Methods for forward error correction coding above a radio link control layer and related apparatus

(54) Title: METHODS FOR CODE OF ANTICIPATED EMISSION ERROR CORRECTION ON A LAYER OF CONTROL OF RADIO LINK AND RELATED EQUIPMENT (30) Unionist Priority: 21/08/2003 us 60 / 497,456; 08/21/2003 US 60 / 497,457; 19/08/2004 US 10 / 922,423 (71) Depositor (s): Qualcomm Incorporated (US) (72) Inventor (s): Francesco Grilli, Alkinoos Hector Vayanos, Lorenzo Casaccia (74) Attorney: Montaury Pimenta, Machado & Lioce (86) International Order: pct US2004 / 027221 de20 / 08/2004 (87) International Publication: W02005 / 022812 of 10/03/2005 (57) Abstract: METHODS FOR EARLY ERROR CORRECTION CODING ON A RADIOENLACE CONTROL LAYER AND RELATED EQUIPMENT. Transmission techniques are provided that improve service continuity and reduce interruptions in content distribution that can be caused by transitions that occur when User Equipment (UE) moves from one cell to another cell, or when content distribution switches from a Point-to-Point (PTP) connection to a Point-to-Multipoint (PTM) connection in the same server cell, and vice versa. Such transmission techniques allow for seamless distribution of content across cell borders and / or between different transmission schemes such as Point-to-Multipoint (PTM) and Point-to-Point (PTP) Mechanisms for adjusting different flows and for retrieving content from each data block during such transitions is also provided in such a way that data is not lost during a transition. In addition, mechanisms are also provided to realign data during decoding at a receiving terminal.

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PtM TRANSMISSION

TRAUSMISSAO PtP

METHODS FOR EARLY ERROR CORRECTION CODING ON A RADIOENLACE CONTROL LAYER AND RELATED EQUIPMENT

FUNDAMENTALS

Field

The present invention relates in general to communication systems and more specifically to the provision of broadcast and multicast content.

Foundations

Wireless communication systems have traditionally been used to carry voice traffic and non-voice traffic with a low data rate. Currently wireless communication systems are being implemented, they also carry multimedia traffic with a high data rate (HDR), such as video, data and other types of traffic. Multicast and Multimedia Broadcast Service Channels (MBMS) can be used to transmit streaming applications based on sources of voice, audio and video data such as radio broadcasts, television broadcasts, films and other types of content. audio or video. Continuous flow of data sources can tolerate delay and a certain amount of loss or bit errors, since these sources are sometimes intermittent and typically compressed. As such, the data rate of transmissions arriving on the Radio Access Network (RAN) can be highly variable. As application stores are typically finite, MBMS transmission mechanisms are required that support variable source data rates.

Base stations typically provide these multimedia traffic services to subscriber stations by transmitting an information signal that can be

2/86 often organized in a plurality of packages. A packet can be a group of bytes, including control and data elements (payload), which are arranged in a specific format. The control elements can comprise, for example, a preamble and a quality metric that can include a cyclic redundancy test (CRC), parity bit (s), and other types of metrics. Packets are usually formatted in a message according to a communication channel structure. The message travels between the source terminal and the destination terminal, and can be affected by characteristics of the communication channel, such as signal / noise ratio, fading, time variance, and other characteristics. These characteristics can affect the modulated signal differently on different communication channels. Among other considerations, the transmission of a modulated information signal through a wireless communication channel requires selection of appropriate methods to protect the information in the modulated signal. Such methods may comprise, for example, encoding, symbol repetition, interleaving and other methods known to those skilled in the art. However, these methods increase overhead. Therefore, a technical adjustment must be made between the reliability of message delivery and the overhead value.

The operator typically selects a Point-to-Point (PTP) connection or a Point-to-multipoint (PTM) connection, on a cell-by-cell basis, depending on the number of interested subscriber stations or User Equipment (UE) receiving MBMS content.

Point-to-Point (PTP) transmission uses dedicated channels to send the service to selected users in the coverage area. A dedicated channel

3/86 information port to / from a single subscriber station. In Point-to-Point (PTP) transmissions a separate channel can be used for transmission to each mobile station. User traffic dedicated to a user's service in the direct link or downlink direction can be sent, for example, through a logical channel called the Dedicated Traffic Channel (DTCH). The services of

<td>Communication</td><td>in</td><td>Point to point</td><td>(PTP) are</td><td colspan="2">typically more</td>

<td>efficient,</td><td>per</td><td colspan="4">example, if there are not enough users</td>

<td>demanding</td><td>one</td><td>Service of</td><td>Multicast</td><td>and Broadcast</td><td>in</td>

<td>Multimedia</td><td colspan="2">(MBMS) in the area of</td><td>roof.</td><td>In such cases,</td><td>The</td>

<td>streaming</td><td>in</td><td>Point to point</td><td>(PTP) can</td><td>be used</td><td>at</td>

<td colspan="2">which season</td><td colspan="2">base transmits the service</td><td>only for</td><td>the</td>

specific users who requested the service. For example, in WCDMA systems it may be more efficient to use a dedicated channel or Point-to-Point (PTP) transmission until there are more than the predetermined number of mobile stations.

Broadcast communication.or Point-to-Multipoint (PTM) communication is communication through a common communication channel for a plurality of mobile stations. A common channel carries information to / from multiple subscriber stations, and can be used simultaneously by multiple terminals. In a Point-to-Multipoint (PTM) communication service, a cellular base station can broadcast multimedia traffic service over a common channel if, for example, the number of users who demand the service exceeds a predetermined limit number included in the base station coverage area. In CDMA 2000 systems, Point-to-Multi-Point (PTM) transmission or transmission is typically used instead of PtP transmission, since the PtM radio carrier is almost as efficient as the PtP radio carrier. At

4/86 transmissions from common channels from a specific base station may not necessarily be synchronized with transmissions from common channels from other base stations. In a typical broadcast system, one or more central stations serve content to one (broadcast network of users). The central station (s) can transmit information to all subscriber stations or to a specific group of subscriber stations. Each subscriber station interested in a broadcast service monitors a common direct link signal. Point-to-Multipoint (PTM) transmissions can be sent on a common broadcast or downlink channel. This common broadcast direct link signal is typically broadcast over a unidirectional channel, such as the Common Traffic Channel (CTCH) that exists in the downlink or direct link direction. Since this channel is unidirectional, the subscriber station does not generally communicate with the base station since allowing all subscriber units to communicate back to the base station could overload the communication system. Thus, in the context of Point-to-Multipoint (PTM) communication services, when there is an error in the information received by the subscriber stations, the subscriber stations may not be able to communicate back to the base station. Consequently, other means of protecting information may be desirable.

In CDMA 2000 systems, the subscriber station can smoothly combine in Point-to-Multipoint (PTM) transmission. Even when measures are taken to protect the information signal, the conditions of the communication channel can degrade in such a way that the destination station cannot decode some of the packets transferred through dedicated channels. In such cases,

5/86 one approach may be simply to retransmit the unencrypted packets using an Automatic Retransmission Request (ARQ) made by the destination station (subscriber) to the originating station (base). Retransmission helps to ensure delivery of the data packet. In case the data cannot be supplied correctly, the RLC user on the transmission side can be notified.

The subscriber station is typically subjected to transitions in various scenarios. These transitions can be classified in different ways. For example, transitions can be classified as cross transitions and direct transitions. Transitions can also be classified as intercellular transitions and intracellular transitions.

Intercellular transitions or transmission schemes can result in service interruptions that may be undesirable for users. Problems can arise when the subscriber station or User Equipment (UE) moves from cell to cell or when the provision of Multicast and Multimedia Broadcast Service (MBMS) content changes from one mode to another in the server cell . The transmissions of neighboring cells can be changed in mutual time by an Átl amount. In addition, additional delay can be introduced during a transition since the mobile station needs to determine system information in the target cell, which requires a certain amount of At2 processing time. Data streams transmitted from different cells (or different types of Point-to-Point (PTP) / Point-to-Multipoint (PTM) transport channel) can be moved between them. Therefore, during point-to-multipoint (PTM) transmissions of cells

6/86 different, the mobile station may receive the same block of content twice or some blocks of content may be lost, which may be undesirable in terms of Quality of Service. Intercellular transitions and / or between Point-to-Point transmission (PTP) and Point-to-Multipoint transmission (PTM) could cause an interruption in service, depending on the duration of the transition and the delay or misalignment between transmissions.

There is, therefore, a need in the transmission technique that provides continuity of service and reduces interruptions in the supply of content that can be

<td>caused</td><td>per</td><td>transitions</td><td>what</td><td>occur when the</td><td>Equipment</td><td>in</td>

<td>User</td><td>(HUH)</td><td>move</td><td>in</td><td>a cell for</td><td>the other,</td><td>or</td>

<td>caused</td><td>per</td><td>transitions</td><td>what</td><td>occur when</td><td colspan="2">the supply</td>

of content changes from a Point-to-Point (PTP) connection to a Point-to-Multipoint (PTM) connection on the same server cell, and vice versa. Such transmission techniques would preferably allow continuous supply of content across cell boundaries and / or between different transmission schemes such as Point-to-Multipoint (PTM) and Point-to-Point (PTP). Mechanisms for adjusting different flows and for retrieving content from each block of data during these transitions are also desirable so that data is not lost during a transition.

It would also be desirable to provide mechanisms for realigning data during decoding at a receiving terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of a communication system.

Figure 2 is a block diagram of the UMTS signaling protocol stack.

Figure 3 is a block diagram of a packet switched user plan from the UMTS protocol stack.

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Figure 4 is a block diagram of a part of the access layer of the UMTS signaling protocol stack.

Figure 5A is a block diagram of data transfer modes used in the Radio Link Control (RLC) layer of the UMTS signaling protocol stack, and several channels used in each layer.

Figure 5B is a block diagram showing the architecture of the Radioenlace control layer (RLC) including several RLC data transfer modes.

Figure 5C is a block diagram showing an entity to implement the Confirmed Mode (AM) of Radio Link Control (RLC).

Figure 6 is a diagram of a modified UMTS protocol stack having an early error correction layer.

Figure 7A shows an embodiment of a protocol structure of the access layer which includes an error correction (FEC) layer.

Figure 7B shows another modality of an access layer protocol structure that includes an early error correction (FEC) layer.

Figure 8 is a diagram of an information block and external code block that corresponds to the information block.

Figure 9A is a diagram showing an external code block structure that can be applied to Multicast and Multimedia Broadcast Service (MBMS) data.

Figure 9B is a diagram showing the external code block structure of Figure 9A in which multiple lines are sent per Transmission Time Interval (TTI).

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Figure 9C is a diagram showing the outer block structure of Figure 9A in which each line is sent in multiple TTIs.

Figures 10A and 10B are diagrams showing the external code blocks, generated by the Early error correction layer.

Figure 11 is a modality of an Early Error Correction (FEC) layer used in an entity

UM + RLC.

Figure 12A shows an encoding process for creating an external code block of data units in which line sizes of the external code block are fixed.

Figure 12B shows an example of information transmitted over the air in figure 12A.

Figure 13 shows a coding process for creating an external code block having a variable line size.

Figure 14 is a diagram of an embodiment of an Early Error Correction (FEC) header format.

Figure 15 is an algorithm to allow mobile stations to delay decoding by the decentralization of time between different logical flows.

Figure 16 is a diagram showing a temporal relationship between external code blocks received by a mobile station as the mobile station transitions between the receipt of a Cell A Point-to-Multipoint (PTM) transmission and another Point30 transmission a-Multipoint (PTM) of cell B.

Figure 17 is a diagram showing a temporal relationship between blocks of external code received by a mobile station as a transition occurs between a

9/86 Point-to-Multipoint transmission (PTM) and Point-to-Point transmission (PTP).

Figure 18 is a diagram showing a temporal relationship between external code blocks received by a mobile station during a transition or relocation between a Radio Network Controller (RNC) A Point-to-Point (PTP) transmission and another transmission Point-to-Point (PTP) of the Radio Network Controller (RNC) B.

DETAILED DESCRIPTION

The word exemplary is used here to mean serving as an example, instance or illustration. Any modality described here as an example should not necessarily be interpreted as preferred or advantageous in relation to other modalities.

The term mobile station is used here interchangeably with the terms destination station, subscriber station, subscriber unit, terminal and User Equipment (UE), and is used here to refer to hardware, such as a base station, with which an access network, such as the UMTS Terrestrial Radio Access Network (UTRAN), communicates. In UMTS systems, the User Equipment (UE) is a device that allows a user to access UMTS network services and also preferably includes a USIM that contains all the user's subscription information. A mobile station can be mobile or stationary, and can generally include any communicator, data devices or terminal that communicates through a wireless channel or through a wire channel, for example, using coaxial or fiber optic cables . Mobile stations can be incorporated into devices that include, but are not limited to, a PC card, compact flash, external or internal modem, or cordless or corded telephone.

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The term connection establishment state refers to the state in which a mobile station is in the process of establishing an active traffic channel connection with a base station.

The term traffic state refers to the state in which a mobile station has established an active traffic channel connection with a base station.

The term communication channel is used here to mean a physical channel or a logical channel according to the context.

The term physical channel is used here to refer to a channel that carries control information or user data through the air interface. Physical channels are the means of transmission that provide the radio platform through which information is actually transferred, and serve to carry signaling and user data through the radio link. A physical channel typically comprises a combination of frequency mix code and channel code. In the uplink direction, relative phase can also be included. Several different physical channels can be used in the uplink direction based on what the mobile station is trying to do. In a UMTS system, the term physical channel can also refer to the different types of bandwidth allocated to different purposes through a Uu interface. The physical channels form the physical existence of the Uu interface between the User Equipment (UE) domain and the network access domain. Physical channels can be defined by physical mappings and attributes used to transfer data over the air interface.

The term transport channel is used here to refer to a communication route for transport

11/86 data between physical layer entities even. Transport channels refer to the way in which information is transmitted. There can generally be two types of transport channels known as Common Transport Channels and Dedicated Transport Channels. A transport channel can be defined according to how and with what characteristics the data can be transferred through the aerial interface in the physical layer, for example, using dedicated or common physical channels, or multiplexing of logical channels. Transport channels can serve as service access points (SAPs) for the physical layer. In a UMTS system, the transport channel describes how logical channels can be transferred and maps these information streams to physical channels. Transport channels can be used to transport user data and signaling between the Middle Layer Access (MAC) and Physical Layer (Ll) control layer. The Radio Network Controller (RNC) sees the transport channels. Information passes to the physical layer of the MAC layer through any of several transport channels that can be mapped to physical channels.

The term logical channel is used here to refer to an information flow, dedicated to the transfer of a specific type of information or radio interface. Logical channels refer to the information being transmitted. A logical channel can be defined by what type of information is transferred, for example, signaling or user data, and can be understood as different tasks that the network and terminal must perform at different times. Logical channels can be mapped to transport channels that perform effective information transfer between the mobile station domain and the access domain. Information passes through channels

12/86 logic that can be mapped through transport channels that can be mapped to physical channels.

The term dedicated channel is used here to refer to a channel that is typically dedicated to, or reserved for, a specific user, and that carries information to or from a specific mobile station, subscriber unit or user equipment. A dedicated channel typically carries information intended for a particular user, including data for the actual service as well as higher layer control information. A dedicated channel can be identified by a certain code at a certain frequency. A dedicated channel can be bidirectional to potentially allow for feedback.

The term common channel is used here to refer to a transport channel that carries information to / from multiple mobile stations. In a common channel, information can be shared between all mobile stations. A common channel can be divided between all users or a group of users in a cell.

The term Point-to-Point Communication (PTP) is used here to mean communication transmitted through a physical communication channel, dedicated to a single mobile station.

The terms broadcast communication '· Point-to-Multipoint (PTM) communication can be used here to refer to communication through a common communication channel for a plurality of mobile stations.

The term reverse link or used here to refer to the communication through which the mobile station sends signals to a base station on the Radio Access network. That channel can also be used to transmit signals from one link or be a link / channel uplink channel and

in

13/86 mobile station to a mobile base station or from a mobile base station to a base station.

The term direct link or downlink channel is used here to mean a link / communication channel through which an access radio network sends signals to a mobile station.

The term Transmission Timing Interval (TTI) is used here to refer to how often data arrives from higher layers in the physical layer. A Transmission Timing Interval (TTI) can refer to the time between the arrival of a Transport Block Set (TBS), and is approximately equal to the periodicity at which a TBS is transferred by the physical layer at the radio interface. The data sent on a Transport Channel during a TTI can be encoded and merged together. A TTI can cover multiple radio frames, and can be a multiple of the minimum interleaving period. The starting positions of the TTI for different transport channels that can be multiplexed together for a single connection are aligned in time. TTIs have a common starting point. 0 Media Access Control provides a Set of Transport Blocks for the physical layer in each TTI. Different transport channels, mapped on the same physical channel, can have different Transmission Timing Interval (TTI) durations. Multiple PDUs can be sent in a TTI.

The term packet is used here to mean a group of bits, including data or payload and control elements arranged in a specific format. The control elements can comprise, for example, a preamble, a quality metric, and others, known to those skilled in the art. The quality metric comprises, for example, a cyclic redundancy test

14/86 (CRC), a parity bit, and others known to those skilled in the art.

The term access network is used here to mean equipment needed to access the network. The access network can comprise a group or network of base stations (BS) and one or more base station controllers (BSC). The access network carries data packets between multiple subscriber stations. The access network can be additionally connected to additional networks outside the access network, such as a legal intranet or the Internet, and can carry data packets between access terminals and such external networks. In the UMTS system, the access network can be referred to as the UMTS Terrestrial Radio Access Network (UTRAN).

The term central network is used here to refer to the switching and routing capacity for connection to the Public Switched Telephone Network (PSTN), for circuit switched calls in the circuit switched domain (CS), or Packet Data Network (PSDN) for packet-switched calls in the packet-switched (PS) domain. The term core network also refers to the routing capability for mobility and subscriber location management and for authentication services. The core network includes network elements necessary for switching and subscriber control.

The term base station is used here to refer to a home station that includes the hardware with which the mobile station communicates. In the UMTS system, the term node B can be used interchangeably with the term base station. A base station can be fixed or mobile.

The term cell is used here to refer to hardware or a geographical coverage area depending on

15/86 of the context in which the term is used.

The term Service Data Unit (SDU) is used here to refer to a data unit exchanged with the protocol provided above the protocol of interest.

The term Payload Data Unit (PDU) is used here to refer to a data unit exchanged with the protocol provided below the protocol of interest. If the identity of the protocol of interest is ambiguous, then a specific mention will be made in the name. For example, FEC-PDUs are the PDUs of the FEC layer.

The term soft handoff is used here to mean communication between a subscriber station and two or more sectors, where each sector belongs to a different cell. The reverse link communication can be received by the two sectors, and the direct link communication can be simultaneously carried on the direct links of the two or more sectors.

The term softer handoff is used here to mean communication between a subscriber station and two or more sectors, where each sector belongs to the same cell. Reverse link communication can be received by both sectors, and direct link communication can be simultaneously carried on direct links from one of the two or more sectors.

The term erasure is used here to mean failure to recognize a message and can also be used to refer to a set of bits that may be missing at the time of decoding.

The term cross transition can be defined as a transition from Point-to-Point (PTP) transmission to Point-to-Multipoint (PTM) transmission, or vice versa. The four possible cross transitions are

16/86 Point-to-Point (PTP) transmission in cell A for Point-to-Multipoint (PTM) transmission in cell B, Point-to-Multipoint (PTM) transmission in cell A for Point-to-Multipoint transmission a-Point (PTP) in cell B, from Point-to-Point (PTP) transmission in cell A to Point-to-Multipoint (PTM) transmission in cell A, and from Point-to-Multipoint transmission (PTM ) in cell A for Point-to-Point (PTP) transmission in cell A.

The term direct transition can be defined as transitions from a point-to-point transmission to another point-to-point transmission and transitions from point-to-multipoint transmission to point-to-multipoint transmission. The two possible direct transitions are Point-to-Point (PTP) in cell A for Point-to-Point (PTP) transmission in cell B, and Point-to-Multipoint (PTM) transmission in cell A for transmission Point-to-Multipoint (PTM) in cell B.

intercellular transition is used to refer to a transition across cell boundaries. The four possible intercellular transitions are from Point-to-Point (PTP) transmissions in cell A to Point-to-Point (PTP) transmission in cell B, from Point-to-Multipoint transmission (PTM) in cell A to Point-to-Multipoint transmission (PTM) in cell B, Point-to-Point transmission (PTP) in cell A for Point-to-Multipoint transmission (PTM) in cell B, and Point-a transmission -Multipoint (PTM) in cell A for Point-to-Point transmission (PTP) in cell B. Generally, the most frequent transition is Point-to-Multipoint (PTM) transmission to Point-to-Multipoint (PTM) transmission across cell boundaries.

The term intracellular transition is used to refer to transitions within a cell in a way

17/86 to another mode. The two possible intracellular transitions are from Point-to-Point (PTP) transmission in cell A to Point-to-Multipoint (PTM) transmission in cell A, and Point-to-Multipoint transmission (PTM) in cell A for Point-to-Point (PTP) transmission in cell A.

The term radio carrier is used to refer to a service provided by Layer 2 for the transfer of user data between User Equipment (UE) and the UMTS Terrestrial Access Radio Network (UTRAN).

The modalities of the invention will now be discussed in which the aspects discussed above are implemented in a UMTS or WCDMA communication system. Figures 1-5C explain some aspects of a conventional WCDMA or UMTS system in which aspects of the inventions described here that could be applied in this description are provided for purposes of illustration and limitation only. It should be recognized that aspects of the invention may also be applicable to other systems that contain both voice and data such as GSM systems and CDMA 2000 systems that are in compliance with the 3^The generation embedded in a set of documents including Document no. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), or TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems (the IS-2000 standard), and GSM specifications such as TS 04.08 (the layer 3 specification of the mobile radio interface), TS 05.08 (Radio Subsystem Link Control) and TS 05.01 (Physical Layer in the Radio Path (General Description)).

For example, although the description specifies that the Radio Access 20 network can be implemented using the Universal Land Access Radio Network aerial interface

18/86 (UTRAN), alternatively, in a GSM / GPRS system, access network 20 could be a Radio Network with GSM / EDGE access (GERAN), or in a case between systems it could comprise cells of an UTRAN overhead interface and cells from a GSM / EDGE aerial interface.

UMTS network topology

Figure 1 is a block diagram of a communication system according to the UMTS network topology. A UMTS system includes User Equipment (UE) 10, an access network 20, and a central network 30. The UE 10 is coupled to the access network which is coupled to the central network 30 which can be coupled to an external network.

The UE 10 includes mobile equipment 12 and a Universal Subscriber Identity Module (USIM) 14 that contains a user's subscription information. The Cu interface (not shown) is the electrical interface between the USIM 14 and the mobile equipment 12. The UE 10 is generally a device that allows a user to access the services of the UMTS network. The UE 10 can be a mobile such as a cell phone, a fixed station, or another data terminal. The mobile equipment can be, for example, a radio terminal used for radio communication through an air interface (Uu). The Uu interface is the interface through which the UE accesses the fixed part of the system. USIM is generally an application that resides on a smart card or another logic card that includes a microprocessor. The smart card contains the subscriber's identity, runs authentication algorithms, and stores authentication in encryption keys and required signature information on the terminal.

Access network 20 includes radio equipment to access the network. In a WCDMA system, access network 20 is the aerial interface of the Terrestrial Access Radio Network

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Universal (UTRAN). The UTRAN includes at least one radio Network Subsystem (RNS) which includes at least one base station or node B 22 coupled to at least one radio Network Controller (RNC) 24.

The RNC controls the radio resources of the UTRAN. The

RNCs 24 of the access network 20 communicate with the central network 30 through the interface Iu. The Uu interface, the Iu 25 interface, the Iub interface, and the Iur interface allow connection between networks between equipment from different vendors and are specified in 3GPP standards. The implementation of the Radio Network Controller (RNC) varies from vendor to vendor and will therefore be described in general terms below.

The Radio Network Controller (RNC) 24 serves as the switching and control element of the UMTS Terrestrial Access Radio Network (UTRAN), and is located between the Iub interface and the Iu 25 interface. The RNC acts as an access point for service for all services that UTRAN provides for the central network 30, for example, connection management for user equipment. The Iub 23 interface connects a B 22 node and a Radio Network Controller (RNC) 24. The Iu interface connects the UTRAN to the central network. 0 Radio Network Controller (RNC) provides a switching point between carrier Iu and base stations. User Equipment (UE) 10 can have multiple radio bearers between itself and the Radio Network Controller (RNC) 24. The radio bearer is related to the User Equipment (UE) context which is a set of required definitions through the Iub to arrange common connections and dedicated connections between the User Equipment (UE) and the Radio Network Controller (RNC). The respective RNCs 24 can communicate with each other via an optional Iur interface that allows soft handover between cells connected to nodes

Different 20/86 22. The Iur interface thus allows inter-RNC connections. In such cases, a server RNC maintains the Iu 25 connection to the central network 30 and performs external control and selector power control functions, while a float RNC transfers frames that can be exchanged through the Iur interface to the mobile station 10 through one or more base stations 22.

The RNC that controls a node B 22 can be referred to as the RNC that controls node B, and it controls the load and congestion of its own cells, and also performs admission control and code allocations for new radio links to be established in those cells.

RNCs and base stations (or Bs node) can be connected and communicate via the Iub 23 interface. RNCs control the use of radio resources by each base station 22 coupled to a specific RNC 24. Each base station 22 controls one or more cells and provides a radio link for mobile station 10. The base station can perform interface processing such as channel coding and interleaving, rate adaptation and spreading. The base station also performs basic radio resource management operations such as power control between loops. Base station 22 converts the data stream between the Iub and Uu 23, 26 interfaces. Base station 22 also participates in radio resource management. An air interface Uu 26 couples each base station 22 to the mobile station 10. Base stations can be responsible for radio transmission in one or more cells to the mobile station 10, and for radio reception in one or more cells of the mobile station 10.

Central network 30 includes all switching and routing capabilities to (1) connect to PSTN 42 if a circuit switched call is present or to a

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Packet Data Network (PDN) if a packet switched call is present, (2) subscriber location and mobility management and (3) authentication services. The central network 30 may include a home location register (HLR) 32, a visitor location record / mobile switching service center (MSC / VLR) 34, a mobile gateway switching center (GMSC) 36, a node for support of general packet radio service server (SGSN) 38 and a node for support of gateway GPRS (GGSN) 40.

The central network 30 can be coupled to an external circuit switching network (CS) 42 that provides circuit switching connections, such as the Public Switched Telephone Network (PSTN) or (ISDN), if a packet switching call is present, or can be coupled to a PS 44 network, such as the Internet, which provides connections for packet data services if a packet switching call is present.

UMTS Signaling Protocol Stack

Figure 2 is a block diagram of the UMTS 110 signaling protocol stack. The UMTS 110 signaling protocol stack includes an access layer and a non-access layer (NAS).

The access layer typically includes a physical layer 120, layer 2 130 that includes a physical media access control layer (MAC) 140 and a radio link control layer (RLC) 150, and a radio resource control layer (RRC) 160. The different layers of the access layer will be described in more detail below.

The UMTS non-access layer is essentially the same as the upper layers of GSM and can be divided into a circuit switching part 170 and a packet switching part 180. The switching part

22/86 of circuit 170 includes a connection management layer (CM) 172 and a mobility management layer (MM) 178. The CM layer 172 handles circuit switching calls and includes several sublayers. The call control (CC) sublayer 174 performs functions such as establish and release. The sub-layer of supplementary services (SS) 176 performs functions such as issuing calls and three-way calling. A sub-layer of short message services (SMS) 177 runs short message services. The MM layer 178 takes care of updating location and authentication for circuit switching calls. The packet switched portion 180 includes a session management (SM) sublayer 182 and a GPRS mobility management (GMM) sublayer 184. The session management (SM) sublayer 182 takes care of packet switching calls by performing functions such as establishing and releasing, and also includes a short message services (SMS) section 183. The GMM 184 sublayer takes care of location updating and authentication for packet switched calls.

Figure 3 is a block diagram of a packet switching user plan from the UMTS protocol stack. The stack includes an access layer (AS) layer and a non-access layer (NAS) layer. The NAS layer includes application layer 80 and Packet Data Protocol (PDP) layer 90. Application layer 80 is provided between User Equipment (UE) 10 and remote user 42. PDP layer 90, as IP or PPP, it is provided between GGSN 40 and User Equipment (EU) 10. Lower layer packet protocols (LLPP) 39 are provided between remote user 42 and SGSN 38. Iu 25 interface protocols are provided between radio Network Controller (RNC) 24 and SGSN 38, and Iub interface protocols are

23/86 provided between the Radio Network Controller (RNC) 24 and node B 22. Other portions of the AS layer will be described below.

Access Stratum Layer (AS)

Figure 4 is a block diagram of the access layer portion of the UMTS signaling protocol stack. The conventional access layer includes the physical layer (Ll) 120, the data link layer (L2) 130 having sublayers including Media Access control layer (MAC) 140, Radio link control layer (RLC) 150, layer of Packet Data Convergence Protocol (PDCP) 156, Broadcast / Multicast Control layer (BMC) 158, and a Radio Resources control layer (RRC). These layers will be further described below.

Radio carriers contain user data 163 between application layers and layer two (L2) 130. Control plane signaling 161 can be used for all UMTS-specific control signaling, and includes the application protocol on the signaling carrier for carry the application protocol messages. The application protocol can be used to configure carriers for the UE 10. The user plan carries all user plan information 163 sent and received by the user as an encoded voice in a voice call or the packets over an Internet connection. User plan information 163 bears the data stream and data bearers to those data streams. Each data stream can be characterized by one or more frame protocols specified for that interface.

The Radio Resource Control (RRC) layer 160 functions as the general controller of the access layer, and configures all other layers in the access layer.

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The RRC layer 160 generates control plane signaling 161 that controls the Radio Link Control Units 152, the physical layer (Ll) 120, the Medium Access Control (MAC) layer 140, the Radio Link Control layer ( RLC) 150, the Packet Data Convergence Protocol (PDCP) layer 156, and the Broadcast / Multicast Control (BMC) layer 158. The Radio Resource Control (RRC) layer 160 determines the types of measurements to do, and reports those measurements. The RRC 160 layer also serves as the signaling and control interface for the non-access layer.

More specifically, the RRC 160 layer broadcasts system information messages that include both access layer and non-access layer information elements to all User Equipment (UE) 10. The RRC 160 layer establishes, maintains and releases a Radio Resource Control (RRC) connection between UTRAN 20 and UE 10. 0 UE RRC requests the connection, while UTRAN RRC configures and releases the connection. The RRC 160 layer also establishes, reconfigures, and releases Radio Carriers between UTRAN 20 and UE 10, with UTRAN 20 initiating these operations.

The RRC 160 layer also takes care of various aspects of the mobility of the User Equipment (UE) 10. These procedures depend on the EU State, whether the call is a circuit switched or packet switched call, and Radio Technology Access (RAT) of the new cell. The RRC layer 160 also pages the UE 10. The UTRAN RRC pages the UE regardless of whether the UE is listening to the paging channel or the paging indicator channel. The EU RRC notifies the upper layers of the central network (CN) 30.

The data link layer (L2) 130 includes a Medium Access control (MAC) sub-layer 40, a

25/86 Radioenlace control (RLC) 150 sublayer, a Packet Data Convergence Protocol (PDCP) sublayer 156, and a Broadcast / Multicast Control (BMC) sublayer 158.

The broadcast and multicast control protocol (BMC) 158 carries, through the radio interface, the messages that originate in the cell broadcast center by adapting the broadcast / multicast service originating from the broadcast domain on the radio interface. The BMC 158 protocol offers a service called a radio carrier, and exists on the user plane. The BMC 158 and RNC protocol store cell broadcast messages received through the CBC-RNC interface for scheduled transmission. On the UTRAN side, BMC 158 calculates the required transmission rate for the cell broadcast service based on messages that can be received through the CBC-RNC interface (not shown) and requests appropriate CTCH / FACH resources from the RRC. The BMC 158 protocol also receives programming information along with each cell broadcast message through the CBCRNC interface. Based on this programming information, from the UTRAN side, the BMC generates programmed messages and programmed BMC message sequences accordingly. On the user equipment side, the BMC evaluates the program messages and indicates the programming parameters for the RRC that can then be used by the RRC to configure the lower layers for discontinuous reception. The BMC also transmits BMC messages, such as programming and cell broadcast messages according to a program. Uncorrupted cell broadcast messages can be delivered to the upper layer. Part of the control signaling between the UE 10 and the UTRAN 20 can be Radio Resource Control (RRC) 160 messages that carry all parameters

26/86 required to configure, modify and release the layer 2 130 and layer 1 120 protocol entities. RRC messages contain in their payload all higher layer signaling. Radio Resource Control (RRC) controls the mobility of user equipment in connected mode by signaling such as measurements, handovers and cell updates.

The Packet Data Convergence Protocol (PDCP) 156 exists in the user plan for services in the PS domain. The services offered by the PDCP can be called radio carriers. The Protocol of

Packet Data Convergence (PDCP) provides header compression services. The Packet Data Convergence Protocol (PDCP) 156 contains compression methods that can provide better spectral efficiency for services transmitting IP packets via radio. Any of several header compression algorithms can be used. The PDCP compresses redundant protocol information at the transmitting entity and decompresses at the receiving entity. The header compression method can be specific to the specific network layer, transport layer, or upper layer protocol combinations, for example, TCP / IP and RTP / UDP / IP. The PDCP also transfers user data it receives in the form of a PDCP Service Data Unit (SDU) from the non-access layer and issues it to the RLC entity, and vice versa. PDCP also provides support for relocating SRNS without loss. When the PDCP uses a Confirmed Mode (AM) RL C with sequential delivery, PDCP entities that can be configured to support loss RSRNS relocation have a Protocol Data Unit (PDU) sequence number, which together with packets Unconfirmed PDCPs can be issued to the new SRNC during relocation.

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The RLC 150 layer offers services to higher layers (for example, the non-access layer) through service access points (SAPs) that can be used by higher layer protocols on the EU side and by the IURNAP protocol on the side of UTRAN. Service access points (SAPs) describe how the RLC layer takes care of data packets. All higher-level signaling, such as mobility management, call control, session management, etc., can be encapsulated in RLC messages for transmission from the radio interface. The RLC layer 150 includes several Radio Link Control Entities 152 coupled to the MAC layer 140 through logical channels that contain signaling information and user data.

In control plane 161, RLC services can be used by the RLC layer to transport signaling. In the 163 user plan, RLC services can be used by the PDCP or BMC specific service protocol layers or by other higher layer user plan functions. The RLC services can be called signaling radio bearers in control plane 161 and radio bearers in user plane 163 for services that do not use PDCP 156 or user plan protocols. In other words, the RLC layer 150 provides services in the control plane 161 called radio signaling carriers (SRBs), and in the user plan 163 provides services called radio carriers (RBs) if the BMC and PDCP protocols cannot. be used for that service. Otherwise, the RB service may be provided by the PDCP layer 156 or BMC layer 158.

The Radio Link Control (RLC) layer 150

28/86 performs structuring functions for control and user data, which include segmentation / concatenation and filling functionality. The RLC layer 150 typically provides segmentation and retransmission services for the Radio Resource Control (RRC) layer 160 for control data in the control plane 161 and for the application layer for user data in the user plane 163. The RLC layer typically performs segmentation / reassembly of higher layer Protocol Data Units (PDUs) with variable length to / from smaller RLC Protocol Data Units (PDUs). A Radio Link Control Protocol (PDU) Data Unit (RLC) typically contains a PDU. The Radio Link Control (RLC) PDU size can be set, for example, according to the lowest possible bit rate for the service using Radio Link Control (RLC). As will be discussed below, for variable rate services, multiple Radio Link Control (RLC) PDUs can be transmitted during a transmission time interval (TTI) when any bit rate higher than the lowest is used. The RLC transmission entity also performs concatenation. If the contents of a Radio Link Control (RLC) Service Data Unit (SDU) do not fill an entire number of Radio Link Control (RLC) PDUs, the first segment of the next Radio Link Control (RLC) SDU can be placed on the Radio Link Control PDU (RLC) in concatenation with the last segment of the previous RLC SDU. The RLC transmission entity also typically performs a fill function. When the remaining data to be transmitted does not fill an entire Radio Link Control (RLC) PDU of a given size, the rest of that data field can be filled with fill bits. According

29/86 aspects of the invention discussed below with reference to figures 11-13, for example, techniques can be provided to reduce or eliminate the amount of filler that is used.

The RLC receiving entity detects duplicates of received Radio Link Control (RLC) PDUs and ensures that the result on the top layer PDU is provided once to the top layer. The RLC layer also controls the rate at which the PRLC transmitting entity can send information to an RLC receiving entity.

access layer, will recognize that all

Figure 5A is a block diagram illustrating the data transfer modes used in the Radio Link Control (RLC) layer of the UMTS signaling protocol stack, and showing possible mappings of logical, transport and physical UMTS channels. with respect Those skilled in the art, mappings would not necessarily be defined at the same time for a given User Equipment (UE), and multiple instantiations of some mappings can occur simultaneously. For example, a voice call could use three Dedicated Traffic Channel (DTCH) logical channels mapped to three Dedicated Channel (DCH) transport channels. In addition, some channels shown in figure 5, such as CPICH, SCH, DPCCH, AICH, and PICH, exist in the context of the physical layer, and do not carry upper layer signaling or user data. The content of these channels can be defined in physical layer 120 (Ll).

Each RLC instance in the Radio Link Control (RLC) layer can be configured by the Radio Resource Control (RRC) 160 layer to operate in one of three modes: transparent mode (TM), unconfirmed mode

30/86 (UM) or confirmed mode (AM), which are described in detail below with reference to figure 5B. The three data transfer modes indicate the mode in which Radio Link Control (RLC) is configured for a logical channel. RLC entities in a transparent and unconfirmed way are defined to be unidirectional whereas entities in a confirmed way are bidirectional. Normally, for all RLC modes, CRC error detection is performed at the physical layer and the result of the CRC test is provided to the RLC along with the actual data. Depending on the specific requirements of each mode, these modes perform some or all of the functions of the RLC 150 layer, which include segmentation, reassembly, concatenation, filling, retransmission control, current control, duplicate detection, supply in sequence, correction of error and encryption. These functions are described in more detail below with reference to figures 5B and 5C. In accordance with an aspect of the invention discussed here, a new way of transferring Radio Link Control (RLC) data can be provided.

The MAC layer 140 offers services to the RLC layer 150 through logical channels that are characterized by the type of data transmitted. The Media Access Control (MAC) layer 140 maps and multiplexes logical channels to transport channels. The MAC layer 140 identifies the User Equipment (UE) that is in common channels. The MAC layer 140 also multiplexes / demultiplexes higher layer PDUs to / from transport blocks supplied to / from the physical layer on common transport channels. The MAC takes care of service multiplexing for common transport channels since it cannot be done at the physical layer. When a common transport channel carries data of logical channels of the type

Dedicated 31/86, the Media Access Control (MAC) header includes an UE identification. The MAC layer also multiplexes and demultiplexes higher layer PDUs to / from sets of transport blocks supplied to or from the physical layer on dedicated transport channels.

The MAC layer 140 receives RLC PDUs along with condition information about the amount of data in the RLC transmission store. The MAC 140 layer compares the amount of data corresponding to the transport channel with limits defined by the RRC 160 layer. If the data amount is too high or too low, then the MAC sends a measurement report on the volume situation. traffic to the RRC. The RRC 160 layer can also request that the MAC 160 layer send these measurements periodically. The RRC 160 layer uses these reports to activate the reconfiguration of radio carriers and / or transport channels.

<td>THE</td><td>layer of</td><td>MAC</td>

<td>transport</td><td>appropriate</td><td>(TF)</td>

<td>depending on</td><td>of fees</td><td>in</td>

<td>logical.</td><td>The layer</td><td>in</td>

priority of data streams by selecting high bit rate and low bit rate transport formats (TFs) for different data streams. Packet switching (PS) data is inherently bursty, so the amount of data available for sending varies from frame to frame. When more data is available, the MAC 140 layer can choose one of the highest data rates, however, when both signaling and user data is available, the MAC 140 layer chooses between them to maximize the amount of data sent. of the most priority channel

High 32/86. The transport format (TF) can be selected with respect to transport format combinations (TFCs) that can be defined by admission control for each connection.

The Media Access Control (MAC) layer also performs encryption. Each radio carrier can be encrypted separately. The encryption details are described in 3GPP TS 33.102.

In a system like WCDMA there are three types of transport channels that can be used to transmit packet data. These channels are known as a common transport channel, a dedicated transport channel, and a shared transport channel. In the downlink, the transport channel packet data is selected by a packet scheduling algorithm. In the uplink, the transport channel is selected by the mobile unit 10 based on the parameters defined by the package programming algorithm.

Common channels can be, for example, the RACH random access channel on the uplink and the advanced FACH access channel on the downlink. Both carry signaling data and user data. Common channels have a low setup time. As the common channels can be used for signaling before configuring the connections, the common channels can be used to send packets immediately without any long configuration time. There are typically some RACH or FACH per sector. Common channels do not have a feedback channel and therefore typically use open loop or fixed power control. In addition, common channels do not use soft handover. In this way, the link level performance of common channels can be worse than that of dedicated channels and more interference can be generated than

33/86 than with dedicated channels. Consequently, common channels may be more suitable for transmitting small individual packets. Applications to be used on common channels would be applications such as short message services, and short text emails. Sending a single request to a page on the Network could also adapt well to the concept of common channels, however in the case of larger amounts of data, common channels suffer from poor radio performance.

Dedicated channels can use soft handover and fast power control features that improve the radio's performance and typically less interference is generated than with regular channels. However, setting up a dedicated channel takes more time than accessing common channels. Dedicated channels can have variable bit rates from a few kilobytes per second up to 2 megabytes per second. As the bit rate changes during transmission, the orthogonal downlink code must be allocated according to the highest bit rate. Therefore, dedicated variable bit rate channels consume valuable downlink orthogonal code space.

The physical layer (Ll) 120 is coupled to the MAC layer 140 through transport channels that contain signaling information and user data. The physical layer 120 provides services to the MAC layer through transport channels that can be characterized by how and with what characteristics the data is transferred.

The physical layer (Ll) 120 receives signaling and user data through the radio link via physical channels. The physical layer (Ll) typically performs multiplexing and channel coding including CRC calculation, early error correction (FEC), rate equivalence, interleaving of transport channel data, and

34/86 multiplexing of transport channel data, as well as other physical layer procedures such as acquisition, access, page, and radio link establishment / failure. The physical layer (Ll) can also be responsible for spreading and shuffling, modulation, measurements, diversity of transmission, power weighting, handover, compressed mode and power control.

Figure 5B is a block diagram showing the architecture of the Radio Link Control (RLC) layer. As mentioned above, each RLC entity or instance 152 in the Radio Link Control (RLC) layer 150 can be configured by the Radio Resource Control (RRC) layer 160 to operate in one of three data transfer modes: transparent (TM), unconfirmed mode (UM) or confirmed mode (AM). The mode of transferring data to user data can be controlled using a Quality of Service (QoS) scenario.

The TM is unidirectional and includes a transmitting TM entity 152A and a receiving TM entity 152B. In transparent mode, no protocol order is added to the higher layer data. Erroneous protocol data units (PDUs) can be discarded or marked as erroneous. Streaming type transmission can be used in which higher layer data is not typically segmented, although in special cases, transmissions of limited reassembly / segmentation can be performed. When segmentation / reassembly is used, it can be negotiated in the radio carrier configuration procedure.

The UM is also unidirectional and includes a transmitting UM entity 152C and a receiving UM entity 152D. A UM RLC entity is defined as unidirectional, because no association is required

35/86 between uplink and downlink. The provision of data is not guaranteed in UM. UM can be used, for example, for certain RRC signaling procedures where confirmation and retransmissions are not part of the RRC procedure. Examples of user services that use RLC in an unconfirmed way are the cell and voice broadcast service over IP. Erroneous data received can be marked or discarded depending on the configuration. A timer-based disposal without an explicit signaling function can be applied, so RLC PDUs that cannot be transmitted in a specified time can simply be removed from the transmission store. In unconfirmed data transfer mode, PDU structuring includes sequence numbers, and a sequence number check can be performed. Checking sequence numbers helps to ensure the integrity of reassembled PDUs and provides a means of detecting corrupted Radio Link Control (RLC) SDUs by checking the sequence number on Radio Link Control (RLC) PUDs when mounted on an SDU Radio Link Control (RLC). Any corrupted Radio Link Control (RLC) SDUs can be discarded. Segmentation and concatenation can also be provided in Unverified Mode (UM).

In confirmed mode, the AM RLC entity is bidirectional and capable of confirming an indication of the link condition in the opposite direction in the user data. Figure 5C is a block diagram showing an entity to implement the Radioenlace Control Confirmed Mode (AM) entity (RLC) and how an AM PDU can be built. Data packets (RLC SDUs) received from higher layers through AM-SAP can be segmented and / or concatenated 514 to Protocol Data Units (PDU)

36/86 of a fixed length. The length of the Protocol Data Unit is a semi-static value decided in the radio carrier configuration, and can be changed through the RRC radio carrier reconfiguration procedure. For concatenation or filling purposes, bits carrying length and extension information can be inserted at the beginning of the last Protocol Data Unit or data from an SDU can be included. If multiple SDUs fit into a PDU, they can be concatenated into the appropriate length (Lis) indicators, they can be inserted at the beginning of the PDU. The PDUs can then be placed in the transmission store 520, which can also take care of relay management.

The PDU can be built by taking a PDU from the transmission store 520, adding a header to it, and if the data in the PDU does not fill the entire RLC PDU, a fill field or confirmation condition message can be attached. The confirmation condition message can originate from the receiving side or the transmitting side to indicate a RLCSDU disposal. The header contains the RLC PDU sequence number (SN), a polling bit (P), which can be used to request condition of the even entity, and optionally a length indicator (LI) which can be used if concatenation of SDUs, fill, or a confirmation PDU occur on the RLC PDU.

Confirmed Mode (AM) is typically used for package-type services, such as browsing the Internet and downloading e-mail. In confirmed mode, an automatic retry request mechanism (ARQ) can be used for error correction. Any packets received with errors can be retransmitted. Quality versus delay performance of RLC can be controlled

37/86 by RRC through the configuration of several retransmissions provided by RLC. If the RLC cannot deliver the data correctly, for example, if the maximum retransmission number has been reached or the transmission time has been exceeded, then the upper layer is notified and the Radio Link Control SDU (RLC) can be discarded . The peer entity can also be informed of the SDU discard operation by sending a move receipt window command in a condition message so that the receiver also removes all PDUs that belong to the discarded Radio Link Control (RLC) SDU.

RLC can be configured for both in-sequence and out-of-sequence delivery. With sequential delivery, the order of the highest layer of PDUs can be maintained, while out-of-sequence delivery issues higher layer PDUs as soon as they are fully received. The RLC layer provides sequential delivery of higher layer PDUs. This function preserves the order of higher layer PDUs that have been submitted for transfer by the RLCs. If this function is not used, out-of-sequence delivery can be provided. In addition to data PDU delivery, reset and condition control procedures can be signaled between peer RLC entities. Control procedures can even use a separate logic channel, so an RLC AM entity can use one or two logic channels.

Encryption can be performed at the RLC layer for both confirmed and unconfirmed RLC modes. In figure 5C, the RLC AM PDU is encrypted 540, excluding the first two bits that comprise the PDU sequence number and the polling bit. The PDU sequence number is an input parameter for the encryption algorithm, and must be readable

38/86 by the peer entity to perform the encryption. The 3GPP TS33.102 specification describes encryption.

The PDU can then be sent to the MAC layer 140 via logical channels. In figure 5C, extra logic channels (DCCH / DTCH) are indicated by dashed lines that illustrate that an RLC entity can be configured to send control PDUs and data PDUs using different logic channels. The receiving side 530 of the AM entity receives AM RLC PDUs through one of the logical channels of the MAC layer. Errors can be checked with the physical layer CRC which can be calculated through the entire RLC PDU. The effective CRC test can be performed on the physical layer and the RLC entity receives the result of the CRC test together with data after decrypting the entire header and possible confirmation condition information can be extracted from the RLC PDU. If the received PDU is a strong message or if the condition information is confirmed for an AM PDU, the control information (condition message) can be passed to the transmission side that checks its relay store against the condition information received. The PDU number of the RLC header is used for decryption 550 and also when storing the encrypted PDU in the receiving store. After all PDUs that belong to a complete SDU are in the receiving store, the SDU can be reassembled. Although not shown, checks for sequential delivery and duplicate detection can then be performed before the RLC SDU is delivered to a higher layer.

When the User Equipment (UE) or mobile station moves between PTM transmission and Ponto-to-Point (PTP) transmission (or changes cells), the RLC entity 152 is reset. This can undesirably result in

39/86 loss of any data found in Radio Link Control (RLC) stores. As noted above, problems can arise when the mobile station moves from one cell to another or when the delivery of Multimedia Broadcast and Multicast (MBMS) content changes from a Point-to-Point (PTP) transmission mode for Point-to-Multipoint (PTM) transmission mode in the server cell.

It is desirable to preserve the continuity of Multimedia Broadcast and Multicast Service (MBMS) transitions between Point-to-Point transmission from Point-to-Multipoint (PTM), or during) PTP) and during transmission transitions (example, handover), and duplicate information.

occur between different cells (to prevent the submission of

To preserve MBMS service continuity and avoid the submission of duplicate information, Layer 2 150 must be able to realign data from the two streams. This synchronization cannot be provided by the physical layer since the network termination point could be different in each mode. If Early Error Correction (FEC) is performed below the RLC 150 layer, as is the case in 3GPP2, data may be lost during any transition between Point-to-Multipoint (PTM) and Point-to-Point (PTP) transmission ), and vice versa. In addition, this would require physical layer synchronization and sharing the same Media Access Control (MAC) between multiple cells (for example, having common programming). As such, this can cause problems in 3GPP2 where these assumptions do not apply.

Point-to-Point Transmission (PTP)

Considering that the application has a significant delay tolerance, the most efficient data transfer mode for Point-to-Point (PTP) transmissions is

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Confirmed Mode (AM) of Radio Link Control (RLC). For example, the confirmed mode (AM) of RLC is typically used for transferring packet-switched data through dedicated logical channels (PTP). The RLC operates in confirmed (AM) mode on dedicated logical channels. As shown in figure 5A, dedicated user traffic for the service of a user in the downlink direction can be sent through a logical channel known as the Dedicated Traffic Channel (DTCH).

In Confirmed Mode (AM), the reverse link is available for relay requests if the data is in error. The RLC transmits Service Data Units (SDUs) and guarantees delivery to its peer entity through retransmission. If RLC is unable to deliver the data correctly, the RLC user on the transmission side is notified. AM RLC operation is generally much more efficient in terms of power at the expense of introducing additional delay.

Point-to-Multipoint Transmission (PTM)

The Common Traffic Channel (CTCH) is a unidirectional channel that exists in the downlink direction and can be used when transmitting information to all terminals or to a specific group of terminals. Both modes of data transfer use common one-way channels that do not have a reverse link channel architecture.

It would be desirable to provide an architecture that allows MBMS service to switch seamlessly between Point-to-Point (PTP) and Pontoa-Multipoint (PTM) transmission modes. To achieve good performance when transitioning between Point-to-Point (PTP) and Point-to-Multipoint (PTM) transmission modes, it would also be desirable to provide an architecture that allows for switching between

41/86 different Radio Link Control (RLC) modes. This can, for example, help to reduce power requirements.

Aspects of the present invention will now be described with reference to the modalities shown and described with reference to figures 6 to 19. These features can, among other things, help preserve service continuity during these transitions by using a new Error Correction layer. (FEC).

Figure 6 is a diagram of a modified UMTS protocol stack having an Early Error Correction (FEC) layer operable in an Early Error Correction (FECd) mode and an Early Error Correction (FECc) mode. The Early Error Correction (FEC) layer allows the underlying Radio Link Control (RLC) entity 152 to switch from a Radio Link Control (RLC) data transfer mode to another Radio Link Control data transfer mode ( RLC) when the User Equipment (UE) changes from Point-to-Point (PTP) transmission to Point-to-Multipoint (PTM) transmission, while maintaining service continuity. According to this modality, the FEC Layer can operate in a first mode (FECc) or in a second mode (FECd). In an implementation, the first mode (FECc) can use parity blocks and the second mode (FECd) can operate without parity blocks. The impact of switching between FECd and FECc modes can be much lower than switching between RLC modes and can be continuous in such a way that no data loss occurs during the transition.

The Early Error Correction (FECc) mode can use external encryption techniques to protect user data. This can be particularly effective through common channels. The Early Correction mode of

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RLC), the number of a layer that is

Error (FECc) allows functionality typically found in Unacknowledged Mode (UM) such as structuring (segmentation and concatenation) and adding sequence number, to occur above the Radio Link Control (RLC) layer. As a result, the Radio Link Control (RLC) layer can use transparent mode (TM) for Point-to-Multipoint (PTM) transmissions because traditional Unconfirmed Mode (UM) functions can be performed on the Early Error Correction layer. (FEC). Although this functionality can be duplicated in the Confirmed Mode (AM) of Radio Link Control (RLC), gains due to ARQ make up this duplication.

By positioning the external coding layer or Early Error Correction (FEC) above the Radio Link Control layer, a sequence can be added independently of the Radio Link Control (RLC). The use of overhead, such as a sequence number with unconfirmed transmissions, can enable the realignment of protocol Data Units (PDUs) with an Encoder Package (EP) during asynchronous MBMS data transmissions. Since sequence numbers are added on a layer above Radio Link Control (RLC), sequence numbers are common in both Point-to-Point Transmission (PTP) ·. as Point-to-Multipoint (PTM) and, therefore, when a transition occurs from Point-to-Multipoint (PTM) transmission to Point-to-Point (PTP) transmission, the continuity of sequence numbers can be maintained. This allows data to be realigned so that duplication of data and / or missing data can be avoided.

External encoding could also be used for Point-to-Point (PTP) transmission, which can potentially gain some power for the system

43/86 and / or reduce the delay for retransmissions. Broadcast and Multicast Multimedia Service (MBMS) data can be tolerant to delay to some extent. In Point-to-Point (PTP) transmissions, a feedback path is provided. This makes the use of Confirmed Mode of Radio Link Control (RLC) more efficient due to the use of ARQ retransmissions when needed which are generally more radio efficient than an FEC scheme in which additional parity blocks are always sent. As such, adding parity blocks to MBMS payload data is unnecessary on dedicated logical channels, for example, Point-to-Point (PTP).

Figures 7A and 7B show modalities of protocol structures of the access layer that include an Early Error Correction (FEC) layer 157 arranged above the Radio Link Control (RLC) layer 150. An Early Error Correction layer modality. (FEC) is described with reference to figure 11.

The Early Error Correction (FEC) layer 157 receives user plan information 163 directly through user plan radio carriers. As the Early Error Correction (FEC) layer is located at the top of the Radio Link Control (RLC) layer, Protocol-FEC Data Units (PDUs) correspond to Service Data-RLC Units (SDUs). The FEC layer preferably supports arbitrary SDU sizes (limited to multiples of 8 bits), variable rate sources, out-of-sequence packet reception of lower layers, and reception of duplicate packets of lower layers. FEC PDU sizes can be limited to multiples of 8 bits.

As described in more detail below with

44/86 reference to figure 9A, the FEC 157 layer segments and concatenates higher layer blocks of user data, such as SDUs, in lines of equal size. Each line can also be referred to as an internal block. Each Protocol Data Unit (PDU) can include overhead. The overhead can include Length Indicators (LIs) that indicate the start of the last Protocol Data Unit (PDU) where data from a specific block of user data, such as a Service Data Unit (SDU) can be located. The collection of PDUs comprises an Encoding Package (EP) or encoding matrix. The number of PDUs included in an Encoder Package (EP) depends, among other factors, on the external code that is used. Compressing each coding matrix line into a separate or independent Transmission Timing Interval (TTI) can increase physical layer performance. To reduce storage loads, Transmission Timing Interval (TTI) durations can be used.

The Encoder Package (EP) can then be passed through an external code encoder to generate the parity lines. As will be described in more detail below with reference to figure 9A, the FEC 157 layer can perform external encoding by providing the functionality of a Reed-Solomon (RS) encoder on the UMTS Terrestrial Radio Access Network (UTRAN) 20 and can perform external decoding for providing the functionality of a Reed-Solomon decoder on User Equipment (UE) 10.

The parity lines generated by the external encoder can be added to the Encoder Package (EP), and placed in a transmission store as a group of internal blocks. Each internal block has information added to it to produce a Data Unit of

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Protocol (PDU). The PDU group can then be transmitted.

This layer of FEC 157 also allows the recovery of data belonging to a single EP, even if different internal blocks are received from different cells. This can be achieved by transmitting a Sequence Number (SN) in the header of each Protocol Data Unit (PDU). In one embodiment, a system Frame Number (SFN) can help maintain data alignment with the Encoder Pack (EP). Sequence numbers are discussed in greater detail throughout this document, for example, with reference to figures 10A and 10B.

The FEC 157 layer can also perform filling and reassembly; transfer of user data; and perform sequential distribution of top layer PDU, duplicate detection, and sequence number checks.

In the modalities shown in Figures 6 to 7A, the Advanced Error Correction (FEC) layer 157 is shown between layer 156 Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) layer 150 (for example, at the same level as the layer (BMC) and below the Packet Data Convergence Protocol (PDCP) layer. By placing layer 157 Advanced Error Correction (FEC) exactly above layer 150 Radioenlace Control (RLC), external code performance can be optimized since the internal block size matches the package size (gold) of the packages that are sent over the air. However, it must be considered that the Early Error Correction (FEC) layer is shown here for illustration purposes only and not for limitation. Packet Data Convergence Protocol layer 156

46/86 (PDCP) can be used over the Advanced Error Correction (FEC) layer 157 for its header compression capabilities. It should be noted that currently Packet Data Convergence Protocol (PDCP) layer 156 is defined for Point-to-Point (PTP) transmission using dedicated logical channels. As shown in Figure 7B, the Early Error Correction (FEC) layer can be provided anywhere within the access extract above the Radio Link Control (RLC) layer or in the application layer. The Early Error Correction (FEC) layer can be below or above the Packet Data Convergence Protocol (PDCP) layer. If FEC is performed on application layer 80, it can also apply to GSM and WCDMA even though the gold packet size is different for both.

External Code Design The new Advanced Error Correction (FEC) layer can perform external coding in user plan information. Figure 8 is a diagram showing an information block 91 and an external code block 95 to illustrate the concept of external block code structures. Figure 9A is a diagram showing an example of how external code block structures can be applied to Broadcast Service and Multimedia Multicast (MBMS) data. External encoding can improve physical layer performance by transmitting delay-tolerant content across an entire cell. External codes can, for example, help prevent data loss during transition between cells and during transitions between Point-to-Point (PTP) transmission mode and Point-to-Multipoint transmission mode (PTM).

An external code block 95 can be represented in the form of a matrix that includes k Units

47/86 of ο

Protocol Data and Nk parity lines 93. In external block coding, data can be mounted in information block 91 or broad encoder package by organizing user data in k payload lines by segmenting, concatenating, and filling data (including inserting support information in the blocks internal) and then encode the resulting information block 91 to generate Nk parity lines 93 that can be added to the information block 91 to produce an external code block 95. Parity blocks 93 add redundancy information to information block 91. Individual lines of the external code block can eventually be transmitted through single or multiple Transmission Timing Intervals (TTI). Redundancy information for a set of Protocol Data Units (PDU) can allow the original information to be reconstructed even if some of the PDUs are lost during transmission.

Figure 9A shows an exemplary external code structure shown as a ReedSolomon (RS) block code. Reed-Solomon (RS) codes can be used to detect and correct channel errors. The external code shown in Figure 9A is a systematic block code (n, k), where each Reed-Solomon (RS) code symbol comprises an information byte defined by a line and a column. Each column comprises a code word of Reed-Solomon (RS). If n missing blocks are to be recovered, then at least n parity blocks are required. As such, the amount of memory required increases as the number of parity blocks increases. In Reed-Solomon (RS) coding, Nk parity symbols can be added to the k systematic symbols to generate a code word. In other words, a word

48/86 code of a Reed-Solomon (RS) code [N, k] has k systematic or information symbols and Nk parity symbols. N is the length of the code, and k is the dimension of the code. For each k bytes of information, the code produces n encoded symbols, the first k of which can be identical to the information symbols. Each line can be referred to as an internal block, and represents the payload per Transmission Timing Interval (TPI). In regular WCDMA systems, transmission can occur, for example, through the basic 20 ms WCDMA frame structure (TTI). Parity symbols can be derived from systematic symbols using a Gk generator matrix_xNdefined as:

mixk. Gjçxn (Eguaçao 1) = word of information = [m₀ mi ... (Equation 2)

Cixn = code word = [c₀ Ci ... Cn-J (Equation 3) where mi, ci belongs to an arbitrary Galois Field. For example, if the Reed-Solomon (RS) code word symbol is a bit, then the 2-dimension Galois field (GF (2)) would be used to describe the decoding operations. In one embodiment, if the symbol is an octet, then the 256 GF (256) Galois Field can be used to describe decoding operations. In this case, each column of information consists of 1-byte per line. Each column of information can be coded using a Reed-Solomon (RS) code [N, k] in relation to the 256 GF (256) Galois field. If there are Mbytes per line, the external block is encoded M times. Therefore, there are N * M bytes per external block 95.

Erase Decoding

The external code structure allows correction of deletion. If the decoder already knows which symbols are in error, the reconstruction of the systematic erroneous symbols

49/86 requires a relatively small amount of computation. An Encoder Package (EP) or matrix refers to the entire set of data in the output of the external encoder. Redundancy information is considered in terms of the column from each row, and each row that is transmitted has a CRC attached to it that you should check to confirm that the data was sent correctly. In the case of MBMS transmissions, a CRC can be used on each transport channel block that indicates whether an internal block 91 is in error or not, and if the CRC fails, it can be assumed that all symbols in the block are in error. In one embodiment, if a particular internal block 97 is in error, then all bits for that block can be cleared. The term erasure refers to each symbol belonging to an erroneous block whose CRC has failed. Symbols, which are not erasures, can be considered as correct. Omitting the probability of undetected CRC errors, then each Nxl column contains correct and erased symbols.

The vector r received can be written as: ⁼[^çThe^eec3^ç4^ec6^ç8..^çwJ (Equation 4) where and identifies deletions.

Erase decoding allows up to Nk erroneous symbols to be corrected. Because it can be assumed that symbols, which are not erasures, can be corrected, the error correction property of RS codes is typically much better than that of typical RS codes. The size of the CRC used in each internal block must be large enough to ensure that the probability of undetected errors does not exceed the probability of residual external block. For example, if a 16-bit CRC is used in the internal blocks, then the lower boundary of the external block error rate

Residual 50/86 will be 2^-16 = 1,5.10^-5. If there can be no errors in the first k internal blocks, RS decoding does not need to be performed since the systematic symbols are identical to the information symbols.

It can be seen that as soon as the k blocks with suitable CRC are received, the decoding of the external block can be performed, without waiting for the receipt of all N internal blocks. To perform erasure decoding, the generating matrix Qkxk can be derived from the generating matrix G_kXBy removing all columns corresponding to unnecessary deletions or blocks, for example, only the first k suitable received symbols can be used to identify the modified generating matrix Qkxk- The original information word m can be retrieved as follows:

^mixk r_lxk (Equation 5) where r {_xk is the modified received vector obtained with the first k appropriate symbols. The complexity of erasing decoding, therefore, can be reduced to the complexity of a kxk matrix inversion. In this way, the use of RS erase decoding can greatly simplify the computational complexity of RS decoding.

Impact of Data Packing on Performance

External Code

As will be discussed below with reference to Figures 11-13, external coding can be used in conjunction with variable rate data sources without resulting in excessively large overhead if the amount of

51/86 filling and support information sent over the air is limited by the specific external coding scheme. In the external code scheme discussed above, data can be compressed into blocks of a given size, and a reduced Reed-Solomon code can be executed across the blocks. The encoded packet data can be packaged in TTI in at least two different forms which will now be described with reference to Figures 9A and 9B.

Figure 9B is a diagram showing the external coding block structure of Figure 9A in which multiple lines can be sent by Transmission Time Interval (TTI). According to another aspect of the invention, data from one line is transmitted in a single TTI. In another embodiment, data from an Encoder Package (EP) line is placed in a TTI in such a way that each TTI contains data from that Encoder Package (EP) line. As such, each of the lines can be transmitted in a separate WCDMA frame or Transmission Timing Interval (TTI). Transmitting each line to a TTI will provide better performance. In Figure 9B, ken are divided by the number of lines by TTI, and errors on one line can be fully correlated. This creates a considerable difference when looking at the EP error rate versus the TTI error rate.

Figure 9C is a diagram showing the external block structure of Figure 9A in which each line can be sent in multiple TTIs. It must be considered that although Figure 9C illustrates the sending of each line of the Encoder Package (EP) through four TTI (TTIO - TTI3), in reality each line could be sent through any number of TTI. Since each column is an external coding codeword, each of the four distinct transmission phases (TTIO - TTI3) means a

52/86 independent external code. For the entire package to be recovered, it would be necessary for all of these independent external codes to decode correctly.

Figures 10A and 10B are diagrams showing the external coding blocks generated by the Early Error Correction layer.

The FECc mode can be used in Point-to-Multipoint (PTM) or common logic channels to build blocks 95 of external coding by adding parity lines or blocks 93 to the MBMS payload data 91. Each outer block 95 includes a plurality of inner blocks 91, 93. Identifying the sequence of internal blocks and their position in relation to the encoding packages can allow each available internal block to be placed in the correct position so that the external decoding can be done correctly. In one embodiment, each inner block includes a header 94 that identifies the inner block by means of an inner block number m and an outer block number n. For example, the outer block n includes a data portion 91 with m Broadcast Service and Multimedia Multicast (MBMS) payload blocks, and a redundancy portion 93 having M- (m + l) internal parity blocks. According to this modality, the sequence number space can be optimized for MBMS and can be defined by some distinct sequence numbers, for example, 0 to 127. The sequence number space must be large enough so that the same sequence number will not appear from a reception interval caused by a transition of any kind. The receiving UE must be able to determine the order of the internal blocks, even if some internal blocks are lost. If the UE loses a larger number of internal blocks than can be identified by the sequence number space as a

53/86 whole, the UE will not be able to correctly reorder the internal blocks. The sequence number of the same internal block is identical through the FECd blocks and FECc blocks. FECd blocks do not include the redundancy part 93 used in FECc blocks. The FECd entity and the FECc entity can use the same bit rate over the air.

Transmission Side

The Transmission Error Early Correction (FEC) entity 410 includes a Service Data Unit (SDU) 412 to receive the SDUs, a segmentation and concatenation unit 414, an external encoder 416 that performs Reed-Solomon encoding (RS), a sequence number generator 418 that adds a sequence number to the encoded PDUs, the transmission store 420 transmits the PDUs through logical channels 406, and a programming unit 422.

Service Data Unit (SDU) store 412 receives user data (FEC SDU) in the form of Service Data Units (SDU) on radio carrier 402 as indicated by the arrow, and stores FEC SDU from layers higher. The receiving store 412 communicates to the programming unit 422 the amount of data that will be transmitted.

As discussed above, the amount of time it takes to fill an Encoder Package (EP) will typically vary since the source data rate typically varies. As explained with reference to Figure 13, frame filling efficiency can be improved by having the flexibility to decide when to start data packaging. The amount of filling introduced can be reduced by delaying the creation of the EP as much as possible based on the fluctuation tolerance of the receiving 430 FEC entity.

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Programming entity 422 can decide when to start coding. Programmer 422 preferably determines how long it is possible to wait before a packet needs to be sent, based on the QoS profile for that specific service. When programmer 422 establishes that sufficient data has accumulated, or that the maximum acceptable packet transmission delay has elapsed, it activates the creation of an Encoder Pack (EP) 91. The segmentation and concatenation unit 414 separates the Service Data Unit (SDU) into several lines and generates the Length Indicators (Lis).

Programming unit 422 preferably decides the optimum line size of the EP or Protocol Data Unit (PDU) so that the SDUs accommodate exactly the number of lines (for example, 12). Alternatively, programmer 422 selects an FEC PDU size, from those configured by the RRC, which will result in the least possible filling, and requests that the Segmentation &amp; Concatenation function 414 format the SDUs in k blocks of size PDU_size-FEC_Header_size. This formatting may vary. Examples of different types of formatting are discussed below with reference to Figures 12-13. The total amount of data considered must include the overhead that will be incorporated by the 414 concatenation and segmentation function. To generate the Encoder Package (EP), programmer 422 requests that the concatenation and segmentation function 414 produce k PDU of that size. This size includes reassembly information. In one embodiment, PDUs can have sizes in multiples of 8 bits, and consecutive PDU data correspond to different symbols in the code words.

The k PDU blocks can then be executed through external encoder 416 which performs

55/86 Reed-Solomon (RS) coding. External encoder 416 encodes the data in the Encoder Package (EP) matrix by generating and attaching redundancy or parity information to the Encoder Package (EP) matrix to create an external encoding block. In one embodiment, the external code can be assumed to be an erase decryption block code (n, k) and the external encoder generates nk parity blocks. The encoder performs the encoding in k lines of information of equal length and distributes to the lower sublayer n Protocol Data Units (PDU) of that same size. The first k blocks are identical to those he receives, and the following nk blocks correspond to the parity information.

Programmer 422 also monitors the time alignment or relative timing of PTM flows, and performs transmissions to adjust the alignment of different logical flows. For example, during reconfigurations, the time alignment between logical PTP and PTM flows can be adjusted to benefit service continuity. The best performance can be obtained when the flows are perfectly synchronous.

Different base stations (or different PTP, Point-to-Multipoint (PTM) transmission modes) transmit the same content stream, but the streams may be misaligned. However, if the Encoder Pack (EP) format of the data streams is identical, then the information in each stream is exactly identical. Adding a sequence number to each external block allows the User Equipment (UE) to combine the two flows since the User Equipment (UE) will know the relationship between the two flows.

The sequence number generator 418 attaches a sequence number to the front of each block, in the same

56/86 sequence than that used in the 416 encoder to create the PDUs. In one embodiment, the sequence number generator adds, for example, an eight-bit sequence number in front of each external code block to generate the PDUs. Additional overhead can also be added to the external code block. The sequence number space must be large enough to accommodate the time difference, at worst, between flows. Therefore, in another embodiment, the sequence number space of 20 can be used, and at least five bits can be reserved in each header for a sequence number. This header can be attached to the external code block after Reed-Solomon (RS) coding is performed, and therefore this external header is not protected by the external code. Sequence numbers are also preferably added to the parity blocks, even if they cannot be transmitted. In one embodiment, the sequence number phase can be aligned with the encoder packet boundary. A sequence number bearing would correspond to the receipt of a new Encoder Package.

Early Error Correction (FEC) header format

As noted above, data stream synchronization can be achieved by entering a sequence number that includes information associated with PDU ordering. In addition to reordering and duplicate detection, the sequence number allows data from the respective sources that are included in an Encoder Package to be realigned. This sequence number can explicitly identify the order in which each packet is to be considered. This sequence number can comprise an FEC header that can be attached to the Payload Units (PDU) of information and parity blocks after

57/86 coding be performed. The sequence number must be protected by the external code since it is necessary for decoding.

Figure 14 is a diagram of a modality of an Early Error Correction (FEC) header format. To facilitate data alignment with the Encoder Pack (EP), the sequence number can be divided to include a reserved part (R) 402, an Encoder Pack (EP) part 404 that identifies the EP (EPSN), and a Pack Intra-Encoder that identifies the position of a specific internal block within the Encoder Package (IEPSN) 406.

It is desirable for the FEC 400 layer to be able to interact with all Radio Link Control (RLC) modes. Since AM Radio Link Control (RLC) and UM Radio Link Control (RLC) both require Service Data Units (SDU) that have sizes in multiples of 8 bits, then it would be desirable for the FEC 400 layer to also adhere to this requirement. Due to the fact that the external code for the FEC 400 layer operates in increments of data byte size, the Encoder Package (EP) line size would also need to be an integer number of bytes. Therefore, the 401 size of the FEC header must also be a multiple of 8 bits for the size of the FEC Protocol Data Unit (PDU) to be acceptable for Radio Link Control (RLC). In an embodiment in which the 401 Early Error Correction (FEC) header can be a byte, with a reserved (R) 402 part comprising a single bit, the part identifying the EP (EPSN) 404 comprising 3 bits, and the IEP part that identifies the position of the PDU within the Encoder Package (IEPSN) 406 comprising 4 bits. In this modality, an 8-bit sequence number is used since it is expected that a PDU will be sent by TTI and a

58/86 since the transmission time of different cells should not fluctuate by more than 100 ms.

transmission storage 420 stores the PDUs until a data frame accumulates. When the PDUs are requested, the transmission store 420 transmits the frames, one by one, through the radio interface (Uu) through a logical channel to the MAC layer. The MAC layer then communicates the PDUs through transport channels to the physical layer where the PDUs can eventually be communicated to the UE 10.

Receiving Side

Still referring to Figure 11, the receiving Early Error Correction (FEC) entity 430 includes a receiving duplicate store / reordering / detection unit 438, a sequence number removal unit 436, an external decoder 434 that performs Reed-Solomon (RS) decoding, and a 432 reassembly transmission unit / Service Data Unit (SDU) transmission store.

Information lines in the EP matrix correspond to the PDUs. To support external encryption, the receiving Early Error Correction (FEC) entity 430 accumulates an FEC PDU number before enabling external decoding. To obtain continuous reception, despite the need to decode encoder packets, the User Equipment (UE) temporarily stores the Protocol Data Units (PDU) that arrive while performing the decryption.

The receiving store 438 can accumulate the PDUs until the entire Encoder Pack (EP) is received or until the programming unit (not shown) is satisfied that there are no more retransmissions to the Encoder Pack (EP). When

59/86 decided that there will be no more data received for a given encoder packet, the missing PDU's can be identified as deletions. In other words, PDUs that do not pass the CRC test will be replaced by erasures in the decoding process.

Due to the fact that some blocks could be abandoned during transmission, and also due to the fact that different data flows may have different delays, the receiving 430 Early Error Correction (FEC) entity performs duplicate detection and potentially block reordering. duplicate detection / storage / reordering / receiving unit 438. 0 sequence number can be used in each FEC Protocol Data Unit (PDU) to assist duplicate / reorder detection. The sequence number can be used in the receiving store 438 to reorder data received out of order. When PDUs are reordered, the duplicate detection unit detects duplicate PDUs in the Encoder Package (EP) based on their sequence numbers, and eliminates any duplicates.

The sequence numbers can then be removed. The sequence number removal unit 436 removes the sequence number from the Encoder Package (EP) since the sequence number may not be part of the block sent to the Reed-Solomon (RS) decoder.

The data can then be passed to the external decoding function 434 to retrieve missing information. The external decoder 434 receives the Encoder Pack (EP), and, if necessary, decodes in the Reed-Solomon (RS) mode the Encoder Pack (EP) using the parity information to regenerate any erroneous or missing lines. For example, if all k Protocol Data Units (PDUs) containing information are not

60/86 received correctly, or a number less than k of n PDU are not received correctly, then Protocol Data Units (PDU), up to the size of the parity PDUs, external decoding can then be performed to recover the PDUs missing information. At least one parity PDU will be available on the receiver whenever external decoding is performed. If all k Protocol Data Units (PDU) containing information are received correctly, a number less than k among the n PDUs, is received correctly, then decoding is unnecessary. The Information Protocol Data Units (PDU) can then be distributed to the 432 reassembly function.

Regardless of whether the external decoding was successful or not, the information lines can then be distributed to the reassembly unit / function 432. The reassembly unit 432 reassembles or reconstructs the SDU from the information lines of the Package matrix. Encoder (EP) using the Length Indicators (LI). When the SDUs are successfully put together, the Service Data Units (SDU) transmission storage 432 transmits the Service Data Units (SDU) through the radio carrier 440 to distribute the SDUs to the upper layers.

In the receiving Early Error Correction (FEC) entity 430, enabling UEs to delay decoding through a time shift between different logical streams can allow the system to take full advantage of receiving data out of potential sequence due to the absence synchronization between logical flows. This relieves service during handoffs as well as transitions between PTP and PTM. An algorithm to allow UEs to delay decoding by time shift

61/86 between different logic flows is discussed with reference to Figure 15.

Encoder Package (EP) Options: Fixed Line Size or

Variable

The FEC or external code entity has flexibility in relation to when Protocol Data Units (PDU) can be built since Protocol Data Units (PDU) do not need to be sent continuously at each Transmission Timing Interval (TTI). This can result in greater frame filling efficiency, and less filling support information.

If desired, the external code entity can generate a payload at each Transmission Timing Interval (TTI). Protocol Data Units (PDU) can be built in real time as Service Data Units (SDU) that can be received from the upper layers. If there is not enough data to build a Protocol Data Unit (PDU), then RLC can add padding.

Fixed Line Size Encoder (EP) Packets

When coding, SDU 201-204 it is desirable to reduce the amount of filling that will be transmitted as much as possible.

In one embodiment, the line size of the Encoder Packet (EP) array 205 may be a fixed size. Prior knowledge of the line size of the Encoder Packet (EP) 205 array can allow data alignment back to its original configuration. Due to the fact that the line size of the SDU 201-204 that will be sent is known in advance, the transmission can start as soon as the data is received without having to wait to see the amount of data that must be sent.

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Figure 12A shows an example of a coding process for creating an external code block 214 from data units 201-204 in which line sizes of the external code block 214 can be fixed. In this example, user data takes the form of a plurality of Service Data Units (SDU) 201-204 that include a block of bits of arbitrary size, the size of which depends on the specific application (video, voice, etc.).

To allow the transmission of FEC SDU of arbitrary sizes, segmentation, concatenation and filling can be performed at the FEC level. Although concatenation is not strictly necessary, its absence would lead to significant degradation in the processing of upper layer data.

The top layer SDU 201-204 can first be formatted in this fixed size PDU. In this modality, a segmentation / concatenation function generates internal blocks of a fixed size that can be indicated for the subscriber unit. In step 220, the group of inner blocks can be segmented and concatenated to become part of an encoder array 205 that includes inner blocks, padding 208 to the required point, and Length Indicators (LI) 206 that can be used to point to an end of the Service Data Unit (SDU), 201-204 by indicating how many SDU's end in a given EP line. The external encoder, discussed below, uses these internal blocks to produce redundancy blocks.

In Radio Link Control (RLC), a Length Indicator (LI) indicates the end of each Service Data Unit (SDU) that is identified in relation to the Protocol Data Unit (PDU), more properly than the Data Unit Service Data (SDU). This helps to reduce

63/86 overheads since the size of the PDU is typically smaller than that of the Service Data Unit (SDU). For example, a Length Indicator (LI) can be used to indicate the last octet of each FEC Service Data Unit (SDU) ending within the Payload Data Unit (PDU). The Length Indicator can be adjusted to the number of octets between the end of the FEC header and up to the last octet of an SDU FEC segment. The Length Indicator (LI) can preferably be included in the PDUs to which the Length Indicator (LI) refers. In other words, the Length Indicators (LI) preferably refer to the same Payload Data Unit (PDU), and are preferably in the same order as the FEC SDU to which the Length Indicator (LI) refers.

When the external block is received, information, such as Length Indicators (Lys), can be used to inform the receiver where the Service Data Unit (SDU) and / or filler starts and ends.

Due to the fact that it is not possible to use a bit in the FEC Header to indicate the presence of a Length Indicator (LI), the FEC layer adds a fixed header within the payload that indicates the presence of Length Indicators (LI). An internal header or LI provides all the information needed to reconstruct SDU 201-204. The LI can be included in the PDU-RLC to which it refers. The presence of the first LI can be indicated by a flag included in the PDU-RLC sequence number header. A bit in each LI can be used to indicate its length. To allow the length of the Length Indicators (LI) to change with the size of the FEC PDU, a new special value for the one-byte Length Indicators (LI) can be introduced indicating that the previous SDU

64/86 ended one byte before filling in the last PDU. The presence bit of Length Indicators (Lys) can be implemented in several ways, two of which are discussed below.

In one embodiment, the Length Indicator (LI) presence bit can be provided in each Protocol Data Units (PDU). For example, a byte can be added at the beginning of each Encoder Package (EP) line, and a bit in that byte indicates the presence of the LI. The first whole byte of each Protocol Data Unit (PDU) can be reserved for this presence bit. To accommodate this presence bit, the Length Indicator data can be reduced by one bit. Providing a presence bit on each Packet Unit (PDU) allows SDU's to be decoded when EP decoding fails, even if the first PDU is absent. This can result in a lower residual error rate. Providing a presence bit in each PDU also allows real-time concatenation / segmentation.

In another embodiment, the Length Indicator (LI) presence bits can be provided on the first PDU. Instead of adding overhead at the beginning of each PDU, the presence bits for all k information PDUs can be added at the beginning of the first EP PDU. Providing the presence bit at the beginning of the Encoder Package (EP) results in less support information when you have large SDU and / or small PDU.

After segmentation and concatenation, EP 205 includes a number of lines occupied by at least one of the various Service Data Units (SDU) 201-204 and filling blocks. The line size of an external block can be designed in such a way that each line can be transmitted during a Transmission Timing Interval (TTI)

65/86 at a maximum data rate. Service Data Units (SDU) generally cannot be aligned with the amount of data sent during a Transmission Timing Interval (TTI). Thus, as shown in Figure 11, the second and fourth SDU 202, 204 do not fit in the Transmission Timing Interval (TTI) of the first and second lines, respectively, of the EP. In this example, the EP has twelve lines available for data, and the four SDU 201-204 can be packaged in the first three lines of those twelve lines. The remaining lines of EP 205 can be occupied by filling blocks 208. In this way, the second SDU 202 can be divided so that a first part of the second Service Data Unit (SDU) 202 begins on the first line of the information block and a second part of the second SDU 202 ends on the second line.

Similarly, the third SDU must be divided so that a first part of the third Service Data Unit (SDU) 203 begins on the second line and a second part of the third SDU 203 part ends on the third line. The fourth

Service Data Unit (SDU) 204 fits within the third line, and the remainder of the third line can be filled with padding blocks 208. In this example, the coding package (EP) 213 is composed mostly of padding 208.

The encoder uses the EP to generate redundancy or parity information. In step 240, an encoder encodes the encoded intermediate packet matrix 205 by adding external parity blocks 214 to generate an external code block 213 that is 16 blocks long. The encoder extracts 8 bits of data from each column of each block to create resulting data 210. The Reed-Solomon (RS) encoder encodes the resulting data 210 to obtain four lines of information from

66/86 redundancy or parity 212. Parity information 212 can be used to generate external parity blocks 214 which can be attached to the EP matrix 205 to generate external block 213 of 16 blocks.

Figure 12B shows an example of the information transmitted over the air in the example discussed above. In step 260, after adding additional overhead that includes the sequence number for each EP 205 line, block 213 of 16-block external code can be transmitted over the air as Protocol Data Units (PDU) 214. The Packet matrix - Complete or entire encoder (EP) 213 is not transmitted in the Protocol Data Units (PDU) 214 sent in the downlink. Preferably, the Protocol Data Units (PDU) include information bits 201-204 and Length Indicators (LI) 206 of the encoder packet (EP) matrix 213. Since the line size of the Packet-Encoder (EP) 213 is fixed and therefore known at the receiver, it is unnecessary to effectively transmit the filling 208 over the air. The filling information 208 is not transmitted in the downlink since the filling values ​​are known, and therefore there is no need to transmit the filling information 208. For example, if the filling can be composed of a known sequence of bits such as like all zeros, all ones, or an alternative pattern of zeros and ones, the receiver can fill the Protocol Data Units (PDU) 214 up to the nominal line length of the encoder (EP) packet 213. Therefore, during transmission, instead of selecting the PDU size equal to the EP line size, the smallest available EP size that carries all bits of information 201-204 and reassembly support information (for example, LI) 206 can be used.

Although the matrix line size of

67/86 encoder is fixed, the size of the FEC PDU could be selected from a given set in each transmission in such a way that each of them includes all the information part of a single line of encoder matrix (the filling could be deleted). Upon receiving a PDU of a size smaller than the encoder matrix line size, the UE can fill up to the size with a known bit sequence. This allows the size of the internal block to remain fixed, without increasing the load on the air interface. Using a fixed line size Encoder Pack (EP) 213 in this way can eliminate the need to wait until all data is available before beginning to transmit the Protocol Data Units (PDU), and it can also be eliminated the need to send the filling.

If the above algorithm is implemented to handle variable rate transmission, then a rate equalization scheme can be used in which all lines of the encoder packet matrix are of constant size. Smaller PDUs could be used when filling is part of the PDU. The padding may consist of a specific sequence of bits, and may be located at the very end of the data. At the receiver, the size of the blocks received from the lower layers can be equalized to a baseline size by attaching the filler at the end.

If a predefined bit sequence can be used for filling, that filling is not transmitted over the air. The receiver does not need to be aware of the current encoder packet line size unless the receiver needs to perform external decoding. Basic SDU reassembly does not require knowledge of the fill quantity at the end of a PDU. If all PDUs containing information to be

68/86 from the first k lines of encoder (EP) packet are received, then external decoding is unnecessary. Conversely, if at least one PDU containing information from the first k encoder packet (EP) lines is missing, then at least one of the PDUs containing data from a parity line is required. Since the parity lines are generally not filled, the size can be used as a reference to the actual encoder packet size that needs to be assumed.

Variable Line Size Encoder (EP) Packets

Figure 13 shows a coding process for creating an external code block 313 having a variable line size.

This aspect of the invention relates to the encoding of a flexible external block of data transmitted over the air interface. This encoding process results in less padding being transmitted so that the padding efficiency increases. The Encoder Pack (EP) 305 lines can be of variable size ·, and an external block of different size can be sent for each Transmission Timing Interval (TTI). Preferably, the line size of the Encoder Pack (EP) 305 changes in such a way that the SDUs fit exactly the number of lines (e.g., 12) of the Encoder Pack (EP) array 305. In this modality, the FEC layer can wait for all data to be available before building the EP so that the FEC layer can determine the optimal line size. The line size can be selected from a number of different sizes based on the amount of data available to limit filling. The line size of the Encoder Package (EP) can be linked to the set of sizes

69/86 PDU that are configured for the S-CCPCH. Depending on the amount of data available at the time when the 305 encoder pack needs to be generated, the line size that results in the minimum padding can be selected. By decreasing the size of the external block 313 so that the block size can be smaller in each frame, the data can be sent at a reduced transmission rate since a smaller number of data is sent over the same duration as the TTI. Using a variable line size of the Encoder Pack (EP) 305 helps to stabilize power requirements across all transmissions to the encoder packets (EP), and also uses less parity overhead (314). This modality works properly with Point-to-Multipoint (PTM) transmissions in systems such as WCDMA in which the underlying wireless protocol allows the size of the transport block sent at each Transmission Timing Interval (TTI) to be variable.

In step 320, several Service Data Units (SDU) 201-204 can be segmented and concatenated to generate an Encoder Packet (EP) 305 matrix in which Length Indicators (LI) 206 can be used to indicate an end of the Service Data Unit (SDU) 201-204. Length indicators (LI) can be included in the last line on which the Service Data Unit (SDU) ends.

In step 330, redundancy or parity information is generated on a column basis by extracting eight bits of data from each data block, and the resulting data 310 can be sent to a Reed-Solomon (RS) encoder for obtain parity information 312. Due to the fact that the lines of the 305 matrix of Encoder Package (EP) are smaller, less information of

70/86 redundancy can be generated.

In step 340 the coding continues, when parity information 312 is used to generate external parity blocks 314 that can be attached to the twelve-block Encoder Package (EP) matrix 305 to thereby generate an external code block that in this example is 16 blocks long. This modality avoids filling transmission that improves transmission efficiency since the entire external code block 313 is occupied either by the SDU, Length Indicators (LI) 206, and / or redundancy information 314. In this specific example, no filling was required. However, it must be considered that in some cases, due to the limited number of configured sizes of the PDU, some filling may be necessary despite the reduced amount of filling. This results in higher frame filling efficiency, and can also allow more constant energy to be maintained across the entire Encoder Package (EP). This is desirable on CDMA systems that use power control schemes.

Although not shown, transmission of PDUs over the air would occur in a similar manner to that discussed above with respect to step 260 in Figure 12.

Figure 11 is a modality of an Early Error Correction (FEC) layer 400 or external coding having a non-confirmation mode RLC (UM) + entity (RLC UM +) provided above the radio link control layer (RLC) . Typically, radio link control (RLC) provides structure for upper layers. Here, the FEC layer that is located above the Radio Link Control (RLC) performs the structuring.

The external coding layer 400 includes an Early Error Correction (FEC) entity 410

71/86 transmission that communicates through the radio interface (Uu) 404, through logical channels 406, with a receiving entity of Early Error Correction (FEC) of reception.

Duplicate Reordering / Detection

Figure 15 is a reordering protocol or algorithm to allow mobile stations 10 to delay decoding by the time shift between different logical flows.

The receiving Early Error Correction (FEC) entity 430 uses the sequence number to determine the position of a given PDU within the EP matrix. For example, a part of the sequence number (PSN) identifies the position of the PDU in the encoder (EP) packet.

sequential storage.

This algorithm assumes that, at most, data from two encoding (EP) packets is received before decoding can be started. In the description below, the Encoder Package (EPd) is the next Encoder Package (EP) in sequence to be decoded, and the Encoder Package (EPb) is the Encoder Package (EP) that is being stored. The Encoder Package (EPb) comes after the Encoder Package (EPd). UE implementations needing the total encoder packet transmission time to perform RS decoding will need double in order to be able to decode packets The UE therefore stores at least n + k of the maximum length lines of the encoder matrix (ken being respectively the number of information lines and the total number of lines including parity lines). A UE having a faster decoding mechanism can reduce this requirement, although not less than n + 1. For example, if the UE has a certain amount of storage space (XtraBffr) in addition to that needed to receive

72/86 sequential packets based on their decryption capacity, and if a 64 kbps flow is assumed, delaying decoding by 100 ms without increasing computational requirements would require an increase of 800 bytes in storage size.

In block 1410, it can be determined whether a new Protocol Data Unit (PDU) for Early Error Correction (FEC) is received. If a new Protocol Data Unit (PDU) for Early Error Correction (FEC) is not received, then the process resumes at block 1410. If a new Early Error Correction Protocol (PDU) Unit is received, at block 1420 a determination can be made as to whether the new Early Error Correction Protocol Data Unit (PDU) ( FEC) belongs to the next encoder packet (EPd) in the sequence to be decoded.

If the Early Error Correction Protocol (PDU) Data Unit (FEC) does not belong to the next encoder (EP) packet in the sequence to be decoded, then in block 1421, a determination can be made as to whether the Error Correction Protocol (PDU) Data (FEC) belongs to the Encoder Package (EPb) that is being temporarily stored. If the Advanced Error Correction Protocol (PDU) Data Units (FEC) does not belong to the Encoder Package (EPb) that is being temporarily stored, then in block 1440 the Protocol Data Unit (PDU) can be discarded. If the Protocol Data Unit (PDU) for Early Error Correction (FEC) belongs to the Encoder Package (EPb) that is being temporarily stored, then in block 1423 the Protocol Data Unit (PDU) can be added to the EPb in the associated position. In block 1425,

73/86 can be determined if the amount of data for EPb exceeds XtraBffr. If in block 1426 it is determined that the amount of data for EPb does not exceed XtraBffr, then the process restarts in block 1410. If the amount of data for EPb exceeds XtraBffr, then in block 1428, the transmitting entity attempts to distribute the complete SDU from of EPd. Then, in block 1430, the remainder of EPd can be removed from the store, and in block 1434 EPb can be set to EPd.

If it is determined in block 1420 that the Early Error Correction Protocol (PDU) Unit belongs to EPd, then in block 1422, the Protocol Data Unit (PDU) can be added to the EPd store in the associated position. In block 1424, it can be determined that the store has k individual PDUs for EPd. If the store does not have k individual PDUs for EPd, then in block 1426, the process restarts in block 1410. If the store has k individual PDUs for EPd, then in block 1427 the decoder performs external decoding for EPd, and then in block 1428, the transmitter tries to distribute the complete SDUs from EPd. Then, in block 1430, the remainder of EPd can be removed from the store, and in block 1434 EPb can be adjusted to EPd.

Figure 16 is a diagram showing a temporal relationship between external code blocks received by a mobile station when the mobile station transitions between receiving a Point-to-Multipoint (PTM) transmission from cell A 99 and another Point-to-Multipoint (PTM) transmission from cell B 99. Some aspects of Figure 16 are further discussed in the United States Patent Applications US-2004-0037245-A1 and US-2004-0037246-A1 by Grilli, et al., Filed on December 21

74/86 August 2002, and United States Patent Application US2003-0207696-A1 by Willenegger, et al., Filed on May 6, 2002, which are incorporated herein by reference in their entirety.

The illustrated scenario assumes certain requirements of the UMTS Terrestrial Radio Access Network (UTRAN) 20 and User Equipment (UE) 10. For example, if UTRAN 20 sends content using the same external block encoding through the cells, then the same numbering must be used in blocks carrying the same data or payload in neighboring cells. External blocks that have the same number are transmitted relatively aligned in time. 0 maximum misalignment of PTM transmission across cells is controlled by the Radio Network Controller (RNC)

24. The UTRAN 20 controls the delay fluctuation in Point-to-Multipoint (PTM) transmission through the cells. The UE 10 must be able to decode an external block while the next block is being received. Therefore, a storage space in the UE should preferably accommodate at least two external blocks 95A-95C since memory for an external block is required to accumulate the current external block. Memory must also be able to accumulate internal blocks of lines if the external blocks during Reed-Solomon (RS) decoding, and compensate for inaccuracies in time alignment across base stations 22.

In cell A 98, during transmission of the external block η 95A, a transition occurs during the transmission of the second internal payload block of the Broadcast and Multimedia Multicast Service (MBMS). The slope of arrow 96, which illustrates the transition from User Equipment (UE) 10 from cell A 98 to cell B 99, is non-horizontal since a certain time elapses during

75/86 transition. By the time User Equipment (UE) 10 reaches cell B 99, the fifth block of Multimedia Broadcast and Multicast Service (MBMS) payload data is being transmitted. As such, User Equipment (UE) 10 loses the second to four blocks due to the time misalignment of the respective transmissions and the time that elapses during the transition. If sufficient blocks are received in cell B 99, the outer block η 95A can nevertheless be decoded because the parity blocks can be used to reconstruct the missing blocks.

Later, during the transmission of the external block n + 2 95C, the User Equipment (UE) 10 experiences another transition from cell B 99 to cell A 98, which occurs in the fifth block of the Broadcast Service payload and Multimedia Multicast (MBMS) of the external block n + 2 95C. In this situation, fewer internal blocks are lost during the transition, and the internal blocks can still be recovered.

The use of external code blocks can help to reduce the likelihood of any service interruption. To ensure that error recovery works, the same blocks must be sent on each transmission path, which means that the parity blocks must be constructed the same way on each transmission path. (The payload blocks and Broadcast Service and Multimedia Multicast (MBMS) are necessarily identical in each route since it is a broadcast transmission). Performing Early Error Correction (FEC) in the upper application layer 80 helps to ensure that the parity blocks are identical in each transmission path since the coding is done in the Early Error Correction (FEC) layer 157 and is, therefore, the same for each

76/86 external block. Conversely, if the coding is done in a lower layer, for example, in the individual radio link control entities (RLC) 152, then some coordination is required since the parity blocks will be different in each transmission path.

Transition from Point-to-Multipoint (PTM) to Point-to-Point (PTP)

Figure 17 is a diagram showing a temporal relationship between external code blocks received by a mobile station 10 when a transition occurs between a Point-to-Multipoint (PTM) transmission and a Point-to-Point (PTP) transmission . The scheme shown in Figure 17 applies, for example, to systems using Point-to-Point (PTP) transmissions, such as WCDMA and GMS systems.

One aspect of the present invention relates to Early Error Correction by adding parity information or blocks to the internal MBMS payload or data blocks during PTM transmission. Each external code block transmitted in a PTM transmission comprises at least one internal payload block and at least one internal parity block. The error correction capabilities of external code blocks can significantly reduce and tend to eliminate the loss of MBMS content or payload during transitions, such as when the UE moves from one cell to another cell, or when distributing content MBMS changes from a PTM connection to a PTP connection in the same server cell, and vice versa.

As noted above, a given cell can transmit to a subscriber 10 using either a PTP or PTM transmission scheme. For example, a cell that normally transmits a broadcast service in a PTM transmission mode may choose to establish a dedicated channel and transmit in a PTP mode (only for a certain

77/86 subscriber 10) if the demand within that cell for the service falls below a certain minimum value. Similarly, a cell that normally transmits content on a dedicated channel (PTP) to individual subscribers may decide to transmit the content to multiple users through a common channel. In addition, a given cell could transmit content in the PTP transmission mode while another cell could transmit the same content in a PTM transmission mode. A transition occurs when mobile station 10 moves from one cell to another, or when the number of subscribers within a cell changes, triggering a change in the transmission scheme from PTP to PTM, or vice versa.

During a Point-to-Multipoint (PTM) transmission from the external block η 95A, a transition occurs during transmission of the fourth internal block of the Broadcast Service and Multimedia Multicast (MBMS) payload. The slope of arrow 101, which illustrates the transition of User Equipment (UE) from a Point-to-Multipoint (PTM) transmission to a Point-to-Point (PTP) transmission, is non-horizontal since some time elapses during the transition. When a transition from PTM 101 to PTP occurs, the bit rate over the air remains approximately identical. Point-to-Point (PTP) transmissions typically have a bit error rate of less than 1% (for example, during transmission there is an error or less in every 100 payload blocks). In contrast, in Point-to-Multipoint (PTM) transmission a higher bit error rate can be assumed. For example, in one mode, the base station generates an external block once for every 16 transmission time intervals (TTI), and twelve of these TTI can be occupied by payload blocks and 4 TTI can be occupied by parity blocks . The number

The maximum block errors that can be tolerated should be 4 internal blocks out of 16 (12 fundamental blocks + 4 parity blocks). As such, the maximum tolerated block error rate would be 1/4.

When the mobile station transitions 101 from Point-to-Multipoint (PTM) transmission to Point-to-Point (PTP) transmission, some of the internal blocks may be lost. Assuming that Point-to-Multipoint (PTM) transmissions and Point-to-Point (PTP) transmissions have approximately the same bit rate in the physical layer (Ll), then PTP transmission will allow payload blocks MBMS are sent faster than PTM transmission, since, on average, the percentage of retransmitted blocks would typically be lower than the percentage of parity blocks. In other words, Point-to-Point (PTP) transmissions are typically faster than Point-to-Multipoint (PTM) transmissions since, statistically speaking, the number of parity blocks is much higher than the number of radio link control (RLC) retransmissions (Re-Tx). Due to the fact that transition 101 is from a Point-to-Multipoint (PTM) transmission to Point-to-Point (PTP) transmission which is typically faster, when User Equipment (UE) 10 transitions 101 to a Ponto-to-Ponto (PTP) transmission, the first Broadcast and Multimedia Multicast Service (MBMS) payload data block is being transmitted. As such, neither the time misalignment of the respective transmissions, nor the time that elapses during transition 101, causes any of the blocks to be lost. Therefore, when switching from Point-to-Multipoint (PTM) transmission to Point-to-Point (PTP) transmission, the missing payload block can be composed by simply restarting from the beginning of the block

79/86 current external when the PTP link has been established in the target cell. The network can compensate by starting the PTP transmission from the beginning of the same external block, that is, with the first internal block. The network can then recover the delay introduced by the transition due to the faster distribution of complete external blocks. Reducing data loss during transitions reduces disruptions in the distribution of MBMS content that can be caused by such transitions.

Subsequently, during the PTP transmission of the external block n + 2, the User Equipment (UE) 10 is subjected to another transition 103 to a Point-to-Multipoint (PTM) transmission mode. In Figure 12, this transition 103 from Point-to-Point (PTP) to Point-to-Multipoint (PTM) occurs in the last internal block of multimedia multicast and broadcast service payload (MBMS) of the external block n + 2 . At this station, many of the internal broadcast and multicast multimedia service payload blocks (MBMS) in the external block n + 2 have already been transmitted except for the last internal block. FEC is typically used in situations where feedback is not available. Due to the fact that PTP transmissions use a dedicated channel, and, therefore, it has feedback capability on the reverse link, the use of FEC is not beneficial. To minimize or eliminate data loss in cross transitions, the UMTS Terrestrial Radio Access Network (UTRAN) 20 relies preferably on the low residual block error rate of the confirmed RLC (AM) mode in the PTP transmission to recover all internal blocks that could be lost during a transition to PTM transmission. In other words, normal layer 2 retransmissions can be used to retransmit any packets in which error (s) are detected in the original transmission. That way, as

80/86 shown in Figure 17, parity blocks are not required for PTP transmissions. If errors are present in the payload blocks during a Point-to-Point (PTP) transmission, the external block may nevertheless be decoded because the Radio Link Control (RLC) layer will request retransmission of any erroneous blocks. That is, when there is an error during PTP transmission, mobile station 10 either requests retransmission (Re-Tx) or when all blocks are correct, no retransmission occurs and a zero transport format (TF0) can be used. External coding is preferably done in layer 2 of the protocol stack so that the size of each internal block 97 fits exactly in a Transmission Timing Interval (TTI) since this can optimize the coding efficiency.

If external error anticipation correction (FEC) coding is done on an upper layer of the protocol stack such as the application layer, then the parity blocks will be sent regardless of the transmission scheme (Point-to-Point (PTP) or Point-to-Multipoint (PTM)). As such, parity blocks would also be attached to Point-to-Point (PTP) transmissions.

As noted above, in PTP transmission the use of parity blocks is not necessary, since more efficient retransmission schemes can be used instead of Early Error Correction. Since parity blocks are preferably not transmitted in PTP transmission, the distribution of a complete external block can on average be faster than in PTM, assuming the same bit rate over the air. This allows the UE to compensate for interruptions caused by Point-to-Multipoint (PTM) to Point-to-Point (PTP) transitions, once

81/86 that PTP transmission can be anticipated with respect to PTM transmission. The User Equipment (UE) can retrieve the external block correctly by combining (1) internal blocks received in the Point-to-Point (PTP) transmission, either in the new cell or after transition, with (2) internal blocks received in the transmission Pontoa-Multipoint (PTM), either in the old cell or before the transition. User Equipment (UE) can combine internal blocks received before the transitions and internal blocks received after the transition that belong to the same external block. For example, User Equipment (UE) 10 can combine the internal broadcast and multicast multimedia service payload blocks (MBMS) in the external n + 2 block that are received via Point-to-Point (PTP) transmission ) with the internal broadcast and multicast multimedia service payload blocks (MBMS) in the external block n + 2 and parity blocks that are received through Point-to-Multipoint (PTM) transmission. The UMTS Terrestrial Access Radio Network (UTRAN) 20 can facilitate this process by slightly anticipating the transmission of external blocks for all users who receive MBMS content from PTP links with respect to transmission over PTM links.

Due to the fact that UTRAN anticipates the transmission of external blocks with respect to PTM transmission, seamless transitions from PTP to PTM are possible. As a result, the distribution of MBMS content across cell boundaries and / or between different transmission schemes such as PTM and PTP is also seamless. This anticipation of time can be expressed in the number of internal blocks. When User Equipment (UE) 10 transitions to a PTM transmission, even if a communication link does not exist during the

82/86 UE radio (RNC). In the UE 10 could transition, the User Equipment (UE) 10 can be deprived of time anticipation number of internal blocks without compromising the QoS of the MBMS reception. If the UE initiates MBMS reception directly in PTP, UTRAN could apply the time anticipation immediately at the start of PTP transmission since UTRAN 20 can slowly anticipate the transmission of external blocks by avoiding empty internal blocks (TF0), until the anticipation reaches the required number of internal blocks time anticipation. From that point on, the UTRAN can keep time anticipation constant.

In Pont.oa-Multipoint (PTM) the specific feedback information available on the Point-to-Point Transmission Network Controller (PTP) cannot be counted, inform the RNC about the number of the last external block received correctly before the transition . This should apply to any transition to PTP (from PTM or from PTP). If this feedback is not considered acceptable, UTRAN 20 can estimate the last external block that was received by User Equipment (UE) 10, most likely before the state transition. This estimate could be based on knowledge of the predicted maximum time imprecision between transmissions of different cells, and based on the external block currently being transmitted or that will soon be transmitted in the target cell.

Anticipated Error Correction (FEC) can be performed so that any blocks lost during the transition can be recovered. This results in a seamless transition by reducing the likelihood that content will be lost during a transition. This scheme assumes that the transition from Point-to-Point (PTP) to Point-to-Multipoint (PTM) transmission takes place while the

83/86 same external block is being transmitted from each source, which typically occurs given the duration of an external block with respect to the duration of a transition.

The amount of memory in the UE 10 can be negotiated with the exact time alignment of PTM transmissions through neighboring cells. By relaxing the memory requirement on the User Equipment (UE) 10, the time accuracy of the PTM transmissions of the UTRAN 20 can be increased.

Figure 18 is a diagram showing a temporal relationship between external code blocks received by a mobile station during a transition or reallocation between a Point-to-Point (PTP) transmission from the radio network controller (RNC) A and another Point-to-Point (PTP) transmission from the radio network controller (RNC) B. The term RNC can be used interchangeably with the term Base Station Controller (BSC). During a relocation, the User Equipment (UE) 10 transits from a Point-to-Point (PTP) transmission of a content stream in an area controlled by a first RNC A 124 for Point-to-Point transmission ( PTP) of the same content stream in an area controlled by a second RNC B 224. Retransmissions (re-Tx) can be used to compensate for any missing MBMS payload blocks. The direct transition from Point-to-Point (PTP) to Point-to-Point (PTP) between cells can be performed similarly to a soft handover or hard handover from Release '99. Although without coordination between the two RNC A, Β, the target RNC A, 124 must be able to calculate the most recent entire external block received by the UE 10. This estimate could be based on the timing of the MBMS content received by the RNC 24 on the interface Iu 25. When using PTP transmission, the RNC 24 can compose an initial delay, and no part of the MBMS content

84/86 will be lost even without requiring relocation of SRNS without loss.

Those skilled in the art will consider that although flow diagrams can be drawn in order, certain steps may be a current implementation.

sequential for understanding, performed in parallel in addition, unless otherwise indicated, the steps of the method can be interchanged without departing from the scope of the invention.

Those knowledgeable about information and signals can in the art understand that they can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be cited throughout the description above can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination of them.

Those skilled in the art will additionally consider that the various illustrative logic blocks, modules, circuits, and algorithm steps described in connection with the modalities implemented as computer hardware, or combinations of this clearly interchangeable hardware and software, various components, blocks, modules, circuits and illustrative steps have been described above generally in terms of their functionality. Whether such functionality can be implemented as hardware or software depends on the specific application and the design limitations imposed on the system as a whole. Those skilled in the art can implement the functionality described in a variety of ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the one described here can be electronic, software from both. To illustrate

85/86 scope of the present invention.

The various logic blocks, modules, and illustrative circuits described in connection with the modalities described here can be implemented or carried out with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate arrangement (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination of them designed to perform the functions described here. A general purpose processor can be a microprocessor, but as an alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the modalities described here can be incorporated directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium can be coupled to the processor in such a way that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium can be integral to the processor. The processor and media

86/86 storage can reside in an ASIC. The ASIC can reside on a user terminal. Alternatively, the processor and the storage medium can reside as discrete components in a user terminal.

The foregoing description of the described modalities is provided to allow anyone skilled in the art to make or use the present invention. Various modifications to these modalities will be easily evident to those skilled in the art, and the general principles defined herein can be applied to other modalities without departing from the spirit or scope of the invention. For example, although the description specifies that an access radio network 20 can be implemented using the aerial interface and Universal terrestrial radio access network (UTRAN), alternatively, in a GSM / GPRS system, access network 20 could be a network radio access GSM / EDGE (GERAN), or in the case of an intersystem it could comprise cells from a UTRAN air interface and cells from a GSM / EDGE air interface. Thus, the present invention should not be limited to the modalities shown here, but should be in accordance with the broader scope compatible with the new principles and characteristics described here.

Part of the description of this patent document contains material that is subject to copyright protection. The copyright holder has no objection to facsimile reproduction, by anyone, of the patent document, or patent description, as presented in the patent file or registration, of the Patent and Trademark Office, but, for on the other hand, it retains any and all copyrights.