Method and apparatus for transmission framing in a wireless communication system.

(54) Title: METHOD AND APPARATUS FOR FRAMING TRANSMISSION IN A WIRELESS COMMUNICATION SYSTEM.

(54) Title: METHOD AND APPARATUS FOR TRANSMISSION FRAMING IN A WIRELESS COMMUNICATION SYSTEM.

(57) Summary

Method and apparatus for framing a wireless transmission system that supports broadcast transmissions. A frame format incorporates specific fields for one-way transmission and reduces system overhead. One embodiment employs a version of HDLC that has a frame field start and an error checking mechanism attached to the load of each frame, where protocol information is not transmitted with each individual frame.

(57) Abstract

Method and apparatus for framing in a wireless transmission system supporting broadeast transmissions. A framing format incorporates fields specific to a unidirectional transmission and reduces the overhead of the system. One embodiment employs a version of HDLC having a start of frame field and an error checking mechanism attached to the payload of each frame, wherein protocol Information is not transmitted with each individual frame.

09/25/2003 21:59 ) ¿3^

4/47 (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATÍON TREATY (PCT) (19) World Intellectual Property Organized International Burean (43) International Publication Date

October 2002 (10.10.2002)

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PCT (10) International Publication Number WO 02/080488 A2 (SI) International Patent Classification⁷: H04L 29/00 (21) International Application Number: PCT / US02 / 09829 (22) Interna tional Filing Date: 28 March 2002 (28.03.2002) (25) Filing Language: English (26) Publication Language: English (30) Prlority Data:

60 / 279,970 28 March2001 (28.03.2001) US • 09 / 933,639 20 Augnst2001 (20.08.2001) US (71) Applicant: QUALCOMMINCORPORATED [US / US];

5775 Morehouse Drivc, San Diego, CA 92121-1714 (US).

gss (72) Inventor: HSU, Raymond, T .; 17775 Pennacook Comí, San Diego, CA 92127 (US).

(74) Agents: WADSWORTH, Philip, R. et al .; Qualcomm Incorporated, 5775 Morehouse Dñve, San Diego, CA 921211714 (US).

(81) Designated States (natíona!): AE, AG, AL, AM, AT, AU. AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CO, CR, CU, CZ, DE, DK, DM, DZ, EC, EB, ES, Η, OB, GD, GB, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NO, NZ, OM, PH, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TI, TM, TN, TR, ΤΓ, TZ, UA, UG, UZ, VN, YU, ΖΑ, ΖΜ, ZW.

(84) Designated States (regional); ARITO patent (GH, GM, KB, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZM, ZW), Eurasian patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM ), European patent (AT, BE, CH, CY, DE, DK, ES, H, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE, TR), OAPI patent (BF, BJ , CF, CG, CI. CM, GA, GN, GQ, GW, ML, MR, NE, SN, TD, TG).

[Continued on nezt page] (54) Title: METHOD AND APPARATUS TOR TRANSMISION FRAMINGIN A WIRELESS COMMUNICATION SYSTEM

WO 02/080488 A2 HllliMIlllH

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(57) Abstract: Method and apparatus for ñaming in a wirelcss transmission system supporting broadcast transmissions. A ñaming fonnat incorporates fields specific to a unidirectíonal transmission and reduces the overhead of the system. One embodiment employs a veision of HDLC having a stert of yam Geld and an error checking mechanism atlached to the payload of each yam, wherein protocol Information is not transmitted with each individual yam.

METHOD AND APPARATUS FOR FRAMING THE TRANSMISSION IN A

WIRELESS COMMUNICATION SYSTEM

FIELD OF THE INVENTION

The present invention relates to wireless communication systems, generally, and specifically, to methods and apparatuses for compressing messages in preparation for their transmission in a wireless communication system.

BACKGROUND OF THE INVENTION

There is a growing demand for packaged data services over wireless communication systems. Since traditional wireless communication systems are designed for voice communications, the extension to support data services introduces many challenges. Conserving bandwidth is the most overwhelming concern for most designers.

The transmission protocols and data preparation methods used for two-way communication may not be optimal for a one-way service, such as a broadcast service, where two-way communication requires information not used in one-way transmission. Therefore, there is a need for an efficient and accurate method for one-way transmission in a wireless communication system.

SUMMARY OF THE INVENTION

The modalities described here solve the needs stated above by providing a method for framing data packets in a data processing system.

In one aspect, a method of framing packets in a wireless transmission system that supports broadcast transmissions includes generating a portion of an Internet Protocol (IP) packet for transmission, appending a start-of-frame indicator to the portion of the broadcast packet. IP, apply an error checking mechanism on the IP packet portion, prepare a frame for transmission, which has the frame start indicator, the IP packet portion, and the error checking mechanism, and transmitting the table without protocol information.

In another aspect, a communication signal transmitted via a carrier wave, having a load portion corresponding to at least a portion of an Internet Protocol (IP) packet of digital information, a frame start portion corresponding to the portion upload, and identify a state of the upload portion within an IP packet, and an error checking portion to verify the upload portion.

In yet another aspect, a method of receiving framed packets in a wireless transmission system that supports broadcast transmission includes receiving a frame from a packet transmission, the frame having a frame start portion, a load portion, and a error checking, the box does not include protocol information, identify the box as an initial box in packet transmission, checking the frame using the error checking portion of the frame, and processing the loading portion of the frame.

In yet another aspect, a computer program stored in a computer-readable storage unit, the computer program for receiving packets framed in a wireless transmission system that supports broadcast transmission, the

20 'computer program includes a first set of instructions for receiving a frame from a packet transmission, the frame has a frame start portion, a load portion, and an error checking portion, the frame does not include information on protocol, a second set of instructions to identify the frame as an initial frame in packet transmission, a third set of instructions for checking the frame using the error checking portion in the frame, and a fourth set of instructions for processing the loading portion of the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of a spread spectrum communication system supporting a number of users.

Figure 2 is a block diagram of the communication system that supports broadcast transmissions.

Figure 3 is a model of the protocol stack for a broadcast service option in a wireless communication system.

Figure 4 is a table of the protocols applied to the layers of a protocol stack that support a broadcast service option in a wireless communication system.

Figure 5 is a flow chart for a message flow for broadcast service in a wireless communication system topology.

Figure 6 is a broadcast stream in a wireless communication system.

Figure 7 is a header compression map in a wireless communication system.

Figure 8 is a periodic broadcast or broadcast of header compression information.

Figure 9 is a header compression protocol.

Figure 10 is a header compression protocol for broadcast service in a wireless communication system.

Figure 11 is a flow diagram of header compression for broadcast service in a wireless communication system.

Figure 12 is a flow chart of header decompression for broadcast service in a wireless communication system.

Figures 13 and 14 are access networks that support broadcast transmissions.

Figures 15-17 illustrate a framing protocol.

DETAILED DESCRIPTION OF THE INVENTION

The word exemplary is used exclusively here with the meaning of serving as an example, case, or illustration. Any embodiment described herein as exemplary should not necessarily be construed as preferred or advantageous over other embodiments.

Optimization of a consistent broadcast service system is desirable in a wireless communication system to conserve a critical resource: available bandwidth. Efficient use of available bandwidth has an impact on system performance and range. Up to that point, various techniques have been applied to reduce the size of the overhead information transmitted along with the data or content information as well as to reduce the size of the transmitted data. For example, in a digital transmission, the data is transmitted in frames. The frames can be part of a data packet, part of a data message, or continuous frames in an information stream, such as audio and / or video streams. Attached to each data frame (and each packet or message) is a header containing processing information that enables the receiver to understand the information contained in the frames. This header information is considered aerial, that is, processing information transmitted together with information content. The information content is referred to as the load. Although each individual header is typically much smaller than a given payload, the cumulative effect of transmitting headers has impacts on available bandwidth.

An exemplary embodiment of a wireless communication system employs a framing method that reduces the size of the frame, while meeting the accuracy and transmission requirements of the system. The exemplary mode supports a one-way broadcast service. The broadcast service provides video and / or audio stream to multiple users. Subscribers of the broadcasting service tune into a designated channel to access the broadcast transmission. Since the bandwidth requirement for high speed transmission of video broadcasts is higher, it is desirable to reduce the size of any overhead associated with that broadcast transmission.

The following discussion develops the exemplary embodiment by first introducing, generally, a spread spectrum wireless communication system. Next, the broadcasting service is introduced; where the service is referred to as a High Speed ​​Broadcasting Service (HSBS), and the discussion includes channel assignments of the exemplary mode. A subscription model is then presented that includes options for paid subscriptions, free subscriptions, and hybrid subscription plans, similar to those currently available for television broadcasts. The broadcast access specificities are then detailed, presenting the use of a service option to define the specificities of a given transmission. The flow of messages in a broadcasting system is discussed with respect to the topology of the system, that is, the elements of the infrastructure. Finally, the header compression used in the exemplary mode is discussed.

Note that the exemplary mode is provided as exemplary throughout this discussion;

however, alternative embodiments may incorporate various aspects without departing from the scope of the present invention. Specifically, the present invention is applicable to a data processing system, a wireless communication system, a one-way broadcast system, and any other system that desires the efficient transmission of information.

Wireless Communication System

The exemplary modality employs a spread spectrum wireless communication system, which

- supports a broadcasting service. Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. Those systems can be based on code division multiple access (CDMA), time division multiple access (TDMA) techniques, or some other modulation techniques. A CDMA system provides certain advantages over other types of systems, including greater system capacity.

A system can be designed to support one or more standards such as a TIA / EIA / IS-95-B Mobile Station-Base Station Compatibility Standard for a Cellular Broadband Spread Spectrum System.

Dual Mode, referred to here as the IS-95 standard, the standard offered by a consortium called the 3rd Generation Partnership Project referred to here as 3GPP, and incorporated into a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213 and 3G TS 25.214, 3G TS 25.3 02, referred to here as the W-CDMA standard, the standard offered by a consortium called 3rd Generation Partnership Project 2 referred to here as 3GPP2, and TR-45.5 referred to herein as the cdma2000 standard, formerly called IS-2000 MC. The

I

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Standards cited hereinbefore are, therefore, expressly incorporated herein by reference.

Each standard specifically defines the data processing for transmission from base station to mobile, and vice versa. As an exemplary embodiment the following discussion considers a spread spectrum communication system consistent with the CDMA2000 protocol standard. Alternative modalities may incorporate another standard. Still other modalities can apply the compression methods described here to other types of data processing systems.

FIGURE 1 serves as an example of a communication system 100 that supports a number of users and is capable of implementing at least some aspects and embodiments of the invention. Any of a variety of algorithms and methods can be used to schedule transmissions in system 100. System 100 provides communication to a number of cells 102A through 102G, each of which is served by a corresponding base station 104A through 104G, respectively. . In the exemplary embodiment, some base stations 104 have multiple receive antennas and others have only one receive antenna. Similarly, some of the base stations 104 have multiple transmit antennas, and others have a single transmit antenna. There are no restrictions on the combinations of transmitting and receiving antennas. Therefore, it is possible that a base station

104 has multiple transmitting antennas and a single receiving antenna, or having a multiple receiving antenna and a single transmitting antenna, or having both single or multiple transmitting and receiving antennas.

Terminals 106 in the coverage area can be fixed (ie, stationary) or mobile. As shown in FIGURE 1, several terminals 106 are scattered throughout the system. Each terminal 106 communicates with at least one and possibly more base stations 104 on the downlink and uplink at any given time, depending on, for example, whether seamless handoff is employed or whether the terminal is designed and operated to receiving (concurrently or sequentially) multiple transmissions from multiple base stations. Unnoticeable handoff in CDNA communication systems is well known in the art and is. described in detail in US Patent No.

5,101,501, entitled Method and system to provide 25 an Imperceptible Transfer in a System of

CDMA Cellular Telephony, which was granted to the beneficiary of the present invention.

The downlink refers to the transmission from the base station to the terminal, and the uplink refers to the transmission from the terminal to the base station. In the exemplary embodiment, some of the terminals 106 have multiple receive antennas and others have only one receive antenna. In FIGURE 1, base station 104Ά transmits data to terminals 106A and 106J on the downlink, base station 104B transmits data to terminals 106B and 106J, base station 104C transmits data to terminal 106C, and so on.

The increased demand for wireless data transmission and the expansion of services available via wireless communication technology has led to the development of specific data services. One of those services is referred to as High Data Rate (HDR).

An exemplary HDR service is proposed in the EIA / YIA-IS856 cdma2000 High Speed ​​Packet Data Air Interconnection Specification referred to as the HDR specification. HDR service is generally an overlay to a voice communication system that provides an efficient method of transmitting data packets in a wireless communication system. As the amount of data transmitted and the number of transmissions increases, the limited bandwidth available for radio transmissions becomes a critical resource.

There is a need, therefore, for a good and efficient method of scheduling transmissions in a communication system that optimizes the use of available bandwidth. In the exemplary embodiment, the system 100 10 illustrated in FIGURE 1 is a system of the CDMA type having HDR service.

High Speed ​​Broadcasting System (HSBS)

A wireless communication system 200 is illustrated in FIGURE 2, where video and audio information is provided to the Packed Data Services Network (PDSN) 202. The video and audio information can be from televised programming or a broadcast of radio. The information is provided as packed data, as in IP packets. The PDSN 202 processes the IP packets for distribution within an Access Network (AN). As illustrated, AN is defined as the portions of the system, including a

BS 204 in communication with multiple MS 206. PDSN 202

- is coupled to BS 204. For HSBS service, BS 204 receives the information stream, from PDSN 202 and provides the information on a designated channel to subscribers within system 200.

In a given sector, there are several ways in which the HSBS broadcast service can be deployed. Factors involved in designing a system include, but are not limited to, the number of HSBS sessions supported, the number of frequency assignments, 10, and the number of physical broadcast channels supported.

HSBS is a flow of information provided over an overhead interconnection in a wireless communication system. The HSBS channel refers to a single logical HSBS broadcast session as defined by the broadcast content. Note that the content of a given HSBS channel may change over time, for example, the 7am News, the 8am Weather Report, the 9am, 8pm Movies etc. Time-based programming is analogous to a single TV channel. The 'Broadcast Channel' refers to a single physical channel of the forward link, that is, a given Walsh Code, which contains broadcast traffic. The Broadcasting Channel, BCH, 25 corresponds to a single CDM channel.

A single broadcast channel can contain one or more HSBS channels; in this case, the HSBS channels will be multiplexed in a Time Division Multiplexing (TDM) form within the single broadcast channel. In one embodiment, a single HSBS channel is provided over more than one broadcast channel within a sector. In another embodiment, a single HSBS channel is provided on different frequencies to serve subscribers on those frequencies.

According to the exemplary mode, the system

100 illustrated in FIGURE 1 supports a high speed multi-media broadcasting service referred to as High Speed ​​Broadcasting Service (HSBS). The service's broadcast capabilities are intended to provide programming at a data rate sufficient to support video and audio communications. As an example, HSBS applications can include video streams of movies, sports, etc. The HSBS service is an Internet Protocol (IP) -based packet data service.

According to the exemplary embodiment, a service provider is referred to as a Content Server (CS), where the CS announces the availability of that high speed broadcast service to the users of the system. Any user who wishes to receive the HSBS service can subscribe with the CS. The subscriber can then scan the broadcast service programming in a variety of ways that can be provided by the CS. For example, broadcast content may be communicated through advertisements, Shortcut Management System (SMS) messages, Wireless Application Protocol (WAP), and / or some other means generally consistent with and convenient for mobile wireless communications. .

Mobile users are referred to as Mobile Stations (MS). Base Stations (BS) transmit parameters related to HSBS in air messages, such as those transmitted on channels and / or frequencies designated for control and information, that is, messages without load. The load refers to the information content of the transmission, where for a broadcast session the load is the broadcast content, that is, the video program, etc. When a subscriber of the broadcast service wishes to receive a broadcast session, that is, a particular broadcast scheduled program, the MS reads the air messages and understands the appropriate settings. The MS then tunes to the frequency containing the HSBS channel, and receives the content from the broadcast service.

The channel structure of the exemplary mode is consistent with the cdma2000 standard, where the One Way Supplemental Channel (F-SCH) supports data transmissions. One modality groups a large number of Fundamental One Way Channels (F-FCH) or Dedicated One Way Control Channels (F-DCCH) to achieve the higher data rate requirements of data services. The exemplary mode uses an FSCH as the basis for the F-BSCH supporting a 64 10 kbps load (excluding RTP overhead). The F-BSCH can also be modified to support other upload speeds, for example by subdividing the 64 kbps upload speed into lower speed sub-streams.

One mode also supports group calls 15 in several different ways. For example, using the existing unidirectional transmission channel, that is, an unshared one-way link channel per MS, of the F-FCH (or the F-DCCH) or both round-trip links. In another example, the F-SCH (shared by the members of group 20 in the same sector) and the F-DCCH (not in frames, but the Power Control Subchannel -for most of the time) on the link of go and R-DCCH on the return link are applied. In yet another example, the high speed F-BSCH is used on the forward link 25 and the Access Channel (or the Enhanced Access Channel / Return Common Control Channel combination) on the return link.

Having a high data rate, the exemplary mode F-BSCH can use a very large portion of the forward link power of a base station to provide adequate coverage. The design of a physical layer for HSBC is thus focused on efficiency improvements in a broadcast environment.

To provide adequate support for video services, the system design considers the base station power required for various ways of transmitting the channel, as well as the corresponding video quality. One aspect of the design is a subjective trade-off between the perceived video quality at the coverage edge and the near-cell site. When the upload speed is reduced, the effective error correction code speed is increased, a given level of base station transmit power would provide better coverage at the edge of the cell.

For mobile stations located closer to the base stations, the channel reception remains error-free and the video quality would decrease due to the lower speed of resources. This same exchange also applies to applications other than video that the F-BSCH can support. The decrease in the upload speed supported by the channel increases the coverage at the expense of the decrease in the download speed for those applications. The balance of relative importance between video quality and amount of data against coverage is objective. The chosen configuration looks for an optimized configuration specific to the application, and a good compromise between all the possibilities.

The charging speed for the F-BSCH is an important design parameter. The following assumptions can be used in designing a system that supports broadcast transmissions according to the exemplary mode: (1) the target upload speed is 64 kbps, which provides an acceptable video quality for SKT; (2) for streaming video services, the upload rate is assumed to include 12 8-bit bytes per packet overhead of RTP packets; (3) the average overhead for all layers between RTP and the physical layer is approximately 64 bytes of 8 bits per packet plus 8 bits per F-SCH frame overhead used by MUXPDU header.

In the exemplary mode, for broadcast services other than video, the maximum supported speed is 64 kbps. However, they are also - - - - -,

V

- many other possible upload speeds reached below 64 kbps.

Subscription Model

There are several possible subscription / rental models for the HSBS service, including free access, controlled access, and partially controlled access. For free access, a subscription is not required to receive the service. The BS transmits the content without encryption or encryption and interested mobiles can receive the content. The income by the service provider can be generated through advertisements that can also be broadcast on the broadcast channel. For example, shorts of upcoming films may be broadcast for which studios will pay the service provider.

For controlled access, users of the

MS subscribe to the service and pay the corresponding fee to receive the broadcasting service. Non-subscribed users cannot receive HSBS service. Controlled access can be achieved by encrypting the HSBS stream / content, so that only subscribed users can decrypt the content. It may use encryption key exchange procedures or aerial encryption.

This scheme provides strong security and prevents service theft.

A hybrid access scheme, referred to as partial controlled access, provides the HSBS service as a subscription-based service that is encrypted with intermittent unencrypted ad transmissions. These advertisements may be intended to encourage subscribers to the encrypted HSBS service. The scheduling of those unencrypted segments could be made known to the MS through external means.

HSBS Service Option

The HSBS service option is defined by: (1) a protocol stack, (2) options in the protocol stack; and (3) procedures to establish and synchronize the service. The protocol stack according to the exemplary embodiment is illustrated in FIGURES 3 and 4. As illustrated in FIGURE 3, the protocol stack is specific to the infrastructure element, that is, the MS, BS, PDSN and CS in exemplary mode.

Continuing with FIGURE 3, for the MS application layer, the protocol specifies the audio code, visual code, as well as any visual profiles. Additionally, the protocol specifies the Radio Transport Protocol (RTP) payload types when RTP is used. For the MS transport layer, the protocol specifies a User Datagram Protocol (UDP) port. The security layer of the MS is specified by the protocol, where 5 security parameters are provided via out-of-band channels when security is initially associated with the CS. The network layer specifies the compression parameters of the IP header.

Message Flow

FIGURE 5 illustrates the exemplary mode call flow for a given system topology. The system includes an MS, BS, PDSN, and CS, as listed on the horizontal axis. The vertical axis represents time. The user or the MS is a subscriber of the HSBS service. At the same time the MS and the CS negotiate the security of the subscription for the broadcast service. The negotiation involves exchange and maintenance of encryption keys, etc., used to receive the broadcast content on the broadcast channel. The user establishes a security association with the CS upon receipt of the encryption information. The encryption information may include a Broadcast Access Key (BAK) or a combination of keys, etc., from the CS. According to the exemplary embodiment, the CS provides the encryption information on a dedicated channel during a transfer of packet data, such as via PPP, WAP, or other out-of-band methods.

At time t2 the MS tunes to the broadcast channel and begins to receive packets. At this point in time, the MS is unable to process the received packets because the IP / ESP header is compressed via ROHC, and the MS decompressor has not been initialized. The PDSN provides header compression information (detailed hereinafter) at time t3. From the header of the ROHC packet, the MS detects and obtains a ROHC Initialization and Renewal (IR) packet periodically sent from the PDSN to the broadcast channel. The ROHC IR packet is used to initialize the decompressor state in the MS, allowing the MS to decompress the IP / ESP header of the received packets. The MS can then process the IP / ESP header of the received packets, however the MS requires additional information to process the ESP payload since the payload is encoded with a Short Term Key (SK) in the CS. The SK acts in coordination with the BAK where the SK is decrypted at the receiver using the BAK. The CS provides additional encryption information, such as' updated key information or a current SK at time t4. Note that the CS provides this information periodically to the MS to ensure the security of the course of the broadcast. At time t5 the MS receives the broadcast content from the CS. Note that the 5 alternative modes can incorporate alternative compression and decompression methods that provide efficient transmission of header information. Additionally, alternative modalities may implement a variety of security schemes 10 to protect broadcast content. Alternative modalities can still provide an insecure broadcasting service. The MS uses the encryption information, such as the SK, to decrypt and present the broadcast content.

Compression

According to the exemplary mode, the broadcast content is transmitted on a dedicated broadcast channel. Transport layer 20 provides encryption overhead to transport broadcast content in IP packets. The system supports data compression, and header compression specifically. The decision to compress data depends on the average throughput required 25 (including transport / encryption overhead, data link layer overhead, and physical layer overhead) and the user's perception of the quality of the broadcast. Carrying more broadcast content in each IP packet reduces overhead 5 and thus reduces the bandwidth of the broadcast channel. In contrast, compression increases the Percentage of Packet Errors (PER) that affects user perception. This is due to the transmission of each long IP packet spanning multiple physical layer 10 frames and this is associated with increases in Frame Error Percentage (FER). If a bearer decides to use a small IP packet to improve broadcast quality, the bearer may choose header compression to reduce the transport and encryption overhead of the IP packet.

The RTP / UDP / IP protocols are used to transport broadcast content from the CS to the MS, and the content is protected by the Encapsulation Security Payload (ESP) in the transport mode. The 20th transport overhead is the RTP / UDP / IP header and is 40 bytes per IP packet data. The encryption overhead is in the form of ESP header, Initialization Vector (IV), and ESP tail. The ESP and IV header are inserted between the IP header and the UDP header. The ESP header consists of the

Security Parameter Index (SPI) (4 bytes) and Sequence Number (4 bytes). The length of the IV is specific to the encryption algorithm that is used. For the AES Cipher Algorithm, the length of the IV is 5 16 bytes. The ESP tail is appended to the end of the UDP datagram and consists of the padding, then the header (1 byte), and the padding length (1 byte). Since the size of the cipher block of the AES algorithm is 16 bytes, the size of padding 10 ranges from 0 to 15 bytes. Taking the maximum function of the average padding size yields 8 bytes. For an IP packet the total overhead due to transport and encryption fluctuates from 66 to 81 bytes with the average of 74 bytes not including the PDSN to MS data link layer overhead.

Header compression such as Robust Header Compression (ROHC) can be used to reduce the IP header and the SPI field of the ESP Header from 24 bytes to 2 bytes. The Sequence Number of the 20 ESP Header is not compressed, because it is used to sequence compressed packets. The IV is not compressed, as it changes randomly for each packet. The UDP / RTP header and ESP queue cannot be compressed because they are encrypted.

Therefore, if the ROHC is used to compress the IP / ESP header, the average overhead due to transport and encryption is reduced from 74 bytes to 52 bytes per IP packet.

According to the exemplary mode, header compression, such as Robust Header Compression (ROHC), is applied to avoid propagating decompression errors. As illustrated in FIGURE 7, the header information is compressed from bytes to 2 bytes. The header 500 includes an IP header 5 02 and an SPI portion 504. The compression algorithm results in 2 bytes after compression. In contrast to conventional header compression, where some type of negotiation is required between the MS and the PDSN and another infrastructure element, the exemplary mode provides a one-way transmission of the compression information. The MS does not need to request the compression information, that is, sufficient header compression parameters for decompression of the information received at the MS. Rather, the PDSN provides the compression information periodically as illustrated in FIGURE 8. The PDSN provides the compression information about the broadcast channel interspersed with the broadcast content. The provision of control information within a data stream is referred to as in-band since no separate channel is required. As illustrated, the broadcast stream 600 includes portions of the broadcast content 604 and the decompression information, ie, compression information, 602. The decompression information is provided by having a period of Tdecompression - Alternative modes may provide the information. decompression after the occurrence of a predetermined event instead of periodically. Since the MS does not request the decompression information, the PDSN provides the information at a frequency that avoids delays in accessing the broadcast content. In other words, the PDSN would provide the information frequently, so that an MS can access the broadcast at any time without having to wait for the decompression information.

Note that the ROHC can be operated in a unidirectional mode, where packets are sent in only one direction: from compressor to decompressor. Thus, therefore, ROHC becomes useful over links where a return path from decompressor to compressor is not available or is undesirable. Before the MS can decompress the packets received from the broadcast channel, the decompressor state is initialized. The Initialization and Renewal Package

- (IR) is used for this purpose. There are two alternatives for ROHC initialization.

The subscriber tunes to the broadcast channel and waits for the ROHC IR packets sent periodically by the ROHC compressor on the PDSN. Frequent ROHC IR packets may be required for the MS to start decompressing the received packets quickly. Frequent ROHC IR packets can use too much bandwidth on the broadcast channel. An IR packet is approximately 30 bytes for the IP / ESP compression profile. If an IR packet is sent once every 250 ms, the process consumes approximately 1 kbps on the broadcast channel. Loss of IR packets over the air would further delay the MS acquisition from ROHC initialization.

If decompression becomes out of sync, due to packet losses, or residual errors in the received compressed header, or failures, etc., the resulting decompression error 20 can propagate until decompression is resynchronized or reinitialized. A ROHC compressed header contains a Cyclic Redundant Check (CRC), which is calculated on the entire header before compression. This CRC allows decompression to perform a local context repair leading to the context in synchronization (in packet loss and residual error events). When decompression recovers from a failure, periodic IR packets effectively reinitialize the decompression process.

Data link layer

A data link layer framing protocol or transport layer protocol is applied between the PDSN and the MS to delineate the packets received from the broadcast channel. With reference to FIGURE 3, the information in the transport layer, identified as BINDING LAYER, is provided between the PDSN and the MS. The framing information is generated at the PDSN and is provided to the MS via the BS. The PDSN receives IP streams from the CS and squares the IP streams according to a predetermined framing protocol. As illustrated in the exemplary embodiment, the PDSN applies a framing protocol version of High Speed ​​Data Link Control (HDLC). The HDLC specified in the ISO standard corresponds to Layer 2 of the 7-layer architecture of the International Standards Organization (ISO), where Layer 2 is referred to as the Data Link Layer. The HDLC protocol seeks to provide error-free movement of data between network nodes. Up to this point, the HDLC layer is designed to ensure the integrity of the data passed to a next layer. In other words, the framing protocol seeks to reproduce the received data exactly as the data was originally transmitted, without errors, without loss of information, and in the correct order.

The exemplary mode applies a framing version of HDLC that applies a subset of the defined HDLC parameters. FIGURE 9 illustrates an HDLC framing mode, where frame 700 includes a plurality of fields as defined by the HDLC protocol disclosed in RFC 1662. Field 702 defines an INDICATOR or indication of a beginning of frame. The FLAG has a designated bit length and is defined by a predetermined bit pattern. HDLC is convenient to apply since HDLC is a commonly available standardized protocol. A disadvantage of the full HDLC framing protocol is the processing time required to generate the frames at the transmitter and to retrieve the frames at the receiver.

In particular, the HDLC protocol is considered processor intensive since additional processing is used to ensure that the payload does not include the same bit sequence as the FLAG. At the transmitter, if a sequence of FLAG bits is detected on the load, an escape character is inserted on the load to identify the FLAG as part of the load and not indicate a frame start. The process of adding an escape character is referred to as hexadecimal escape patterns of 0x7E and 0x7D in the frame load. An alternative method, referred to as the Protocol, Efficient Framing which is less processor intensive than HDLC-like framing is described later. FIGURE 9 illustrates the options of using HDLC framing to transport PPP frames. For HSBS operation, HDLC-like framing overhead can be reduced by eliminating fields that are not required, or have little meaning and / or provide little information, for unidirectional broadcasting. As described here above, the FLAG is a predetermined sequence of bits that indicates the start of an HDLC frame. The exemplary embodiment incorporates an INDICATOR or other beginning of frame indicator 802, as illustrated within the 800 format of FIGURE 10. In contrast to the format of FIGURE 9, the end of a frame is not indicated with overhead information in exemplary mode.

Since the address and control fields of the format

700 they have static values, those are not included in the 800 format.

Continuing with FIGURE 10, since the purpose of the Protocol field 708 (FIGURE 9) is to identify the type of payload, such as LCP control packet, ROHC packet, IP packet, etc., this discriminator is not required for broadcast operation since all packets on the broadcast channel belong to the same type. For example, if ROHC compression is used for packet transmission, all packets on the broadcast channel are processed as ROHC packets. ROHC packet types, such as IR packets, compressed packets, etc., are distinguished by the Packet Type field in the ROHC packet header. Therefore, the Protocol field is not included in the 800 format. Also, the 800 format includes an error check field 806 after loading 804. The error checking field 806 provides information to the receiver to allow the receiver to check for errors in the received payload. The exemplary mode incorporates a Frame Checksum (FCS) which can be specified as null, 16 bits, or 32 bits. Since one HDLC frame can span multiple physical layer frames on the broadcast channel, it is recommended to use 16-bit FCS.

The octet packing procedure defined in RFC 1662 is also applied to the exemplary mode, where after the FCS calculation, the HDLC transmitter in the PDSN examines each byte in the HDLC table (excluding the Flag) for the parameters of 0x7E and 0x7D. Pattern 0x7E will be encoded as 0x7D and 0x5E, and pattern 0x7D will be encoded as 0x7D and 0x5D. The HDLC transmitter will not encode any other patterns. This implies that any Asynchronous Control Character Map (ACCM) as defined in RFC 1662 is all set to zero.

The HDLC framing overhead is 3 bytes plus the octet packing overhead. Assuming the byte pattern is evenly distributed, the average byte packing overhead is one byte per 12 8 bytes of the HDLC frame. For example, if the payload is 256 bytes, the HDLC framing overhead is 5 bytes on average.

FIGURE 11 is a flow chart of a framing method 900 performed at the transmitter. The transmitter forms a broadcast box in step

902 determining a load portion of the packed data and generating the Start of Indicator (SOF).

The transmitter then checks the frame for any SOF sequences contained in the load 904. If an SOF sequence is found in the load, the transmitter adds an escape character in step 912. Also, the transmitter appends the SOF to the load. loads in step 906 and provides an error checking mechanism in step 908. The frame is transmitted in step 910. The transmitted frame has the format 800 of FIGURE 10. Alternative modalities may implement other fields 10 within the framing format and may incorporate any form of classifier to locate a sequence of SOFs in the payload.

FIGURE 12 is a flow chart of an out-of-frame method 920 performed at the receiver. The process begins upon receipt of a broadcast frame at step 922. The receiver identifies an SOF at step 924, and checks the escape characters in the decision diamond load 926. If an escape character is found, or other SOF sequence identifier, on upload, the receiver separates the escape character at step 932. Also, the receiver performs an error check at step 928 and processes the frame at step 930.

An alternative modality incorporates a framing protocol that does not use a framing similar to the one

Byte-based HDLC seeking to avoid processor intensive operations which use byte padding (referred to as escape). Instead, this alternative uses a packet-based framing layer 5 which is less processor intensive and is referred to here as the efficient framing protocol. FIGURE 15 illustrates the process and protocol 2000 for the formation of a 2016 framing layer packet from IP 2002 layer packets, integrity layer 10 packets, and packaging layer packets.

The framing layer processes 2000 variable length packets received from an upper layer such as the IP layer into 2016 fixed length packets and passes the packets from the resulting 2016 framing layer to the lower 15 layer, i.e. the layer physical (not shown). The framing layer allows the receiver to determine the upper layer packet boundaries and validate the integrity of the upper layer packet.

As illustrated, process 2000 includes several processing sublayers, including an integrity layer and a packaging layer. The integrity layer forms a load portion of the integrity layer 2006 packet of the IP layer 2002 and appends a queue 2008. In one embodiment, the load portion of the integrity layer 2006 includes the packet of the cap

I

- from IP 2002; however, alternative modes may include a portion of the IP layer 2002 packet or multiple IP layer 2002 packets, or any combination thereof. Queue 2008 can be an integrity check mechanism.

The integrity layer appends an integrity verification field or queue 2008 to each packet of the IP layer 2002, that is, the packets received from the upper layer, which in this case is the IP layer. The integrity layer 10 then passes the packets from the resulting integrity layer 2006, 2008 to a lower layer, which in this case is the packaging layer. The packets are further processed to form the frame layer 2 016 packets and are transmitted via the physical layer. At the receiver, packets are received via the physical layer and provided to the higher layers. The integrity layer at the receiver processes the integrity check mechanism, ie the queue, and thus enables the receiver to validate the integrity of packets received from the lower layer before passing them to the upper layer. The integrity layer format is illustrated in FIGURE 16, discussed below. .

Continuing with FIGURE 15, the integrity layer passes the integrity layer packets

2006, 2008, to the packaging layer to form packaging of the packaging layer. The packing layer forms a packet that has at least one packing header, or 2010 packet header, at least one packing payload, or 2012 packet payload, and a 2014 padding. The illustrated embodiment includes multiple packet loads 2012, each of which has associated packet header 2010. Alternate modes can incorporate any number of 2012 packet payloads and 2010 packet headers. From the packaging layer, the 2000 processing then generates a 2016 framing layer packet to feed to the physical layer (not shown).

The packing layer packages variable length packets received from the upper layer (e.g., the integrity layer) into fixed-length packing layer packets 2016 and passes the resulting packing layer packets 2016 to a lower layer ( for example the physical layer). The packing layer allows reception to determine the packet boundaries of the upper layer.

FIGURE 16 illustrates the integrity layer packet 2050 format (packet 2006, 2008 of FIGURE 15). As illustrated, the 2050 format includes two portions: the 2052 load field and the

Frame Check Sequence (FCS) 2054. Payload portion 2052 is a variable-length field containing the octets of exactly one upper layer packet. The FCS portion 2056 is a 32-bit field 5 that contains the FCS for the upload. The FCS is a 32-bit CRC calculated on the load field. Alternative modalities may implement other error checking mechanisms.

FIGURE 17 illustrates the 2060 format of a packaging layer packet according to one embodiment. The 2060 format, four fields: continue, length, load and fill. The continue field 2062 and the length field 2064 constitute a header portion. The continue field 2062 is a 15-bit field that indicates whether a corresponding payload field 2066 is the start or continuation of an upper layer packet. Alternative modes may increment any number of bits that have meaning with respect to the charge field 2066. In the embodiment 20 illustrated in FIGURE 17, when the continue field is set, the corresponding charge field is a continuation of a packet of the top layer. Otherwise, the post charge field is the start of a top layer pack. In this way, each of 25 packet payloads 2012 (FIGURE 15) can include a full IP layer packet 2002 (or integrity layer payload 2006), a portion of a packet from IP layer 2006, packets Multiple IP Layer 2002. According to an alternative embodiment, the continue field 2062 is not included in the packet layer 2060 format, where if a packet from the previous framing layer is discarded before reaching the receiver's framing layer, the receiver You can use integrity layer processing to determine the start or continuation state of an integrity layer packet. That mode, however, places an additional processing load on the integrity layer and expands the integrity check processing. Note also that in one embodiment the continue field 2062 is single bit, where the meaning of the bit corresponds to the polarity of the bit. Alternate modes may have alternate polarity, or as stated above, may implement a combination of bits to provide additional information, such as sequence number, etc.

Continuing with FIGURE 17, the header portion further includes a field of length 2064. In one embodiment, the length field 2064 is the 15-bit field that indicates the number of octets in the first octet 25 in the corresponding payload field 2066 down to the last octet in the upper layer packet contained in the post-payload field. The payload field 2066 is a variable length field that contains bytes from a single packet from the integrity layer 2006, 2008 (FIGURE 5 15). The number of octets in payload field 2066 is the length of the octets or the number of octets from the start of the payload field 2006 to the end of the packet layer 2016 packet, whichever is less. The padding field 2068 is a variable length field containing enough bits to keep the layer size of the packing packet 2016 at the size of the lower layer payload supported by the physical layer. The constitution of the padding field 2068 reflects a predetermined recognizable pattern, such as all 15 octets of zero, and so on. The transmitter fills the fill field 2068, which is received and ignored or discarded by the receiver.

Access Network

A general access network topology for a system 1000 is illustrated in FIGURE 13 having a CS 1002, a PDSN 1004, and two PCFs: PCF1 1006 and PCF2 1008. FIGURE 13 includes datagrams specifying the transmissions of each of the ' Infrastructure elements illustrated in system 1000. As illustrated, CS 1002 prepares an information IP packet and transmits the packet in at least one frame, having a payload and an inner header, H1. The inner header has source and destination information, 5 where the source identifies CS 1002 and the destination identifies a subscription group. CS 1002 transmits the frame to PDSN 1004, which maps the target subscription group to individual subscribers in a set of active users.

PDSN 1004 determines the number of individual users in the active set that are in the target subscription group and duplicates the frame received from CS 10 02 by each of those users. PDSN 1004 determines the PCFs for each of the users in the subscription group. PDSN 1004 then appends an outer header, H2 to each of the prepared frames, where H2 identifies a PCF. The PDSN 1004 then transmits the frames to the PCFs. The transmission of the PDSN 1004 includes the original payload, the Hl header, and the H2 header. As illustrated, PDSN 1004 sends N transmission frames to PCF1 1006 and sends M transmission frames to PCF2 1008. The N transmission frames correspond to N users in the subscription group served via PCF1 1006 and the M transmission frames correspond to M users in the subscription group served via PCF2 1008. In this scenario, the PDSN 1004 duplicates the received frames any number of times for transmission to the corresponding subscribers.

FIGURE 14 illustrates an exemplary embodiment of a system 1020 having a CS 1022 that communicates with PCF1 1026 and PCF2 1028 via PDSN 1024. As illustrated, CS 1022 prepares an IP packet of information and transmits the packet. in at least one frame, which has a payload and an internal header, Hl. The inner header has source and destination information, where the source identifies the CS 1022 and the destination identifies a subscription group. CS 1022 transmits the frame to PDSN 1024, where PDSN 1024 appends an outer header H2, where H2 routes the frame to at least one PCF. The PDSN 1024 then transmits the frames to the PCFs. The PDSN 1024 transmission includes the original payload, the Hl header, and the H2 header. As illustrated, the PDSN 1024 sends a transmit frame to the

PCF1 1026 and sends a broadcast frame to PCF2 1028. PCF1 1026 sends a broadcast frame to the N users in the subscription group. The PCF2 1028 sends a broadcast frame to the M users in the group. subscription.

In accordance with an exemplary embodiment, the broadcast CS sends IP packets containing encrypted broadcast content to a broadcast group identified by a class D multi-broadcast IP address. This address is used in the broadcast address field. destination of IP packets. A given PDSN 1024 participates in the multi-broadcast routing of those packets. After header compression, the PDSN 1024 places each packet in an HDLC frame for transmission. The HDLC frame is encapsulated by a Generic Routing Encapsulation (GRE) packet. The GRE packet header key field uses a special value to indicate a broadcast bearer connection. The GRE packet is appended with the 20-byte IP packet header that has a source address field that identifies the IP address of the PDSN 1024, and the destination address field uses a multi-broadcast IP address. of class D. It is recommended that this multi-broadcast IP address be different from the one used by the broadcast CS. System 1020 configures at least one multi-broadcast routing table of the respective PCFs and PDSNs. The packets delivered to the broadcast connection 25 are provided in sequence; in exemplary mode, a GRE sequencing feature is allowed. Duplication of IP multicast packets is done on routers capable of multicasting.

In an exemplary embodiment, each PCF is further coupled to a BSC (not shown), where a BSC can duplicate the packets and send them to another BSC. BSC chaining produces imperceptible better transfer performance. BSC anchor produces better imperceptible transfer performance. The BSC anchor duplicates the transmission frame and sends it with the same stamped time to its adjacent BSCs. The time stamp information is critical for the seamless handover operation when the mobile station receives transmission frames from different

BSC.

Those skilled in the art will understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, the data, instructions, orders, information, signals, bits, symbols and elementary units of information that can be referred to through the previous description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields. or particles, or any combination thereof.

Those of skill will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in connection with the embodiments described herein can be implemented as electronic components, computer programs and programming systems, or combinations of both. To clearly illustrate this interchangeability of computer hardware and programming systems and programs, various illustrative components, blocks, modules, circuits, and steps have been generally described above in terms of their functionality. Whether that functionality is implemented as physical components of computing or programming programs and systems depends on the particular application and design constraints imposed on the entire system. Experts can implement the described functionality in various ways for each particular application, but those implementation decisions should not be construed as departing from the scope of the present invention.

The various illustrative logic blocks, modules, and circuits described in connection with the embodiments described herein can be implemented or implemented with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware, or any combination thereof designed to perform the functions described here. A general purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine or engine. 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 of those configurations.

The steps of a method or algorithm described in relation to the modalities described herein can be incorporated directly into physical computing components, into a module of programs and programming systems executed by a processor, or in a combination of the two. A program module and programming system can reside in RAM, buffer, ROM, EPROM, EEPROM, registers, hard disk, removable disk, CD-ROM, or any other known form of storage medium. in technique. An exemplary storage medium is coupled to the processor, since the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium can be integrated into the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal.

Alternatively, the processor and storage medium can reside as discrete components in a user terminal.

The foregoing description of the described embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications of those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but in accordance with the broadest scope consistent with the principles and novel features described herein.