Uplink scrambling during random access

TECHNICAL FIELD [0001] The subject field of technology relates to mobile radio communication, and in particular to uplink communication in which mobile radio terminals participate in a mobile radio communication system,

BACKGROUND ART [0002] The UMTS system (Universai Mobile Telecommunications System) is a third generation (3G) asynchronous mobile communication system that uses the Wideband Coda Division Multiple Access (WCDMA) technology based on European systems GSM (Global System for Mobile Communications) and GPRS (General Packet Radio Services). LTE variety (ang. Long Term Evolution) of the UMTS system is developed by the 3rd Generation Partnership Project (3GPP), which standardized the UMTS system. There are many technical specifications posted on the 3GPP website that relate to E-UTRA (Evolved Universal Terrestria! Radio Access) and E-UTRAN (Evolved Universal Terrestrial Radio Access NetWork), e.g. 3GPP TS 36.300. The purpose of the LTE system is to develop a benchmark for the evolution of 3GPP radio access technology towards packet-optimized radio access technology with high data rates and low latency. In particular, LTE technology is designed to support services provided from a packet switched domain (PS). The key goal of 3GPP LTE technology is to enable high speed packet communication at or above 100 Mbps.

[0003] Fig. 1 illustrates an example of a LTE 10 mobile communication system. The E-UTRAN network 12 includes EUTRAN NodeB nodes (eNodeB or eNB) 18 that provide radio termination of the user plane and the E-UTRA control plane for user devices (UE, user euuipment) 20. Although the eNB is a logical node, often, but not necessarily, implemented as a physical base station, the term base station is generally used here for both logical and physical nodes. The UE is sometimes called a mobile radio terminal, while in the inactive state it monitors system information broadcast within its range by eNB nodes, giving information about available base stations in the service area. When the UE needs access to services from the radio access network, it sends a request through a RACH (random access channei) channel to the appropriate eNB node, usually to the eNB node with the most favorable radio conditions. ENB nodes are connected to each other via the X2 interface. The eNB nodes are also connected via the S1 interface with the EPC (Evolved Packet Core) 14 system, which includes the Mobility Management Entity (MME) module, the S1-MME interface, as well as with the SAE (System) gateway Architecture Evolution Gateway), S1-U interface. The MME module / SAE gateway is in this example a single module 22. The S1 interface supports a many-to-many relationship between

- 2 MME modules / SAE gates and eNB nodes. The E-UTRAN 12 network and the EPC 14 system together form the Public Land Mobile NetWork (PLMN). The MME modules / SAE 22 gateways are connected directly or indirectly to the internet 16 network and other networks.

[0004] To enable operation at various spectrum allocations, e.g. for smooth migration from existing cellular systems to a new system with high capacity and high data rate in the existing radio spectrum, it is necessary to be able to work with adapted bandwidth, e.g. bandwidths of from 1.25 MHz to 20 MHz for downlink transmission from the network to the UE. Both high-speed services and low-speed services, e.g. voice services, must be supported, and because 3G LTE is provided for the TCP / IP protocol, it is likely that the gios forwarding service will be implemented in VolP technology.

[0005] LTE uplink transmission is based on the so-called DFTS-OFDM modulated transmission Discrete Fourier Transform Spread-OFDM), a single-carrier transmission scheme (SC) with a low peak to average power ratio (PAPR) that allows flexible bandwidth allocation and orthogonal multi-access not only in the time domain, but also in the frequency domain. Therefore, the LTE uplink transmission scheme is often called the SC-FDMA (Single-Carrier FDMA) scheme.

[0006] The LTE uplink transport channel processing is outlined in Fig. 2. The dynamic size transport block is provided from the media access control (MAC) layer. The CRC (cyclic redundancy codec) checksum is calculated and attached to this block for use in the base station receiver for error detection. Then, uplink channel coding is performed by a channel coder that can use any suitable technique. In LTE technology, the code may be a turbo-code that contains an internal interleaver based on QPP (Ouadratic Permutation Polynomial) to perform block interleaving as part of a turbocoder. The hybrid automatic repetition request (ARQ) technique Automatic Repeat Request) in the uplink in LTE technology takes from the block of coded bits, provided by the channel encoder, the correct set of bits to be sent at any time of transmission / retransmission. The scrambler will scramble these encoded bits on the LTE uplink (e.g., scrambling at the bit level) to randomize interference, and thus ensure that the processing gain provided by the channel code can be fully utilized.

[0007] To achieve this randomization of interference, uplink scrambling depends on the terminal, i.e. different mobile terminals (UEs) use different scrambling sequences. Terminal-dependent boring also gives the scheduler the freedom to schedule a number of users in the same time-frequency resources and to rely on the base station receiver to process transmission from a number of users. Terminal-dependent scrambling randomizes interference from other mobif terminals in the same cell that have been ranked in the same resources, and increases performance.

[0008] After scrambling, data is modulated to transform a block of coded / scramble bits into a block of complex modulation symbols. In the LTE uplink example, the set of supported modulation schemes include QPSK, 16QAM and 64QAM, which corresponds to two, four and six bits respectively

-3 modulation symbol. The block of modulation symbols is then forwarded to the DFTS-OFDM modulator, which also assigns the signal to the assigned radio resources, e.g. to a frequency subband.

[0009] Along with the modulated data symbols, the signal associated with the assigned frequency band also includes demodulation reference signals. Reference signals known in advance by both the mobile terminal (UE) and the base station (eNodeB) are used by the receiver to estimate the channel and demodulate the data symbols. A user terminal may be assigned different reference signals for similar reasons, for which terminal-dependent scrambling codes can be used, i.e. for the intelligent scheduling of a number of users in the same time-frequency resources, and thus the implementation of so-called multi-user MIMO scheme. In the case of a multi-user MIMO scheme, processing by the eNodeB is responsible for separating signals transmitted from two (or more) UEs arranged simultaneously on the same frequency resources in the same cell. Terminals arranged simultaneously on the same frequency resources are usually assigned different (e.g. orthogonal) reference signal sequences for the eNodeB node's estimation of radio channels for each of these UEs.

[0010] A basic requirement for any cellular or other radio communication system is to provide the user terminal with the ability to request the establishment of a connection. This capability is commonly known as free access and serves two main purposes in LTE technology, namely obtaining uplink synchronization with the countdown by the base station and acquiring the terminal's unique identity, e.g. temporary identifier in the cell radio network temporary identifier (C-RNTI) in the LTE system, known to both the network and the user terminal, which is used in communication to distinguish that user's communication from other communication.

[0011] However, during the (preliminary) random access procedure, uplink transmissions from the user terminal may not use scrambling sequences or terminal dependent reference values ​​to randomize because the initial random access request message from the user terminal is only just beginning to communicate with the network and thus no user terminal has been assigned a terminal-dependent scrambling code, or terminal-dependent reference value. A mechanism is needed that allows the scrambling of random access messages sent over the uplink shared channel until the terminal-dependent scrambling code can be assigned to this user terminal. One of the reasons for scrambling random access messages is the randomization of intercell interference, which also applies to scrambling during "normal" data transmission over an uplink. In the latter case, scrambling can also be used to suppress intracellular interference when a number of UEs are scheduled on the same time-frequency resources). Similarly, it would also be desirable to be able to cause user terminals to transmit known reference signals during random access to allow the base station receiver to estimate an uplink channel. Reference signals must be attached to random access messages as well as to "normal" uplink data transmissions to enable channel estimation at the eNodeB node and appropriate

-4 coherent demodulation.

[0012] Document EP0565507 A2 describes a mobile station comprising means for selecting, from a list of available scrambling codes broadcast from another radio station, a scrambling code to generate a random access message, see p. 3, vv. 30-32.

SUMMARY OF THE INVENTION [0013] The technology described below allows the user terminal to freely access the radio base station. Among others this advantage is obtained in accordance with one aspect of the present disclosure using a method for a user terminal according to claim 1. 1 and the wedfug user terminal of claim 6, as well as a method for a base station according to claim And a base station according to claim 10.

The user terminal designates one of the first type uplink scrambling sequences and generates a random access message using the first type of uplink scrambling sequences. Its transmitter transmits this message to free access to the radio base station. Then the user terminal receiver receives from this base station the uplink scrambling sequence of the second type. The terminal uses this uplink scrambling sequence of the second type in further communication with this radio base station. In one non-limiting embodiment of the invention, the first type uplink scrambling sequences may be specifically associated with the cell area of ​​this radio base station or random access radio channel associated with this radio base station, but are not specifically assigned to any of the user terminals, and the sequence scrambling up links of a second, different type can be selected from a second set of scrambling up links sequences, assigned to individual user terminals. The use of these two different types of scrambling sequences allows user terminals to scramble their uplink transmission even though, during random access, user terminals cannot use terminal dependent scrambling codes on the uplink.

[0014] The user terminal sends to the radio base station a first random access request message including a random access preamble using random radio channel resources. Then, a second random access response message is received from this radio base station, indicating a change in the countdown time, identified radio resources, as well as a temporary user terminal identifier. The terminal tunes the time countdown by this user terminal to transmit signals to this radio base station based on the information received in this random access response message, and based on this tuned time countdown sends to this radio base station using the indicated radio resources a third message corresponding to the generated a random access message containing the full identity of the user terminal. This third message is bred by using the designated uplink scrambling sequence of the first type, modulated and assigned to radio channel resources. The terminal receives from this radio base station the fourth competition resolution message to complete the random access procedures, followed by normal communication.

[0015] Various non-limiting embodiments of the invention map the first set of uplink scrambling sequences to some other parameter known to the user terminal and base station. Eg.

The first set of uplink scrambling sequences can be mapped to the corresponding random access preamble sequences. Then one of the first set of scrambling sequences can be selected based on the random access preamble contained in the first random access request and mapping message, Another example maps the first set of uplink scrambling sequences to the respective user terminal identifiers and selects one of the first set of uplink scrambling sequences based on the user terminal identifier contained in the second random access and mapping response message. The third example maps the first set of uplink scrambling sequences to the corresponding radio resources used to transmit the random access request message and selects one of the first set of uplink scrambling sequences based on the random access radio channel resources used to send the first random request message to the radio base station access containing the free access and mapping preamble.

[0016] This solution with two types of scrambling sequences can also be used for reference signals contained in uplink random access messages sent to the base station which are used by this base station to estimate the uplink channel, e.g. for correction etc. One of the first set of uplink reference sequences is selected, e.g. uplink reference sequences specifically associated with the radio cell area or base station random access channel, but which are not specifically assigned to any of the user terminals. A random access message is generated using the uplink scrambling sequence selected from the first set and the uplink reference sequence selected from the first set. The user terminal transmits this random access message to the radio base station. Then, the base station informs the user terminal of a second, other type reference sequence to be used in further uplink communication, e.g., a reference value assigned specifically to that user terminal.

[0017] In one non-limiting exemplary embodiment, the user terminal and base station are adapted to communicate with an LTE (long term evolution) radio communication network, wherein the user terminal transmits a first random access request message over a random access channel (RACH). random access channel) and the third message via the uplink-shared channel (UL-SCH). The user terminal identifier, sent by the base station in the second message, may be the temporary identifier of the user terminal used until the user terminal is assigned a radio network terminal (RNTI),

BRIEF DESCRIPTION OF THE FIGURES [0018]

Fig. 1 shows an example of an LTE mobile radio communication system;

Fig. 2 is a flowchart illustrating non-limiting examples of a procedure for preparing a transport block provided from a user access medium layer for radio transmission to a network in an LTE mobile radio communication system;

Fig. 3 is a flowchart illustrating non-limiting examples of a procedure for a user terminal to

-6 ~ performing free access to the radio network;

Fig. 4 is a flowchart illustrating non-limiting examples of a procedure for a base station for receiving and processing random access of a user terminal to a radio network;

Figures 5A and 5B illustrate the assignment between transport and physical channels in a downlink and uplink;

Fig. 6 is a diagram illustrating three basic statuses of a user terminal;

Fig. 7 is a signaling diagram illustrating a non-limiting example of a random access procedure; Fig. 8 illustrates a non-limiting example of random access preamble transmission; and Fig. 9 shows a non-limiting example of a functional block diagram of a user terminal and eNode B as a base station.

DETAILED DESCRIPTION [0019] In the following description, specific details, e.g., specific nodes, functional modules, techniques, protocols, standards, etc. are provided for clarification and without limitation, in order to provide an understanding of the described technology. In other cases, detailed descriptions of well-known methods, devices, techniques etc. have been omitted so as not to obscure the heart of the description with unnecessary details. Individual functional blocks are shown in the figures. Qualified persons will notice that the functions of these blocks can be implemented using individual hardware circuits, using software and data in combination with an appropriately programmed microprocessor or general purpose computer, using dedicated integrated circuits (ASIC). programmable logic matrix and / or using one or more signal processors (DSP) digital signal processor).

[0020] It will be apparent to a skilled person that in addition to the specific examples disclosed herein, other embodiments of the invention may be implemented. The technology has been described in the context of an evolved 3GPP UMTS system, e.g. LTE, to provide an exemplary and non-limiting context for explanation. See, e.g., the LTE system diagram shown in Fig. 1. However, this technology is not limited to LTE and can be used in any modern radio communication system. In addition, the following solution that uses two different types of scrambling sequences - one for random access and one for random access communication - can also be used for known channel estimation reference signals (sometimes called pilots). However, a detailed description has been provided for the use of scrambling sequences, with the understanding that similar details apply to reference signals. To simplify the description, a user device (UE) is often without restrictions, called a user terminal or mobile terminal, and the eNodeB node is referred to as a more general and better known term, a base station.

[0021] Fig. 3 is a flowchart illustrating non-limiting example procedures for a user terminal for performing random access to a radio network using an uplink scrambling code that is generally available to all user terminals needing free access to a service in a particular cell. The user terminal detects the first type of scrambling sequences, e.g. uplink scrambling sequences specifically associated with a cell area or channel

- random access of the base station, but which are not specifically assigned to any of the user terminal (step S1). A first type uplink scrambling sequence of the first type is determined (step S2) and a random access message (step S3) is generated using the first uplink scrambling sequence selected from these first. The user terminal transmits this message to the radio base station for free access (step S4). After this random access message is given, the user terminal receives from this radio base station an uplink scrambling sequence of a second, other type, e.g. an uplink scrambling sequence selected from a second set of uplink scrambling sequences assigned to individual user terminals (step S5) . The user terminal uses this uplink scrambling sequence of the second type in further communication with this radio base station. Similar procedures can be used for known uplink reference signals.

[0022] Fig. 4 is a flowchart illustrating non-limiting example procedures corresponding to the above for a base station for receiving and processing random access of a user terminal to a radio network. Each base station in the network has its own set of preamble sequences, reference signals and scrambling codes or sequences independent of the terminal. The base station broadcasts, implicitly or explicitly, on a broadcast channel, e.g. in the BCH, its set of preambles and uplink scrambling sequences (step S10). If the base station does not explicitly broadcast the scrambling sequence to be used, the identity of the cell from which the scrambling sequence to be used can be derived, e.g., by alignment between the sequence and the cell identifier. Uplink scrambling sequences can be e.g. specifically associated with the cell area or random access channel of the radio base station and are not specifically associated with any of the user terminals. The base station then waits for the first random access request message to be received from the user terminal which contains one of the preambles of that base station. In response, the base station sends a second random access response message to this user terminal indicating a change in the countdown time, the identified radio resources, and the user terminal identifier. The third message, corresponding to the random access message generated, which contains the identity of the user terminal, is descrammed using that selected from the first set of uplink scrambling sequences (step S11). The base station then sends a fourth message to the user terminal, comprising an uplink scrambling sequence of a second, other type selected from a second set of uplink scrambling sequences, e.g., uplink scrambling sequences, which are assigned to individual user terminals (step S12). The user terminal uses this second uplink scrambling sequence in further communication with this radio base station. Similar procedures can be used for known uplink reference signals.

[0023] For a better understanding of the following example and the non-limiting free access procedure in LTE, reference is made to Figs. 5A and 5B, which respectively illustrate the assignment between transport and physical channels on the downlink and uplink. Downlink transport channels are as follows: broadcast channel (BCH), call channel (PCH), shared downlink channel (DL-SCH) downlink shared channel) and mutticast mode channel (MCH). The BCH channel is assigned to the Physical Broadcast Channel (PBCH), while the PCH and DL-SCH channels are assigned to the Physical Shared Channel

-8 Links (PDSH). Uplink transport channels include the random access channel (RACH) and uplink shared channel (UL-SCH). The RACH channel is assigned to a Physical Random Access Channel (PRACH), while the UL-SCH channel is assigned to a Physical Shared Channel Link (PUSCH). Physical Uplink Shared Channel).

[0024] In the LTE system, as in other mobile radio communication systems, the mobile terminal may be in a number of different operating states. Fig. 6 illustrates these conditions for the LTE system. After starting, the mobile terminal enters the LTE_DETACHED state. In this state, the mobile terminal is not known to the network. Before any further communication between this mobile terminal and the network can take place, the mobile terminal must register in the network using the random access procedure to enter the LTE "ACTIVE" state. The LTE_DETACHED state is primarily the state used at startup. When the mobile terminal registers to the network, it is usually in one of the other states: LTE_ATIVE or LTEJDLE.

[0025] The LTE_ACTIVE state is a state used when the mobile terminal is involved in transmitting and receiving data. In this state, the mobile terminal is connected to a specific cell of the network. The mobile terminal has been assigned one or a number of Internet Protocol (IP) addresses or other types of data packet addresses, as well as terminal identity, C-RNTI Identifier (ang. Cell Radio Network Temporary Identifier), used for signaling between this mobile terminal and the network. The LTE_ACTIVE state has two substations, IN_SYNC and OUT_OF_SYNC, depending on whether the uplink is synchronized with the network or not. As long as the uplink is in the IN_SYNC state, uplink transmissions of user data and lower layer control signaling are possible. If there is no uplink transmission in the given time window, then the uplink is considered not in synchronization, in which case the mobile terminal must perform a free access procedure to restore uplink synchronization.

[0026] The LTEJDLE state is a low activity state in which the mobile terminal is most of the time dormant to reduce battery consumption. Uplink synchronization is not maintained, and therefore the only uplink transmission operation that may occur is free access for transition to LTE_ACTIVE. The mobile terminal stores its IP addresses (its addresses) and other internal information in order to quickly switch to LTE_ACTIVE state when needed. The location of the mobile terminal is partly known to the network, so that the network knows at least the group of cells in which the mobile terminal is to be called.

[0027] A non-limiting example of a random access procedure is illustrated in Fig. 7 and includes four steps, called steps 1-4, with four associated signaling messages, called messages 1-4. The base station sends a set of preambles associated with this base station, RACH channel resource information, as well as other information, in a broadcast message sent regularly on a broadcast channel that active mobile terminals can regularly listen to. In the first stage, after receiving and decoding information broadcast by the base station (eNodeB node), the user terminal selects one of the base station's free access preambles and sends it via the RACH channel. Base station

Monitors the RACH channel and detects this preamble, which allows the base station to estimate transmission time from the user terminal. Uplink synchronization is necessary to allow the terminal to transmit uplink data to the base station.

[0028] The random access preamble includes a known sequence selected arbitrarily by the mobile terminal from a set of known preamble sequences available for random access to a specific base station. When performing a random access test, the terminal selects any one preamble sequence from the set of preamble sequences allocated to the cell to which the terminal is trying to access. As long as no other terminal attempts random access using the same preamble sequence at the same time, no collision occurs and the random access request is likely to be detected by the base station. The preamble is transmitted by the user terminal in radio channel resources, e.g. time / frequency resources, designated for random access purposes, e.g. RACH channel.

[0029] Fig. 8 conceptually illustrates the transmission of a random access preamble according to the LTE specification current at the time of writing. One of the non-limiting examples of the production of suitable preambles is based on Zadoff-Chu (ZC) sequences and their cynical shifts. Zadoff-Chu sequences can also be used e.g. to generate uplink reference signals contained in each data frame for channel estimation purposes.

[0030] The user terminal performing the random access attempt obtains, prior to the transmission of this preamble, downlink synchronization due to the cell search procedure using the countdown time information broadcast by the base station. But, as explained above, the uplink countdown is not yet established. The beginning of the uplink transmission frame in the terminal is determined relative to the beginning of the uplink transmission frame in the terminal. Due to the propagation delay between the base station and the terminal, the uplink transmission will be delayed relative to the downlink transmission time at the base station. Since the distance between the base station and the terminal is not known, there is uncertainty in the countdown time in the connector corresponding to the double distance between the base station and the terminal. To account for this uncertainty and to avoid interference with subsequent frames not used for free access, a guard period is used.

Returning to the second random access signaling step shown in Fig. 7, in response to the detected random access attempt, the base station sends a random access response message 2 via a downlink shared channel (DL-SCH). Message 2 contains an index or other random access preamble sequence identifier detected by the base station and for which this response is correct, an uplink countdown correction or time-out command timing advance) calculated by this base station after processing the received random access preamble, a scheduling assignment indicating the resources that the user terminal is to use to transmit the message in the third message sent from the mobile terminal to the base station, as well as the temporary identity of the user terminal used for further communication between this user terminal and this base station. After completing Stage 2, the user terminal is in a state of time synchronization.

[0032] If the base station detects a number of random access attempts (from different user terminals), then response messages to random access requests 2 to a number of terminals

- 10mobiles can be combined in one transmission. Therefore, the random access response 2 response message is serialized on the DL-SCH channel and indicated on the Physical Link Control Channel Physical Downlink Control Channel (PDCCH) using a common identity reserved for the random access response. The PDCCH channel is a control channel used to inform the terminal whether the DL-SCH channel contains data intended for that terminal, and if so, in which time-frequency resources the DL-SCH channel can be found. All user terminals that sent the preamble monitor the PDCCH for a random access response sent using a predetermined common identity used by the base station for all random access responses.

[0033] In the third step 3, the user terminal sends the necessary information to the network in message 3 using the uplink scheduling resources allocated in the random access response message 2 and synchronized on the uplink. Sending an uplink message in step 3 in the same way as "normal" serialized uplink data, i.e. on a UL-SCH, instead of appending it to the preamble in the first stage, is beneficial for a number of reasons. First, the amount of information sent without uplink synchronization should be minimized, as the need for a long guard period makes such transmissions relatively costly. Secondly, the use of the "normal" uplink transmission scheme for message transmission allows the allocation size and modulation scheme to be adjusted, e.g. to different radio conditions. Thirdly, this enables the use of hybrid ARQ soft linking technique for an uplink message, which may be advantageous, especially in limited range situations, because it allows reliance on one or a certain number of retransmissions to accumulate enough energy for link signaling in up to ensure a sufficiently high probability of successful transmission. The mobile terminal sends its temporary mobile terminal identity to the network, e.g. C-RNTI temporary identity in the third step using the UL-SCH channel. The exact content of this signaling depends on the state of the terminal, e.g., whether it is already known to the network or not.

[0034] As long as terminals that performed random access at the same time use different preamble sequences, no collisions occur. But there is some likelihood of competition when a number of terminals use the same free access preamble at the same time. In this case, a number of terminals respond in step 2 to the same downlink response message, and in step 3 a collision occurs. Resolution of the collision or settlement of the competition takes place in stage 4.

[0035] In step 4, a contention resolution message is sent from the base station to the terminal on the DL-SCH. This stage resolves the competition when a number of terminals have attempted to access the system on the same resources, indicating which user terminal was detected in the third stage. A number of terminals performing simultaneous random access attempts using the same preamble sequence in step 1 listens to the same response message in step 2 and therefore has the same user terminal temporary identifier. Thus, in step 4, each terminal receiving a downlink message compares the identity of the user terminal in this message with the identity of the user terminal that emerged in the third stage. Only a user terminal that has observed compliance of the identity received in the fourth stage with the identity sent as part of the third stage confirms the successful implementation of the procedure

- 11 free access. If the terminal does not yet have a C-RNTI identity assigned, the temporary identity of the second stage is raised to the rank of C-RNTI; otherwise, the user terminal retains its already assigned C-RNTI identity. Terminals that do not match the identity received in the fourth stage must restart the free access procedure from the first stage.

[0036] As explained above, the user terminal identity contained in message 3 is used as part of the contention resolution mechanism in the fourth stage. Continuing the non-limiting example of LTE technology, if the user terminal is in the LTE_ACTIVE state, i.e., it is connected to a known cell and therefore has a C-RNTI identity assigned, this C-RNTI identity is used as the terminal identity in the uplink message. Otherwise, the terminal identifier in the core network is used, and the base station must engage the core network before responding to this uplink message in step three.

[0037] In this non-limiting example for LTE technology, only the first stage uses physical layer processing particularly adapted for random access. The last three steps use the same physical layer processing as "normal" data transmissions on the uplink and downlink, which simplifies the implementation of both the terminal and the base station. Since the transmission scheme used for data transmission is adapted to provide high spectral flexibility and high capacity, it is desirable to use these features also when exchanging random access messages.

[0038] In the exemplary, non-limiting context of LTE technology, the steps of general processing described in Fig. 2, including CRC sum calculation, coding, HARQ technique, scrambling, modulation and DFTS-OFDM modulation, are used by the user terminal for message 3 of Fig. 7 and subsequent uplink transmissions from this user terminal to the base station (in the initial uplink random access message, in step 1, scrambling is not used). The different uplink scrambling sequences in the terminal depend on the type of uplink transmission. For random access message 3, a first type scrambling sequence is used, e.g., cell dependent or random access scrambling code. For subsequent "normal" uplink data transmissions, i.e. when the base station assigned a non-temporary identity to the terminal, a second type of scrambling sequence is used, e.g. terminal-dependent scrambling code. A similar solution with two types can be used for the uplink reference signals used by the base station for channel estimation: the first type, e.g. cell-dependent or random access-dependent reference signal for random access 3, followed by the second type, e.g. assigned or an uplink reference signal sequence associated with the base station for the following "normal" data transmissions.

[0039] When the base station assigns the scrambling sequence and / or reference sequence to the mobile terminal, this terminal-dependent scrambling sequence and / or reference sequence is used (are used) for all subsequent uplink data transmissions in this particular connection via the link up. The scrambling sequence and / or reference sequence to be used can be configured directly in the mobile terminal or associated with the terminal's identity (e.g. C-RNTI) that the base station assigns to the mobile terminal.

[0040] Above, the user terminal uses the scrambling sequence to scramble the message 3

- cell dependent, because before performing random access the user terminal has decoded the broadcast information of the base station / cell and thus knows the identity of the cell it is accessing, the random access preambles associated with that cell, and the cell dependent scrambling sequences and / or reference values. As long as terminals that simultaneously perform random access are assigned different time / frequency resources for their respective uplink 3 random access messages, there is no interference between these users, and the lack of randomization between users is not a problem.

In a non-limiting embodiment of the invention, an unambiguous assignment is introduced between the random access preamble sequence used in the random access request message sent in step 1 of Fig. 7 and the scrambling sequence used to scramble the random access message sent in step 3. Since both the base station and the user terminal know the preamble used for the random access request message sent in step 1 at the time when message 3 is to be sent, both of them know which scrambling sequence to use.

[0042] In another non-limiting embodiment of the invention, the base station assigns a scrambling sequence to the user terminal to be used to scramble the message 3 in part of the response to the random access request issued in step 2 of Fig. 7 (i.e. before message 3). In one example, this can be done by establishing a unique assignment between the temporary user identifier sent in message 2, e.g. temporary identifier C-RNTI and the scrambling sequence to be used.

[0043] Yet another non-limiting example associates the scrambling sequence to be used by the user terminal to scramble the message 3 with the time-frequency resources used by this user terminal to grant the random access preamble (message 1). In this case, the scrambling sequence will be known to both the base station and the user terminal because both of these devices know the time-frequency resources used for the first random access request message. In this example, the scrambling sequence will be shared between all user terminals transmitting the preamble of a random access request using the same time-frequency resources. But as long as all these terminals are assigned different time / frequency resources for their own random access message 3, there is no interference between these users, and no randomization between users is no problem. [0044] Combinations of one or more of these four different embodiments may also be used. Again, the principles described in the above scrambling sequence example and these four embodiments can also be used for the uplink reference values ​​used to estimate the uplink channel. In other strengths, one generic or shared reference type may be used for the uplink random access message 3, and another terminal-dependent reference type may be used for the subsequent uplink communication associated with the same connection.

[0045] There may be situations in which a user terminal has already been assigned an identity, but it will still need to perform random access. One example occurs when the terminal

-13 it registers to the network, but it loses uplink synchronization and, as a consequence, must attempt random access to recover uplink synchronization. Although this user terminal has an identity assigned, in this case, the terminal dependent scrambling cannot be used for message 3, because until the message 3 is received, the network does not know why the terminal is attempting random access. As a result, the cell scrambling sequence must be used instead of the outdated terminal dependent scrambling sequence.

[0046] Thus, the benefits of terminal-dependent scrambling in normal data transmissions are preserved without affecting the functionality of the random access procedure. As described above, terminal dependent scrambling randomizes interference, which increases uplink transmission performance and provides additional flexibility for scheduling.