Method for accessing a communication network, associated method, terminal, base station and corresponding computer program

Abstract

The present invention relates to a method for accessing a communication network implemented by a terminal, comprising: - receiving (211) system information broadcast by a network, the system information comprising an identification of at least one time-frequency resource capable of carrying information related to a unique terminal identifier, - sending (212) an access request to the network, the access request carrying a first piece of information representing the unique identifier of the terminal, the first piece of information being sent on at least one of the time-frequency resources identified by the system information, referred to as a specific resource, - authorizing (213) access to the network in the event of receiving a response to the access request, the response carrying a second piece of information representing the unique identifier of the terminal.

Description

Technical Field

[0001] The field of the invention is that of digital communications.

[0002] More precisely, the invention relates to the stage of attaching a terminal to a communication network. It proposes in particular a solution for fast access to a network, for example for applications of the instant messaging type.

[0003] The invention is particularly, but not exclusively, used in the field of LTE (Long Term Evolution) or 5G. Background Art

[0004] Conventionally, in order for a terminal to communicate with another terminal in a communication network, two phases are implemented: a phase of attachment to the communication network, during which the terminal is identified, synchronized with the network and configured, and a communication phase, during which the terminal can exchange useful data with the network and / or with another terminal attached to the network.

[0005] For example, according to the LTE standard, a random access procedure based on the use of a RACH channel (Random Access Channel) called the RACH procedure is implemented to enable a terminal to attach to the network. Such a channel is "random access" because, from the network's point of view, it is difficult to know at which moment a terminal will seek to connect to the network.

[0006] The main objectives of the RACH procedure are to ensure synchronization of the terminal and the base station (eg, an eNB according to the LTE standard) on the upstream link and to identify the terminal so that the network can know it and configure it.

[0007] The synchronization between the base station and the terminal on the downlink can be ensured by periodically broadcasting system information carrying synchronization information.

[0008] The main steps of the RACH procedure are described below.

[0009] like Figure 1 As shown, when a terminal UE exits standby mode or enters the coverage area of ​​a base station (e.g., eNodeB), it receives system information 11 broadcasted periodically in the network by an entity of the network (e.g., base station eNodeB). This information specifically identifies at least one time-frequency resource, referred to as RACH resource, intended to be used by the terminal for a RACH procedure.

[0010] On receiving this system information, the terminal UE randomly selects a preamble from a set of available preambles and sends a first message 12 on the RACH resource carrying the preamble, an identifier associated with the RACH resource and therefore known to the network, noted as RA-RNTI (Random Access-Radio Network Temporary Identifier), and a possible indication of the capacity to be provided for data transmission. In particular, the identifier RA-RNTI can be used to detect transmission errors (CRC or Cyclic Redundancy Check).

[0011] Since the network has not yet identified the terminal, the network (or more precisely, an entity of the network, such as a base station) responds by a second message 13, noted as RAR (Random Access Response), which carries an identifier of the preamble received on the RACH resource, noted as PID (Preamble ID), an estimate of the time offset to be applied by the terminal to the task of the message taking into account the travel time between the terminal and the base station (noted as TA (Timing Advance)), a temporary identifier for accessing the network (noted as TC-RNTI (Temporary Cell Radio Network Temporary Identifier)), and an indication of the resources allocated for communication on the uplink (noted as UL Grant). These various parameters can be encapsulated in a packet and sent on the MAC layer. In particular, such a packet can be encoded using an identifier RA--RNTI associated with the RACH resource and therefore known to the network. In this way, only the terminal that has sent the first message 12 on the RACH resource can decode these packets.

[0012] On receiving these packets, the terminal can therefore decode them and verify whether the identifier PID indeed corresponds to the preamble it selected and sent in the first message 12. If this is the case, it can continue decoding the various parameters. Otherwise, it interrupts the decoding.

[0013] When the terminal has verified that the received identifier PID does correspond to the transmitted preamble, it knows that the network correctly received the first message 12 with the preamble. Therefore, it can adjust its sending moment while taking into account the parameter TA and send its identifier UE_ID in the third message 14 on the resources granted for uplink communication UL. The identifier UE_ID is, for example, the IMSI number (International Mobile Subscriber Identifier) ​​of the SIM card of the terminal. In particular, the third message 14 can be encoded by using a temporary identifier TC-RNTI generated by the base station.

[0014] When receiving the request, the base station may send a fourth message 15 to the terminal to resolve possible conflict problems. The message carries the identifier UE_ID of the terminal.

[0015] If this identifier UE_ID of the terminal is the same as the identifier sent in the third message, this means that the terminal is known to the network. Therefore, the terminal can change the temporary identifier TC-RNTI to C-RNTI (cell RNTI), which is a specific identifier used by the terminal during the communication phase with the network after the attachment phase (for example, as a CRC to detect transmission errors).

[0016] Otherwise, this means that the network does not know the terminal. Therefore, the terminal must restart the RACH process.

[0017] After the RACH procedure, the base station thus knows the identity UE_ID of the terminal. However, the terminal cannot send useful data (i.e. start a communication phase) as long as the network has not yet configured the terminal by implementing, for example, a protocol for controlling radio resources of the RRC type (Radio Resource Control). This configuration is necessary in order for the terminal to effectively use the radio link provided by the base station.

[0018] Therefore, RACH and RRC procedures are particularly useful for configuration of access networks and terminals.

[0019] However, the disadvantage of these techniques is that they must be implemented every time the terminal wishes to access the network, for example when the terminal exits standby mode or switches to a new cell of the cellular network (handover). However, such techniques are rather lengthy to implement and expensive in terms of resources.

[0020] In particular, when the communication phase has a short duration, for example when the terminal sends a message of the instant messaging type (e.g. SMS, MMS, chat, messages sent via Facebook, Whatsapp, Twitter-trade marks type applications), the phase of attaching to the network may be more expensive in terms of time and / or resources than the communication phase. In fact, such instant messages usually have a small size of the order of a few bytes or a few kilobytes, and the cost of the attaching phase becomes non-negligible relative to the cost of the communication phase.

[0021] Therefore, there is a need for a new technology for accessing networks that is easy to implement and not very expensive in terms of time and / or resources. Summary of the invention

[0022] According to at least one embodiment, the present invention proposes a method implemented by a terminal for accessing a communication network.

[0023] According to the present invention, the method comprises:

[0024] - receiving system information broadcast by the network, the system information comprising an identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier, sending to the network an access request, the access request carrying a first piece of information representing the unique identifier of the terminal, the first piece of information being sent on at least one of the time-frequency resources identified by the system information, called specific resources,

[0025] - authorizing access to the network upon receipt of a response to the access request, the response carrying a second piece of information representative of the unique identifier of the terminal.

[0026] The proposed solution therefore allows identifying in the system information broadcast in the network one or more specific time-frequency resources that a terminal will be able to use starting from its first transmission to the network to send its unique identifier, which may be its physical layer identifier, its IMSI identifier or any other unique identifier such as, for example, its MSISDN (Mobile Station ISDN Number) identifier.

[0027] Thus, the procedure for accessing a network according to at least one embodiment of the present invention is simplified relative to the prior art, since it is based on the exchange of two main messages (an access request carrying a unique identifier of the terminal, and a response to the request), while it is based on the exchange of two main messages according to the protocol described above. Figure 1 The prior art describes the exchange of four main messages.

[0028] Due to the limited number of messages exchanged, the procedure for accessing the network according to at least one embodiment of the present invention is also faster than the RACH procedure described with respect to the prior art and allows optimization of spectrum efficiency during the access procedure.

[0029] Note that such an access procedure must be implemented each time a terminal leaves the network (e.g., because it enters standby mode) and wishes to "enter" the network again (e.g., because it exits standby mode). It is therefore desirable to simplify and speed up the access procedure.

[0030] In particular, if a response to the access request is received and if the response carries a second piece of information representing a unique identifier of the terminal, access to the network is authorized. For example, the first piece of information representing the unique identifier of the terminal and the second piece of information are identical or related. These first and second pieces of information allow the same terminal to be identified.

[0031] According to the first embodiment, the first piece of information indicating the unique identifier of the terminal may be sent in a dedicated resource noted as TFR based on a system information identification.

[0032] According to a second embodiment, the first piece of information representing the unique identifier of the terminal can be sent in resources traditionally used for channel access (e.g., RACH resources). According to this second embodiment, the network can reserve larger time-frequency resources for the transmission of the first piece of information representing the unique identifier and traditional information for accessing the channel.

[0033] According to a specific embodiment, the access request also carries a useful message intended to be sent to at least one other terminal. In particular, the useful message is sent together with a first piece of information representing a unique identifier of the terminal on a specific time-frequency resource or on another time-frequency resource identified in the system information and capable of carrying the useful message.

[0034] The proposed solution thus allows useful messages to be sent from the terminal to the network during the access procedure, ie without requiring a previous configuration of the terminal (eg based on the implementation of a protocol for controlling radio resources of the RRC type).

[0035] In particular, the proposed solution allows improving the spectral efficiency of the network, especially when the terminals send messages using instant messaging type applications (SMS, MMS, chat, Facebook, Twitter, WhatsApp-trademarks, etc.).

[0036] In this regard it should be noted that the unique identifier of the terminal allows in particular the identification of the transmitter of a useful message via an application of the social network type. It is therefore an identifier of application level.

[0037] According to a particular embodiment, the system information identifies at least two time-frequency resources capable of carrying the useful message. According to this embodiment, the method enables the selection of at least one of the time-frequency resources while taking into account the size of the useful message intended to be sent to at least one other terminal. In this case, the useful message can be sent on the selected resource.

[0038] For example, the system information identifies a first resource (denoted TFR1) for sending useful messages having a size of approximately several bits, a second resource (denoted TFR2) for sending messages of several bytes, and a third resource (denoted TFR3) for sending messages of several kilobytes.

[0039] Hence, the use of the time-frequency resources is optimized by adapting them to the size of the useful message.

[0040] According to a particular embodiment, a first piece of information representing a unique identifier of the terminal and / or a useful message is sent to the network while taking into account a piece of information about modulation and coding associated with a specific time-frequency resource selected for transmission. This piece of information about modulation and coding is obtained based on system information.

[0041] In this way, the terminal knows the modulation and coding scheme (MCS) to be used in the network, in particular for sending useful data starting from the beginning of the access procedure.

[0042] According to a particular embodiment, the unique identifier of the terminal is an integer and the transmission also transmits a reference signal obtained by applying a cyclic offset to a predefined reference sequence.Such a cyclic offset may be determined according to the unique identifier of the terminal.

[0043] Therefore, the reference signal sent from the terminal to the network does not carry the traditional reference sequence, but a modified version of this sequence (cyclic offset) which allows the unique identifier of the terminal or part of this identifier to be sent directly in the reference signal.

[0044] Thus, by reducing the amount of bits required to send the unique identifier of the terminal, the transmission bit rate is optimized.

[0045] For example, the reference signal belongs to the demodulation reference signal type (DMRS). For the reference sequence, it can be defined for the network, normalized or defined in other ways. It is a sequence known to the terminal and at least one other entity of the network (such as a base station).

[0046] In particular, when the unique identifier of the terminal is greater than the maximum number of cyclic shifts, the first piece of information representing the unique identifier of the terminal includes the entire portion of the ratio between the unique identifier and the maximum number of cyclic shifts, also referred to as a residual value. In particular, the maximum number of cyclic shifts can be obtained based on the system information.

[0047] In this way, the amount of bits required to send the first piece of information representing the unique identifier of the terminal is small.

[0048] For example, the maximum number of cyclic shifts is equal to the length of the reference sequence.

[0049] Alternatively, the terminal may send its unique identifier directly to the network.

[0050] According to a specific embodiment, the access request also carries a preamble selected from a plurality of preambles, the preamble being sent on a specific time-frequency resource or on a time-frequency resource (e.g., a RACH resource) capable of carrying a preamble identified based on the system information. According to this embodiment, when the response to the access request carries a second piece of information representing a unique identifier of the terminal and a piece of information representing the selected preamble, authorization to access the network is granted.

[0051] The time-frequency resources dedicated to the transmission of the preamble are also referred to as RACH opportunities. For example, such RACH opportunities are associated with one or more time-frequency resources that can carry useful messages.

[0052] According to a particular embodiment, the access request also carries at least one indicator indicating that the terminal returns to standby mode after access to the network is granted.

[0053] For example, a portion of a specific time-frequency resource is reserved for the transmission of such an indicator. Optionally, a portion of the time-frequency resources dedicated to the transmission of a preamble is reserved for the transmission of such an indicator. Alternatively, at least two types of preambles are defined, a first type of preamble to be used when the terminal wishes to enter standby mode after having accessed the channel, and a second type of preamble to be used when the terminal wishes to continue the configuration process after having accessed the channel. According to this alternative, the indicator is therefore the type of preamble selected.

[0054] Such an indicator can in particular be used by entities of the network to detect the transmission of messages of the instant messaging type for which the terminal wishes to return to standby mode after the useful message has been sent.

[0055] In particular, when the terminal has received a response to the access request and access to the network is authorized, the terminal may enter standby mode. In this way, the energy consumption of the terminal issuing the access request is limited.

[0056] Alternatively, the terminal may remain in active mode while access to the network is granted.

[0057] For example, if the access request does not carry useful information, the method implements a configuration phase between the terminal and the network.

[0058] In fact, if the access request carries the first piece of information related to the unique identifier of the terminal, but does not carry a useful message, this means that the terminal uses the proposed solution to quickly access the network. In this case, when access to the network has been authorized, the terminal does not want to return to standby mode.

[0059] According to a specific embodiment, in the event of receiving a response to the access request that does not carry a second piece of information representing the unique identifier of the terminal, the method comprises retransmitting the access request, the first piece of information representing the unique identifier of the terminal being sent on a new specific time-frequency resource identified in the response.

[0060] This particular embodiment can be particularly implemented when an entity of the network (e.g. a base station) can decode the preamble of an access request sent on a dedicated time-frequency resource, but cannot decode a useful message and / or the first piece of information representing a unique identifier of a terminal of an access request sent on a specific time-frequency resource.

[0061] According to this embodiment, instead of completely restarting the access procedure, new specific resources may be allocated to the terminal for sending the first piece of information representing the unique identifier of the terminal and optionally a useful message.

[0062] Furthermore, since the base station indicates to the terminal new resources to be used for sending the first piece of information representative of the unique identifier of the terminal and optionally a useful message, the risk of collisions with access requests issued by other terminals is limited.

[0063] According to particular characteristics, in the event that no response to an access request is received after a predetermined time interval, the method comprises retransmitting the access request.

[0064] In other words, after sending the access request, the terminal continues to listen for a predetermined duration, referred to as the RAR window. If it has not received a response to its access request after this duration, it may optionally retransmit the access request by using other time-frequency resources.

[0065] In another embodiment, the present invention relates to a corresponding terminal.

[0066] Such a terminal is particularly suitable for implementing the access method described above. It is, for example, a piece of user equipment such as a mobile phone. The terminal may of course include various features related to the method according to the invention, which may be used in combination or alone. Therefore, the features and advantages of the terminal are the same as those of the method described above. Therefore, they will not be described in more detail.

[0067] According to one embodiment, the present invention also relates to a method for attaching a terminal to a communication network. In particular, the method is implemented in an entity of the network (eg a base station).

[0068] According to the present invention, the method comprises:

[0069] - broadcasting of system information by the network, the system information comprising the identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier, verifying the reception of a first piece of information representative of a unique terminal identifier carried by a request for access to the network on at least one of the time-frequency resources identified based on the system information, referred to as specific resources;

[0070] - If the first piece of information representing the unique identifier of the terminal is received, sending a response to the access request to the terminal, the response carrying a second piece of information representing the unique identifier of the terminal.

[0071] According to the above method for accessing a network, the method is particularly suitable for receiving an access request issued by a terminal.

[0072] As already indicated, according to at least one embodiment, it allows a terminal to quickly access a network.

[0073] According to a particular embodiment, the verification also verifies the reception of a useful message intended to be sent to at least one other terminal on a specific time-frequency resource used for the transmission of a first piece of information representing a unique identifier of a terminal or on another time-frequency resource capable of carrying a useful message identified based on the system information.

[0074] The method further comprises, if the first piece of information representing the unique identifier of the terminal and the useful message are received, sending the useful message to the at least one other terminal.

[0075] Therefore, the method according to this embodiment allows optimizing the spectral efficiency of the network.

[0076] According to a particular embodiment, since the unique identifier of a terminal is an integer and a reference signal obtained by applying a cyclic offset to a predefined reference sequence is received on a specific time-frequency resource, the method implements the step of determining the unique identifier of the terminal.

[0077] To this end, knowing the reference sequence and having received the reference signal, it is indeed possible to determine the amount of offset applied to the reference sequence and therefore the unique identifier of the terminal.

[0078] According to a specific embodiment, the method further comprises:

[0079] - verifying that the preamble carried by the access request is received on the time-frequency resource or on at least one time-frequency resource capable of carrying a preamble identified based on the system information,

[0080] -If the preamble is received and the first piece of information representing the unique identifier of the terminal is not received, sending a response to the access request to the terminal, the response carrying a piece of information representing the preamble and identifying a new specific time-frequency resource (i.e., for sending the first piece of information and an optional useful message).

[0081] In another embodiment, the present invention relates to a corresponding base station.

[0082] Such a base station is particularly suitable for implementing the above-described attachment method. It is for example an eNodeB according to the LTE standard, or a gNB according to 5G. The base station may of course comprise various features relating to the method according to the invention, which may be used in combination or individually. The features and advantages of the base station are therefore identical to those of the method described above. Therefore, they are not described in more detail.

[0083] The invention also relates to one or more computer programs comprising instructions for implementing at least one of the methods described above when the program or programs are executed by at least one processor.

[0084] The invention also relates to an information medium readable by a computer and comprising instructions of a computer program as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Other characteristics and advantages of the invention will appear more clearly on reading the following description of specific embodiments given as simple illustrative and non-limiting examples, together with the accompanying drawings, in which:

[0086] Figure 1 shows the main steps of the RACH process according to the prior art;

[0087] Figure 2 The main steps implemented by a terminal and a base station according to an embodiment of the present invention are shown;

[0088] Figure 3 shows the use of specific time-frequency resources according to an embodiment of the present invention;

[0089] Figure 4 An example of a cyclic shift applied to a reference sequence is presented;

[0090] Figure 5 shows messages exchanged between a terminal and a base station according to a first example;

[0091] Figure 6 shows messages exchanged between a terminal and a base station according to a second example;

[0092] Figure 7A simplified structure of a terminal implementing a method for accessing a network according to an embodiment of the present invention is presented;

[0093] Figure 8 A simplified structure of a base station implementing a method for attaching to a network according to an embodiment of the invention is presented. DETAILED DESCRIPTION

[0094] 5.1 General Principles

[0095] The general principle of the invention is based on a novel technique that allows a terminal to simply and quickly attach itself to a network. To this end, the system information traditionally broadcast by the network is modified to identify at least one time-frequency resource capable of sending a piece of information related to a unique terminal identifier to the network. Such a resource is therefore not reserved for a specific terminal, but can be used by any terminal wishing to access the network.

[0096] In particular, the network may reserve a larger time-frequency resource than conventionally reserved for RACH procedures so that the terminal can send its unique identifier (or more generally, the first piece of information representing its unique identifier) ​​using the information conventionally sent on the RACH resources.

[0097] Alternatively, the network may reserve different time-frequency resources so that the terminal can send at least one first piece of information representative of its unique identifier.

[0098] Thus, a terminal wishing to access the network may send its unique identifier and optionally a useful message intended for another terminal directly to the network (i.e. to at least one entity of the network, such as a base station) in the physical layer on at least one specific time-frequency resource reserved by the network.

[0099] Based on the information received, the network can send a response to the terminal. The exchange of these two main messages (access request and response to access request) between the terminal and the network is sufficient to authorize the terminal to access the network or not.

[0100] The terminal can then return to standby mode or remain in active mode and continue the configuration process.

[0101] In particular, in the context of an instant messaging type application according to which the terminal sends one or more short messages, the terminal can access the network and send short messages via the exchange of these two main messages, without having to implement a configuration procedure of the terminal (for example of the RCC type), and can return to standby mode after each transmission if the terminal does not wish to continue the communication phase, or remain in active mode if, for example, several messages have to be sent.

[0102] Next, about Figure 2, presents the main steps implemented by a terminal 21 and entities of a communication network (eg, a base station 22) according to an embodiment of the present invention.

[0103] Typically, the base station 22 broadcasts 221 system information in the network. Such system information may be broadcast periodically and may carry in particular a synchronization signal (eg of the Synchronization Signal Block SSB type) which in particular allows terminals wishing to access the network to synchronize with the base station.

[0104] According to the invention, the system information is modified and comprises the identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier.

[0105] When the terminal 21 exits the standby mode or enters the coverage area of ​​the base station 22, it can therefore receive 211 the system information broadcast by the base station 22 and synchronize with the base station for the downlink.

[0106] Thus, the terminal 21 may send 212 a request to the base station for access to the network. Such an access request carries in particular a first piece of information representing a unique identifier of the terminal. According to the invention, the first piece of information representing the unique identifier of the terminal is sent on at least one of said time-frequency resources (referred to as specific resources) identified based on the system information and therefore reserved by the network.

[0107] The base station 22 observes an uplink channel, for example a RACH channel, and verifies 222 whether a first piece of information representative of a unique identifier of the terminal has been received on one of said time-frequency resources reserved by the network.

[0108] In case of positive authentication, the base station sends 223 to the terminal a response carrying a second piece of information representative of the unique identifier of the terminal.

[0109] The terminal 21 verifies 213 whether a response to the access request has been received.

[0110] In the case of positive authentication, and more precisely in the case of reception of a response to the access request carrying a second piece of information representative of the unique identifier of the terminal, the terminal considers that it is authorized to access the network.

[0111] If it does not wish to continue the configuration process and the communication phase, it can enter the standby mode. Otherwise, it can remain in the active mode.

[0112] 5.2 Description of Specific Embodiments

[0113] An exemplary embodiment of the invention is given below, according to which the access request carries a first piece of information representing a unique identifier of a terminal and a useful message intended to be sent to another terminal.

[0114] In particular, such a useful message can be a short message, ie have a size of approximately a few bits or a few kilobits.

[0115] According to this example, it is considered that the system information provided by the network identifies one or more time-frequency resources that can carry a preamble and are recorded as RACH_O, and for each resource RACH_O, identifies one or more time-frequency resources that can carry a piece of information related to a unique terminal identifier and are recorded as TFR. In addition, according to this example, the resource TFR can also carry useful messages. For example, three resources TFR1-1, TFR1-2 and TFR1-3 are associated with the first resource RACH_O1, two resources TFR2-1 and TFR2-2 are associated with the second resource RACH_O2, and so on.

[0116] In addition to the unique identifier of the terminal, various resources TFR associated with the resource RACH_O may be reserved for sending useful messages with different sizes. The resource TFR1-1 may be reserved for sending useful messages with a small size, for example less than 10 bits (generated, for example, in the context of applications with a low bit rate: data from sensors, M2M (machine to machine) communication, etc.). The resource TFR1-2 may be reserved for sending useful messages with a medium size, for example between 10 bits and 100 bits (generated, for example, in the context of applications with a medium bit rate: Facebook, Twitter-trademarks, etc.). The resource TFR1-3 may be reserved for sending useful messages with a large size, for example greater than 100 bits (generated, for example, in the context of applications with a high bit rate).

[0117] The system information may also carry information about the modulation and codec MCS associated with each resource TFR.

[0118] Furthermore, the system information may carry a piece of information about the maximum number of cyclic shifts that the terminal is authorized to apply to the predefined reference sequence.

[0119] As about Figure 2 As indicated, upon receiving the system information, the terminal may send an access request to the base station during the first phase.

[0120] To this end, it selects a preamble, for example, from a set of preambles traditionally used in RACH procedures, and selects a resource RACH_O from the resources RACH_O identified in the system information. For example, it selects the resource RACH_O1.

[0121] The terminal must then select a resource TFR from the resource TFRs associated with the resource RACH_O1. If it wishes to send only its unique identifier, it can randomly select a resource TFR from the resource TFRs associated with the resource RACH_O1. If it wishes to send its unique identifier and a useful message, it can select a resource TFR while taking into account the size of the useful message it wishes to send. For example, if the useful message to be sent has a size equal to 20 bits, the terminal selects resource TFR1-2.

[0122] Based on the system information, the terminal can also obtain the modulation and coding scheme used to send the useful message on the resource TFR1-2. Note that if the system information identifies several resource TFRs, one or more resource TFRs can be used to send the unique identifier of the terminal on the one hand and the useful message on the other hand. If the system information identifies a single resource TFR, the unique identifier of the terminal and the useful message are sent on the same resource TFR.

[0123] For example, resource TFR1-2 reserves a block consisting of X time intervals and Y carrier frequencies. Figure 3 As shown, resources TFR1-2 may carry a time sequence of X OFDM symbols, each OFDM symbol carrying data modulated in frequency by Y resource blocks.

[0124] according to Figure 3 In the example shown, the third OFDM symbol 31 carries a reference signal modulated by Y carrier frequencies, for example a DMRS type reference signal.

[0125] Typically, such a reference signal carries a reference sequence known to the terminal and the base station. For example, such a reference sequence is normalized.

[0126] According to one embodiment of the present invention, the reference signal carries a version of the reference sequence after a cyclic shift.

[0127] Indeed, since certain resources are not reserved for certain terminals but can be used by any terminal wishing to access the network, the same resources can be used simultaneously by several terminals.The cyclic offset applied to the reference sequence allows in particular the base station to distinguish between various terminals.

[0128] In particular, the offset applied to the reference sequence is determined according to the unique identifier of the terminal.

[0129] Therefore, the reference sequence can be decomposed into N equal parts, where N is the number of authorized cyclic shifts defined in the system information. Therefore, the number of cyclic shifts to be applied to the reference sequence to obtain the reference signal is equal to the identifier UE_ID of the terminal modulo N: mod(UE_ID, N).

[0130] according to Figure 4 In the example shown, the reference sequence 41 may be decomposed into 17 equal parts, where 17 is the number of authorized cyclic offsets defined in the system information.

[0131] If the unique identifier of the terminal is equal to 1, a cyclic shift is applied to the reference sequence and a first cyclic shifted version of the reference sequence 42 is obtained.

[0132] If the unique identifier of the terminal is equal to 2, two cyclic shifts are applied to the reference sequence and a second cyclic shifted version of the reference sequence 43 is obtained.

[0133] If the unique identifier of the terminal is equal to 55, four cyclic shifts are applied to the reference sequence (mod(55, 17)=4).

[0134] According to the latter example, since the unique identifier of the terminal is greater than N, the terminal may also send to the base station a remaining value corresponding to the entire portion of the ratio between the unique identifier and the maximum number of cyclic shifts, ie, the value 3 according to the above example.

[0135] For example, the residual value may be sent specifically on the symbol OFDM of the resource TFR1-2.

[0136] Due to the cyclic shift of the base station and the residual value, the terminal can send the first piece of information indicating its unique identifier to the base station.

[0137] Therefore, the terminal can send an access request carrying a preamble, a first piece of information indicating a unique identifier of the terminal, and a useful message to the base station. This step corresponds to Figure 2 Step 212.

[0138] According to the above example, the preamble can be sent on the resource RACH_O1, and the first information and the useful message representing the unique identifier of the terminal can be sent on the resource TFR1-2. In particular, the data carried by the resource TFR1-2 can be encoded by using the identifier RA-RNTI associated with the resource RACH_O1. More generally, the data sent on a specific resource can be encoded by using the identifier RA-RNTI.

[0139] According to a specific embodiment, the access request may also carry an indicator indicating whether the terminal wishes to enter standby mode when receiving a response to the access request, or wishes to continue the attachment phase, such as by implementing the RCC protocol. The indicator may be sent in particular on resource TFR1-2, on resource RACH_O1, or on another time-frequency resource. Alternatively, at least two types of preambles are defined, a first type of preamble to be used when the terminal wishes to enter standby mode after having accessed a channel, and a second type of preamble to be used when the terminal wishes to continue the configuration process after having accessed a channel. According to this alternative, the indicator is therefore the type of the selected preamble. According to another alternative, the absence of a useful message in the access request means that the terminal wishes to remain in active mode. Therefore, the presence or absence of a useful message can be used as an indicator.

[0140] In particular, if the terminal only occasionally sends useful messages, for example because it uses an instant messaging type application, the indicator may be automatically positioned at a value indicating that the terminal wishes to enter standby mode upon receiving a response to an access request.

[0141] In contrast, if the terminal regularly sends useful messages, the indicator may indicate that the terminal wishes to remain in active mode upon receiving a response to an access request.

[0142] After sending the access request, the terminal keeps waiting for a response on the part of the base station. Therefore, it listens to a dedicated downlink channel, such as the PDCCH (Physical Downlink Control Channel), during a predetermined time interval, also called the RAR window.

[0143] During the second phase, the base station thus processes the access request and may send a response to the terminal to inform it whether it is authorized to access the network, ie whether the access request has indeed been received, or to inform it of a possible conflict.

[0144] In particular, according to the previous example, such a response can be encoded by using the identifier RA--RNTI associated with the resource RACH_O1. In this way, only the terminal that has used the resource RACH_O1 to send the preamble can decode the response of the base station.

[0145] The following describes the processing implemented by the base station.

[0146] The base station monitors an uplink channel, such as a RACH channel, and verifies whether a preamble has been received on a dedicated resource known to the base station (e.g., RACH_O1, RACH_O2). If a preamble has been detected (e.g., on resource RACH_O1), it verifies whether a unique identifier of the terminal has been received on at least one specific resource associated with the dedicated resource carrying the detected preamble (e.g., resources TFR1-1, TFR1-2, TFR1-3).

[0147] Various situations are distinguished according to whether the access request has been fully received, partially received or not received by the base station.

[0148] according to Figure 5 In the first case shown, it is considered that the terminal UE has received the system information 51 broadcast by the base station (e.g. gNB) and has sent an access request 52 carrying a preamble, a useful message and the first information representing the unique identifier of the terminal.

[0149] Considering the previous example again, the base station receives the preamble on resource RACH_O1 and receives the useful message and the first piece of information representing the unique identifier of the terminal on resource TFR1-2. Upon receiving the reference signal sent on resource TFR1-2, the base station can determine the number of cyclic offsets applied to the reference sequence (i.e., 4) because it knows the reference sequence. The base station also receives the residual value. Knowing this residual value (i.e., 3), the number of cyclic offsets applied to the reference sequence (i.e., 4), and the maximum number of authorized cyclic offsets (i.e., 17), the base station can determine the unique identifier of the terminal (3*17+4=55).

[0150] Therefore, the base station can send a response 53 to the terminal, which carries one piece of information (such as PID) representing the preamble sent on the resource RACH_O1 and a second piece of information representing the unique identifier of the terminal. According to the above example, the second piece of information representing the identifier of the terminal is 55 (UE_ID).

[0151] When the terminal receives the response 53 during the RAR window, if it detects that the piece of information representing the preamble PID does correspond to the preamble it selected for the access request, and the second piece of information representing the unique identifier of the terminal does correspond to its unique identifier, it considers that it has been authorized to access the network. In other words, this means that the base station has correctly identified the terminal and received the useful message. Therefore, the useful message is now processed by the network and can be sent to the receiving terminal.

[0152] According to this first case, contrary to the conventional RACH procedure, the parameter TA is not sent from the base station to the terminal. However, the base station knows the value of this parameter.

[0153] In particular, if the access request carries an indicator to return to standby mode after granting access to the network, the terminal may enter standby mode, for example if it has no new useful messages to send within a predefined time interval (e.g. 2 minutes) after receiving a response to the access request.

[0154] according to Figure 6 In the second case shown, it is considered that the terminal UE has received the system information 61 broadcast by the base station (e.g. gNB) and has sent an access request 62 carrying a preamble, a useful message and a first piece of information representing a unique identifier of the terminal.

[0155] However, considering the previous example again, the base station only receives the preamble on resource RACH_O1, but does not receive the useful message and / or the first information representing the unique identifier of the terminal on resource TFR1-2 (e.g., after a transmission problem, decoding problem, synchronization problem, etc. on this time-frequency resource).

[0156] Therefore, the base station can send a response 63 to the terminal, which carries a piece of information (e.g., PID) representing the preamble and identifies at least one new time-frequency resource (e.g., in the form of a parameter "UL Grant") so that the terminal can retransmit the first piece of information representing its unique identifier and the useful message according to this exemplary embodiment. In addition, such a response can optionally carry other parameters traditionally used in the RACH process, such as parameters TA and TC-RNTI. Such parameters can be sent in the response or in a different message.

[0157] When the terminal receives a response 63 during the RAR window, if it detects that the piece of information representing the preamble PID does correspond to the preamble it selected for the access request, but it does not detect the second piece of information representing the unique identifier of the terminal, it considers that the base station has only received the preamble but not the useful message and / or the first piece of information representing the unique identifier of the terminal.

[0158] Therefore, the terminal must retransmit 64 the useful message and the first piece of information representing the unique identifier of the terminal.

[0159] To this end, the terminal uses the new specific time-frequency resource identified in the response. The terminal can use the parameter TA to adjust the sending time of its useful message and the sending time of the first piece of information representing the unique identifier of the terminal, thereby facilitating synchronization with the base station.

[0160] In particular, the useful message and the first piece of information representing the unique identifier of the terminal may be encoded by using a temporary identifier TC-RNTI generated by the base station.

[0161] Since the useful message and the first piece of information indicating the unique identifier of the terminal are sent on new time-frequency resources (particularly new time-frequency resources allocated by the base station to the terminal for the transmission), the probability that the base station receives the useful message and the first piece of information is higher.

[0162] Thus, if the base station has indeed received the useful message and the first piece of information representing the unique identifier of the terminal, the base station can respond with an acknowledgement message 65. In this case, the terminal considers that it has been authorized to access the network, i.e. the base station has correctly identified the terminal and received the useful message.

[0163] Otherwise, the base station may respond with an error message. In this case, the terminal must restart the access process and send a new access request.

[0164] According to the third case not shown, it is considered that the terminal UE has received the system information broadcast by the base station gNB and has sent an access request carrying a preamble code, a useful message and a first piece of information representing a unique identifier of the terminal.

[0165] However, the terminal does not receive a response to the access request during the RAR window. In this case, the terminal considers that the access process has failed. Therefore, the terminal must restart the access process and send a new access request.

[0166] In the above example, for the purpose of illustration, it is considered that an access request carrying a preamble, a first piece of information representing a unique identifier of a terminal, and a useful message is sent. However, it is recalled that only sending the first piece of information representing a unique identifier of a terminal on a time-frequency resource identified by the system information is necessary for the terminal to be able to quickly access the network, such as Figure 2 As shown in Figure 2. The transmission of the preamble and the transmission of the useful message are both optional.

[0167] In particular, the use of a preamble allows the base station to detect that a terminal has entered the network. However, other techniques may be implemented, in particular simply sending by the terminal its unique identifier.

[0168] Furthermore, in the above example, the transmission of the preamble on the resource RACH_O1 and the transmission of the first piece of information representing the unique identifier of the terminal on the resource TFR1-2 are considered. Note that if the size of the time-frequency resource reserved by the network is sufficient, the first piece of information representing the unique identifier of the terminal and optionally the useful message can be sent on the resource RACH_O1.

[0169] 5.3 Equipment

[0170] Finally, about Figure 7 and Figure 8, presenting a simplified structure of a terminal and a network entity (eg, a base station) according to at least one of the above embodiments.

[0171] like Figure 7 As shown, the terminal according to at least one embodiment of the present invention includes at least one memory 71 and at least one processing unit 72, which is equipped with, for example, a programmable computer or a special-purpose computer, such as a processor P, and is controlled by a computer program 73 to implement the steps of the method for accessing a communication network according to at least one embodiment of the present invention.

[0172] At initialization, the code instructions of the computer program 73 are loaded into RAM memory, for example, before being executed by the processor of the processing unit 72 .

[0173] The processor of the processing unit 72 implements the steps of the method for accessing a communication network according to the instructions of the computer program 73 to:

[0174] - receiving system information broadcast by the communication network to which the terminal wishes to access, the system information comprising an identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier,

[0175] - sending an access request to the network, the access request carrying a first piece of information representing a unique identifier of the terminal, the first piece of information being sent on at least one of the time-frequency resources identified based on the system information, referred to as a specific resource,

[0176] - receiving a response to the access request, in which case the terminal's access to the network is authorized, the response carrying a second piece of information representative of the unique identifier of the terminal.

[0177] like Figure 8 As shown, the base station according to at least one embodiment of the present invention includes at least one memory 81 and at least one processing unit 82, which is equipped with, for example, a programmable computer or a special-purpose computer, such as a processor P, and is controlled by a computer program 83 to implement the steps of the method for attaching to a network according to at least one embodiment of the present invention.

[0178] Upon initialization, the code instructions of the computer program 83 are loaded into RAM memory, for example, before being executed by the processor of the processing unit 82 .

[0179] The processor of the processing unit 82 implements the steps of the above-described method for attaching to a network according to the instructions of the computer program 83 to:

[0180] - broadcasting system information comprising the identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier,

[0181] - verifying the reception of a first piece of information representative of a unique identifier of the terminal carried by a request for access to the network on at least one of the time-frequency resources identified based on the system information, called specific resources,

[0182] - If the first piece of information representing the unique identifier of the terminal is received, sending a response to the access request to the terminal, the response carrying a second piece of information representing the unique identifier of the terminal.

Claims

1. A method for accessing a communication network implemented by a terminal, comprising: - receiving (211) system information broadcast by the network, the system information comprising an identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier, - sending (212) an access request to the network, the access request carrying a first piece of information representing a unique identifier of the terminal, the first piece of information being sent on at least one of the time-frequency resources identified based on the system information, referred to as a specific resource, - authorizing (213) access to said network in the event of receipt of a response to said access request, said response carrying a second piece of information representative of a unique identifier of said terminal, The access request further carries a useful message sent on the specific resource or on at least one time-frequency resource capable of carrying a useful message, and the at least one time-frequency resource is identified based on the system information.

2. According to the method of claim 1, according to the method, since the system information identifier can carry at least two time-frequency resources of the useful message, the method realizes the selection of at least one of the time-frequency resources while considering the size of the useful message.

3. The method according to claim 1 or 2, according to which, since the unique identifier of the terminal is an integer, the transmission also sends a reference signal obtained by applying a cyclic offset to a predefined reference sequence, wherein the cyclic offset is determined according to the unique identifier of the terminal.

4. The method according to claim 3, according to which, when the unique identifier of the terminal is greater than the maximum number of cyclic shifts, the first piece of information representing the unique identifier of the terminal includes the entire portion of the ratio between the unique identifier and the maximum number of cyclic shifts, The maximum number of cyclic shifts is obtained based on the system information.

5. The method according to claim 1, according to which the access request also carries at least one indicator, the at least one indicator indicating that the terminal returns to standby mode after access to the network is granted.

6. The method according to claim 1, wherein the access request further carries a preamble selected from a plurality of preambles, and the preamble is sent on the specific resource or on a time-frequency resource capable of carrying the preamble identified based on the system information. According to the method, when the response to the access request carries a second piece of information representing a unique identifier of the terminal and a piece of information representing the selected preamble, authorization to access the network is granted, And according to the method, in the event of receiving a response to the access request that does not carry a second piece of information representing a unique identifier of the terminal, the method includes retransmitting the access request, with the first piece of information representing the unique identifier of the terminal being sent on a new specific time-frequency resource identified in the response.

7. The method according to claim 1, according to which the useful message is an instant message type message.

8. The method according to claim 1 , according to which the first piece of information and / or the useful message is sent to the network while taking into account a piece of information about modulation and coding associated with the corresponding time-frequency resource, the piece of information about modulation and coding being obtained based on the system information.

9. The method according to claim 1, according to which the useful message is intended to be sent to at least one other terminal.

10. A method for attaching a terminal to a communication network, comprising: - broadcasting (221) by the network system information, the system information comprising the identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier, - verifying (222) receiving, on at least one of said time-frequency resources identified on the basis of said system information, called specific resources, a first piece of information representing a unique identifier of said terminal carried by a request for access to said network, - if the first piece of information representing the unique identifier of the terminal is received, sending (223) a response to the access request to the terminal, the response carrying a second piece of information representing the unique identifier of the terminal, wherein the verification (222) further verifies that a useful message intended to be sent to at least one other terminal is received on the specific resource or on at least one time-frequency resource capable of carrying a useful message identified based on the system information, And wherein the method comprises: if the first piece of information representing the unique identifier of the terminal and the useful message are received, sending the useful message.

11. The method according to claim 10, further comprising: - verifying that the preamble carried by the access request is received on the specific resource or on at least one time-frequency resource capable of carrying a preamble identified based on the system information, - If the preamble is received and the first piece of information representing the identifier of the terminal is not received, sending a response to the access request to the terminal, the response carrying a piece of information representing the preamble and identifying a new specific time-frequency resource.

12. Method according to any one of claims 10 to 11, according to which the useful message is intended to be sent to at least one other terminal.

13. A terminal, comprising at least one processing unit, wherein the at least one processing unit is configured to: - receiving (211) system information broadcast by a communication network that the terminal wishes to access, the system information comprising an identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier, - sending (212) a request to the network for access to the network, the access request carrying a first piece of information representing a unique identifier of the terminal, the first piece of information being sent on at least one of the time-frequency resources identified based on the system information, referred to as a specific resource, - receiving (213) a response to the access request, in which case the terminal's access to the network is authorized, the response carrying a second piece of information representative of a unique identifier of the terminal, The access request further carries a useful message sent on the specific resource or on at least one time-frequency resource capable of carrying a useful message, and the at least one time-frequency resource is identified based on the system information.

14. A base station of a communication network, comprising at least one processing unit, wherein the at least one processing unit is configured to: - broadcasting (221) system information comprising an identification of at least one time-frequency resource capable of carrying a piece of information related to a unique terminal identifier, - verifying (222) receiving, on at least one of said time-frequency resources identified on the basis of said system information, called specific resources, a first piece of information representing a unique identifier of said terminal carried by a request for access to said network, - if the first piece of information representing the identifier of the terminal is received, sending (223) to the terminal a response to the access request, the response carrying a second piece of information representing the unique identifier of the terminal, wherein the verification (222) further verifies that a useful message intended to be sent to at least one other terminal is received on the specific resource or on at least one time-frequency resource capable of carrying a useful message identified based on the system information, And wherein the at least one processing unit is configured to: if the first piece of information representing the unique identifier of the terminal and the useful message are received, send the useful message.

15. A computer readable medium having stored thereon a computer program, the computer program comprising instructions for implementing the method according to any one of claims 1 to 12 when the program is executed by a processor.

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