JP6144442B1 - Communication control method and base station - Google Patents

Abstract

The communication control method according to the first feature is used in a cellular communication system including the UE 100 that operates in one of a connected state and an idle state. The communication control method includes a step in which the UE 100 performs a random access procedure for a cell in an idle state. The steps of performing the random access procedure include a step in which the UE 100 transmits a small amount of data to the cell, and a step in which the UE 100 ends the random access procedure without transitioning to a connected state after transmitting the small amount of data. Including. [Selection] Figure 8

Description

  The present invention relates to a communication control method and a base station used in a cellular communication system.

  A user terminal used in a cellular communication system operates in either a connected state or an idle state. The user terminal transmits and receives data (user data and control signals) to and from the cell in the connected state. On the other hand, in the idle state, the user terminal periodically monitors the paging channel without transmitting / receiving data in order to suppress battery consumption.

  In addition, a user terminal in an idle state needs to perform a random access procedure for a cell in order to transition to a connected state (see Non-Patent Document 1, for example). The user terminal establishes synchronization with a cell by a random access procedure, and is assigned a terminal identifier that is an identifier of the user terminal in the cell. The user terminal that has transitioned to the connected state by the random access procedure can transmit and receive data to and from the cell.

3GPP Technical Specification “TS36.300 V11.5.0” March 2013

  By the way, even when the user terminal in the idle state transmits a small amount of data such as a control signal to the cell, the user terminal cannot transmit the small amount of data to the cell unless the user terminal transits to the connected state by the random access procedure.

  However, there is a problem that it is not efficient from the viewpoint of the load on the network and the battery consumption of the user terminal that the user terminal transitions to the connected state only to transmit a small amount of data to the cell.

  Therefore, an object of the present invention is to enable a small amount of data to be efficiently transmitted from a user terminal in an idle state to a cell.

  The communication control method according to the first feature is used in a cellular communication system including a user terminal that operates in either a connected state or an idle state. The communication control method includes a step in which the user terminal performs a random access procedure for a cell in the idle state. The step of performing the random access procedure includes a step in which the user terminal transmits a small amount of data to the cell, and the user terminal transmits the small amount of data and then the random number without transitioning to the connection state. Ending the access procedure.

  The user terminal according to the second feature operates in either a connected state or an idle state. The said user terminal is provided with the control part which performs the random access procedure with respect to a cell in the said idle state. The control unit transmits a small amount of data to the cell when performing the random access procedure. After transmitting the small amount of data, the control unit ends the random access procedure without transitioning to the connection state.

  A processor according to a third feature is provided in a user terminal that operates in either a connected state or an idle state. The processor performs a random access procedure for the cell in the idle state. The processor transmits a small amount of data to the cell when performing the random access procedure. After transmitting the small amount of data, the processor ends the random access procedure without transitioning to the connection state.

  According to the present invention, it is possible to efficiently transmit a small amount of data to a cell from a user terminal in an idle state.

It is a system configuration figure concerning a 1st embodiment and a 2nd embodiment. It is a block diagram of UE (user terminal) concerning a 1st embodiment and a 2nd embodiment. It is a block diagram of eNB (base station) which concerns on 1st Embodiment and 2nd Embodiment. It is a block diagram of AP (access point) which concerns on 1st Embodiment and 2nd Embodiment. It is a protocol stack figure of the radio | wireless interface which concerns on 1st Embodiment and 2nd Embodiment. It is a block diagram of the radio | wireless frame which concerns on 1st Embodiment and 2nd Embodiment. It is a figure for demonstrating the operating environment which concerns on 1st Embodiment and 2nd Embodiment. It is an operation | movement sequence diagram which concerns on 1st Embodiment. It is an operation | movement sequence diagram which concerns on 2nd Embodiment.

[Outline of Embodiment]
The communication control method according to the first embodiment and the second embodiment is used in a cellular communication system including a user terminal that operates in either a connected state or an idle state. The communication control method includes a step in which the user terminal performs a random access procedure for a cell in the idle state. The step of performing the random access procedure includes a step in which the user terminal transmits a small amount of data to the cell, and the user terminal transmits the small amount of data and then the random number without transitioning to the connection state. Ending the access procedure.

  In the first embodiment and the second embodiment, the communication control method holds a terminal identifier assigned to the user terminal by the user terminal and the cell before the step of performing the random access procedure. The method further includes a step. The terminal identifier held by the user terminal and the cell is used to identify the user terminal in the step of performing the random access procedure.

  In the first embodiment, the step of performing the random access procedure includes the step of transmitting a random access signal including information indicating that the user terminal transmits the small amount of data to the cell, and the user terminal includes: Receiving a random access response, which is a response to the random access signal, from the cell. The step of transmitting the small amount of data includes a step in which the user terminal transmits the terminal identifier together with the small amount of data to the cell in response to receiving the random access response.

  In the second embodiment, the communication control method includes, before the step of performing the random access procedure, a parameter identifier indicating a parameter to be applied to a random access signal transmitted from the user terminal to the cell. Receiving, and further comprising the step of the user terminal and the cell holding the parameter identifier. The step of performing the random access procedure includes a step of transmitting the random access signal including the small amount of data to the cell, to which the user terminal applies the parameter indicated by the parameter identifier.

  In the first embodiment and the second embodiment, in the communication control method, before the step of performing the random access procedure, the user terminal supporting wireless LAN communication establishes a connection with a wireless LAN access point. And a step of transitioning to the idle state. The step of performing the random access procedure further includes the step of the user terminal transmitting the small amount of data to the cell while maintaining a connection with the wireless LAN access point.

  In the first embodiment and the second embodiment, the small amount data is a control signal indicating a communication status of the wireless LAN communication.

  The user terminals according to the first embodiment and the second embodiment operate in either a connected state or an idle state. The said user terminal is provided with the control part which performs the random access procedure with respect to a cell in the said idle state. The control unit transmits a small amount of data to the cell when performing the random access procedure. After transmitting the small amount of data, the control unit ends the random access procedure without transitioning to the connection state.

  The processor which concerns on 1st Embodiment and 2nd Embodiment is provided in the user terminal which operate | moves in any state among a connection state and an idle state. The processor performs a random access procedure for the cell in the idle state. The processor transmits a small amount of data to the cell when performing the random access procedure. After transmitting the small amount of data, the processor ends the random access procedure without transitioning to the connection state.

[First Embodiment]
Hereinafter, an embodiment in the case where a cellular communication system (LTE system) configured in conformity with the 3GPP standard is linked with a wireless LAN (WLAN) system will be described with reference to the drawings.

(System configuration)
FIG. 1 is a system configuration diagram according to the first embodiment. As shown in FIG. 1, the cellular communication system includes a plurality of UEs (User Equipment) 100, an E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core) 20. The E-UTRAN 10 corresponds to a radio access network. The EPC 20 corresponds to a core network.

  The UE 100 is a mobile radio communication device, and performs radio communication with a cell that has established a connection. UE100 is corresponded to a user terminal. The UE 100 is a terminal (dual terminal) that supports both cellular communication and WLAN communication methods.

  The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Node-B). The eNB 200 corresponds to a cellular base station. The eNB 200 manages one or a plurality of cells, and performs radio communication with the UE 100 that has established a connection with the own cell. Note that “cell” is used as a term indicating a minimum unit of a radio communication area, and is also used as a term indicating a function of performing radio communication with the UE 100. The eNB 200 has, for example, a radio resource management (RRM) function, a user data routing function, and a measurement control function for mobility control and scheduling.

  The eNB 200 is connected to each other via the X2 interface. Moreover, eNB200 is connected with MME / S-GW500 contained in EPC20 via S1 interface.

  The EPC 20 includes a plurality of MME (Mobility Management Entity) / S-GW (Serving-Gateway) 500. The MME is a network node that performs various types of mobility control for the UE 100, and corresponds to a control station. The S-GW is a network node that performs transfer control of user data, and corresponds to an exchange.

  The WLAN system includes a WLAN access point (hereinafter referred to as “AP”) 300. The WLAN system is configured in accordance with, for example, IEEE 802.11 standards. The AP 300 communicates with the UE 100 in a frequency band (WLAN frequency band) different from the cellular frequency band. The AP 300 is connected to the EPC 20 via a router or the like.

  Moreover, not only when eNB200 and AP300 are arrange | positioned separately, eNB200 and AP300 may be arrange | positioned (Collocated) in the same place. As one form of Collated, the eNB 200 and the AP 300 may be directly connected by an arbitrary interface of the operator.

  Next, configurations of the UE 100, the eNB 200, and the AP 300 will be described.

  FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100 includes antennas 101 and 102, a cellular communication unit 111, a WLAN communication unit 112, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, and a memory. 150 and a processor 160. The memory 150 and the processor 160 constitute a control unit. The UE 100 may not have the GNSS receiver 130. Further, the memory 150 may be integrated with the processor 160, and this set (that is, a chip set) may be used as the processor 160 '.

  The antenna 101 and the cellular communication unit 111 are used for transmitting and receiving cellular radio signals. The cellular communication unit 111 converts the baseband signal output from the processor 160 into a cellular radio signal and transmits it from the antenna 101. In addition, the cellular communication unit 111 converts a cellular radio signal received by the antenna 101 into a baseband signal and outputs it to the processor 160.

  The antenna 102 and the WLAN communication unit 112 are used for transmission / reception of a WLAN radio signal. The WLAN communication unit 112 converts the baseband signal output from the processor 160 into a WLAN radio signal and transmits it from the antenna 102. In addition, the WLAN communication unit 112 converts the WLAN radio signal received by the antenna 102 into a baseband signal and outputs the baseband signal to the processor 160.

  The user interface 120 is an interface with a user who owns the UE 100, and includes, for example, a display, a microphone, a speaker, and various buttons. The user interface 120 receives an input from the user and outputs a signal indicating the content of the input to the processor 160. The GNSS receiver 130 receives a GNSS signal and outputs the received signal to the processor 160 in order to obtain position information indicating the geographical position of the UE 100. The battery 140 stores power to be supplied to each block of the UE 100.

  The memory 150 stores a program executed by the processor 160 and information used for processing by the processor 160. The processor 160 includes a baseband processor that performs modulation / demodulation and encoding / decoding of a baseband signal, and a CPU that executes programs stored in the memory 150 and performs various processes. The processor 160 may further include a codec that performs encoding / decoding of an audio / video signal. The processor 160 executes various processes and various communication protocols described later.

  FIG. 3 is a block diagram of the eNB 200. As illustrated in FIG. 3, the eNB 200 includes an antenna 201, a cellular communication unit 210, a network interface 220, a memory 230, and a processor 240. The memory 230 and the processor 240 constitute a control unit.

  The antenna 201 and the cellular communication unit 210 are used for transmitting and receiving cellular radio signals. The cellular communication unit 210 converts the baseband signal output from the processor 240 into a cellular radio signal and transmits it from the antenna 201. In addition, the cellular communication unit 210 converts a cellular radio signal received by the antenna 201 into a baseband signal and outputs it to the processor 240.

  The network interface 220 is connected to the neighboring eNB 200 via the X2 interface, and is connected to the MME / S-GW 500 via the S1 interface. The network interface 220 is used for communication with the AP 300 via the EPC 20.

  The memory 230 stores a program executed by the processor 240 and information used for processing by the processor 240. The processor 240 includes a baseband processor that performs modulation / demodulation and encoding / decoding of a baseband signal, and a CPU that executes a program stored in the memory 230 and performs various processes. The processor 240 executes various processes and various communication protocols described later.

  FIG. 4 is a block diagram of the AP 300. As illustrated in FIG. 4, the AP 300 includes an antenna 301, a WLAN communication unit 311, a network interface 320, a memory 330, and a processor 340.

  The antenna 301 and the WLAN communication unit 311 are used for transmission / reception of WLAN radio signals. The WLAN communication unit 311 converts the baseband signal output from the processor 340 into a WLAN radio signal and transmits it from the antenna 301. In addition, the WLAN communication unit 311 converts the WLAN radio signal received by the antenna 301 into a baseband signal and outputs the baseband signal to the processor 340.

  The network interface 320 is connected to the EPC 20 via a router or the like. The network interface 320 is used for communication with the eNB 200 via the EPC 20.

  The memory 330 stores a program executed by the processor 340 and information used for processing by the processor 340. The processor 340 includes a baseband processor that performs modulation / demodulation and encoding / decoding of the baseband signal, and a CPU that executes programs stored in the memory 330 and performs various processes.

  FIG. 5 is a protocol stack diagram of a radio interface in the LTE system. As shown in FIG. 5, the radio interface protocol is divided into the first to third layers of the OSI reference model, and the first layer is a physical (PHY) layer. The second layer includes a MAC (Media Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer. The third layer includes an RRC (Radio Resource Control) layer.

  The physical layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the physical layer of UE100 and the physical layer of eNB200, user data and a control signal are transmitted via a physical channel.

  The MAC layer performs data priority control, retransmission processing by hybrid ARQ (HARQ), random access procedure, and the like. Between the MAC layer of the UE 100 and the MAC layer of the eNB 200, user data and control signals are transmitted via a transport channel. The MAC layer of the eNB 200 includes a scheduler that determines an uplink / downlink transport format (transport block size, modulation / coding scheme) and an allocation resource block to the UE 100. Details of the random access procedure will be described later.

  The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and the physical layer. Between the RLC layer of the UE 100 and the RLC layer of the eNB 200, user data and control signals are transmitted via a logical channel.

  The PDCP layer performs header compression / decompression and encryption / decryption.

  The RRC layer is defined only in the control plane that handles control signals. Control signals (RRC messages) for various settings are transmitted between the RRC layer of the UE 100 and the RRC layer of the eNB 200. The RRC layer controls the logical channel, the transport channel, and the physical channel according to establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 is in a connected state, otherwise, the UE 100 is in an idle state.

  A NAS (Non-Access Stratum) layer located above the RRC layer performs session management, mobility management, and the like.

  FIG. 6 is a configuration diagram of a radio frame used in the LTE system. In the LTE system, OFDMA (Orthogonal Frequency Division Multiplexing Access) is applied to the downlink and SC-FDMA (Single Carrier Frequency Multiple Access) is applied to the uplink.

  As shown in FIG. 6, the radio frame is composed of 10 subframes arranged in the time direction. Each subframe is composed of two slots arranged in the time direction. The length of each subframe is 1 ms, and the length of each slot is 0.5 ms. Each subframe includes a plurality of resource blocks (RB) in the frequency direction and includes a plurality of symbols in the time direction. Each resource block includes a plurality of subcarriers in the frequency direction. Among radio resources allocated to the UE 100, a frequency resource can be specified by a resource block, and a time resource can be specified by a subframe (or slot).

  In the downlink, the section of the first few symbols of each subframe is an area mainly used as a physical downlink control channel (PDCCH) for transmitting a control signal. The remaining section of each subframe is an area that can be used as a physical downlink shared channel (PDSCH) mainly for transmitting user data.

  In the uplink, both ends in the frequency direction in each subframe are regions used mainly as physical uplink control channels (PUCCH) for transmitting control signals. The 6 resource blocks in the center in the frequency direction in each subframe are areas that can be used as physical random access channels (PRACH) for transmitting random access signals. The other part in each subframe is an area that can be used mainly as a physical uplink shared channel (PUSCH) for transmitting user data.

(Random access procedure)
The UE 100 in the idle state needs to perform a random access procedure for the cell in order to transition to the connected state. Hereinafter, a general random access procedure in the LTE system will be described.

  Prior to random access, the UE 100 establishes downlink synchronization with the cell of the eNB 200 by cell search. One purpose of random access is to establish uplink synchronization with the cell.

  As the first process of the random access procedure, the UE 100 transmits a random access signal to the eNB 200 on the PRACH. The random access signal is a signal for performing random access from the UE 100 to the eNB 200 in the MAC layer. The random access signal is referred to as a random access preamble in the specification.

  Resources used for transmission of random access signals (hereinafter referred to as “random access resources”) include a random access signal signal sequence and random access signal transmission timing.

  When UE100 in an idle state performs random access, UE100 selects a random access resource based on the broadcast information received from eNB200. The broadcast information includes a master information block (MIB) and a system information block (SIB). UE100 transmits a random access signal to eNB200 using the selected random access resource. Such random access is referred to as “contention base”.

  As the second process of the random access procedure, the eNB 200 estimates the uplink delay with the UE 100 based on the random access signal received from the UE 100. Moreover, eNB200 determines the radio | wireless resource allocated to UE100. Then, the eNB 200 transmits a random access response to the UE 100. The random access response includes a timing correction value based on a delay estimation result, information on the determined allocated radio resource, information indicating a signal sequence of a random access signal received from the UE 100, and a temporary terminal identifier (TC-RNTI) allocated to the UE 100. : Temporary Cell-Radio Network Temporary Identifier).

  When the UE 100 receives a random access response including information corresponding to the random access signal within a predetermined time after transmitting the random access signal, the UE 100 determines that the random access is successful. Otherwise, the UE 100 determines that a random access failure has occurred and performs the first process again. The UE 100 sets higher transmission power than that at the time of the first random access signal transmission in order to increase the success rate of the random access at the time of the second random access signal transmission.

  As the third process of the random access procedure, the UE 100 that has determined that the random access is successful, based on the information included in the random access response, sends an RRC connection request message to the eNB 200 to request establishment of the RRC connection in the RRC layer. Send. The RRC connection request message includes the identifier of the source UE 100.

  As the fourth process of the random access procedure, the eNB 200 transmits a response message to the UE 100 to the RRC connection request message. The response message includes the identifier of the destination UE 100. When contention due to using the same random access resource occurs, a plurality of UEs 100 may respond to the same random access response, but such contention is solved by the fourth process. The UE 100 to which the terminal identifier (C-RNTI: Cell-Network Temporary Identifier) in the cell is not assigned at this time continues to use the TC-RNTI as the C-RNTI.

(Operation according to the first embodiment)
Next, an operation according to the first embodiment will be described.

(1) Operating Environment FIG. 7 is a diagram for explaining the operating environment according to the first embodiment. As illustrated in FIG. 7, an AP 300 is provided in the coverage area of the eNB 200. The AP 300 is, for example, an AP (Operator controlled AP) managed by an operator of the cellular communication system. In addition, UE 100 is located in the coverage area of eNB 200 and in the coverage area of AP 300.

  First, the UE 100 establishes an RRC connection with the eNB 200 and performs cellular communication with the eNB 200. Specifically, the UE 100 transmits and receives a cellular radio signal including traffic (user data) to and from the eNB 200. When eNB200 establishes RRC connection with many UE100, the load level of eNB200 becomes high. A load level means the congestion degree of eNB200, such as the traffic load of eNB200, or the radio | wireless resource usage rate of eNB200.

  Secondly, the UE 100 establishes a connection with the AP 300 based on its own determination or an instruction from the eNB 200, and releases the RRC connection with the eNB 200. In this way, the traffic load of the eNB 200 can be shifted (offloaded) to the AP 300 by switching the traffic transmitted / received between the eNB 200 and the UE 100 to be transmitted / received between the AP 300 and the UE 100. During the execution of such offloading, the UE 100 enters an idle state for cellular communication.

  During execution of offloading, it is preferable that the eNB 200 can grasp the status of the UE 100 by receiving a report on the status of the UE 100 (such as the communication status of WLAN communication) from the UE 100. However, since the UE 100 that has established a connection with the AP 300 is in an idle state, data cannot be transmitted / received to / from the cell of the eNB 200 unless the UE 100 transitions to the connected state by the random access procedure.

  However, it is not efficient from the viewpoint of the load on the network and the battery consumption of the UE 100 that the UE 100 transitions to the connected state only for the UE 100 to transmit to the cell. Hereinafter, a method for efficiently transmitting a small amount of data from the UE 100 in the idle state to the cell will be described.

(2) Communication control method according to the first embodiment The communication control method according to the first embodiment is used in a cellular communication system including the UE 100 operating in either a connected state or an idle state. The communication control method according to the first embodiment includes a step in which the UE 100 performs a random access procedure for a cell in an idle state. The steps of performing the random access procedure include a step in which the UE 100 transmits a small amount of data to the cell, and a step in which the UE 100 ends the random access procedure without transitioning to a connected state after transmitting the small amount of data. Including. The small amount of data is data that the UE 100 transmits, for example, on a single basis. The small amount of data may be a control signal or user data. In the first embodiment, a case where a small amount of data is a control signal will be mainly described.

  As described above, in the first embodiment, the UE 100 in the idle state transmits a small amount of data to the cell in the course of the random access procedure, and ends the random access procedure without transitioning to the connected state. A small amount of data can be transmitted to the cell while maintaining the idle state.

  The communication control method according to the first embodiment further includes a step in which the UE 100 and the cell hold the C-RNTI assigned to the UE 100 before the step of performing the random access procedure. C-RNTI which UE100 and a cell hold | maintain is utilized in order to identify UE100 in the step which performs a random access procedure.

  Thereby, C-RNTI can be utilized in UE100 in an idle state. Moreover, the cell (eNB 200) can grasp the UE 100 that performs the random access procedure to transmit a small amount of data.

  In the first embodiment, the steps of performing the random access procedure are a step of transmitting a random access signal including information indicating that the UE 100 transmits a small amount of data to the cell, and the UE 100 is a response to the random access signal. Receiving a random access response from the cell. The step of transmitting the small amount of data includes the step of transmitting the C-RNTI together with the small amount of data to the cell by the UE 100 in response to receiving the random access response.

  Thereby, eNB200 can grasp | ascertain that the random access procedure for transmitting a small amount of data was started based on a random access signal, and can handle it differently from a normal random access procedure. Moreover, eNB200 can identify UE100 of the transmission source of small amount data by receiving C-RNTI with small amount data.

  The communication control method according to the first embodiment further includes a step in which the UE 100 supporting WLAN communication establishes a connection with the AP 300 and transitions to an idle state before the step of performing the random access procedure. The step of performing the random access procedure further includes the step of the UE 100 transmitting a small amount of data to the cell while maintaining the connection with the AP 300.

  Thereby, the cell (eNB 200) can receive a small amount of data from the UE 100 being offloaded, and can grasp the situation of the UE 100.

  In the first embodiment, the small amount of data is a control signal indicating the communication status of WLAN communication. The communication status of the WLAN communication is, for example, a reception strength (RSSI: Received Signal Strength Indicator) of a signal received by the UE 100 from the AP 300, a load level of the AP 300, or the like.

  Thereby, the cell (eNB 200) can grasp the communication status of the WLAN communication in the UE 100 during the offload.

(3) Operation Sequence According to First Embodiment FIG. 8 is an operation sequence diagram according to the first embodiment.

  As shown in FIG. 8, in step S101, the UE 100 is in a state (connection state) where an RRC connection with the eNB 200 is established.

  In step S102, the eNB 200 transmits a connection release request for requesting release of the RRC connection to the UE 100. In the first embodiment, the connection release request includes a C-RNTI holding flag that is information indicating whether or not to request holding of C-RNTI. The UE 100 receives the connection release request including the C-RNTI holding flag.

  In step S103-1, the UE 100 confirms whether or not the C-RNTI holding flag included in the connection release request is “true” indicating that C-RNTI holding is requested. When the C-RNTI holding flag is “true” (step S103-1: YES), in step S104-1, the UE 100 holds the C-RNTI allocated from the eNB 200.

  In step S103-2, the eNB 200 confirms whether or not the C-RNTI holding flag included in the connection release request is “true” indicating that the holding of the C-RNTI is requested. When the C-RNTI holding flag is “true” (step S103-2: YES), in step S104-2, the eNB 200 holds the C-RNTI assigned to the UE 100.

  In step S105-1, UE100 which changed to the idle state according to a connection release request | requirement transmits / receives traffic with AP300. Thereby, the traffic load of the eNB 200 is reduced (that is, offloaded).

  In step S105-2, the eNB 200 continues monitoring the status of the UE 100 in preparation for a status in which the UE 100 is newly connected to the own cell.

  In step S106, the UE 100 confirms whether or not the C-RNTI is held. When the C-RNTI is held and when it is necessary to transmit a small amount of data to the eNB 200, the UE 100 determines the start of a random access procedure for transmitting the small amount of data. The case where it is necessary to transmit a small amount of data includes a case where a predetermined event (for example, deterioration of communication status with the AP 300) occurs, or a case where a periodic timer expires.

  In steps S107 to S111, the UE 100 performs a random access procedure. First, in step S107, the UE 100 transmits a random access signal including a small amount data transmission flag, which is information indicating that small amount data is transmitted, to the cell. The eNB 200 receives a random access signal including a small amount data transmission flag.

  In step S108, the eNB 200 confirms whether or not the C-RNTI is held. When the C-RNTI is not held, the eNB 200 recognizes that it is a normal random access procedure.

  When C-RNTI is held (step S108: YES), in step S109, the eNB 200 transmits a random access response, which is a response to the random access signal, to the UE 100. The random access response may include information indicating whether or not transmission of a small amount of data is permitted. The UE 100 receives a random access response.

  In step S110, the UE 100 transmits a small amount of data to the eNB 200 in response to reception of the random access response. In the first embodiment, the small amount of data is a control signal indicating the communication status of WLAN communication. UE100 transmits C-RNTI to eNB200 with a small amount of data. The eNB 200 receives a small amount of data and C-RNTI.

  In step S111, the eNB 200 transmits a small amount data transmission response to the UE 100 in response to reception of the small amount data. The small amount data transmission response includes ACK / NACK that is information indicating whether or not the small amount data has been successfully received.

  When the UE 100 receives from the eNB 200 a small amount data transmission response including an ACK indicating that the small amount of data has been successfully received, the UE 100 ends the random access procedure without making a transition to the connected state.

[Second Embodiment]
The second embodiment will be described mainly with respect to differences from the first embodiment. The system configuration and operating environment of the second embodiment are the same as those of the first embodiment.

(1) Communication Control Method According to Second Embodiment The communication control method according to the second embodiment is a parameter that UE 100 should apply to a random access signal transmitted to a cell before the step of performing a random access procedure. Receiving the indicated parameter identifier from the cell, and the UE 100 and the cell holding the parameter identifier. In the second embodiment, the parameter to be applied to the random access signal is a random access resource. The random access resource is defined by ra-PreambleIndex and ra-PRACH-MaskIndex.

  The step of performing the random access procedure includes the step of the UE 100 transmitting a random access signal to which the parameter indicated by the parameter identifier is applied and including a small amount of data to the cell.

  Thus, in the second embodiment, a small amount of data is included in the random access signal. Therefore, as compared with the first embodiment, a small amount of data can be transmitted at the first stage in the random access procedure, and the random access procedure can be terminated earlier. Therefore, the load on the network and the battery consumption of the UE 100 can be further reduced.

(2) Operation Sequence According to Second Embodiment FIG. 9 is an operation sequence diagram according to the second embodiment.

  As shown in FIG. 9, in step S201, the UE 100 is in a state (connection state) where an RRC connection with the eNB 200 is established.

  In step S202, the eNB 200 transmits a connection release request for requesting release of the RRC connection to the UE 100. In the second embodiment, the connection release request includes a C-RNTI holding flag and an RA-RNTI (Random Access-Radio Network Temporary Identifier) that is an identifier indicating a random access resource. The UE 100 receives the connection release request including the C-RNTI holding flag and the RA-RNTI.

  In step S203-1, the UE 100 confirms whether or not the C-RNTI holding flag included in the connection release request is “true” indicating that C-RNTI holding is requested. When the C-RNTI holding flag is “true” (step S203-1: YES), in step S204-1, the UE 100 holds the C-RNTI and RA-RNTI allocated from the eNB 200.

  In step S203-2, the eNB 200 confirms whether or not the C-RNTI holding flag included in the connection release request is “true” indicating that the holding of the C-RNTI is requested. When the C-RNTI holding flag is “true” (step S203-2: YES), in step S204-2, the eNB 200 holds the C-RNTI and RA-RNTI assigned to the UE 100 in association with each other.

  In step S205-1, UE100 which changed to the idle state according to a connection release request | requirement transmits / receives traffic with AP300. Thereby, the traffic load of the eNB 200 is reduced (that is, offloaded).

  In step S205-2, the eNB 200 continues monitoring the status of the UE 100 in preparation for the status where the UE 100 is newly connected to the own cell.

  In step S206, UE100 confirms whether C-RNTI and RA-RNTI are hold | maintained. When it is necessary to transmit a small amount of data to the eNB 200 when the C-RNTI or the RA-RNTI is held, the UE 100 determines the start of a random access procedure for transmitting the small amount of data. The case where it is necessary to transmit a small amount of data includes a case where a predetermined event (for example, deterioration of communication status with the AP 300) occurs, or a case where a periodic timer expires.

  In steps S207 to S212, the UE 100 performs a random access procedure. First, in step S207, the UE 100 transmits a random access signal to which the random access resource indicated by the held RA-RNTI is applied to the eNB 200. In the second embodiment, the random access signal includes a small amount of data. The small amount of data is a control signal indicating the communication status of WLAN communication. The eNB 200 receives a random access signal including a small amount of data.

  In step S208, the eNB 200 confirms whether or not the C-RNTI is held. When the C-RNTI is not held, the eNB 200 recognizes that it is a normal random access procedure.

  When the C-RNTI is held (step S208: YES), in step S209, the eNB 200 determines whether or not the random access resource corresponding to the RA-RNTI allocated in the own cell is applied in the received random access signal. To check. If “No” in step S209, in step S210, the eNB 200 recognizes that it is a normal random access procedure.

  On the other hand, if “Yes” in step S209, the C-RNTI associated with the RA-RNTI corresponding to the received random access signal is specified in step S211. That is, the UE 100 that is the source of the random access signal is identified. Thereby, eNB200 can grasp | ascertain the transmission origin UE of the small amount data contained in the random access signal.

  In step S212, the eNB 200 transmits a small amount data transmission response to the UE 100 in response to reception of the small amount data. The small amount data transmission response includes ACK / NACK that is information indicating whether or not the small amount data has been successfully received.

  When the UE 100 receives from the eNB 200 a small amount data transmission response including an ACK indicating that the small amount of data has been successfully received, the UE 100 ends the random access procedure without making a transition to the connected state.

[Other Embodiments]
In the first embodiment and the second embodiment described above, the eNB 200 includes a transmission trigger for a small amount of data and / or a data type to be transmitted as a small amount of data in the connection release request for requesting the release of the RRC connection. May be. Thereby, transmission of a small amount of data can be controlled more flexibly.

  In the first embodiment and the second embodiment described above, it is assumed that the UE 100 reconnects to the eNB 200 after switching the connection from the eNB 200 to the AP 300. However, for example, when the AP 300 is installed at the end of the coverage area of the eNB 200, the UE 100 may connect to another eNB 200 after switching the connection from the eNB 200 to the AP 300. Therefore, when the UE 100 in an idle state connected to the AP 300 tries to connect to another eNB 200 (or when cell reselection is performed), the UE 100 may transmit a control signal indicating that to the eNB 200 as a small amount of data. In that case, the UE 100 and the eNB 200 may discard the retained C-RNTI (and RA-RNTI). Note that the UE 100 and the eNB 200 may discard the retained C-RNTI (and RA-RNTI) after a predetermined time has elapsed since the start of offloading to the AP 300.

  In the first embodiment and the second embodiment described above, a case has been described in which the UE 100 in the idle state performs WLAN communication with the AP 300. However, the UE 100 in the idle state may not perform WLAN communication with the AP 300. For example, the UE 100 in the idle state may perform D2D (Device to Device) communication with another UE 100. D2D communication is a communication mode in which a plurality of neighboring UEs 100 perform direct inter-terminal communication without going through a core network. The UE 100 performing D2D communication in the idle state transmits a control signal (small amount of data) indicating the communication status of the D2D communication to the cell of the eNB 200, so that the eNB 200 can grasp the communication status of the D2D communication.

  In the above-described embodiment, the LTE system has been described as an example of the cellular communication system. However, the present invention is not limited to the LTE system, and the present invention may be applied to a system other than the LTE system.

  DESCRIPTION OF SYMBOLS 10 ... E-UTRAN, 20 ... EPC, 100 ... UE, 101, 102 ... Antenna, 111 ... Cellular communication part, 112 ... WLAN communication part, 120 ... User interface, 130 ... GNSS receiver, 140 ... Battery, 150 ... Memory , 160 ... processor, 200 ... eNB, 201 ... antenna, 210 ... cellular communication unit, 220 ... network interface, 230 ... memory, 240 ... processor, 300 ... AP, 301 ... antenna, 311 ... WLAN communication unit, 320 ... network interface , 330 ... Memory, 340 ... Processor, 500 ... MME / S-GW

Claims (2)

A communication control method used in a cellular communication system including a user terminal that operates in either a connected state or an idle state,
A base station transmits a connection release request message requesting release of an RRC connection to the user terminal, and the connection release request message is information indicating that the base station requests holding of an identifier assigned to the user terminal. Including steps, and
The base station performing a random access procedure with the user terminal holding the identifier in the idle state, and
Performing the random access procedure comprises:
The base station receiving a random access signal from the user terminal;
The base station transmitting a random access response, which is a response to the random access signal, to the user terminal;
The base station receiving the identifier together with a small amount of data from the user terminal in the idle state. A base station used in a cellular communication system including a user terminal that operates in either a connected state or an idle state, comprising a control unit, the control unit,
A connection release request message requesting release of an RRC connection is transmitted to the user terminal, and the connection release request message includes information indicating that the base station requests to hold an identifier assigned to the user terminal. When,
Performing a random access procedure with the user terminal holding the identifier in the idle state,
The process of performing the random access procedure is as follows:
Receiving a random access signal from the user terminal;
A process of transmitting a random access response, which is a response to the random access signal, to the user terminal;
And a process of receiving the identifier together with a small amount of data from the user terminal in the idle state.

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