Communication control method, remote user device, and processor

Abstract

To provide a communication control method, a relay user equipment, and a remote user equipment for use in a cellular communication system.SOLUTION: A method includes: receiving, by a lower layer of a remote user equipment UE 100A, a PC5-RRC message containing information indicating a radio link failure (RLF) between a first relay user equipment UE 100B relaying data of the remote user equipment and a network from the first relay user equipment; and notifying, by the lower layer of the remote user equipment, an upper layer of the remote user equipment based on the information indicating the RLF. The upper layer of the remote user equipment is a layer that performs settings related to discovery of the relay user equipment that has the ability to relay data of the remote user equipment.SELECTED DRAWING: Figure 16

Description

Technical Field

[0001] The present invention relates to a communication control method, a relay user device, and a remote user device used in a cellular communication system.

Background Art

[0002] In recent years, the 5th generation (5G) cellular communication system has attracted attention. In NR (New Radio), which is a radio access technology (RAT) of the 5G system, sidelink communication in which user devices directly perform wireless communication with each other has been introduced.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

[0004] The communication control method according to the first aspect is a communication control method used in a cellular communication system, wherein a relay user device having the ability to relay data of a remote user device transmits a message including information about the relay user device; the remote user device receives the message; and the remote user device performs a process for establishing a sidelink connection between the remote user device and the relay user device based on the message.

[0005] The relay user device according to the second aspect is a relay user device having the ability to relay data of a remote user device in a cellular communication system, and includes a transmission unit that transmits a message including information about the relay user device to the remote user device. The message is used for a process for establishing a sidelink connection between the remote user device and the relay user device.

[0006] A remote user device according to a third embodiment is a remote user device used in a cellular communication system, comprising: a receiving unit that receives a message containing information about the relay user device from a relay user device having the capability to relay data from the remote user device; and a control unit that performs processing to establish a sidelink connection between the remote user device and the relay user device based on the message. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram shows the configuration of a cellular communication system according to one embodiment. [Figure 2] This diagram shows the configuration of a UE (User Equipment) according to one embodiment. [Figure 3] This diagram shows the configuration of a gNB (base station) according to one embodiment. [Figure 4] This diagram shows the protocol stack configuration of the user plane wireless interface that handles data. [Figure 5] This diagram shows the protocol stack configuration of the wireless interface of the control plane that handles signaling (control signals). [Figure 6] This figure shows a side link relay according to one embodiment. [Figure 7] This figure shows the overall flow of a sidelink relay according to one embodiment. [Figure 8] This diagram shows the configuration of the protocol stack for the user plane sidelink that handles data. [Figure 9] This diagram shows the configuration of the protocol stack for the control plane sidelink that handles signaling (control signals). [Figure 10] This figure shows a relay UE message according to one embodiment. [Figure 11] This figure shows the sequence of the relay UE selection procedure according to one embodiment. [Figure 12] This figure shows the sequence of the relay UE reselection procedure according to one embodiment. [Figure 13] This figure shows operation pattern 1 of sidelink communication control by a remote UE according to one embodiment. [Figure 14] This figure shows an operation pattern 2 of sidelink communication control by a remote UE according to one embodiment. [Figure 15] This figure shows an example of changing the operation pattern 2 of sidelink communication control by a remote UE according to one embodiment. [Figure 16] This figure shows sidelink communication control by a relay UE according to one embodiment. [Modes for carrying out the invention]

[0008] Sidelink relay is being considered, in which a relay user device relays data from a remote user device using sidelink communication. The remote user device can use sidelink relay by selecting a relay user device and establishing a sidelink connection. However, if the remote user device cannot select an appropriate relay user device, sidelink communication cannot be performed properly.

[0009] Therefore, this disclosure aims to enable proper sidelink communication.

[0010] A cellular communication system according to an embodiment will be described with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0011] (Configuration of a cellular communication system) First, the configuration of a cellular communication system according to one embodiment will be described. Figure 1 is a diagram showing the configuration of a cellular communication system according to one embodiment. This cellular communication system conforms to the 5th Generation System (5GS) of the 3GPP® standard. In the following description, 5GS will be used as an example, but the cellular communication system may also incorporate at least partially the LTE (Long Term Evolution) system.

[0012] As shown in FIG. 1, a cellular communication system includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. The radio access network and the core network are collectively referred to as a cellular communication network.

[0013] The UE 100 is a mobile wireless communication device. The UE 100 can be any device used by a user. For example, the UE 100 can be a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in the sensor, a vehicle or a device provided in the vehicle (Vehicle UE), an aircraft or a device provided in the aircraft (Aerial UE).

[0014] The NG-RAN 10 includes base stations (referred to as "gNB" in a 5G system) 200. The gNBs 200 are interconnected via an Xn interface which is a base station-to-base station interface. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with the UE 100 that has established a connection with its cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, etc. "Cell" is used as a term indicating the smallest unit of a wireless communication area. "Cell" is also used as a term indicating a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency.

[0015] Note that the gNB can also be connected to an Evolved Packet Core (EPC) which is the core network of LTE. The base station of LTE can also be connected to the 5GC. The base station of LTE and the gNB can also be connected via a base station-to-base station interface.

[0016] 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE100. The AMF manages the mobility of the UE100 by communicating with the UE100 using NAS (Non-Access Stratum) signaling. The UPF performs data transfer control. The AMF and the UPF are connected to the gNB200 via the NG interface, which is an interface between the base station and the core network.

[0017] Figure 2 is a diagram showing the configuration of a UE100 (user device) according to an embodiment.

[0018] As shown in Figure 2, the UE100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130.

[0019] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0020] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmitted signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0021] The control unit 130 performs various controls in the UE100. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of the baseband signal. The CPU executes the programs stored in the memory to perform various processes.

[0022] Figure 3 shows the configuration of a gNB200 (base station) according to one embodiment.

[0023] As shown in Figure 3, the gNB200 comprises a transmitting unit 210, a receiving unit 220, a control unit 230, and a backhaul communication unit 240.

[0024] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0025] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0026] The control unit 230 performs various controls in the gNB200. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing.

[0027] The backhaul communication unit 240 is connected to an adjacent base station via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF300 via a base station-core network interface. The gNB may consist of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally separated), and the two units may be connected via an F1 interface.

[0028] Figure 4 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0029] As shown in Figure 4, the user plane radio interface protocol has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0030] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the UE100's PHY layer and the gNB200's PHY layer via a physical channel.

[0031] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of the UE100 and the MAC layer of the gNB200 via the transport channel. The MAC layer of the gNB200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE100.

[0032] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the UE100's RLC layer and the gNB200's RLC layer via a logical channel.

[0033] The PDCP layer performs header compression / decompression, and encryption / decryption.

[0034] The SDAP layer maps IP flows, which are the units under which the core network performs QoS control, to wireless bearers, which are the units under which the AS (Access Stratum) performs QoS control. Note that if the RAN is connected to the EPC, SDAP may not be necessary.

[0035] Figure 5 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0036] As shown in Figure 5, the protocol stack of the control plane's wireless interface has an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer instead of the SDAP layer shown in Figure 4.

[0037] RRC signaling for various settings is transmitted between the RRC layer of the UE100 and the RRC layer of the gNB200. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC connected state. If there is no connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC idle state. If the connection between the RRC of the UE100 and the RRC of the gNB200 is suspended, the UE100 is in the RRC inactive state.

[0038] The NAS layer, located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the UE100's NAS layer and the AMF300's NAS layer.

[0039] In addition to the wireless interface protocol, the UE100 also has an application layer and other components.

[0040] (Summary of sidelink broadcast) Next, an overview of a side link relay according to one embodiment will be described. Figure 6 is a diagram showing a side link relay according to one embodiment.

[0041] As shown in Figure 6, there are two modes for sidelink relay: UE-to-NW relay (U2N relay) and UE-to-UE relay (U2U relay).

[0042] U2N relay is a mode in which the relay UE100B relays data between the remote UE100A and the gNB200 (cell). In this mode, a sidelink connection is established between the relay UE100B and the remote UE100A, and a network connection is established between the relay UE100B and the gNB200. The sidelink is a direct link between the UE100s and is sometimes called the PC5 interface. The sidelink connection is sometimes called the PC5-S connection or PC5-RRC connection. The network connection refers to the connection between the UE100 and the cellular communication network (gNB200) and is sometimes called the NAS connection, RRC connection, or Uu interface.

[0043] The relay UE100B is located within the coverage of the gNB200 cell (hereinafter simply referred to as "coverage"). On the other hand, the remote UE100A is located outside the coverage. With U2N relay, the remote UE100A, which is outside the coverage (so-called out of range), can communicate via the relay UE100B. However, the remote UE100A may also be located within the coverage.

[0044] U2U relay is a mode in which relay UE100B relays between remote UE100A and other UE100C. Here, sidelink connections are established between relay UE100B and remote UE100A, and between relay UE100B and other UE100C. Remote UE100A, relay UE100B, and other UE100C may each be located within or outside the coverage area. In addition, a sidelink connection may be indirectly established between remote UE100A and other UE100C via relay UE100B.

[0045] According to U2U relay, even if direct sidelink communication between a remote UE100A and another UE100C is not possible outside of coverage, for example, the remote UE100A can indirectly perform sidelink communication via relay UE100B.

[0046] Figure 7 shows the overall flow of sidelink relay according to one embodiment. In the following, it is assumed that the remote UE100A has already established a network connection with the cellular communication network (gNB200) or a sidelink connection with another UE100C.

[0047] As shown in Figure 7, in step S1, the remote UE100A and the relay UE100B perform the relay UE discovery procedure. The relay UE discovery procedure includes a method in which the relay UE100B notifies of its presence by sending a discovery message, and a method in which the remote UE100A searches for the relay UE100B by sending a discovery message. The discovery message sent may be a message specifically for discovery, or it may be an existing message for establishing a sidelink connection. The remote UE100A may send a discovery message indicating its presence, and the relay UE100B may send a discovery message to search for the remote UE100A. Through the relay UE discovery procedure, the remote UE100A discovers the relay UE100B. Here, the remote UE100A may discover multiple candidate relay UE100Bs.

[0048] In step S2, the remote UE100A performs a relay UE selection procedure to select a relay UE100B to relay its data. If only one relay UE100B is found in step S1, the remote UE100A may select that one relay UE100B in the relay UE selection procedure depending on whether the discovered relay UE100B meets predetermined conditions. On the other hand, if multiple relay UE100B are found in step S1, the remote UE100A may select one relay UE100B from among the discovered relay UE100B in the relay UE selection procedure. Details of the relay UE selection procedure will be described later.

[0049] In step S3, the remote UE100A and relay UE100B perform a sidelink connection establishment procedure to establish a sidelink connection. For example, the sidelink connection is established by the remote UE100A and relay UE100B sending and receiving PC5-RRC layer messages (e.g., RRCReconfigurationSidelink, RRCReconfigurationCompleteSidelink) as described later. This sidelink connection establishment procedure may also include sending and receiving PC5-S layer messages (e.g., DIRECT LINK ESTABLISHMENT REQUEST, DIRECT LINK ESTABLISHMENT ACCEPT) as described later.

[0050] In step S4, the remote UE100A performs sidelink communication with the relay UE100B and sends and receives data with the relay UE100B. The relay UE100B relays the data sent and received by the remote UE100A (sidelink relay).

[0051] In step S5, the remote UE100A may perform the relay UE selection procedure again. Specifically, the remote UE100A may perform the relay UE reselection procedure to switch from the current relay UE100B to another relay UE100B.

[0052] (Sidelink protocol stack) Next, the configuration of the sidelink protocol stack according to one embodiment will be described.

[0053] Figure 8 shows the configuration of the protocol stack for the user plane sidelink that handles data. As shown in Figure 8, the user plane sidelink protocol has a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer.

[0054] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the remote UE100A and the PHY layer of the relay UE100B via a physical channel.

[0055] The MAC layer performs data priority control and retransmission processing using HARQ. Data and control information are transmitted between the MAC layer of the remote UE100A and the MAC layer of the relay UE100B via the transport channel.

[0056] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the remote UE100A and the RLC layer of the relay UE100B via a logical channel. The PDCP layer performs header compression / decompression and encryption / decryption. The SDAP layer maps IP flows, which are the units under which the core network performs QoS control, to wireless bearers, which are the units under which the AS performs QoS control.

[0057] Figure 9 shows the configuration of the protocol stack of the sidelink of the control plane that handles signaling (control signals).

[0058] As shown in Figure 9, the protocol stack of the control plane sidelink has a PC5-RRC layer and a PC5-S layer instead of the SDAP layer shown in Figure 8.

[0059] PC5-RRC messages for various settings are transmitted between the PC5-RRC layer of the remote UE100A and the PC5-RRC layer of the relay UE100B. If there is a connection (PC5-RRC connection) between the PC5-RRC of the remote UE100A and the PC5-RRC of the relay UE100B, the remote UE100A may be in the PC5-RRC connected state. Note that the PC5-RRC layer is included in the AS layer.

[0060] The PC5-S layer is located above the PC5-RRC layer (AS layer). PC5-S messages, such as discovery messages, are transmitted between the PC5-S layer of the remote UE100A and the PC5-S layer of the relay UE100B.

[0061] (Procedure for selecting a relay UE) Next, the procedure for selecting a relay UE according to one embodiment will be described.

[0062] The remote UE100A can utilize sidelink relay by selecting a relay UE100B and establishing a sidelink connection. However, if the remote UE100A cannot select an appropriate relay UE100B, sidelink communication cannot be performed properly. The relay UE selection procedure according to one embodiment enables the remote UE100A to select an appropriate relay UE100B in the relay UE selection procedure.

[0063] A relay UE selection procedure according to one embodiment includes the steps of: a relay UE 100B having the capability to relay data from a remote UE 100A transmits a message containing information about the relay UE 100B (hereinafter referred to as the "relay UE message"); a remote UE 100A receives the relay UE message; and the remote UE 100A performs processing to establish a sidelink connection between the remote UE 100A and the relay UE 100B based on the relay UE message. For example, the relay UE message is a PC5-RRC message of the PC5-RRC layer or a discovery message of the PC5-S layer.

[0064] If only one relay UE100B is found, the remote UE100A may select that relay UE100B in the relay UE selection procedure based on the relay UE message received from that relay UE100B. Conversely, if multiple relay UE100B are found, the remote UE100A may select one relay UE100B in the relay UE selection procedure based on the relay UE message from each of the multiple relay UE100B.

[0065] Figure 10 shows a relay UE message according to one embodiment.

[0066] As shown in Figure 10, if the relay UE 100B has a network connection to the cellular communication network, the relay UE message includes information indicating the network communication status between the relay UE 100B and the cellular communication network. This allows the remote UE 100A to select or re-select the appropriate relay UE 100B by considering the network communication status between the relay UE 100B and the cellular communication network.

[0067] The relay UE message includes information indicating the sidelink communication status between relay UE100B and other UE100C if relay UE100B has a sidelink connection with other UE100C. This allows remote UE100A to select or re-select the appropriate relay UE100B by considering the sidelink communication status between relay UE100B and other UE100C.

[0068] The relay UE message includes information indicating the relay capabilities of relay UE100B. This allows the remote UE100A to select or re-select the appropriate relay UE100B, taking into account its relay capabilities.

[0069] Specifically, the information indicating the network communication status between the relay UE100B and the cellular communication network includes at least one of the following information elements: • An information element indicating the RRC status (one of RRC Connected, RRC Inactive, or RRC Idle) between the relay UE100B and the cellular communication network; • An information element indicating the coverage status of the relay UE100B (either within coverage or outside coverage); • An information element indicating the wireless status (e.g., RSRP, RSRQ, or SINR) between the relay UE100B and the cellular communication network; • An information element indicating the frequency band used between the relay UE100B and the cellular communication network; For example, the information element may indicate one of the following: Licensed spectrum (a frequency band for which a license has been granted), Unlicensed spectrum (a frequency band that does not require a license), or Shared spectrum (a frequency band that can be shared by multiple systems). The information element may also indicate one of the following: Frequency Range 1 (FR1), which includes frequencies below 6 GHz; Frequency Range 2 (FR2), which includes millimeter waves from 24.25 GHz to 52.6 GHz, which has a narrower communication range than FR1 but a wider frequency bandwidth; or another Frequency Range (FR3, etc.). The information element may also indicate the bandwidth of the frequency band used between the relay UE100B and the cellular communication network (e.g., 100 MHz). • Information elements indicating the link status between the relay UE100B and the cellular communication network (e.g., throughput (data rate) or latency); • An information element that shows the load status (e.g., resource utilization) between the relay UE100B and the cellular communication network.

[0070] On the other hand, information indicating the sidelink communication status between the relay UE100B and other UE100Cs includes at least one of the following information elements: • An information element indicating the operating frequency band between the relay UE100B and other UE100C units; • An information element indicating the wireless status between the relay UE100B and other UE100C devices; The information element may also be RSRP, RSRQ, and SINR for each other UE100C (for each PC5-RRC connection). The information element may also be an information element showing the measurement result of the Channel Busy Ratio (CBR), which indicates the degree of channel congestion between the relay UE100B and other UE100Cs. • An information element indicating the link status between the relay UE100B and other UE100C devices; • An information element that shows the load status between the relay UE100B and other UE100C devices.

[0071] On the other hand, information indicating the relay capability of the relay UE100B includes at least one of the following information elements. It is assumed that this information is held by the upper layer (PC5-S layer): • An information element indicating the relay mode of the relay UE100B (U2N, U2U, or both); The information element may be based on the mode authenticated by the network; • Information elements that show the load status of the relay UE100B (e.g., CPU and memory usage); • An information element indicating the battery status of the relay UE100B (e.g., connected to power, battery in use, or low battery level).

[0072] Figure 11 shows the sequence of the relay UE selection procedure according to one embodiment. An example is shown where there are two candidate relay UEs 100B, but there may be three or more candidate relay UEs 100B.

[0073] As shown in Figure 11, in step S101, relay UE100B#1 sends the relay UE message to remote UE100A.

[0074] If the relay UE message is a discovery message at the PC5-S layer, the AS layer at relay UE100B#1 notifies the upper layer (PC5-S layer) of its own network link status or the link status with the other side (other UE100C). The upper layer (PC5-S layer) generates a discovery message using the status information from the AS layer and its own relay capability information, and sends this discovery message as the relay UE message.

[0075] On the other hand, if the relay UE message is a PC5-RRC message of the PC5-RRC layer, the upper layer (PC5-S layer) in relay UE 100B#1 notifies the AS layer of its relay capability status. The AS layer generates a PC5-RRC message using the relay capability information from the upper layer (PC5-S layer) and its own link status information, and sends this PC5-RRC message as the relay UE message.

[0076] The message format of the PC5-RRC message may be a PC5-RRC message broadcast on the sidelink (e.g., an existing MasterInformationBlockSidelink or a new message). Alternatively, the message format of the PC5-RRC message may be a PC5-RRC message used for establishing a sidelink connection (e.g., RRCReconfigurationSidelink, RRCReconfigurationCompleteSidelink), a PC5-RRC message used for querying and responding on the sidelink (e.g., UECapabilityEnquirySidelink, UECapabilityInformationSidelink), and / or a new query / response message specifically for relaying. With respect to query / response messages, the relay UE message is a response message, and the relay UE sends a relay UE message (response message) in response to a query from a remote UE.

[0077] In step S102, relay UE100B#2 sends the relay UE message to remote UE100A.

[0078] In step S103, the remote UE100A selects one relay UE100B from among the multiple relay UE100B (relay UE100B#1, relay UE100B#2) to establish a sidelink connection based on the relay UE messages of each relay UE100B.

[0079] In such a relay UE selection process, the remote UE 100A may extract selection candidates based on the radio state between the remote UE 100A and each relay UE 100B (e.g., RSRP of the sidelink). The remote UE 100A may rank the candidates by the radio state of the sidelink and select the top n (e.g., top 5 UEs) of relay UE 100B as candidates. Alternatively, the remote UE 100A may select relay UE 100B within a certain range (e.g., within -10dB) based on the radio state of the relay UE 100B with the best radio state, or it may select all relay UE 100B whose radio state is above a threshold (e.g., above -100dBm) as candidates.

[0080] In the relay UE selection process, the remote UE 100A selects one relay UE 100B by comparing the information elements contained in the relay UE messages of multiple candidate relay UE 100B. The information elements used for relay UE selection and the selection criteria (selection priority) may be set by the gNB200, pre-defined (pre-configuration), or set by user preference.

[0081] For example, the remote UE100A may prioritize selecting a relay UE100B that is in the RRC Connected state over a relay UE100B that is not in the RRC Connected state, based on the RRC state included in the network communication state. The remote UE100A may also select a relay UE according to the priority order: RRC Connected state > RRC Inactive state > RRC Idle state.

[0082] The remote UE100A may exclude relay UE100B within coverage or outside coverage from the candidates, depending on the respective uses of U2N and U2U, for the coverage status included in the network communication state. The remote UE100A may also prioritize selecting a relay UE100B within coverage over a relay UE100B outside coverage.

[0083] The remote UE100A may prioritize selecting a relay UE100B with good wireless conditions over a relay UE100B with poor wireless conditions, based on the wireless conditions (RSRP, RSRQ, SINR) included in the network communication state.

[0084] Remote UE100A may prioritize selecting a relay UE100B that uses a licensed spectrum over a relay UE100B that does not use a licensed spectrum for the frequency band included in the network communication state. Remote UE100A may prioritize selecting a relay UE100B that uses FR2 over a relay UE100B that does not use FR2. Remote UE100A may prioritize selecting a relay UE100B that uses a wide bandwidth over a relay UE100B that uses a narrow bandwidth. Note that these priority criteria may also be reversed. For example, remote UE100A may prioritize a relay UE100B that does not use a licensed spectrum, or a relay UE100B that does not use FR2.

[0085] The remote UE100A may prioritize selecting a relay UE100B with high throughput over a relay UE100B with low throughput, based on the link state included in the network communication state. The remote UE100A may also prioritize selecting a relay UE100B with low latency over a relay UE100B with high latency.

[0086] The remote UE100A may prioritize selecting a relay UE100B with a low load over a relay UE100B with a high load, based on the load status included in the network communication state.

[0087] Furthermore, the remote UE100A selects a relay UE for sidelink communication status in the same way as for network communication status. However, regarding the wireless status included in the sidelink communication status, the remote UE100A may prioritize selecting a relay UE100B with good wireless conditions for its communication partner (destination). Also, the remote UE100A may prioritize selecting a relay UE100B with a low CBR measurement value over a relay UE100B with a high CBR measurement value.

[0088] Furthermore, regarding relay capability information, the remote UE100A may prioritize selecting a relay UE100B with a relay mode suitable for its own U2N and U2U applications. The remote UE100A may also prioritize selecting a relay UE100B with a low load (such as CPU and memory usage) over a relay UE100B with a high load. Regarding battery status, the remote UE100A may prioritize selecting a relay UE100B that is connected to a power source.

[0089] When the remote UE100A selects one relay UE100B through the relay UE selection process, in step S104, it performs a sidelink connection establishment process for the selected relay UE100B (in this case, relay UE100B#1).

[0090] Figure 12 shows the sequence of the relay UE re-selection procedure according to one embodiment. Here, we will explain the differences from the relay UE selection procedure described above.

[0091] As shown in Figure 12, in step S151, the remote UE100A has established a sidelink connection with the relay UE100B#1. The remote UE100A may trigger a relay UE reselection if the sidelink wireless state with relay UE100B#1 deteriorates.

[0092] In steps S152 and S153, the remote UE100A receives relay UE messages from relay UE100B#1 and relay UE100B#2, respectively.

[0093] In step S154, the remote UE100A determines whether to switch (re-select) to relay UE100B#2 based on the relay UE messages of relay UE100B#1 and relay UE100B#2. The criteria for such relay UE re-selection are the same as the criteria for relay UE selection described above. Here, we will proceed with the explanation assuming that the remote UE100A has determined to re-select relay UE100B#2.

[0094] In step S154, the remote UE100A performs the sidelink connection establishment process for the re-selected relay UE100B#2. The remote UE100A also releases the sidelink connection with relay UE100B#1.

[0095] (Side link communication control) Next, we will describe the sidelink communication control in the sidelink relay procedure according to one embodiment.

[0096] A remote UE100A with a sidelink connection to a relay UE100B can communicate with a cellular communication network or another UE100C via the relay UE100B. However, after such sidelink communication has started, changes in circumstances such as the movement of the UE100 may occur, which may make it difficult to perform sidelink communication properly.

[0097] One embodiment of sidelink communication control includes the steps of: a remote UE 100A having a sidelink connection with a relay UE 100B determining the network communication status between the remote UE 100A and the cellular communication network (gNB200); and the remote UE 100A performing control regarding sidelink communication between the remote UE 100A and the relay UE 100B based on the network communication status. This allows for appropriate control of sidelink communication between the remote UE 100A and the relay UE 100B.

[0098] One embodiment of sidelink communication control includes the steps of: a relay UE 100B having a sidelink connection with a remote UE 100A determining the communication status between the relay UE 100B and the cellular communication network (gNB200), or the communication status between the relay UE 100B and another UE 100C; and the relay UE 100B performing control regarding sidelink communication between the relay UE 100B and the remote UE 100A based on the determined communication status. This allows for appropriate control of sidelink communication between the remote UE 100A and the relay UE 100B.

[0099] (1) Sidelink communication control via remote UE100A

[0100] (1.1) Operation Pattern 1 An operation pattern 1 of sidelink communication control by remote UE100A according to one embodiment will be described.

[0101] In operation pattern 1 of sidelink communication control by remote UE100A, the remote UE100A, which has a sidelink connection with relay UE100B, detects an improvement in the network communication state between the remote UE100A and the cellular communication network. Then, in response to the detection of this improvement, the remote UE100A performs processing to terminate the sidelink communication between the remote UE100A and relay UE100B.

[0102] As a result, if the network communication status between the remote UE100A and the cellular communication network improves after sidelink relay has started, the remote UE100A can switch from sidelink relay communication to direct communication with the cellular communication network.

[0103] Figure 13 shows operation pattern 1 of sidelink communication control by a remote UE 100A according to one embodiment. In Figure 13, the case where the remote UE 100A, which has a sidelink connection with a relay UE 100B, moves from outside the coverage area to inside the coverage area is mainly assumed. In Figure 13, steps that are not essential are shown with dashed lines.

[0104] As shown in Figure 13, in step S201, the remote UE100A has established a sidelink connection with the relay UE100B. The relay mode of the relay UE100B may be either U2N relay or U2U relay.

[0105] In step S202, the remote UE100A transmits and receives data with the relay UE100B.

[0106] In step S203, the relay UE100B relays the data transmitted and received by the remote UE100A. Figure 13 shows an example in which the relay UE100B transmits and receives relay data with the gNB200, but the relay UE100B may also transmit and receive relay data with other UE100C.

[0107] In step S204, the remote UE100A determines the network communication status between the remote UE100A and the cellular communication network (gNB200) and detects any changes in the network communication status.

[0108] For example, in step S204, the remote UE100A detects that it has moved from outside the coverage area to inside the coverage area. The remote UE100A may also detect that it has moved inside the coverage area in response to the received power (RSRP) of the reference signal received from the cellular communication network exceeding a threshold. The remote UE100A may also detect that it has moved inside the coverage area in response to receiving a synchronization signal from the cellular communication network. Alternatively, in step S204, the remote UE100A may detect that it has transitioned from the RRC idle state or RRC inactive state to the RRC connected state (step S205 described below).

[0109] Here, the thresholds to be compared with RSRP and the network communication status that the remote UE100A should detect may be set from the gNB200 using system information (SIB), or they may be predefined thresholds (e.g., S-criteria) and / or settings pre-written to the SIM (Subscriber Identity Module), etc. (Pre-configuration).

[0110] In step S205, the remote UE100A establishes a network connection with the gNB200 and transitions to the RRC connected state. Note that step S205 may be performed from step S208 onwards, for example, between step S208 and step S209.

[0111] When the remote UE100A detects a change in the network communication status, it performs a process to terminate the sidelink communication between the remote UE100A and the relay UE100B.

[0112] As part of this process, the remote UE100A may notify the relay UE100B of a change in the network communication state (for example, a transition to the RRC connected state) (step S206). Here, the remote UE100A may also notify the remote UE100A of the received power (RSRP) of the reference signal received from the cellular communication network. Such notification may be made by a PC5-RRC message or a PC5-S message.

[0113] The relay UE100B may, based on a notification from the remote UE100A, perform the process of releasing the sidelink connection with the remote UE100A. For example, the relay UE100B may discard the PC5-RRC entity and / or the PC5-S entity, or send a PC-RRC release instruction to the remote UE100A.

[0114] The remote UE100A may terminate sidelink communication with the relay UE100B in response to detecting a change in the network communication state (step S207). For example, the remote UE100A may cause a communication timeout by not responding to the relay UE100B, implicitly notifying the relay UE100B of the release of the sidelink connection. The remote UE100A may also discard its own PC5-RRC entity and / or PC5-S entity.

[0115] In step S208, the remote UE100A performs the process of releasing the sidelink connection with the relay UE100B. For example, the remote UE100A may explicitly notify the relay UE100B of the release of the sidelink connection using a PC5-RRC message indicating the release of the sidelink connection.

[0116] In step S209, the remote UE100A sends and receives data via network communication with the gNB200.

[0117] Although this operation pattern describes U2N relaying, it may also be applied to U2U relaying. In this case, gNB200 in this operation pattern should be read as another UE (another remote UE) 100C, and the network communication state should be read as the communication state between remote UE100A and the other remote UE100C. Remote UE100A may detect that the other remote UE100C is nearby (within direct communication range) by, for example, a discovery procedure (step S204). After that, remote UE100A performs the same operation as in this operation pattern to release the sidelink connection with relay UE100B.

[0118] (1.2) Operation Pattern 2 An operation pattern 2 of sidelink communication control by remote UE100A according to one embodiment will be described.

[0119] In operation pattern 2 of sidelink communication control by remote UE100A, relay UE100B, which performs U2N relay, forwards the first system information broadcast by the first cell of the cellular communication network to remote UE100A. Remote UE100A detects an improvement in the network communication state with the second cell of the cellular communication network. Then, in response to the detection of this improvement, remote UE100A acquires the second system information broadcast by the second cell, rather than the first system information forwarded from relay UE100B. As a result, if remote UE100A moves to the coverage of a second cell different from the first cell to which it is connected, remote UE100A can acquire the system information of the second cell.

[0120] Figure 14 shows an operation pattern 2 of sidelink communication control by a remote UE 100A according to one embodiment. In Figure 14, an example is shown in which cell #1 (first cell) is managed by gNB200#1 and cell #2 (second cell) is managed by gNB200#2, but cell #1 and cell #2 may be managed by a single gNB200.

[0121] As shown in Figure 14, in step S301, the relay UE100B located within the coverage of cell #1 receives (acquires) SIB#1 (first system information), which is the system information of cell #1, from cell #1.

[0122] In step S302, relay UE100B forwards SIB#1 to remote UE100A. Remote UE100A, located outside the coverage area, receives and applies SIB#1 from relay UE100B.

[0123] In step S303, the remote UE100A determines the network communication status between the remote UE100A and cell #2 and detects any changes in the network communication status.

[0124] For example, in step S303, the remote UE100A detects that it has moved from outside the coverage area into the coverage area of ​​cell #2. The remote UE100A also detects that it has moved into the coverage area of ​​cell #2 when the received power (RSRP) of the reference signal received from cell #2 exceeds a threshold. The remote UE100A may also detect that it has moved into the coverage area of ​​cell #2 when it receives a synchronization signal from cell #2. Here, the threshold for comparison with RSRP and the network communication state that the remote UE100A should detect may be set from the gNB200 using system information (SIB), etc., or they may be predefined thresholds (e.g., S-criteria) and / or settings pre-written to the SIM, etc. (Pre-configuration).

[0125] In step S304, the remote UE100A, having moved into the coverage of cell #2, receives (acquires) SIB#2 (second system information), which is the system information of cell #2, from cell #2. The remote UE100A may discard the settings provided by SIB#1, which was forwarded from relay UE100B.

[0126] Figure 15 shows an example of a modification to the operation pattern 2 of sidelink communication control by a remote UE 100A according to one embodiment. This modification example assumes that the remote UE 100A moves from inside the coverage area to outside the coverage area.

[0127] As shown in Figure 15, in step S351, the remote UE100A located within the coverage of cell #1 receives (acquires) the SIB from cell #1.

[0128] In step S352, the remote UE100A determines the network communication status between the remote UE100A and cell #1 and detects any changes in the network communication status.

[0129] For example, in step S352, the remote UE100A detects that it has moved from within the coverage of cell #1 to outside its coverage. The remote UE100A may also detect that it has moved outside the coverage when the received power (RSRP) of the reference signal received from cell #1 falls below a threshold. Here, the threshold for comparison with the RSRP may be set by system information (SIB) etc. from the gNB200, or it may be a predefined threshold (e.g., S-criteria) and / or a setting pre-written to the SIM etc. (Pre-configuration).

[0130] Here, the remote UE100A may perform the relay UE discovery procedure and the relay UE selection procedure described above to establish a sidelink connection with relay UE100B.

[0131] In step S353, relay UE100B, located within the coverage of cell #1, receives (acquires) the SIB from cell #1.

[0132] In step S354, relay UE100B forwards the SIB to remote UE100A. Remote UE100A, located outside the coverage area, receives and applies the SIB from relay UE100B.

[0133] Note that while Figure 15 illustrates an example where the relay UE100B is located within the coverage of cell #1, the relay UE100B may also be located in a different cell (cell #2). In this case, the relay UE100B forwards the SIB from cell #2 to the remote UE100A, which is outside the coverage area. The remote UE100A may discard the settings made by the SIB from cell #1.

[0134] (2) Communication control by relay UE100B Sidelink communication control using a relay UE100B according to one embodiment will be described.

[0135] A relay UE100B, which has a sidelink connection with a remote UE100A, detects a deterioration in the communication status between the relay UE100B and the cellular communication network (gNB200), or between the relay UE100B and other UE100Cs. In response to the detection of such deterioration, the relay UE100B performs a predetermined process to terminate the sidelink communication with the remote UE100A.

[0136] The remote UE100A cannot ascertain the communication status between the relay UE100B and the cellular communication network (gNB200), or the communication status between the relay UE100B and other UE100Cs, making it difficult to determine whether sidelink relaying can continue. Therefore, when the relay UE100B detects a deterioration in the communication status, it performs a predetermined process to terminate sidelink communication with the remote UE100A, thereby enabling the remote UE100A to perform processes such as relay UE reselection.

[0137] The relay UE100B may, in a predetermined process, send a reselection instruction to the remote UE100A to re-select a relay UE100B other than itself. If the relay UE100B detects a deterioration in the communication state between itself and another UE100C, it may notify the remote UE100A of that other UE.

[0138] Figure 16 shows a sidelink communication control by the relay UE100B according to one embodiment. In Figure 16, steps that are not essential are shown with dashed lines.

[0139] As shown in Figure 16, in step S401, the remote UE100A has established a sidelink connection with the relay UE100B. The relay mode of the relay UE100B may be either U2N relay or U2U relay.

[0140] In step S402, the remote UE100A transmits and receives data with the relay UE100B.

[0141] In step S403, the relay UE100B relays the data transmitted and received by the remote UE100A. Specifically, the relay UE100B transmits and receives the relay data with the gNB200 or another UE100C.

[0142] In step S404, the relay UE100B determines the communication status between the relay UE100B and the cellular communication network (gNB200), or between the relay UE100B and other UE100C devices, and detects any deterioration in the said communication status.

[0143] For example, in the case of U2N relay, the relay UE100B may detect at least one of the following: RLF (Radio Link Failure), RRC connection recovery failure, and RRC connection release in the network connection with the gNB200. The relay UE100B may also detect that the received power (RSRP) of the reference signal received from the gNB200 or the throughput of network communication with the gNB200 falls below a threshold, or that the resource utilization (occupancy rate) of network communication with the gNB200 exceeds a threshold.

[0144] On the other hand, in the case of U2U relay, the relay UE100B may detect at least one of the following in the sidelink connection with the other UE100C: RLF, PC5-RRC connection release, PC5-S connection release, failure to establish PC5-RRC connection, and failure to establish PC5-S connection. The relay UE100B may also detect that the received power (RSRP) of the reference signal received from the other UE100C or the throughput of the sidelink communication with the other UE100C has fallen below a threshold, or that the resource utilization (occupancy rate) of the sidelink communication with the other UE100C has exceeded a threshold.

[0145] The threshold may be set from the gNB200 using system information (SIB), a predefined threshold (e.g., S-criteria), or a setting pre-written to the SIM (Pre-configuration).

[0146] In step S405, the relay UE100B determines the deterioration of the communication state between the relay UE100B and the cellular communication network (gNB200), or the communication state between the relay UE100B and other UE100C, and sends a message indicating the deterioration of the communication state to the remote UE100A. The message may be a PC5-RRC message sent by unicast, or a message sent by broadcast.

[0147] For example, the message in step S405 may be a reselection instruction that instructs the remote UE100A to perform a relay UE reselection process. In the case of U2U relay, the message may include a destination ID indicating the other UE100C whose sidelink communication state has deteriorated. The message may also include information indicating whether the deterioration in communication state is due to a deterioration in the network communication state or a deterioration in the sidelink communication state.

[0148] The message in step S405 may be a suspend instruction indicating a temporary interruption of sidelink communication with the remote UE100A. In this case, the relay UE100B may send a resume instruction to the remote UE100A indicating the resumption of sidelink communication with the remote UE100A when the communication status between the relay UE100B and the cellular communication network (gNB200) or between the relay UE100B and other UE100Cs improves. These instructions may include information indicating the cause (based on the above detection results).

[0149] The message in step S405 may be a discovery message. The discovery message includes a list of identifiers of other UE100Cs with which the relay UE100B has a sidelink connection. If the relay UE100B detects a deterioration in the communication status with any of the UE100Cs in the list, it updates the list to remove the identifier of that UE100C and notifies the remote UE100A of the discovery message containing the updated list. This allows the remote UE100A to correctly identify other UE100Cs with which it can communicate via sidelink relay. If the list includes the identifier of a gNB200 (i.e., in the case of U2N relay), that identifier (such as a cell ID or an identifier indicating network connection) may be removed from the list.

[0150] The message in step S405 may be the relay UE message described above. In other words, relay UE200B triggers the transmission of the relay UE message described above in response to a change (determination) in the communication status with gNB200 or other UE100C.

[0151] In step S406, the relay UE100B may perform processing to terminate sidelink communication with the remote UE100A. For example, the relay UE100B may generate a communication timeout by not responding to the remote UE100A, implicitly notifying the remote UE100A of the release of the sidelink connection. Alternatively, the relay UE100B may explicitly notify the remote UE100A of the release of the connection using a PC5-RRC message indicating the release of the sidelink connection.

[0152] In step S407, the remote UE 100A may trigger a relay UE reselection process based on a message received from the relay UE 100B in step S405, for example. Here, the remote UE 100A may perform the relay UE reselection process after excluding the relay UE 100B that sent the message from the reselection candidates. Within the remote UE 100A, the AS layer may notify the upper layer (PC5-S, etc.) that it has received a message (and the content of the message). In this case, the upper layer may exclude the relay UE 100B that sent the message from the discovery targets in the relay UE discovery procedure.

[0153] (Other embodiments) Each of the sequences described above can be performed not only separately and independently, but also by combining two or more steps from different sequences.

[0154] A program may be provided that causes a computer to perform each of the processes that UE100 or gNB200 performs. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM.

[0155] Alternatively, the circuits that perform each process carried out by the UE100 or gNB200 may be integrated, and at least a portion of the UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC).

[0156] Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the invention.

[0157] This application claims priority to U.S. Provisional Application No. 63 / 086146 (filed October 1, 2020), the entirety of which is incorporated into the specification of this application.

Claims

1. A communication control method used in a cellular communication system, The lower layer of the remote user device receives a PC5-RRC message from the first relay user device that includes information indicating a radio link failure (RLF) between the first relay user device that relays data from the remote user device and the network, The lower layer of the remote user device further provides notification to the upper layer of the remote user device based on information indicating the RLF, The upper layer of the remote user device is a layer that configures the discovery of relay user devices, which have the capability to relay data from the remote user device. Communication control method.

2. A remote user device used in a cellular communication system, Upper layer and A lower layer receives a PC5-RRC message from a first relay user device that relays data from the remote user device, which includes information indicating a radio link failure (RLF) between the first relay user device and the network, and notifies the upper layer based on the information indicating the RLF. The aforementioned upper layer is a layer that configures settings related to the discovery of relay user devices that have the capability to relay data from the remote user devices. Remote user device.

3. A processor for controlling remote user devices used in cellular communication systems, The lower layer of the remote user device processes receiving a PC5-RRC message from the first relay user device that includes information indicating a radio link failure (RLF) between the first relay user device that relays data from the remote user device and the network, The lower layer of the remote user device performs a process of notifying the upper layer of the remote user device based on information indicating the RLF, The upper layer of the remote user device is a layer that configures the discovery of relay user devices, which have the capability to relay data from the remote user device. Processor.

Images