Wireless communication device and wireless communication system

Abstract

A wireless communication device (200) comprises: a wireless communication unit (210) for transmitting and receiving signals; and a processor (220) for controlling power supply to the wireless communication unit (210), wherein the processor (220) performs the following processing: determining an activity interval indicating a time for power supply to the wireless communication unit (210) based on information related to a setting of a multicast signal, supplying power to the wireless communication unit (210) during the determined activity interval, and performing listening to determine whether wireless resources are used by other devices during the determined activity interval.

Description

Technical Field

[0001] The present invention relates to a wireless communication device, a wireless communication system and a power control method. Background Art

[0002] In current networks, services for mobile terminals (smartphones, feature phones) occupy a large portion of network resources. Furthermore, the number of services used by mobile terminals is expected to expand in the future.

[0003] On the other hand, the development of IoT (Internet of Things) services (e.g., transportation systems, smart meters, and monitoring systems for devices) is being driven by the need to support services with diverse requirements. Therefore, in addition to the standard technologies of 4G (fourth-generation mobile communications) (e.g., Non-Patent Documents 2 to 12), the fifth-generation mobile communications (5G or NR (New Radio)) standards are being required to achieve higher data rates, larger capacity, and lower latency.

[0004] In addition, regarding the fifth-generation communication standard, technical research was conducted in the working groups of the 3GPP (Third Generation Partnership Project) (for example, TSG-RAN WG1, TSG-RAN WG2, etc.), and the first version of the standard specification was released in December 2017 (non-patent documents 13 to 39).

[0005] As mentioned above, in order to cope with a variety of services, 5G envisions services classified as eMBB (Enhanced Mobile Broadband), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communication).

[0006] 3GPP working groups also discussed NR-V2X (New Radio Vehicle to Everything) communications. NR-V2X is a general term for V2V (Vehicle to Vehicle) communications between vehicles using sidelink channels, V2P (Vehicle to Pedestrian) communications between vehicles, V2I (Vehicle to Infrastructure) communications between vehicles and road infrastructure such as road signs, and V2N (Vehicle to Network) communications between vehicles and networks. V2X regulations are described in, for example, Non-Patent Document 1.

[0007] Regarding resource configuration in NR-V2X, there is a configuration method that performs TDM (Time Division Multiplexing) or FDM (Frequency Division Multiplexing) on ​​the control channel (PSCCH: Physical Sidelink Control Channel) and the data channel (PSSCH: Physical Sidelink Shared CHannle). In addition, the resource mapping of PSCCH includes SCI (Sidelink Control Information), which contains information such as the modulation method and coding rate of the corresponding PSSCH data. In addition, in order to improve the channel quality of the side link, a feedback channel (PSFCH: Physical Sidelink Feedback Channel) is introduced.

[0008] Prior art literature

[0009] Non-patent literature

[0010] Non-Patent Document 1: 3GPP TS 22.186 V 16.2.0 (2019-06)

[0011] Non-Patent Document 2: 3GPP TS 36.211 V16.0.0 (December 2019)

[0012] Non-Patent Document 3: 3GPP TS 36.212 V16.0.0 (December 2019)

[0013] Non-Patent Document 4: 3GPP TS 36.213 V16.0.0 (December 2019)

[0014] Non-Patent Document 5: 3GPP TS 36.300 V16.0.0 (December 2019)

[0015] Non-Patent Document 6: 3GPP TS36.321 V15.8.0 (December 2019)

[0016] Non-Patent Document 7: 3GPP TS 36.322 V 15.3.0 (2019-09)

[0017] Non-Patent Document 8: 3GPP TS 36.323V 15.5.0 (2019-12)

[0018] Non-Patent Document 9: 3GPP TS 36.331 V15.8.0 (December 2019)

[0019] Non-Patent Document 10: 3GPP TS 36.413 V16.0.0 (December 2019)

[0020] Non-Patent Document 11: 3GPP TS 36.423 V16.0.0 (2019-12)

[0021] Non-Patent Document 12: 3GPP TS 36.425 V15.0.0 (June 2018)

[0022] Non-Patent Document 13: 3GPP TS 37.340 V16.0.0 (December 2019)

[0023] Non-Patent Document 14: 3GPP TS 38.201 V16.0.0 (December 2019)

[0024] Non-Patent Document 15: 3GPP TS 38.202 V16.0.0 (December 2019)

[0025] Non-Patent Document 16: 3GPP TS 38.211 V16.0.0 (December 2019)

[0026] Non-Patent Document 17: 3GPP TS 38.212 V16.0.0 (December 2019)

[0027] Non-Patent Document 18: 3GPP TS 38.213 V16.0.0 (December 2019)

[0028] Non-Patent Document 19: 3GPP TS 38.214 V16.0.0 (December 2019)

[0029] Non-Patent Document 20: 3GPP TS 38.215 V16.0.1 (2020-01)

[0030] Non-Patent Document 21: 3GPP TS 38.300 V16.0.0 (December 2019)

[0031] Non-Patent Document 22: 3GPP TS 38.321 V15.8.0 (December 2019)

[0032] Non-Patent Document 23: 3GPP TS 38.322 V15.5.0 (March 2019)

[0033] Non-Patent Document 24: 3GPP TS 38.323 V15.6.0 (June 2019)

[0034] Non-Patent Document 25: 3GPP TS 38.331 V15.8.0 (December 2019)

[0035] Non-Patent Document 26: 3GPP TS 38.401 V16.0.0 (December 2019)

[0036] Non-Patent Document 27: 3GPP TS 38.410 V16.0.0 (December 2019)

[0037] Non-Patent Document 28: 3GPP TS 38.413 V16.0.0 (December 2019)

[0038] Non-Patent Document 29: 3GPP TS 38.420 V15.2.0 (December 2018)

[0039] Non-Patent Document 30: 3GPP TS 38.423 V16.0.0 (December 2019)

[0040] Non-Patent Document 31: 3GPP TS 38.470 V16.0.0 (December 2019)

[0041] Non-Patent Document 32: 3GPP TS 38.473 V16.0.0 (December 2019)

[0042] Non-Patent Document 33: 3GPP TR38.801 V14.0.0 (March 2017)

[0043] Non-Patent Document 34: 3GPP TR38.802 V14.2.0 (September 2017)

[0044] Non-Patent Document 35: 3GPP TR38.803 V14.2.0 (September 2017)

[0045] Non-Patent Document 36: 3GPP TR38.804 V14.0.0 (March 2017)

[0046] Non-Patent Document 37: 3GPP TR 38.900 V15.0.0 (June 2018)

[0047] Non-Patent Document 38: 3GPP TR38.912 V15.0.0 (June 2018)

[0048] Non-Patent Document 39: 3GPP TR38.913 V15.0.0 (June 2018) Summary of the Invention

[0049] Problems to be solved by the invention

[0050] However, to reduce power consumption in wireless communication devices, wireless communication devices sometimes perform discontinuous reception (DRX), which intermittently performs reception processing. When performing DRX, the wireless communication device operates the wireless communication unit and performs reception processing only during the active interval within a specified DRX cycle. Similarly, in NR-V2X, each terminal device can reduce power consumption by performing DRX.

[0051] However, in NR-V2X, a large amount of services are multicast services, and when terminal devices belonging to the same group perform DRX respectively, there is a problem of reduced communication performance.

[0052] Specifically, NR-V2X assumes that multicasting, in which a terminal device sends signals to other terminal devices in the same group, will be frequently performed. In this scenario, each terminal device in the group independently sets an active interval and performs reception processing only during that interval. This reduces the number of terminal devices that can receive the signal, depending on the timing of the multicasting.

[0053] Alternatively, it is possible to synchronize the active intervals of terminal devices belonging to the same group, allowing each terminal device to perform reception processing simultaneously. However, in this case, each terminal device would also perform sensing to check for availability of wireless resources at the same timing. Therefore, when selecting wireless resources for transmission based on the sensing results, the likelihood of conflict between the wireless resources selected by each terminal device increases.

[0054] As described above, when performing multicast, it is not easy to reduce the power consumption of a wireless communication device by intermittent reception without degrading communication performance.

[0055] The disclosed technology has been developed in view of this point, and an object of the technology is to provide a wireless communication device and a wireless communication system capable of reducing power consumption while suppressing degradation in communication performance.

[0056] Means for solving problems

[0057] The wireless communication device disclosed in the present application, in one embodiment, comprises: a wireless communication unit that transmits and receives signals; and a processor that controls power supply to the wireless communication unit, wherein the processor performs the following processing: determining an activity interval indicating a time for power supply to the wireless communication unit based on information related to a setting for multicasting of signals; supplying power to the wireless communication unit during the determined activity interval; and performing listening to determine whether wireless resources are used by other devices during the determined activity interval.

[0058] Effects of the Invention

[0059] According to one aspect of the wireless communication device and the wireless communication system disclosed in the present application, it is possible to reduce power consumption and suppress degradation of communication performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a diagram showing an example of multicast types.

[0061] Figure 2 This is a diagram showing another example of the multicast type.

[0062] Figure 3 This is a block diagram showing the structure of a transmitting device according to one embodiment.

[0063] Figure 4 This is a diagram explaining the selection of a transmission time slot.

[0064] Figure 5 This is a block diagram showing the structure of a receiving device according to one embodiment.

[0065] Figure 6 is a flowchart illustrating a power control method.

[0066] Figure 7 This is a diagram showing a specific example of the relationship between regions and activity intervals.

[0067] Figure 8 It is a diagram showing a specific example of an active section corresponding to a communication range.

[0068] Figure 9 It is a diagram showing a specific example of the active section corresponding to the group ID.

[0069] Figure 10 It is a diagram showing a specific example of an active section according to another embodiment.

[0070] Figure 11 It is a diagram showing a specific example of an active section according to still another embodiment. DETAILED DESCRIPTION

[0071] Hereinafter, an embodiment of the wireless communication device, wireless communication system, and power control method disclosed in the present application will be described in detail with reference to the accompanying drawings.

[0072] Figure 1 FIG. 1 is a diagram showing an example of multicast according to an embodiment of the present invention. Figure 1 As shown, a wireless communication system according to one embodiment includes a plurality of terminal devices, each of which is mounted on a vehicle. Each terminal device can communicate wirelessly with each other and may perform multicast to transmit signals to other terminal devices belonging to the same group.

[0073] exist Figure 1 In the example shown, terminal devices within a predetermined communication range centered around the transmitting terminal device form a group. For example, terminal devices within a predetermined communication range centered around transmitting terminal device TX#1 belong to group #1, terminal devices within a predetermined communication range centered around transmitting terminal device TX#2 belong to group #2, and terminal devices within a predetermined communication range centered around transmitting terminal device TX#3 belong to group #3. The size of the communication range of each group #1 through #3 is predetermined, for example, based on the type of communication service.

[0074] Each terminal device determines the location of the terminal device itself and the terminal device that sends the signal through an area set according to geographic coordinates. That is, in an area where a wireless communication system is carried out, for example, a grid-shaped area is set, and each terminal device can determine whether the terminal device belongs to a group based on the distance between the area where the terminal device that sends the signal is located and the coordinates of the terminal device where the terminal device is located. Specifically, for example, when a signal containing identification information of the area where the terminal device TX#1 is located (hereinafter referred to as "area ID") is sent from the terminal device TX#1, each terminal device calculates the distance between the terminal device TX#1 based on the coordinates of the terminal device and the area ID contained in the signal sent from the terminal device TX#1. Furthermore, each terminal device can determine whether the terminal device belongs to group #1 by determining whether the calculated distance is included in the communication range.

[0075] As described above, in wireless communication systems, multicast is sometimes performed in which signals are transmitted and received within a group set according to a communication range.

[0076] Figure 2 FIG. 1 is a diagram showing another example of multicast according to an embodiment of the present invention. Figure 1 Likewise, in Figure 2In one embodiment, the wireless communication system also includes a plurality of terminal devices, each of which is mounted on a vehicle. Each terminal device can communicate wirelessly with each other and may perform multicast to send signals to other terminal devices belonging to the same group.

[0077] exist Figure 2 In the example shown, the terminal devices that are pre-registered as members constitute a group. That is, for example, the multiple terminal devices surrounded by the solid line in the figure belong to group #1, and the multiple terminal devices surrounded by the dotted line in the figure belong to group #2. These groups do not depend on the location of the terminal devices. For example, even if the terminal devices are far away from each other, they belong to the same group as long as they are pre-registered. In addition, each terminal device can also belong to multiple groups at the same time, and each saves the identification information of the group to which the device belongs (hereinafter referred to as "group ID"). In addition, the group ID is the identification information that represents the destination group of the multicast, and is therefore sometimes also called the destination ID.

[0078] As described above, in wireless communication systems, multicast of a type in which signals are transmitted and received within a group set according to a group ID is sometimes performed.

[0079] Terminal devices performing multicasting implement discontinuous reception (DRX) based on the multicast type. Specifically, the terminal device determines an active interval ("Active Interval") indicating when power is supplied to the wireless communication unit based on information related to the multicast configuration, and transmits and receives signals only during the active interval. Furthermore, the terminal device stops supplying power to the wireless communication unit outside of the active interval within the specified DRX cycle to conserve power.

[0080] Figure 3 This is a block diagram showing the structure of the transmission device 100 according to one embodiment. Figure 3 The transmitter 100 shown is one of the terminal devices that multicasts the signal. Figure 3 Only the processing units related to signal transmission are shown in the figure. In addition, the following mainly describes the functions of each processing unit when performing multicast corresponding to the communication range.

[0081] Figure 3 The illustrated transmitting device 100 includes a processor 110 , a memory 120 , and a wireless communication unit 130 .

[0082] Processor 110 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and comprehensively controls the entire transmission device 100. Specifically, processor 110 includes an application processing unit 111, a control information generation unit 112, a transmission data generation unit 113, a group management unit 114, a time slot selection unit 115, and a transmission control unit 116.

[0083] The application processing unit 111 executes processing of applications corresponding to various communication services.

[0084] The control information generation unit 112 generates control information such as SCI (Sidelink Control Information). The control information generated by the control information generation unit 112 includes the area ID of the area where the transmitting device 100 is located. The control information may also include information on the data coding rate and modulation scheme, information specifying the radio resources of the data channel used for data transmission, and information specifying the radio resources used for data retransmission.

[0085] The transmission data generating unit 113 generates transmission data to be multicast to terminal devices in the group based on the processing of the application processing unit 111. The transmission data generated by the transmission data generating unit 113 is multicast to terminal devices in the group set according to the communication range, for example.

[0086] The group management unit 114 manages the groups to which the transmitting device 100 belongs. Specifically, the group management unit 114 obtains the location information of the transmitting device 100 using, for example, a GPS (Global Positioning System) and determines the area ID of the area where the transmitting device 100 is located. Furthermore, the group management unit 114 determines the areas within the communication range, centered on the area where the transmitting device 100 is located. The group management unit 114 determines that the areas within the communication range are areas corresponding to the group and stores the area IDs of these areas.

[0087] Furthermore, when executing multicast corresponding to the group ID, the group management unit 114 stores the group ID of the group to which the transmission device 100 belongs, and also stores identification information of other terminal devices belonging to the group.

[0088] The time slot selection unit 115 selects a time slot for transmitting data based on the information about the groups managed by the group management unit 114. Specifically, the time slot selection unit 115 selects a time slot that is included in the active interval of the terminal devices belonging to the group to which the data is to be transmitted. In other words, the active interval of each terminal device consists of time slots corresponding to the region in which the terminal device is located, and the active interval varies depending on the region in which the terminal device is located. Therefore, the time slot selection unit 115 selects a time slot that is a common active interval for all terminal devices belonging to the group to which the data is to be transmitted.

[0089] For example, Figure 4 As shown, when the group for which transmitter 100 performs multicast includes areas #1 through #5, the active intervals for each area #1 through #5 differ, as indicated by the diagonal lines in the figure. Specifically, the active interval for a terminal device in area #1 is time slots #2 through #6, the active interval for a terminal device in area #2 is time slots #3 through #7, the active interval for a terminal device in area #3 is time slots #4 through #8, the active interval for a terminal device in area #4 is time slots #5 through #9, and the active interval for a terminal device in area #5 is time slots #6 through #10. The lengths of these active intervals are determined by calculating the number of time slots that constitute the active interval based on the relationship between the communication range and the area size.

[0090] exist Figure 4 In the example shown, the time slot selection unit 115 selects the time slot #6 that is the common active period for all terminal devices located in areas #1 to #5, and notifies the transmission control unit 116 of this selection.

[0091] Furthermore, when executing multicast corresponding to the group ID, the time slot selection unit 115 selects a time slot that serves as an active interval for terminal devices belonging to the destination group. Specifically, when executing multicast corresponding to the group ID, an active interval is set for each group. Therefore, the time slot selection unit 115 selects a time slot that serves as an active interval for the destination group and notifies the transmission control unit 116 of this fact.

[0092] Transmission control unit 116 encodes and modulates the control information and transmit data, maps them to radio resources, and generates a transmit signal. Specifically, transmission control unit 116 maps the control information to a control channel and the transmit data to a data channel to generate a transmit signal. At this time, transmission control unit 116 maps the transmit data and control information to the time slots notified by time slot selector 115.

[0093] The memory 120 includes, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores information used for processing by the processor 110 .

[0094] The wireless communication unit 130 transmits a signal to other terminal devices. Specifically, the wireless communication unit 130 performs a predetermined wireless transmission process on the transmission signal and wirelessly transmits it via an antenna. This transmission signal is a multicast signal to terminal devices belonging to the destination group.

[0095] Figure 5 This is a block diagram showing the structure of a receiving device 200 according to one embodiment. Figure 5 The receiving device 200 shown is one of the terminal devices that receives the multicast signal. However, the terminal device included in the wireless communication system may also include Figure 3 The transmitting device 100 and Figure 5 The functions of both the receiving device 200 shown in FIG. Hereinafter, the functions of each processing unit when executing multicast corresponding to the communication range will be mainly described.

[0096] Figure 5 The receiving device 200 shown includes a wireless communication unit 210 , a processor 220 , and a memory 230 .

[0097] Wireless communication unit 210 transmits and receives signals with other terminal devices. Specifically, wireless communication unit 210 wirelessly receives signals via an antenna and performs predetermined wireless reception processing on the received signals. Furthermore, wireless communication unit 210 performs predetermined wireless transmission processing on transmit signals and wirelessly transmits them to other terminal devices via the antenna. As described later, wireless communication unit 210 operates only during the active period of receiving device 200. Outside of this period, it conserves power and does not consume electricity.

[0098] The processor 220 includes, for example, a CPU, an FPGA, or a DSP, and centrally controls the entire receiving device 200. Specifically, the processor 220 includes a group management unit 221, a time slot determination unit 222, a power management unit 223, a reception control unit 224, a listening unit 225, an application processing unit 226, a control information generation unit 227, a transmission data generation unit 228, and a transmission control unit 229.

[0099] The group management unit 221 manages the groups to which the receiving device 200 belongs. Specifically, the group management unit 221 obtains the location information of the receiving device 200 using, for example, GPS, and determines the coordinates of the receiving device 200. Furthermore, the group management unit 221 obtains the area ID of the area where the signal's source is located from the received signal to determine whether the receiving device 200 belongs to the group. Specifically, the group management unit 221 calculates the distance between the area where the signal's source is located and the coordinates of the receiving device 200. If the calculated distance is less than the communication range, the receiving device 200 is determined to belong to the group. Furthermore, the group management unit 221 determines the area ID of the area where the receiving device 200 is located based on the coordinates of the receiving device 200.

[0100] Furthermore, when executing multicast corresponding to the group ID, the group management unit 221 stores the group ID of the group to which the reception device 200 belongs, and also stores identification information of other terminal devices belonging to the group.

[0101] The time slot determination unit 222 obtains the area ID of the area where the receiving device 200 is located from the group management unit 221 and determines the time slots that constitute the active interval of the receiving device 200. Specifically, the time slot determination unit 222 determines the time slots corresponding to each area and determines the active interval of the receiving device 200, which consists of a plurality of consecutive time slots. Specifically, the time slot determination unit 222 determines the time slots that are included in the active interval using the determination function S(n) of the following equation (1) indicating whether time slot #n is included in the active interval.

[0102] [Formula 1]

[0103]

[0104] Time slot #n where the decision function S(n) in equation (1) is 1 is included in the active interval, and time slot #n where the decision function S(n) is 0 is not included in the active interval. In equation (1), Δt is a predetermined integer offset, and N is the number of time slots in the predetermined DRX cycle. Furthermore, amodA represents the remainder when a is divided by A. Furthermore, Z(m) is a function represented by equation (2).

[0105] [Formula 2]

[0106]

[0107] In the above equation (2), i is the area ID of area #i where the receiving device 200 is located, and Y is a constant determined by the communication range and the size of the area. Specifically, Y is an integer that satisfies the conditions of the following equation (3).

[0108] [Formula 3]

[0109]

[0110] In the above formula (3), d cr represents the size of the communication range, and L represents the size of the area. Here, the area is a square with a side of L.

[0111] As can be seen from equations (2) and (3), for example, when constant Y is the smallest integer that satisfies equation (3), function Z(m) outputs 1 when area #m is within the communication range with receiving device 200, and outputs 0 when area #m is outside the communication range with receiving device 200. In other words, function Z(m) is a function that indicates the relevance of areas, and is a function that outputs 1, indicating relevance, for at least areas within the communication range from the area where receiving device 200 is located.

[0112] In addition, according to the above formula (1), the time slot corresponding to the area with correlation is determined to be included in the active section. Therefore, the time slot determination unit 222 determines the time slot corresponding to the area where the receiving device 200 is located and the area with correlation with the area as the active section of the receiving device 200. The length (number of time slots) of the active section determined by this determination is l act It is represented by the following formula (4).

[0113] l act =2Y+1...(4)

[0114] With such an active interval length, there are time slots that are simultaneously active intervals for at least the area within the communication range of the area where receiving device 200 is located. Therefore, by having each terminal device, including receiving device 200, determine the active interval in a similar manner, there are time slots that are simultaneously active intervals for all terminal devices within the communication range of the signal transmission source, allowing signals to be transmitted at a timing that can be received by each terminal device within the communication range. Furthermore, all parameters in equations (1) to (4) above can be pre-set in the wireless communication system or semi-statically re-set.

[0115] The power management unit 223 controls the power supply to the wireless communication unit 210 to operate or conserve energy. Specifically, the power management unit 223 operates the wireless communication unit 210 by supplying power during the active interval determined by the time slot determination unit 222. On the other hand, the power management unit 223 stops supplying power outside the active interval to conserve energy.

[0116] The reception control unit 224 receives the received signal from the wireless communication unit 210 and performs reception processing on the received signal. Specifically, the reception control unit 224 demodulates and decodes the control channel to obtain control information and notifies the group management unit 221 of the area ID of the area where the signal is transmitted. In addition, the reception control unit 224 demodulates and decodes the data channel according to the control information.

[0117] The listening unit 225 listens to determine whether other terminal devices are using wireless resources. Specifically, when the active interval determined by the time slot determination unit 222 arrives within a predetermined listening window, the listening unit 225 determines whether other terminal devices are transmitting signals in each time slot within the active interval.

[0118] The application processing unit 226 executes processing of applications corresponding to various communication services.

[0119] The control information generation unit 227 generates control information such as the SCI. The control information generated by the control information generation unit 227 includes the area ID of the area where the receiving device 200 is located. The control information may also include information on the data coding rate and modulation method, information for determining the wireless resources of the data channel used for data transmission, and information for determining the wireless resources used for data retransmission.

[0120] The transmission data generating unit 228 generates transmission data to be multicast to the terminal devices in the group according to the processing of the application processing unit 226. The transmission data generated by the transmission data generating unit 228 is multicast to the terminal devices in the group set according to the communication range, for example.

[0121] The transmission control unit 229 encodes and modulates the control information and transmission data, maps them to wireless resources, and generates a transmission signal. Specifically, the transmission control unit 229 maps the control information to the control channel and the transmission data to the data channel to generate a transmission signal. At this time, the transmission control unit 229 selects the wireless resources to be used for signal transmission based on the results of the listening unit 225's listening. Specifically, the transmission control unit 229 selects a wireless resource from the selection window that, as a result of the listening, is estimated to be unused by other terminal devices and is included in the active interval of the terminal device that is the data transmission destination. The selection window is a resource pool with a specified time width that is set at a fixed time after the listening window.

[0122] The memory 230 includes, for example, a RAM or a ROM, and stores information used for processing by the processor 220 .

[0123] Next, refer to Figure 6 The flowchart shown explains the power control method of the receiving device 200 configured as described above.

[0124] First, the location information of the receiving device 200 is obtained by using GPS, etc., and the group management unit 221 obtains the coordinates of the receiving device 200, and determines the area ID based on the coordinates (step S101). Then, the time slot determination unit 222 uses the above formulas (1) to (3) to determine the active interval of the receiving device 200 (step S102). That is, the time slot corresponding to the area where the receiving device 200 is located and the area associated with the area is determined as the active interval of the receiving device 200. Specifically, for example, Figure 7 As shown, when receiving device 200 is located in area #4, areas #2 to #6 centered on area #4 are determined to be related areas. Then, time slots #2 to #6 corresponding to areas #2 to #6 are determined to be active periods of receiving device 200.

[0125] Then, the power management unit 223 determines whether the current time slot is included in the active period (step S103 ). If not included in the active period (step S103 : No), power supply to the wireless communication unit 210 is stopped to save energy (step S104 ).

[0126] On the other hand, if the current time slot is included in the active section (step S103: Yes), power is supplied to wireless communication unit 210 to activate wireless communication unit 210. Reception control unit 224 then performs reception processing on the received signal received by wireless communication unit 210 (step S105). Furthermore, within a predetermined listening window, listening unit 225 performs listening to determine whether another terminal device is transmitting a signal in the current time slot.

[0127] By setting an active interval corresponding to the area where the receiving device 200 is located, the wireless communication unit 210 can save energy outside the active interval, thereby reducing power consumption. In addition, within the active interval, signals can be transmitted and received, and listening to check the availability of wireless resources can be performed.

[0128] Next, an example will be given of specific examples of active periods of a plurality of terminal devices belonging to the same group. Figure 8 This figure shows a specific example of the activity range of a plurality of terminal devices UE#1 to #5. The terminal devices UE#1 to #5 belong to the same group corresponding to the communication range. In addition, the terminal devices UE#1 to #5 are located in different areas.

[0129] like Figure 8As shown, the window width of the listening window is the width that includes multiple DRX cycles. In each DRX cycle, there is one active interval corresponding to each area in the group. Terminal devices UE#1 to #5 respectively determine the time slots corresponding to the area where the device is located and the area associated with the area, and set the active interval. As a result, terminal devices UE#1 to #5 located in different areas set the active intervals with different timings and the active intervals that commonly include the time slots in which the wireless communication unit works as their respective DRX cycles. Then, terminal devices UE#1 to #5 perform listening in each active interval. Therefore, terminal devices UE#1 to #5 can respectively investigate the idle status of wireless resources at different timings.

[0130] When the timing selection window following the listening window arrives, terminal devices UE#1-#5 select radio resources for signal transmission based on the listening results. Specifically, terminal devices UE#1-#5 select radio resources from the radio resources corresponding to their respective active intervals that are estimated to be unused by other terminal devices based on the listening results. Because the active intervals of terminal devices UE#1-#5 are at different timings, the candidate radio resources for selection are also different, reducing the possibility of conflicts in the selected radio resources.

[0131] on the other hand, Figure 9 This is a diagram showing a specific example of an active section when multicast is performed based on a group ID.

[0132] like Figure 9 As shown, the listening window width is a width that includes multiple DRX cycles. Each DRX cycle includes one active interval for each group. That is, the active intervals of groups #1 and #2 are included in each DRX cycle.

[0133] exist Figure 9 In the example shown, the active intervals for each group are timed identically. Therefore, when performing multicast, the signal can be transmitted only during the active interval of the destination group. For example, when performing multicast to the terminal devices in group #1, the signal can be transmitted only during the active interval of group #1.

[0134] In each DRX cycle, the active interval of each group is the same timing. In contrast, in different DRX cycles, the active interval of each group is different timing. That is, for example, the active interval of group #1 is Figure 9 The three DRX cycles shown have different timings. This is achieved, for example, by setting the time slot corresponding to the value obtained by assigning an offset to the group ID of each group as the active interval in each DRX cycle, where the offset is determined in advance for each DRX cycle.

[0135] By setting the active intervals for each group at various timings within the DRX cycle, the number of radio resources corresponding to the active intervals for each group increases within the selection window. Consequently, the number of radio resources available for selection increases, reducing the likelihood of conflicts among the radio resources selected for each group.

[0136] As described above, according to this embodiment, the receiving device sets an active interval corresponding to the area and communication range, or sets an active interval corresponding to the group ID, performs reception processing including listening during the active interval, and saves energy during intervals outside the active interval. Furthermore, the transmitting device multicasts signals during the timing of the active interval shared by the destination terminal devices. Therefore, the signals multicast by the transmitting device can be received by the destination terminal devices, and the possibility of conflicts when the receiving device selects wireless resources based on the listening results can be reduced. In other words, it is possible to reduce power consumption while suppressing degradation in communication performance.

[0137] (Other embodiments)

[0138] In the above embodiment, when performing multicast corresponding to the communication range, for example, Figure 8 The active interval shown in FIG. 1 may be an active interval with an offset for each DRX cycle. Figure 10 As shown, different offsets Δt1 to Δt3 may be given to the active periods of the terminal apparatuses UE# 1 to UE# 5 in three DRX cycles.

[0139] By assigning an offset to the active interval for each DRX cycle, the active interval is set at various timings within the DRX cycle. This increases the number of radio resources corresponding to the active intervals of each terminal device within the selection window. As a result, the number of radio resources available for selection increases, reducing the likelihood of conflicts in the radio resources selected by each terminal device within the selection window.

[0140] In the above embodiment, multicast corresponding to the communication range and multicast corresponding to the group ID are described, but a single terminal device may belong to both multicast groups. In this case, an active interval corresponding to each multicast type is set.

[0141] Specifically, for example Figure 11As shown, when terminal devices UE#1-#5 belong to both a multicast group corresponding to the communication range and a multicast group corresponding to the group ID, different types of active intervals are set. Specifically, an active interval corresponding to the group ID of the group to which terminal devices UE#1-#5 belong is set, and an active interval corresponding to the area and communication range in which terminal devices UE#1-#5 are located is set. During each active interval, each terminal device UE#1-#5 activates its wireless communication unit and performs reception processing, including listening.

[0142] Description of labels

[0143] 110, 220 processors

[0144] 111, 226 Application Processing Department

[0145] 112, 227 Control Information Generation Unit

[0146] 113, 228 Sending data generation unit

[0147] 114, 221 Group Management Department

[0148] 115 Time Slot Selection Unit

[0149] 116, 229 Sending Control Unit

[0150] 120, 230 memory

[0151] 130, 210 Wireless Communications Department

[0152] 222 Time slot determination unit

[0153] 223 Electric Power Management Department

[0154] 224 Receiving Control Unit

[0155] 225 Interception Department

Claims

1. A wireless communication device, characterized in that: The wireless communication device comprises: a control unit that determines a parameter related to an offset of an active interval capable of receiving a signal based on destination information of a signal multicasted by another terminal device to a plurality of terminal devices including the terminal device; as well as a wireless communication unit configured to receive the signal in the active interval set using the parameter, The control unit determines whether wireless resources are being used by another device during the active period corresponding to the parameter, and selects wireless resources for multicast signals from among the wireless resources corresponding to the active period corresponding to the parameter.

2. The wireless communication device according to claim 1, wherein The control unit supplies power to the wireless communication unit in the active section corresponding to the offset, and determines whether wireless resources are being used by another device in the active section corresponding to the offset.

3. The wireless communication device according to claim 1 or 2, wherein: When multicast is performed within a group set according to a communication range corresponding to a communication service, the control unit determines an active period corresponding to an area where the own device is located and the communication range.

4. The wireless communication device according to claim 3, wherein The control unit determines an active section consisting of a plurality of consecutive time slots corresponding to respective areas.

5. The wireless communication device according to claim 4, wherein: The control unit determines an active section including time slots corresponding to an area where the own device is located and an area included in the communication range from the own device. The wireless communication device according to claim 1 , wherein: The control unit determines a parameter related to the shift of the active section based on identification information of the group to which the own device belongs.

7. The wireless communication device according to claim 1, wherein The control unit determines an active interval for each intermittent reception cycle, wherein the active interval is an interval obtained by assigning different offsets to each of the plurality of intermittent reception cycles.

8. A wireless communication device, characterized in that: The wireless communication device includes: a wireless communication unit that transmits and receives a signal multicast to a group including a plurality of terminal devices; and a control unit that determines a transmission timing of the signal transmitted from the wireless communication unit. The control unit selects, based on the destination information of the multicast signal, a transmission timing that becomes the active interval corresponding to a parameter related to an offset of an active interval in which the plurality of terminal devices belonging to the group can receive the signal, A wireless resource for the multicast signal is selected from wireless resources corresponding to the active interval corresponding to the parameter.

9. A wireless communication system comprising a first terminal device and a second terminal device, characterized in that: The second terminal device is the wireless communication device according to claim 1.

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