Communication device, control method, and program

Abstract

To provide a communication device, its control method, and a program by which the communication device that performs terminal-to-terminal communication performs highly accurate transmission power control.SOLUTION: When a communication device (control terminal) executing terminal-to-terminal communication in a cellular communication standard determines that the transmission power of the peer device (non-control device) in the terminal-to-terminal communication needs to be changed, YES in S606, the communication device determines a power value to which the power is changed, S607, and sends a TPC command, S611. When the peer device receives the TPC command, YES in S603, it changes the transmission power, S604.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to inter-terminal communication technology conforming to the 3rd Generation Partnership Project (3GPP (registered trademark)) standards.

Background Art

[0002] Wireless communication systems conforming to cellular communication standards such as Long Term Evolution (LTE) and 5th Generation (5G) of the 3rd Generation Partnership Project (3GPP (registered trademark)) are widely used. These cellular communication standards include specifications related to direct communication between terminals called Sidelink communication, in addition to the scheme in which a terminal communicates with other terminals via a base station.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In Sidelink communication, the transmission power when a terminal transmits a signal is fixed to a predetermined value. For this reason, the transmission power may become excessive or insufficient depending on the positional relationship between the terminals and the like. In response to this, Patent Document 1 describes a transmission power control technique for inter-terminal communication. In this transmission power control technique, within the coverage of a control station, all terminals share a flag indicating whether data can be received from other terminals, and determine their own transmission power based on these flags. However, with the technique of Patent Document 1, the terminal can only specify whether the transmitted power was successfully received by other terminals, and cannot perform highly accurate transmission power control.

Means for Solving the Problems

[0005] This invention provides a technology that enables a communication device performing inter-terminal communication to perform highly accurate transmission power control.

[0006] A communication device according to one aspect of the present invention enables terminal-to-terminal communication in cellular communication standards. Between the other device The means of communication to be used, A determination means for determining which of the communication device and the other device will operate as a control terminal to control the transmission power of the other device, based on whether the communication device transmits a predetermined signal to the other device or the communication device receives the predetermined signal from the other device, and when it is determined that the communication device will operate as the control terminal, before record It includes control means for sending a command to a remote device and controlling the transmission power of the remote device based on that command. [Effects of the Invention]

[0007] According to the present invention, a communication device that performs inter-terminal communication can perform transmission power control with high precision. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating Sidelink communication. [Figure 2] This figure shows an example of the hardware configuration of a communication device. [Figure 3] This figure shows an example of the functional configuration of a communication device. [Figure 4] This diagram shows an example of the processing flow between communication devices. [Figure 5] This diagram shows the physical layer frame format used in Sidelink communication. [Figure 6] This diagram shows an example of the processing flow performed in a communication device. [Modes for carrying out the invention]

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] (Sidelink communication) Figure 1 is a diagram illustrating the manner in which wireless communication is performed according to this embodiment. In this embodiment, communication is performed in accordance with the Long-Term Evolution (LTE) and 5G cellular communication standards of the 3rd Generation Partnership Project (3GPP®). In particular, communication devices 101 and 102 are terminals in a cellular communication system and are configured to communicate with, for example, a nearby base station. On the other hand, in this embodiment, communication devices 101 and 102 communicate directly without going through a base station, as shown in Figure 1. In this embodiment, it is assumed that this direct communication is performed using NR (New Radio) Sidelink communication or V2X (Vehicle-to-Everything) Sidelink communication as defined in the above-mentioned cellular communication standards. Hereinafter, such communication will be referred to as Sidelink communication or SL communication. Note that at least one of communication devices 101 and 102 may be located within a coverage area where it can connect to a base station, or both may be located outside a coverage area. It should be noted that Sidelink communication is merely presented as an example of inter-terminal communication compliant with cellular communication standards, and the following arguments can also be applied to inter-terminal communication other than the inter-terminal communication defined as Sidelink communication above. For example, the following arguments can be applied to inter-terminal communication in 5G Advanced, the successor standard to 5G, and to inter-terminal communication in 6G, a further successor standard.

[0011] In this embodiment, communication devices 101 and 102 perform transmit power control when performing Sidelink communication. Here, either communication device 101 or communication device 102 acts as a control terminal that takes the lead in transmit power control, while the other acts as a controlled terminal that performs transmit power control under the control of the control terminal. The control terminal then determines the transmit power that should be used to transmit the wireless signal at the other device (controlled terminal) based on the received power of the wireless signal from the other device, and uses a transmit power control command to control the other device to transmit the wireless signal at that transmit power. The roles of the control terminal and the controlled terminal may be determined dynamically, for example, based on the criteria described later.

[0012] The following section provides a detailed explanation of the device configuration of a communication device that performs such processing, and an example of the processing flow that is executed. In the following, unless otherwise specified, communication device 101 and communication device 102 will simply be referred to as "communication device" or UE (User Equipment).

[0013] (Device configuration) Figure 2 shows an example of the hardware configuration of a communication device. The communication device includes a storage unit 201, a control unit 202, a wireless communication unit 203, and an antenna 204 as its hardware configuration. Note that these hardware blocks are just an example, and the communication device may include, for example, further hardware blocks. Also, two or more hardware blocks in Figure 2 may be implemented as a single integrated hardware block, or a single hardware block may be divided into multiple hardware blocks.

[0014] The storage unit 201 is configured to include, for example, memory such as Read Only Memory (ROM) or Random Access Memory (RAM). The storage unit 201 stores various information such as programs for performing the various operations described later, and communication parameters for wireless communication. In addition to memory such as ROM and RAM, the storage unit 201 may also include storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs. Furthermore, the storage unit 201 may include multiple memories.

[0015] The control unit 202 is composed of, for example, a processor such as a CPU or MPU, an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or a field-programmable gate array (FPGA). Here, CPU is an acronym for Central Processing Unit, and MPU is an acronym for Micro Processing Unit. The control unit 202 controls the entire communication device, for example, by executing a program stored in the memory unit 201. The control unit 202 may also control the communication device in cooperation with the program stored in the memory unit 201 and the operating system (OS). Furthermore, the control unit 202 may include multiple processors, such as a multi-core processor.

[0016] The wireless communication unit 203 is configured to include hardware (for example, a radio frequency (RF) chip, a baseband chip, etc.) for performing wireless communication conforming to the 3GPP (registered trademark) cellular communication standard. The wireless communication unit 203 controls the corresponding antenna 204 to transmit and receive radio signals for wireless communication. Note that although FIG. 2 shows a configuration with one antenna 204, a plurality of antennas may be used. The wireless communication unit 203 is configured to be capable of executing, for example, Sidelink communication such as NR Sidelink communication and V2X Sidelink communication with other UEs in addition to communication with a base station. As shown in FIG. 2, the wireless communication unit 203 is configured to include a communication control unit 211, a modulation unit 212, a transmission amplification unit 213, a reception strength measurement unit 214, a reception amplification unit 215, and a demodulation unit 216.

[0017] The communication control unit 211 controls other components (the modulation unit 212 to the demodulation unit 216) to perform wireless communication.

[0018] The modulation unit 212 performs primary modulation and secondary modulation on transmission data to be transmitted by wireless communication, and further performs processing such as frequency conversion to generate a signal that can be transmitted through the antenna 204. Here, the primary modulation can be a process of mapping a data sequence to signal points in an IQ plane composed of an in-phase component and a quadrature component. As the modulation scheme for primary modulation, for example, PSK (Phase Shift Keying) and QAM (Quadrature Amplitude Modulation) are used. Note that PSK includes BPSK (Binary PSK), QPSK (Quadrature PSK), and the like, and QAM includes 16QAM, 64QAM, 256QAM, and the like. A modulation scheme with a larger number of points on the IQ plane can increase the amount of data that can be transmitted at one signal point. The secondary modulation is modulation on the frequency axis, and performs, for example, Orthogonal Frequency Division Multiplexing (OFDM), spreading using a spreading code, frequency hopping, and the like. The frequency conversion includes, for example, conversion of a baseband frequency signal into a radio frequency (RF) signal. The signal modulated by the modulation unit 212 is amplified by the transmission amplification unit 213 and transmitted via the antenna 204.

[0019] A signal transmitted from another terminal is received via an antenna 204, and the intensity thereof is measured in a received intensity measurement unit 214. Further, the received signal is amplified in a reception amplification unit 215 and input to a demodulation unit 216. The demodulation unit 216 converts the input signal into, for example, a baseband signal, performs secondary demodulation corresponding to secondary modulation and primary demodulation corresponding to primary modulation, and acquires data transmitted from another device. The reception amplification unit 215 is configured to include, for example, a low-noise amplifier (LNA), and can amplify a received signal of minute power received via the antenna 204. Note that the power consumption of the reception amplification unit 215 generally varies depending on the input signal intensity. For example, when the input signal intensity is low, the power consumption may increase. On the other hand, when the input signal intensity is too high, the signal may be distorted, and the demodulation performance may deteriorate. Therefore, when high-accuracy transmission power control as described later is performed, the demodulation performance can be maintained sufficiently high while suppressing an increase in power consumption.

[0020] Figure 3 shows an example of the functional configuration of a communication device. The functions in Figure 3 can be implemented, for example, by the communication control unit 211 executing pre-programmed processes. Alternatively, each function may be implemented by the control unit 202 executing a program stored in the storage unit 201. Alternatively, each function may be implemented by the communication control unit 211 operating according to the control of the control unit 202. Note that the functional configuration example in Figure 3 is just one example, and at least some of these functions may be omitted, or further additional functions may be added. Also, each functional block is shown schematically, and multiple functional blocks may be combined into one functional block, or one functional block may be divided into multiple functional blocks. The signal receiving unit 301 and the signal transmitting unit 302 perform wireless communication with other terminal devices or with base stations according to communication standards such as LTE or 5G. The data storage unit 303 performs control to store software and information related to wireless communication in the storage unit 201. The connection control unit 304 performs control to establish or disconnect connections at various layers, such as the radio resource control (RRC) layer, with terminals and core network functions. The connection control unit 304 performs tasks such as sending and receiving RRC messages, and sending and receiving information from the physical layer and media access control (MAC) layer.

[0021] (Process flow) Next, an example of the communication processing flow according to this embodiment will be explained using Figure 4. Figure 4 shows an example of processing according to this embodiment when either the communication device 101 or the communication device 102 functions as the control terminal 411 and the other functions as the controlled terminal 412. For example, the device that requests the setup of the RRC connection may function as the control terminal, and the device that receives the request may function as the controlled terminal. However, this is just an example, and the device that receives the request may function as the control terminal, and the device that sends the request may function as the controlled terminal. Here, the role of control terminal or controlled terminal is determined based on whether the device is the sending or receiving device of the setup request, but the role may be determined based on another message in the RRC layer. For example, the role may be determined based on whether the device is the sending or receiving device of the reconfiguration message (RRC Reconfiguration). Furthermore, communication devices 101 and 102 can request channel status information (CSI) from the other device. The device requesting the CSI may function as the control terminal, and the other device may function as the controlled terminal. Alternatively, the device requesting the CSI may function as the controlled terminal, and the other device may function as the control terminal. Here, "control terminal" refers to the communication device that takes the lead in transmit power control (TPC) (issues TPC commands), and does not need to perform control other than TPC.

[0022] In the process shown in Figure 4, either communication device 101 or communication device 102 sends an RRC connection setup request (SL RRC Setup Request) for Sidelink communication (F401). In this example, the device that sent this request starts operating as the control terminal 411. The other device, upon receiving this setup request, starts operating as the controlled terminal 412 and sends an RRC connection setup message (SL RRC Setup) to the control terminal 411 (F402). Subsequently, the control terminal 411 sends a response message (SL RRC Setup Complete) to the controlled terminal 412 (F403), and the connection for Sidelink communication is established. After that, the control terminal 411 and the controlled terminal 412 perform Sidelink communication (direct communication between terminals) (F404).

[0023] Here, the controlled terminal 412 transmits a radio signal containing data (physical sidelink shared channel (PSSCH)) (F404), and the control terminal 411 determines that the received signal strength of this radio signal is not within the appropriate input range of the receiving amplifier 215. In this case, the control terminal 411 transmits a radio signal (PSSCH) containing a transmit power control (TPC) command to the controlled terminal 412, which is used to set the transmit power appropriately so that the radio signal transmitted by the controlled terminal 412 is received with an appropriate received signal strength (F406). The controlled terminal 412 extracts the TPC command from the received radio signal, increases or decreases the transmit power according to the TPC command, and transmits a radio signal using the modified transmit power (F407). The control terminal 411 also transmits a radio signal to the controlled terminal 412 as needed (F408).

[0024] Furthermore, the control terminal 411 may change the transmission power of its own device, for example, in F406 or F408. For example, if the received signal strength of the wireless signal from the controlled terminal 412 is higher than the appropriate value, the control terminal 411 can estimate that the signal transmitted by its own device will be received by the controlled terminal 412 at a signal strength higher than the appropriate value. Then, if the control terminal 411 instructs the controlled terminal 412 to lower its transmission power by a predetermined value, the control terminal 411 may also lower the transmission power of its own device by a predetermined value. Similarly, if the control terminal 411 instructs the controlled terminal 412 to increase its transmission power by a predetermined value, the control terminal 411 may also increase the transmission power of its own device by a predetermined value. If the initial transmission power at the time Sidelink communication is started between the control terminal 411 and the controlled terminal 412 is a predetermined value, such processing can keep the transmission power at both the control terminal 411 and the controlled terminal 412 consistent. Furthermore, if the performance of the amplifiers, such as the low-noise amplifier (LNA), in the receiving amplifier section 215 of the control terminal 411 and the controlled terminal 412 differs, the appropriate value of the input signal may differ. For this reason, for example, when establishing a connection, information indicating the performance of the amplifiers, such as UE Capability, may be exchanged, and the control terminal 411 may perform transmit power control based on that information. The control terminal 411 may change the transmit power of its own device at the time of sending the TPC command F406, for example, or it may perform the same transmit power change process at another timing, such as F408. Also, the control terminal 411 may change only the transmit power of the controlled terminal 412 without changing the transmit power of its own device. Furthermore, the control terminal 411 may change the transmit power of its own device without changing the transmit power of the controlled terminal 412.

[0025] The control terminal 411 can transmit a transmit power control command to the controlled terminal 412 using a physical layer frame format for Sidelink communication, such as shown in Figure 5(A) or Figure 5(B). Figure 5(A) is a format that includes two symbols of a physical sidelink control channel (PSCCH) and two symbols of demodulation reference signals (DMRS) for the PSSCH, but does not include a physical sidelink feedback channel (PSFCH). On the other hand, Figure 5(B) shows a format that includes three symbols of a PSCCH, three symbols of DMRS for the PSSCH, and a PSFCH. Among these formats, for example, TPC commands may be included in the PSSCH, PSCCH, or PSFCH. In Sidelink communication, communication control is performed in the PSSCH and PSCCH based on transmitted and received control information such as the modulation and coding scheme (MCS) and Channel State Information (CSI) Request.

[0026] A TPC command may include a change step value indicating the amount of change in transmit power, and bits (upper / lower bits) indicating whether to increase or decrease the transmit power. When the controlled terminal 412 receives this TPC command, if the upper / lower bits indicate an increase in power, it increases the transmit power by the change step value. Conversely, if the upper / lower bits in this TPC command indicate a decrease in power, the controlled terminal 412 decreases the transmit power by the change step value. The TPC command may also include a target power value. In this case, the controlled terminal 412 can set the transmit power to that target power value. A TPC command including a combination of the change step value and upper / lower bits, or a target power value, may be defined as an option. In this case, power control may not be performed by leaving the combination of the change step value and upper / lower bits, or the target power value blank. In the example format described above, transmit power control is performed at the physical layer, but transmit power control may also be performed at a higher layer, such as the Media Access Control (MAC) layer, using messages from that layer.

[0027] Next, an example of the processing flow performed by the communication device will be explained using Figure 6. Note that the processing example shown in Figure 6 is just one example; for example, some processing steps may be omitted, or additional processing steps may be added. Furthermore, multiple processing steps may be combined into one processing step, or one processing step may be divided into multiple processing steps. Also, the order of the processing steps may be changed.

[0028] First, the communication device determines whether to operate as a control terminal or a controlled terminal (S601). The communication device may determine whether to operate as a control terminal based on whether it is the device that sends messages such as setup requests or reconfiguration requests for the Radio Resource Control (RRC) layer, or the device that receives those messages, as described above. Alternatively, the communication device may determine whether to operate as a control terminal based on whether it is the device that sends request messages related to composite automatic retransmission requests (HARQ) or channel status information (CSI), or the device that receives those messages. Furthermore, the communication device may determine whether to operate as a control terminal if the value of identification information such as device ID, MAC address, or IMSI is larger for both the device and the other device, and whether to operate as a controlled terminal if the value is smaller. Alternatively, the communication device may determine whether to operate as a control terminal if the value is smaller, and as a controlled terminal if the value is larger.

[0029] If the communication device is operating as a controlled terminal (NO in S602), it determines whether or not it has received a TPC command from the other device operating as a control terminal (S603). If the communication device has not received a TPC command (NO in S603), it terminates processing without performing any further operations. On the other hand, if the communication device has received a TPC command (YES in S603), it changes the transmission power according to the command (S604) and continues communication.

[0030] When the communication device is operating as a control terminal (YES in S602), it measures the received strength of the radio signal transmitted from the other device and compares the value Pr, which indicates the received power, with the value Pin, which indicates the input range of the receiving amplifier 215 of its own device (S605). The communication device then decides, for example, whether to change the transmission power of the other device based on the comparison result (S606). The value Pr, which indicates the received power, may be, for example, the average received power of the signal over a certain period (for example, the average received power of the entire radio signal transmitted in one go). Alternatively, the value Pr, which indicates the received power, may be calculated based on, for example, the received power of a reference signal. The value Pin, which indicates the input range, may be, for example, the range of input power values ​​of an amplifier (e.g., LNA) that can perform proper amplification, with a lower limit of an input power value that can sufficiently suppress the effects of noise and an upper limit of an input power value that does not cause signal distortion due to clipping, etc. In this case, the communication device decides, for example, that the transmission power of the other device should be changed if Pr exceeds the upper limit of Pin or if Pr falls below the lower limit of Pin. Furthermore, the value Pin, which indicates the input range, may be the median value of the appropriate input power levels. In this case, the communication device may decide to change the transmission power of the other device when the difference between Pr and Pin exceeds a predetermined value. The communication device may also decide to change the transmission power of the other device when Pr remains at an inappropriate value compared to Pin for a predetermined period of time or longer. In other words, even if Pr is at an inappropriate value compared to Pin, the communication device may not change the transmission power of the other device if that condition does not persist for a predetermined period of time or longer. The communication device may also decide to control the transmission power of the other device regardless of the relationship between Pr and Pin. For example, the communication device may decide to set the transmission power of the other device when a predetermined period of time or more has elapsed since the last transmission power control was performed. The communication device may also decide to change the transmission power of the other device when the amount of change in Pr within a certain period of time exceeds a predetermined value.

[0031] If the communication device decides not to change the transmission power of the other device (NO in S606), it terminates processing. On the other hand, if the communication device decides to change the transmission power of the other device (YES in S606), it determines the power value P_controlled to be changed (S607). For example, the communication device may decide how much to increase or decrease the transmission power based on the values ​​of Pr and Pin. The communication device may also determine P_controlled so that Pr falls within an appropriate input range. Furthermore, the communication device may determine P_controlled so that the transmission power reaches a predetermined value if a predetermined time has elapsed since the last transmission power control was performed. In addition, the communication device may change not only the transmission power of the other device but also the transmission power of its own device, and may determine the power value P_control for that purpose.

[0032] The communication device determines whether to change the power change steps ΔP_control and ΔP_controlled, which specify by how much the transmission power should be increased or decreased (S608). Note that ΔP_control is the power change step for transmission power at the control terminal 411, and ΔP_controlled is the power change step for transmission power at the controlled terminal 412. If the communication device decides to change the power change step (YES in S608), it determines and changes the power change step (S609). On the other hand, if the communication device decides not to change the power change step (YES in S608), it does not perform the determination and change process of the power change step in S609.

[0033] The communication device may, for example, determine in S607 whether or not to change the power change step based on the difference between Pr and Pin. The communication device may, for example, determine the range of power to be increased or decreased in order to bring Pr to an appropriate value as the power change step. For example, |Pr-Pin| may be used as the power change step, or α×|Pr-Pin| (where 0<α<1) may be used as the power change step. Furthermore, if the amount of movement of the self-device and the other-device is known, the communication device may change the power change step if the amount of movement within a certain period exceeds a predetermined value. For example, if the amount of movement of at least one of the self-device and the other-device exceeds a predetermined value, the communication device may increase the power change step in order to quickly track the transmission power to an appropriate value. When the amount of movement is large, it is expected that the communication situation will change significantly in a short period of time, and therefore the appropriate transmission power may change significantly in a short period of time. For this reason, the communication device can increase the probability of being able to communicate with an appropriate transmission power by increasing the power change step and improving the tracking ability of the transmission power. On the other hand, when the amount of movement is small, the communication conditions are expected to remain generally constant. Therefore, the communication device can reduce the power change step to suppress the probability of the transmission power becoming an inappropriate value. The amount of movement can be calculated or estimated based on, for example, measurements from positioning or acceleration sensors, or images captured by the imaging functions of the communication device and the receiving device.

[0034] Then, the communication device changes its own transmission power by ΔP_control (S610) and sends a TPC command to change the other device's transmission power by ΔP_controlled (S611), and then terminates processing.

[0035] Through the above processing, it becomes possible to control the transmission power in terminal-to-terminal communication under the cellular communication standard with high precision. Note that the above configuration examples and processing examples can be used in any combination unless otherwise specified.

[0036] (Summary of the embodiments) At least some of the embodiments described above can be summarized as follows:

[0037] [Item 1] A communication means for performing terminal-to-terminal communication in cellular communication standards, Control means for sending a command to the other device in the aforementioned inter-terminal communication and controlling the transmission power of the other device based on the command, A communication device characterized by having the following features.

[0038] [Item 2] The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means controls the transmission power of the other device based on the measured received signal strength. A communication device as described in item 1, characterized by the features described herein.

[0039] [Item 3] The communication device according to item 2, characterized in that the control means further controls the transmission power of the other device based on the input range of an amplifier that amplifies the wireless signal transmitted from the other device.

[0040] [Item 4] The communication device according to any one of items 1 to 3, characterized in that the control means further controls the transmission power of the communication device.

[0041] [Item 5] The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means controls the transmission power of the communication device based on the measured received signal strength. A communication device as described in item 4, characterized by the features described herein.

[0042] [Item 6] The device further includes a determination means for determining which of the communication device and the other device will operate as a control terminal that controls the transmission power. The control means controls the transmission power of the other device when it is determined that the communication device will operate as the control terminal. A communication device as described in item 4 or 5, characterized by the features described herein.

[0043] [Item 7] The communication device according to item 6, characterized in that the determination means determines that the device that transmits a predetermined signal among the communication device and the other device will operate as the control terminal.

[0044] [Item 8] The communication device according to item 7, characterized in that the predetermined signal is one of the following: a message from the Radio Resource Control (RRC) layer, a request for Channel Status Information (CSI), or a combined automatic retransmission request (HARQ) message.

[0045] [Item 9] The communication device according to item 6, characterized in that the determination means determines that the device that receives a predetermined signal from the communication device and the other device will operate as the control terminal.

[0046] [Item 10] The communication device according to item 9, characterized in that the predetermined signal is one of the following: a message from the Radio Resource Control (RRC) layer, a request for Channel Status Information (CSI), or a composite automatic retransmission request (HARQ) message.

[0047] [Item 11] The communication device according to any one of items 1 to 10, characterized in that the control means determines whether or not to send the command, sends the command to the other device if it is decided to send the command, and does not send the command to the other device if it is decided not to send the command.

[0048] [Item 12] The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The communication device according to item 11, characterized in that the control means decides to transmit the command when the amount of change in the received signal strength within a certain period of time is greater than or equal to a predetermined value.

[0049] [Item 13] The communication device according to item 11, characterized in that the control means decides to send the next command based on the fact that a predetermined time has elapsed since the transmission of the command.

[0050] [Item 14] The communication device according to any one of items 1 to 13, characterized in that the control means sets the range of change when changing the transmission power, and transmits information indicating the range of change and information indicating whether to increase or decrease the transmission power as a command to the other device.

[0051] [Item 15] The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means sets the change range based on the amount of change in the received signal strength, or based on the amount of movement within a certain period in at least one of the communication device and the other device. A communication device as described in item 14, characterized by the features described herein.

[0052] [Item 16] The communication device according to item 4, characterized in that the control means sets the range of change when changing the transmission power, and increases or decreases the transmission power of the communication device by the range of change.

[0053] [Item 17] The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means sets the change range based on the amount of change in the received signal strength, or based on the amount of movement within a certain period in at least one of the communication device and the other device. A communication device as described in item 16, characterized by the features described herein.

[0054] [Item 18] A communication means for performing terminal-to-terminal communication in cellular communication standards, Receiving means for receiving a command to control the transmission power from the other device in the aforementioned inter-terminal communication, A control means for controlling the transmission power of the wireless signal to be transmitted to the other device based on the command, A communication device characterized by having the following features.

[0055] [Item 19] A control method performed by a communication device that performs terminal-to-terminal communication in a cellular communication standard, A control method characterized by including sending a command to a remote device in the aforementioned inter-terminal communication and controlling the transmission power of the remote device based on the command.

[0056] [Item 20] A control method performed by a communication device that performs terminal-to-terminal communication in a cellular communication standard, Receiving a command from the other device in the aforementioned inter-terminal communication to control the transmission power, Based on the aforementioned command, the transmission power of the wireless signal to be sent to the other device is controlled, A control method characterized by including

[0057] [Item 21] A program to cause a computer to function as one of the means of a communication device described in any one of items 1 through 18.

[0058] <Other Embodiments> The present invention provides a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium. It can also be implemented by a process in which one or more processors in the computer of the system or device read and execute the program. Furthermore, it can also be implemented by a circuit (e.g., an ASIC) that implements one or more functions.

[0059] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0060] 101, 102: Communication device, 203: Wireless communication unit, 211: Communication control unit, 213: Transmitting amplifier unit, 214: Received signal strength measurement unit, 215: Receiving amplifier unit

Claims

1. A communication device, A communication means for performing terminal-to-terminal communication with a partner device in the cellular communication standard, A determination means for determining which of the communication device and the other device will operate as a control terminal to control the transmission power of the other device, based on whether the communication device transmits a predetermined signal to the other device or the communication device receives the predetermined signal from the other device, When the communication device is determined to operate as the control terminal, a control means sends a command to the other device and controls the transmission power of the other device based on the command, A communication device characterized by having the following features.

2. The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, When the communication device determines that it will operate as the control terminal, the control means controls the transmission power of the other device based on the measured received signal strength. The communication device according to feature 1.

3. The communication device according to claim 2, wherein the control means further controls the transmission power of the other device based on the input range of an amplifier that amplifies the wireless signal transmitted from the other device when the communication device decides to operate as the control terminal.

4. The communication device according to claim 1, further comprising the control means controlling the transmission power of the communication device when it is determined that the communication device will operate as the control terminal.

5. The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means controls the transmission power of the communication device based on the measured received signal strength. The communication device according to feature 4.

6. The communication device according to claim 1, characterized in that the determination means determines that the communication device will operate as the control terminal when it transmits the predetermined signal to the other device.

7. The communication device according to claim 6, characterized in that the predetermined signal is one of a message from the Radio Resource Control (RRC) layer, a Channel Status Information (CSI) request, or a Combined Automatic Retransmission Request (HARQ) message.

8. The communication device according to claim 1, characterized in that the determination means determines that the communication device will operate as the control terminal when it receives the predetermined signal from the other device.

9. The communication device according to claim 8, characterized in that the predetermined signal is one of a message from the Radio Resource Control (RRC) layer, a Channel Status Information (CSI) request, or a Combined Automatic Retransmission Request (HARQ) message.

10. The communication device according to claim 1, characterized in that the control means determines whether or not to send the command when the communication device is operating as the control terminal, sends the command to the other device if it is decided to send the command, and does not send the command to the other device if it is decided not to send the command.

11. The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The communication device according to claim 10, characterized in that the control means determines to transmit the command when the communication device is operating as the control terminal and the amount of change in the received signal strength within a certain period of time is greater than or equal to a predetermined value.

12. The communication device according to claim 10, characterized in that when the communication device is operating as the control terminal, the control means decides to send the next command based on the fact that a predetermined time has elapsed since the transmission of the previous command.

13. The communication device according to claim 1, characterized in that, when the communication device operates as the control terminal, the control means sets the range of change when changing the transmission power of the other device, and transmits information indicating the range of change and information indicating whether to increase or decrease the transmission power as a command to the other device.

14. The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means sets the change range based on the amount of change in the received signal strength, or based on the amount of movement within a certain period in at least one of the communication device and the other device. The communication device according to feature 13.

15. The communication device according to claim 4, characterized in that the control means sets a change range when changing the transmission power of the communication device when the communication device is operating as the control terminal, and increases or decreases the transmission power of the communication device by the change range.

16. The device further includes a measuring means for measuring the received signal strength of a wireless signal transmitted from the aforementioned other device, The control means sets the change range based on the amount of change in the received signal strength, or based on the amount of movement within a certain period in at least one of the communication device and the other device. The communication device according to feature 15.

17. When the other device decides to operate as the control terminal, the device further has receiving means for receiving a command from the other device to control the transmission power, The control means controls the transmission power of the communication device based on the command. The communication device according to feature 1.

18. A control method performed by a communication device that performs terminal-to-terminal communication with a partner device in a cellular communication standard, Based on whether the communication device transmits a predetermined signal to the other device, or whether the communication device receives the predetermined signal from the other device, it is determined which of the communication device and the other device will act as a control terminal to control the transmission power of the other device. When the communication device decides to operate as the control terminal, it sends a command to the other device and controls the transmission power of the other device based on that command. A control method characterized by including

19. A program for causing a computer to function as one of the means of a communication device according to any one of claims 1 to 17.

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