Method, information processing device, and program

Abstract

The present invention improves the efficiency of reporting information on the propagation characteristics of a received signal by a receiving-side device. In the present invention, a computer executes: acquiring the coherent bandwidth of a first signal received by the receiving-side device; and acquiring, on the basis of the coherent bandwidth of the first signal, the number of sub-bands when the receiving-side device acquires information on the propagation characteristics in each of a plurality of sub-bands of the first signal.

Description

Method, Information Processing Apparatus, and Program

[0001] The present disclosure relates to wireless communication.

[0002] In wireless communication such as 5th Generation Mobile Communication System (5G), distributed MIMO (Multi-Input Multi-Output) is proposed in which one or more distributed stations near a mobile station are selected from a plurality of distributed stations distributed within the communication area of one base station for communication. According to distributed MIMO, by appropriately combining radio waves simultaneously transmitted from a plurality of distributed stations, the received signal power at the mobile station can be improved and the throughput can be increased.

[0003] In cooperative transmission between a plurality of distributed base stations (mTRP, hereinafter referred to as distributed stations) such as distributed MIMO, a technique for improving the received signal power by ensuring that the transmission signals from each distributed station are received in the same phase at the UE (User Equipment) is called Coherent Joint Transmission (CJT). For example, in cooperative transmission by N distributed stations, assuming that the transmission power of each distributed station is equal, theoretically, the received signal power at the UE becomes N squared times the received signal power of the signal from one distributed station by CJT. By improving the received signal power by CJT, improvement in throughput and reduction in latency can be achieved.

[0004] When there is an offset in the phase of the carrier wave between a plurality of distributed stations performing cooperative transmission, a loss of received signal power occurs when the received signals at the UE are combined. The loss of received signal power is the difference between the theoretical value of the received signal power obtained by CJT and the actually obtained received signal. In order to correct the phase offset of the carrier wave of each distributed station, the UE measures the phase offset value for each distributed station and reports it to each distributed station.

[0005] One method for reporting phase offset by a UE is to divide the channel bandwidth of a transmitted signal from a single distributed station into a predetermined number of subbands, measure the phase offset for each subband, and report it (for example, Non-Patent Document 1).

[0006] 3GPP TSG RAN WG1 #117 R1-2405486 (2024-05-20)3GPP TSG RAN Meeting #104 RP-240087 (2004-03-18)3GPP TS 38.214 V18.2.0 (2024-03)

[0007] One aspect of this disclosure is to provide a method, an information processing device, and a program that can improve the efficiency of information regarding the propagation characteristics of a received signal by a receiving device.

[0008] One aspect of the present disclosure is a method by which a computer performs the following: obtains the coherent bandwidth of a first signal received by a receiving device; and, based on the coherent bandwidth of the first signal, obtains the number of subbands in which the receiving device obtains information regarding the propagation characteristics in each of a plurality of subbands of the first signal.

[0009] Another aspect of the present disclosure is an information processing device comprising: a control unit that performs the following: obtaining the coherent bandwidth of a first signal received by a receiving device; and obtaining the number of subbands in which the receiving device obtains information regarding the propagation characteristics in each of a plurality of subbands of the first signal, based on the coherent bandwidth of the first signal.

[0010] Another aspect of the present disclosure is a program for causing a computer to perform the following actions: obtain the coherent bandwidth of a first signal received by a receiving device; and obtain the number of subbands in the information regarding the propagation characteristics of each of the multiple subbands of the first signal obtained by the receiving device, based on the coherent bandwidth of the first signal.

[0011] According to one aspect of this disclosure, a method, an information processing device, and a program can be provided that can improve the efficiency of reporting information on propagation characteristics by a receiving device.

[0012] Figure 1 is a diagram showing an example of the system configuration of a communication system according to the first embodiment. Figure 2 is an example of the CJT sequence in the communication system. Figure 3 is a graph showing an example of the measurement result of the phase offset of the target signal from the received signal from a reference transmission point in the frequency domain. Figure 4 is a diagram illustrating the hardware configuration of the control device. Figure 5 is a diagram showing an example of the functional configuration of the control device. Figure 6 is an example of the flowchart for the subband number determination process for measuring the phase offset of the control device. Figure 7 is a diagram showing an example of the impulse response h_(n) in the time domain of the received signal. Figure 8 is a setting table of subband size sets corresponding to the number of resource blocks included in the channel bandwidth disclosed in Table 5.2.1.4-2 of 3GPP TS38.214.

[0013] When acquiring and reporting information on the propagation characteristics of a received signal across multiple subbands, an appropriate number of subbands can be obtained by bringing the subband size closer to a bandwidth where the characteristics of the received signal in the frequency domain can be considered constant. This allows for efficient reporting of information on the propagation characteristics of a received signal across multiple subbands. For example, when measuring the phase offset of a received signal from a reference transmission point to a received signal from another transmission point (the target signal) across multiple subbands, in the case of received signals from two co-transmitted transmission points, an appropriate number of subbands can be determined by bringing the subband size closer to a frequency bandwidth where the phase offset can be considered constant. An appropriate number of subbands for phase offset measurement is one that improves the accuracy of phase correction of the target signal while keeping the data size of the reported phase offset values ​​of the target signal in each subband low. A bandwidth in which fluctuations can be considered constant in the frequency domain is called a coherent bandwidth.

[0014] The coherent bandwidth of the phase offset of the target signal from the received signal at the reference transmission point is substituted with the coherent bandwidth of the target signal to determine the number of subbands for measuring the phase offset of the target signal from the received signal at the reference transmission point. The propagation characteristic information obtained using the number of subbands obtained based on the coherent bandwidth of the received signal is not limited to the phase offset of the target signal from the received signal at the reference transmission point. In addition to the phase offset, the propagation characteristic information obtained using the number of subbands obtained based on the coherent bandwidth of the received signal may include, for example, amplitude and channel status information (CSI) which are frequency selective.

[0015] One aspect of the present disclosure is a method by which a computer performs the following actions: obtains the coherent bandwidth of a first signal received by a receiving device; and, based on the coherent bandwidth of the first signal, obtains the number of subbands in which the receiving device obtains information regarding the propagation characteristics of each of a plurality of subbands of the first signal.

[0016] The computer performing the method is, for example, a computer that operates as a control device for controlling a base station. However, it is not limited to this, and the computer may be a computer installed in the base station. The receiving equipment is, for example, a terminal station and a relay station. The terminal station is, for example, a mobile station of a user terminal such as a smartphone, tablet terminal, and in-vehicle device. However, it is not limited to this, and the terminal station may be a stationary terminal that does not move.

[0017] The number of subbands may be determined based on the subband size, which is obtained based on the coherent bandwidth of the first signal, and the channel bandwidth of the first signal. Alternatively, the computer may select the subband size from among 1, 2, 4, 8, and 16 physical resource blocks, according to the coherent bandwidth of the first signal.

[0018] According to one aspect of this disclosure, the number of subbands when acquiring information on the propagation characteristics of the first signal is acquired based on the coherent bandwidth of the first signal. This makes it possible to maintain the highest possible accuracy of the information on the propagation characteristics of the first signal while suppressing the overhead in reporting information on the propagation characteristics of the first signal in multiple subbands, thereby improving the efficiency of reporting. When reporting the measurement of the phase offset in multiple subbands of the first signal from the received signal from a reference transmission point, it is possible to maintain the highest possible accuracy of phase correction of the first signal while suppressing overhead, thereby suppressing the loss of received signal power during coherent synthesis and enabling efficient phase correction.

[0019] In one aspect of the present disclosure, the computer may further notify the receiving device of an instruction to acquire information regarding the propagation characteristics of a first signal in each of a plurality of subbands, and the number of subbands. When the receiving device receives a plurality of received signals from a plurality of transmission points, and the propagation characteristic information is the phase offset of the first signal from the received signal from a reference transmission point among the plurality of transmission points, the computer may further perform the following actions: receive from the receiving device the acquisition results of information regarding the propagation characteristics of the first signal in each of the plurality of subbands; acquire a phase correction value for the first signal based on the acquisition results; and cause the transmission point of the first signal to transmit the signal using a carrier wave whose phase has been corrected based on the phase correction value. This increases the likelihood that the first signal will arrive at the receiving device in phase with the signal from the reference transmission point, thereby improving the received signal power, improving throughput, and reducing latency.

[0020] Another aspect of this disclosure can also be identified as an information processing device that performs the processing of the above method. The information processing device includes a control unit that performs the following: obtaining the coherent bandwidth of a first signal received by a receiving device; and obtaining the number of subbands in which the receiving device obtains information regarding the propagation characteristics in each of a plurality of subbands of the first signal, based on the coherent bandwidth of the first signal. The control unit is, for example, a processor such as a CPU (Central Processing Unit).

[0021] Another embodiment of the method can also be defined as a program for causing a computer to execute, and a computer-readable, non-temporary storage medium on which the program is recorded.

[0022] Embodiments of this disclosure will be described below with reference to the drawings. The configurations of the following embodiments are illustrative, and this disclosure is not limited to the configurations of these embodiments.

[0023] <First Embodiment> Figure 1 is a diagram showing an example of the system configuration of the communication system 100 according to the first embodiment. The communication system 100 is a distributed MIMO system including user equipment (UE) 2, a control device 1, and a plurality of distributed base stations. The communication system 100 is a wireless communication system of mobile communication methods such as 5G, LTE (Long Term Evolution), and 6G or later. The control device 1 is a device on the core network to which the distributed base stations are connected. However, it can also be considered that the control device 1 is the core network itself, or a system included in the core network. The core network includes, for example, an optical fiber network. The control device 1 controls the distributed base stations and the UE 2.

[0024] The distributed base stations, together with other distributed base stations within the same communication area, provide a wireless access network to UE 2 located within that communication area. The three distributed base stations (RU#1 to #3) shown in Figure 1 are assumed to be located within the same communication area. Each distributed base station is connected to the control unit 1.

[0025] A distributed base station is equipped with an antenna capable of forming multiple beam patterns. The antenna used in a distributed base station is, for example, an adaptive array antenna. An adaptive array antenna is an array antenna in which multiple antenna elements are arranged. The adaptive array antenna can electrically change its beam pattern by adaptively controlling the weighting of each antenna element according to the radio wave propagation environment. A beam pattern can also be described as the directivity of the beam formed by the adaptive array antenna. The beam pattern of a distributed base station is controlled by a control device 1. Note that a distributed base station may have one antenna or multiple antennas.

[0026] UE 2 is a terminal station such as a smartphone, tablet, wearable device, or in-vehicle data communication device. However, it is not limited to this, and UE 2 may be a stationary terminal device. Alternatively, a relay station that relays wireless communication between a distributed base station and a terminal station can be used as a mobile station instead of UE 2. Relay stations include, for example, small base stations, mobile base stations, in-vehicle devices, and smartphones. In the first embodiment, UE 2 is equipped with one antenna. However, it is not limited to this, and UE 2 may be equipped with multiple antennas.

[0027] In the example shown in Figure 1, distributed base station RU#1 includes transmitting points m_(0), m_(1), and m_(2), distributed base station RU#2 includes transmitting points m_(3) and m_(4), and distributed base station RU#3 includes transmitting points m_(5) and m_(6). Distributed base station RU#1 transmits three beams: b0, b1, and b2. Distributed base station RU#1 is also represented as the transmitting points m_(0), m_(1), and m_(2) of beams b0, b1, and b2. The characters after the underscore or in parentheses are shown as subscripts in the figure. Distributed base station RU#2 transmits two beams: b3 and b4. Distributed base station RU#3 transmits two beams: b5 and b6. UE 2 uses the beam with the best communication quality from among beams b0-b6 to perform communication. UE 2 is an example of a "receiving device". Hereafter, distributed base stations will simply be referred to as distributed stations.

[0028] UE 2 receives signals transmitted from each distributed station's transmission point using each beam pattern. The objective of CJT is for the signals transmitted from each distributed station's transmission point using each beam pattern to reach UE 2 in phase. To achieve this, it is required that each transmission point transmits a carrier wave with phase correction equal to the offset from the received signal from the reference transmission point. The reference transmission point is selected by the control device 1 from among multiple transmission points that perform coordinated transmission to UE 2. The signal whose phase offset is to be measured will be referred to as the "target signal" below. The transmission point or distributed station that is the source of the target signal will be referred to as the "target transmission point" or "target distributed station". Furthermore, when "phase offset" is referred to below, it will refer to the phase offset of the target signal from the received signal from the reference transmission point.

[0029] The phase offset of the target signal is measured by UE 2 and reported to the control device 1. In the first embodiment, UE 2 divides the channel bandwidth of the target signal into a plurality of subbands and measures the phase offset for each subband. In the first embodiment, the control device 1 determines the number of subbands for phase offset measurement for each of the plurality of transmission points that perform coordinated transmission by UE 2, and notifies UE 2 of this along with the instruction to measure the phase offset.

[0030] Figure 2 shows an example of a CJT sequence in the communication system 100. In Figure 2, it is assumed that distributed station #1 and distributed station #2 each have one antenna (or transmission point). Therefore, in Figure 2, a distributed station equals one transmission point.

[0031] In S11, the control device 1 selects distributed stations to perform coordinated transmission to UE 2. In the selection of distributed stations in S11, the number of distributed stations to perform coordinated transmission to UE 2 and the reference distributed station are also selected. The method for selecting the distributed stations to perform coordinated transmission to UE 2 and the method for selecting the reference distributed station are not limited to any particular method. In Figure 2, it is assumed that distributed station #1 and distributed station #2 have been selected, and distributed station #1 has been selected as the reference.

[0032] In S12, the control device 1 determines the number of subbands for measuring the phase offset of the signal transmitted from distributed station #2. Details of the process for determining the number of subbands for the phase offset will be described later.

[0033] In S13, the control device 1 allocates radio resources for phase offset measurement to distributed station #1 and distributed station #2. For measuring the phase offset, for example, a CSI-RS (Channel State Information Reference Signal), a signal for measuring the phase offset, or a data signal may be used.

[0034] In S14, the control device 1 notifies distributed station #1 and distributed station #2 of the allocation of radio resources for phase offset measurement determined in S13. In S15, the control device 1 notifies UE 2 of the number of distributed stations and the number of subbands for each distributed station other than the reference station (distributed station #2 in Figure 2).

[0035] In S16, distributed station #1 and distributed station #2 transmit phase offset measurement signals using the instructed radio resources. In S17, UE 2 receives phase offset measurement signals from distributed station #1 and distributed station #2, and measures the phase offset from the received signal of distributed station #1 (reference signal) for each of the specified number of subbands for the received signal from distributed station #2. In S18, UE 2 reports the measurement results of the phase offset of the received signal from distributed station #2 to the control device 1.

[0036] In S21, the control device 1 calculates a phase correction value for the carrier wave of distributed station #2 in each subband from the measurement results of the phase offset of the received signal from distributed station #2 in each subband, which was received from UE 2. The phase correction value in each subband is obtained, for example, as a value obtained by inverting the sign of the phase offset in that subband. However, this is not limited to this, and the method of determining the phase correction value is not limited to a specific method.

[0037] In S22, the control device 1 notifies distributed station #2 of the acquired phase correction values ​​for each subband. In S23, distributed station #2 performs phase correction of the carrier wave by shifting the phase of each subband of the carrier wave frequency by the amount of the notified phase correction value.

[0038] In S24, the control device 1 sends data signals to be transmitted via CJT to distributed station #1 and distributed station #2, and also notifies them of the radio resources for transmitting the data signals. In S25, distributed station #1 and distributed station #2 transmit data to UE 2 using the designated radio resources. At this time, distributed station #2 transmits data using a phase-corrected carrier wave in each subband.

[0039] In Figure 2, there are two distributed stations, but if there are three or more distributed stations, the same processing as for distributed station #2 is performed for each distributed station other than the reference distributed station, for example, in S12 (determination of the number of subbands), S14 (notification of radio resources for phase offset measurement), S17 (measurement of phase offset), S18 (reporting), S21 (calculation of phase correction value), S22 (notification of phase correction value), and S23 (phase correction).

[0040] Furthermore, Figure 2 was explained on the premise that each distributed station is equipped with one transmitting antenna (or transmitting point). If a distributed station is equipped with multiple antennas (or transmitting points), then "distributed station" in the explanation of Figure 2 should be replaced with "transmitting point". That is, for example, if a non-reference distributed station is equipped with multiple transmitting antennas and these multiple transmitting antennas are used for coordinated transmission, then for each of these multiple transmitting antennas, the following steps will be performed, for example, in S12 (determination of the number of subbands), S14 (notification of radio resources for phase offset measurement), S17 (measurement of phase offset), S18 (reporting), S21 (calculation of phase correction value), S22 (notification of phase correction value), S23 (phase correction), etc.

[0041] Also, in the example shown in FIG. 2, the phase correction value is notified from the control device 1 to the distributed station #2, and the distributed station #2 performs phase correction. However, it is not limited to this. Depending on the performance of the distributed station #2, the control device 1 may perform phase correction of the carrier wave based on the phase correction value, notify the distributed station #2 of the information about the carrier wave after phase correction, and the distributed station #2 may transmit the data signal with the carrier wave after phase correction according to the information.

[0042] FIG. 3 is a graph showing an example of the measurement result of the phase offset of the target signal from the received signal from the reference transmission point in the frequency domain. Φ_(n, j) indicates the phase offset in the sub-band j of the transmission point n. The variable n indicating the transmission point can take values from 1 to the number of transmission points N_(TRP). The variable j indicating the sub-band can take values from 0 to the number of sub-bands N_(SB-P)-1.

[0043] For example, as shown in FIG. 3, when the fluctuation of the measurement result of the phase offset of the target signal is large, if the number of sub-bands is small, the band where the phase of the target signal after phase correction is different from the received signal from the reference transmission point will increase, the phase correction accuracy will be low, and the loss of the received signal power will be large. However, if the number of sub-bands is increased, the phase correction accuracy will increase and the loss of the received signal power will decrease, but the data size when reporting from the UE 2 to the control device 1 will increase and the overhead will increase.

[0044] That is, since the phase correction accuracy (or the loss of the received signal power) and the overhead are in a trade-off relationship according to the number of sub-bands, it is required to determine the number of sub-bands so that the relationship between the phase correction accuracy and the overhead becomes appropriate. For this purpose, it is desirable to make the sub-band size close to the coherent bandwidth, which is the bandwidth in which the frequency characteristics of the phase offset of the target signal can be regarded as constant.

[0045] In the first embodiment, the control device 1 replaces the coherent bandwidth of the phase offset of the target signal with the coherent bandwidth of the target signal to obtain the subband size, and determines the number of subbands from the obtained subband size. This makes it possible to obtain a number of subbands for phase offset measurement that ensures an appropriate relationship between phase correction accuracy and overhead, thereby enabling efficient measurement and reporting of the phase offset.

[0046] Figure 4 illustrates the hardware configuration of the control device 1. The control device 1 includes a CPU 101, a main memory 102, an external memory 103, and a communication device 104. The CPU 101 is also called a processor. The CPU 101 is not limited to a single processor and may be a multi-processor configuration. In addition to the CPU 101, a Graphics Processing Unit (GPU), Digital Signal Processor (DSP), etc., may also be provided. Furthermore, the CPU 101 may be linked with hardware circuits such as a Field Programmable Gate Array (FPGA).

[0047] The CPU 101 executes a computer program deployed executable in the main memory device 102 and provides the processing of the control device 1. The main memory device 102 stores the computer program executed by the CPU 101, the data processed by the CPU 101, and the like. The main memory device 102 is a Dynamic Random Access Memory (DRAM), a Static Random Access Memory (SRAM), a Read Only Memory (ROM), or the like. Further, the external memory device 103 is used, for example, as a storage area that supplements the main memory device 102, and stores the computer program executed by the CPU 101, the data processed by the CPU 101, and the like. The external memory device 103 is a hard disk drive, a Solid State Drive (SSD), or the like. Further, a drive device for a removable storage medium may be connected to the control device 1. The removable storage medium is, for example, a Blu-ray Disc, a Digital Versatile Disc (DVD), a Compact Disc (CD), a flash memory card, or the like. The CPU 101 is an example of the "control unit" of the "information processing device".

[0048] The communication device 104 communicates with an external network such as a distributed base station and the Internet via, for example, an optical fiber. The communication device 104 of the control device 1 may be a single device or a combination of a plurality of devices. The control device 1 is an example of the "information processing device". Note that the hardware configuration of the control device 1 is not limited to that shown in FIG. 4.

[0049] FIG. 5 is a diagram showing an example of the functional configuration of the control device 1. The control device 1 includes a control unit 11 as a functional configuration. The functions of the control unit 11 are achieved by the CPU 101 executing a predetermined program.

[0050] The control unit 11 controls the CJT. More specifically, the control unit 11 selects distributed stations to perform coordinated transmission to UE 2 (S11), determines the number of subbands for phase offset measurement (S12), allocates radio resources for phase offset measurement (S13), calculates phase correction values ​​(S21), and notifies the distributed stations and UE 2 of control information and data signals (S14, S15, S22, S24), etc.

[0051] In the subband number determination process for phase offset measurement, the control unit 11 determines the coherent bandwidth of the received signal for a non-reference transmission point in UE 2, and determines the subband size with a value close to the coherent bandwidth of the received signal. The control unit 11 then determines the number of subbands from the determined subband size and the channel bandwidth of the target signal. Details of the subband number determination process for phase offset measurement will be described later.

[0052] Figure 6 is an example of a flowchart for the subband number determination process for measuring the phase offset of the control device 1. The process shown in Figure 6 is performed, for example, after the distributed station selection process has been executed and completed. The main entity executing the process shown in Figure 6 is the CPU 101 of the control device 1, but for convenience, Figure 6 will be explained mainly in terms of its functional components. Note that the process shown in Figure 6 is executed for one transmission point that is not the reference among multiple transmission points that perform coordinated transmission to UE 2. The transmission point that is the target of the process in Figure 6 is referred to as the target transmission point.

[0053] In OP11, the control unit 11 performs a fast inverse Fourier transform (IFFT) on the frequency domain propagation characteristics H_(n) of the received signal from the target transmission point in UE 2 to obtain the time domain impulse response h_(n). The propagation characteristics H_(n) are measured in UE 2, for example, by CSI-RS from the target transmission point. The propagation characteristics H_(n) may be obtained from UE 2 in the transmission point selection process (S21), or by sending a measurement request to UE 2 and receiving a report. However, the propagation characteristics H_(n) of the received signal from the target transmission point may also be obtained by the control unit 11 having the target transmission point measure it using the uplink signal transmitted from UE 2.

[0054] In OP12, the control unit 11 obtains the arrival delay τ_(k, n), which is the elapsed time until the arrival of each of the multiple delayed waves p_(k, n) of the received signal that arrives at UE2 after the second wave, from the time-domain impulse response h_(n) of the received signal from the target transmission point. The variable k indicates the arrival order of the waves of the received signal arriving at UE2. The variable k can take values ​​from 0 to the number of IFFT points N_(FFT)-1. The unit of the arrival delay τ_(k, n) is the number of points.

[0055] In OP13, the control unit 11 obtains the maximum arrival delay τ_(max) among the arrival delays of effective delayed waves. Effective delayed waves are delayed waves that are not interference waves, and more specifically, delayed waves whose received signal power (amplitude in the time domain) is greater than or equal to a predetermined threshold. First, the processing from OP11 to OP13 will be explained in more detail based on an example of the time domain impulse response h_(n) of the received signal shown in the following figure.

[0056] Figure 7 shows an example of the time-domain impulse response h_(n) of a received signal. In Figure 7, the number of points N_(FFT) of the inverse Fourier transform is 512. Therefore, the delayed wave exists from p(1,n) to p(511,n). In the graph shown in Figure 7, the horizontal axis represents time and the vertical axis represents amplitude. The amplitude of the delayed wave p_(k,n) is denoted by A_(k,n).

[0057] A valid delayed wave is one whose amplitude is greater than or equal to the value obtained by subtracting the threshold Γ_(A) from the amplitude A_(0,n) of the arrived wave p_(0,n). A delayed wave whose amplitude is less than the value obtained by subtracting the threshold Γ_(A) from the amplitude A_(0,n) of the arrived wave p_(0,n) can be considered noise. The threshold Γ_(A) is set by the administrator of the communication system 100, for example, from the allowable value of the phase measurement error based on the loss during the synthesis of the received signal allowed in CJT and the number of transmission points N_(TRP).

[0058] In the example shown in Figure 7, the latest arriving delay wave among the effective delay waves is delay wave p(16, n). Therefore, in the example shown in Figure 7, the maximum arrival delay τ_(max) is 16 points. There is a relationship in which the greater the spread of the arrival delay of the delay wave in the time domain, the more volatile the fluctuation of the received signal power in the frequency domain becomes.

[0059] Returning to Figure 6, in OP14, the control unit 11 uses the maximum arrival delay τ_ (max) to determine the coherent bandwidth σ_ (BW) of the received signal from the following equation 1. C is a coefficient that is set in advance by, for example, the administrator of the communication system 100. N_ (FFT) is the number of points in the inverse Fourier transform. If C = 1, then in the example shown in Figure 7, where the maximum arrival delay τ_(max) = 16, the coherent bandwidth σ_(BW) of the received signal is approximately 2.7 PBRs.

[0060] In OP15, the control unit 11 selects the largest value from the subband size set {1, 2, 4, 8, 16 PBRs} that is less than or equal to the coherent bandwidth σ_(BW) of the received signal as the subband size. In the example shown in Figure 7, the coherent bandwidth σ_(BW) of the received signal is approximately 2.7 PBRs, so subband size 2 is selected. Note that the method of selecting the subband is not limited to the above, and the value from the subband size set {1, 2, 4, 8, 16 PBRs} that is closest to the coherent bandwidth σ_(BW) of the received signal may be selected as the subband size.

[0061] In OP16, the control unit 11 selects the subband number N_(SB-P) as the quotient obtained by dividing the number of resource blocks included in the channel bandwidth of the target transmission point by the subband size. The channel bandwidth of the target transmission point is determined by the control unit 11, for example, in the distributed station selection (S11 in Figure 2).

[0062] In the example shown in Figure 7, the number of resource blocks for the channel bandwidth corresponding to the number of points N_(FFT) = 512 inverse Fourier transform is 25. Therefore, 25 PBRs ÷ subband size 2 PBRs = 12 remainder 1, and the number of subbands N_(SB-P) is 12.

[0063] After processing OP16, the process shown in Figure 6 is completed. Once the process shown in Figure 6 is completed, the control unit 11 notifies the UE 2 of the number of transmission points and the number of subbands for measuring the phase offset of each transmission point (Figure 2, S15).

[0064] <Effects of the First Embodiment> In the first embodiment, the number of subbands for measuring the phase offset of the received signal from the target transmission point is obtained based on the coherent bandwidth of the received signal from the target transmission point. This allows UE 2 to reduce the data size of the report of the phase offset measurement results of the received signal from the target transmission point while improving the accuracy of carrier phase correction at the target transmission point, thereby enabling efficient measurement of the phase offset.

[0065] <Modification of the First Embodiment> In the first embodiment, when determining the number of subbands for measuring the phase offset of the received signal from the target transmission point, the subband size is selected from the subband size set {1, 2, 4, 8, 16PRBs} according to the coherent bandwidth σ_(BW) of the received signal (Figure 6, OP15). Alternatively, the subband size may be selected from other subband size sets.

[0066] Figure 8 is a setting table of subband size sets corresponding to the number of resource blocks included in the channel bandwidth disclosed in Table 5.2.1.4-2 of 3GPP TS38.214. The control device 1 may identify a subband size set corresponding to the channel bandwidth of the target transmission point according to the table shown in Figure 8, and select the subband size that is closest to the coherent bandwidth of the received signal from the identified subband size set.

[0067] For example, in the example shown in Figure 7, the number of resource blocks for the channel bandwidth corresponding to the number of points N_(FFT) = 512 inverse Fourier transform is 25, so the subband size set {4, 8} corresponding to "24-72" in the Bandwidth part is selected. Of the subband size sets {4, 8}, the value "4" that is closer to the coherent bandwidth σ_(BW) = 2.7 of the received signal in the example shown in Figure 7 is selected as the subband size. Note that the subband sets and subband size sets {1, 2, 4, 8, 16PRBs} shown in Figure 8 are all examples of subband size sets used for selecting subband sizes, and are not limited to these.

[0068] <Other Embodiments> The embodiments described above are merely examples, and this disclosure may be modified as appropriate without departing from its essence.

[0069] In the first embodiment, the control device 1 determines the number of subbands for measuring the phase offset for each transmission point and notifies the UE 2. Therefore, the UE 2 measures the phase offset with a different number of subbands for each transmission point. However, it is not limited to this, and the control device 1 may notify the UE 2 of, for example, only the largest number of subbands among the number of subbands obtained for each transmission point, and the UE 2 may measure the phase offset using a common number of subbands for each transmission point. Note that the number of subbands notified to the UE 2 is not reduced to the largest number of subbands for each transmission point, but may be, for example, the average value or median of the number of subbands for each transmission point. By notifying the UE 2 of only one subband for measuring the phase offset, for example, the size of the data transmitted from the control device 1 to the UE 2 in S15 of Figure 2 can be reduced, thereby reducing overhead.

[0070] In the first embodiment, the control device 1 determines the number of subbands based on the coherent bandwidth of the received signal for measuring the phase offset of the received signal from the transmission point. However, the number of subbands determined based on the coherent bandwidth of the received signal is not limited to being used for measuring the phase offset. For example, the number of subbands determined based on the coherent bandwidth of the received signal from the transmission point can also be used to measure or acquire the amplitude of the received signal and frequency-selective information such as channel status information (CSI). Phase offset, amplitude of the received signal, and channel status information (CSI) are all examples of "information related to propagation characteristics".

[0071] In the first embodiment, the processing of the control device 1 may be performed by any of the base stations among the distributed stations, or by any of the relay stations if the signal to UE 2 is relayed by one or more relay stations. Also, if the signal to UE 2 is relayed by one or more relay stations, the relay station may perform the same processing on the transmission point as UE 2 in the first embodiment.

[0072] Furthermore, the processes and means described in this disclosure can be freely combined and implemented, provided that no technical inconsistencies arise.

[0073] Furthermore, a process described as being performed by a single device may be divided and executed by multiple devices. Conversely, a process described as being performed by different devices may be executed by a single device. In a computer system, the hardware configuration (server configuration) by which each function is implemented can be flexibly changed.

[0074] The present disclosure can also be realized by supplying a computer program implementing the functions described in the embodiments above to a computer, and having one or more processors in the computer read and execute the program. Such a computer program may be provided to the computer by a non-temporary computer-readable storage medium that can be connected to the computer's system bus, or it may be provided to the computer via a network. The non-temporary computer-readable storage medium includes any type of disk, such as magnetic disks (floppy disks, hard disk drives (HDDs), etc.), optical disks (CD-ROMs, DVDs, Blu-ray discs, etc.), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic cards, flash memory, or optical cards, and any type of medium suitable for storing electronic instructions.

[0075] 1...Control unit 2...UE 11...Control unit 100...Communication system 101...CPU 102...Main memory 103...External memory 104...Communication device

Claims

1. A method for a computer to perform the following: acquire the coherent bandwidth of a first signal received by a receiving device; and, based on the coherent bandwidth of the first signal, acquire the number of subbands in which the receiving device acquires information regarding the propagation characteristics of each of a plurality of subbands of the first signal.

2. The method according to claim 1, wherein the computer obtains the subband size based on the coherent bandwidth of the first signal, and obtains the number of subbands based on the channel bandwidth of the first signal and the subband size.

3. The method according to claim 2, wherein the computer selects the subband size from among 1, 2, 4, 8, and 16 physical resource blocks according to the coherent bandwidth of the first signal.

4. The method according to claim 1, wherein the computer further notifies the receiving device of an instruction to acquire information regarding the propagation characteristics of the first signal in each of the plurality of subbands, and the number of subbands.

5. The method according to claim 4, wherein the receiving device receives a plurality of received signals from a plurality of transmitting points, the information relating to the propagation characteristics is the phase offset of the first signal from a received signal from a reference transmitting point among the plurality of transmitting points, and the computer further performs the following: receiving from the receiving device the acquisition result of the information relating to the propagation characteristics of the first signal in each of the plurality of subbands; acquiring a phase correction value for the first signal based on the acquisition result; and causing the transmitting point of the first signal to transmit a signal using a carrier wave whose phase has been corrected based on the phase correction value.

6. An information processing device comprising: a control unit that performs the following: obtaining the coherent bandwidth of a first signal received by a receiving device; and obtaining the number of subbands in which the receiving device obtains information regarding the propagation characteristics in each of a plurality of subbands of the first signal, based on the coherent bandwidth of the first signal.

7. The information processing apparatus according to claim 6, wherein the control unit obtains the subband size based on the coherent bandwidth of the first signal, and obtains the number of subbands based on the channel bandwidth of the first signal and the subband size.

8. The information processing apparatus according to claim 7, wherein the control unit selects the subband size from among 1, 2, 4, 8, and 16 physical resource blocks according to the coherent bandwidth of the first signal.

9. The information processing apparatus according to claim 6, wherein the control unit further notifies the receiving device of an instruction to acquire information regarding the propagation characteristics of the first signal in each of the plurality of subbands, and the number of subbands.

10. The information processing apparatus according to claim 9, wherein the receiving device receives a plurality of received signals from a plurality of transmitting points, the information relating to the propagation characteristics is the phase offset of the first signal from a received signal from a reference transmitting point among the plurality of transmitting points, and the control unit further performs the following: receiving from the receiving device the acquisition result of the information relating to the propagation characteristics of the first signal in each of the plurality of subbands; acquiring a phase correction value for the first signal based on the acquisition result; and causing the transmitting point of the first signal to transmit a signal using a carrier wave whose phase has been corrected based on the phase correction value.

11. A program for causing a computer to perform the following actions: obtain the coherent bandwidth of a first signal received by a receiving device; and obtain the number of subbands in which the receiving device obtains information regarding the propagation characteristics of each of the multiple subbands of the first signal, based on the coherent bandwidth of the first signal.

12. The program according to claim 11, wherein the computer is instructed to obtain a subband size based on the coherent bandwidth of the first signal, and to obtain the number of subbands based on the channel bandwidth of the first signal and the subband size.

13. The program according to claim 12, wherein the computer selects the subband size from among 1, 2, 4, 8, and 16 physical resource block numbers according to the coherent bandwidth of the first signal.

14. The program according to claim 11, further causing the computer to notify the receiving device of an instruction to acquire information regarding the propagation characteristics of the first signal in each of the plurality of subbands, and the number of subbands.

15. The program according to claim 14, wherein the receiving device receives a plurality of received signals from a plurality of transmitting points, the information relating to the propagation characteristics is the phase offset of the first signal from a received signal from a reference transmitting point among the plurality of transmitting points, and the computer further causes the computer to: receive from the receiving device the acquisition result of the information relating to the propagation characteristics of the first signal in each of the plurality of subbands; acquire a phase correction value for the first signal based on the acquisition result; and transmit a signal to the transmitting point of the first signal using a carrier wave whose phase has been corrected based on the phase correction value.

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