Information processing device, information processing method, UE, and base station

Abstract

In order to suppress overhead due to time offset reporting, this information processing device, which controls CJT in a communication system including a UE having N second antenna ports that receive signals transmitted by the CJT from one or a plurality of base stations having K first antenna ports, supplies the UE with information indicating a reference signal that is used for measuring phase offset and time offset related to CJT and is periodically transmitted from one or more base stations to the UE, and information indicating a reporting condition used for controlling transmission of a time offset report, and updates the reporting condition on the basis of the time offset report transmitted, together with a phase offset report, from the UE on the basis of the information indicating the reporting condition.

Description

Information Processing Apparatus, Information Processing Method, UE, and Base Station

[0001] The present disclosure relates to an information processing apparatus, an information processing method, a UE, and a base station.

[0002] In wireless communication such as 5th Generation Mobile Communication System (5G), distributed MIMO (Multi-Input Multi-Output) has been 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 transmitted simultaneously from a plurality of distributed stations, the received signal power at the mobile station can be improved and the throughput can be increased. Also, in distributed MIMO, since the base stations are distributed, the dead zones of radio waves can be reduced and the influence of obstacles can be reduced.

[0003] In coordinated transmission between a plurality of distributed base stations (mTRP, hereinafter referred to as "distributed stations") such as distributed MIMO, a technique called Coherent Joint Transmission (CJT: coherent joint transmission) is used to improve the received signal power when signals from each distributed station are combined by receiving the transmission signals from each distributed station in the same phase at the UE (User Equipment). For example, in coordinated 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 CJT, 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 the network.

[0005] If a UE (Unified Electron) has multiple antenna ports, the UE is required to report the phase offset of the carrier wave from each antenna port at each distributed station to the network for each antenna port. Therefore, the phase offset reported from the UE to the network is the product of the number of antenna ports on the UE and the total number of antenna ports at the distributed stations. Consequently, as the number of antenna ports on the UE increases, the network overhead increases.

[0006] If a UE has multiple antenna ports, it is permitted to select one of these multiple antenna ports and report the phase offset of the carrier waves from the multiple antenna ports provided at each distributed station for the selected antenna port (for example, Non-Patent Document 1). The antenna port from which the phase offset is reported on behalf of the multiple antenna ports provided at the UE is referred to as the reference UE antenna port.

[0007] Furthermore, when performing CJT, a standardized method has been established for measuring the time offset using UE and reporting the measurement results (see, for example, Non-Patent Document 2).

[0008] Google, CSI Enhancement for NR MIMO, 3GPP TSG RAN WG1 #119, R1-2410154, November 18, 2024, pp.33GPP TS 38.214 version 18.2.0 Release 18

[0009] This disclosure aims to provide an information processing device, an information processing method, a user interface (UE), and a base station that can reduce the overhead caused by reporting time offsets.

[0010] One aspect of the present disclosure is a communication system comprising one or more base stations having K first antenna ports and a UE having N second antenna ports that receive signals transmitted from the one or more base stations by coherent joint transmission, wherein the information processing device controls the coherent joint transmission and includes a control unit that controls supplying the UE with information indicating a reference signal periodically transmitted from the one or more base stations to the UE and used for measuring phase offset and time offset related to the coherent joint transmission, and information indicating reporting conditions used for controlling the transmission of the time offset report, and updating the information indicating the reporting conditions based on the time offset report transmitted from the UE together with the phase offset report when the reporting conditions are met.

[0011] In addition to the information processing device described above, this disclosure may also include an information processing method, a computer program that causes a computer to operate as an information processing device, a computer-readable non-temporary recording medium that records the computer program, a UE, and a base station.

[0012] According to this disclosure, the overhead associated with reporting time offsets can be reduced.

[0013] Figure 1 shows an example of the configuration of a communication system. Figure 2 shows an example of the configuration of a control device. Figure 3 shows an example of the configuration of a UE. Figure 4 is a flowchart illustrating a first example of operation in the communication system (a control method for the first time offset report). Figure 5 is an explanatory diagram of the first reporting cycle setting method in the first time offset report control method. Figure 6 is an explanatory diagram of the second reporting cycle setting method in the first time offset report control method. Figure 7 is an explanatory diagram of the third reporting cycle setting method in the first time offset report control method. Figure 8 is a flowchart illustrating a second example of operation in the communication system (a control method for the second time offset report).

[0014] In implementing CJT, the UE measures and reports time offset and phase offset to the network. Time offset and phase offset have different "sensitivity." Regarding time offset, for example, if the channel bandwidth is 100 MHz (symbol period of 10 ns), compensation for time offset is necessary if a distance change of approximately 1 m or more occurs (propagation delay shift of 3 ns or more). Thus, time offset affects the channel bandwidth (subcarrier spacing). On the other hand, regarding phase offset, for example, if the carrier frequency is 4 GHz, compensation for phase offset is necessary to provide stable coherent synthesis if a distance change of 1 cm or less (20 ps) occurs. Thus, there is a difference of nearly 100 times in sensitivity between time offset and phase offset.

[0015] The time offset and phase offset are measured using the reference signal (CSI-RS) received by the UE. Therefore, the time offset and phase offset are measured using the same reference signal. However, if a time offset report is transmitted every time a phase offset report is transmitted, the difference in sensitivity causes a problem where the overhead increases due to the creation and transmission of the time offset report, even though the time offset report is essentially unnecessary. The following describes an information processing device and UE that control the reporting of the time offset in order to suppress overhead.

[0016] 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.

[0017] Figure 1 shows an example of the system configuration of the communication system 100. The communication system 100 includes a UE (User Equipment) 2, a control device 1, and a plurality of distributed base stations (distributed stations). The communication system 100 is, for example, a wireless communication system of 5G, LTE (Long Term Evolution), and mobile communication methods of 5G or later. The control device 1 is a device on the core network to which the distributed 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 stations and the UE 2.

[0018] A distributed station, along with other distributed stations within the same communication area, provides a wireless access network to UE2 located within that communication area. The three distributed stations (RU#1 to #3) shown in Figure 1 are assumed to be located within the same communication area. Each distributed station is connected to the control unit 1.

[0019] The distributed station is equipped with an antenna capable of forming multiple beam patterns. The antenna in the distributed station is, for example, an adaptive array antenna. An adaptive array antenna is an array antenna with multiple antenna elements arranged in a sequence. The adaptive array antenna can electrically form one or more beams and change their respective beam patterns by adaptively controlling each antenna element. The beams and beam patterns of the distributed station are controlled by the control device 1. The beams formed in the distributed station are identified by the antenna ports.

[0020] A base station comprises a Radio Unit (RU), a Distributed Unit (DU), and a Centralized Unit (CU). While a distributed station may also have an RU and a CU, the minimum configuration includes a DU, so hereafter, a distributed station will be referred to as a "DU." Hereafter, an antenna port provided on a DU will be referred to as a DU antenna port or a DU port. A DU antenna port is an example of a "first antenna port."

[0021] UE2 is a terminal station such as a smartphone, tablet, wearable device, or in-vehicle data communication device. UE2 may also be a vehicle. However, it is not limited to this, and UE2 may be a stationary terminal device such as an IoT device. Alternatively, a relay station that relays wireless communication between a distributed station and a terminal station can be used as a mobile station instead of UE2. Examples of relay stations include small base stations, mobile base stations, in-vehicle devices, and smartphones. In the first embodiment, UE2 is equipped with multiple antennas such as monopole antennas and dipole antennas, and these multiple antennas can form one or more beams. The beams formed in UE2 are identified by antenna ports. Hereinafter, antenna ports provided in UE2 will be referred to as UE antenna ports or UE ports. UE antenna ports are an example of a "second antenna port".

[0022] In the example shown in Figure 1, the communication system 100 includes three DUs: DU#1, DU#2, and DU#3. Each of DU#1, DU#2, and DU#3 is connected to and controlled by the control device 1. The connection between the control device 1 and each DU is, for example, via a dedicated line or a backbone network. The control device 1 and the UE2 communicate via a wireless communication control channel through either DU#1, DU#2, or DU#3.

[0023] DU#1, DU#2, and DU#3 perform CJT (Common-Mode Combined Coordinated Transmission) with UE2. For example, the three DUs, DU#1, DU#2, and DU#3, can perform CJT with UE2. Each of DU#1, DU#2, and DU#3 has two DU antenna ports. UE2 also has two UE antenna ports, UE#1 and UE#2.

[0024] DU#1, DU#2, and DU#3 are examples of "one or more base stations having K first antenna ports," where K is a natural number greater than or equal to 1. UE2 is an example of "a UE having N second antenna ports," where N is a natural number greater than or equal to 1. The CJT only needs to be able to receive signals transmitted from two or more first antenna ports at the second antenna ports of UE2. For simplicity, the following explanation assumes that UE2 receives signals from two base stations (DUs) via CJT at a single UE antenna port.

[0025] Figure 2 shows an example configuration of an information processing device operating as control device 1. The control device 1 (information processing device) comprises 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 be provided. Furthermore, the CPU 101 may work in conjunction with an integrated circuit such as a Field Programmable Gate Array (FPGA).

[0026] The CPU 101 operates as a control unit 1 by executing a computer program that has been loaded into the main memory 102 in an executable format. The main memory 102 stores the computer program executed by the CPU 101, data processed by the CPU 101, etc. The main memory 102 is a Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Read Only Memory (ROM), etc. Furthermore, the external storage device 103 is used as a storage area that assists the main memory 102, and stores the computer program executed by the CPU 101, data processed by the CPU 101, etc. The external storage device 103 is a hard disk drive, Solid State Drive (SSD), etc. Furthermore, a drive device for a removable storage medium may be connected to the control unit 1. Removable storage mediums are, for example, Blu-ray discs, Digital Versatile Discs (DVDs), Compact Discs (CDs), flash memory cards, etc. The CPU 101 is an example of a "control unit".

[0027] The communication device 104 communicates, for example, via optical fiber and with external networks such as the Internet. The communication device 104 of the control device 1 may be a single device or a combination of multiple devices. The control device 1 is an example of a "computer" and an "information processing device". Note that the configuration of the control device 1 is not limited to that illustrated in Figure 2.

[0028] Figure 3 shows an example configuration of UE2. UE2 comprises a CPU 201, main memory 202, external storage 203, wireless communication device 204, and antenna 205 as its hardware configuration. The CPU 201, main memory 202, and external storage 203 are the same as those of CPU 101, main memory 102, and external storage 103.

[0029] The wireless communication device 204 is connected to the antenna 205 and, through the antenna 205, connects to a wireless access network, for example, by a 5G or later mobile wireless communication system, and receives wireless signals from distributed base stations. The wireless communication device 204 is also connected to the control device 1 on the control plane. The configuration of the UE2 is not limited to that illustrated in Figure 3. Depending on the type, the UE2 may further include input devices (touch panel display, buttons, keys, etc.), a display, a microphone, and a speaker in addition to the components shown in Figure 3.

[0030] <First Operation Example> Figure 4 is a flowchart illustrating the first operation example (first time offset reporting control method) in a communication system. The network (NW) shown in Figure 4 represents the control device 1 that controls CJT, the distributed stations represent the multiple DUs shown in Figure 1, and the UE represents the UE2 shown in Figure 1. For the sake of simplicity, we will assume that CJT is performed using two distributed stations (two first antenna ports) and one second antenna port of the UE.

[0031] The network (NW) allocates a resource block for transmitting the downlink reference signal (CSI-RS) at the period required for measuring the phase offset, based on the period of the downlink reference signal (CSI-RS) (step S1). The allocation result is notified to the distributed stations and UEs (steps S2 and S3). The network also calculates an initial value for the time offset reporting period (timing for transmitting time offset reports) (e.g., reporting each time the phase offset is measured and reported) and notifies the UEs via the distributed stations (steps S2 and S3). The initial value may be transmitted together with the allocation result or separately. The time offset reporting period (timing for transmitting time offset reports) is an example of "control information".

[0032] Each distributed station transmits a reference signal using the resource block allocated to it from the network (step S4). Downlink communication via CJT is performed after the reference signal is transmitted. The reference signal is received by the UE (step S5), and the UE uses the reference signal to calculate (measure) the phase offset and time offset.

[0033] The UE refers to the initial value of the time offset reporting cycle (however, if an updated reporting cycle has been notified, the updated reporting cycle) and determines whether to report the time offset along with the phase offset (step S7). If it is determined that the time offset should be reported along with the phase offset, the UE generates a phase offset report and a time offset report containing the calculation results of the phase offset and time offset, and sends them to the NW (step S8). The phase offset report and the time offset report may be sent in a single message or in separate messages.

[0034] The network (NW) uses the time offset report to update the time offset report cycle (step S9). However, the cycle length may be the same before and after the update. If the time offset report cycle changes due to the update, the NW sends a notification (instruction) regarding the timing of sending the time offset report related to the update, as needed.

[0035] If it is determined that neither the phase offset nor the time offset needs to be reported, the UE generates a phase offset report and transmits it to the NW (step S11). In this case, the time offset report is not transmitted. Note that the phase offset report and the time offset report may be transmitted at different timings for each distributed station. Thereafter, steps S5 to S11 are repeated each time a reference signal is transmitted.

[0036] <First Time Offset Report Control Method: First Control Method> In step S9, the NW updates the time offset report cycle using the following method. (Method for setting the first report cycle (transmission timing)) Figure 5 is an explanatory diagram of the first report cycle setting method in the first time offset report control method. In step S9, the NW updates (sets) the time offset report cycle using the following method.

[0037] In the first method for setting the reporting cycle, general linear interpolation is performed. Specifically, the network (NW) sets the initial time offset to zero. The initial value of the time offset reporting cycle is the same as the phase offset reporting timing (reporting cycle = 1). Then, based on the results of two or more offset reports, the NW sets the time offset reporting cycle (transmission timing) taking into account the allowable value of the time offset and the safety factor (margin).

[0038] In the graph shown in Figure 5, the vertical axis represents the time offset (absolute value), and the horizontal axis represents time. The numbers 0 to 8, indicating time, represent the transmission timing of the phase offset report. The dashed line in the graph is a line drawn considering the tolerance and safety factor (upper limit of the time offset). At transmission timing "1", the time offset report is transmitted from the UE according to the initial value "1" of the reporting cycle. The NW draws a straight line that passes through the time offset value of transmission timing "0" (initial value: zero) and the time offset value of transmission timing "1". This straight line exceeds the upper limit between the 4th and 5th transmissions. In this case, the NW sends an instruction to the UE to transmit the time offset report at transmission timing "4". For example, the NW updates the time offset reporting cycle to "3" and notifies the UE of the updated reporting cycle "3". As a result, the transmission of time offset reports at transmission timings "2" and "3" is omitted (it is determined that transmission is unnecessary). Here, the report cycle, whose value has changed due to the update, is sent to the UE. However, the instruction content (control information) only needs to indicate the timing for sending the next time offset report, and may include information other than the report cycle. Also, if the updated report cycle is the same as the previous report cycle, the transmission of the updated report cycle may be omitted.

[0039] Furthermore, if the network receives a time offset report from the user audience (UE) at transmission timing "4", it draws an approximation line (straight line) for the time offset plots at transmission timings "0", "1", and "4". In this case, the straight line exceeds its upper limit around transmission timing "7". Therefore, the network decides to send the time offset report at the preceding transmission timing "6", updates the reporting cycle to "2", and notifies the UE. In other words, the network instructs the UE to send the time offset report at transmission timing "6". As a result, the transmission of the time offset report at transmission timing "5" is omitted.

[0040] Furthermore, when the network receives a time offset report at transmission timing "6", it draws an approximation line (straight line) for the plotted time offsets at transmission timings "0", "1", "4", and "6". This straight line exceeds its upper limit between transmission timings "8" and "9". Therefore, the network decides to transmit the time offset report at transmission timing "8", just before the straight line exceeds its upper limit, updates the reporting cycle to "2", and notifies the user interface (UE). In this way, the network instructs the user interface to transmit the time offset report at transmission timing "8". As a result, the time offset report at transmission timing "7" becomes unnecessary and is omitted. Note that even if the network updates the reporting cycle, if the value is the same as the previous value, a configuration may be adopted in which the network does not transmit the updated reporting cycle or instructions (control information) to the user interface.

[0041] NW may set (update) the initial value of the reporting period to "8" for the transmission of time offset reports after transmission timing "8", so that a time offset report is transmitted for every eight phase offset report transmission timings. However, the period may be set to a value obtained by multiplying the 8 obtained above by a coefficient of 1 or less, or to a number obtained by subtracting 1 from 8.

[0042] According to the first reporting period setting method, in the example of FIG. 5, at the transmission timings of the second, third, fifth, and seventh phase offset reports, the transmission of the time offset report is not performed. Thereby, overhead can be suppressed.

[0043] (Second Reporting Period Setting Method) FIG. 6 is an explanatory diagram of the second reporting period setting method in the first control method. In the second reporting period setting method, the reporting period (transmission timing) of the time offset is set (updated) using the maximum change amount within a predetermined time window. When NW receives the current time offset report (time offset), it calculates the change amount (difference) from the time offset (zero) at the previous transmission timing, and sets the reporting period of the time offset in consideration of the allowable value of the time offset and the safety factor (margin).

[0044] In the example shown in FIG. 6, similar to the first reporting period setting method, the initial value of the time offset is zero, and the initial value of the reporting period is the same period as the reporting period of the phase offset. From these initial settings, a time offset report is sent from the UE to the NW at transmission timing "1". NW obtains a straight line (slope a_0,1) passing through the time offset (initial value = 0) at transmission timing "0" and the value of the time offset at "1". In this specification, a subscript (for example, A ｘ ) is denoted as "A_x". The straight line with slope a_0,1 exceeds the upper limit between transmission timings "5" and "6". Therefore, NW sets the transmission timing (reporting timing) of the time offset report based on the straight line with slope a_0,1 to "5", and sets (updates) "4", which is 1 subtracted from "5", as the reporting period of the time offset. Thereby, NW instructs the UE to transmit a time offset report at reporting timing "5" (sends the reporting period "4" to the UE as control information). From this, in the UE, the transmission of the time offset report at transmission timings "2" and "3" is omitted.

[0045] Next, when the NW receives the time offset report sent from the UE at reporting timing "5", it sets the time offset at reporting timing "5" to the initial value (zero). Also, the NW acquires the time offset at the next reporting timing "9" according to the reporting period "4", and draws a straight line (slope a_5,9) connecting the values of the time offsets at reporting timings "5" and "9" respectively. The NW compares slope a_0,1 and slope a_5,9. In the example of FIG. 6, since slope a_5,9 is larger than slope a_0,1, the reporting period is updated to "3". This is because it is considered that the upper limit is reached in a shorter time as the slope is larger. If slope a_5,9 is less than or equal to slope a_0,1, the reporting period "4" is maintained. The example shown in FIG. 6 is an example showing one time window. The length of the time window can be appropriately set based on the passage of time, or the number of offset compensations, or the number of transmission timings, etc.

[0046] (Third Reporting Period Setting Method) FIG. 7 is an explanatory diagram of the third reporting period setting method in the first control method. The NW can obtain indicators related to propagation characteristics such as L1-RSRP (Layer 1 - Reference Signal Received Power), L1-SINR (Layer 1 - Signal to Interference plus Noise Ratio), and RI for the reference signals transmitted from each distributed station from the UE. The NW uses the indicator to calculate the gain of the signal synthesized by the UE from the signals received from each distributed station by CJT, and updates the reporting period of the time offset in consideration of the allowable value of the gain.

[0047] In FIG. 7, the vertical axis of the graph is the CJT combined gain indicating the gain of the signal synthesized by CJT for the received signals, the horizontal axis is time, and 0 to 9 indicate the transmission timings of the phase offset report. The initial value of the CJT combined gain is set to a predetermined ideal value. Also, the initial value of the reporting period is the same as the transmission period of the phase offset report.

[0048] In Figure 7, the UE transmits a time offset report and an indicator for calculating the CJT composite gain (referred to as CJT composite gain calculation information) to the NW at transmission timing "1", according to the initial value "1" of the reporting cycle. The NW calculates the CJT composite gain using the CJT composite gain calculation information. However, instead of the CJT composite gain calculation information, information indicating the calculation result of the CJT composite gain calculated by the UE may be sent to the NW. The NW draws a straight line passing through the CJT composite gain values ​​at transmission timings "0" and "1", and identifies the intersection point of this line with the dashed line indicating the allowable value (lower limit) of the CJT composite gain shown in the graph of Figure 7. Since the intersection point is between transmission timings "3" and "4", transmission timing "3" is determined as the transmission timing for the next time offset report (the reporting cycle is updated to "2", and the updated reporting cycle is notified to the UE). This eliminates the need for the UE to send a time offset report at transmission timing "2".

[0049] Next, the network receives the time offset report and CJT composite gain calculation information transmitted from the UE at transmission timing "3". The network draws a line connecting the initial value of the CJT composite gain and the CJT composite gain at transmission timing "3" (calculated from the CJT composite gain calculation information), and identifies the intersection point of this line with the dashed line of the allowable value (lower limit). Since the intersection point lies between transmission timings "5" and "6", transmission timing "5" is determined as the transmission timing for the next time offset report (the reporting cycle is updated to "2", and the updated reporting cycle is notified to the UE. However, notification is optional). As a result, the transmission of the time offset report at transmission timing "4" by the UE is omitted (becomes unnecessary).

[0050] Next, the network receives the time offset report and CJT composite gain calculation information transmitted from the UE at transmission timing "5". The network draws a line connecting the initial value of the CJT composite gain and the CJT composite gain at transmission timing "5" (calculated from the CJT composite gain calculation information), and identifies the intersection point of this line with the dashed line of the allowable value (lower limit). Since the intersection point lies between transmission timings "7" and "8", transmission timing "7" is determined as the transmission timing for the next time offset report (the reporting cycle is updated to "2", and the updated reporting cycle is notified to the UE. However, notification is optional). As a result, the transmission of the time offset report at transmission timing "6" by the UE is omitted (becomes unnecessary).

[0051] Based on the results so far, NW may set (update) the initial value of the time offset reporting cycle to "7". However, the reporting cycle may also be set to a value obtained by multiplying 7 by a count of 1 or less, or to a value obtained by subtracting 1 from 7.

[0052] (Fourth method for setting the reporting period) As a fourth method for setting the reporting period in the first control method, the reporting period of the time offset may be updated based on physical information of the UE (at least one of the UE's direction of movement, speed of movement, and position). For example, machine learning is performed on the relationship between past CJT composite gain or measured data of the time offset amount and physical information to generate a discriminator that calculates the reporting period from at least one of the UE's position, direction of movement, and speed of movement. The NW can then determine the reporting period using this discriminator.

[0053] <Second Operation Example> Figure 8 is a flowchart illustrating a second operation example (second time offset reporting control method) in the communication system. The difference from the flowchart in Figure 4 is that steps S21, S27, S29, and S30 are provided instead of steps S1, S7, S9, and S10.

[0054] In step S21, NW calculates initial values ​​for the time offset reporting conditions instead of initial values ​​for the time offset reporting cycle and supplies them to UE (steps S2 and S3 in Figure 8). The processing in steps S4 to S6 in Figure 8 is the same as in Figure 4. In step S27, UE determines whether the time offset reporting conditions are met. If it is determined that the reporting conditions are met, UE sends a phase offset report and a time offset report (step S8); otherwise, UE sends a phase offset report (step S11).

[0055] The reporting conditions for time offset are an example of "control information." The initial value of the reporting conditions can be, for example, a time offset threshold that takes into account the allowable value of the time offset and the safety factor (margin). However, it is not limited to this. In step S27, the UE can determine that it will send a time offset report if the calculation result of the time offset exceeds this threshold.

[0056] Furthermore, the NW may provide the UE with a threshold value for the CJT combined gain as an initial value for the reporting conditions. The UE has a configuration that allows it to calculate the CJT combined gain from the L1-RSRP of the reference signal from each distributed station, and in step S27, it may determine to transmit a time offset report if the CJT combined gain exceeds the threshold value.

[0057] Furthermore, as a reporting condition for the time offset, the UE may be provided with information indicating the physical information of the UE (at least one of its position, direction of movement, and speed of movement). The UE can calculate its position, direction of movement, and speed of movement using a GPS receiver or the like installed on its aircraft. In step S27, if the UE's position, direction of movement, and speed of movement match the position, direction of movement, and speed of movement indicated as reporting conditions, it may be determined to transmit the time offset report.

[0058] The information indicating the position, direction of movement, and speed of the UE provided as reporting conditions may be obtained by learning the correspondence between the position, direction of movement, and speed of the UE and the measured data of the time offset and CJT composite gain.

[0059] In step S29, if the reporting cycle needs to be shortened or lengthened based on the time offset indicated in the time offset report, the reporting conditions are updated, and the updated reporting conditions are provided to the UE as necessary (step S30). For example, if the reporting conditions are changed due to the update of the reporting conditions, the updated conditions are provided to the UE; otherwise (if the reporting conditions are maintained), the updated conditions are not provided to the UE.

[0060] According to the control device 1 (corresponding to the NW: information processing device) of this embodiment, by controlling the reporting cycle of the time offset (the timing of sending the time offset report) through the first control method, it is possible to reduce the frequency of time offset reports being sent and suppress overhead. Furthermore, the UE sends a time offset report when the reporting conditions are met, and does not send a time offset report otherwise, using the second control method. This also suppresses overhead.

[0061] The control device 1 (information processing device) according to this embodiment controls CJT in a communication system including one or more base stations (distributed stations) having K first antenna ports and a UE having N second antenna ports that receive signals transmitted from one or more base stations by coherent joint transmission (CJT). The control device 1 supplies the UE with information indicating a reference signal (CSI-RS) that is periodically transmitted from one or more base stations to the UE and used for measuring phase offset and time offset related to CJT transmission, and control information used for controlling the transmission of time offset reports. The control device 1 also updates the control information based on time offset reports transmitted from the UE along with phase offset reports transmitted based on the control information. The control information is, for example, information indicating the reporting period of time offsets. According to the control device 1, by supplying control information to the UE, the transmission timing of time offsets can be controlled, and the frequency of time offset reports can be set to a preferred frequency that is less frequent than that of phase offset reports. This reduces the overhead of the UE.

[0062] In this embodiment, the UE receives from the second antenna port described above and from the control device 1 that controls CJT transmission information indicating a reference signal that is periodically transmitted from one or more base stations to the UE2 and used for measuring phase offset and time offset related to CJT transmission, and information indicating time offset reporting conditions used for controlling the transmission of time offset reports. The UE includes a control unit (CPU 201) that, when the reporting conditions are met, transmits a phase offset report along with a time offset report used for updating the reporting conditions.

[0063] The information indicating the reporting conditions is information indicating a time offset threshold, and the CPU 201 (control unit) can decide to send a time offset report if the time offset measured in UE2 exceeds that threshold.

[0064] Furthermore, the information indicating the reporting conditions is information indicating the threshold of the CJT combined gain, and the CPU 201 (control unit) can decide to send a time offset report if the gain of the signal obtained by combining the received signals from one or more base stations transmitted by CJT (CJT combined gain) exceeds the threshold.

[0065] Furthermore, the information indicating the reporting conditions is information indicating at least one of the position, direction of movement, and speed of movement, and the CPU 201 (control unit) can decide to send a time offset report if at least one of the position, direction of movement, and speed of the UE matches at least one of the position, direction of movement, and speed of movement indicating the reporting conditions.

[0066] A time offset report is sent only when the reporting conditions are met; otherwise, it is not sent. This reduces the frequency of time offset reports and thus lowers the overhead of the UE. The information indicating the reporting conditions is updated so that the reporting frequency increases when the UE is moving (changing location) rapidly, and decreases when the UE is moving (changing location) slowly.

[0067] The communication system according to the embodiment includes a base station (distributed station, DU) having at least one antenna port for transmitting signals for CJT to the UE. The base station has at least the configuration shown in Figure 3 and a communication interface (communication device) connected to the core network. The base station (its control unit (CPU 201)) can transmit to the UE a reference signal used for measuring phase offset and time offset related to CJT, and information indicating the reporting conditions for the time offset used for controlling the transmission of the time offset report. The control unit (CPU 201) of the base station can also relay the time offset report transmitted from the UE along with the phase offset report when the reporting conditions are met to an information processing device (control device 1) that controls CJT for updating the reporting conditions.

[0068] A process described as being performed by one device in an embodiment may be divided and executed by multiple devices. Alternatively, 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.

[0069] 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.

[0070] 1...Control device 2...UE 100...Communication system 101,201...CPU 102,202...Main memory 103,203...External memory 104...Communication device 204...Wireless communication device

Claims

1. A communication system comprising one or more base stations having K first antenna ports and a UE having N second antenna ports that receive signals transmitted from the one or more base stations by coherent joint transmission, wherein the information processing device controls the coherent joint transmission and includes a control unit that controls: supplying the UE with information indicating a reference signal periodically transmitted from the one or more base stations to the UE and used for measuring phase offset and time offset related to the coherent joint transmission, and information indicating reporting conditions used for controlling the transmission of the time offset report; and updating the information indicating the reporting conditions based on the time offset report transmitted from the UE together with the phase offset report when the reporting conditions are met.

2. The information processing device according to claim 1, wherein the information indicating the reporting conditions is information indicating a threshold, and the transmission of the time offset report is determined when the time offset measured in the UE exceeds the threshold.

3. The information processing device according to claim 1, wherein the information indicating the reporting conditions is information indicating a threshold, and the transmission of the time offset report is determined when the gain of the signal obtained by synthesizing the received signals from the one or more base stations transmitted by the coherent joint transmission exceeds the threshold.

4. The information processing apparatus according to claim 1, wherein the information indicating the reporting conditions is information indicating at least one of position, direction of movement, and speed of movement, and the transmission of the time offset report is determined when at least one of the position, direction of movement, and speed of movement of the UE matches at least one of the position, direction of movement, and speed of movement indicating the reporting conditions.

5. A communication system comprising one or more base stations having K first antenna ports and a UE having N second antenna ports that receive signals transmitted from the one or more base stations by coherent joint transmission, wherein an information processing device that controls the coherent joint transmission supplies the UE with information indicating a reference signal periodically transmitted from the one or more base stations to the UE and used for measuring phase offset and time offset related to the coherent joint transmission, and information indicating reporting conditions used for controlling the transmission of the time offset report, and updates the information indicating the reporting conditions based on the time offset report transmitted from the UE together with the phase offset report when the reporting conditions are met.

6. The information processing method according to claim 5, wherein the information indicating the reporting conditions is information indicating a threshold, and the transmission of the time offset report is determined when the time offset measured in the UE exceeds the threshold.

7. The information processing method according to claim 5, wherein the information indicating the reporting conditions is information indicating a threshold, and the transmission of the time offset report is determined when the gain of the signal obtained by synthesizing the received signals from the one or more base stations transmitted by the coherent joint transmission exceeds the threshold.

8. The information processing method according to claim 5, wherein the information indicating the reporting conditions is information indicating at least one of position, direction of movement, and speed of movement, and the transmission of the time offset report is determined when at least one of the position, direction of movement, and speed of movement of the UE matches at least one of the position, direction of movement, and speed of movement indicating the reporting conditions.

9. A UE comprising: N second antenna ports that receive signals transmitted by coherent joint transmission from one or more base stations having K first antenna ports; a control unit that performs the following from an information processing device that controls the coherent joint transmission: information indicating a reference signal periodically transmitted from the one or more base stations and used for measuring phase offset and time offset related to the coherent joint transmission, and information indicating the time offset reporting conditions used for controlling the transmission of the time offset report; and, when the reporting conditions are met, transmit the time offset report used for updating the reporting conditions along with the phase offset report; 10. The UE according to claim 9, wherein the information indicating the reporting conditions is information indicating a threshold, and the control unit decides to transmit the report of the time offset when the time offset measured in the UE exceeds the threshold.

11. The UE according to claim 9, wherein the information indicating the reporting conditions is information indicating a threshold, and the control unit decides to transmit the time offset report when the gain of the signal obtained by synthesizing the received signals from the one or more base stations transmitted by the coherent joint transmission exceeds the threshold.

12. The UE according to claim 9, wherein the information indicating the reporting conditions is information indicating at least one of position, direction of movement, and speed of movement, and the control unit decides to transmit the time offset report when at least one of the position, direction of movement, and speed of the UE matches at least one of the position, direction of movement, and speed of movement indicating the reporting conditions.

13. A base station having at least one antenna port for transmitting signals for coherent joint transmission to a UE, the base station including a control unit that controls: transmitting to the UE a reference signal used for measuring phase offset and time offset related to the coherent joint transmission, and information indicating the time offset reporting conditions used for controlling the transmission of the time offset report; and relaying the time offset report transmitted from the UE together with the phase offset report when the reporting conditions are met to an information processing device that controls the coherent joint transmission for updating the reporting conditions.

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