Control device, control method, and program for controlling access point cluster
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-08-13
Smart Images
Figure JP2025045054_13082026_PF_FP_ABST
Abstract
Description
Control Device, Control Method, and Program for Controlling an Access Point Cluster
[0001] The present invention relates to a technique for selecting an access point cluster in a mobile communication system.
[0002] Self-free is being considered as an enabling technology for the next-generation cellular communication standard in the 3rd Generation Partnership Project (3GPP (registered trademark)). Self-free is a technology that uses antennas distributed at multiple locations in cooperation, and it is expected to improve the performance degradation caused by inter-cell interference that occurred in the conventional method.
[0003] In self-free, a signal processing device or a control device on the network side communicates with a terminal using each of the antennas distributed at multiple locations. Therefore, the processing load of the signal processing device or the control device may increase. In contrast, in order to reduce the processing load of the signal processing device or the control device, AP clustering that restricts the antennas to be used for each terminal among the antennas distributed at multiple locations has been considered. AP is an abbreviation for access point. In Patent Document 1, when a message signal for connection establishment transmitted from a terminal is received at each of the antennas distributed at multiple locations, a technique for selecting the antennas constituting an AP cluster using the received power of the message signal at each antenna is described.
[0004] Japanese Patent Application Laid-Open No. 2021-78043
[0005] The present invention provides a technique for improving the radio quality provided to a terminal while reducing the processing load of a signal processing device or a control device in a mobile communication system using self-free.
[0006] A control device according to one aspect of the present invention is a control device connected to a plurality of antennas and using at least one of the plurality of antennas to communicate user data with a terminal device, comprising: acquisition means for acquiring a message signal for establishing a connection with the control device transmitted by the terminal device via a first set of antennas included in the plurality of antennas, and acquiring a reference signal for measuring radio quality transmitted by the terminal device via each of the plurality of antennas; and control means for controlling the communication of user data with the terminal device using a second set of antennas selected based on the message signal or the reference signal, wherein when the message signal is acquired via the first set of antennas... In the event that the received power of the message signal is measured at each of the antennas included in the first set of antennas, one or more antennas included in the first set of antennas selected based on the results of the measurement, and antennas included in the plurality of antennas but not included in the first set of antennas selected according to predetermined criteria, are selected as the second set of antennas, and after the second set of antennas has been selected, if the reference signal is acquired through each of the plurality of antennas, the received power of the reference signal is measured at each of the plurality of antennas, and the second set of antennas is updated with the antenna selected from the plurality of antennas based on the results of the measurement.
[0007] According to the present invention, in a mobile communication system using cell-free technology, it is possible to improve the wireless quality provided to the terminal while reducing the processing load on the signal processing device and control device.
[0008] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are given the same reference numeral.
[0009] The attached drawings are included in the specification and constitute part thereof, illustrating embodiments of the present disclosure and used together with the description to explain the principles of the present disclosure. Figure 1 is a diagram showing an example configuration of a mobile communication system. Figure 2 is a diagram showing an example processing flow executed by a control device. Figure 3 is a diagram showing an example hardware configuration of a control device. Figure 4 is a diagram showing an example functional configuration of a control device. Figure 5 is a diagram showing an example sequence of messages exchanged between a control device and an AP. Figure 6 is a diagram showing an example sequence of messages exchanged between a control device and an AP.
[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.
[0011] (System Configuration) Figure 1 shows an example of the configuration of a mobile communication system according to this embodiment. The mobile communication system of this embodiment is, for example, a cellular communication system compliant with the cellular communication standard of the Third Generation Partnership Project (3GPP®). The cellular communication standard may be Long Term Evolution (LTE), Fifth Generation Mobile Communication System (5G), Beyond 5G, 6G, etc. However, it is not limited to these, and the following discussion can be applied to a mobile communication system compliant with any wireless communication standard. This mobile communication system is composed of, for example, control devices 101 to 102, APs 111 to 119, terminal 121, and RIC 131. AP is an abbreviation for access point. Access points are sometimes called antennas. RIC is an abbreviation for Radio Intelligent Controller. Control device 101 is connected by APs 111 to 115. Furthermore, the control device 102 is connected by APs 116 to 119. The RIC 131 is connected by control devices 101 and 102. Control devices 101 and 102 are sometimes referred to as control device 100 without distinction. Also, APs 111 to 119 are sometimes referred to as AP 110 without distinction. The control device 100 and AP 110 may be connected by a network including a wired network using optical fiber or the like, or a wireless network. Also, the control device 100 and RIC 131 may be connected by a network including a wired network using optical fiber or the like, or a wireless network. The control device 100 is connected to a core network (not shown). The core network may be, for example, an Evolved Packet System (EPS) or a 5G Core Network (5GC). In this embodiment, the communication device to which each of AP 110 is connected is described as the control device 100, but the control device 100 may be a signal processing device.
[0012] Terminal 121 can wirelessly connect to the control device 100 via at least one of APs 111 to 119, and connect to the core network via the control device 100. Terminal 121 may be called User Equipment (UE). Terminal 121 includes, for example, smartphones, mobile phones, personal computers, tablet terminals, wearable devices, IoT (Internet of Things) terminals, etc. For example, terminal 121 can communicate with the core network via one or more APs 110 connected to one control device 100. In this case, the control device 100 performs signal synthesis processing, etc., of the signals received at each AP 110, and receives processing is performed using the synthesized signals. The control device 100 can perform signal synthesis processing of the signals received at each AP 110 by, for example, maximum ratio synthesis based on the received power of the signals received at each AP 110. Terminal 121 can also communicate with the core network via multiple control devices 100. For example, terminal 121 can communicate with the core network via one or more APs 110 connected to each of the multiple control devices 100. In this case, signals received by each AP 110 are acquired by the control devices 100 connected to each AP 110. Then, synthesis processing, reception processing, etc., can be performed in cooperation with these control devices. The received signals acquired by each control device may be aggregated into one control device, and synthesis processing and reception processing may be performed by that one control device. Alternatively, each control device may perform synthesis processing of the signals it has acquired, the synthesized signals may be aggregated into one control device, and further synthesis processing may be performed in that one control device before reception processing is performed. In this way, in Selfree, a virtual area centered on terminal 121 can be configured for one terminal 121 by one or more APs 110 connected to one or more control devices 100. By configuring a virtual area centered on terminal 121, high-quality and stable communication services can be provided to terminal 121 regardless of its geographical location.
[0013] The control device 100 communicates wirelessly with the terminal 121 via one or more APs 110 connected to itself. The control device 100 may have at least some of the functions that a base station in a mobile communication system should have. For example, if the APs 110 function as antennas that transmit and receive radio signals, the control device 100 may acquire analog radio frequency (RF) signals from the APs 110. In this case, the control device 100 may have functions for filtering the acquired signals, frequency conversion, analog / digital (A / D) conversion, baseband processing, combining the signals acquired from each AP 110, and subsequent reception processing. On the other hand, the APs 110 may have functions for filtering the received radio signals, frequency conversion, analog / digital (A / D) conversion, and baseband processing. In this case, the control device 100 may have functions for combining the signals acquired from each AP 110 and performing subsequent reception processing using the combined signals. The arrangement of functions between the AP 110 and the control device 100 is not limited to these and may be determined based on the design policy of the mobile communication system. When one terminal 121 communicates via one or more APs 110 connected to each of the multiple control devices 100, the signals received by all APs 110 are transferred to one of the multiple control devices 100, and synthesis processing or the like is performed in that one control device 100. Alternatively, the results of predetermined processing performed in each of the multiple control devices 100 may be transferred to one device, where subsequent processing is performed. For example, the results of a first synthesis process performed in each control device 100 may be transferred to any of the control devices 100 or other devices. Then, a second synthesis process may be performed using the results of this first synthesis process and the results of the first synthesis process performed in any of the control devices 100 or other devices. Then, reception processing using the results of the second synthesis process may be performed in any of the control devices 100 or other devices. The control device 100 may also be a device that operates as a DU (Distributed Unit) in the Open-Radio Access Network (O-RAN).In this case, the control device 100 can execute processes that are not executed by AP 110 among the processes executed in layers below the MAC layer, and output the results to the CU (Central Unit). The CU can execute processes in layers higher than the MAC layer. The CU can be connected by multiple DUs. For example, if each of the multiple control devices 100 operates as a DU, the output of each control device 100 can be directed to a single communication device operating as a CU.
[0014] RIC 131 controls the radio access network in a mobile communication system for intelligent operation. For example, RIC 131 can be a Non-RealTime RAN Intelligent Controller (non-real-time RIC) or a Near-RealTime RIC (near-real-time RIC) in an O-RAN. Non-real-time RICs make decisions on policies to control the long-term behavior of the radio access network. Near-real-time RICs control the short-term behavior of the radio access network. For example, RIC 131 can issue instructions to the control devices 100 and AP 110 based on information about the radio environment provided by each of the control devices 100. Communication between RIC 131 and the control devices 100 can be performed using E2AP or O1AP. E2AP is an abbreviation for E2 Application Protocol, and O1AP is an abbreviation for O1 Application Protocol.
[0015] As shown in Figure 1, in this embodiment, the wireless communication system has a large number of APs 110 arranged at high geographical density, and the control device 100 acquires signals received by the APs 110 connected to itself. Each control device 100 combines the acquired signals and performs reception processing. With this configuration, the processing load on the control device 100 increases as the number of APs 110 connected to a single control device 100 increases. For example, control device 101 acquires signals received from terminal 121 by each of APs 111 to 115. Also, control device 102 acquires signals received from terminal 121 by each of APs 116 to 119. For example, each control device 100 can perform combining processing and reception processing of the received signals acquired from each of the APs 110 connected to itself. Alternatively, the signals acquired from each of APs 111 to 119 can be aggregated in a single communication device including any of these control devices, and combining processing and reception processing can be performed. Thus, as the number of APs 110 increases, the processing load on the control device 100 that performs combining processing and reception processing can increase. To reduce the processing load on such a control device 100, AP clustering can be applied, which selects a set of APs 110 to be used for each terminal. By selecting an appropriate set of APs 110 for each terminal using the mobile communication system, it is possible to reduce the processing load on the control device 100 while maintaining the radio quality provided to that terminal. For example, the AP cluster, which is a set of APs 110, can be selected based on the radio quality provided to terminal 121. As an example, when terminal 121 connects to the mobile communication system, it periodically transmits a reference signal to measure the radio quality. For example, the reference signal may be called a Sounding Reference Signal (SRS). The reference signal transmitted by terminal 121 is received by each AP 110 and used to measure the radio quality. For example, the control device 100 can acquire the reference signal from each AP 110 and measure the received power at each AP 110. The received power may be called Reference Signal Received Power (RSRP). The value indicating the received power is not limited to RSRP, but may also be RSRQ, RSSI, SINR, etc.RSRQ is an abbreviation for Reference Signal Received Quality. RSSI is an abbreviation for Received Signal Strength Indicator. SINR is an abbreviation for Signal to Interference plus Noise Ratio. The received power measured in the control device 100 may be notified to the RIC 131. Based on the received power collected from each control device 100, the RIC 131 may determine the AP cluster for terminal 121. For example, the RIC 131 may select a predetermined number of APs 110 as the AP cluster for terminal 121, starting with the APs 110 with the highest received power of the reference signal transmitted by terminal 121. Furthermore, RIC 131 may select AP 110s whose received power of the reference signal transmitted by terminal 121 exceeds a predetermined threshold as an AP cluster for terminal 121. Also, RIC 110 may select a combination of AP 110s whose total received power of the reference signal transmitted by terminal 121 exceeds a predetermined threshold as an AP cluster for terminal 121. Note that the AP 110s selected by RIC 110 may be connected to one control device 100, or some may be connected to different control devices 100. The AP cluster selected for terminal 121 in this way is used for communication of terminal 121.
[0016] Here, until the AP cluster for terminal 121 is determined, it is not clear which AP 110 is suitable for communication with terminal 121, so all AP 110 can be used for communication with terminal 121. For example, terminal 121 performs a random access procedure to establish a connection to the network. As an example, terminal 121 starts a random access procedure using the radio resource (RACH) allocated for sending message signals for the random access procedure. RACH is an abbreviation for Random Access Channel. At the stage when terminal 121 performs the random access procedure, the establishment of terminal 121's connection to the network is not yet complete, so an AP cluster for terminal 121 has not been selected. In this case, the control device 100 can use all AP 110 to perform a random access procedure with terminal 121. For example, signals received in the RACH via each of AP 111 to AP 119 are output to the control device 100, and each control device 100 processes the signals received via the AP 110 connected to its own device. Furthermore, since the timing for initiating the random access procedure is determined by terminal 121, the control device 100 constantly monitors the RACH output from each AP 110 and synthesizes the RACHs obtained from each AP 110 to detect whether or not a transmission has been made from terminal 121. Thus, even when AP clustering is applied, there are factors that increase the processing load of the control processing 100, such as the processing for the random access procedure with terminal 121 in the control device 100.
[0017] To reduce the processing load on the control device 100 related to such random access procedures, the APs 110 used for the random access procedure are pre-selected, and the random access procedure can be executed only on the selected APs 110. For example, the APs 110 used for the random access procedure may be an AP cluster commonly used for all terminals not connected to the network. The APs 110 used for the random access procedure may be selected so that the failure of random access detection by terminal 121 does not depend on the location of terminal 121. For example, they may be selected so that there is less area not covered by the APs 110 used for the random access procedure. The APs 110 used for the random access procedure will be referred to as the first set of antennas. In this way, by limiting the number of APs 110 used for the random access procedure, the processing load on the control device 100 is reduced. However, if the APs 110 used for the random access procedure are limited, the wireless quality provided to terminal 121 may be low during the period until an AP cluster for terminal 121 is selected. For example, suppose that when terminal 121 initiates a random access procedure, there is only one AP 110 that can receive the signal transmitted from terminal 121. In this case, terminal 121 will communicate only through that AP 110 until an AP cluster is selected for its device. Therefore, the wireless quality provided to terminal 121 will be lower compared to the wireless quality after an AP cluster has been selected. The AP 110 selected as the AP cluster for terminal 121 will be referred to as the second set of antennas.
[0018] In light of these circumstances, the control device 100 in this embodiment, upon receiving a message signal used in a random access procedure via the first set of antennas, selects one or more antennas included in the first set of antennas and antennas selected according to predetermined criteria from among the antennas not included in the first set of antennas as the second set of antennas, based on the measurement result of the received power of the received message signal. The message signal is, for example, message 1 or message 3 in a four-step random access procedure, or message A in a two-step random access procedure. Furthermore, when the control device 100 receives a reference signal via each of the antennas connected to its device, it updates the second set of antennas based on the measurement result of the received power of the received reference signal. The reference signal is, for example, SRS.
[0019] The control device 100 may select a second set of antennas within its own device. For example, the control device 100 may pre-associate one or more antennas not included in the first set of antennas with at least some of the antennas included in the first set of antennas. Then, based on the measurement result of the received power of the message signal, the control device 100 may select one or more antennas included in the first set of antennas as the second set of antennas, and further select the antennas not included in the first set of antennas that are pre-associated with each of the selected one or more antennas as the second set of antennas. In this way, by associating each of the antennas included in the first set of antennas with an antenna not included in the first set of antennas, the second set of antennas can include not only the first set of antennas but also antennas not included in the first set of antennas.
[0020] The method by which the control device 100 includes antennas not included in the first set of antennas in the second set is not limited to the above. For example, the control device 100 stores a history of combinations of measured received power values for each antenna when a signal is received at each antenna connected to the device. The control device 100 also estimates the received power of antennas not included in the first set of antennas from the measured received power values at the first set of antennas when a message signal is received at the first set of antennas, based on the history of combinations of measured received power values stored at the device. Then, when a message signal is acquired via the first set of antennas, the control device 100 selects the second set of antennas based on the measured received power value of the message signal at the first set of antennas and the estimated received power value of antennas not included in the first set of antennas. In this way, by estimating the received power of antennas not included in the first set of antennas based on the received power history of each antenna, the second set of antennas can include not only the first set of antennas but also antennas not included in the first set of antennas.
[0021] On the other hand, the second set of antennas may be selected by a communication device other than the control device 100. For example, the second set of antennas may be selected by RIC 131. In this case, the control device 100 can transmit a message signal acquired via the first set of antennas to RIC 131 and receive information indicating the second set of antennas selected by RIC 131. RIC 131 may select the second set of antennas using the same selection method as the control device 100 used to select the second set of antennas, or it may select the second set of antennas using a different method.
[0022] With this configuration, even if the AP 110 used in the random access procedure is limited to the first set of antennas, it becomes possible to communicate user data using a second set of antennas selected, which includes not only the first set of antennas but also AP 110 other than the first set of antennas, thereby improving the wireless quality provided to the terminal 121. Furthermore, if a reference signal is received through more AP 110s after the second set of antennas has been selected, the wireless quality provided to the terminal 121 can be further improved by updating the second set of antennas based on the measured value of the received power of this reference signal. An example of the configuration and operation of the control device 100 that operates in this manner will be described below.
[0023] (Overview of Control Device Operation) First, an overview of the operation of the control device 100 will be described. In this example, the operation of the control device 101 when establishing a connection with terminal 121 will be used as an example for explanation, but this example can also be applied to the operation of the control device 102 when establishing a connection with terminal 121. In the following explanation, terminals using the mobile communication system of this embodiment, including terminal 121, will be collectively referred to as terminal 120. Figure 2 shows an example of the processing flow executed when the control device 101 establishes a connection with terminal 121. First, the control device 101 identifies the AP 110 to be used when establishing a connection with terminal 120 (S201). The establishment of the connection between the control device 101 and terminal 120 can be performed using a random access procedure. For example, the control device 101 can identify the AP 110 by obtaining information from the RIC 131 to identify the AP 110 to be used when establishing a connection with terminal 120. The control device 101 instructs the AP110 connected to its own device (the first set of antennas) among the identified AP110s to output to the control device 101 a message signal for establishing a connection received from the terminal 120 (S202). For example, the control device 101 may send a control signal to the first set of antennas indicating that it should output to the control device 101 a signal received in the radio resources allocated for the random access procedure. In this way, the control device 101 can process message signals received by some of the AP110s connected to its own device and execute the procedure for establishing a connection with the terminal 120. This reduces the processing load on the control device 101.
[0024] Furthermore, the control device 101 identifies which APs 110 connected to its own device should output a reference signal for measuring wireless quality received from terminal 120 to the control device 101. For example, this set of APs could be all APs 110 connected to the control device 101. In this case, the control device 101 can use the measured value of the received power of the reference signal received by each AP 110 connected to its own device to select an AP cluster for terminal 120 that transmitted the reference signal. The control device 101 may also choose not to output a reference signal to the control device 101 for some of the APs 110 connected to its own device. In this case, the control device 101 can reduce the processing load compared to when all APs 110 connected to its own device output a reference signal. For example, the control device 101 may choose not to output a reference signal to the control device 101 for APs 110 located geographically far from terminal 121.
[0025] When the control device 101 receives a message signal from terminal 121 for establishing a connection (YES in S203), it selects an AP cluster (a second set of antennas) for communicating user data with terminal 121 based on this message signal (S204). For example, the control device 101 measures the received power of the message signal at each of the APs 110 that constitute the first set of antennas. Based on these measured values of received power, the control device 101 can then select a second set of antennas by inferring which APs 110 should be selected as the AP cluster for terminal 121. The control device 101 instructs the APs 110 selected as the second set of antennas to output a signal to the control device 101 that includes the user data received from terminal 121 (S205). For example, the control device 101 may send a control signal to the second set of antennas indicating that it should output to the control device 101 the signal received in the radio resource allocated for terminal 121 to transmit PUSCH. PUSCH is an abbreviation for Physical Uplink Shared Channel. The control device 101 then communicates with the terminal 121 using an AP cluster formed by a second set of antennas (S206). In this way, the control device 101 infers which APs 110 should be included in the AP cluster for terminal 121 based on the measured values of the received power of the message signal in each of the first set of antennas. The control device 101 then instructs the second set of antennas, which is composed of the inferred APs 110, to output the user data received from terminal 121, thereby enabling communication with terminal 121 using an AP cluster formed by APs 110 selected from a larger number of APs 110 than those in the first set of antennas. This improves the wireless quality provided to terminal 121 during communication with terminal 121 before the AP cluster is selected based on the reference signal transmitted from terminal 121.
[0026] Meanwhile, the control device 101 instructs each of the APs 110 connected to its device to output the reference signal received from the terminal 121 to the control device 101. For example, the control device 101 may send a control signal to each of the APs 110 connected to its device indicating that the signal received in the radio resource allocated by the terminal 121 for transmitting the reference signal should be output to the control device 101. When the control device 101 receives a reference signal for measuring radio quality from the terminal 121 via each of the APs 110 connected to its device (YES in S207), it updates the second set of antennas based on the respective reference signals (S208). For example, if the control device 101 receives the reference signal via all APs 110 connected to it, the control device 101 measures the received power of the reference signal at each AP 110. The control device 101 may then use these measured values of received power to select new APs 110 that should be part of the second set of antennas. The control device 101 may then update the second set of antennas using the newly selected APs 110. In this way, the control device 101 updates the second antenna set using the measured value of the reference signal received at each of the A110 connected to its device, thereby further improving the wireless quality available to the terminal 121.
[0027] (Circuit Configuration) An example of the configuration of the control device 101 described above will now be explained. Figure 3 is a diagram showing the hardware configuration of the control device 101. In one example, the control device 101 is configured to include a processor 301, ROM 302, RAM 303, storage device 304, and communication circuit 305. The processor 301 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or ASIC (Application-Specific Integrated Circuit). The processor 301 executes the overall processing of the device and the above-mentioned processing by reading and executing programs stored in the ROM 302 and storage device 304. The ROM 302 is a read-only memory in which information such as programs and various parameters related to the processing executed by the control device 101 is recorded. The RAM 303 functions as a workspace when the processor 301 executes programs and is a random access memory in which temporary information is recorded. The storage device 304 is configured, for example, by a removable external storage device. The communication circuit 305 is configured to include, for example, a circuit for wired or wireless communication of the control device 101. For example, the control devices 101 can communicate with each other using the communication circuit 305 for LTE or 5G.
[0028] (Functional Configuration) Figure 4 shows an example of the functional configuration of the control device 101. The control device 101 is configured to include, for example, a wireless communication control unit 401, an AP instruction unit 402, a wireless quality measurement unit 403, an AP selection unit 404, and an AP update unit 405. Figure 4 shows the functional configuration of the control device 101 in this embodiment, and the general configuration of the control device 101 is omitted. These functional units can be realized, for example, by the processor 301 executing a program stored in the ROM 302 or storage device 304 and controlling the communication circuit 305 as needed. However, it is not limited to this, and dedicated hardware for realizing each function may be provided, for example.
[0029] The wireless communication control unit 401 performs communication with the terminal 121. For example, the wireless communication control unit 401 can perform communication with the terminal 121 via one or more APs 110 connected to its own device. As an example, the wireless communication control unit 401 can allocate wireless resources to be used for transmission to the terminal 121, wireless resources to be used when the terminal 121 transmits, wireless resources to be used for transmitting message signals used when establishing communication with the terminal 121, and wireless resources to be used when the terminal 121 transmits reference signals. The allocated wireless resources can be notified to the terminal 121 using SSB or the like. SSB is an abbreviation for Synchronization Signal Block. The terminal 121 can use the notified wireless resources to communicate with the control device 101, transmit message signals and reference signals, etc.
[0030] The AP instruction unit 402 issues instructions to the AP 110 connected to its own device. For example, the AP instruction unit 402 may instruct the first set of antennas used to establish a connection with the terminal 121, which is one of the AP 110s connected to its own device, to output a message signal for establishing a connection transmitted from the terminal 121 to its own device. The AP instruction unit 402 may also instruct the AP 110 connected to its own device to output a reference signal for measuring the wireless quality transmitted from the terminal 121 to its own device. Furthermore, the AP instruction unit 402 may instruct the second set of antennas used for communicating user data with the terminal 121, which is selected based on the message signal and reference signal, to output user data transmitted from the terminal 121 to its own device. The AP instruction unit 402 may also issue instructions to the AP 110 by specifying a wireless resource allocated to transmit the signal to be output to its own device, and causing the received signal to be output by that wireless resource.
[0031] The wireless quality measurement unit 403 measures the received power at each of the APs 110 connected to its device. For example, when the wireless quality measurement unit 403 receives a message signal from terminal 121 via the first antenna array, it can measure the received power of the message signal at each of the first antenna arrays. Also, when the wireless quality measurement unit 403 receives a reference signal from terminal 121 via an AP 110 connected to its device, it can measure the received power of the reference signal at each of the APs 110 connected to its device.
[0032] The AP selection unit 404 selects a second set of antennas. For example, if the AP selection unit 404 receives a message signal via the first set of antennas, it may select a second set of antennas based on the received power of the message signal at each of the first set of antennas measured by the radio quality measurement unit 403. If a second set of antennas is selected at RIC 131, the AP selection unit 404 may notify RIC 131 of the received power measured at RIC 131. The AP selection unit 404 may then obtain identification information from RIC 131 to identify the second set of antennas selected at RIC 131. Based on the identification information obtained from RIC 131, the AP selection unit 404 may select a second set of antennas.
[0033] The AP update unit 405 updates the second antenna set. For example, when the AP selection unit 404 receives a reference signal via an AP 110 connected to its device, it may select a second antenna set based on the received power of the reference signal at each AP 110 measured by the radio quality measurement unit 403. When a second antenna set is selected at RIC 131, the AP selection unit 404 may notify RIC 131 of the received power measured by the radio quality measurement unit 403. The AP selection unit 404 may then obtain identification information from RIC 131 to identify the selected second antenna set. The AP update unit 405 may update the second antenna set based on the second antenna set identified based on the identification information obtained from RIC 131.
[0034] (Processing Flow) The processing flow when the control device 101 communicates with the terminal 121 via AP 110 will be explained. Figure 5 shows an example of a sequence of messages exchanged between communication devices when the control device 101 communicates with the terminal 121 via AP 110. In this example, as shown in Figure 1, the control device 101 is connected to AP 111 to AP 115. First, the control device 101 identifies the AP 110 that should be used when establishing a connection with the terminal 120. For example, the control device 101 can obtain information from RIC 131 to identify the AP 110 that should be used when establishing a connection with the terminal 120 (S501). The control device 101 can obtain this information using CONTROL services and INSERT services messages specified in E2AP. In this example, it is assumed that AP 111 and AP 114 have been identified as the AP 110 that should be used when establishing a connection with the terminal 120.
[0035] The control device 101 issues a first instruction to the AP 110 connected to its own device (S502). For example, as the first instruction, the control device 101 instructs the AP 110 connected to its own device (the first set of antennas), which has been identified as the AP 110 to be used when establishing a connection with the terminal 120, to output a message signal to the control device 101 that includes a message for establishing a connection received from the terminal 120. For example, the control device 101 issues a first instruction to AP 111 and AP 114.
[0036] For example, a radio frame used in communication with terminal 121 consists of 10 subframes in the time domain, and each subframe may consist of one or more slots depending on the subcarrier interval. One slot may consist of 14 OFDM symbols. The radio frame may also be divided into RBs consisting of 12 subcarriers in the frequency domain. A unit of radio resource identified by one OFDM symbol in the time domain and one subcarrier in the frequency domain is called a resource element (RE). The control device 101 may specify to each AP 110 which RE should be output to the control device 101 for each slot. The control device 101 also allocates radio resources to be used for transmission such as PUSCH, PDSCH, SRS, and RACH for communication with each terminal 120. PDSCH is an abbreviation for Physical Data Shared Channel. Therefore, the control device 101 can specify an RE corresponding to the radio resource allocated for RACH transmission and instruct the first antenna array (AP111, AP114) to output the signal received by this RE to the control device 101. The control device 101 may also specify to AP110 the radio resources to be output to its device in units of RB.
[0037] When terminal 121 is powered on and starts up, it begins to connect to the network. For example, terminal 121 attempts to receive an SSB transmitted via an AP 110 located near its device. The SSB may be transmitted via all APs 110 connected to the control device 101, or via the first set of antennas. If the SSB is transmitted via all APs connected to the control device 101, the number of APs 110 transmitting the SSB increases, thus increasing the probability that the SSB will be detected by terminal 120. On the other hand, if the SSB is transmitted via the first set of antennas, the number of APs 110 to which the control device 101 outputs the SSB decreases, thus reducing the processing load on the control device 101 and reducing the amount of traffic between the control device 101 and the APs 110. By receiving the SSB, terminal 121 can identify the radio resource (RACH) to which it should send a message signal to establish a connection. Terminal 121 then sends a message to establish a connection to the identified radio resource. For example, when terminal 121 establishes a connection using a four-step random access procedure, it sends message 1 (Msg1) containing a Random Access Preamble (S503). Msg1 is received by AP111 and AP114 and output to control device 101. Msg1 may also be received by AP112, AP113, and AP115. However, AP112, AP113, and AP115 do not output Msg1 to control device 101 because they have not received instructions from control device 101 to output a message signal containing the connection establishment message received from terminal 120 to control device 101. In response to Msg1, control device 101 sends message 2 (Msg2) containing a Random Access Response. Msg2 may include a UL grant indicating the radio resources that terminal 121 should use to send message 3 (Msg3). Msg2 is transmitted to terminal 121 via AP111 and AP114.
[0038] Terminal 121 transmits Msg3, which includes an RRC Connection Request, based on the UL grant contained in Msg2. Msg3 is output to the control unit 101 via AP111 and AP114. The control unit 101 may instruct AP111 and AP114 to output the signal received by the radio resource corresponding to the UL grant to the control unit 101, based on the allocation of the UL grant to terminal 121. In response to Msg3, the control unit 101 transmits message 4 (Msg4), which includes an RRC Connection Setup. Msg4 is transmitted to terminal 121 via AP111 and AP114. Subsequently, the procedure for RRC connection is performed between terminal 121 and the control unit 101 (S507-S509). For example, terminal 121 sends message 5 (Msg5) including RRC Connection Setup Complete (S507). Control device 101 sends RRC Connection Reconfiguration (S508). Terminal 121 sends RRC Connection Reconfiguration Complete (S509).
[0039] The control device 101 can measure the received power from terminal 121 at AP 111 and AP 114 using Msg1 and Msg3 received in the four-step random access procedure. By measuring the received power using Msg1, the control device 101 can select a second antenna set at an early stage. On the other hand, by measuring the received power using Msg3, the control device 101 can select a second antenna set when it becomes more certain that terminal 121 is connected to the network. Furthermore, if a two-step random access procedure is used to establish a connection with terminal 121, the control device 101 can measure the received power from terminal 121 at AP 111 and AP 114 using message A (Msg A) which contains the information of Msg1 and Msg3 from the four-step random access procedure. Thus, this technology is also applicable to two-step random access procedures.
[0040] The control device 101 selects a second set of antennas for terminal 121 according to predetermined criteria based on the measured values of the received power at AP111 and AP114. For example, the control device 101 may select one AP110 from the first set of antennas and select this AP110 and one or more AP110s pre-associated with it as the second set of antennas. As an example, suppose AP112 is pre-associated with AP111, and AP113 and AP115 are pre-associated with AP114. First, the control device 101 compares the received power at AP111 and AP114 and selects either AP111 or AP114. For example, the control device 101 selects AP111 based on the fact that the received power at AP111 was higher than the received power at AP114. In this case, the control device 101 selects AP111 and AP112 associated with AP111 as the second set of antennas. Furthermore, the control device 101 may select AP114 based on the fact that the received power at AP114 was higher than the received power at AP111. In this case, the control device 101 selects AP114 and the AP113 and AP115 associated with AP114 as a second set of antennas. In this way, one AP110 that is determined to have good wireless quality is selected from the first set of antennas, and the AP110 that is pre-associated with the selected AP110 is presumed to be an AP110 with good wireless quality with respect to the terminal 121. This allows for the selection of a second set of antennas that includes an AP110 with a high probability of having good wireless quality without measuring the received power at AP110 that is not included in the first set of antennas. Note that each AP110 included in the first set of antennas may be pre-associated with other AP110s based on their geographical location. For example, AP110s whose distance from each other is less than a predetermined threshold may be associated. Alternatively, a predetermined number of AP110s may be associated with the first set of antennas, starting with those closest to the first AP110. The control device 101 may select multiple antennas from the first set of antennas to form a second set of antennas.For example, the control device 101 may select a plurality of AP110s with received power exceeding a predetermined threshold as a second set of antennas. In this case, the AP110s associated with each of the selected first sets of antennas may be selected as the second set of antennas.
[0041] The method for selecting the second set of antennas based on the received power at each of the first set of antennas is not limited to the above. For example, the second set of antennas may be selected based on the received power measured at each AP 110 in past communications with terminal 120. For example, the control device 101 measures the received power at each AP 110 using the same reference signal received from terminal 120 via each AP 110 connected to itself. The control device 101 stores the combination of measured values obtained as received power at each AP 110 for the same reference signal. For example, when the control device 101 receives the same reference signal via APs 111 to 115, it stores the measured values obtained as received power at each of APs 111 to 115, associating them with the identifier of each AP 110. The combination of measured values of received power is stored separately for each received reference signal. Then, when the control device 101 receives a message signal from terminal 121 to establish a connection via the first set of antennas, it measures the received power of this message signal at each of the first set of antennas. The control device 101 calculates the correlation between the received power of the message signal measured at each of the first antenna sets and the received power of each of the first antenna sets from the stored combination of received power measurements. For example, the control device 101 calculates the correlation between the received power of AP111 and AP114 for the received message signal and the received power of AP111 and AP114 from the stored combination of received power measurements. Then it identifies the combination of received power measurements with a high correlation. In this way, the received power of AP112, AP113, and AP115 for which there are no received power measurements for the message signal can be estimated. For example, if the combination of received power measurements with the highest correlation is identified, the control device 101 can select a predetermined number of AP110s as the second antenna set from the identified combination of received power measurements, in order from those with the highest received power.Furthermore, if a predetermined number of received power sets are identified from combinations of received power measurements with high correlation, the control device 101 may perform statistical processing, such as averaging, for each AP 110 for the multiple identified received power sets. Then, the control device 101 may select a predetermined number of AP 110s as a second set of antennas, in descending order of received power, using the statistically processed combinations of received power measurements. The control device 101 may also select AP 110s with received power exceeding a predetermined threshold as a second set of antennas, based on the identified combinations of received power measurements or the statistically processed combinations of received power measurements. The control device 101 may also select a second set of antennas using a trained model obtained by machine learning with the combinations of received power measurements as training data. As an example, the training data may consist of multiple datasets in which the received power of each antenna set from the combinations of received power measurements is used as an explanatory variable, and information indicating a predetermined number of AP 110s in descending order of received power in that combination of received power measurements is used as the objective variable. By performing machine learning using this training data, a trained model can be generated that, when the received power at each of the first antenna sets is input, outputs information indicating a predetermined number of AP110s that are estimated to have high received power. In this case, the control device 101 can input the measured values of the received power of the message signals at each of the first antenna sets into the trained model, thereby acquiring AP110s that are estimated to have high received power from among the first antenna sets and AP110s not included in the first antenna sets as a second antenna set.
[0042] The control device 101 issues a second instruction to the AP 110 connected to its device for communication with the terminal 121 (S510). For example, as a second instruction, the control device 101 instructs the AP 110 selected as the second set of antennas for terminal 121 to output user data received from terminal 121 to the control device 101. As an example, the control device 101 may specify an RE corresponding to the radio resource allocated for terminal 121 to transmit PUSCH and instruct the second set of antennas to output the signal received at this RE to the control device 101. Also, as a second instruction, the control device 101 instructs each of the AP 110 connected to its device to output a reference signal for measuring radio quality received from terminal 121 to the control device 101. As an example, the control device 101 may specify an RE corresponding to the radio resource allocated for terminal 121 to transmit the reference signal and instruct the RE to output the signal received at this RE to the control device 101. In Figure 5, assume that AP111 and AP112, which is pre-associated with AP111, receive a second instruction as a second set of antennas. Also assume that all AP110 connected to the control device 101 receive a second instruction that includes the instruction to output a reference signal. As a result, user data is communicated with terminal 121 via AP111 and AP112, and the reference signal transmitted from terminal 121 is output to the control device 101 via AP111 to AP115.
[0043] The control device 101 communicates with the terminal 121 for user data via AP111 and AP112. For example, a PUSCH transmitted by the terminal 121 is output to the control device 101 via AP111 and AP112 (S511). The control device 101 also transmits a PDSCH to the terminal 121 via AP111 and AP112 (S512).
[0044] The control device 101 receives a reference signal transmitted by the terminal 121 via AP111 to AP115 (S513). The control device 101 updates the second set of antennas for the terminal 121 based on the measured values of the received power at each of AP111 to AP115. For example, a predetermined number of AP110s may be selected as the second set of antennas in descending order of the measured values of the received power at each of AP111 to AP115. Alternatively, AP110s may be selected as the second set of antennas in which the measured values of the received power at each of AP111 to AP115 exceed a predetermined threshold. Furthermore, AP110s may be selected as the second set of antennas in which the sum of the measured values of the received power at each of AP111 to AP115 exceeds a predetermined threshold. The method of selecting the second set of antennas based on the reference signal received through each of AP110 is not limited to these. For example, the second set of antennas may be selected by the control device 101 or by the RIC 131. When RIC 131 selects a second set of antennas, the control device 101 notifies RIC 131 of the received power at each of APs 111 to 115 (S514). For example, the control device 101 may associate identification information for AP 110 with the received power at AP 110 and notify RIC 131. As an example, the control device 101 may notify RIC 131 using a REPORT services message specified in E2AP or performance data specified in O1AP. The control device 101 then obtains information from RIC 131 that identifies the second set of antennas (S515). For example, the information that identifies the second set of antennas may be the identification information for AP 110. For example, the control device 101 may obtain information identifying the second set of antennas using CONTROL services messages and INSERT services messages specified in E2AP. By selecting the second set of antennas, the RIC 131 may select an AP 110 that is more suitable for communication with the terminal 121.For example, the RIC 131 can select a second set of antennas for the terminal 121 from a set of APs including not only the AP 110 connected to the control device 101 but also the AP 110 connected to the control device 102.
[0045] In response to the update of the second set of antennas for the terminal 121, the control device 101 issues a third instruction to the AP 110 connected to its own device (S516). For example, as the third instruction, the control device 101 instructs the AP 110 selected as the updated second set of antennas for the terminal 121 to output the user data received from the terminal 121 to the control device 101. As an example, the control device 101 can specify the RE corresponding to the radio resource allocated for the terminal 121 to transmit PUSCH and instruct the updated second set of antennas to output the signal received by this RE to the control device 101. For example, the control device 101 can issue a third notification to the APs 111, 112, and 115 as the updated second set of antennas. The control device 101 communicates with the terminal 121 using the updated second set of antennas (S517). For example, the control device 101 receives the PUSCH transmitted from the terminal 121 via the APs 111, 112, and 115.
[0046] (Modification 1) In the above example, the control device 101 was described using a message signal to establish a connection and select a second set of antennas. The second set of antennas using the message signal may be selected by the RIC 131. Figure 6 shows an example of a message sequence exchanged between the control device 101 and the RIC 131 in this modification. In Figure 6, the same operations as in Figure 5 are given the same reference numerals and the explanation is omitted. That is, the control device 101 operates in the same way as in Figure 5 with respect to the AP 110 and the terminal 121. When the control device 101 completes a four-step random access with the terminal 121 (S503 to S506), it notifies the RIC 131 of the measured value of the received power of the message signal at each of the first set of antennas (S601). For example, the control device 101 may associate identification information for the AP 110 with the measured value of the received power at the AP 110 and notify the RIC 131 of this. For example, the control device 101 may notify the RIC 131 using REPORT Services messages in E2AP or performance data specified in O1AP. The RIC 131 may select a second set of antennas using the measured value of the received power at AP 110 collected from the control device 101. For example, the RIC 131 may select a second set of antennas using the method by which the control device 101 selects a second set of antennas as described above. The control device 101 then obtains information identifying the second set of antennas from the RIC 131 (S602). For example, the information identifying the second set of antennas may be the identification information of AP 110. For example, the control device 101 may obtain information identifying the second set of antennas using CONTROL Services messages or INSERT Services messages in E2AP. By selecting a second set of antennas, RIC 131 can select an AP 110 that is more suitable for communication with terminal 121. For example, RIC 131 can select a second set of antennas for terminal 121 from a set of APs that includes not only AP 110 connected to control device 101, but also AP 110 connected to control device 102.
[0047] Figure 6 shows an example in which the control device 101 notifies the RIC 131 of the received power of the message signal after the exchange of message 4 of the four-step random access procedure is completed. However, the method by which the control device 101 notifies the RIC 131 of the received power of the message signal is not limited to this. For example, after receiving message 1 which includes a random access preamble, the control device 101 may notify the RIC 131 of the received power measured using the random access preamble. This allows for the selection of a second antenna array at an earlier timing, thereby improving the wireless quality provided to the terminal 121 more quickly. Furthermore, if the received power of the message signal is notified to the RIC 131 after the exchange of message 4 is completed, the second antenna array can be selected at a time when the connection is more certain, thus enabling more effective use of wireless resources. The control device 101 may also perform a two-step random access procedure with the terminal 121. In this case, the control device 101 may notify the RIC 131 of the received power measured using message A, which includes the random access preamble, after the exchange of message B, which corresponds to message 2 and message 4 in the four-step random access procedure, is completed. Alternatively, the control device 101 may notify the RIC 131 after receiving message A.
[0048] (Other Modification Examples) For example, the control device 101 may be configured such that all signals received by the AP 110 connected to the device itself are output to the control device 101. The control device 101 can acquire information necessary for processing from the signals output to the control device 101 by the AP 110. For example, the control device 101 can acquire a message signal for establishing a connection from the signals output by each of the APs 110, from the signals output from the set of first antennas. Also, the control device 101 can acquire a reference signal for measuring radio quality from the signals output by each of the APs 110. Further, the control device 101 can acquire user data included in the signals output from the set of second antennas among the signals output by each of the APs 110. For example, the control device 101 can acquire, from the signals output from each of the APs 110, the portion corresponding to the radio resource containing the necessary information, from the output of the AP 100 from which the necessary information is to be acquired. Thus, the control device 101 may filter the signals output by the AP 110 to acquire the necessary information. In this case, the processing load of the control device 101 may increase in order to select the information to be used in the control device 101. However, since the control device 101 can acquire all the information received by the AP 110, it becomes possible to select the second AP using the necessary information therefrom.
[0049] As described above, according to this embodiment, when the control device 100 receives a message signal used in a random access procedure via the first set of antennas, it selects one or more antennas included in the first set of antennas and antennas selected from those not included in the first set of antennas according to predetermined criteria as the second set of antennas, based on the measurement result of the received power of the received message signal. Then, when the control device 100 receives a reference signal via each of the antennas connected to itself, it updates the second set of antennas based on the measurement result of the received power of the received reference signal. With this configuration, even if the APs 110 used in the random access procedure are limited to the first set of antennas, it becomes possible to communicate user data using the second set of antennas selected to include not only the first set of antennas but also APs 110 other than the first set of antennas, thereby improving wireless quality. Furthermore, if the reference signal is received via more APs 110 after the second set of antennas has been selected, the wireless quality can be further improved by updating the second set of antennas. This makes it possible to improve wireless quality in mobile communication systems using cell-free technology while reducing the processing load on signal processing and control devices. Therefore, it will be possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."
[0050] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention.
[0051] This application claims priority based on Japanese Patent Application No. 2025-16974, filed on February 4, 2025, and all of its contents are incorporated herein by reference.
Claims
1. A control device connected to a plurality of antennas, which communicates user data with a terminal device using at least one of the plurality of antennas, comprising: acquisition means for acquiring a message signal transmitted by the terminal device to establish a connection with the control device via a first set of antennas included in the plurality of antennas, and acquiring a reference signal for measuring radio quality transmitted by the terminal device via each of the plurality of antennas; and control means for controlling the communication of user data with the terminal device using a second set of antennas selected based on the message signal or the reference signal, wherein when the message signal is acquired via the first set of antennas, the received power of the message signal is measured at each of the antennas included in the first set of antennas, and one or more antennas included in the first set of antennas selected based on the results of the measurement, and antennas included in the plurality of antennas but not included in the first set of antennas selected according to predetermined criteria, are selected as the second set of antennas. A control device that, after the second set of antennas has been selected, when the reference signal is acquired through each of the plurality of antennas, measures the received power of the reference signal at each of the plurality of antennas, and updates the second set of antennas with the antenna selected from the plurality of antennas based on the results of the measurement.
2. The control device according to claim 1, further comprising selection means for selecting a set of second antennas based on the message signal or the reference signal.
3. A control device according to claim 2, wherein at least a portion of the antennas included in the first set of antennas are pre-associated with one or more antennas included in the plurality of antennas but not included in the first set of antennas, and the selection means selects one or more antennas included in the first set of antennas as the second set of antennas based on the measurement result of the received power of the message signal, and further selects the antennas included in the plurality of antennas but not included in the first set of antennas that are pre-associated with each of the selected one or more antennas as the second set of antennas.
4. A control device according to claim 2, further comprising: a storage means for storing a history of combinations of measured values of received power of signals received at each of the plurality of antennas; and an estimation means for estimating the received power of an antenna included in the plurality of antennas but not included in the first antenna set, based on the history of combinations of measured values of received power at the first antenna set, wherein the selection means selects the second antenna set based on the measured value of the received power of the message signal at the first antenna set and the estimated value of the received power of an antenna included in the plurality of antennas but not included in the first antenna set, when the message signal is acquired via the first antenna set.
5. The control device according to claim 1, further comprising communication means for transmitting the message signal acquired via the first set of antennas to another control device operating as a Radio Intelligent Controller (RIC) of an Open-Radio Access Network (O-RAN), and for receiving information indicating the second set of antennas selected by the other control device.
6. The control device according to claim 5, wherein the communication means transmits the message signal to the other control means after receiving a random access preamble for a four-step random access procedure or a two-step random access procedure as defined in the Third Generation Partnership Project (3GPP) cellular communication standard via the first antenna array.
7. The control device according to claim 5, wherein the communication means transmits the message signal to the other control means after receiving a message 4 of a four-step random access procedure or a message 2 of a two-step random access procedure as defined in the Third Generation Partnership Project (3GPP) cellular communication standard via the first antenna array.
8. The control device according to any one of claims 1 to 5, wherein the message signal is message 1 of a four-step random access procedure as defined in the Third Generation Partnership Project (3GPP) cellular communication standard.
9. The control device according to any one of claims 1 to 5, wherein the message signal is message A of a two-step random access procedure as defined in the Third Generation Partnership Project (3GPP) cellular communication standard.
10. The control device according to any one of claims 1 to 9, wherein the reference signal is a Sounding Reference Signal as defined in the Third Generation Partnership Project (3GPP) cellular communication standard.
11. A control method performed by a control device connected to a plurality of antennas and using at least one of the plurality of antennas to communicate user data with a terminal device, comprising: acquiring a message signal for establishing a connection with the control device transmitted by the terminal device via a first set of antennas included in the plurality of antennas; acquiring a reference signal for measuring radio quality transmitted by the terminal device via each of the plurality of antennas; and controlling the control device to communicate user data with the terminal device using a second set of antennas selected based on the message signal or the reference signal, wherein when the message signal is acquired via the first set of antennas, the received power of the message signal is measured at each of the antennas included in the first set of antennas, and one or more antennas included in the first set of antennas selected based on the results of the measurement, and antennas included in the plurality of antennas but not included in the first set of antennas selected according to predetermined criteria, are selected as the second set of antennas. A control method characterized in that, after the second set of antennas is selected, if the reference signal is acquired through each of the plurality of antennas, the received power of the reference signal is measured at each of the plurality of antennas, and the second set of antennas is updated by the antenna selected from the plurality of antennas based on the result of the measurement.
12. A program for causing a computer to function as each of the means of the control device described in any one of claims 1 to 10.