Communication control device, communication control method, and program

Abstract

Select the AP that will perform the RACH process. [Solution] The communication control device is a communication control device that communicates information with a DU (Distributed Unit) located in a self-free wireless communication system that uses a plurality of distributed APs to reduce the effects of interference, and comprises a storage unit that stores a RACH AP list which is a list that identifies one or more APs that perform RACH (Random Access Channel) Preamble detection processing, and a control unit that updates the RACH AP list when the DU notifies that detection of the RACH Preamble has failed as a result of detecting the RACH Preamble based on the RACH AP list.

Description

Technical Field

[0001] The present invention relates to a communication control device, a communication control method, and a program.

Background Art

[0002] Conventionally, in a self-free wireless communication system, a plurality of APs (Access Points) are geographically distributed and information communication with a UE (User Equipment) is performed. For example, Non-Patent Document 1 discloses a technique for transmitting a preamble of RACH (Random Access Channel) processing from a UE to an AP. Specifically, it is disclosed that the UE receives SSBs from a plurality of APs and transmits a preamble to the AP with the maximum signal-to-noise ratio (SNR: Signal-Noise Ratio).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By using such conventional technologies, it is possible to establish optimal information communication based on the relative positional relationship between the UE and AP at that particular time. However, the wireless environment changes dynamically in response to factors such as increases or decreases in the number of APs, adjustments to the tilt angle, shielding by nearby structures, and seasonal changes in trees (changes in the degree of shielding due to foliage growth, etc.). Therefore, there was a challenge in that it is preferable to dynamically change the AP to which the UE connects.

[0005] For example, using conventional technology, the AP to which the UE connects is AP1, which has the highest SNR. Therefore, if an obstruction is placed between the UE and the AP, it is possible that information communication will become impossible. Another possible way to address this problem is to select all APs that share a common higher-level node (e.g., DU: Destributed Unit) and transmit a preamble, but this raises concerns about an increased load on the higher-level node.

[0006] This invention has been made in consideration of these circumstances, and its purpose is to provide a communication control device, a communication control method, and a program that can select an AP to perform RACH processing. [Means for solving the problem]

[0007] (A1) One aspect of the present invention is a self-free wireless communication system that reduces the effects of interference by using a plurality of distributed APs, a DU (Distributed Unit), and a RIC (RAN Intelligent Controller), and is a wireless communication system that includes an interface for notifying the DU of a RACH AP list, which is a list that identifies one or more APs that perform RACH (Random Access Channel) Preamble detection processing. (A2) In addition, one aspect of the present invention is the wireless communication system described in (A1) above, wherein the DU has an interface that detects a RACH Preamble based on the notified RACH AP list and notifies the RIC if detection fails. (A3) In addition, in the wireless communication system described in (A2) above, the interface notified from the DU to the RIC when detection of the RACH Preamble fails includes at least the reception quality for each of the multiple APs. (A4) In addition, in the wireless communication system described in (A3) above, the interface notified from the DU to the RIC when the detection of the RACH Preamble fails further includes the reception quality for the synthesized AP. (A5) In another aspect of the present invention, in any of the wireless communication systems described in (A1) to (A4) above, the interface for notifying the RACH AP list from the RIC to the DU is included in the E2 interface between the DU and the RIC. (A6) In another aspect of the present invention, in any of the wireless communication systems described in (A1) to (A5) above, the interface to which the RIC is notified from the DU when the detection of the RACH Preamble fails is included in the E2 interface or the O1 interface between the DU and the RIC. (A7) Another aspect of the present invention is a communication control method for controlling a self-free wireless communication system that reduces the effects of interference using a plurality of distributed APs, a DU (Distributed Unit), and a RIC (RAN Intelligent Controller), the method comprising the step of notifying the DU of a RACH AP list, which is a list that identifies one or more APs that perform RACH (Random Access Channel) Preamble detection processing. (A8) Another aspect of the present invention is a program that causes a computer to execute a communication control method for controlling a self-free wireless communication system that reduces the effects of interference using a plurality of distributed APs, a DU (Distributed Unit), and a RIC (RAN Intelligent Controller), the program which causes the computer to execute a step of notifying the DU of a RACH AP list, which is a list that identifies one or more APs that perform RACH (Random Access Channel) Preamble detection processing.

[0008] (B1) One aspect of the present invention is a communication control device that communicates information with a Distributed Unit (DU) located in a self-free wireless communication system that uses a plurality of distributed APs to reduce the effects of interference, and comprises: a storage unit that stores a RACH AP list which is a list that identifies one or more APs that perform RACH (Random Access Channel) Preamble detection processing; and a control unit that updates the RACH AP list when the DU notifies that detection of the RACH Preamble has failed as a result of detection based on the RACH AP list. (B2) In addition, in one aspect of the present invention, in the communication control device described in (B1) above, the control unit refers to the AP cluster of the UE (User Equipment) in communication and, if the list contains APs that can be recognized by multiple UEs, updates the RACH AP list by removing one of them from the list. (B3) In addition, in one aspect of the present invention, in the communication control device of (B1) or (B2) described above, the storage unit further stores a list of APs that failed to be detected, and the control unit updates the RACH AP list by adding neighboring APs to the APs shown in the list of APs that failed to be detected stored in the storage unit. (B4) In addition, in one aspect of the present invention, any of the communication control devices described in (B1) to (B3) above is a communication control device that communicates information with a plurality of DUs, and the control unit updates the RACH AP list by preferentially adding multihoming APs that are located at the boundary of the plurality of DUs and connected to the plurality of DUs. (B5) Another aspect of the present invention is a communication control method for communicating information with a Distributed Unit (DU) located in a self-free wireless communication system that uses a plurality of distributed APs to reduce the effects of interference, comprising: a storage step of storing a RACH AP list, which is a list of one or more APs that perform RACH (Random Access Channel) Preamble detection processing; and a control step of updating the RACH AP list when the DU notifies that detection of the RACH Preamble has failed as a result of detection based on the RACH AP list. (B6) Another aspect of the present invention is a program that causes a computer to communicate information with a Distributed Unit (DU) located in a self-free wireless communication system that reduces the effects of interference using a plurality of distributed APs, the program comprising: a storage step of storing a RACH AP list, which is a list of one or more APs that perform RACH (Random Access Channel) Preamble detection processing; and a control step of updating the RACH AP list when the DU notifies that detection of the RACH Preamble has failed as a result of detection based on the RACH AP list. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a wireless communication system, a communication control method, and a program that can select an AP that performs RACH processing. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram for explaining the outline of the wireless communication system according to this embodiment. [Figure 2] This is a diagram for conceptually explaining the wireless communication method according to this embodiment. [Figure 3] This is a sequence diagram showing the flow of a series of processes of the wireless communication method according to this embodiment. [Figure 4] This is a diagram for explaining an example in the case of prioritizing the multi-homing AP in the wireless communication system according to this embodiment. [Figure 5] This is a first diagram showing an example of an identifier for identifying devices in the wireless communication system according to this embodiment. [Figure 6] This is a second diagram showing an example of an identifier for identifying devices in the wireless communication system according to this embodiment. [Figure 7] This is a third diagram showing an example of an identifier for identifying devices in the wireless communication system according to this embodiment. [Figure 8] This is a fourth diagram showing an example of an identifier for identifying devices in the wireless communication system according to this embodiment. [Figure 9] This is a fifth diagram showing an example of an identifier for identifying devices in the wireless communication system according to this embodiment. [Figure 10] This is a sixth diagram showing an example of an identifier for identifying devices in the wireless communication system according to this embodiment. <00​​​​​​​​​​​​​​[Embodiment] Preferred embodiments of a wireless communication system, a communication control method, and a program according to aspects of the present invention will be described in detail below with reference to the accompanying drawings. Note that the aspects of the present invention are not limited to these embodiments, and also include those with various modifications or improvements. That is, the components described below include those that can be easily assumed by those skilled in the art and substantially identical ones, and the components described below can be combined as appropriate. Also, various omissions, substitutions, or changes of the components can be made without departing from the gist of the present invention. Also, in the following drawings, in order to make each configuration easy to understand, the scale, number, etc. in each structure may be different from those in the actual structure.

[0012] [Wireless Communication System] FIG. 1 is a diagram for explaining the outline of the wireless communication system according to the present embodiment. First, the outline of the wireless communication system 1 will be described while referring to the figure. The wireless communication system 1 has a configuration based on, for example, the specifications of O-RAN (Open Radio Access Network). However, in the example shown in the figure, some configurations are omitted for simplification of explanation. The wireless communication system 1 includes at least one RIC (RAN Intelligent Controller), a plurality of DUs (Distributed Units), a plurality of APs (Access Points), and a plurality of UEs (User Equipment).

[0013] [[ID=I1]] The RIC is a component defined by the O-RAN architecture and performs control so that wireless communication in the lower nodes is optimized. Also, the RIC optimizes the entire network by performing information communication with an orchestrator (not shown) of the upper node. A plurality of DUs are connected to the lower nodes of the RIC.

[0014] In the following description, RIC may be referred to as the communication control device 10. The communication control device 10 comprises a control unit 11 and a storage unit 12 as its functional configuration. The control unit 11 is configured to include at least a processor as a component and performs control for network optimization. The storage unit 12 is configured to include at least memory elements and stores information that the control unit 11 refers to when processing. The control unit 11 performs control while referring to the information stored in the storage unit 12.

[0015] In the O-RAN architecture, the DU (Digital Unit) is responsible for signal modulation and demodulation, MAC layer communication control, and other functions. The DU is also called a distributed station. The DU may be located on the Radio Unit (RU) side, which controls the antennas, or on the Central Unit (CU) side, which is the aggregation station. Multiple access points (APs) are connected to the lower nodes of the DU.

[0016] An AP is an access point that communicates directly with an UE. In wireless communication system 1, APs are distributed and placed on structures, etc. An AP is connected to one or more UEs. In the illustrated example, an AP is connected to one UE, but the system is not limited to this example; an AP may be connected to multiple UEs, and one UE may be connected to multiple APs.

[0017] A UE is a terminal device used by a user, comprising at least a processor and memory, and having wireless communication capabilities. Specifically, a UE may be a smartphone, tablet, laptop, wearable device, etc.

[0018] [RACH processing] Here, we will briefly explain the RACH (Random Access Channel) processing in cell-free wireless communication systems and its problems. In cell-free wireless communication systems, the DU broadcasts burst signals (SSB: Synchronization Signals / physical broadcast channel Block). The UE, upon receiving the SSB, returns a RACH Preamble if it wishes to communicate. However, conventionally, there was a problem in that only one AP could be selected.

[0019] According to this embodiment, the UE returns a RACH Preamble to each AP, and the DU synthesizes the signals using diversity reception technology. In other words, in this embodiment, even if shielding occurs in the area handled by the DU, the success rate of Preamble detection is increased. To put it another way, this embodiment can be described as expanding the RACH area across a surface. It can also be described as reducing the effects of interference. However, if all APs placed as subordinate nodes of the DU are targeted, there is a concern that the processing load on the DU will increase.

[0020] Therefore, according to this embodiment, the RIC creates a list of target APs and targets the APs included in that list. This list is dynamically changed in response to changes in the signal strength of the radio waves received by the UE. This list is notified from the RIC to the DU as the RACH AP list (hereinafter simply referred to as the AP list). The DU uses the APs included in the AP list to detect preambles. By adopting this configuration, the processing load on the DU is reduced compared to the case where all APs placed as subordinate nodes of the DU are targeted.

[0021] Note that the number of APs included in the AP list only needs to be one or more; it does not necessarily need to be multiple. If the DU repeatedly fails to detect a Preamble, a new AP will be added by the RIC. Also, if the DU repeatedly succeeds in detecting a Preamble, the RIC will determine if there are any unnecessary APs, and if so, it will remove those APs from the AP list.

[0022] The criteria for determining successful Preamble detection are arbitrary. For example, if a DU receives Preambles from multiple APs, the DU may combine the multiple Preambles and determine whether detection is successful based on whether the combined received level (e.g., Reference Signal Received Power (RSRP)) exceeds a detection threshold. The method of signal combining is arbitrary, but for example, it may be done by combining signals with the maximum ratio using diversity reception technology.

[0023] [Wireless communication method] Figure 2 is a diagram for conceptually illustrating the wireless communication method according to this embodiment. Next, a conceptual explanation will be given of an example of a wireless communication method implemented using the wireless communication system 1 described above. The figure shows multiple APs (Access Points) arranged in a distributed manner.

[0024] Figure 2(A) shows an example of a situation where detection failures frequently occur due to changes in the wireless environment. The figure shows two APs performing RACH processing, schematically illustrating the occurrence of shielding. When the radio wave strength changes (mainly degrades) due to shielding, it is possible to maintain the quality of wireless communication by selecting a new AP and adding it to the AP list.

[0025] Figure 2(B) shows an example where the quality of wireless communication can be maintained by adding a new AP that performs RACH processing. In the example shown, one new AP has been added from the state in Figure 2(B). The added AP is located in a position unaffected by shielding. In this way, by adding a new AP that performs RACH processing to the AP list, it is possible to prevent the degradation of wireless communication quality. Note that when adding a new AP that performs RACH processing to the AP list, unnecessary APs may be removed from the AP list. The following explains how to select APs to include in the AP list, etc., with reference to the figures.

[0026] Figure 3 is a sequence diagram showing the flow of a series of processes in the wireless communication method according to this embodiment. Referring to this figure, the flow of a series of processes in the wireless communication method implemented using the wireless communication system 1 described above will be explained.

[0027] (Step S11) First, the RIC performs the initial setup of the AP list. The initial setup of the AP list is performed, for example, when at least one of the RIC or DU restarts (including when it is newly deployed) or when a new AP is added.

[0028] [Initial settings for the AP list] There are several possible methods for initializing the AP list. Below is an example of how to initialize the AP list. Note that the following examples can be combined.

[0029] One possible method for initializing the AP list is to reuse the previous AP list. Specifically, when the RIC or DU restarts, the AP list is stored in the ROM (Read Only Memory) area, and the same AP list is referenced after the restart. By reusing the previously used AP list, the time it takes for the APs included in the AP list to stabilize (converge) can be shortened. However, this first method cannot handle situations such as the initial startup or when it is necessary to reset the AP list itself due to a problem with the AP list. In such cases, it should be executed in combination with the following method.

[0030] A second method for initializing the AP list is to randomly select a certain number of APs. This method can be used even without information on previous processing or the local wireless environment. The certain number is selected within the allowable processing load of the DU while ensuring wireless communication quality, and may be in the range of 2 to 5, for example. A specific method for calculating the certain number may be the value obtained by dividing the area covered by the DU by the area covered by one AP (rounded to the nearest whole number). The area covered by one AP may be estimated by estimating the communication distance at which a predetermined received signal level is achieved through line design, etc. Note that the area covered by one AP will be concentric circles of the communication distance for an omnidirectional antenna, and a sector in the direction of direction for a directional antenna. In this way, by randomly selecting APs, the area covered by the DU can be covered without gaps. In other words, it becomes possible to respond no matter where the UE is located within the area covered by the DU.

[0031] A third method for initializing the AP list is to allow users to manually select APs. For example, by utilizing the expertise of area design personnel to select APs, the initial setup can reflect the placement of APs in accordance with surrounding buildings and other structures, thus preventing the selection of APs that are not geographically suitable. This method can also shorten the time it takes for the APs included in the AP list to stabilize (converge).

[0032] A fourth method for initializing the AP list is to include all APs connected as subordinate nodes of the DU in the AP list. This method can be adopted even without information on previous processing or the local wireless environment. Even if all APs are selected only on the first run, the number of APs included in the AP list can be reduced by dynamic control, thus reducing the processing load on the DU in a static state.

[0033] (Step S12) Next, the RIC sends the created AP list (RACH AP list shown in the diagram) to the DU. For the purposes of the following explanation, in this example, the AP list will be assumed to include AP0 and AP2.

[0034] Note that the message used to notify the RIC of the AP list to the DU is not defined in the current O-RAN specification. An example of the specification for this message is described below.

[0035] [Example of message specification in step S12] The AP list transmitted in step S12 identifies one or more APs that perform the RACH Preamble detection process. As described above, the AP list only needs to identify one or more APs present in nodes below the DU, and may identify multiple APs. Alternatively, it may identify all APs present in nodes below the DU.

[0036] The information elements include at least information about an identifier that identifies the AP, etc. Note that this identifier does not necessarily have to identify the AP itself. Specifically, this embodiment is not limited to AP-level control, but can be implemented at various units, such as beam units during beamforming. Specifically, in addition to identifying the AP, it is possible to identify DU, gNB (gNodeB), antenna port, beam, etc. A detailed example of the identifier will be described later with reference to Figures 5 to 12.

[0037] The message notification timing may include the initial startup or restart of devices such as RIC, DU, and AP. A message will also be sent when the AP list is updated by the RIC.

[0038] Specific examples of interfaces include the E2:REPORT service and the E2:INSERT service. The interface for notifying the RIC of the AP list to the DU can also be considered part of the E2 interface between the DU and the RIC.

[0039] (Step S13) Next, the DU configures the APs included in the AP list to periodically transmit SSB (SS / PBCH Block). In this embodiment, the AP list includes AP0 and AP2, so as shown in the figure, the DU causes AP0 and AP2 to periodically transmit SSB.

[0040] (Step S14) Next, the DU receives RACH Preamble(Msg1) via the APs included in the AP list. In this embodiment, the AP list includes AP0 and AP2, so as shown in the figure, the DU receives RACH Preamble(Msg1) via AP0 and AP2.

[0041] (Step S15) Next, the DU synthesizes the signals received through the APs included in the AP list. Diversity reception techniques, for example, may be used for signal synthesis. Maximum ratio synthesis may be performed as an example.

[0042] (Step S16) Next, the DU detects the RACH Preamble based on the AP list notified by the RIC in step S12 and determines whether the detection was successful. Successful detection may be defined as the received strength of the RACH Preamble sent from the UE being above a predetermined threshold. For example, if the quality of the combined signal satisfies the detection conditions, detection may be considered successful. If detection is successful, the AP list is not updated and the process ends (Step S16; YES). If detection fails, the process proceeds to step S17 in order to update the AP list (Step S16; NO).

[0043] (Step S17) If detection fails, the DU notifies the RIC of a RACH Preamble Detection Failure.

[0044] Note that the message used by the DU to notify the RIC of a RACH Preamble Detection Failure is not defined in the current O-RAN specification. An example of the specification of such a message is described below.

[0045] [Example of message specification in step S17] The information elements include at least one of the following: quality information for each AP included in the AP list, and quality information after synthesis. Specifically, quality information refers to information indicating reception quality, and may include, for example, reference signal received power (RSRP) or signal-noise ratio (SNR). The interface notified from the DU to the RIC when RACH Preamble detection fails may also include at least the reception quality for each of the multiple APs. Furthermore, the interface notified from the DU to the RIC when RACH Preamble detection fails may also include the reception quality for the synthesized AP.

[0046] The timing for sending the message is when the detection of the RACH Preamble fails in step S16. While it is also possible to send a message upon success, it is preferable to send the message only upon failure to avoid straining the control lines.

[0047] Specific examples of interfaces include E2:REPORT service, E2:Performance Measurement, and O1:Performance Measurement. In other words, the interface to which the RIC is notified when RACH Preamble detection fails can be the E2 interface or the O1 interface between the DU and the RIC.

[0048] (Step S18) Next, the RIC updates the AP list. The AP list is updated by referring to the information received in step S17 and the current AP list. A specific example of how to update the AP list will be explained below.

[0049] [Dynamic control of AP list] If detection failures occur frequently, the RIC will add a new AP to the AP list. The RIC may also replace APs by deleting unnecessary APs at the same time as adding an AP, or during subsequent updates. Frequent detection failures refer to multiple consecutive occurrences, and the number of occurrences can be arbitrarily changed. If there is one or two successes among a series of failures, the success may be ignored and treated as multiple consecutive failures.

[0050] Specifically, the RIC selects which APs to remove or add by referring to the AP quality information included in the RACH Preamble Detection Failure in step S17.

[0051] More specifically, the RIC (Remote Control Unit) refers to the quality information of APs (Access Points), and if any APs have quality information below a predetermined threshold, it removes those APs from the AP list. Simultaneously with the removal, it considers APs located close to the removed AP as candidates for addition to the AP list. The determination of proximity may be based on the AP's latitude and longitude information.

[0052] The threshold can be set using either an absolute value or a relative value. Alternatively, a combination of absolute and relative values ​​may be used. An example of an absolute value setting might be -100 dBm, while an example of a relative value setting might be 30 dB or more lower than the maximum received level at the AP.

[0053] If no APs have quality information below the threshold, select an AP that is not included in the AP list and add it to the AP list. The selection of APs not included in the AP list may be, for example, random.

[0054] Furthermore, if detection successes continue, the RIC may remove any AP from the AP list. Since continued detection successes suggest that a sufficient number of APs have been selected, removing an AP from the AP list aims to further reduce the processing load on the DU. For example, the RIC selects the AP to remove by referring to the AP cluster information of the UEs it manages.

[0055] Specifically, if there are multiple access points (APs) located close to each other, the RIC may remove one of the APs from the AP list. Also, if there is an AP that is not included in any AP cluster, the RIC may remove that AP from the AP list.

[0056] [Multihoming AP] Figure 4 is a diagram illustrating an example of a wireless communication system according to this embodiment in which a multihoming AP is prioritized. This figure is a schematic diagram illustrating a multihoming AP and its handling. The explanation of the multihoming AP and its handling will be given with reference to this figure.

[0057] The figure shows an example where DU1 and DU2 are connected as subordinate nodes of RIC. The figure also shows multiple distributed APs. APs located within geographical range AR1 are connected to DU1. APs located within geographical range AR2 are connected to DU2. Here, ranges AR1 and AR2 overlap. APs located within overlapping ranges can be multihoming APs. In other words, a multihoming AP can be defined as an AP located at the boundary of multiple DUs. Such a multihoming AP is connected to multiple DUs. In the example shown, the multihoming AP is connected to both DU1 and DU2.

[0058] When a multihoming AP exists, the RIC may prioritize adding it to the AP list when reversing the AP list. This is because multihoming APs are connected to multiple DUs, making it easier to reduce the impact of interference.

[0059] [Functional Configuration] Let's look at an example of a specific functional configuration for performing the processing described above, again referring to Figure 1.

[0060] The AP list is stored in the storage unit 12 of the communication control device 10. The AP list is a list that identifies one or more APs that perform the RACH Preamble detection process. The storage unit 12 can also store the AP list. The storage unit 12 may also store a list of APs that the DU failed to detect from among the APs identified by the AP list. The list of APs that the DU failed to detect is updated in response to receiving the message in step S17 described above.

[0061] If the control unit 11 receives notification from the DU that it failed to detect a RACH Preamble based on the AP list, it updates the AP list. Specifically, the control unit 11 may update the AP list by referring to the AP cluster of the UE in communication and, if the list contains APs that can be recognized by multiple UEs, by removing one of them from the list.

[0062] Furthermore, the control unit 11 adds neighboring APs to the AP list from the list of APs that failed to be detected, based on the information stored in the memory unit 12. Neighboring APs may be identified based on latitude and longitude.

[0063] Furthermore, the control unit 11 prioritizes adding multihoming APs during the AP list update process. Whether or not an AP is a multihoming AP may be stored, for example, in the storage unit 12.

[0064] [Example of an identifier] Next, with reference to Figures 5 through 12, we will explain an example of an identifier used to identify devices such as APs in an AP list.

[0065] Figure 5 is the first diagram showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example in which a device is identified by the AP ID. In the illustrated example, two APs, AP#0 and AP#1, are connected to the DU. For example, any device can be specified by using the AP ID, such as AP#0 or AP#1, in the AP list.

[0066] Figure 6 is a second diagram showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example of identifying a device by combining the AP ID and the antenna port ID. In the illustrated example, two APs, AP#0 and AP#1, are connected to the DU. Each AP has port #0 and port #1. In the illustrated example, the port IDs of each AP are port #0 and port #1, and are common to both. In such a case, any device can be specified by using a combination of the AP ID and the antenna port ID, for example, port #0 of AP#0 or port #1 of AP#1 in the AP list.

[0067] Figure 7 is a third diagram showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example in which a device is identified by the antenna port ID. In the illustrated example, two APs are connected to the DU. Each AP has multiple ports. In the illustrated example, the first AP has ports #0 and #1. The second AP has ports #2 and #3. Thus, in the illustrated example, the port IDs of each AP are different from each other. In such a case, for example, any device can be specified (without specifying the AP) by the antenna port ID, such as port #0 or port #3, in the AP list.

[0068] Figure 8 is a fourth diagram showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example of identifying a device by a combination of the AP ID and the beam ID. In the illustrated example, two APs, AP#0 and AP#1, are connected to the DU. Each AP can transmit beam #0 and beam #1 by beamforming. In the illustrated example, the beam IDs that each AP can transmit are beam #0 and beam #1, and are common to both. In such a case, any device can be specified by using a combination of the AP ID and the beam ID, for example, beam #0 for AP#0 or beam #1 for AP#1 in the AP list.

[0069] Figure 9 is the fifth figure showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example of identifying a device by beam ID. In the illustrated example, two APs are connected to the DU. Each AP can transmit multiple beams by beamforming. In the illustrated example, the beam IDs that the first AP can transmit are beam #0 and beam #1. The beam IDs that the second AP can transmit are beam #2 and beam #3. Thus, in the illustrated example, the beam IDs that each AP can transmit are different from each other. In such a case, for example, in the AP list, any device can be specified by beam ID, such as beam #0 or beam #3 (without specifying the AP).

[0070] Figure 10 is the sixth figure showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example in which a device is identified by the AP ID, antenna port ID, and beam ID. In the illustrated example, two APs, AP#0 and AP#1, are connected to the DU. Each AP has port #0 and port #1 (although not shown, the upper row is port #0 and the lower row is port #1). Furthermore, each antenna port can transmit beam #0 and beam #1 by beamforming. In the illustrated example, the port IDs of each AP are port #0 and port #1, and are common to both. Furthermore, the beam IDs that each antenna port can transmit are beam #0 and beam #1, and are common to both. In such a case, any device can be specified by using a combination of the AP ID, antenna port ID, and beam ID, for example, beam #0 of port #0 of AP#0, or beam #1 of port #1 of AP#1, in the AP list.

[0071] Figure 11 is the seventh figure showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example of identifying a device by combining the ID of the DU and the ID of the AP. In the illustrated example, two DUs, DU#1 and DU#2, are connected to the RIC. Each DU is also connected to AP#0 and AP#1. In the illustrated example, the IDs of the APs connected to each DU are AP#0 and AP#1, and are common to both. In such a case, any device can be specified by using a combination of the ID of the DU and the ID of the AP, for example, AP#0 for DU#1 or AP#0 for DU#2, in the AP list.

[0072] Figure 12 is the eighth figure showing an example of an identifier for identifying a device in the wireless communication system according to this embodiment. The figure shows an example of identifying a device by combining the ID of a gNB (gNodeB) and the ID of an AP. In the illustrated example, two gNBs, gNB#1 and gNB#2, are connected to the RIC. Each gNB is also connected to AP#0 and AP#1. In the illustrated example, the IDs of the APs connected to each gNB are AP#0 and AP#1, and are common to both. In such a case, any device can be specified by using a combination of the gNB ID and the AP ID, for example, AP#0 for gNB#1 or AP#0 for gNB#2, in the AP list.

[0073] Figure 13 is a block diagram showing an example of the internal configuration of a communication control device according to this embodiment. At least some of the functions of the communication control device 10 can be realized using a computer. As shown in the figure, the computer is composed of a central processing unit 901, RAM 902, input / output ports 903, input / output devices 904 and 905, etc., and a bus 906. The computer itself can be realized using existing technology. The central processing unit 901 executes instructions contained in programs read from RAM 902, etc. The central processing unit 901 writes data to RAM 902, reads data from RAM 902, and performs arithmetic and logical operations according to each instruction. RAM 902 stores data and programs. Each element contained in RAM 902 has an address and can be accessed using that address. RAM stands for "Random Access Memory". Input / output ports 903 are ports for the central processing unit 901 to exchange data with external input / output devices, etc. Input / output devices 904 and 905 are input / output devices. Input / output devices 904 and 905 exchange data with the central processing unit 901 via input / output ports 903. Bus 906 is a common communication channel used within the computer. For example, the central processing unit 901 reads and writes data to RAM 902 via bus 906. Also, for example, the central processing unit 901 accesses input / output ports via bus 906. Furthermore, all or part of the functional units of the communication control device 10 may be implemented using hardware such as ASICs, PLDs, or FPGAs. Furthermore, all or part of the functional units may be implemented by a combination of software and hardware.

[0074] [Summary of Embodiments] According to the embodiment described above, the wireless communication system 1 is a self-free wireless communication system that reduces the effects of interference by using a plurality of distributed APs, a DU, and an RIC. The wireless communication system 1 includes an interface (step S12 described above) that notifies the DU of an AP list, which is a list that identifies one or more APs that perform RACH Preamble detection processing. By providing such an interface, the RIC can select APs that perform RACH processing. According to this embodiment, by being able to select APs that perform RACH processing, the load on higher-level nodes (e.g., DUs) can be reduced.

[0075] Furthermore, according to this embodiment, the DU further includes an interface (step S17 described above) that detects RACH Preambles based on the notified AP list and notifies the RIC if detection fails. By adopting such a configuration, the RIC can obtain information regarding the reception quality between the APs and UEs present in the AP list. Therefore, the RIC can select a suitable AP for which RACH processing should be performed. According to this embodiment, by being able to select a suitable AP for which RACH processing should be performed, the load on higher-level nodes (e.g., the DU) can be reduced.

[0076] Furthermore, according to this embodiment, the interface to which the RIC is notified from the DU when the detection of the RACH Preamble fails (step S17 described above) includes at least the reception quality for each of the multiple APs. In other words, the RIC can obtain information on the reception quality for each of the multiple APs present in the AP list. Therefore, the RIC can accurately select the most suitable AP for which RACH processing should be performed. According to this embodiment, by being able to accurately select the most suitable AP for which RACH processing should be performed, the load on the higher-level node (e.g., the DU) can be reduced.

[0077] Furthermore, according to this embodiment, the interface to which the RIC is notified from the DU when the detection of the RACH Preamble fails (step S17 described above) also includes the reception quality of the synthesized AP. Therefore, the RIC can determine how many APs should be added based on the reception quality of the synthesized AP. Thus, the RIC can accurately select suitable APs for which RACH processing should be performed. According to this embodiment, by being able to accurately select suitable APs for which RACH processing should be performed, the load on higher-level nodes (e.g., DUs) can be reduced.

[0078] Furthermore, according to this embodiment, the interface that notifies the RIC of the RACH AP list to the DU (step S12 described above) is specifically included in the E2 interface between the DU and the RIC. Moreover, the interface to which the DU notifies the RIC when detection of the RACH Preamble fails (step S17 described above) is specifically included in the E2 interface or the O1 interface between the DU and the RIC. Therefore, this embodiment can be implemented using an existing O-RAN architecture.

[0079] Furthermore, according to this embodiment, the communication control device 10 communicates information with a DU located in a self-free wireless communication system that reduces the effects of interference by using a plurality of distributed APs. The communication control device 10 may be, for example, a RIC. The communication control device 10 comprises a control unit 11 and a storage unit 12. The control unit 11 stores a RACH AP list, which is a list that identifies one or more APs that perform RACH Preamble detection processing. If the control unit 11 is notified by the DU that detection of RACH Preamble failed as a result of detecting it based on the RACH AP list, it updates the RACH AP list. By adopting such a configuration, the communication control device 10 can select APs that perform RACH processing. According to this embodiment, by being able to select APs that perform RACH processing, the load on higher-level nodes (e.g., DUs) can be reduced.

[0080] Furthermore, according to this embodiment, the control unit 11 refers to the AP cluster of the UE in communication and, if the list contains APs that can be recognized by multiple UEs, updates the RACH AP list by removing one of them from the list. By adopting this configuration, the communication control device 10 can reduce the number of APs that perform RACH Preamble detection. Therefore, according to this embodiment, the load on the higher-level node (e.g., DU) can be reduced.

[0081] Furthermore, according to this embodiment, the storage unit 12 also stores a list of APs that failed to be detected. The control unit 11 updates the RACH AP list by adding neighboring APs to the list of APs that failed to be detected stored in the storage unit 12. By adopting this configuration, it becomes possible to add APs that are likely to improve reception quality to the AP list.

[0082] Furthermore, according to this embodiment, the communication control device 10 communicates information with multiple DUs. The control unit 11 prioritizes adding multihoming APs that are located at the boundary of multiple DUs and connected to multiple DUs to the AP list. By adopting this configuration, it becomes possible to add APs (specifically multihoming APs) that are likely to have high reception quality to the AP list.

[0083] Furthermore, the above-described embodiment makes it possible to dynamically establish optimal information communication by considering the relative positional relationship between the UE and the AP. In addition, according to this embodiment, it is possible to select the AP that performs RACH processing, thereby reducing the processing load on the DU. Therefore, according to this embodiment, it is possible to contribute to Goal 9 of the United Nations Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0084] Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like are also included within the scope of the gist of the present invention.

[0085] Alternatively, computer programs for realizing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the programs recorded on this recording medium may be loaded into a computer system and executed. Note that the term "computer system" here may include hardware such as an operating system and peripheral devices. Furthermore, "computer-readable recording media" refers to writable non-volatile memory such as flexible disks, magneto-optical disks, ROMs, and flash memory, portable media such as DVDs (Digital Versatile Discs), and storage devices such as hard disks built into computer systems.

[0086] Furthermore, "computer-readable recording media" includes volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within computer systems that act as servers or clients when programs are transmitted via networks such as the Internet or communication lines such as telephone lines, which retain programs for a certain period of time. The program may also be transmitted from the computer system storing it in a memory device to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may also be intended to implement only a part of the aforementioned functions. Furthermore, it may be a so-called differential file (differential program) that can implement the aforementioned functions in combination with a program already recorded in the computer system. [Explanation of Symbols]

[0087] 1... Wireless communication system, 10... Communication control device, 11... Control unit, 12... Memory unit

Claims

1. A communication control device that communicates information with a Distributed Unit (DU) located in a self-free wireless communication system that uses multiple distributed APs to reduce the effects of interference, A storage unit that stores a RACH AP list, which is a list that identifies one or more APs that perform detection processing for RACH (Random Access Channel) Preamble, If the DU notifies that detection of RACH Preamble failed based on the RACH AP list, the control unit performs an update process on the RACH AP list. A communication control device equipped with the following features.

2. The control unit refers to the AP cluster of the UE (User Equipment) in communication, and if the list contains APs that can be recognized by multiple UEs, it updates the RACH AP list by removing one of them from the list. The communication control device according to claim 1.

3. The aforementioned storage unit further stores a list of APs that failed to be detected. The control unit updates the RACH AP list by adding neighboring APs to the APs shown in the list of APs that failed to be detected, which is stored in the storage unit. A communication control device according to claim 1 or claim 2.

4. A communication control device that communicates information with multiple DUs, The control unit performs the update process of the RACH AP list by preferentially adding multihoming APs that are located at the boundaries of multiple DUs and connected to multiple DUs. A communication control device according to claim 1 or claim 2.

5. A communication control method for communicating information with a Distributed Unit (DU) located in a self-free wireless communication system that uses multiple distributed APs to reduce the effects of interference, A storage step of storing a RACH AP list, which is a list that identifies one or more APs that perform detection processing for RACH (Random Access Channel) Preamble, If the DU notifies that detection of RACH Preamble failed based on the RACH AP list, the control process updates the RACH AP list. A communication control method having

6. On the computer, A program that enables information communication with a Distributed Unit (DU) located in a self-free wireless communication system that uses multiple distributed APs to reduce the effects of interference, A storage step of storing a RACH AP list, which is a list that identifies one or more APs that perform detection processing for RACH (Random Access Channel) Preamble, If the DU notifies that detection of RACH Preamble failed based on the RACH AP list, the control step includes updating the RACH AP list. A program that executes the command.

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