Processing apparatus of a self-free communication system, method and program executed by the processing apparatus

Abstract

To appropriately feedback channel state information by WD.SOLUTION: A method executed by a processing device of a cell-free communication system having a plurality of access points (APs) includes transmitting measurement information to a wireless device via a master AP among one or more APs included in a cluster associated with the wireless device among the plurality of APs, for the wireless device to determine a measurement target AP for which the wireless device measures a channel state, and receiving channel state information indicating the channel state with the measurement target AP via the master AP in response to the measurement information.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a self - contained communication system.

Background Art

[0002] A cellular communication system provides services by dividing a service - providing area into a plurality of cells and arranging base stations in each cell. In a cellular communication system, a wireless device (WD), also called a user equipment (UE), communicates with the base station of the cell in which the WD is located. In a cellular communication system, due to power attenuation of radio waves from the base station and interference from neighboring cells, the communication quality in the boundary region of the cell tends to deteriorate.

[0003] For this reason, Non - Patent Document 1 discloses a self - contained communication system. Also in a self - contained communication system, similar to a cellular communication system, a plurality of access points (APs) are arranged at various geographical locations. The plurality of APs are connected to a central processing unit (CPU) via transmission lines. In a self - contained communication system, for example, the CPU selects one or more APs with which the WD communicates wirelessly from among the plurality of APs. The WD communicates with the CPU via the one or more APs by transmitting and receiving wireless signals with the one or more APs selected by the CPU.

[0004] In a self - contained communication system, there is no concept of a conventional "cell", and one or more APs that communicate with a WD are dynamically controlled by the CPU for each WD. This set of one or more APs that communicate with a WD is also called the "cluster" of the WD or the "cluster" associated with the WD.

[0005] Non - Patent Document 2 discloses a cluster formation process for forming a cluster of a WD when the WD makes an initial access to a self - contained communication system. Further, Non - Patent Document 2 also discloses setting an upper limit on the number of WDs that one AP can communicate with in order to reduce the processing load on the CPU. In other words, Non - Patent Document 2 discloses setting an upper limit on the number of clusters to which one AP can belong.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order for the CPU to dynamically control the clusters of each WD, the WD needs to measure the channel state with each AP and feedback channel state information indicating the measured channel state to the CPU. However, in a configuration where the WD feedbacks the channel state with all APs capable of receiving wireless signals to the CPU, the processing loads of the CPU and the WD increase. On the other hand, if the number of APs whose channel states are feedback by the WD is insufficient, the cluster of the WD cannot be configured appropriately.

[0008] This disclosure provides a technique for appropriately feedbacking channel state information by the WD.

Means for Solving the Problems

[0009] According to one aspect of the present disclosure, a method executed by a processing device of a cell-free communication system including a plurality of access points (APs) includes transmitting, via a master AP among one or more APs included in a cluster associated with a wireless device among the plurality of APs, measurement information for the wireless device to determine a measurement target AP through which the wireless device measures a channel state; and receiving, as a response to the measurement information, channel state information indicating the channel state with the measurement target AP via the master AP.

Advantages of the Invention

[0010] According to the present disclosure, it is possible to appropriately perform feedback of channel state information by a WD.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential for the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined. Also, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0013] FIG. 1 is a configuration diagram of a self-free communication system used in the description of the embodiment. In FIG. 1, the self-free communication system has a plurality of APs 1-1 to 1-10. In the following description, when there is no need to distinguish between APs 1-1 to 1-10, they are denoted as AP1. In FIG. 1, the number of APs 1 is 10 as an example, but the number of APs 1 in the self-free communication system is not limited to 10. Each AP1 is connected by a wired and / or wireless communication link to a CPU 3. Further, the CPU 3 is connected to a core network (not shown). Note that in FIG. 1, for the sake of simplicity of the figure, the communication links connecting each AP1 and the CPU 3 are omitted. Also, in FIG. 1, only one CPU 3 is shown, but a plurality of CPU 3s may be arranged in the self-free communication system. In the self-free communication system, one AP1 may be connected to one or a plurality of CPU 3s.

[0014] Also, in FIG. 1, two WDs 2-1 and 2-2 are shown. In the following description, when there is no need to distinguish between WDs 2-1 and 2-2, they are denoted as WD2. APs 1-1 to 1-3 and 1-5 within the solid-line circle in FIG. 1 are the cluster 4-1 of WD2-1. Also, APs 1-5, 1-7, and 1-10 within the dotted-line circle in FIG. 1 are the cluster 4-2 of WD2-2. Therefore, WD2-1 communicates wirelessly with APs 1-1 to 1-3 and 1-5 included in the cluster 4-1, and communicates with the CPU 3 via APs 1-1 to 1-3 and 1-5. Similarly, WD2-2 communicates wirelessly with APs 1-5, 1-7, and 1-10 included in the cluster 4-2, and communicates with the CPU 3 via APs 1-5, 1-7, and 1-10.

[0015] One master AP is set for each cluster of each WD2 by the CPU 3. In FIG. 1, the master AP of the cluster 4-1 of WD2-1 is AP1-1. Similarly, one of the three APs 1 within the cluster 4-2 of WD2-2 is selected as the master AP by the CPU 3. Note that in FIG. 1, only two WDs 2 are shown as an example, but the number of WDs 2 receiving service by the self-free communication system is not limited to 2.

[0016] Hereinafter, the communication sequence according to this embodiment will be described with reference to FIG. 2. At the start time of FIG. 2, it is assumed that WD2-1 is in an idle state. WD2-1 first selects one AP1 from a plurality of AP1s in the self-free communication system and transmits an initial access signal to the selected AP1 at S1. In FIG. 2, it is assumed that AP1-1 is selected. For example, WD2-1 measures the reference signals transmitted by each AP1 and performs initial access to the AP1 with the best quality of the received reference signal. The initial access signal can be, for example, a random access signal defined by 3GPP (registered trademark). The AP1-1 that has received the initial access signal transmits the initial access signal to the CPU3 at S2.

[0017] Thereafter, WD2-1 and the CPU3 exchange initial information via AP1-1 at S3. The initial information includes information necessary for the CPU3 to configure the cluster of WD2-1. For example, the initial information includes channel state information indicating the channel state between each AP1 measured based on the reference signals received by WD2-1 from each AP1. The CPU3 forms a cluster 4-1 (FIG. 1) associated with WD2-1 based on the initial information at S4. That is, the CPU3 selects the AP1 to be used for communicating with WD2-1 at S4. At this time, the CPU3 determines the master AP of WD2-1 from the AP1s in the cluster 4-1. In this example, in the cluster formation at the time of initial access, it is assumed that the CPU3 selects the AP1 to which WD2 has performed initial access as the master AP. Therefore, in this example, AP1-1 is selected as the master AP of WD2-1. Although not shown in FIG. 2, the CPU3 communicates with WD2-1 via the AP1s in the cluster 4-1.

[0018] The CPU3 transmits, at S5, measurement information for WD2-1 to determine the AP1 (hereinafter referred to as the measurement target AP1) for which WD2-1 should measure the channel state to the master AP (AP1-1) of WD2-1. The master AP (AP1-1) notifies WD2-1 of the measurement information at S6.

[0019] WD2-1 measures the channel state with the target AP1 according to the measurement information, and in S7, transmits the measurement result to the master AP (AP1-1). The measurement result includes channel state information indicating the channel state with the target AP1. The master AP, AP1-1, transmits the measurement result to the CPU3 in S8. The CPU3 can schedule the data transmitted and received with WD2-1 based on the measurement result. Also, the CPU3 determines whether it is necessary to change the cluster of WD2-1 based on the measurement result, and can change the cluster of WD2-1 if necessary.

[0020] Note that the master AP of WD2-1 can be changed when changing the cluster of WD2-1. Alternatively, the master AP of WD2-1 can be changed when the master AP leaves the cluster of WD2-1. The CPU3 repeats the processes of S5 to S8 until WD2-1 enters the idle state.

[0021] Hereinafter, the target AP1 will be described. First, the CPU3 can set only the AP1 included in the current cluster 4-1 of WD2-1 as the target AP1.

[0022] Also, in addition to or instead of the AP1 included in the current cluster 4-1 of WD2-1, the CPU3 can set the neighboring AP1 as the target AP1. The neighboring AP1 is an AP1 that satisfies a predetermined condition among the AP1s not included in the cluster 4-1. The predetermined condition can be an AP1 whose distance from the AP1s included in the cluster 4-1 is within a predetermined value. For example, in the example of FIG. 1, in addition to or instead of AP1-1 to 1-3 and 1-5 included in the cluster 4-1, AP1-4 and AP1-6 to AP1-8, which are not included in the cluster 4-1 but whose distance from any of AP1-1 to 1-3 and 1-5 is within the predetermined value, can be included as the neighboring AP1 in the target AP1. By setting the neighboring AP1 as the target AP1, the CPU3 can appropriately control the cluster according to the movement of WD2-1.

[0023] The CPU 3 can include all of the neighboring APs 1 in the measurement target AP 1. Alternatively, the CPU 3 can narrow down the APs 1 to be included in the measurement target AP 1 from among the neighboring APs 1. For example, when WD2-1 is moving in the direction of the arrow in Fig. 1, the CPU 3 can include only AP1-7 and AP1-8, among the neighboring APs 1 which are AP1-4 and AP1-6 to AP1-8, whose distance from WD2-1 becomes shorter with time, in the measurement target AP 1. By narrowing down the neighboring APs 1 to be included in the measurement target AP 1 in consideration of the moving direction of WD2-1, the CPU 3 can acquire the channel state information for appropriately controlling the cluster while suppressing the processing loads of WD2 and the CPU 3. Note that the CPU 3 can receive the change in the position of WD2-1 from WD2-1. Also, the CPU 3 can determine the change in the position of WD2-1 by repeatedly acquiring from the relevant AP 1 the intensity of the radio signal received by the AP 1 included in the cluster 4-1 of WD2-1 from WD2-1.

[0024] Furthermore, when the number of connectable WD2s is set in the AP 1, the CPU 3 can be configured to include only the neighboring APs 1 with available space in the number of connectable WD2s in the measurement target AP 1. For example, assume that AP1-7 has also been selected for a cluster of WD2s (not shown) in addition to WD2-2, and thus the number of WD2s that AP1-7 can connect to has reached the upper limit set for AP1-7. In this case, the CPU 3 will include the neighboring APs 1 other than AP1-7 in the measurement target AP 1. Also, when considering the moving direction of WD2-1, the CPU 3 will include only AP1-8 in the measurement target AP 1. Note that the CPU 3 includes the identifier of the measurement target AP 1 in the measurement information.

[0025] Further, the measurement information is not limited to directly indicating the measurement target AP1, and can be configured to specify selection conditions for the WD2 to select the measurement target AP1. For example, the CPU3 can transmit measurement information including the number N of APs 1 reporting channel state information as a selection condition. In this case, WD2-1 reports the top N pieces of channel state information with good received signal quality to the CPU3 together with the identifier of the AP1. Note that the signal quality is determined based on the reference signal transmitted by each AP1. Alternatively, WD2-1 reports the top N pieces of channel state information with strong received signal strength to the CPU3 together with the identifier of the AP1.

[0026] Further, the CPU3 can transmit measurement information including a threshold as a selection condition. In this case, WD2-1 reports to the CPU3 the channel state of the AP1 with the best received signal quality and the channel state of the AP1 whose signal quality degradation degree with respect to the AP1 with the best signal quality is within the notified threshold, together with the identifier of the AP1. Alternatively, WD2-1 reports to the CPU3 the channel state of the AP1 with the strongest received signal strength and the channel state of the AP1 whose signal strength decrease degree with respect to the AP1 with the strongest signal strength is within the notified threshold, together with the identifier of the AP1.

[0027] Further, the CPU3 can transmit measurement information including selection conditions such as reporting the channel state of the AP1 whose received signal strength increases over time or the AP1 whose signal quality increases over time. For example, the CPU3 can specify to WD2-1 to report the channel state of the AP1 whose signal strength or signal quality has increased by a predetermined value compared to the previous channel state measurement. By acquiring the channel state of the AP1 whose received signal strength or signal quality increases over time, the CPU3 can appropriately determine the AP1 to be added to the cluster 4-1 of WD2-1.

[0028] In addition, the CPU 3 can transmit measurement information including selection conditions such as reporting the channel state of the AP 1 whose received signal strength weakens over time or the channel state of the AP 1 whose signal quality deteriorates over time. For example, the CPU 3 can specify to the WD2-1 to report the channel state of the AP 1 whose signal strength or signal quality is weaker or lower than a predetermined value compared to the previous channel state measurement. By acquiring the channel state of the AP 1 whose received signal strength or signal quality weakens or deteriorates over time, the CPU 3 can appropriately determine the AP 1 to be excluded from the cluster 4-1 of the WD2-1.

[0029] Note that the CPU 3 repeatedly transmits the measurement information to the WD2-1 (S5 in FIG. 2), but the content of the measurement information can be made different for each transmission. For example, after transmitting measurement information with only the AP 1 included in the current cluster 4-1 as the measurement target AP 1, in the next measurement information, measurement information including the neighboring AP 1 as the measurement target AP 1 can be transmitted. Furthermore, the next measurement information can be measurement information indicating selection conditions instead of measurement information directly indicating the measurement target AP 1 by an identifier. That is, the CPU 3 can specify the AP 1 for which the channel state is acquired to be different in each transmission of the measurement information.

[0030] In this way, by the CPU 3 transmitting the measurement information for determining the AP 1 for which the channel state is acquired to the WD2, the CPU 3 can acquire only the channel state with the necessary AP 1, and the processing load of the CPU 3 can be reduced. Also, since the WD2 no longer needs to always measure and report the channel state with all the AP 1s, the processing load of the WD2 can also be reduced.

[0031] FIG. 3 is a configuration diagram of the processing device 5 according to the present embodiment. The processing device 5 can be implemented, for example, in the CPU 3. The processing device 5 includes one or more processors 50 and one or more non-temporary memory devices 51 that store a computer program. The one or more memory devices 51 are computer-readable storage media. When the computer program is executed by the one or more processors 50, it includes instructions to cause the one or more processors 50 to execute the processing in the CPU 3 described in FIG. 2.

[0032] In addition, the processing device 5 includes a database unit 52. The database unit 52 is a database that indicates the arrangement positions of the respective APs 1 of the self-free communication system. Also, when an upper limit value of the number of WDs 1 that can communicate with each AP 1 is set, the database unit 52 also stores the upper limit value of each AP 1. Note that the present disclosure is not limited to the configuration in which the processing device 5 has the database unit 52. For example, the database unit 52 can be provided in an external device that can be accessed by the processing device 5 via a network.

[0033] FIG. 4 shows functional blocks realized in the processing device 5 when one or more processors 50 execute a computer program stored in one or more memory devices 51. As shown in FIG. 4, the one or more processors 50 function as a measurement information generation unit 55 and a processing unit 56.

[0034] The measurement information generation unit 55 generates the measurement information to be transmitted in S5 of FIG. 2. As described above, the measurement information may include an identifier for identifying the measurement target AP 1. Also, as described above, the measurement information may include selection conditions for the WD 1 to select the measurement target AP 1. When the processing unit 56 acquires a measurement result from the WD 2 as a response to the measurement information, it performs operations such as changing the cluster and scheduling data transmission with the WD 1 based on the channel state information with the AP 1 included in the measurement result.

[0035] Furthermore, according to the present disclosure, a program executable by one or more processors is provided. When the program is executed by one or more processors of the device, the program includes instructions for causing the device to function as, for example, the processing device 5. Furthermore, according to the present disclosure, a non-transitory computer-readable storage medium storing the above program is provided. Furthermore, according to the present disclosure, a method executed by the processing device 5 is provided in accordance with the content described in FIG. 2. Furthermore, according to the present disclosure, a program for causing the method to be executed by a device having one or more processors and a non-transitory computer-readable storage medium storing the program are provided.

[0036] The invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the gist of the invention.

[0037] With the above configuration, it is possible to appropriately feedback the channel state information by the WD. Therefore, it becomes possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Build resilient infrastructure, promote sustainable industrialization, and foster innovation."

Description of Reference Numerals

[0038] 55: Measurement information generation unit, 56: Processing unit

Claims

1. 1. A method executed by a processor in a cell-free communication system having a plurality of access points (APs), comprising: transmitting, to the wireless device, measurement information for the wireless device to determine a measurement target AP for measuring a channel state of the wireless device via a master AP among one or more APs included in a cluster associated with the wireless device among the plurality of APs; receiving, as a response to the measurement information, channel state information indicating the channel state between the AP and the measurement target AP via the master AP; A method comprising:

2. 2. The method of claim 1 , The method, wherein the measurement information includes an identifier of the measured AP.

3. 3. The method of claim 2, The method, wherein the measurement target APs include the one or more APs included in the cluster.

4. 3. The method of claim 2, A method according to claim 1, wherein the measurement target AP includes one or more neighboring APs that are not included in the cluster and whose distance from the one or more APs included in the cluster is less than a predetermined value.

5. 5. The method of claim 4, The method, wherein the measurement target AP includes an AP among the one or more neighboring APs whose distance to the wireless device is decreasing over time.

6. 5. The method of claim 4, The method, wherein the measurement target AP includes an AP that may be newly added to the cluster of the wireless device among the one or more neighboring APs.

7. 2. The method of claim 1 , The method, wherein the measurement information includes selection conditions for the wireless device to select the AP to be measured.

8. 8. The method of claim 7, The method, wherein the selection condition includes a condition regarding the number of the APs for which the wireless device measures the channel condition.

9. 8. The method of claim 7, The method, wherein the selection conditions include conditions related to signal strength or signal quality received by the wireless device.

10. 8. The method of claim 7, A method according to claim 1, wherein the selection conditions include conditions relating to time variations in signal strength or quality received by the wireless device.

11. one or more processors; A memory device for storing a program; A processing device for a cell-free communication system comprising: A processing device, the program, when executed by the one or more processors, causing the processing device to perform the method of any one of claims 1 to 10.

12. A program which, when executed by one or more processors of a processing device of a cell-free communication system, causes the processing device to carry out the method of any one of claims 1 to 10.

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