RELAY CONTROL SYSTEM, RELAY APPARATUS, AND RELAY CONTROL METHOD

A relay apparatus includes a plurality of reflection elements that applies independent phase shifts to an incoming wave, a communication circuitry that receives transmission point information from one or more transmission points, an element allocation circuitry, and a phase control circuitry. The element allocation circuitry determines the number of communication links to be established via the relay apparatus based on the transmission point information, determines the number of reflection elements to be allocated to each of the communication links, and determines a reflection element to be allocated to each of the communication links according to the number of the reflection elements. The phase control circuitry determines the phase weights so that a beam directed to a reception point being a communication destination of each communication link is generated by a reflection wave generated by each reflection element allocated to each of the communication links.

TECHNICAL FIELD

The present disclosure relates to a relay control system, a relay apparatus, and a relay control method, and particularly to a relay control system, a relay apparatus, and a relay control method for relaying wireless communication using a reconfigurable intelligent surface.

BACKGROUND ART

NPL 1 and NPL 2 below disclose a technique using a reconfigurable intelligent surface (RIS) as a relay apparatus for wireless communication.

FIG.1illustrates a conventional configuration of a wireless communication relay control system using the RIS. The system illustrated inFIG.1includes a transmission point10, a reception point12, and a RIS20. The transmission point10is configured of a radio base station or the like under the management of a communication carrier. The reception point12is configured of a user terminal such as a smart phone. The RIS20is disposed to relay a radio signal between the transmission point10and the reception point12.

FIG.2illustrates the configuration of a conventional RIS20. The RIS20includes a communication unit22. The communication unit22receives information necessary for controlling the RIS20from the transmission point10or the reception point12. The control information acquired by the communication unit22is provided to a phase control unit24.

The phase control unit24performs a process for controlling a phase to be applied to the reflection wave based on the control information. The result of the phase control is provided to a reflection unit26.

The reflection unit26is provided with a large number of reflection elements disposed two-dimensionally. Each of the reflection elements can reflect an incoming wave incident in a high frequency band after controlling a phase. The phase control is performed for each of the reflection elements included in the reflection unit26. When appropriate phase control is performed in each of the reflection elements, the communication wave reflected by the reflection unit26becomes a beam directed in a specific direction.

In a situation where an obstacle exists between the transmission point10and the reception point12, it is sometimes difficult to directly transmit and receive a radio signal between the transmission point10and the reception point20. In such a case, if the RIS20generates a beam toward the reception point12by phase control, good receiving characteristics can be obtained at the reception point12. Therefore, the RIS20is useful for expanding coverage in a high frequency band.

CITATION LIST

Non Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the conventional relay control system, the RIS20is disposed to connect one transmission point10to one reception point12. On the other hand, in the field of radio communication, an increase in the number of transmission points is expected as the number of distributed antennas and the number of cells is reduced. If the RIS20is installed for each transmission point, the network cost increases. In addition, if the number of RISs20to be disposed is increased, it is difficult to secure installation places.

The present disclosure has been made in view of the above problems, and a first object thereof is to provide a relay control system that suppresses network costs and facilitates securing of an installation place using a relay apparatus that reflects incoming waves from each of a plurality of transmission points toward each of a plurality of reception points.

In addition, a second object of the present disclosure is to provide a relay apparatus that reflects incoming waves from each of a plurality of transmission points toward each of a plurality of reception points, thereby suppressing network costs and facilitating securement of an installation place.

In addition, a third object of the present disclosure is to provide a relay control method for suppressing network costs and facilitating securing of an installation place using a relay apparatus that reflects incoming waves from each of a plurality of transmission points toward each of a plurality of reception points.

Solution to Problem

In order to achieve the above object, it is preferable that a first aspect is a relay control system using a relay apparatus including a plurality of reflection elements capable of applying independent phase shifts to incoming waves, the system includinga communication unit that receives transmission point information from one or a plurality of transmission points,an element allocation unit that determines allocation of the plurality of reflection elements based on the transmission point information, anda phase control unit that applies a phase weight to each of the plurality of reflection elements, in whichthe element allocation unit is configured to executea process of determining the number of communication links to be established via the relay apparatus based on the transmission point information,an element number determination process of determining the number of reflection elements allocated to each of the communication links, anda process of determining reflection elements to be allocated to each of the communication links according to the determined number, andthe phase control unit is configured to execute a process of determining the phase weight so that a beam directed to a reception point being a communication destination of each communication link is generated by a reflection wave generated by each reflection element allocated to each of the communication links.

In addition, it is preferable that a second aspect is a relay apparatus includinga reflection unit including a plurality of reflection elements capable of applying independent phase shifts to an incoming wave,a communication unit that receives transmission point information from one or a plurality of transmission points,an element allocation unit that determines allocation of the plurality of reflection elements based on the transmission point information, anda phase control unit that applies a phase weight to each of the plurality of reflection elements, in whichthe element allocation unit is configured to executea process of determining the number of communication links to be established based on the transmission point information,a process of determining the number of reflection elements allocated to each of the communication links, anda process of determining reflection elements to be allocated to each of the communication links according to the determined number, andthe phase control unit is configured to execute a process of determining the phase weight so that a beam directed to a reception point being a communication destination of each communication link is generated by a reflection wave generated by each reflection element allocated to each of the communication links.

In addition, it is preferable that a third aspect is a relay control method using a relay apparatus including a plurality of reflection elements capable of applying independent phase shifts to incoming waves, the method includinga step of receiving transmission point information from one or a plurality of transmission points,an element allocation step of determining allocation of the plurality of reflection elements based on the transmission point information, anda phase control step of applying a phase weight to each of the plurality of reflection elements, in whichthe element allocation step includesa step of determining the number of communication links to be established via the relay apparatus based on the transmission point information,a step of determining the number of reflection elements to be allocated to each of the communication links, anda step of determining reflection elements to be allocated to each of the communication links according to the determined number, andthe phase control step includes a step of determining the phase weight so that a beam directed to a reception point being a communication destination of each communication link is generated by a reflection wave generated by each reflection element allocated to each of the communication links.

Advantageous Effects of Invention

According to the first to third aspects, the single relay apparatus can reflect incoming waves from each of the plurality of transmission points toward each of the plurality of reception points. Therefore, according to these aspects, in a situation where a number of transmission points exist, the network cost is suppressed as compared with a case where one relay apparatus is set for each transmission point, and the installation place can be easily secured.

DESCRIPTION OF EMBODIMENTS

First Embodiment

[Configuration of First Embodiment]

FIG.3illustrates a configuration of a relay control system of First Embodiment of the present disclosure. The system illustrated inFIG.3includes a first transmission point30-1and a first reception point32-1, and a second transmission point30-2and a second reception point32-2. Hereinafter, in a case where it is not necessary to distinguish the first transmission point30-1from the second transmission point30-2, the suffixes of the reference numerals are omitted, and they are simply referred to as “transmission point30.” Similarly, in a case where it is not necessary to distinguish the first reception point32-1from the second reception point32-2, they are simply referred to as “reception point32.”

In the present embodiment, the transmission point30is configured by a radio base station or the like under the management of a communication carrier. On the other hand, the reception point32is configured of a user terminal such as a smartphone. In a case where the reception point32belongs to the communication area of the transmission point30and there is no obstacle or the like between them, the reception point32can directly communicate with the transmission point30.

The relay control system according to the present embodiment includes a relay apparatus40. The relay apparatus40is configured by a reconfigurable intelligent surface, that is, a RIS. The relay apparatus40is disposed to relay a radio signal between the transmission point30and the reception point32. Even in a case where direct communication with the transmission point30cannot be performed, the reception point32may communicate with the transmission point30via the relay apparatus40.

FIG.4is a block diagram for illustrating a configuration of the relay apparatus40. As illustrated inFIG.4, the relay apparatus40includes a communication unit42. The communication unit42is a block for transmitting and receiving control information to and from the transmission point30or the reception point32in order to be used for controlling the relay apparatus40. The control information acquired by the communication unit42is provided to an element allocation unit44and a phase control unit46. In addition, the processing result of the element allocation unit44is provided to the phase control unit46. The processing result of the phase control unit46is provided to a reflection unit48.

FIG.5is a diagram for illustrating a configuration of the reflection unit48. As illustrated inFIG.5, the reflection unit48has a plurality of reflection elements50. The reflection elements50are disposed regularly and two-dimensionally at equal intervals. Each of the reflection elements50has a mechanism for reflecting or transmitting a radio wave emitted from the transmission point30. Individual IDs are applied to the reflection elements50, and they can be controlled independently of each other. More specifically, each of the reflection elements50can generate a reflection wave with a desired phase shift by adding a desired phase weight to an incoming wave.

The phase shift can be generated, for example, by connecting a variable phase shifter for applying an arbitrary phase shift to each reflection element50. Alternatively, the phase shift may be generated using a device capable of controlling the phase in a binary manner by turning on and off the switch. In addition, the phase of the incoming wave reflected by the reflection element50may be shifted by another method.

The description will proceed with reference toFIG.4again. A control signal for each of the reflection elements50is provided to the reflection unit48from the phase control unit46. The control signal includes a phase weight command for each of the reflection elements50. The phase weight can be calculated, for example, by a method of channel estimation, a method of using position information (for example, see Japanese Patent No. 5200090), or other known methods.

As described above, the phase control unit46is provided with the processing result of the element allocation unit44. The element allocation unit44is a block for determining how to allocate the reflection elements50of the reflection unit48based on the control information received from the communication unit42. Specifically, the element allocation unit44determines the number of communication links to be handled by the relay apparatus40based on control information from the communication unit42. For example, in a case where the communication unit42receives the control information from two transmission points30-1and30-2, it is determined that there are two communication links.

The element allocation unit44then determines the number of reflection elements50to be allocated to each of the communication links. Further, the element allocation unit44concretely determines the reflection elements50to be allocated to each of the communication links based on the determined number. Then, the element allocation unit44provides the determination result to the phase control unit46.

The phase control unit46provides a control signal for achieving a phase shift suitable for each communication link to the reflection element50allocated to each communication link. Thus, a plurality of reflection waves for establishing a plurality of communication links is generated by one relay apparatus40.

[Operation of First Embodiment]

FIG.6is a flowchart for illustrating an operation of the relay control system illustrated inFIG.3. In the example illustrated inFIG.6, first, the first transmission point30-1generates transmission point information (step100). Then, the second transmission point30-2generates transmission point information (step102).

The transmission point information includes, for example, a part or all of the following information.(1) Transmission point identification number(2) Frequency channel(3) Required number of reflective elements(4) Positional information and installation height of transmitting point(5) Traffic volume (cumulative traffic, time average traffic volume, or measured traffic volume in a fixed period)(6) The number of connected terminals (the number of reception points to establish communication)

Both transmission point information generated at the first transmission point30-1and the second transmission point30-2are received by the relay apparatus40. The relay apparatus40first determines that the number of communication links to be established is two based on them. Then, the relay apparatus40determines the number of reflection elements50to be allocated to each transmission point30and the element ID (step104).

Specifically, the allocation of the reflection elements50is calculated based on the “allocation index” set by the following method. The following methods may be selectively used as a single method, or may be used in combination of two or three or more methods.

(1) An allocation index is set according to “the required number of reflection elements” included in the transmission point information. Thus, this makes it possible to respond to requests from each transmission point30.

(2) An allocation index is set in accordance with the distance between each transmission point30and the relay apparatus40. Specifically, first, the distance between the transmission point30and the relay apparatus40is calculated based on the “position information” included in the transmission point information. This calculation may be executed by the relay apparatus40, but may be executed by an external control device (not illustrated) and the result may be provided to the relay apparatus40. The relay apparatus40allocates more reflection elements as the distance is longer. An incoming wave from the transmission point30is attenuated as the propagation distance becomes longer. According to the above-mentioned method, the influence of attenuation can be suppressed by allocating a large number of reflection elements to an incoming wave having a large attenuation.

(3) An allocation index is set according to the “traffic amount” included in the transmission point information. The relay apparatus40allocates many reflection elements50to the transmission point30having a large traffic volume. Thus, the reflection wave with high intensity can be generated at the transmission point30with a large traffic volume, and an environment in which excellent communication quality can be easily secured can be disposed.

(4) An allocation index is set according to “the number of connected terminals” included in the transmission point information. The relay apparatus40allocates many reflection elements50to a transmission point where the number of connected terminals is large. Thus, it is possible to suppress the number of reflection elements50allocated to individual terminals from becoming unbalanced.

When the setting of the “allocation index” is completed, the relay apparatus40calculates the number of the reflection elements50to be allocated to each transmission point according to the following equation.

Note that, the “total amount of allocation indexes” is a total value of “allocation indexes” for all transmission points30.

It is to be noted that Equation (1) above may be replaced by Equation (2) below by weighting each transmission point. The weight can be set between “0” and “1,” and the total sum of the weights of the respective transmission points is set to “1”.

According to the method using Equation (2) above, by applying a large weight to the specific transmission point30, it is possible to prepare an environment in which communication related to the transmission point30is given priority to communication related to another transmission point30.

FIG.7illustrates an example of the allocation of the reflection elements50to two transmission points30in which the assignment conditions, that is, the “allocation index” and the “weight” are the same. In this case, among a plurality of reflection elements50provided in the reflection unit48, an element group50-1of a left half is allocated to the first transmission point30-1, and an element group50-2of a right half is allocated to the second transmission point30-2. However, the allocation method is not limited to such a simple division, and as long as the allocation number is satisfied, a specific combination of elements to be assigned can be freely set including a random combination. In addition, the number of transmission points30is not limited to two, and the number of transmission points30may be three or more, and the reflection elements50may be allocated to three or more transmission points30. By the above processing, the ID of the reflection element50allocated to each transmission point30is linked to the transmission point30of the assignment destination.

In the flowchart illustrated inFIG.6, next, the phase to be added to each of the reflection elements50is determined (step106). This processing is performed so that a beam directed to the reception point32which is a communication destination of each transmission point30is generated by a reflection wave generated by each reflection element50connected to each transmission point30.

However, in a case where one transmission point30communicates with two or more reception points32, a plurality of communication links are established for the transmission point30. Then, the reflection element50is allocated to each of the plurality of communication links. In this case, the processing of step106is performed so that a beam directed to the reception point32which is the communication destination of each communication link is generated by the reflection wave generated by each of the reflection elements allocated to each communication link.

In the example illustrated inFIG.6, a radio signal is transmitted from the first transmission point30-1following the processing of step106(step108). The signal is reflected by the reflection element50allocated to the first transmission point30-1in the relay apparatus40. As a result, this signal becomes a beam directed to the first reception point32-1, and is received by the first reception point32-1via the first communication link (step110).

In the example illustrated inFIG.6, furthermore, the radio signal is transmitted from the second transmission point30-2(step112). The signal is reflected by the reflection element50allocated to the second transmission point30-2in the relay apparatus40. As a result, the signal becomes a beam directed to a second reception point32-2, and is received by the second reception point32-2via a second communication link (step114).

As described above, according to the relay control system of the present embodiment, a plurality of communication links connecting each of the plurality of transmission points30and each of the plurality of reception points32can be established by using one relay apparatus40. Thus, in this system, the network cost can be suppressed and the installation place of the relay apparatus40can be easily secured as compared with a conventional configuration in which one relay apparatus40is installed for each transmission point30.

Second Embodiment

Next, Second Embodiment of the present disclosure will be described with reference toFIGS.8to10.

FIG.8is the diagram for illustrating a configuration of a relay control system of Second Embodiment of the present disclosure. Note that, inFIG.8, the same elements as those illustrated inFIG.3are designated by a common reference numeral, and the description thereof will be omitted or simplified.

The relay control system of the present embodiment is similar to the relay control system of First Embodiment except that the functions of the relay apparatus40are distributed to a control device60and a relay apparatus70. More specifically, in the present embodiment, the function of element allocation provided in the relay apparatus40in First Embodiment is provided not to the relay apparatus70but to the control device60.

FIG.9is a block diagram for functionally illustrating the configuration of the control device60illustrated inFIG.8. As illustrated inFIG.9, the control device60in the present embodiment includes the communication unit42and the element allocation unit44. These functions are similar to those of the communication unit42and the element allocation unit44provided in the relay apparatus40in First Embodiment. That is, in the present embodiment, a control unit60installed separately from the relay apparatus70receives transmission point information from each of the transmission points30, the number and ID of the reflection elements50to be allocated to each transmission point30are determined based on the transmission point information.

FIG.10is a block diagram for functionally illustrating the configuration of the relay apparatus70illustrated inFIG.8. As illustrated inFIG.10, the relay apparatus70according to the present embodiment includes a communication unit72. The communication unit72is a block for receiving the result of element allocation, that is, the ID information of the reflection element50allocated to each transmission point30, from the control device60. The phase control unit46of the relay apparatus70provides the phase weight information to each of the reflection elements50in accordance with the ID information thus received, as in First Embodiment.

As a result, the relay control system of the present embodiment can establish a plurality of communication links connecting each of the plurality of transmission points30and each of the plurality of reception points32by using one relay apparatus70, as in the case of First Embodiment. Therefore, the system of the present embodiment can also suppress the network cost and easily secure the installation place of the relay apparatus40, as in the case of First Embodiment, and sufficient coverage can be obtained.

REFERENCE SIGNS LIST