JP7816526B2 - Wireless communication system, wireless communication method, and wireless communication control device - Google Patents

Description

The present disclosure relates to a wireless communication system, a wireless communication method, and a wireless communication control device.

Radio waves in the millimeter wave band used in 5G services and the even higher frequency bands being developed for 6G services have a high tendency to travel in a specific direction. For this reason, the use of RIS (Reconfigurable Intelligent Surface) technology is expected to be used as a means of improving communication interference caused by obstructions (Non-Patent Documents 1-3). RIS technology reflects radio waves in a specific direction by arranging electrically phase-switching elements on the surface of a reflector.

Using Any Surface to Realize a New Paradigm for Wireless Communications(Communications of the ACM, Volume 61, Issue 11, November 2018, p30-33) Wireless Communications Through Reconfigurable Intelligent Surfaces(IEEE Access, Volume 7, 13 August 2019, p116753-116773) Intelligent Reflecting Surface Enhanced Wireless Network via Joint Active and Passive Beamforming(IEEE Transactions on Wireless Communications, Volume 18, Issue 11, November 2019, p5394-5409)

RIS devices consume a lot of power because they electrically control the direction of reflection. Therefore, when connected to an environmental power generation system such as solar power generation, there is a limit to the amount of power that can be generated, making it difficult to operate the RIS device continuously. On the other hand, when connected to an external power source, although sufficient power can be supplied, there is an issue of limitations on where it can be installed.

In order to solve the above-mentioned problems, the primary objective of this disclosure is to provide a wireless communication system that can reduce power consumption by reducing the operating frequency of the RIS device.

A second objective of this disclosure is to provide a wireless communication method that can reduce power consumption by reducing the operating frequency of the RIS device.

Furthermore, a third objective of this disclosure is to provide a wireless communication control device that can reduce power consumption by reducing the operating frequency of the RIS device.

A first aspect of the present disclosure is a wireless communication system comprising a base station, a RIS device that reflects radio waves from the base station to a terminal device, and a control device that controls the RIS device, wherein the control device is configured to perform a process of pre-estimating the radio quality within the area, a process of receiving positioning information from the terminal device, a process of making a wake-up determination to determine whether the RIS device needs to be started, and, if it is determined that start-up is necessary, a startup process of sending a wake-up signal and a RIS parameter signal to the RIS device instructing it to start up; and preferably, when the RIS device receives the wake-up signal, a process of starting the RIS device and a process of controlling the reflection of radio waves at the reflecting section of the RIS device based on the RIS parameter signal.

A second aspect of the present disclosure is a wireless communication method performed by a wireless communication system including a base station, a RIS device that reflects radio waves from the base station to a terminal device, and a control device that controls the RIS device, and the wireless communication method preferably includes a process of estimating the radio quality within the area in advance, a process of receiving positioning information from the terminal device, a process of making a wake-up determination to determine whether the RIS device needs to be started, a process of sending a wake-up signal and a RIS parameter signal to the RIS device to instruct it to start up if it is determined that start-up is necessary, a process of starting the RIS device if the wake-up signal is received, and a process of controlling the reflection of radio waves at the reflecting section of the RIS device based on the RIS parameter signal.

A third aspect of the present disclosure is preferably a wireless communication control device configured to perform the following processes: a process for estimating wireless quality within an area in advance; a process for receiving positioning information from a terminal device; a process for making a wake-up determination to determine whether or not the RIS device needs to be started; and, if it is determined that startup is necessary, a process for transmitting a wake-up signal and a RIS parameter signal to the RIS device to instruct it to start up.

According to the first, second and third aspects of the present disclosure, power consumption can be reduced by reducing the operating frequency of the RIS device.

FIG. 10 is a diagram showing a simulation result of wireless quality when a RIS device is not used. FIG. 10 is a diagram showing a simulation result of wireless quality when the reflection angle of the RIS device is set to 30 degrees. FIG. 10 is a diagram showing the results of a simulation of wireless quality when the reflection angle of the RIS device is set to 60 degrees. FIG. 1 is a diagram illustrating the configuration of a conventional RIS device. FIG. 1 is a diagram illustrating a configuration of a RIS device according to a first embodiment of the present disclosure. 1 is a diagram illustrating a configuration of a wireless communication system according to a first embodiment of the present disclosure. 1 is a chart showing a startup procedure of a RIS device according to the first embodiment of the present disclosure. 1 is a flowchart illustrating a wake-up determination process according to the first embodiment of the present disclosure.

First Embodiment
Figure 1 shows the results of a wireless quality simulation when a RIS device is not used. The figure shows the results of a wireless quality simulation when an obstruction is present in a certain area, viewed from above. The area has spots divided into squares. The wireless quality is simulated for each spot, and the results are indicated by color changes.

Base station 50 is installed in the upper left of the area. Shielding object 52 is installed near the center of the area. Radio waves transmitted from base station 50 are blocked by shielding object 52. As a result, wireless quality deteriorates in area 54. Hereinafter, spots with poor wireless quality will be referred to as dead spots.

Now, RIS device 56 is installed in the position shown in Figure 1. RIS device 56 can control the reflection direction of radio waves, improving wireless quality. For example, wireless quality can be improved by setting a reflection angle of 0 degrees in area 58, a reflection angle of 20 degrees in area 60, a reflection angle of 30 degrees in area 62, and a reflection angle of 60 degrees in area 64.

Figure 2 shows the results of a simulation of wireless quality when the reflection angle of the RIS device is set to 30 degrees. That is, it shows the results of a simulation when the RIS device 56 reflects radio waves 28 transmitted from the base station 50 at a reflection angle of 30 degrees. It can be seen that the wireless quality in area 62 has improved.

Figure 3 shows the results of a simulation of wireless quality when the reflection angle of the RIS device is set to 60 degrees. That is, it shows the results of a simulation when the RIS device 56 reflects radio waves 28 transmitted from the base station 50 at a reflection angle of 60 degrees. It can be seen that the wireless quality in area 64 has improved.

As mentioned above, when improving wireless quality in the area of Figure 1, reflection control by the RIS device is effective only in area 54. In other words, when compensating for dead spots in an area, it is sufficient for the RIS device to be active when the terminal device is located in the dead spot; it does not need to be active all the time.

In this disclosure, coordinate information for dead spots and RIS parameters for compensating for dead spots are estimated in advance through simulation. The RIS device is then activated only when a user with a terminal approaches a dead spot. The RIS parameters corresponding to that dead spot are then used to control radio wave reflection. This allows the RIS device to remain in a sleep state when activation is not required, thereby reducing power consumption.

Figure 4 shows the configuration of a conventional RIS device. The conventional RIS device 30 includes a communication unit 8. The communication unit 8 receives necessary information from the outside. Examples of the necessary information include information on the amount of phase change calculated externally, or information required to calculate that amount of phase change. This information is then transmitted to the control unit 10.

The control unit 10 determines the amount of phase change in the reflecting unit 12 (described below) based on the information obtained from the communication unit 8. Then, it transmits this amount of phase change to the reflecting unit 12.

The reflector 12 reflects radio waves using multiple elements provided on the surface of the reflector. The amount of phase change used to reflect radio waves by each element is adjusted by the control unit 10. This allows the radio wave reflection characteristics to be dynamically switched.

The power supply unit 32 supplies power from an external power source to the communication unit 8, the control unit 10, and the reflection unit 12.

As mentioned above, a power source is required for the RIS device to control the reflection direction of radio waves. When the RIS device is constantly operating, the power consumption increases due to the large number of functional parts that require electricity. When the reflecting unit 12 is made larger using a large number of elements, or when multiple RIS devices are installed, the total power consumption increases even further. This requires a wired connection to an external power source, which creates the problem of limiting the locations where the RIS device can be installed.

Even if a RIS device were connected to an energy harvester such as solar power generation, there is a limit to the amount of power that can be generated by the energy harvester. This means that it is difficult to keep the RIS device running at all times, which creates the problem of increasing the likelihood that the RIS device will not be able to function when needed. This disclosure solves the above-mentioned problem.

Figure 5 is a diagram showing the configuration of a RIS device according to embodiment 1 of the present disclosure. The RIS device 2 according to embodiment 1 differs from conventional RIS devices in that it uses environmental power generation instead of an external power source.

The RIS device 2 comprises a communication unit 8, a control unit 10, and a reflecting unit 12. The communication unit 8, the control unit 10, and the reflecting unit 12 have the same functions as those of the RIS device 30. The RIS device further comprises a power generation unit 4. The power generation unit 4 generates power to ensure the power necessary to drive the RIS device 2, and sends the obtained power to the power supply unit 6. The power supply unit 6 sends the obtained power to the communication unit 8, the control unit 10, and the reflecting unit 12. This allows the RIS device to be driven without being connected to an external power source.

The amount of power that can be supplied from the power generation unit 4 is less than that of an external power source. However, in this disclosure, the operating time of the RIS device 2 is reduced by power supply control. More specifically, the RIS device 2 functions only when needed by the user. This reduces power consumption, thereby improving the user's communication quality even with a configuration like the RIS device 2.

Figure 6 is a diagram showing the configuration of a wireless communication system according to the first embodiment of the present disclosure. The wireless communication system 100 includes a terminal device 14. The terminal device 14 is a user terminal that performs wireless communication with a base station, and includes a sensor unit 16. The sensor unit 16 detects positioning information of the terminal device 14 and transmits it to the communication unit 18. The communication unit 18 transmits the positioning information to the control device 20.

The terminal device 14 may be a fixedly installed sensor terminal rather than a user terminal. In this case, what is transmitted to the control device 20 is not the positioning information of the sensor terminal itself, but rather the sensor information of the user terminal detected by the sensor terminal.

The control device 20 has a communication unit 22. The communication unit 22 receives positioning information transmitted from the terminal device 14.

The control device 20 also has a pre-estimation unit 24. The pre-estimation unit 24 performs pre-estimation of dead spots, etc. This pre-estimation may be performed using simulation or site survey results. The pre-estimation results are then transmitted to the RIS control unit 26.

The control device 20 further includes a RIS control unit 26. The RIS control unit 26 uses the results of advance estimation to manage the wake-up determination described below. If the determination indicates that the RIS needs to be driven, the necessary information is transmitted to the communication unit 22. Examples of the necessary information include information on the amount of phase change calculated externally, or information required to calculate that amount of phase change. The communication unit 22 transmits the information transmitted from the terminal device, advance estimation unit 24, and RIS control unit 26 to the RIS device 2.

The control device 20 of the present disclosure can also be realized by a computer and a program. The control device 20 can also record the program on a recording medium or provide it via a network.

The RIS device 2 receives information transmitted from the communication unit 22 via the communication unit 8. Based on this information, the control unit 10 determines the amount of phase change for the reflecting unit 12. The reflecting unit 12 reflects the radio wave 28 with the determined amount of phase change.

Figure 7 is a chart showing the startup procedure for the RIS device according to embodiment 1 of the present disclosure. First, the control device 20 performs a preliminary estimation 100. As mentioned above, dead spots and RIS parameters for compensating for the dead spots are estimated in advance through simulation. This simulation may be performed for the entire area supported by the wireless communication system 100, or may be performed only for the area that is desired to be supported by the RIS device 2.

Next, the terminal device 14 performs positioning 102a. That is, the sensor unit 16 of the terminal device 14 acquires positioning information of the terminal device 14. The positioning information is then transmitted to the control device 20. The positioning information may be transmitted periodically at any cycle, such as every 100 ms or every second. Alternatively, the positioning information may be transmitted irregularly at a timing requested by the terminal device 14 itself. Examples of the timing at which the request is made include when the communication quality falls below a certain value, or when higher communication quality is desired.

Next, the control device 20 performs a wake-up determination 104a. This is a determination to start up the RIS device 2 when the user approaches a dead spot. Details of the wake-up determination will be described later.

When a decision is made to start the RIS device 2, the control device 20 transmits a wake-up signal 106a and a RIS parameter signal 108a to the communication unit 8. This RIS parameter signal 108a includes, for example, a phase coefficient and an active time. The active time indicates the time for which each device is to be maintained in an active state.

When the communication unit 8 receives the wake-up signal 106a, it changes its status from sleep state 110a to active state 111a. The communication unit 8 is normally in sleep state, but changes its status to active state periodically or at specified times, so that it can receive a signal from the control device 20. The communication unit 8 then transmits a wake-up signal 112a and RIS parameters 114a to the control unit 10.

When the communication unit 8 sends the RIS parameter 114a, it changes its status from active state 111a to sleep state 115a. This reduces power consumption.

When the control unit 10 receives the wake-up signal 112a, it changes its status from sleep state 116a to active state 117a. The control unit 10 then transmits the RIS setting 118a to the reflector 12.

When the control unit 10 sends the RIS setting 118a, it changes the status from active state 117a to sleep state 119a. This reduces power consumption.

When the reflection unit 12 receives the RIS setting 118a, it changes its status from sleep state 120a to active state 122a. The reflection unit 12 then uses the RIS setting 118a to control the reflection of radio waves.

We will now describe the case where the active time of the reflector 12 is extended. In Figure 7, the terminal device 14 performs the next positioning 102b a certain time after the positioning 102a. Accordingly, the control device 20 and the RIS device 2 repeat the above-mentioned processing.

However, here, the operation of the reflection unit 12 differs from the above-mentioned process. If the reflection unit 12 does not receive the next RIS setting during the active time, it changes its status from the active state to the sleep state. However, the reflection unit 12 receives the next RIS setting 118b while in the active state 122a. Therefore, the active time is extended by transitioning from the active state 122a to the active state 122b. After that, because the next RIS setting is not received during the active state 122b, the status is changed to the sleep state 124b.

We will now describe the case where the wake-up determination result is that the RIS device 2 is not to be started. In Figure 7, the terminal device 14 performs the next positioning 102c a certain time after positioning 102b. Accordingly, the control device 20 performs a wake-up determination 104c. As a result, a determination is made not to start the RIS device 2, and therefore no wake-up signals or the like are transmitted thereafter.

The communication unit 8, control unit 10, and reflection unit 12 operate intermittently while maintaining a sleep state. This allows them to periodically receive signals, allowing them to receive each signal while maintaining a sleep state.

Figure 8 is a flowchart showing the wake-up determination process according to the first embodiment of the present disclosure. First, in step 150, it is determined whether the user is in or near an area requiring support. In other words, it is determined whether the user is near a dead spot.

Specifically, the positioning information transmitted from the terminal device is compared with the coordinate information of the dead spot simulated in advance. When a fixedly installed sensor terminal is used, the positioning information estimated from the sensor information is used. If the user is near a dead spot, proceed to step 152. If the user is not near a dead spot, it is determined that the startup process of the RIS device 2 is unnecessary, and the process is terminated.

In step 152, it is confirmed whether an active time has been set in the RIS device 2. If an active time has been set, proceed to step 154. If an active time has not been set, proceed to step 166.

In step 154, the RIS device 2 checks whether it is in the active time it has set. If it is in the active time, proceed to step 156. If it is not in the active time, proceed to step 162.

In step 156, it is checked whether there has been a change in the phase coefficient. If there has been a change, the process proceeds to step 158. If there has been no change, it is determined that startup processing of the RIS device 2 is not necessary, and the process ends. In other words, this prevents unnecessary power consumption as a result of performing further startup processing on an already running RIS device 2.

In step 158, the phase coefficient is set and the process proceeds to step 160. In step 160, a wake-up signal is sent and the process ends. This wake-up signal includes information about the phase coefficient.

In step 162, the active time is set. Any value can be set for this active time. Once the setting is complete, proceed to step 164.

In step 164, it is checked whether there are any changes to the phase coefficients. If there are any changes, proceed to step 166. If there are no changes, proceed to step 170.

In step 166, the phase coefficient is set and processing proceeds to step 168. In step 168, a wake-up signal is sent and processing ends. This wake-up signal includes information on the active time and phase coefficient.

In step 170, a wake-up signal is sent and processing ends. This wake-up signal includes active time information.

In step 172, the active time is set. Any value can be set for this active time. Once the setting is complete, proceed to step 172.

In step 172, the phase coefficient is set and processing proceeds to step 174. In step 174, a wake-up signal is sent and processing ends. This wake-up signal includes information on the active time and phase coefficient.

As described above, according to the aspects of the present disclosure, the RIS device can be activated only when the user is in an area with poor communication quality. This allows the RIS device to maintain its sleep state to the maximum extent possible, thereby reducing the power consumption of the RIS device. Furthermore, even when the power supply to the RIS device is lower than that of an external power source, such as when powering the RIS device using environmental power generation, the RIS device can function for a long period of time.

12 Reflection unit 14 Terminal device 20 Control device 28 Radio wave 50 Base station 100 Wireless communication system

Claims (4)

A wireless communication system including a base station, a RIS device that reflects radio waves from the base station to a terminal device, and a control device that controls the RIS device,
The control device
A process of estimating wireless quality in an area in advance;
a process of receiving positioning information from the terminal device;
A process of performing a wake-up determination to determine whether or not the RIS device needs to be started;
When it is determined that activation is necessary, the RIS device is configured to execute an activation process of transmitting a wake-up signal and an RIS parameter signal to the RIS device,
The RIS device
When the wake-up signal is received, the RIS device is started up;
and a process of controlling the reflection of radio waves in a reflecting unit of the RIS device based on the RIS parameter signal ,
The RIS parameter signal includes at least one of an active time, which is a time for putting the RIS device into an active state, and a phase coefficient used for the reflection control.
Wireless communication system. The startup process
The wireless communication system according to claim 1 , further comprising a process of transmitting the wake-up signal and the RIS parameter signal when the active time is set in the RIS device and the RIS device is not in the active time. A wireless communication method performed by a wireless communication system including a base station, a RIS device that reflects radio waves from the base station to a terminal device, and a control device that controls the RIS device,
The control device
A process of estimating wireless quality in an area in advance;
a process of receiving positioning information from the terminal device;
A process of performing a wake-up determination to determine whether or not the RIS device needs to be started;
If it is determined that activation is necessary, a process of transmitting a wake-up signal and a RIS parameter signal to the RIS device to instruct activation;
Run
The RIS device
When the wake-up signal is received, the RIS device is started up;
A process of controlling the reflection of radio waves in a reflecting unit of the RIS device based on the RIS parameter signal;
Run
The RIS parameter signal includes at least one of an active time, which is a time for putting the RIS device into an active state, and a phase coefficient used for the reflection control.
Wireless communication method. A process of estimating wireless quality in an area in advance;
A process of receiving positioning information from a terminal device that is the destination of the radio wave reflection;
A process of performing a wake-up determination to determine whether or not the RIS device to be controlled needs to be started;
If it is determined that activation is necessary, a process of transmitting a wake-up signal and a RIS parameter signal to the RIS device to instruct activation;
configured to run
The RIS parameter signal includes at least one of an active time, which is a time for putting the RIS device into an active state, and a phase coefficient used for reflection control.
Wireless communication control device.