JP7654387B2 - Communication device, communication method, and program for communicating using multiple beam forming techniques - Google Patents

Description

The present invention relates to a control technology for a communication device that forms beams using multiple antennas.

In the technical field of wireless communication, a technique is known that uses multiple antennas to effectively utilize spatial resources in order to improve throughput and expand communication capacity. This technique includes, for example, multiple-input multiple-output (MIMO) and antenna diversity.

In a cellular communication system, a base station device can estimate the state of a transmission path based on an uplink signal (e.g., a sounding reference signal (SRS) or a demodulation reference signal (DMRS)) transmitted from a terminal device. The base station device can then adjust the antenna weight based on the estimated value, form a beam with a narrow shape and sufficiently high gain in the direction of direction, and communicate with the terminal device. As described above, this method allows the base station device to form a beam with a sufficiently high gain in the direction of direction suitable for the terminal device, and therefore allows data to be transmitted to the terminal device with high throughput. This method can also be used in frequency division duplex (FDD) systems, but is particularly useful in time division duplex (TDD) systems.

In a cellular communication system, a terminal device may observe a CSI-RS (Channel State Information Reference Signal) transmitted from a base station device and estimate the state of the downlink transmission path based on the CSI-RS. The terminal device may then identify one of a number of PMI (Precoding Matrix Indicator) values corresponding to a number of antenna weight patterns prepared in advance based on the estimation result, and notify the base station device of the identified PMI value. The base station device may form a beam using an antenna weight corresponding to the notified PMI, and communicate with the terminal device. In a technology using PMI, the terminal device may perform transmission path estimation, select a roughly suitable beam based on the transmission path estimation value, and feed back only the selection result, thereby making it possible to set a beam with little feedback.

In a method in which the base station device directly estimates the transmission path and forms a beam, a unique beam is formed according to the position of the terminal device, which makes it possible to obtain high throughput. On the other hand, in this method, the beam width is formed narrow in order to increase the gain of the beam toward the direction of the terminal device. For this reason, when the terminal device moves, a mismatch occurs between the direction of the beam and the position of the terminal device, which can result in a decrease in throughput. In contrast, in a method in which the terminal device feeds back the PMI value, a beam roughly directed toward the direction of the terminal device is used, so the maximum throughput is relatively low, but the degree of degradation in throughput due to movement of the terminal device is not large.

The present invention provides a technology that appropriately selects and uses a transmission method using multiple antennas depending on the situation.

A communication device according to one aspect of the present invention has an estimation means for estimating a state of a transmission path between the communication device and the other device using a wireless signal transmitted from the other device; an acquisition means for acquiring information regarding the identity of a beam when the communication device transmits a signal to the other device, which is determined by the other device based on the wireless signal transmitted by the communication device; a communication means for forming a first beam when transmitting a signal to the other device based on the estimated transmission path state, or forming a second beam when transmitting a signal to the other device based on the acquired information, the second beam having a beam width wider than that of the first beam, and communicating with the other device; and a control means for controlling the communication means to switch the beam to be used from the first beam to the second beam based on a first wireless quality in the other device for a first wireless signal transmitted using the first beam and a second wireless quality in the other device for a second wireless signal transmitted using a predetermined beam for determining the second beam, while communicating with the other device using the first beam.

The present invention makes it possible to appropriately select and use a transmission method using multiple antennas depending on the situation.

FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. FIG. 2 is a diagram illustrating an example of a hardware configuration of a base station device. FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. FIG. 11 is a diagram illustrating an example of a flow of processing executed by a base station device.

The following embodiments are described in detail with reference to the attached 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 necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. In addition, the same reference numbers are used for the same or similar configurations, and duplicate descriptions will be omitted.

(System Configuration)
1 shows an example of the configuration of a wireless communication system according to this embodiment. The wireless communication system is, for example, a long-term evolution (LTE) or fifth generation (5G) cellular communication system, and includes a base station device 101 having multiple antennas and a terminal device 102 having one or more antennas. Note that this is just one example, and the following discussion can be applied to any wireless communication system in which a communication device having multiple antennas forms beams using the multiple antennas and wirelessly communicates with a partner device having one or more antennas.

In this wireless communication system, the base station device can form a beam based on an estimate of the state of the transmission path between the base station device and the terminal device, and transmit a wireless signal (wireless frame) to the base station device. In this embodiment and the appended claims, the state of the transmission path between the base station device and the terminal device indicates the state of the transmission path between each of the multiple antennas of the base station device and each of one or more antennas of the terminal device. For example, when the base station device has N antennas and the terminal device has M antennas, the states of N x M transmission paths are estimated. For example, the base station device calculates a weight to be multiplied by the wireless frame to be transmitted at each of the multiple antennas based on the estimate of the state of the transmission path, and transmits the wireless frame to be transmitted multiplied by the weight from the multiple antennas in parallel. In addition, when the terminal device has multiple antennas, the base station device can transmit multiple data streams in parallel to the terminal device. That is, it is possible to use MIMO (Multiple-Input Multiple-Output) technology, in which a base station device and a terminal device both use multiple antennas to transmit and receive multiple streams. In this method, multiple data streams can be spatially multiplexed and transmitted in the same frequency band and time. In this case, for example, an antenna weight matrix (precoding matrix) of the number of transmitting antennas x the number of receiving antennas is multiplied by a vector indicating each data stream to generate a vector of the data stream to be transmitted by each transmitting antenna. Then, each of the multiple antennas of the base station device (transmitting side) transmits a corresponding element of the vector. According to this, in one example, it is possible to extract the multiple transmitted streams with high quality from the signal received by each antenna of the terminal device (receiving side).

As described above, the base station device can estimate the state of the transmission path based on a radio signal such as a sounding reference signal (SRS) transmitted from the terminal device, and calculate a precoding matrix based on the transmission path estimation value. In addition, multiple candidates for precoding matrices that can be used by the base station device may be prepared in advance, and the terminal device may decide which of the candidates the base station device should use. In this case, the terminal device notifies the base station device of information specifying the determined beam as a precoding matrix indicator (PMI), and the base station device can decide the precoding matrix to use based on the PMI.

The first beam formed by the base station device by estimating the state of the transmission path is the beam most suitable for the state of the transmission path at the time when the terminal device transmits a radio signal. However, this first beam has a narrow beam width and is vulnerable to changes in the state of the transmission path when the terminal device moves, and when such a change occurs, the throughput may deteriorate sharply. On the other hand, the second beam obtained by the terminal device determining the precoding matrix to be used from among the precoding matrix candidates is the most suitable among the candidates at the time of the determination, but in most cases, the performance is insufficient compared to the first beam. That is, in the method using PMI, only a limited number of precoding matrix candidates are prepared to reduce the amount of feedback, so the second beam is roughly suitable for the state of the transmission path in the terminal device, but is not optimal. For this reason, the second beam is generally inferior to the first beam in terms of quality such as throughput. On the other hand, the second beam is set to roughly match the state of the transmission path, so even if the state of the transmission path in the terminal device changes, sufficient gain tends to be obtained as long as the change is not significant.

In this embodiment, a technology is provided for appropriately switching and using beams based on the characteristics of such beams. Note that, below, a base station device capable of switching between a first beam and a second beam to communicate with a terminal device is described, but this is just one example, and for example, a terminal device may perform similar processing, or a similar processing may be performed in another wireless communication system.

In this embodiment, while the base station device forms a first beam and communicates with the terminal device, the base station device transmits a first radio signal such as a demodulation reference signal (DMRS) or a channel state information reference signal (CSI-RS) using the first beam. The base station device may also transmit a second radio signal such as a CSI-RS using a predetermined beam (with a relatively wide beam width) so that the terminal device can determine the PMI. The terminal device then receives the first radio signal transmitted using the first beam and measures a first radio quality related to the first radio signal. The terminal device also receives a second radio signal transmitted using a predetermined beam and measures a second radio quality related to the second radio signal. These radio qualities may be, for example, a signal-to-interference-and-noise ratio (SINR), but may also be, for example, a signal-to-noise ratio (SNR) or a received signal strength. Then, the base station device determines whether to switch the beam to be used from the first beam based on the SRS to the second beam based on the PMI based on the first radio quality and the second radio quality. If the base station device determines to switch, it uses the second beam without using the first beam, and if it determines not to switch, it continues to use the first beam and transmits data to the terminal device.

In one example, the base station device may determine that the beam to be used is switched from the first beam to the second beam based on the difference between the first wireless quality and the second wireless quality becoming equal to or lower than a predetermined level. For example, the base station device may determine that the beam to be used is switched from the first beam to the second beam based on the first wireless quality falling below the second wireless quality. In addition, the first beam generally has a narrow beam width, and it is assumed that the gain obtained in signal transmission to the terminal device will deteriorate sharply when the state of the transmission path changes due to the movement of the terminal device, etc. For this reason, when the level difference between the first wireless quality and the second wireless quality approaches to the extent that a sign of deterioration of the first wireless quality is observed, control may be executed to switch the beam to be used to the second beam. That is, when the first wireless quality is higher than the second wireless quality, the beam to be used may be switched from the first beam to the second beam. Also, the beam used may be switched from the first beam to the second beam after the value obtained by subtracting the second wireless quality level from the first wireless quality level falls below a negative predetermined value.

The terminal device may transmit a report on the first wireless quality and a report on the second wireless quality to the base station device. The base station device may determine whether to switch to the second beam as described above based on these reported values. The terminal device may also report information generated based on the first wireless quality and the second wireless quality to the base station device. For example, information indicating the difference between the first wireless quality and the second wireless quality may be generated and notified to the base station device. In one example, the difference may be indicated in 16 steps and reported as 4-bit information. Note that the number of steps and the number of bits are only examples, and 8 steps may be indicated by 3 bits, or 64 steps may be indicated by 6 bits. In one example, the steps may be in 1 dB increments, but may have any increment width, such as 2 dB increments, 0.5 dB increments, or a non-uniform increment width determined in advance.

The base station device may receive an SRS from a terminal device during communication using the second beam, calculate the radio quality assuming that the first beam is formed based on the SRS, and compare the radio quality with the radio quality measured by the terminal device in communication using the second beam to determine whether to switch the beam to be used to the first beam. For example, the base station device may estimate the state of the transmission path, such as the path loss, based on the SRS, and estimate the first reception power of the signal in the terminal device based on the gain obtained when the first beam is formed and the transmission power available to the base station device. The base station device may then receive a report of the second reception power of the signal transmitted using the second beam from the terminal device, and determine to use the first beam when the first reception power exceeds the second reception power by exceeding a predetermined level. The reception power is an example of radio quality, and other indicators may be used. The base station device may also determine to use the first beam when the first reception power exceeds the second reception power by exceeding a predetermined level for a predetermined period of time. In this way, switching from the second beam to the first beam may be performed in a similar manner to the above-mentioned method.

According to the above-mentioned processing, it is possible to appropriately switch between the first beam based on the SRS and the second beam based on the PMI based on the state of the transmission path in the terminal device. For example, when it is expected that the gain obtained with the first beam will decrease due to a change in the state of the transmission path due to the movement of the terminal device, etc., and sufficient throughput will not be obtained, it is possible to use the second beam with relatively high stability. This increases the stability of communication, while at the same time improving the throughput of the entire system by using the first beam with a higher gain when the state of the transmission path is stable because the terminal device is stationary, etc.

(Device configuration)
Next, an example of the hardware configuration of the base station device as described above will be described with reference to FIG. 2. In one example, the base station device is configured to include a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. The processor 201 is a computer configured to include one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and executes the entire processing of the base station device and each of the above-mentioned processes by reading and executing a program stored in the ROM 202 or the storage device 204. The ROM 202 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the base station device. The RAM 203 functions as a workspace when the processor 201 executes a program, and is a random access memory that stores temporary information. The storage device 204 is configured, for example, by a removable external storage device. The communication circuit 205 is configured, for example, by a circuit for wireless communication of LTE or 5G. 2 illustrates one communication circuit 205, the base station device may have multiple communication circuits, such as wireless communication circuits for LTE and 5G and a wired communication circuit for wired communication, etc. The base station device may have separate communication circuits 205 for each of multiple available frequency bands, or may have a common communication circuit 205 for at least some of the frequency bands.

Figure 3 shows an example of the functional configuration of a base station device according to this embodiment. The base station device has, for example, a communication unit 301, a transmission path estimation unit 302, a candidate matrix holding unit 303, an information acquisition unit 304, and a beam forming control unit 305 as an example of its functional configuration. Note that FIG. 3 shows only a part of the functions of the base station device that is related to the description of this embodiment, and the base station device naturally has functions as a base station device of a general cellular communication system. In addition, the base station device may have functions other than the functions shown in FIG. 3 and the general-purpose functions of a base station device. In addition, the functional blocks in FIG. 3 are shown generally, and each functional block may be realized by being integrated, or may be further subdivided. Each function in FIG. 3 may be realized, for example, by the processor 201 executing a program stored in the ROM 202 or the storage device 204, or may be realized, for example, by a processor present inside the communication circuit 205 executing predetermined software.

The communication unit 301 forms a beam based on the state of the transmission path between the terminal device and the communication unit 301 and performs wireless communication with the terminal device. The communication unit 301 is configured to form and transmit a high-gain beam in a predetermined direction, for example, by multiplying the modulated signal to be transmitted to the terminal device by a predetermined weight for each transmitting antenna and transmitting the signal in parallel. The communication unit 301 can transmit multiple signal streams in parallel by multiplying each of the multiple signal streams by a separate antenna weight and transmitting the signal in a separate direction. In this case, a waveform in which the components of the multiple signal streams are added together is sent out from each antenna.

The transmission channel estimation unit 302 performs transmission channel estimation based on an uplink radio signal received from a terminal device. The transmission channel estimation unit 302 performs transmission channel estimation based on, for example, an SRS received from the terminal device, and stores the result as an estimated value of the downlink transmission channel. Note that the SRS is an example of an uplink radio signal, and transmission channel estimation may be performed using other radio signals. The candidate matrix holding unit 303 holds multiple candidates for a pre-determined precoding matrix. Note that an indicator is attached to each of the multiple candidates, and the precoding matrix to be used is specified by the PMI from the terminal device.

The communication unit 301 generates a precoding matrix based on the state of the transmission path estimated by the transmission path estimation unit 302, forms a first beam using the matrix, and can communicate with the terminal device. The communication unit 301 also selects a precoding matrix specified by a PMI from the terminal device from among the precoding matrix candidates stored in the candidate matrix storage unit 303, forms a second beam using the matrix, and can communicate with the terminal device.

The information acquisition unit 304 acquires information for determining whether to use the first beam or the second beam. For example, during communication using the first beam, the information acquisition unit 304 acquires information capable of identifying a first wireless quality in the terminal device for a first wireless signal transmitted in the first beam from the terminal device via the communication unit 301. The information acquisition unit 304 also acquires a second wireless quality in the terminal device for a second wireless signal transmitted in a predetermined beam related to the second beam (for example, used for determining the second beam). The first wireless quality and the second wireless quality may be, for example, a signal-to-interference and noise ratio (SINR). The first wireless signal may be, for example, a DMRS transmitted immediately before user data addressed to the terminal device. The first wireless signal may be, for example, a CSI-RS specific to the terminal device, transmitted using the first beam. Furthermore, another signal may be used as the first wireless signal. The second radio signal may be, for example, a cell-specific CSI-RS (common to terminal devices in the cell). The CSI-RS is, for example, a predetermined beam for selecting the second beam, and is mapped to resources based on the number of ports of the CSI-RS and transmitted at a predetermined period. The predetermined beam is a beam with a wider beam width than a terminal device-specific beam formed based on the SRS, etc., and may be an omnidirectional beam.

In one example, the information acquisition unit 304 may acquire one piece of information generated based on the first wireless quality and the second wireless quality. This piece of information may be, for example, a difference value between the first wireless quality and the second wireless quality. A value obtained by subtracting the second wireless quality from the first wireless quality may be notified from the terminal device to the base station device as 4-bit information in 16 steps, for example, less than 0 dB, 0 dB or more and less than 1 dB, 1 dB or more and less than 2 dB, ..., 13 dB or more and less than 14 dB, and 14 dB or more. Note that this is only an example, and the difference value may be expressed in a step width of, for example, 2 dB increments. Also, 32 steps of information may be notified using 5 bits, or only 8 steps of information may be notified using 3 bits. Also, only the difference value may be notified, or either the first wireless quality or the second wireless quality may be notified together with the difference value. For example, the terminal device may notify the base station device of the first wireless quality and the difference value. The base station device may configure the terminal device with respect to the information to be notified. For example, the RRC message when establishing a connection may notify the terminal device of configuration information indicating whether to notify only the difference value, to notify the first wireless quality or the second wireless quality and the difference value, or to notify the first wireless quality and the second wireless quality.

The information acquisition unit 304 may receive a signal transmitted from a terminal device, and calculate an estimated value of the wireless quality corresponding to the first wireless quality or the second wireless quality based on the signal. For example, the information acquisition unit 304 measures the amplitude fluctuation and the phase rotation amount when the signal transmitted from each antenna of the terminal device arrives at each antenna of the base station device. Then, the information acquisition unit 304 multiplies the signal to be transmitted from each antenna in accordance with the antenna weight corresponding to the first beam and the predetermined beam by the amplitude fluctuation and the phase rotation amount measured at each antenna based on the signal transmitted from one antenna of the terminal device. Then, by adding up all the results of the multiplication, it is possible to estimate how the signal is received at one antenna of the terminal device. In this way, the information acquisition unit 304 can estimate the first wireless quality or the second wireless quality within its own device without receiving a report from the terminal device.

The beam forming control unit 305 determines whether to use the first beam or the second beam based on the first wireless quality and the second wireless quality acquired by the information acquisition unit 304, or the difference between them. The beam forming control unit 305 then controls the communication unit 301 to form a beam based on the determination. The beam forming control unit 305 performs control to use the first beam, for example, at the time of initial connection. The beam forming control unit 305 then switches the beam used for communication from the first beam to the second beam, for example, based on the difference between the levels of the first wireless quality and the second wireless quality becoming equal to or less than a predetermined level. As an example, the beam forming control unit 305 may switch the beam used for communication from the first beam to the second beam based on the level of the first wireless quality becoming lower than the level of the second wireless quality.

(Processing flow)
Next, an example of the flow of processing executed by the base station device according to this embodiment will be described with reference to Fig. 4. This processing can be realized, for example, by the processor 201 executing a program stored in the ROM 202 or the storage device 204. Note that the criteria for switching the beam used by the base station device are as described above, so only an example of the flow of processing executed by the base station device will be outlined here, and the details will not be repeated.

First, the base station device establishes a connection with the terminal device and starts communication with a first beam (S401). For example, the base station device causes the terminal device with which the connection has been established to transmit an SRS, forms a first beam based on the result of measuring the SRS, and transmits user data to the terminal device. Then, for example, the base station device transmits a first radio signal such as a DMRS or CSI-RS using the first beam immediately before transmitting user data (S402), and causes the terminal device to measure a first radio quality related to the first radio signal. In addition, even during communication using the first beam, the base station device transmits a second radio signal by periodically transmitting a CSI-RS using a predetermined beam related to a second beam based on the PMI (S403). Note that the base station device periodically transmits a CSI-RS with a predetermined beam even when not connected to the terminal device. In addition, as described above, the base station device transmits a DMRS before transmitting user data to the terminal device. As such, the order of steps S401 to S403 is merely an example, and these steps may be performed in a different order.

Then, the base station device receives a report on the first wireless quality of the first wireless signal and the second wireless quality of the second wireless signal from the terminal device (S404). This report may be, for example, a report including information indicating the first wireless quality and the second wireless quality, or a report including information indicating a level difference between the first wireless quality and the second wireless quality (and information indicating the first wireless quality or the second wireless quality as necessary). Note that, in cases where the base station device can estimate the first wireless quality and the second wireless quality using the uplink signal transmitted from the terminal device, the processes of S402 to S403 may be replaced with measuring the uplink wireless signal and calculating the wireless quality.

Then, the base station device determines whether to switch the beam to be used from the first beam to the second beam based on the relationship between the first wireless quality and the second wireless quality (S405). If the base station device determines not to switch from the first beam to the second beam (NO in S405), the process returns to S401 and continues to monitor whether the first wireless quality has deteriorated to a degree approaching the second wireless quality. On the other hand, if the base station device determines to switch from the first beam to the second beam (YES in S405), the base station device switches the beam to be used to the second beam and transmits a signal (user data) to the terminal device (S406). The base station device periodically transmits CSI-RS, and the terminal device that observes it estimates the state of the downlink transmission path and notifies the base station device of the PMI specified based on the estimation result. The base station device communicates using the second beam using the precoding matrix specified by the PMI received from the terminal device.

The base station device may then switch back to the first beam if it is determined that the state of the transmission path of the terminal device has stabilized after switching to the second beam. When switching back to the first beam, the base station device may execute the process of FIG. 4 again.

By performing the above-described processing, the base station device can appropriately switch between the first beam using a precoding matrix generated from an estimate of the state of the transmission path based on the radio signal from the terminal device, and the second beam using a precoding matrix according to the result selected by the terminal device from among multiple candidates, depending on the situation of the terminal device. This enables stable, high-quality communication suited to the situation by using the second beam when there is a large change in the state of the transmission path, such as when the terminal device is moving, and communicating using the first beam when there is a small change in the state of the transmission path.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the invention.

Claims (12)

1. A communication device, comprising:
an estimation means for estimating a state of a transmission path between the communication device and the counterpart device using a wireless signal transmitted from the counterpart device;
an acquisition means for acquiring information regarding a beam identification when the communication device transmits a signal to the counterpart device, the information being determined by the counterpart device based on a wireless signal transmitted by the communication device;
a communication means for forming a first beam when transmitting a signal to the other device based on the estimated state of the transmission path, or forming a second beam when transmitting a signal to the other device based on the acquired information , the second beam having a beam width wider than that of the first beam , and communicating with the other device;
a control means for controlling the communication means to switch a beam to be used from the first beam to the second beam based on a first wireless quality in the counterpart device for a first wireless signal transmitted in the first beam and a second wireless quality in the counterpart device for a second wireless signal transmitted in a predetermined beam related to the second beam while communicating with the counterpart device using the first beam;
A communication device comprising: The communication device according to claim 1, characterized in that the control means performs control to switch from the first beam to the second beam based on the difference between the first wireless quality and the second wireless quality becoming equal to or less than a predetermined level. The communication device according to claim 1 or 2, characterized in that the control means performs control to switch from the first beam to the second beam based on the first wireless quality falling below the second wireless quality. The communication device according to any one of claims 1 to 3, characterized in that the control means determines whether or not to switch the beam to be used from the first beam to the second beam based on a report on the first wireless quality and a report on the second wireless quality received from the other device by the communication means. The communication device according to any one of claims 1 to 3, characterized in that the control means determines whether or not to switch the beam to be used from the first beam to the second beam based on a report generated based on the first wireless quality and the second wireless quality acquired from the other device and received from the other device by the communication means. The communication device according to any one of claims 1 to 5, characterized in that the first radio signal includes a demodulation reference signal or a channel state information reference signal. The communication device according to any one of claims 1 to 6, characterized in that the second radio signal includes a channel state information reference signal. The communication device according to any one of claims 1 to 7, characterized in that the communication device is a base station device in a cellular communication system, and the other device is a terminal device in the cellular communication system. The communication device according to claim 8, characterized in that the estimation means estimates the state of the transmission path between the communication device and the counterpart device based on a sounding reference signal (SRS) transmitted from the terminal device. The communication device according to claim 8 or 9, characterized in that the acquisition means acquires a PMI (Precoding Matrix Indicator) as information regarding the identification of a beam when the communication device transmits a signal to the other device. A control method performed by a communication device, comprising:
The communication device is configured to communicate with the other device by forming a first beam when transmitting a signal to the other device based on a state of a transmission path between the communication device and the other device estimated using a wireless signal transmitted from the other device, or by forming a second beam when transmitting a signal to the other device based on information regarding a specification of a beam when the communication device transmits a signal to the other device, the second beam having a beam width wider than that of the first beam, the second beam being determined by the other device based on the wireless signal transmitted by the communication device,
The control method is characterized in that it includes, while communicating with the other device using the first beam, controlling to switch the beam to be used from the first beam to the second beam based on a first wireless quality in the other device for a first wireless signal transmitted in the first beam and a second wireless quality in the other device for a second wireless signal transmitted in a predetermined beam related to the second beam. A program for causing a computer to function as each of the means possessed by a communication device according to any one of claims 1 to 10.

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