JP7701901B2 - Radio station and communication method - Google Patents

Description

The present invention relates to a radio station used for wireless communication and a communication method for the radio station.

In a wireless communication system, a synchronization signal is transmitted from a base station to a wireless terminal at a predetermined period. Patent Document 1 discloses that a synchronization signal block (SSB) is transmitted periodically in a fifth-generation (5G) communication system.

Special Publication No. 2021-520128

In conventional systems, beams containing synchronization signals are transmitted at a specified interval even in directions where no wireless terminals are present. Although such beams do not contribute to communication between the base station and wireless terminals, they result in unnecessary consumption of base station resources, which is a problem.

The present invention was made in consideration of these points, and aims to prevent wireless station resources from being wasted.

A wireless station according to a first aspect of the present invention includes a beam transmitting unit that transmits a wireless station beam toward one or more wireless terminals while changing its orientation at a predetermined period, a beam receiving unit that receives a terminal beam from the one or more wireless terminals after the beam transmitting unit transmits the wireless station beam, an orientation estimating unit that estimates one or more orientations corresponding to the one or more wireless terminals, a range determining unit that determines a terminal orientation range including the one or more orientations estimated by the orientation estimating unit, and a sweep control unit that controls the beam transmitting unit to transmit the wireless station beam at one or more first timings corresponding to one or more orientations included in the terminal orientation range and not to transmit the wireless station beam at one or more second timings corresponding to ranges outside the terminal orientation range.

The sweep control unit may control the beam transmission unit to retransmit, at the second timing, the radio station beam including the same data as the data included in the radio station beam transmitted at the first timing.

The sweep control unit may control the beam transmission unit to transmit the radio station beam including first purpose data at the first timing, and to transmit the radio station beam including second purpose data different from the first purpose data at the second timing.

The sweep control unit may control the beam receiving unit to receive the terminal beam transmitted from the wireless terminal at the second timing.

The device may further include a storage unit that stores the orientation of the wireless terminal in association with time, and the sweep control unit may control the beam transmission unit to transmit the wireless station beam to a range excluding the orientation of the wireless terminal that is not stored in the storage unit for a predetermined period of time.

The wireless station may further include a moving speed identification unit that identifies the moving speed of the wireless terminal relative to the wireless station, a calculation unit that calculates a variation value that indicates the magnitude of variation of the multiple moving speeds corresponding to multiple time points, and an identification unit that identifies the terminal direction range at the next time based on the direction of the terminal beam most recently received from the wireless terminal by the beam receiving unit, the moving speed, and the variation value.

The communication method of the second aspect of the present invention includes the steps of transmitting a radio station beam directed to one or more wireless terminals to a beam transmitting unit while changing the orientation at a predetermined period, receiving a terminal beam from the wireless terminal after transmitting the radio station beam, estimating one or more orientations corresponding to the one or more wireless terminals, determining a terminal orientation range including the estimated one or more orientations, and controlling the beam transmitting unit to transmit the radio station beam at one or more first timings corresponding to one or more orientations included in the terminal orientation range and not to transmit the radio station beam at one or more second timings corresponding to a range outside the terminal orientation range.

The present invention has the effect of preventing unnecessary consumption of resources at wireless stations.

1 is a diagram showing an outline of a communication sequence between a wireless station 1 in a wireless communication network and a wireless terminal 2 that wirelessly communicates with the wireless station 1. A diagram showing the transmission timing of an SSB beam. 2 is a diagram showing a range in which a wireless station 1 sweeps a beam. FIG. FIG. 2 is a diagram showing a configuration of a wireless station 1. 4 is a flowchart showing a process flow of the wireless station 1; FIG. 11 is a diagram illustrating a configuration of a wireless station 1A according to a second embodiment.

First Embodiment
[Overview of wireless communication system S]
1 to 3 are diagrams for explaining an overview of a wireless communication system S according to the present embodiment. FIG. 1 is a diagram showing an overview of a communication sequence between a wireless station 1 of a wireless communication network and a wireless terminal 2 that wirelessly communicates with the wireless station 1. The wireless station 1 functions as a master station in wireless communication, and is, for example, a base station or a relay station. The wireless terminal 2 functions as a slave station in wireless communication, and is, for example, a smartphone or a tablet. The wireless station 1 wirelessly communicates with one or more wireless terminals 2. The wireless communication network of this embodiment is, for example, a 5G wireless communication network, but the type of wireless communication network is arbitrary.

Wireless station 1 and wireless terminal 2 communicate with each other while sequentially changing the direction in which the beam is swept. Each ellipse in FIG. 1 shows a schematic representation of the shape of the beam. The shaded ellipse indicates a beam corresponding to a direction in which wireless station 1 and wireless terminal 2 are transmitting and receiving beams at a certain point in time, and the white ellipse indicates a beam corresponding to a direction in which wireless station 1 and wireless terminal 2 are not transmitting or receiving beams at that point in time.

In the initial stage, wireless station 1 sequentially transmits SSB beams, which are synchronization signal blocks, in all directions at a period of 20 ms. When wireless terminal 2 receives the SSB beam, it transmits a response beam to wireless station 1 indicating information (beam ID) for identifying the SSB beam with the highest received power.

Next, wireless station 1 sequentially transmits a channel state information estimation reference signal (CSI-RS) in multiple directions using a beam narrower than in the initial stage within the range corresponding to the beam ID indicated by the response beam received from wireless terminal 2. Wireless terminal 2 transmits a response beam indicating the beam ID of the beam with the maximum received power toward wireless station 1. Wireless station 1 then starts transmission using the beam ID indicated by the response beam, and wireless terminal 2 starts reception in the direction in which the received power of the beam corresponding to that beam ID is maximum. This starts transmission and reception of actual data (DATA) between wireless station 1 and wireless terminal 2.

Figure 2 shows the transmission timing of an SSB beam. The horizontal axis in Figure 2 represents time. As shown in Figure 2, an SSB beam is transmitted at a period of 20 ms, with timing corresponding to multiple transmission time slots within one radio frame.

Conventional wireless station 1 transmits SSB beams at all times when it is possible to transmit SSB beams. However, even if an SSB beam is transmitted at a time corresponding to a direction in which it is estimated that no wireless terminal 2 is present, the SSB beam is not received by wireless terminal 2, resulting in wasted resources. Therefore, the wireless station 1 of this embodiment is characterized in that it does not transmit an SSB beam at a time corresponding to a direction in which it is estimated that no wireless terminal 2 is present (for example, the time of time slot SSB#2 shown in gray in FIG. 2).

Figure 3 is a diagram showing the range in which wireless station 1 sweeps its beam. In Figure 3, θ is the deflection angle based on the first axis of a spherical coordinate system whose origin is the position of wireless station 1, and φ is the deflection angle based on the second axis perpendicular to the first axis. Each of the solid-line circles arranged at equal intervals in the θ-axis and φ-axis directions indicates the irradiation range of the beam in one direction. The dashed-line circles indicate the range in a direction in which no wireless terminal 2 is present (hereinafter sometimes referred to as the "terminal-absent range").

In this case, wireless station 1 does not transmit the beams shown in gray that are included in the range where no terminals are present. In other words, wireless station 1 does not transmit SSB beams at the timings when it would transmit beams shown in gray. Wireless station 1 transmits SSB beams only at the timings when it would transmit beams shown in white. The timings when it transmits beams shown in gray are, for example, the timings assigned to time slot SSB#2 shown in gray in FIG. 2.

The configuration of the wireless station 1 that operates in this manner will be described in detail below. In the following description, the beam transmitted by the wireless station 1 will be referred to as a wireless station beam, and the beam transmitted by the wireless terminal 2 will be referred to as a terminal beam.

[Configuration of Wireless Station 1]
4 is a diagram showing the configuration of the wireless station 1. The wireless station 1 has a communication unit 11, a storage unit 12, and a control unit 13. The communication unit 11 has a beam transmission unit 111 and a beam reception unit 112. The control unit 13 has an azimuth estimation unit 131, a range determination unit 132, and a sweep control unit 133.

The communication unit 11 functions as a beam sweep unit that sweeps a beam within a range specified by the sweep control unit 133. The beam transmission unit 111 transmits a radio station beam toward one or more wireless terminals while changing the direction at a predetermined period. The beam transmission unit 111 transmits a radio station beam within a range specified by the sweep control unit 133.

The beam receiving unit 112 receives terminal beams from one or more wireless terminals 2 after the beam transmitting unit 111 transmits a wireless station beam. The beam receiving unit 112 receives terminal beams arriving from a range specified by the sweep control unit 133. When the beam receiving unit 112 receives a terminal beam, it inputs an electrical signal based on the received terminal beam to the direction estimating unit 131.

The storage unit 12 includes storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage unit 12 stores programs executed by the control unit 13. The storage unit 12 also stores data used by the control unit 13 to estimate the direction of the wireless terminal 2 and sweep the beam within the range of the estimated direction. The storage unit 12 stores, for example, direction history data that associates the direction in which the beam receiving unit 112 received a terminal beam with the time at which the terminal beam was received. The storage unit 12 also stores data indicating the range in which the wireless terminal 2 is located.

The control unit 13 has, for example, a CPU (Central Processing Unit). The control unit 13 executes the programs stored in the storage unit 12 to function as an orientation estimation unit 131, a range determination unit 132, and a sweep control unit 133.

The direction estimation unit 131 estimates one or more directions corresponding to one or more wireless terminals 2. The direction estimation unit 131 creates direction history data including the results of estimating the direction of the wireless terminal 2 that transmitted the terminal beam by analyzing the terminal beam (e.g., a response beam) input from the beam receiving unit 112, and stores the created direction history data in the memory unit 12.

Specifically, the direction estimation unit 131 creates direction history data that associates the time when the beam receiving unit 112 received the terminal beam with coordinates indicating the estimated direction. For example, each time the direction estimation unit 131 estimates the direction of the wireless terminal 2 based on the terminal beam input from the beam receiving unit 112, it adds the coordinates and time of the new direction to the direction history data stored in the memory unit 12.

After adding a direction to the direction history data, the direction estimation unit 131 may delete the direction from the direction history data when the wireless terminal 2 is no longer present in that direction. For example, when the beam reception unit 112 does not receive a response beam in response to the transmission of an SSB beam by the beam transmission unit 111, the direction estimation unit 131 deletes the direction in which the beam transmission unit 111 transmitted the SSB beam from the direction history data.

The direction estimation unit 131 may estimate the direction of the wireless terminal 2 using any method. For example, the direction estimation unit 131 estimates the direction of the wireless terminal 2 using the following equation (1).
Here, P(θ) is the power of the terminal beam received by the beam receiving unit 112 from the angle θ.

The range determination unit 132 determines a predetermined range in which the beam transmission unit 101 transmits a beam based on the direction of the wireless terminal 2 estimated by the direction estimation unit 131. That is, the range determination unit 132 determines a terminal direction range including one or more directions estimated by the direction estimation unit 131. The terminal direction range coincides with the irradiation range of one or more wireless station beams corresponding to one or more directions estimated by the direction estimation unit 131 that the wireless terminal 2 exists, for example. The range determination unit 132 may set the terminal direction range to a range that includes a margin in addition to the irradiation range of one or more wireless station beams in which the wireless terminal 2 exists. As an example, the range determination unit 132 may include the irradiation range of a wireless station beam adjacent to the irradiation range of one or more wireless station beams in which the wireless terminal 2 exists, in the terminal direction range.

The sweep control unit 133 controls the beam transmitting unit 111 and the beam receiving unit 112. The sweep control unit 133 controls the beam transmitting unit 111 to transmit radio station beams at one or more first timings corresponding to one or more directions included in the terminal direction range determined by the range determination unit 132, and not to transmit radio station beams at one or more second timings corresponding to ranges outside the terminal direction range. The first timings are, for example, the transmission timings of time slots SSB#0, SSB#1, and SSB#3 shown in white in FIG. 2, and the second timings are the transmission timings of time slot SSB#2 shown in gray in FIG. 2.

The terminal direction range includes the direction of the wireless terminal 2 estimated by the direction estimation unit 131 within the specified period. Therefore, the sweep control unit 133 determines whether or not to transmit a wireless station beam based on the terminal direction range determined by the range determination unit 132, and controls the beam transmission unit 111 to transmit a wireless station beam to a range excluding the direction of the wireless terminal 2 that is not stored in the storage unit 12 for the specified period. The sweep control unit 133 then controls the beam transmission unit 111 not to transmit a wireless station beam to the direction of the wireless terminal 2 that is not stored in the storage unit 12 for the specified period. The specified period is, for example, one minute, which is a period during which it can be determined that the wireless terminal 2 has moved.

The sweep control unit 133 may control the beam transmission unit 111 to retransmit, at the second timing, a radio station beam including the same data as that included in the radio station beam transmitted at the first timing. For example, the sweep control unit 133 causes the beam transmission unit 111 to retransmit, at the second timing, the SSB beam transmitted at the first timing. At this time, the sweep control unit 133 causes the beam transmission unit 111 to transmit the same SSB beam at the second timing in the direction in which the SSB beam was transmitted at the first timing.

Specifically, in the example shown in FIG. 2, the sweep control unit 133 causes the beam transmitting unit 111 to transmit the SSB beam transmitted by the beam transmitting unit 111 in time slot SSB#1 also in time slot SSB#2. By operating the sweep control unit 133 in this manner, the same SSB beam is retransmitted in the same direction. Therefore, even if noise temporarily occurs in that direction at the timing of time slot SSB#1, the wireless terminal 2 can receive the SSB beam in time slot SSB#2, improving the signal-to-noise ratio.

The sweep control unit 133 may control the beam transmission unit 111 to transmit a radio station beam including first use data at a first timing, and to transmit a radio station beam including second use data different from the first use data at a second timing. The first use data is, for example, data included in an SSB beam, and the second use data is data included in a PDCCH (Physical Downlink Control Channel), a CDSCH (Physical Downlink Shared Channel), or a CSI-RS (Channel Status Information Reference Signal) beam. By operating the sweep control unit 133 in this manner, the transmission timing of the SSB beam that does not contribute to communication between the radio station 1 and the radio terminal 2 is effectively utilized, and the actual communication capacity in the radio communication system S is increased.

The sweep control unit 133 may set the second timing, at which the radio station beam is not transmitted, to the timing at which the terminal beam is received from the radio terminal 2. In this case, the sweep control unit 133 controls the beam receiving unit 112 to receive the terminal beam transmitted from the radio terminal at the second timing.

To enable the wireless terminal 2 to transmit the terminal beam at the second timing, the sweep control unit 133 may transmit information indicating the second timing at which the terminal beam can be transmitted to the wireless terminal 2 via the communication unit 11 or via another communication medium such as Wi-Fi (registered trademark). The information indicating the second timing is, for example, a time slot number. By operating the sweep control unit 133 in this manner, it is possible to increase the communication capacity of the uplink.

[Processing flow of wireless station 1]
Fig. 5 is a flowchart showing the flow of processing in the wireless station 1. The flowchart shown in Fig. 5 starts from the point in time when the wireless station 1 starts its operation.

First, the sweep control unit 133 controls the beam transmission unit 111 to transmit a radio station beam at an initially set timing (S1). The initially set timing is any timing at which the radio station beam can be transmitted.

Then, the direction estimation unit 131 estimates the direction of the wireless terminal 2 based on the direction in which the terminal beam was received from the wireless terminal 2 (S2). The range determination unit 132 determines a terminal direction range, which is the range of directions in which the terminal exists, based on the directions of multiple wireless terminals 2 estimated by the direction estimation unit 131 (S3). The range determination unit 132 notifies the sweep control unit 133 that the terminal direction range has been determined. The range determination unit 132 also stores the determined terminal direction range in the storage unit 12.

When the sweep control unit 133 receives notification from the range determination unit 132 that the terminal orientation range has been determined, it compares the terminal orientation range stored in the storage unit 12 with the determined terminal orientation range (S4). If the sweep control unit 133 determines that the terminal orientation range has been changed (YES in S4), it changes the timing for transmitting the radio station beam (S5). Specifically, the sweep control unit 133 excludes the timing corresponding to the orientation not included in the terminal orientation range from the timing for transmitting the radio station beam. If the sweep control unit 133 determines that the terminal orientation range has not been changed (NO in S4), it does not change the timing for transmitting the radio station beam.

The control unit 13 repeats the processes from S2 to S5 until an operation to end the operation of transmitting the radio station beam is received (NO in S6).

[Effects of the wireless station 1 according to the first embodiment]
As described above, the wireless station 1 includes the direction estimation unit 131 that estimates one or more directions corresponding to one or more wireless terminals 2, the range determination unit 132 that determines a terminal direction range including the one or more directions estimated by the direction estimation unit 131, and the sweep control unit 133 that controls the beam transmission unit 111 to transmit a wireless station beam at one or more first timings corresponding to one or more directions included in the terminal direction range and not to transmit a wireless station beam at one or more second timings corresponding to a range other than the terminal direction range. By configuring the wireless station 1 in this way, the beam transmission unit 111 does not transmit a wireless station beam (e.g., an SSB beam) at a timing corresponding to a direction in which no wireless terminal 2 exists, thereby preventing the consumption of unnecessary resources that do not contribute to communication between the wireless station 1 and the wireless terminal 2.

Second Embodiment
6 is a diagram showing the configuration of a wireless station 1A according to the second embodiment. In the wireless station 1 according to the first embodiment, when a wireless terminal 2 is present, the direction estimated by the direction estimation unit 131 is set as the terminal direction range, but an error may occur in the direction estimated by the direction estimation unit 131. Therefore, the wireless station 1A is characterized in that it determines the terminal direction range taking the error into consideration.

As shown in FIG. 6, wireless station 1A differs from wireless station 1 shown in FIG. 4 in that the control unit 13 further includes a moving speed determination unit 134 and a calculation unit 135, but is otherwise the same. The following description will focus on the differences from wireless station 1.

The moving speed determination unit 134 determines the moving speed of the wireless terminal 2 at multiple points in time based on the relationship between the multiple directions in which the wireless terminal 2 was present and the multiple times that are estimated by the direction estimation unit 131 at multiple times and stored in the memory unit 12. Specifically, the moving speed determination unit 134 calculates the moving speed relative to other wireless stations using the following formula (2).

Here, Δt is the time interval during which the orientation of the wireless terminal 2 is stored, N is the number of orientations included in the orientation history data, and θ _i is the orientation at the i-th time.

In this case, the direction estimation unit 131 estimates the direction at the next time by the following equation (3).

The calculation unit 135 calculates a variation value indicating the magnitude of variation in multiple moving speeds corresponding to multiple time points. The variation value is expressed by a statistical value such as the variance or standard deviation of the moving speeds, for example.

The calculation unit 135 calculates the standard deviation as a variation value, for example, by the following formula (4).
Here, N is the number of past directions used to calculate the dispersion value, v _i is the moving speed at time i, and v _a is the average moving speed.

The range determination unit 132 estimates the terminal orientation range of the wireless terminal 2 at the next time based on the previous orientation of the wireless terminal 2, the movement speed identified by the movement speed identification unit 134, and the variation value. The range determination unit 132 estimates the position of other wireless stations at the next time based on, for example, the previous orientation of the wireless terminal 2 and the latest movement speed identified by the movement speed identification unit 134, and calculates the terminal orientation range taking into account the error based on the position to be estimated and the variation value.

Specifically, the range determination unit 132 estimates the error range of the azimuth of another wireless station at the next time, for example, using the following equation (5).
The range determination unit 132 determines the terminal orientation range taking the error into consideration by adding the error range calculated by formula (5) to the orientation at the next time calculated by formula (3). The range determination unit 132 notifies the determined terminal orientation range to the sweep control unit 133. The sweep control unit 133 controls the beam transmission unit 111 and the beam reception unit 112 based on the notified terminal orientation range in the same way as the wireless station 1 of the first embodiment.

[Effects of the wireless station 1A of the second embodiment]
As described above, the sweep control unit 133 of the wireless station 1A estimates the direction of the wireless terminal 2 at the next time, and controls the communication unit 11 using the terminal direction range that takes into account the error included in the estimated direction. By configuring the wireless station 1A in this way, even when the wireless terminal 2 moves, the wireless station 1A can transmit a wireless station beam at a timing corresponding to the direction in which the wireless terminal 2 is present, and can avoid transmitting a wireless station beam at a timing corresponding to the direction in which the wireless terminal 2 is not present.

Furthermore, this invention will make it possible to contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is "Build resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation and infrastructure."

Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination also has the effect of the original embodiment.

REFERENCE SIGNS LIST 1 Wireless station 2 Wireless terminal 11 Communication unit 12 Storage unit 13 Control unit 111 Beam transmission unit 112 Beam reception unit 131 Direction estimation unit 132 Range determination unit 133 Sweep control unit 134 Travel speed identification unit 135 Calculation unit

Claims (5)

a beam transmission unit that transmits a radio station beam toward one or more radio terminals while changing an orientation at a predetermined period;
a beam receiving unit that receives a terminal beam from the one or more wireless terminals after the beam transmitting unit transmits the wireless station beam;
an orientation estimation unit that estimates one or more orientations corresponding to the one or more wireless terminals;
a range determination unit that determines a terminal direction range including the one or more directions estimated by the direction estimation unit;
a sweep control unit that controls the beam transmission unit to transmit the radio station beam at one or more first timings corresponding to one or more directions included in the terminal direction range, and not to transmit the radio station beam at one or more second timings corresponding to a range other than the terminal direction range;
A radio station having the following: the sweep control unit controls the beam receiving unit to receive the terminal beam transmitted from the wireless terminal at the second timing.
The radio station according to claim 1. A storage unit that stores the direction of the wireless terminal in association with time,
the sweep control unit controls the beam transmission unit to transmit the radio station beam to a range excluding the azimuth of the radio terminal that is not stored in the storage unit for a predetermined period of time.
The radio station according to claim 1. a moving speed determination unit that determines a moving speed of a wireless terminal relative to the wireless station;
A calculation unit that calculates a variation value indicating a magnitude of variation of a plurality of the moving speeds corresponding to a plurality of time points;
a determination unit that determines the terminal direction range at the next time based on the direction of the terminal beam that the beam receiving unit has just received from the wireless terminal, the moving speed, and the dispersion value;
Further comprising
A radio station according to any one of claims 1 to 3 . The computer executes
transmitting a radio station beam directed to one or more radio terminals to a beam transmitting unit while changing a direction at a predetermined period;
receiving a terminal beam from the wireless terminal after transmitting the wireless station beam;
estimating one or more orientations corresponding to the one or more wireless terminals;
determining a terminal orientation range including the estimated one or more orientations;
controlling the beam transmission unit to transmit the radio station beam at one or more first timings corresponding to one or more directions included in the terminal direction range, and not to transmit the radio station beam at one or more second timings corresponding to a range other than the terminal direction range;
A communication method comprising:

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