Wireless communication device

Abstract

In the present invention, spatial multiplex transmission is performed between a mobile radio station which is equipped with a plurality of antennas and which moves and a terrestrial radio station which includes a plurality of terrestrial antennas. A wireless communication device which functions as the mobile radio station comprises a processing circuit. By mechanically driving a plurality of antennas, the processing circuit mechanically performs rough adjustment to direct the orientation directions of the plurality of antennas toward the terrestrial radio station. In addition, through weight control of reception signals of the plurality of antennas, the processing circuit performs fine adjustment to direct the orientation directions of the plurality of antennas toward the plurality of terrestrial antennas.

Description

wireless communication device

[0001] The present disclosure relates to a wireless communication device that functions as a mobile wireless station equipped with a plurality of antennas and that performs spatial multiplexing transmission with a terrestrial wireless station including a plurality of terrestrial antennas.

[0002] Non-Patent Document 1 proposes the use of MIMO (Multiple-Input Multiple Output) transmission when conducting wireless communication between a satellite and a terrestrial radio station. MIMO transmission enables an expansion of the communication capacity of the satellite feeder link. However, when MIMO transmission is applied to satellite communications, the satellite and the terrestrial radio station are in a line-of-sight environment, which results in high spatial correlation, making it difficult to properly separate signals. In this regard, Non-Patent Document 1 states that antenna placement is an important factor in improving communication capacity in a line-of-sight environment. In communications with long transmission and reception distances in a line-of-sight environment such as satellite communications, a low-correlation channel can be formed by increasing the antenna distance between the terrestrial radio station and a single satellite.

[0003] One form of MIMO transmission in satellite communications (hereafter referred to as satellite MIMO transmission) is a technology that achieves high capacity by equipping a satellite with multiple antennas to form multiple beams and then transmitting the signals in parallel to multiple antennas at terrestrial radio stations. This technology requires a satellite antenna that can form multiple beams and has pointing control. Satellite antenna pointing control methods can be broadly divided into mechanically driven tracking methods and electronic scanning tracking methods.

[0004] Non-Patent Document 2 discloses a tracking method using mechanical drive for satellite antennas. A mechanical drive tracking method involves adjusting the angle of a single antenna with high directivity, such as a parabolic antenna, to mechanically control the direction of the antenna relative to the receiving station. Because the target of mechanical drive is a single antenna, this method has the advantages of low cost and low power consumption. On the other hand, forming multiple beams requires the installation of multiple antennas on a satellite. However, due to limitations on the area available for mounting antennas on a satellite, it is necessary to miniaturize each individual antenna. Miniaturizing an antenna reduces the antenna gain of each antenna, narrowing the conditions for validating a link calculation.

[0005] Non-Patent Document 3 discloses a tracking method using electronic scanning. The electronic scanning tracking method is a method for controlling the amplitude and phase excitation coefficients of each array element in an array antenna equipped with a large number of antenna elements with wide directivity so that radio waves synthesized across all elements are propagated with high power in the desired direction. Since an array antenna is composed of a large number of small antenna elements, it is possible to form multiple beams with a single array antenna. With the electronic scanning tracking method, satellite MIMO transmission can be achieved with a single array antenna, eliminating the need for antenna miniaturization due to mounting constraints such as with mechanical drive. However, this tracking method requires the same number of amplifiers as the antenna elements, and the more elements in the array antenna, the greater the number of amplifiers required. Therefore, the electronic scanning tracking method has the problem of consuming significantly more power than the mechanical drive tracking method.

[0006] A. Knopp, R.T. Schwarz, D. Ogermann, C.A. Hofmann and B. Lankl, "Satellite System Design Examples for Maximum MIMO Spectral Efficiency in LOS Channels," IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008, pp. 1-6. T. Ueno, S. Ukawa, M. Sugita, T. Suzuki, T. Shima, and Y. Arikawa, "ALOS-2 On-Orbit Evaluation Results of Satellite Attitude / Antenna Coordinated Control and Antenna Alignment Error Estimation," Proceedings of the 57th Joint Conference on Automatic Control Systems, 2014, Vol. 57, Session ID 3A01-2, pp. 1882-1887, November 2014. T. Takahashi et al., "On-Board Calibration Methods for Mechanical Distortions of Satellite Phased Array Antennas," in IEEE Transactions on Antennas and Propagation, vol. 60, no. 3, pp. 1362-1372, March 2012, doi: 10.1109 / TAP.2011.2180303.

[0007] The present disclosure has been made in view of the above-mentioned problems, and one object of the present disclosure is to provide a wireless communication device that can achieve spatial multiplexing transmission with terrestrial wireless stations while suppressing the installation scale of antennas and the power consumption of the antennas.

[0008] The present disclosure provides a wireless communication device that functions as a mobile wireless station equipped with multiple antennas and performs spatial multiplexing transmission with a terrestrial wireless station including multiple terrestrial antennas, and that includes a processing circuit. The processing circuit is configured to mechanically coarsely adjust the direction of orientation of the multiple antennas toward the terrestrial wireless station by mechanically driving the multiple antennas, and to finely adjust the direction of orientation of the multiple antennas toward the terrestrial antennas by weight control of received signals from the multiple antennas.

[0009] According to the above-mentioned wireless communication device, the antenna direction is controlled by combining coarse adjustment by mechanically driving the antenna with fine adjustment by weight control, thereby realizing spatial multiplexing transmission between terrestrial wireless stations while reducing the antenna installation size and power consumption.

[0010] FIG. 1 is a diagram illustrating an overview of a wireless communication system according to an embodiment of the present disclosure; FIG. 2 is a diagram illustrating a configuration of a wireless communication system according to an embodiment of the present disclosure; FIG. 3 is a diagram illustrating pointing control of a satellite antenna by a wireless communication device according to an embodiment of the present disclosure; FIG. 4 is a diagram illustrating pointing control of a satellite antenna by a wireless communication device according to an embodiment of the present disclosure; FIG. 5 is a flowchart illustrating a flow of processing executed in a wireless communication system according to an embodiment of the present disclosure; and FIG. 6 is a diagram illustrating a first modified example of pointing control of a satellite antenna by a wireless communication device according to an embodiment of the present disclosure.

[0011] 1. Overview of Wireless Communication System Fig. 1 shows a configuration in which a wireless communication system according to an embodiment of the present disclosure is implemented using a mobile station (MS) 10 and a terrestrial radio station (GW) 30. In this embodiment, the mobile station 10 is specifically a low Earth orbit (LEO) satellite. However, the mobile station 10 is not limited to a LEO satellite and may be, for example, an unmanned aerial vehicle.

[0012] The mobile radio station 10 is equipped with two satellite antennas 11-1 and 11-2. Hereinafter, when there is no need to distinguish between the two satellite antennas, the subscripts of the reference numerals will be omitted and they will be referred to as satellite antennas 11. In this embodiment, the satellite antennas 11 are each configured as a parabolic antenna equipped with an independent mechanical tracking mechanism. Note that the number of satellite antennas 11 is not limited to two, and may be two or more.

[0013] Two terrestrial antennas 31-1 and 31-2 are connected by wire to the terrestrial radio station 30. Hereinafter, when there is no need to distinguish between the two terrestrial antennas, the subscripts of the reference numerals will be omitted and they will be referred to as terrestrial antennas 31. Like the satellite antenna 11, the terrestrial antenna 31 is also configured as a parabolic antenna equipped with a mechanical tracking mechanism. Note that the number of terrestrial antennas 31 is not limited to two, and may be two or more.

[0014] The LEO satellites constituting the mobile radio station 10 orbit the Earth in a low earth orbit at an altitude of, for example, 2000 km or less. Unlike geostationary orbit satellites, LEO satellites are characterized by being constantly moving as seen from the Earth. Therefore, to provide continuous service using LEO satellites, it is necessary to launch multiple satellites and provide comprehensive coverage to the entire service area. In particular, to provide global services, it is essential to deploy a satellite constellation orbiting the Earth.

[0015] In order to increase the communication capacity of terrestrial terminals or the number of terrestrial terminals that can be accommodated in services using LEO satellites, it is necessary to increase the capacity of the feeder link lines used for data communication. In order to increase the capacity of the lines, it is desirable to use high frequency bands that enable wideband communication. In this embodiment, for example, the ka band in the 20 to 30 GHz band or the Q / V band in the 40 to 50 GHz band is used.

[0016] Furthermore, the wireless communication system of this embodiment utilizes MIMO technology as an additional method for increasing the capacity of the link. However, when MIMO transmission is performed between a satellite and a terrestrial wireless station, a line-of-sight environment is formed between the two, which increases spatial correlation and may result in inaccurate separation of multiplexed transmitted signals. Therefore, in the wireless communication system of this embodiment, multiple terrestrial antennas 31 communicating with a single mobile wireless station 10 are arranged at large distances. With this arrangement, multiple channels with low correlation between the MS 10 and the multiple terrestrial antennas 31 are formed, thereby increasing the capacity of the link.

[0017] To achieve satellite MIMO transmission, satellite antennas require pointing direction control. Satellite antenna pointing control methods can be broadly divided into mechanically driven tracking methods and electronic scanning tracking methods. The former has the disadvantage of requiring a large antenna installation size, while the latter has the disadvantage of requiring a large antenna power consumption. Therefore, the wireless communication system of this embodiment combines the mechanically driven tracking method and the electronic scanning tracking method to compensate for the respective disadvantages, thereby making it possible to reduce both the antenna installation size and the antenna power consumption. An overview of satellite antenna pointing control in the wireless communication system of this embodiment will be described below.

[0018] The satellite antenna pointing control is performed by a mobile radio station 10 serving as a radio communication device. The mobile radio station 10 mechanically drives two satellite antennas 11-1 and 11-2 in the same direction. In other words, the satellite antennas 11-1 and 11-2 are mechanically driven so that they always point in the same direction. The satellite antennas 11-1 and 11-2 can be mechanically driven in both elevation and azimuth. The mobile radio station 10 first mechanically drives the satellite antennas 11-1 and 11-2 toward the estimated direction of the terrestrial communication station 30, and roughly adjusts the pointing direction of the satellite antennas 11-1 and 11-2 so that the terrestrial communication station 30 is within the antenna pattern 100 of the satellite antennas 11-1 and 11-2 as a whole.

[0019] The mobile radio station 10 then fine-tunes the direction of the satellite antennas 11-1 and 11-2 toward the respective ground antennas 31-1 and 31-2 by weight control of the signals received by the satellite antennas 11-1 and 11-2. That is, electronic scanning by the two satellite antennas 11-1 and 11-2 forms a beam 210 with an antenna pattern directed toward the terrestrial antenna 31-1 and a beam 220 with an antenna pattern directed toward the terrestrial antenna 31-2. Note that although the example shown in Figure 2 has two satellite antennas 11 and two terrestrial antennas 31, increasing the number of antennas allows for spatial multiplexing transmission that is multiplexed accordingly.

[0020] 2. Configuration of the Wireless Communication System The configuration of the wireless communication system for realizing the above-mentioned pointing control of the satellite antenna will be explained with reference to FIG.

[0021] Figure 2 is a block diagram for functionally explaining the configuration of the mobile radio station 10 and the terrestrial radio station 30. Each function represented by a block in Figure 2 is implemented in a processing circuit including a general-purpose processor, an application-specific processor, an integrated circuit, an ASIC, an FPGA, a CPU, a conventional circuit, and / or a combination thereof, programmed to realize that function. The processing circuit includes a memory in which instruction code and data are stored. Each function of the mobile radio station 10 and the terrestrial radio station 30 described below is realized by the execution of instruction code stored in the respective memory in the respective processing circuit.

[0022] First, the function for controlling the pointing of the satellite antennas 11-1 and 11-2 provided in the mobile radio station 10 will be described. The mobile radio station 10 has the following blocks for controlling the pointing of the satellite antenna 11. "Signal receiving unit 12-1": A block for receiving signals that have arrived at the satellite antenna 11-1. "Signal receiving unit 12-2": A block for receiving signals that have arrived at the satellite antenna 11-2. "Reception amplitude and phase control unit 13": A block for performing maximum ratio combining by multiplying each signal received by the signal receiving units 12-1 and 12-2 by an excitation coefficient (reception weight) for amplitude and phase for weight control. "Demodulation unit 14": A block for demodulating the signal that has been subjected to maximum ratio combining by the reception amplitude and phase control unit 13 to restore the data. "Modulation unit 15": A block for modulating the data to be transmitted into a signal. "Transmission amplitude and phase control unit 16": A block for multiplying the signal obtained by modulation by the modulation unit 34 by amplitude and phase excitation coefficients (transmission weights) for in-phase synthesis of the transmission signals from the satellite antennas 11-1 and 11-2. "Signal transmission unit 17-1": A block for transmitting the signal multiplied by the transmission weight by the transmission amplitude and phase control unit 16 from the satellite antenna 11-1. "Signal transmission unit 17-2": A block for transmitting the signal multiplied by the transmission weight by the transmission amplitude and phase control unit 16 from the satellite antenna 11-2. "Station position estimation unit 18": A block for estimating the position information of the mobile radio station 10 and the terrestrial radio station 30. The position information of the mobile radio station 10 can be estimated from satellite orbit information and GPS satellites. The position of the terrestrial radio station 30 is known to the mobile radio station 10. "Host station attitude estimation unit 19": A block for estimating the attitude information of the mobile radio station 10 itself. The attitude information of the mobile radio station 10 can be estimated from a signal from a gyro sensor provided in the mobile radio station 10. "Received power calculation unit 20": A block for calculating the power of each signal received by the signal receiving units 12-1 and 12-2."Direction control unit 21": A block for controlling the direction of direction of the satellite antennas 11-1 and 11-2 based on the position information estimated by the station position estimation unit 18, the attitude information estimated by the station attitude estimation unit 19, and the received power calculated by the received power calculation unit 20. "Antenna driving unit 22-1": A block for mechanically driving the satellite antenna 11-1 in accordance with instructions from the direction control unit 21. "Antenna driving unit 22-2": A block for mechanically driving the satellite antenna 11-2 in accordance with instructions from the direction control unit 21.

[0023] Antenna pointing control is also performed by the terrestrial radio station 30. The function for pointing control of the terrestrial antennas 31-1 and 31-2 provided in the terrestrial radio station 30 will be described. The terrestrial radio station 30 has the following blocks as functions for pointing control of the terrestrial antenna 31. "Signal receiving unit 32": A block for receiving signals that have reached the terrestrial antennas 31-1 and 31-2. "Demodulation unit 33": A block for demodulating signals received by the signal receiving unit 32 to restore the data. "Modulation unit 34": A block for modulating data to be transmitted into signals. "Signal transmitting unit 35": A block for transmitting signals obtained by modulation by the modulation unit 34 from the terrestrial antennas 31-1 and 31-2. "Received power calculation unit 36": A block for calculating the power of the signal received by the signal receiving unit 32. "Direction control unit 37": A block for controlling the direction of the terrestrial antennas 31-1 and 31-2 based on the received power calculated by the received power calculation unit 36. "Antenna driving unit 38-1": A block for mechanically driving the ground antenna 31-1 in accordance with instructions from the directivity direction control unit 37. "Antenna driving unit 38-2": A block for mechanically driving the ground antenna 31-2 in accordance with instructions from the directivity direction control unit 37.

[0024] 3. Details of Satellite Antenna Pointing Control The details of satellite antenna pointing control that can be realized by the wireless communication system configured as described above will be explained with reference to FIGS.

[0025] A mobile radio station 10 serving as a wireless communication device uses one of two terrestrial antennas 31-1, 31-2 as a reference antenna and mechanically drives satellite antennas 11-1, 11-2 so that they point toward the reference antenna. In the example shown in FIG. 3 , the terrestrial antenna 31-1 is set as the reference antenna. The pointing direction control unit 21 of the mobile radio station 10 controls the drive of the satellite antennas 11-1, 11-2 so that they point toward the terrestrial antenna 31-1 based on the relative positional relationship between the mobile radio station 10 and the terrestrial radio station 30 estimated by the station position estimation unit 18 and the attitude of the mobile radio station 10 estimated by the station attitude estimation unit 19. The satellite antennas 11-1 and 11-2 may have their respective drive motors coordinated so that they always point in the same direction, or may be connected by a mechanical mechanism so that they always point in the same direction.

[0026] By mechanically driving the satellite antennas 11-1 and 11-2 as described above, the pointing directions of the satellite antennas 11-1 and 11-2 are roughly adjusted so that they track the terrestrial antenna 31-1, which is the reference antenna. As a result, the antenna pattern 100 of the satellite antennas 11-1 and 11-2 as a whole is set to cover the terrestrial antennas 31-1 and 31-2, with the terrestrial antenna 31-1, which is the reference antenna, as the center.

[0027] Next, the mobile radio station 10, which serves as a wireless communication device, performs weight control on the received signals of the satellite antennas 11-1 and 11-2 so as to maximize the power in the direction of pointing. In the example shown in FIG. 3, the pointing direction is the direction of the terrestrial antenna 31-1, which is the reference antenna. The reception amplitude and phase control unit 13 of the mobile radio station 10 performs in-phase synthesis of the received signals of the satellite antennas 11-1 and 11-2 so as to reinforce the main beam 210 directed toward the terrestrial antenna 31-1. Furthermore, the transmission amplitude and phase control unit 16 calculates transmission weights based on the reception weights, taking into account the frequency difference with the received signals, and controls the transmission beams output from the satellite antennas 11-1 and 11-2 by phase control using the transmission weights.

[0028] The pointing direction control unit 21 may control the pointing direction of the satellite antennas 11-1 and 11-2 based on the received power acquired from the received power calculation unit 20, instead of the estimation results from the station position estimation unit 18 and the station attitude estimation unit 19. For example, a method such as conical scan or step track may be used to make the pointing direction of the satellite antennas 11-1 and 11-2 follow the direction that maximizes the received power calculated by the received power calculation unit 20. Furthermore, the change in the pointing direction of the satellite antennas 11-1 and 11-2 may be calculated from a change in phase due to electronic scanning.

[0029] Next, the mobile radio station 10 as a radio communication device forms a beam 220 toward the terrestrial antenna 31-2, as shown in Figure 4. At this time, the orientation of the mechanically driven satellite antennas 11-1 and 11-2 remains directed toward the terrestrial antenna 31-1, and the beam 220 is formed independently of the beam 210 by weight control of the received signals of the satellite antennas 11-1 and 11-2.

[0030] However, since beam 210 and beam 220 are formed independently, there is a possibility that they may interfere with each other at terrestrial radio station 30. To realize spatial multiplexing transmission that eliminates the effects of interference, some form of interference compensation is necessary. Below, an overview of general reception interference compensation for eliminating the effects of interference will be described.

[0031] 4, there are four channel components (2 x 2) between the two terrestrial antennas 31-1 and 31-2 and the two satellite antennas 11-1 and 11-2. If the terrestrial radio station 30 is the receiving side, these channel components can be expressed as follows:

[0032] After estimating these four channel coefficients, the terrestrial radio station 30 obtains the following channel estimation matrix based on the results:

[0033] Thereafter, the terrestrial radio station 30 generates a pseudo-inverse matrix of the above channel estimation matrix using, for example, a ZF (Zero Forcing) algorithm, as follows:

[0034] By multiplying the received signal by the pseudo-inverse matrix generated in this way, it becomes possible to cancel the interference component.

[0035] After beamforming is established and channel estimation is completed, beamforming to the terrestrial antenna 31-1 may be performed using a method other than in-phase combining, provided that a sufficient margin of carrier-to-noise ratio (CNR) is secured. For example, the ZF algorithm may be used, or beamforming may be performed so as to improve signal-to-interference-plus-noise ratio (SINR) by precoding transmission such as minimum mean-square error (MMSE) or eigenmode transmission.

[0036] 4. Processing Executed in the Wireless Communication System The above-mentioned pointing control of the satellite antenna is executed as part of a series of processes executed by the wireless communication system. The flow of the processing executed in the wireless communication system of this embodiment will be explained below with reference to Figure 5. Figure 5 is a flowchart showing the flow of the processing executed by the mobile wireless station 10 and the terrestrial wireless station 30.

[0037] The mobile radio station 10 first predicts its own location information and the location information of the terrestrial radio station 30 with which communication is to be established (step S101). The mobile radio station 10 also estimates its own attitude information (step S102). The order of estimation of the location information and the attitude information may be reversed or may be simultaneous.

[0038] Next, the mobile radio station 10 roughly adjusts the pointing direction of the satellite antenna 11 based on the estimated position information and attitude information (step S103). The rough adjustment of the pointing direction of the satellite antenna 11 is performed mechanically, and the elevation angle and azimuth angle are mechanically controlled so that the satellite antenna 11 points in the direction of the terrestrial radio station 30.

[0039] Next, the mobile radio station 10 transmits a beacon signal to the terrestrial radio station 30 (step S104). Specifically, a beacon signal is sent from each satellite antenna 11 to each terrestrial antenna 31 with which a one-to-one relationship should be established.

[0040] After transmitting the beacon signal, the mobile radio station 10 waits for a transmission from the terrestrial radio station 30, and the signal transmitted from the terrestrial radio station 30 is received by the satellite antenna 11 (step S105). The signal received by the satellite antenna 11 includes a data signal and a beacon signal. Then, the spatial multiplexing transmission channel is estimated based on the detection of the beacon signal, i.e., the unique identification signal (step S106).

[0041] Next, the mobile radio station 10 performs fine adjustment of the pointing direction of the satellite antenna 11 by weight control of the received signal of the satellite antenna 11 (step 107). The coarse adjustment of pointing direction performed in the above-mentioned step S103 involves mechanically adjusting the elevation angle and azimuth angle of each of the multiple satellite antennas 11. In contrast, the fine adjustment of pointing direction performed in this step involves controlling the excitation coefficients of the amplitude and phase of each satellite antenna 11 so that the radio waves synthesized from all the satellite antennas 11 are propagated with high power in the desired direction.

[0042] Next, the mobile radio station 10 multiplies the received signal from the satellite antenna 11 by an excitation coefficient for amplitude and phase that combines the received signal at the maximum ratio, i.e., a receiving weight (step 108).Then, the received signal multiplied by the receiving weight is demodulated (step S109) and data is restored (step S110) in sequence.

[0043] The mobile radio station 10 also determines which satellite antennas 11 are capable of transmitting based on the received beacon signal. Then, the number of beamforming operations and beamforming directions that can achieve the maximum transmission capacity are calculated based on the satellite antennas 11 that are capable of transmitting, and amplitude and phase excitation coefficients for beamforming for the terrestrial antenna 31 are calculated (step S111). Next, the amplitude and phase excitation coefficients for in-phase synthesis when transmitting a signal, i.e., transmission weights, are calculated (step S112).

[0044] Thereafter, the mobile radio station 10 performs a data generation process (step S113), modulates the data, and multiplies the modulated signal by the amplitude and phase excitation coefficients (step S114).Then, the signal multiplied by the amplitude and phase excitation coefficients is transmitted from each satellite antenna 11 (step S115).

[0045] First, the terrestrial radio station 30 predicts its own location information and the location information of the mobile radio station 10 with which communication is to be established (step S201).

[0046] Next, the terrestrial radio station 30 roughly adjusts the direction of the terrestrial antenna 31 based on the estimated position information (step S202). The rough adjustment of the direction of the terrestrial antenna 31 is performed mechanically, and the elevation angle and azimuth angle are mechanically controlled to point toward the estimated position of the mobile radio station 10.

[0047] The terrestrial radio station 30 waits for the transmission of a beacon signal or a data signal from the mobile radio station 10, and the signal transmitted from the mobile radio station 10 is received by the terrestrial antenna 31 (step S203). Then, the direction of the terrestrial antenna 31 is finely adjusted by weight control of the received signal at the terrestrial antenna 31 (step 204).

[0048] If the signal received in step S203 is a beacon signal, the terrestrial radio station 30 transmits the beacon signal from the terrestrial antenna that received the signal (step S205).

[0049] If the signal received in step S203 is a data signal, the terrestrial radio station 30 performs channel estimation (step S206) based on the signal received by each terrestrial antenna 31. Then, equalization (step S207), demodulation (step S208), and data recovery (step S209) of the received signal are sequentially performed.

[0050] Also, if the signal received in step S203 is a data signal, the terrestrial radio station 30 performs a data generation process (step S210), and the signal obtained by modulating the data is transmitted from at least one of the terrestrial antennas 31 (step S216).

[0051] As described above, according to the wireless communication system of this embodiment, the direction of the satellite antenna is controlled by combining coarse adjustment by mechanically driving the satellite antenna with fine adjustment by weight control. This makes it possible to realize spatial multiplexing transmission between the mobile wireless station 10 and the terrestrial wireless station 30 while suppressing the installation scale and power consumption of the satellite antenna.

[0052] 5. Modifications Figure 6 is a diagram illustrating a first modification of satellite antenna pointing control by a mobile radio station 10 serving as a wireless communication device. In this first modification, after the formation of beam 210 toward terrestrial antenna 31-1 and beam 220 toward terrestrial antenna 31-2 is established and channel estimation for spatial multiplexing transmission is completed, the conditions for co-directional tracking of mechanically driven satellite antennas 11-1 and 11-2 are changed, provided that a sufficient CNR margin is secured. For example, the pointing direction of mechanically driven satellite antenna 11-1 remains the same as that of terrestrial antenna 31-1, while the pointing direction of mechanically driven satellite antenna 11-2 is changed to that of terrestrial antenna 31-2. In other words, as in the example shown in Figure 6, the antenna pattern 110 of satellite antenna 11-1 is centered on terrestrial antenna 31-1 and covers terrestrial antennas 31-1 and 31-2. On the other hand, the antenna pattern 120 of the satellite antenna 11-2 is centered on the terrestrial antenna 31-2 and covers the terrestrial antennas 31-1 and 31-2. By adjusting the mechanical pointing directions of the satellite antennas 11-1 and 11-2 in this way, it is possible to expect an improvement in the channel capacity of spatial multiplexing transmission, depending on the conditions.

[0053] In the second variant of satellite antenna pointing control by the mobile radio station 10, first, as in the above embodiment, the satellite antenna is mechanically driven to roughly adjust its pointing direction, and then weight-controlled to finely adjust its pointing direction. Then, utilizing the satellite's ability to predict its orbit, the satellite's future position is predicted and the transmission capacity within a certain period of time, for example, within the satellite antenna's footprint, is calculated. If the prediction of the future satellite's position differs, the results of the stationary antenna's pointing control will also differ. The transmission capacity calculation reflects the results of the different pointing controls, and the satellite antenna is mechanically driven so that the beam is directed in the direction that maximizes the transmission capacity.

[0054] 10 Mobile radio station (wireless communication device) 11-1, 11-2 Satellite antenna 30 Terrestrial radio station 31-1, 31-2 Terrestrial antenna

Claims

1. A wireless communication device equipped with multiple antennas and functioning as a mobile wireless station that moves and performs spatial multiplexing transmission with a terrestrial wireless station that includes multiple terrestrial antennas, comprising a processing circuit, wherein the processing circuit is configured to mechanically coarsely adjust the direction of orientation of the multiple antennas toward the terrestrial wireless station by mechanically driving the multiple antennas, and to finely adjust the direction of orientation of the multiple antennas toward the multiple terrestrial antennas by weight control of the received signals of the multiple antennas.

2. A wireless communication device according to claim 1, wherein the processing circuit is configured to multiply the transmission signals of each of the plurality of antennas by the transmission weight obtained by the weight control.

3. A wireless communication device according to claim 1, characterized in that the processing circuit is configured to: mechanically roughly adjust the direction of orientation of the plurality of antennas so as to track a reference antenna among the plurality of terrestrial antennas possessed by the terrestrial radio station; and form a beam directed toward the reference antenna and a beam directed toward another terrestrial antenna among the plurality of terrestrial antennas by finely adjusting the direction of orientation of the plurality of antennas through the weight control.

4. A wireless communication device according to claim 1, characterized in that the processing circuit is configured to determine the direction of orientation of the plurality of antennas, which are roughly adjusted by mechanical drive, based on the relative position and attitude of the own station with respect to the terrestrial radio station, or based on the received power of the signals received by the plurality of antennas.

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