JP5552180B2 - Transmitting apparatus and transmitting / receiving method - Google Patents

Description

  The present invention relates to a transmission apparatus and a transmission / reception method for simultaneously transmitting signals to a plurality of communication apparatuses.

In a wireless communication system such as a conventional cellular system, there is a method for increasing transmission capacity by performing space division multiple access (SDMA) using a multi-antenna transmission / reception technology (MIMO: Multiple Input Multiple Output). Proposed.
In SDMA, by using the directivity of the antenna of the base station apparatus, directional beams having different directivities are assigned to a plurality of communication terminals (mobile station apparatuses) separated from each other. By spatially separating communication signals within the communication range, a plurality of communication terminals can transmit and receive simultaneously.

  However, when performing communication by SDMA, it is necessary for the base station apparatus on the transmission side to acquire downlink channel information from the base station apparatus to the communication terminal, and the uplink from the communication terminal to the base station apparatus In a frequency division duplex (FDD) system in which frequencies used for communication in the downlink are different, it is difficult to acquire downlink channel information.

Thus, as one method of acquiring downlink channel information, there is a method of feeding back downlink channel information from a communication terminal to a base station apparatus. However, as the number of antennas and the number of registered communication terminals increase, the amount of information fed back from the communication terminal to the base station apparatus has become a problem. As a method for reducing the amount of information fed back from the communication terminal to the base station apparatus, a multi-user MIMO scheme that feeds back and uses partial channel information has been proposed.
In the random beam forming proposed in Non-Patent Document 1 as one of the multi-user MIMO schemes, first, the base station apparatus uses a unitary matrix to form directional beams that are orthogonal to each other for communication terminals, and performs communication. Transmit to each communication terminal within range. Each communication terminal obtains an effective S / N ratio (ESNR: Effective Signal to Noise Ratio) based on the directional beam transmitted from the base station apparatus, and feeds back the ESNR to the base station apparatus. Thereafter, the base station apparatus allocates resources to the communication terminal with the highest ESNR.

As another method for acquiring downlink channel information, there is a method for estimating an arrival angle of a transmission signal transmitted from a communication terminal based on an uplink reception signal received by a base station apparatus.
As an example, there is a conventional FDD base station apparatus 500 as shown in the schematic block of FIG. In uplink processing by base station apparatus 500 shown in FIG. 6, first, received signals received via antennas 100-1, 100-2,..., 100-M are converted into downconverters 101 for each received antenna. Down-converts. Thereafter, the arrival angle estimation unit 105 estimates the arrival angle for each down-converted received signal, that is, for each communication terminal. In the downlink processing by base station apparatus 500 shown in FIG. 6, first, orthogonal weight calculation section 106 downloads to all communication terminals based on the arrival angle for each communication terminal estimated in uplink processing. A zero-forcing (ZF) weight for transmitting a zero signal in a direction unnecessary for communication so that the beams are orthogonal to each other is calculated. Thereafter, the downlink signal is transmitted after performing a process of multiplying the modulated signal of the transmission data transmitted to the communication terminal by the ZF weight calculated by the orthogonal weight calculation unit 106 for each communication terminal.

C.Jaehak, CS.Hwang, K.Kiho, and KKYoung, “A random beamforming technique in MIMO system exploiting multiuser diversity,” IEEE Journal on Selected Areas in Communications, vol.21, pp.848-855, June 2003 .

  However, in the conventional random beam forming, the transmission signal space used when the base station apparatus on the transmission side forms a directional beam and the transmission signal used when the communication terminal on the reception side forms a directional beam. Therefore, there is a problem in that transmission power of a transmission signal is lost and interference between directional beams occurs.

  In addition, when the method for estimating the arrival angle of a transmission signal transmitted from a communication terminal is applied to a communication terminal having a high correlation of communication channels, an increase in unwanted radiation in a direction other than the target, or dynamics of ZF weights There was a problem that the range would increase.

The present invention has been made on the basis of the above problem recognition, and in downlink communication of a transmission apparatus having a precoding process that does not feed back downlink channel information in multi-antenna transmission / reception, there is a loss of transmission power of a transmission signal. Therefore, an object of the present invention is to provide a transmission apparatus and a transmission / reception method in which interference between directional beams does not occur.
It is another object of the present invention to provide a transmission apparatus and a transmission / reception method that can suppress unnecessary radiation in a non-target direction and increase in the dynamic range of non-orthogonal weights to a communication terminal having a high correlation of communication channels. It is said.

  In order to solve the above-described problem, a transmission device of the present invention includes a plurality of antennas, and a transmission device of a wireless communication system that performs communication with one or more communication devices using a plurality of frequency bands. An apparatus, using the received signal received by the transmitting apparatus, and arrival direction estimating means for estimating an arrival angle that indicates an arrival direction of a transmission signal that exists within a communication range and is transmitted from a partner communication apparatus that is a communication partner. The amount of interference between a transmission beam transmitted to one partner communication device and a transmission beam transmitted to another partner communication device based on the arrival angle of the transmission signal from the partner communication device estimated by the arrival direction estimation means Interference amount estimation means for calculating a variable for estimating the interference amount, and based on the variable for estimating the interference amount calculated by the interference amount estimation means, the interference amount is removed from the transmission signal transmitted to the counterpart communication device. And a transmission having directivity from the transmission signal from which the interference amount has been removed by the interference amount removal unit, based on the arrival angle of the transmission signal from the counterpart communication device estimated by the arrival direction estimation unit. Beam forming means for forming a beam, and the priority of the processing for removing the amount of interference from the transmission signal transmitted to the counterpart communication apparatus is the priority of the transmission signal from the counterpart communication apparatus estimated by the arrival direction estimation means. It is based on the amount of change in the angle of arrival.

  In the transmission apparatus of the present invention, the priority of the process of removing the interference amount from the transmission signal transmitted to the counterpart communication apparatus is such that the priority of the counterpart communication apparatus with a small amount of change in the arrival angle is high, and the arrival angle The priority of the counterpart communication device decreases as the amount of change increases.

In the transmission device of the present invention, the variable for estimating the amount of interference is the estimated signal of each antenna transmitted from one of the plurality of antennas of the transmission device. A weight w (θ _k ) representing a phase difference with respect to the arrival angle θ _k , and the arrival angle θ _k is an arrival angle of the transmission signal from the k-th partner communication device estimated by the arrival direction estimation unit, k Is a positive integer from 1 to K, K is the number of counterpart communication devices, and weight w (θ _k ) is the kth counterpart communication device transmitted from each antenna of the transmission device. The weight multiplied by the signal, and the amount of interference to be removed from the transmission signal transmitted to the kth partner communication device is the weight w (θ _k ) arranged in the priority order of each partner communication device QR decomposition of weight matrix The interference component with respect to the k-the counterpart communication apparatus, which is calculated using the lower triangular matrix obtained Te, characterized in that.

  Further, the transmission / reception method of the present invention is a transmission / reception method of a transmission apparatus of a wireless communication system that includes a plurality of antennas and performs communication with one or more communication apparatuses using a plurality of frequency bands. Using the received signal received by the transmitting apparatus, an arrival direction estimation procedure for estimating an arrival angle indicating an arrival direction of a transmission signal that exists within a communication range and is transmitted from a partner communication apparatus serving as a communication partner; Based on the arrival angle of the transmission signal from the partner communication device estimated by the direction estimation procedure, the amount of interference between the transmission beam transmitted to one partner communication device and the transmission beam transmitted to the other partner communication device is estimated. The interference amount is removed from the transmission signal transmitted to the counterpart communication device based on the interference amount estimation procedure for calculating the variable for the interference and the variable for estimating the interference amount calculated by the interference amount estimation procedure. A transmission beam having directivity from the transmission signal from which the interference amount has been removed by the interference amount removal procedure based on the interference cancellation procedure and the arrival angle of the transmission signal from the counterpart communication device estimated by the arrival direction estimation procedure The priority of processing for removing the amount of interference from the transmission signal transmitted to the counterpart communication device is the arrival of the transmission signal from the counterpart communication device estimated by the arrival direction estimation means. It is based on the amount of change in corners.

According to the present invention, transmission power loss of a transmission signal is formed by forming a directional beam in the direction of a communication apparatus of a communication partner existing within a communication range of the transmission apparatus and removing interference with other communication beams. Therefore, it is possible to provide a transmission apparatus and a transmission / reception method in which interference between directional beams does not occur.
Further, it is possible to provide a transmission apparatus and a transmission / reception method that can suppress unnecessary radiation in an unintended direction and increase in the dynamic range of non-orthogonal weights by removing interference.

It is the figure which showed schematic structure of the multiuser MIMO system by embodiment of this invention. It is a block diagram which shows schematic structure of the base station apparatus in embodiment of this invention. It is the flowchart which showed the process sequence in the base station apparatus of this embodiment. It is the graph which showed the relationship between the transmission direction of the transmission signal which the base station apparatus of this embodiment transmits, and transmission power. It is the flowchart which showed the process sequence which performs scheduling in the base station apparatus of this embodiment. It is the block diagram which showed schematic structure of the conventional base station apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a multiuser MIMO system according to the present embodiment. In FIG. 1, a multi-user MIMO system is installed at a predetermined specific position and can perform communication using a plurality of frequency bands, and communicates using a plurality of frequency bands. Mobile terminals 201 to 20K (K is an integer) that is moved by the owner of the communication terminal (hereinafter, the mobile terminals 201 to 20K are collectively referred to as “mobile terminal 200”). .

The base station apparatus 100 includes a plurality of antennas 100-1, 100-2,..., 100-M (M is an integer), and can transmit and receive simultaneously with a plurality of mobile terminals 200 existing within a communication range. it can. In FIG. 1, the number following the symbol 100 of the antenna of the base station apparatus 100 and subsequent to “-: hyphen” represents the identification number of the antenna in the base station apparatus 100.
For example, the base station apparatus 100 performs transmission / reception with the mobile terminal 201 using the communication frequency band h ₁ , performs transmission / reception with the mobile terminal 202 using the communication frequency band h ₂ , and communicates with the mobile terminal 20K. It performs transmission and reception using a frequency band h _K.

  The mobile terminal 201 includes a plurality of antennas 201-1, 201-2, ..., 201-N (N is an integer), and can transmit and receive signals spatially multiplexed by the MIMO technology. The mobile terminals 202 to 20K have the same configuration as that of the mobile terminal 201, and transmit and receive spatially multiplexed signals. Note that the number following the sign of the antenna of the mobile terminal 200 followed by “-: hyphen” represents the identification number of the antenna in each mobile terminal.

  Next, the communication method in the base station apparatus of this embodiment is demonstrated. FIG. 2 is a block diagram illustrating a schematic configuration of the base station apparatus 100 according to the present embodiment. 2, the base station apparatus 100 includes communication antennas 100-1, 100-2,..., 100-M, a down converter 101, reception processing units 102-1, 102-2,. (Hereinafter referred to as “reception processing unit 102” when any one of the reception processing units is indicated), transmission processing units 103-1, 103-2,..., 103-M (hereinafter referred to as transmission processing unit 102). When one of them is shown, it is referred to as “transmission processing unit 103”), an up converter 104, an arrival angle estimation unit 105, a non-orthogonal weight calculation unit 107, and an interference amount calculation unit 108. The reception processing unit 102 includes an uplink beam forming unit 1021 and a data demodulating unit 1022. The transmission processing unit 103 includes a data modulation unit 1031, a downlink beam forming unit 1032, and an interference removal unit 1033.

  The configuration of base station apparatus 100 is a configuration in which interference amount calculation section 108 and interference cancellation section 1033 in transmission processing section 103 are added to conventional base station apparatus 500 shown in FIG. The non-orthogonal weight calculation unit 107 has the same function as the orthogonal weight calculation unit 106 in the conventional base station apparatus 500 shown in FIG. 6, but in this embodiment, all mobile terminals 200 that perform communication. It is not necessary for the downstream beams to be orthogonal.

  The down-converter 101 converts the received signal from each mobile terminal 200 received via the antenna into a low-frequency signal, and converts the converted received signal into a reception processing unit 102 and an arrival angle estimation unit for each mobile terminal 200. To 105. Down converter 101 has the same function as down converter 101 in conventional base station apparatus 500 shown in FIG.

  The reception processing unit 102 performs processing such as analog-digital conversion, Fourier transform, and data demodulation processing on the low-frequency reception signal input from the down converter 101 to extract reception data, and extracts the extracted reception data. Output to a control device (not shown). Note that the reception processing unit 102 has the same number of antennas as the base station apparatus 100, and performs reception data extraction processing for each antenna. The reception processing unit 102 has the same function as the reception processing unit 102 in the conventional base station apparatus 500 shown in FIG.

  The upstream beam forming unit 1021 performs processing such as analog-digital conversion and Fourier transform on the low-frequency received signal input from the down converter 101 to remove processing for communication compensation included in the received signal. The received data from which processing for communication compensation has been removed is output to the data demodulator 1022. The uplink beam forming section 1021 has the same function as the uplink beam forming section 1021 in the conventional base station apparatus 500 shown in FIG.

  The data demodulating unit 1022 performs demodulation using a predetermined modulation method from the received data from which the processing for communication compensation input from the uplink beam forming unit 1021 is removed, and further compensates for an error code or the like of the received data. The received data is extracted by removing the above process, and the extracted received data is output to a control device (not shown). Data demodulating section 1022 has the same function as data demodulating section 1022 in conventional base station apparatus 500 shown in FIG.

  The arrival angle estimation unit 105 detects, for example, phase information of the received signal observed at each antenna from the low frequency received signal of each mobile terminal 200 input from the down converter 101, and based on the phase difference between the antennas. The direction in which the mobile terminal 200 exists, that is, the arrival angle of the transmission signal transmitted from the mobile terminal 200 is estimated, and the arrival angle estimation result for each mobile terminal 200 is output to the non-orthogonal weight calculation unit 107. Note that arrival angle estimation section 105 has the same function as arrival angle estimation section 105 in conventional base station apparatus 500 shown in FIG.

  Based on the arrival angle estimation result for each mobile terminal 200 input from the arrival angle estimation unit 105, the non-orthogonal weight calculation unit 107, for example, the maximum power in the direction for each mobile terminal 200, that is, each mobile terminal 200 calculates a weight (hereinafter referred to as “non-orthogonal weight”) that forms a beam from which the received power of the received signal received by 200 is maximized, and performs transmission processing on the calculated non-orthogonal weight for each mobile terminal 200 Output to the unit 103. In addition, the non-orthogonal weight calculation unit 107 is configured to generate an independent non-orthogonal signal for each mobile terminal 200 based on the change in the arrival angle estimation result for each mobile terminal 200 input from the arrival angle estimation unit 105. The result of calculating the amount of interference generated between the beams and the priority of communication with the mobile terminal 200 existing within the communication range (hereinafter, this priority determination is referred to as “scheduling”), and the scheduling result Is output to the interference amount calculation unit 108. The non-orthogonal weight calculation unit 107 has the same function as the orthogonal weight calculation unit 106 in the conventional base station apparatus 500 shown in FIG. 6, but in the present embodiment, all mobile terminals 200 that perform communication. It is not necessary for the downstream beams to be orthogonal.

  Based on the scheduling result within the communication range input from the non-orthogonal weight calculation unit 107, the interference amount calculation unit 108 calculates the interference amount of the modulated transmission signal generated by the data modulation unit 1031 for each mobile terminal 200. Then, the calculated interference amount for each mobile terminal 200 is output to the transmission processing unit 103.

  The transmission processing unit 103 performs processing such as data modulation processing, inverse Fourier transform, and analog / digital conversion on transmission data input from a control device (not shown) to generate a transmission signal, and uploads the generated transmission signal. Output to the converter 104. The transmission processing unit 103 has the same number of antennas as that of the base station apparatus 100, and performs transmission data conversion processing for each antenna. The transmission processing unit 103 has the same function as the transmission processing unit 103 in the conventional base station apparatus 500 illustrated in FIG. 6, but in this embodiment, for example, is generated for transmission to the mobile terminal 201. A function of removing interference is added so that the transmitted signal does not interfere with other mobile terminals 202 to 20K.

  The data modulation section 1031 performs processing for compensating transmission data such as an error code on transmission data input from a control device (not shown), and further performs modulation by a predetermined modulation method to modulate the transmission data. Is output to the interference removal unit 1033 and the interference amount calculation unit 108. Data modulation section 1031 has the same function as data modulation section 1031 in conventional base station apparatus 500 shown in FIG.

  The interference removal unit 1033 removes the interference amount according to the interference amount for each mobile terminal 200 input from the interference amount calculation unit 108 from the modulated transmission data input from the data modulation unit 1031 and removes the interference amount. The transmission data is output to downlink beam forming section 1032.

  Downlink beam forming section 1032 performs a process of multiplying the transmission data from which the interference amount input from interference cancellation section 1033 is removed by the non-orthogonal weight for each mobile terminal 200 input from non-orthogonal weight calculation section 107, and For example, processing for communication compensation is performed by performing processing such as inverse Fourier transform and analog / digital conversion. Thereafter, a low-frequency transmission beam signal having directivity is formed for each mobile terminal 200, and the formed low-frequency transmission beam is output to the up-converter 104. Downlink beam forming section 1032 has the same function as downlink beam forming section 1032 in conventional base station apparatus 500 shown in FIG.

  The up-converter 104 converts the low-frequency transmission signal for each antenna input from the transmission processing unit 103 into a high-frequency signal, and transmits the signal to each mobile terminal 200 via the antenna. Upconverter 104 has the same function as that of upconverter 104 in conventional base station apparatus 500 shown in FIG.

<First Embodiment>
Hereinafter, a processing procedure when transmitting to the mobile terminal in the base station apparatus of the present embodiment will be described. FIG. 3 is a flowchart showing a processing procedure in the base station apparatus 100 of the present embodiment.
Note that the mobile terminal 200 can communicate with the base station apparatus 100 using a plurality of antennas. However, in the description of the present embodiment, the mobile terminal 200 has one antenna (N = 1). Give an explanation.

  First, when the base station apparatus 100 receives a reception signal from the mobile terminal 200 via an antenna, the arrival angle estimation unit 105 estimates the arrival angle from the reception signal converted by the down converter 101 to a low frequency. Subsequently, in step S100, the non-orthogonal weight calculation unit 107 calculates a non-orthogonal weight that maximizes the received power based on the following equation (1). Here, if the transmission signal transmitted from each antenna is received at the mobile terminal 200 in the same phase, it can be said that the reception power is maximum.

In the above equation (1), d represents the antenna element spacing of the base station apparatus 100, and λ ^(d) represents the wavelength of the incident wave.
The above equation (1) represents the phase difference with respect to the arrival angle θ _k of the signal transmitted from each antenna when the antenna 100-1 is used as a reference. By multiplying the non-orthogonal weights in 1), the phases of the received signals received at the arrival angle θ _k are matched, and the maximum power can be obtained.
The non-orthogonal weight is a vector whose length is proportional to the number of antennas. Further, the arrival angle θ _k is a numerical value from 0 ° to 180 ° in the case of a linear array in which the antennas of the base stations are arranged linearly as shown in FIG.

Thereafter, when the non-orthogonal weight calculation unit 107 calculates the non-orthogonal weights of all the mobile terminals 200 based on the above equation (1), the weight matrix W of the following equation (2) is obtained.
Note that the arrival angle θ _k and the matrix w (θ _k ), which is the vector of the above equation (1), have a one-to-one relationship, and the arrival angle θ _k estimated by the arrival angle estimation unit 105 is expressed by the equation (1). A weight matrix W can be obtained by substituting a value of 0 (0 °) to π (180 °) into the θ _k portion.

In the above equation (2), K represents the number of mobile terminals 200.
Note that the arrangement order of the non-orthogonal weights of each mobile terminal 200, which is a component of the weight matrix W of the above equation (2), indicates the priority order of communication with the mobile terminal 200 existing within the communication range. For example, in the weight matrix W, the non-orthogonal weights are arranged so that the non-orthogonal weight at the left end has the highest priority, and the priority becomes lower as going to the right.

  Subsequently, in step S200, the interference amount calculation unit 108 performs QR decomposition on the weight matrix W of the above equation (2) based on the following equation (3) to obtain a lower triangular matrix L. . For example, three mobile terminals 200 (K = 3), for example, mobile terminals 201 to 203, and the number of antennas of the base station apparatus 100 is four (M = 4), for example, with antennas 100-1 to 100-4. In some cases, the weight matrix W is a 3 × 4 matrix as shown in the following equation (4). Further, the following formula (5) is obtained by QR decomposition of the following formula (4).

In the above equations (3) and (5), L is a lower triangular matrix, and the lower triangular matrix L is l _ij = 0 (i> j). All the diagonal components are scalar quantities, and the components are complex numbers. Q is a unitary matrix, and the components of the unitary matrix Q are complex numbers. If the row vectors of the unitary matrix Q are q ₁ , q ₂ , and q ₃ , respectively, the power of each row vector is “1”, and the row vectors are orthogonal to each other.

  Subsequently, when the base station apparatus 100 transmits the transmission data, the interference cancellation unit 1033, in step S300, obtains the lower triangle obtained from the modulated transmission data input from the data modulation unit 1031 by the above equation (3). Based on the matrix L, interference components are sequentially subtracted and transmitted. For example, when transmitting transmission data to the mobile terminal 201, the interference component of the transmission signal of the transmission data is subtracted from the transmission signals for all the mobile terminals 200 other than the mobile terminal 201 existing within the communication range.

  For example, when the above-described mobile terminal 200 is three (K = 3) and the number of antennas of the base station apparatus 100 is four, if the transmission symbols of the mobile terminals 201 to 203 are expressed by the following equation (6), In beam forming, a transmission signal is generated by multiplying a transmission symbol by a ZF weight and using the following equation (7).

  In the present embodiment, using the following equation (8), the above equation (5) is modified to obtain the following equation (9).

  At this time, the above equation (9) is substituted into the above equation (7) to obtain the following equation (10).

In the above equation (10), the transmission signal of the mobile terminal 201 includes only S _1, but the transmission signal of the mobile terminal 202 includes the transmission signal component (l ₁₂ / l ₂₂ S ₁ of the mobile terminal 201. The transmission signal of the mobile terminal 203 includes the transmission signal component of the mobile terminal 201 (l ₁₃ / l ₃₃ S ₁ ) and the transmission signal component of the mobile terminal 202 (l ₂₃ / l ₃₃ S ₂ ). It is included. Thus, interference removal can be performed by subtracting the interference component in advance using the known interference component.
As described above, the transmission signals S ′ ₁ , S ′ ₂ , S ′ of the mobile terminals 201 to 203 after the interference components are sequentially removed from the mobile terminal 201 in the order of the following equations (11) to (14). ₃ can be obtained.

  Next, the transmission direction and transmission power of the transmission signal in this embodiment will be described. FIG. 4 is a graph showing the relationship between the transmission direction and transmission power of the transmission signal transmitted by the conventional base station device 500 and the base station device 100 of the present embodiment. In FIG. 4, the X axis indicates the direction in which the transmission signal is transmitted, and the Y axis indicates the transmission power of the transmission signal transmitted by the base station device 500 and the base station device 100.

  FIG. 4 shows the influence of the transmission signal transmitted from the base station device 500 and the base station device 100 to the mobile terminal 201 on the transmission power of the transmission signal for the other mobile terminals 202 and 20K in the communication range. Also, with respect to the location where the base station apparatus 500 and the base station apparatus 100 exist, the mobile terminal 201 exists in a 45 ° direction, the mobile terminal 202 exists in a 0 ° direction, and the mobile terminal 20K exists in a −15 ° direction. Yes.

  In FIG. 4, when the conventional base station apparatus 500 transmits the transmission signal having the transmission power waveform shown in P201 of FIG. 4 to the mobile terminal 201, the transmission power waveform of the transmission signal to the mobile terminal 202 is as shown in P202a of FIG. The transmission power waveform of the transmission signal to the mobile terminal 20K is a waveform like P20Ka in FIG. In the transmission of the conventional base station apparatus 500 shown in FIG. 4, interference with the mobile terminal 20K occurs in the direction of 20 °.

  On the other hand, in FIG. 4, when the base station apparatus 100 of the present embodiment transmits a transmission signal having a transmission power waveform indicated by P201 in FIG. 4 to the mobile terminal 201 in the same manner as the base station apparatus 500, the transmission signal to the mobile terminal 202 The transmission power waveform is a waveform like P202b in FIG. 4, and the transmission power waveform of the transmission signal to the mobile terminal 20K is a waveform like P20Kb in FIG. In the transmission of the base station apparatus 100 of the present embodiment, the interference that has occurred in the 20 ° direction with respect to the mobile terminal 20K is removed.

As described above, according to the first embodiment of the present invention, there is no loss of transmission power of a transmission signal in downlink communication by removing multi-user interference, and the directional beam transmitted by the base station apparatus. Good communication can be performed without causing any interference.
In addition, since it is not necessary for the downlink beams to all the mobile terminals 200 that perform communication to be orthogonal, unnecessary radiation in an unintended direction and an increase in the dynamic range of non-orthogonal weights can be suppressed to a low level.

  In the description of the first embodiment of the present invention, the case where the mobile terminal 200 has one antenna (N = 1) has been described, but the mobile terminal 200 has two antennas (N = 2). The above case can be processed in the same manner as described above.

<Second Embodiment>
Hereinafter, a processing procedure in the case of performing transmission by scheduling the priority of communication with the mobile terminal based on the change in the angle of arrival estimated in the base station apparatus of the present embodiment will be described. FIG. 5 is a flowchart showing a processing procedure for performing scheduling in the base station apparatus 100 of the present embodiment.

First, when the base station apparatus 100 receives a reception signal from the mobile terminal 200 via an antenna, the arrival angle estimation unit 105 estimates the arrival angle from the reception signal converted by the down converter 101 to a low frequency. Subsequently, in step S101, the non-orthogonal weight calculation unit 107 calculates the non-orthogonal weight that maximizes the received power based on the above equation (1), similarly to step S100 in FIG.
Further, when the non-orthogonal weight calculation unit 107 completes the calculation of the non-orthogonal weights of all the mobile terminals 200 based on the above equation (1), the weight matrix W of the above equation (2) is obtained.

Subsequently, in step S151, the non-orthogonal weight calculation unit 107 schedules the communication priority with the mobile terminal 200 based on the change in the arrival angle estimated by the arrival angle estimation unit 105, and determines the priority of the scheduled priority. The non-orthogonal weight matrix W is rearranged in order.
Note that, when scheduling communication priorities with the mobile terminal 200, the priorities are scheduled in consideration of the influence of interference removal processing by the interference removal unit 1033 on communication with other mobile terminals 200.

Specific scheduling will be described below.
First, since the base station apparatus 100 always receives the transmission signal from the mobile terminal 200 and estimates the arrival angle, the base station apparatus 100 can recognize the movement of the mobile terminal 200 based on the estimated change in the arrival angle. That is, when there is a difference between the arrival angle estimated from the previous received signal and the arrival angle estimated from the current received signal, the mobile terminal 200 is moving and the mobile terminal 200 having a large difference in the arrival angles is large. Can be recognized as moving at a high speed. In addition, it can be said that the mobile terminal 200 having a low moving speed, that is, having a small difference in arrival angle, has a low probability of being out of the communication range of the base station apparatus 100, and therefore has a high frequency of communication with the base station apparatus 100. .
As a result, the communication with the mobile terminal 200 having a high communication frequency is less likely to be performed by the interference removal unit 1033 than the communication with the mobile terminal 200 having a low communication frequency. It can be judged that the influence on Therefore, the priority of communication with the mobile terminal 200 with a small change in the arrival angle is increased, and the priority is decreased as the change in the arrival angle increases.

For example, when the above-described mobile terminal 200 is three (K = 3) and the number of antennas of the base station apparatus 100 is four, the weight matrix W is determined in advance as shown in the above equation (4). Assuming that the mobile terminals 201, 202, and 203 are arranged in the order of the mobile terminal 200 numbers, the arrival angle estimation unit 105 periodically estimates the arrival angle θ _k for each mobile terminal 200, and the arrival angle θ _k. Observe the amount of change. At this time, for example, if the arrival angle of the mobile terminal 201 at time t is θ ₁ (t), the amount of change is Δ ₁ = | θ ₁ (t) −θ ₁ (t−1) |. Similarly, the arrival angle changes Δ ₂ and Δ ₃ of the mobile terminals 202 and 203 are observed, and the weight matrix W is rearranged in ascending order of the observed arrival angle changes Δ.
For example, when the amount of change Δ of the mobile terminals 201 to 203 is the amount of change Δ ₁ = 0.3, the amount of change Δ ₂ = 0.3, and the amount of change Δ ₃ = 0.3, the change amount Δ is in ascending order. The weight matrix W is rearranged, and the weight matrix W is expressed by the following equation (15).

  Subsequently, in step S201, the interference amount calculation unit 108 triangulates the weight matrix W rearranged in the same manner as in step S200 of FIG. A matrix L is obtained.

  Subsequently, when the base station apparatus 100 transmits the transmission data, the interference amount calculation unit 108 uses the above equation in step S300 from the modulated transmission data input from the data modulation unit 1031 as in step S300 of FIG. Based on the lower triangular matrix L obtained in (3), the interference components are successively subtracted and transmitted.

  As described above, according to the second embodiment of the present invention, the uncertain movement of the mobile terminal 200 is less affected by the uncertain change in the arrival angle due to the movement of the mobile terminal 200. Precoding processing with high robustness can be performed.

  In addition, you may make it implement | achieve the function of a part of base station apparatus 100 in embodiment mentioned above, for example, the non-orthogonal weight calculation part 107, and the interference amount calculation part 108 with a computer. In that case, the program for realizing the control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” dynamically holds a program for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system that serves as a server or a client in that case may also be included that holds a program for a certain time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes various modifications within the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 100,500 ... Base station apparatus, 100-1, 100-2, 100-M ... Antenna, 101 ... Down converter, 102-1, 102-2, 102-M ... Reception processing part , 1021 ... Uplink beam forming section, 1022 ... Data demodulation section, 103-1, 103-2, 103-M ... Transmission processing section, 1031 ... Data modulation section, 1032 ... Downlink beam Forming unit, 1033 ... Interference canceling unit, 104 ... Upconverter, 105 ... Arrival angle estimation unit, 106 ... Orthogonal weight calculation unit, 107 ... Non-orthogonal weight calculation unit, 108 ... interference quantity calculation unit, 201,202,20K ··· mobile terminal, 201-1,201-2, ···, 201-N ··· _{antenna, h 1, h 2, h} K ··· frequency band

Claims (4)

In a transmission device of a wireless communication system that includes a plurality of antennas and performs communication with one or more communication devices using a plurality of frequency bands,
The transmitter is
Using the received signal received by the transmitting device, the arrival direction estimating means for estimating the arrival angle indicating the arrival direction of the transmission signal that exists within the communication range and is transmitted from the counterpart communication device to be a communication partner;
Based on the arrival angle of the transmission signal from the counterpart communication apparatus estimated by the arrival direction estimation means, the amount of interference between the transmission beam transmitted to one counterpart communication apparatus and the transmission beam transmitted to another counterpart communication apparatus is calculated. An interference amount estimating means for calculating a variable for estimation;
Based on the variable for estimating the interference amount calculated by the interference amount estimation means, interference removal means for removing the interference amount from the transmission signal transmitted to the counterpart communication device;
Based on the arrival angle of the transmission signal from the counterpart communication device estimated by the arrival direction estimation means, beam forming for forming a transmission beam having directivity from the transmission signal from which the interference amount is removed by the interference amount removal means Means, and
The priority of the process of removing the interference amount from the transmission signal transmitted to the counterpart communication device is based on the amount of change in the arrival angle of the transmission signal from the counterpart communication device estimated by the arrival direction estimation means. Transmitter device.   The priority of the process of removing the amount of interference from the transmission signal transmitted to the counterpart communication device is higher as the priority of the counterpart communication device with a small amount of change in the arrival angle is high and the change amount of the arrival angle is large. The transmission apparatus according to claim 1, wherein the priority order of the counterpart communication apparatus is lowered. The variable for estimating the amount of interference is a phase difference with respect to the estimated arrival angle θ _k of a signal transmitted from each antenna when one antenna of the plurality of antennas of the transmission device is used as a reference. Is a weight w (θ _k ) representing
The arrival angle θ _k is the arrival angle of the transmission signal from the kth counterpart communication device estimated by the arrival direction estimation means,
k is a positive integer from 1 to K;
K is the number of the partner communication device,
The weight w (θ _k ) is a weight multiplied by the signal to the k-th partner communication device transmitted from each antenna of the transmission device,
The amount of interference removed from the transmission signal transmitted to the kth counterpart communication device is obtained by QR decomposition of the weight matrix in which the weights w (θ _k ) are arranged in the priority order of each counterpart communication device. An interference component for the kth counterpart communication device calculated using the lower triangular matrix,
The transmission apparatus according to claim 1, wherein the transmission apparatus is a transmission apparatus. In a transmission / reception method of a transmission device of a wireless communication system that includes a plurality of antennas and performs communication with one or more communication devices using a plurality of frequency bands,
The transmitter is
An arrival direction estimation procedure for estimating an arrival angle indicating an arrival direction of a transmission signal that exists within a communication range and is transmitted from a counterpart communication device that is a communication counterpart, using a reception signal received by the transmission device;
Based on the arrival angle of the transmission signal from the counterpart communication apparatus estimated by the arrival direction estimation procedure, the amount of interference between the transmission beam transmitted to one counterpart communication apparatus and the transmission beam transmitted to another counterpart communication apparatus is calculated. An interference amount estimation procedure for calculating a variable for estimation;
Based on the variable for estimating the interference amount calculated by the interference amount estimation procedure, an interference removal procedure for removing the interference amount from the transmission signal transmitted to the counterpart communication device;
Beam forming for forming a transmission beam having directivity from the transmission signal from which the interference amount has been removed by the interference amount removal procedure, based on the arrival angle of the transmission signal from the counterpart communication device estimated by the arrival direction estimation procedure Including steps,
The priority of the process of removing the interference amount from the transmission signal transmitted to the counterpart communication device is based on the amount of change in the arrival angle of the transmission signal from the counterpart communication device estimated by the arrival direction estimation procedure. Transmission / reception method.

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