JP2014017738A - Transmission station device and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce signal errors in simultaneously transmitting signals to a plurality of reception station devices at the same frequency.SOLUTION: A base station 100 uses transmission channel information given by terminal stations 101-1 and 101-2 to calculate broadcast weight to be used for transmitting same data to the terminal stations 101-1 and 101-2 and unicast weight to be used for transmitting different data to the terminal stations 101-1 and 101-2. The base station 100 compares signals to be simultaneously transmitted to the respective terminal stations 101-1 and 101-2 for each OFDM symbol, generates transmission signals by using the broadcast weight if the signals are same, and generates transmission signals by using the unicast weight if the signals are different. Then, the base station 100 simultaneously outputs the transmission signals generated at the same frequency by radio from a plurality of antennas.

Description

  The present invention relates to a transmission station apparatus and a wireless communication method.

  There is an IEEE 802.11a standard as a high-speed wireless access system using the 5 GHz band. The high-speed wireless access system of this standard uses an orthogonal frequency division multiplexing (OFDM) modulation scheme, which is a technique for stabilizing characteristics in a multipath fading environment, and has a maximum of 54 Mbps (megabits per second). Throughput is realized (for example, see Non-Patent Document 1).

  Furthermore, IEEE802.11n realizes high-speed communication by using MIMO (Multiple input multiple output) technology capable of realizing spatial multiplexing using the same time and the same frequency channel using a plurality of antennas. Aiming at a transmission speed of up to 600 Mbps can be achieved (for example, see Non-Patent Document 1).

  Furthermore, IEEE 802.11ac, whose standard is being developed, has a speed exceeding 1 Gbps (gigabit per second) compared to IEEE 802.11n by multi-user MIMO technology that communicates with a plurality of radio stations at the same frequency channel and at the same time. It aims to realize wireless communication.

Masahiro Morikura, Shuji Kubota, “Revised Third Edition 802.11 High-Speed Wireless LAN Textbook”, Impress R & D, March 27, 2008

  However, when a base station that is a transmitting station apparatus transmits different data to a plurality of terminal stations that are receiving stations using multi-user MIMO technology, a single data is transmitted to a single terminal station. Large received power is required compared to the case of transmission. This is because interference between users increases because transmission is performed at the same frequency and at the same time, and furthermore, power allocated to data transmitted to each terminal station is reduced. Therefore, when the received power at the terminal station is lower than the received power that can be transmitted by the multi-user MIMO technique, data cannot be received accurately and a signal error occurs.

  The present invention has been made to solve the above problems, and provides a transmitting station apparatus and a wireless communication method capable of reducing signal errors when signals are simultaneously transmitted to a plurality of receiving station apparatuses at the same frequency. .

  In order to solve the above-described problem, the present invention provides a transmitting station apparatus that performs wireless communication simultaneously with a plurality of receiving station apparatuses, and includes a plurality of antennas that transmit and receive radio signals, and the receiving station that is received by the plurality of antennas. A radio unit that performs a reception process on a radio signal from a device, a transmission process that generates a radio signal from a plurality of transmission signals addressed to the receiving station device and transmits the signals simultaneously from the plurality of antennas, and a reception process in the radio unit The propagation channel acquisition unit that acquires the propagation channel information of the receiving station device from the radio signal that has been performed, and the propagation channel information of the plurality of reception station devices acquired in the propagation channel acquisition unit, the same data Broadcast weight, which is the transmission weight used when transmitting, and user, which is the transmission weight used when transmitting different data. A transmission weight calculating unit that calculates a cast weight according to a combination in which transmission signals addressed to the plurality of receiving station apparatuses are the same, and a transmission signal that is simultaneously transmitted to the plurality of receiving station apparatuses are compared for each symbol, Depending on the combination of the receiving station devices having the same data, the weight calculation is performed using the broadcast weight for symbols having the same data, and the unicast weight is used for symbols having different data. And a transmission signal generation unit that generates the transmission signal and outputs the transmission signal to the radio unit.

  Further, the present invention is the above-described transmission station apparatus, wherein the transmission signal generation unit performs the two-phase shift keying modulation or the four-phase shift keying modulation to generate the transmission signal, and the transmission weight calculation unit includes the transmission weight calculation unit Using the propagation channel information of the plurality of receiving station devices acquired by the propagation channel acquiring unit, the broadcast weight and the broadcast weight are used according to the combination in which the transmission signals addressed to the plurality of receiving station devices are the same. And calculating a unicast weight that gives the same phase rotation amount as the phase rotation amount in the receiving station apparatus when the transmission is performed.

  Further, the present invention is the above-described transmission station apparatus, wherein the transmission weight calculation unit uses the propagation channel information of the plurality of reception station apparatuses acquired by the propagation channel acquisition unit, and is addressed to the plurality of reception station apparatuses. The broadcast weight and the unicast weight that gives the same phase rotation amount as the phase rotation amount in the receiving station device when transmission using the broadcast weight is performed according to the combination in which the transmission signals of the same are transmitted. The transmission signal generation unit calculates and generates the transmission signal by quadrature amplitude modulation representing a predetermined number or more states. When the transmission power is a symbol larger than a predetermined value, the transmission signal generation unit simultaneously transmits to the plurality of receiving station apparatuses. Depending on the combination of the destination receiving station apparatuses with the same symbol of the transmission signal to be transmitted, the symbol having the same data The weight calculation is performed using the cast weight, and the weight calculation is performed using the unicast weight for symbols having different data. If the transmission power is lower than a predetermined symbol, the weight calculation is performed using the unicast weight. To generate the transmission signal and output it to the radio unit.

  Also, the present invention is the above-described transmission station apparatus, wherein the transmission signal generation unit sets information indicating which of the broadcast weight and the unicast weight is used for each symbol in the transmission signal. It is characterized by.

  Further, the present invention is the above-described transmitting station apparatus, wherein the radio unit transmits a propagation channel information estimation signal from the plurality of antennas to the receiving station apparatus, and the plurality of antennas transmit the propagation channel information. A radio signal in which propagation channel information measured by the receiving station apparatus is set based on an estimation signal is received and output to the radio unit.

  Further, the present invention is the above-described transmitting station apparatus, which is a wireless communication method executed by a transmitting station apparatus that performs wireless communication simultaneously with a plurality of receiving station apparatuses, and is a wireless communication method received from a plurality of antennas from the receiving station apparatus. A reception step of performing reception processing on a signal, a propagation channel acquisition step of acquiring propagation channel information of the receiving station device from the radio signal received and processed in the reception step, and acquired in the propagation channel acquisition step A plurality of broadcast weights, which are transmission weights used when transmitting the same data, and unicast weights, which are transmission weights used when transmitting different data, using the propagation channel information of the plurality of receiving station apparatuses Transmission weights calculated in accordance with combinations in which the transmission signals addressed to the receiving station devices are the same. And a transmission signal transmitted simultaneously to the plurality of receiving station devices for each symbol, and depending on the combination of the receiving station devices of the destination having the same data, the symbols having the same data A transmission signal generation step for performing a weight calculation using a broadcast weight and performing a weight calculation for the symbols having different data using the unicast weight to generate the transmission signal, and a plurality of signals generated in the transmission signal generation step A transmission step of performing a transmission process of simultaneously transmitting transmission signals addressed to the receiving station device from the plurality of antennas.

  According to the present invention, when a transmitting station apparatus transmits signals to a plurality of receiving station apparatuses at the same frequency at the same time, transmission is performed when the OFDM symbols of the signals transmitted simultaneously to the plurality of receiving station apparatuses are different from the same case. By switching the weight, it is possible to reduce signal errors.

It is a figure which shows the example of the radio | wireless communications system to which the radio | wireless communication method in 1st Embodiment is applied. It is a schematic block diagram which shows the internal structure of the base station in the embodiment. It is a figure which shows the example of the comparison of the transmission signal (BPSK) in the embodiment. It is a schematic block diagram which shows the internal structure of the terminal station in the same embodiment. It is a time chart which shows the operation | movement of the packet signal transmission in the same embodiment. It is a conceptual diagram which shows an example of embodiment of the transmission weight switching method in the embodiment. It is a schematic block diagram which shows the internal structure of the base station in 2nd Embodiment. It is a figure which shows the example of the transmission signal (BPSK) in the embodiment. It is a time chart which shows the operation | movement of the packet signal transmission in the same embodiment. It is a schematic block diagram which shows the internal structure of the base station in 4th Embodiment. It is a schematic block diagram which shows the internal structure of the terminal station in the same embodiment. It is a schematic block diagram which shows the internal structure of the base station in 5th Embodiment. It is a figure which shows the example of the transmission signal (16QAM) using the broadcast weight in the embodiment. It is a figure which shows the example of the received signal (16QAM) by the terminal station side in the same embodiment. It is a figure which shows the example of the transmission signal (64QAM) using the broadcast weight in the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[1. First Embodiment]
FIG. 1 is a diagram illustrating an example of a wireless communication system to which a wireless communication method according to the first embodiment of the present invention is applied. The wireless communication system shown in FIG. 1 includes a base station 100 as a transmitting station device and two terminal stations 101 as receiving station devices. Here, the two terminal stations 101 that perform wireless packet communication with the base station 100 are referred to as a terminal station 101-1 and a terminal station 101-2, respectively. For this communication, for example, multi-user MIMO technology is used. The terminal stations 101-1 and 101-2 located in the communication cell of the base station 100 belong to the base station 100, and communicate with an external network (not shown) via the base station 100.

The base station 100 is, for example, an access point in a wireless local area network (LAN), and the terminal station 101 is a computer, a portable information electronic device, or the like. The external network is a network other than the local network formed by the base station 100, for example, the Internet.
Further, as shown in the figure, the propagation channel between the base station 100 and the terminal station 101-1 and _{H 1,} to the propagation channel between the base station 100 and the terminal station 101-2 and _{H 2.}

  In the first embodiment, the base station 100 transmits symbols to the two terminal stations 101 at the same time when the OFDM (Orthogonal Frequency Division Multiplexing) symbols are the same and different symbols. The transmission weight is switched every time. This makes it possible to reduce signal errors.

[1.1 Base station configuration]
FIG. 2 is a schematic block diagram illustrating an internal configuration of the base station 100 according to the first embodiment.
As shown in the figure, the base station 100 includes a plurality of antennas 111, a radio unit 112, a propagation channel acquisition unit 113, a transmission weight calculation unit 114, a transmission signal generation unit 115, an information storage unit 116, And a network interface unit 117.

  The plurality of antennas 111 is connected to the wireless unit 112 and includes a plurality of antennas generally used in a wireless LAN or the like. In the case of transmission, the plurality of antennas 111 radiate by converting electric signals input from the radio unit 112 into radio waves. In the case of reception, the plurality of antennas 111 convert airwaves into electrical signals and output them to the radio unit 112.

  The radio unit 112 performs guard interval removal, demultiplexing processing by FFT (Fast Fourier Transform), channel equalization processing, subcarrier detection, deinterleaving on received signals received via a plurality of antennas 111 , Receive processing such as Viterbi decoding, and detect a wireless packet. The radio unit 112 outputs the detected radio packet to the network interface unit 117, and outputs a radio packet including the propagation channel information notified from the terminal station 101 to the propagation channel acquisition unit 113. The radio unit 112 also performs transmission processing such as guard interval addition and symbol shaping on the transmission signal input from the transmission signal generation unit 115, generates a radio packet, and transmits the radio packet via a plurality of antennas 111. .

The propagation channel acquisition unit 113 acquires the propagation channel H ₁ or H ₂ from the propagation channel information set in the radio packet input from the radio unit 112, and outputs it to the transmission weight calculation unit 114.

The transmission weight calculation unit 114 uses the propagation channels H ₁ and H ₂ input from the propagation channel acquisition unit 113 to calculate broadcast weights and unicast weight transmission weights using a calculation formula described later, and the information storage unit 116. Output to. The broadcast weight is a transmission weight used when OFDM symbols of signals transmitted simultaneously to a plurality of terminal stations 101 are the same. Unicast weight is a transmission weight used when OFDM symbols of signals transmitted simultaneously to a plurality of terminal stations 101 are different. In this example, the number of antennas 111 of the plurality of antennas 111 is 2. However, even when the number of antennas is 3 or more, the calculation can be performed in the same manner.

  The transmission signal generation unit 115 performs convolutional coding, interleave processing, subcarrier modulation, transmission weight calculation, IFFT (Inverse Fast Fourier Transform) processing, etc., on the signal input from the network interface unit 117. A transmission signal generation process is performed. However, in the transmission weight calculation, the transmission signal generation unit 115 compares the transmission signals addressed to the respective terminal stations 101 in units of OFDM symbols, and when the OFDM symbols are the same, using the broadcast weight input from the information storage unit 116. Performs transmission weight calculation. On the other hand, when the OFDM symbols are different, the transmission signal generation unit 115 performs transmission weight calculation using the unicast weight input from the information storage unit 116. The transmission signal generation unit 115 outputs a transmission signal generated as a result of the transmission signal generation processing to the radio unit 112.

  The information storage unit 116 stores the transmission weight (broadcast weight and unicast weight) input from the transmission weight calculation unit 114. Further, the information storage unit 116 outputs the stored transmission weight to the transmission signal generation unit 115.

  The network interface unit 117 converts the wireless packet input from the wireless unit 112 into a packet used in an external network and transmits the packet to the external network. The network interface unit 117 outputs a packet addressed to the terminal station 101 among the packets received from the external network to the transmission signal generation unit 115.

  Next, calculation formulas used by the transmission weight calculation unit 114 for calculating broadcast weights and unicast weights will be described.

<Broadcast weight calculation formula>
First, the broadcast weight calculation formula will be described. A propagation channel obtained by combining a propagation channel H ₁ between the base station 100 and the terminal station 101-1 and a propagation channel H ₂ between the base station 100 and the terminal station 101-2 as shown in Expression (1). Let _Hb1 . H _b1 is decomposed as shown in Expression (2) by singular value decomposition. Here, diag () represents a diagonal matrix having a matrix and coefficients in parentheses as diagonal elements.

However, U is a right singular value matrix, Σ is a diagonal matrix having the square root of the eigenvalue λ as a diagonal, and V is a right singular value matrix. V ^H represents a complex conjugate transpose of V. Here, the broadcast weight W _b1 is expressed by Equation (6).

The transmission weight calculation unit 114 calculates the broadcast weight W _b1 using the propagation channels H ₁ and H ₂ input from the propagation channel acquisition unit 113 according to the above formulas (1) to (6).

When using broadcast weight, the antenna freedom for null directivity can be reduced, so that the power efficiency per stream increases and the signal error decreases.
Furthermore, when the number of terminal stations for multi-user MIMO increases, the probability that transmission data will be the same increases, and a great effect can be obtained.

<Unicast weight calculation formula>
Next, a formula for calculating the unicast weight will be described. The unicast weight is a weight calculated from a zero forcing weight generally used in multi-user MIMO, and is calculated as shown in Expression (7).

The transmission weight calculation unit 114 calculates the unicast weight W _u1 using the propagation channels H ₁ and H ₂ input from the propagation channel acquisition unit 113 according to the above equation (7).
Here, the unicast weight is calculated from the zero forcing weight that is general in the multi-user MIMO technique, but may be calculated by other methods such as a block diagonalization method.

  FIG. 3 shows an example of transmission signal comparison by the transmission signal generator 115. The figure shows an example in which the transmission signal is BPSK (Binary Phase Shift Keying). As shown in the figure, the transmission signal generator 115 compares the data of the transmission signal G11 addressed to the terminal station 101-1 and the data of the transmission signal G12 addressed to the terminal station 101-2 for each OFDM symbol. As a result of the comparison, the transmission signal generation unit 115 changes the transmission weight to be used depending on whether or not they match.

For example, the transmission signal generator 115 uses the broadcast weight for both the transmission signal G11 and the transmission signal G12 because the data of the transmission signal G11 and the transmission signal G12 are the same for the OFDM symbols of the symbol numbers 2 and n. Performs transmission weight calculation.
On the other hand, for the OFDM symbols of symbol numbers 1 and 3, the transmission signal G11 and the transmission signal G12 have different data, and therefore, transmission weight calculation is performed using unicast weights for the transmission signal G11 and the transmission signal G12.

Here, BPSK is shown as an example of the transmission signal, but QPSK (Quadrature Phase Shift Keying), 16 QAM (Quadrature Amplitude Modulation), 64 QAM, and 256 QAM may be used.
The above is the description of the configuration of the base station 100.

[1.2 Terminal station configuration]
Next, the configuration of the terminal station 101 will be described.
FIG. 4 is a schematic block diagram showing the internal configuration of the terminal station 101. As shown in the figure, the terminal station 101 includes an antenna 121, a radio unit 122, a propagation channel acquisition unit 123, a notification unit 124, an information storage unit 125, a received signal acquisition unit 126, and a channel equalization unit. 127.

  The antenna 121 is connected to the radio unit 122. In the case of transmission, the antenna 121 converts an electric signal input from the wireless unit 122 into a radio wave and radiates it.

Radio section 122 performs guard interval removal and demultiplexing processing by FFT on the received signal received via antenna 121, and outputs the result to channel equalization section 127. The radio unit 122 performs reception processing such as subcarrier detection, deinterleaving, and Viterbi decoding on the signal input from the channel equalization unit 127, detects a radio packet, and receives the detected radio packet as a received signal. The data is output to the acquisition unit 126. Further, the radio unit 122 outputs the propagation channel (H ₁ for the terminal station 101-1 and H ₂ for the terminal station 101-2) acquired in the radio packet detection to the propagation channel acquisition unit 123. The radio unit 122 performs convolutional coding, interleaving processing, subcarrier modulation, IFFT processing, guard interval addition, symbol shaping, and the like on the signal input from the notification unit 124 to generate a radio packet, and 121 to transmit.

  The channel equalization unit 127 performs channel equalization for each OFDM symbol on the signal input from the radio unit 122 by using information on match / mismatch for each OFDM symbol set in this signal, To the unit 122.

The reception signal acquisition unit 126 acquires a wireless packet input from the wireless unit 122. The propagation channel acquisition unit 123 acquires the propagation channel H ₁ or H ₂ from the radio packet input from the radio unit 122 and outputs it to the information storage unit 125. The information storage unit 125 stores the information acquired by the propagation channel acquisition unit 123 and input. Further, the information storage unit 125 outputs the stored propagation channel H ₁ or H ₂ to the notification unit 124. The notification unit 124 generates a transmission signal including information on the propagation channel H ₁ or H ₂ input from the information storage unit 125 and outputs the transmission signal to the radio unit 122.
The above is the description of the configuration of the terminal station 101.

[1.3 Example of communication procedure between base station 100 and terminal station 101]
Next, a communication procedure between the base station 100 and the terminal station 101 to which the wireless communication method in the first embodiment is applied will be described using a time chart.

  FIG. 5 is a time chart showing the operation of packet signal transmission in the first embodiment. In this description, it is assumed that CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) is adopted as the access control method.

  In the figure, in the base station 100, transmission data addressed to the terminal stations 101-1 and 101-2 has occurred. When the radio unit 122 of the base station 100 detects that the communication frequency band is in an idle state by the carrier sense CS executed at the time t0, the transmission signal generation unit 115 A paging signal including a destination address of 101-2 and a training signal for channel estimation is generated. The radio unit 122 transmits the call signal generated by the transmission signal generation unit 115 by the plurality of antennas 111 during a period from time t1 to time t2 when a certain time has elapsed from time t0.

Next, the terminal stations 101-1 and 101-2 designated as destinations in the call signal receive the call signal by the antenna 121 within the same time period t1 to time t2, and the radio unit 122 receives the received call signal. A propagation channel is acquired from the signal and output to the propagation channel acquisition unit 123. Thus, the propagation channel acquisition unit 123 of the terminal station 101-1 are stored to obtain a propagation channel _{H 1} to the information storage unit 125, the propagation channel acquisition unit 123 of the terminal station 101-2 obtains the propagation channel _{H 2} And stored in the information storage unit 125.

Next, in the period from time t3 to time t4 after the elapse of a certain time from the time t2, the notification unit 124 of the terminal station 101-1 includes propagation channel information set the propagation channel H ₁ read out from the information storage unit 125 A notification signal is generated and transmitted via the wireless unit 122 and the antenna 121. The destination of this notification signal is the base station 100.

Similarly, in the period of time t6 the time t5 after the elapse of a certain time from the time t4, the notification unit 124 of the terminal station 101-2 includes propagation channel information set the propagation channel H ₂ read from the information storage unit 125 A notification signal is generated and transmitted via the wireless unit 122 and the antenna 121. The destination of this notification signal is the base station 100.

  Here, an example is shown in which two terminal stations 101 continuously transmit notification signals. However, after the base station 100 transmits a signal requesting a notification signal, each terminal station 101 transmits a notification signal. May be sent.

Next, the plurality of antennas 111 of the base station 100 receive notification signals transmitted by the terminal stations 101-1 and 101-2, respectively. The propagation channel acquisition unit 113 acquires the propagation channel H ₁ and the propagation channel H ₂ from the propagation channel information set in each notification signal output from the radio unit 112. The transmission weight calculation unit 114 calculates the broadcast weight W _b1 from the acquired propagation channels H ₁ and H _{2 using} the equations (1) to (6), and calculates the unicast weight W _u1 using the equation (7). calculate. The propagation channel acquisition unit 113 stores the calculated broadcast weight W _b1 and unicast weight W _u1 in the information storage unit 116.

The transmission signal generation unit 115 of the base station 100 performs broadcast weighting based on whether or not the OFDM symbols of Data1 and Data2 that are transmission signals to the terminal station 101-1 and the terminal station 101-2 match. _Wb1 and unicast weight _Wu1 are switched to perform weight calculation of Data1 and Data2, and a transmission signal is generated. Note that the transmission signal also includes information on match / mismatch for each OFDM symbol, that is, information on whether broadcast weight or unicast weight is used. The coincidence / non-coincidence information may be location information indicating a coincidence or non-coincidence symbol, or may be codebook information that can specify the location information.

  The radio unit 112 of the base station 100 simultaneously transmits the transmission signals generated by the transmission signal generation unit 115 via the plurality of antennas 111 from time t7 to time t8 when a certain time has elapsed from time t6.

  Next, when the radio unit 122 of the terminal station 101-1 decodes the radio packet signal of the transmission signal from the base station 100 received by the antenna 121 without error, the notification unit 124 generates the confirmation signal Ack. The notification unit 124 transmits the generated confirmation signal Ack to the base station 100 via the wireless unit 122 and the antenna 121 from time t9 to time t10 when a certain time has elapsed from time t8 after reception of the wireless packet signal.

  Similarly, when the radio unit 122 of the terminal station 101-2 decodes the radio packet signal of the transmission signal from the base station 100 received by the antenna 121 without error, the notification unit 124 generates the confirmation signal Ack. The notification unit 124 transmits the confirmation signal Ack to the base station 100 via the wireless unit 122 and the antenna 121 from time t11 to time t12 when a certain time has elapsed from time t10 after reception of the wireless packet signal. To do.

Note that the channel equalization unit 127 of the terminal stations 101-1 and 101-2 receives information on matching / mismatching for each OFDM symbol included in the radio packet signal output from the radio unit 122 when decoding the transmission signal. Based on the above, channel equalization is performed in symbol units. This is because the phase rotation amount of the signal received at the terminal station 101 differs between when the broadcast weight is used and when the unicast weight is used.
The above is the first embodiment.

[2. Second Embodiment]
In the second embodiment, the base station is used to generate transmission signals addressed to these terminal stations according to the combination pattern of whether or not the OFDM symbols of the signals transmitted simultaneously to the three terminal stations match. Switch the transmission weight for each symbol. This makes it possible to reduce signal errors.

FIG. 6 is a diagram illustrating an example of a wireless communication system to which the wireless communication method according to the second embodiment of the present invention is applied. The wireless communication system shown in FIG. 1 includes a base station 100a as a transmitting station device and a plurality of terminal stations 101 as receiving station devices. Here, the three terminal stations 101 that perform wireless packet communication with the base station 100a are described as terminal stations 101-1, 101-2, and 101-3, respectively. The terminal stations 101-1, 101-2, and 101-3 belong to the base station 100a, and communicate with an external network (not shown) via the base station 100a.
Further, as shown in the figure, the propagation channel between the base station 100a and the terminal station 101-1 _{H 1,} the propagation channel of _{H 2} between the base station 100a and the terminal station 101-2, and base station 100a terminal the propagation channel between the stations 101-1 and _{H 3.}

[2.1 Base station configuration]
FIG. 7 is a schematic block diagram showing the internal configuration of the base station 100a in the second embodiment. In this figure, the same parts as those of the base station 100 in the first embodiment shown in FIG.
As shown in the figure, the base station 100a includes a plurality of antennas 111, a radio unit 112, a propagation channel acquisition unit 113, a transmission weight calculation unit 131, a transmission signal generation unit 132, an information storage unit 116, And a network interface unit 117. As described above, the base station 100a shown in the figure is different from the base station 100 shown in FIG. 2 in that instead of the transmission weight calculation unit 114 and the transmission signal generation unit 115, the transmission weight calculation unit 131 and the transmission signal generation unit. 132.

The transmission weight calculation unit 131 calculates a transmission weight for each combination of the propagation channels H ₁ , H ₂ , and H ₃ input from the propagation channel acquisition unit 113 using a calculation formula described later, and outputs the transmission weight to the information storage unit 116. . Here, the number of antennas 111 of the plurality of antennas 111 of the base station 100a is three.

  The transmission signal generation unit 132 performs transmission signal generation processing such as convolutional coding, interleaving processing, subcarrier modulation, transmission weight calculation, and IFFT processing on the signal input from the network interface unit 117. However, in the transmission weight calculation, the transmission signal generation unit 132 compares transmission signals addressed to the three terminal stations 101 in units of OFDM symbols, and uses the broadcast weight and the unicast weight according to the comparison result to transmit the weight. Perform the operation. The transmission signal generation unit 132 outputs a transmission signal generated as a result of the transmission signal generation process to the radio unit 112.

  Next, calculation formulas used by the transmission weight calculation unit 131 for calculating broadcast weights and unicast weights will be described.

<Calculation formula of broadcast weight for H ₁ , H ₂ , H ₃ >
Propagation channel H ₁ between base station 100a and terminal station 101-1, propagation channel H ₂ between base station 100a and terminal station 101-2, and propagation channel H between base station 100a and terminal station 101-3 Let H _{b2 be} a propagation channel in which ₃ is coupled as shown in equation (8). H _b2 is decomposed as shown in Equation (9) by singular value decomposition.

Here, the broadcast weight W _b2 for H ₁ , H ₂ , and H ₃ is expressed by Equation (13).

The transmission weight calculation unit 131 uses the propagation channels H ₁ , H ₂ , and H ₃ input from the propagation channel acquisition unit 113 according to the above formulas (7) to (12), and uses H ₁ , H ₂ , H _3. Broadcast weight _Wb2 is calculated.

<Broadcast Weight Calculation Formula for H ₁ and H ₂ and Unicast Weight Calculation Formula for H ₃ >
First, calculation formulas of broadcast weights for H ₁ and H ₂ are shown. First, singular value decomposition is performed on H ₃ as shown in equation (14).

Then, a part of formula (17), the propagation channel _{H 1} between the base station 100a and the terminal station 101-1, propagation channel _{H 2} and the equation between the base station 100a and the terminal station 101-2 ( The propagation channel coupled as shown in 18) is assumed to be _Hb3 . H _b3 is decomposed as shown in Expression (19) by singular value decomposition.

Here, the broadcast weight W _b3 for H ₁ and H ₂ is expressed by Equation (23).

The transmission weight calculation unit 131 uses the propagation channels H ₁ , H ₂ , and H ₃ input from the propagation channel acquisition unit 113 according to the above equations (14) to (23), and broadcast weights for H ₁ and H ₂ . W _b2 is calculated.

Next, a unicast weight calculation formula for H ₃ is shown. The unicast weight W _u2 is calculated by Expression (24) and Expression (25).

The transmission weight calculation unit 131 uses the propagation channels H ₁ , H ₂ , and H ₃ input from the propagation channel acquisition unit 113 according to the above equations (24) and (25), and uses the unicast weights W _u2 for H ₃ . Is calculated.

<Broadcast Weight Calculation Formula for H ₁ and H ₃ and Unicast Weight Calculation Formula for H ₂ >
Calculation formula broadcast wait for H _{1, H 3} is changed _H 1, _{H 2} in the equation for calculating the broadcast wait for _H 1, _{H 2} shown formula (14) to Formula (23) to _H 1, _{H 3} It is a formula.
Further, the calculation formula of unicast weight for H ₂ is the same as the calculation formula of broadcast weight for H ₃ shown in Expression (24) and Expression (25).

<Broadcast Weight Calculation Formula for H ₂ and H ₃ and Unicast Weight Calculation Formula for H ₁ >
Calculation formula broadcast wait for H _{2, H 3} is changed _H 1, _{H 2} in the equation for calculating the broadcast wait for _H 1, _{H 2} shown formula (14) to Formula (23) in _H 2, _{H 3} It is a formula.
In addition, the calculation formula of the unicast weight for H ₁ is the same as the calculation formula of the broadcast weight for H ₃ shown in Expression (24) and Expression (25).

<Unicast weight calculation formula for H ₁ , H ₂ , H ₃ >
The unicast weight W _u3 for H ₁ , H ₂ , and H ₃ is shown in Equation (26).

The transmission weight calculation unit 131 uses the propagation channels H ₁ , H ₂ , and H ₃ input from the propagation channel acquisition unit 113 according to the above equation (26), and uses the unicast weights W for H ₁ , H ₂ , and H _{3. u3} is calculated.
In this example, the unicast weight is calculated from the zero forcing weight that is general in the multi-user MIMO technique, but may be calculated by other methods.

  FIG. 8 shows an example of transmission signal comparison by the transmission signal generator 132. In the figure, an example in which the transmission signal is BPSK is shown. As shown in the figure, the transmission signal generation unit 132 transmits data of a transmission signal G21 addressed to the terminal station 101-1, data of a transmission signal G22 addressed to the terminal station 101-2, and transmission addressed to the terminal station 101-3. The data of the signal G23 is compared for each OFDM symbol. The transmission signal generation unit 132 changes the transmission weight used when the data of the respective transmission signals match completely, when they partially match, or when they do not all match.

That is, when the OFDM symbols of the transmission signals G1 to G3 addressed to the terminal station 101-1, addressed to the terminal station 101-2, and addressed to the terminal station 101-3 are the same as symbol number 1, the transmission signal generation unit 132 A transmission weight calculation is performed on each of the transmission signals G1 to G3 using the broadcast weight W _b2 for H ₁ , H ₂ , and H ₃ input from the information storage unit 116.

When the OFDM symbol of the transmission signal G21 addressed to the terminal station 101-1 and the transmission signal G22 addressed to the terminal station 101-2 are the same as in the symbol number 2, the transmission signal generation unit 132 is input from the information storage unit 116. that _H 1, performs a transmission weight calculation on a transmission signal G21 and G22 with the broadcast weight _{W b3} for _{H 2,} performs transmission weight calculation on a transmission signal G23 using unicast weight _{W u2} for _{H 3.}

When the OFDM symbol of the transmission signal G21 addressed to the terminal station 101-1 and the transmission signal G23 addressed to the terminal station 101-3 are the same as symbol number 3, the transmission signal generation unit 132 is input from the information storage unit 116. A transmission weight calculation is performed on the transmission signals G21 and G23 using broadcast weights for H ₁ and H ₃ and a transmission weight calculation is performed on the transmission signal G22 using a unicast weight for H ₂ .

When the OFDM symbol of the transmission signal G22 addressed to the terminal station 101-2 and the transmission signal G23 addressed to the terminal station 101-3 are the same as in the symbol number n, the transmission signal generation unit 132 is input from the information storage unit 116. A transmission weight calculation is performed on the transmission signals G22 and G23 using broadcast weights for H ₂ and H ₃ and a transmission weight calculation is performed on the transmission signal G21 using a unicast weight W _u3 for H ₁ .

Here, BPSK is shown as an example of the transmission signal, but QPSK, 16QAM, 64QAM, and 256QAM may be used.
When these modulation schemes are used, the OFDM symbols of transmission signals addressed to the terminal station 101-1, addressed to the terminal station 101-2, and addressed to the terminal station 101-3 may all be different. In that case, the transmission signal generation unit 132 performs transmission weight calculation on the transmission signals G1 to G3 using the unicast weights for H ₁ , H ₂ , and H ₃ input from the information storage unit 116.
The above is the description of the configuration of the terminal station 101a.

[2.2 Terminal station configuration]
The configuration of the terminal station 101 is the same as that of the terminal station 101 of the first embodiment.

[2.3 Example of Communication Procedure between Base Station 100a and Terminal Station 101]
Next, a communication procedure between the base station 100a and the terminal station 101 to which the wireless communication method according to the second embodiment is applied will be described using a time chart.

  FIG. 9 is a time chart illustrating an operation of transmitting a packet signal in the second embodiment. In this description, it is assumed that CSMA / CA is adopted as the access control method.

  In the figure, in the base station 100a, transmission data addressed to the terminal stations 101-1, 101-2, and 101-3 has occurred. When the radio unit 122 of the base station 100a detects that the communication frequency band is in an idle state by the carrier sense CS executed at time t0, the transmission signal generation unit 115 includes the terminal station 101-1, A paging signal including destination addresses 101-2 and 101-3 and a training signal for channel estimation is generated. The radio unit 122 transmits the call signal generated by the transmission signal generation unit 115 by the plurality of antennas 111 during a period from time t1 to time t2 when a certain time has elapsed from time t0.

Next, the terminal stations 101-1, 101-2, and 101-3 specified as destinations by the call signal receive the call signal by the antenna 121 during the same period from time t 1 to time t 2, and the wireless unit 122 Acquires a propagation channel from the received paging signal and outputs it to the propagation channel acquisition unit 123. Thus, the propagation channel acquisition unit 123 of the terminal station 101-1 are stored to obtain a propagation channel _{H 1} to the information storage unit 125, the propagation channel acquisition unit 123 of the terminal station 101-2 obtains the propagation channel _{H 2} Te is stored in the information storage unit 125, the propagation channel acquisition unit 123 of the terminal station 101-3 stores obtains propagation channel _{H 3} in the information storage unit 125.

Next, in the period from time t3 to time t4 after the elapse of a certain time from the time t2, the notification unit 124 of the terminal station 101-2 includes propagation channel information set the propagation channel H ₁ read out from the information storage unit 125 A notification signal is generated and transmitted via the wireless unit 122 and the antenna 121. The destination of this notification signal is the base station 100a.

Similarly, in the period of time t6 the time t5 after the elapse of a certain time from the time t4, the notification unit 124 of the terminal station 101-2 includes propagation channel information set the propagation channel H ₂ read from the information storage unit 125 A notification signal is generated and transmitted via the wireless unit 122 and the antenna 121. The destination of this notification signal is the base station 100a.

Similarly, in the period of time t8 from time t7 after the elapse of a certain time from the time t6, the notification unit 124 of the terminal station 101-3 includes a propagation channel information set the propagation channel H ₃ read from the information storage unit 125 A notification signal is generated and transmitted via the wireless unit 122 and the antenna 121. The destination of this notification signal is the base station 100a.

  In this example, three terminal stations 101 continuously transmit notification signals. However, after the base station 100a transmits a signal requesting the notification signal, the terminal station 101 transmits the notification signal. You can send it.

Next, the plurality of antennas 111 of the base station 100a receive notification signals transmitted from the terminal stations 101-1, 101-2, and 101-3, respectively. The propagation channel acquisition unit 113 acquires the propagation channel H ₁ , the propagation channel H ₂ , and the propagation channel H ₃ from the propagation channel information set in each notification signal output from the radio unit 112. The transmission weight calculation unit 131 calculates the broadcast and unicast weight corresponding to the combination of channels (destination terminal station 101) having the same transmission data from the acquired propagation channels H ₁ , H ₂ , and H ₃ . The transmission weight calculation unit 131 stores the broadcast weight and the unicast weight calculated corresponding to the channel combination in the information storage unit 116.

  The transmission signal generation unit 132 of the base station 100a performs broadcast weight according to the pattern of whether the OFDM symbols of the Data1, Data2, and Data3 of the terminal stations 101-1 and 101-2 and the terminal station 101-3 match. Then, the unicast weight is switched, and the weight calculation of Data1, Data2, and Data3 is performed, and a transmission signal is generated. Note that the transmission signal also includes information on matching and mismatching for each OFDM symbol. The coincidence / non-coincidence information may be location information indicating a coincidence or non-coincidence symbol and information of a combination of terminal stations, or may be codebook information that can specify location information and combination information of terminal stations.

  The radio unit 112 of the base station 100a simultaneously transmits the transmission signals generated by the transmission signal generation unit 132 via the plurality of antennas 111 from time t9 to time t10 when a certain time has elapsed from time t8.

  Next, when the radio unit 122 of the terminal station 101-1 decodes the radio packet signal of the transmission signal from the base station 100 received by the antenna 121 without error, the notification unit 124 generates the confirmation signal Ack. The notification unit 124 transmits the generated confirmation signal Ack to the base station 100a via the wireless unit 122 and the antenna 121 from time t11 to time t12 when a certain time has elapsed from time t10 after reception of the wireless packet signal.

  Similarly, when the radio unit 122 of the terminal station 101-2 decodes the radio packet signal of the transmission signal from the base station 100 received by the antenna 121 without error, the notification unit 124 generates the confirmation signal Ack. The notification unit 124 transmits the generated confirmation signal Ack to the base station 100a via the wireless unit 122 and the antenna 121 from time t13 to time t14 when a certain time has elapsed from time t12 after reception of the wireless packet signal.

  Similarly, when the radio unit 122 of the terminal station 101-3 decodes the radio packet signal of the transmission signal from the base station 100 received by the antenna 121 without error, the notification unit 124 generates the confirmation signal Ack. The notification unit 124 transmits the generated confirmation signal Ack to the base station 100a via the wireless unit 122 and the antenna 121 from time t15 to time t16 when a certain time has elapsed from time t14 after reception of the wireless packet signal.

The channel equalizers 127 of the terminal stations 101-1, 101-2, and 101-3 match each OFDM symbol included in the wireless packet signal output from the wireless unit 122 when the transmission signal is decoded. Based on the mismatch information, channel equalization is performed in symbol units.
The above is the second embodiment.

[3. Third Embodiment]
In the third embodiment, the method shown in the second embodiment is extended according to the combination pattern of whether or not the OFDM symbols of the signals transmitted from the base station to four or more terminal stations simultaneously match. Then, transmission weights corresponding to the combination of channels are calculated, and the transmission weight to be used is switched for each symbol depending on the combination in which the transmission signals addressed to the terminal stations match. This makes it possible to reduce signal errors.

[4. Fourth Embodiment]
In the fourth embodiment, when the base station that performs transmission using the BPSK or QPSK modulation scheme has different OFDM symbols for signals transmitted simultaneously to two terminal stations, the broadcast weight and Switch unicast weight. The unicast weight of this embodiment gives the same phase rotation amount as the phase rotation amount at the terminal station at the time of broadcast transmission. As a result, signal errors can be reduced, and information required for matching or mismatching for each OFDM symbol, which was previously required in the terminal station, is no longer necessary. It becomes possible.

  In the wireless communication system to which the wireless communication method according to the present embodiment is applied, the base station 100 and the terminal station 101 of the first embodiment shown in FIG. 1 are each a base station 100b shown in FIG. The terminal station 101b shown in FIG. Here, the two terminal stations 101b that perform wireless packet communication with the base station 100b are described as a terminal station 101b-1 and a terminal station 101b-2, respectively.

[4.1 Base station configuration]
FIG. 10 is a schematic block diagram showing the internal configuration of the base station 100b in the fourth embodiment, in which the same parts as those in the base station 100 in the first embodiment shown in FIG. The description is omitted.
As shown in the figure, the base station 100b includes a plurality of antennas 111, a radio unit 112, a propagation channel acquisition unit 113, a transmission weight calculation unit 141, a transmission signal generation unit 142, an information storage unit 116, And a network interface unit 117. As described above, the base station 100b shown in FIG. 2 differs from the base station 100 shown in FIG. 2 in that, instead of the transmission weight calculation unit 114 and the transmission signal generation unit 115, a transmission weight calculation unit 141 and a transmission signal generation unit. 142.

The transmission weight calculation unit 141 uses the propagation channel H ₁ or H ₂ input from the propagation channel acquisition unit 113 to calculate the broadcast weight and the unicast weight transmission weight using a calculation formula described later, and the information storage unit 116. Output to. In this example, the number of antennas 111 of the plurality of antennas 111 is 2. However, even when the number of antennas is 3 or more, the calculation can be performed in the same manner.

  The transmission signal generation unit 142 performs transmission signal generation processing such as convolutional coding, interleaving processing, subcarrier modulation, transmission weight calculation, and IFFT processing on the signal input from the network interface unit 117. However, in the transmission weight calculation, the transmission signal generation unit 142 compares the transmission signals addressed to the respective terminal stations 101b in units of OFDM symbols, and when the OFDM symbols are the same, the transmission weight is input using the broadcast weight input from the information storage unit 116. Performs transmission weight calculation. On the other hand, when the OFDM symbols are different, the transmission signal generation unit 142 performs transmission weight calculation using the unicast weight input from the information storage unit 116. The transmission signal generation unit 142 outputs a transmission signal generated as a result of the transmission signal generation processing to the radio unit 112.

  Subsequently, a calculation formula used by the transmission weight calculation unit 141 to generate a broadcast weight and a unicast weight will be described.

<Broadcast weight calculation formula>
First, the broadcast weight calculation formula will be described. A propagation channel obtained by combining a propagation channel H ₁ between the base station ₁₀₀ b and the terminal station 101 b- ₁ and a propagation channel H ₂ between the base station ₁₀₀ b and the terminal station 101 b-2 as shown in Expression (27) Let _Hb4 . H _b4 is decomposed as shown in Expression (28) by singular value decomposition.

Here, the broadcast weight W _b4 is expressed by Expression (32).

The transmission weight calculation unit 141 calculates the broadcast weight W _b4 using the propagation channels H ₁ and H ₂ input from the propagation channel acquisition unit 113 according to the above equations (27) to (32).

<Unicast weight calculation formula>
Next, a formula for calculating the unicast weight will be described. The unicast weight is a weight calculated from a zero forcing weight generally used in multiuser MIMO. However, the difference is that the unicast weight is calculated so that the phase rotation amount is the same as the phase rotation amount at the terminal station during broadcast transmission.

The phase rotation amounts θ ₁ and θ ₂ that the terminal stations 101 b-1 and 101 b-2 respectively use when the broadcast weight W _b4 is used are calculated by equations (33) and (34).

Here, ang (A) represents a function for calculating the phase rotation amount of A. As shown in Expression (36), the unicast weight W _u4 is obtained by performing an inverse matrix operation on the coupled propagation channel H _b4 expressed by Expression (27), and the amount of phase rotation is expressed as H _b4 ⁻¹ (Expression (35)). It is calculated by performing the correction.

The transmission weight calculation unit 141 calculates the unicast weight W _u4 using the propagation channels H ₁ and H ₂ input from the propagation channel acquisition unit 113 according to the above equations (33) to (36).
The above is the description of the configuration of the base station 100b.

[4.2 Terminal station configuration]
Next, the configuration of the terminal station 101b will be described.
FIG. 8 is a schematic block diagram showing the internal configuration of the terminal station 101b in the fourth embodiment. In this figure, the same parts as those of the terminal station 101 in the first embodiment shown in FIG.

  As shown in the figure, the terminal station 101b includes an antenna 121, a radio unit 122, a propagation channel acquisition unit 123, a notification unit 124, an information storage unit 125, a received signal acquisition unit 126, and a channel equalization unit. 151. As described above, the terminal station 101 b shown in the figure is different from the terminal station 101 shown in FIG. 4 in that a channel equalizing unit 151 is provided instead of the channel equalizing unit 127.

  The channel equalization unit 151 performs channel equalization for each OFDM symbol on the signal input from the radio unit 122 using the channel acquired by the propagation channel acquisition unit 123 regardless of whether the OFDM symbol matches or does not match. And output to the wireless unit 122.

  The above is the description of the configuration of the terminal station 101b.

[4.3 Example of communication procedure between base station 100b and terminal station 101b]
The time chart of the communication procedure to which the wireless communication method in the fourth embodiment is applied is the same as the time chart of the first embodiment shown in FIG. That is, the base station 100, the terminal station 101-1, and the terminal station 101-2 in FIG. 5 may be replaced with the base station 100b, the terminal station 101b-1, and the terminal station 101b-2 of this embodiment.

However, instead of the transmission weight calculation unit 114, the transmission weight calculation unit 141 calculates the broadcast weight W _b4 and the unicast weight W _u4 , and the transmission signal generation unit 142 instead of the transmission signal generation unit 115 matches the OFDM symbols. Based on whether or not the broadcast weight W _b4 and the unicast weight W _u4 are switched, the weight calculation of Data1 and Data2 is performed to generate a transmission signal.
Further, the channel equalization units 151 of the terminal stations 101-1 and 101-2 perform channel equalization for each OFDM symbol regardless of the match or mismatch for each OFDM symbol.

[5. Fifth Embodiment]
In the fifth embodiment, whether a base station that performs transmission using a QAM modulation scheme such as 16QAM or 64QAM has the same OFDM symbol for signals transmitted simultaneously to two terminal stations, and the OFDM symbol The broadcast weight and the unicast weight are switched for each symbol in accordance with the transmission power. The unicast weight of this embodiment gives the same phase rotation amount as the phase rotation amount at the terminal station at the time of broadcast transmission. As a result, in addition to being able to reduce the signal error, since the terminal station does not need information on matching or mismatching for each OFDM symbol, which is necessary in advance in the terminal station, as in the fourth embodiment. The amount of information required at the station can be reduced.

  The radio communication system to which the radio communication method according to the present embodiment is applied includes a base station 100 and a terminal station 101 according to the first embodiment shown in FIG. 4 is replaced with the terminal station 101b of the fourth embodiment.

[5.1 Base station configuration]
FIG. 12 is a schematic block diagram showing the internal configuration of the base station 100c in the fifth embodiment. The base station 100 in the first embodiment shown in FIG. 2 and the base station in the fourth embodiment shown in FIG. The same parts as those in 100b are denoted by the same reference numerals, and the description thereof is omitted.
As shown in the figure, the base station 100c includes a plurality of antennas 111, a radio unit 112, a propagation channel acquisition unit 113, a transmission weight calculation unit 141, a transmission signal generation unit 161, an information storage unit 116, A network interface unit 117. As described above, the base station 100c shown in the figure differs from the base station 100 shown in FIG. 2 in that the transmission weight calculation unit 141 in the fourth embodiment is provided instead of the transmission weight calculation unit 114, and the transmission signal The transmission signal generating unit 161 is provided instead of the generating unit 115.

  The transmission signal generation unit 161 performs convolutional coding, interleaving processing, subcarrier modulation, transmission weight calculation, IFFT processing, and the like on the signal input from the network interface unit 117. However, the transmission signal generation unit 161 performs QAM modulation such as 16QAM and 64QA in the subcarrier modulation. Further, in the transmission weight calculation, the transmission signal generation unit 161 compares the signals addressed to the respective terminal stations in units of OFDM symbols, and switches the broadcast weight or the unicast weight according to the transmission power of the OFDM symbol, thereby calculating the transmission weight. I do. The transmission signal generation unit 132 outputs a transmission signal generated as a result of the transmission signal generation process to the radio unit 112.

FIG. 13 shows an example of a 16QAM transmission signal using broadcast weight.
For example, in the case of 16QAM, the transmission signal generator 161 broadcasts signals when the signals addressed to the terminal stations 101b are symbols with high transmission power surrounded by a solid line shown in FIG. The weight calculation is performed using the weight. On the other hand, if the signals addressed to the terminal stations 101b are different signals, or the symbols are low in transmission power surrounded by a dotted line and are the same, the transmission signal generator 161 is unicast. The weight calculation is performed using the weight.
Here, an example of 16QAM is shown, but the same applies to 64QAM.

FIG. 14 is a diagram showing a received signal on the terminal station 101b side when broadcast weights and unicast weights are used for 16QAM transmission signals. As shown in the figure, when the broadcast is used and when the unicast is used, the amplitude received at the terminal station 101b is different, so that an error occurs in the symbol surrounded by the dotted line in FIG. However, no error occurs in the symbols surrounded by the solid line in FIG.
Therefore, for symbols with high received power enclosed by solid lines, broadcast weights are used if they match, and unicast weights are used if they do not match, but for symbols with low received power enclosed by dotted lines, Use unicast weights regardless of whether they match.

FIG. 15 shows an example of 64QAM signal comparison using broadcast weights.
As in the case of 16QAM shown in FIG. 13, the transmission signal generation unit 161 performs transmission weight calculation by dividing the symbol into a symbol surrounded by a solid line and a symbol surrounded by a dotted line. That is, the transmission signal generation unit 161 performs a weight calculation using the broadcast weight when the signal addressed to each terminal station 101b is a symbol with high transmission power surrounded by a solid line and is the same. . On the other hand, if the signals addressed to the terminal stations 101b are different signals, or the symbols are low in transmission power surrounded by a dotted line and are the same, the transmission signal generator 161 is unicast. The weight calculation is performed using the weight.
The above is the description of the configuration of the base station 100c.

[5.2 Terminal station configuration]
The terminal station of the fifth embodiment has the same configuration as the terminal station 101b of the fourth embodiment shown in FIG.

[5.3 Example of Communication Procedure between Base Station 100c and Terminal Station 101b]
The time chart of the communication procedure to which the wireless communication method in the fifth embodiment is applied is the same as the time chart of the first embodiment shown in FIG. That is, the base station 100, the terminal station 101-1, and the terminal station 101-2 in FIG. 5 may be replaced with the base station 100c, the terminal station 101b-1, and the terminal station 101b-2 of this embodiment.

However, instead of the transmission weight calculation unit 114, the transmission weight calculation unit 141 calculates the broadcast weight W _b4 and the unicast weight W _u4 as in the fourth embodiment. Then, instead of transmission signal generation section 115, transmission signal generation section 161 switches between broadcast weight W _b4 and unicast weight W _u4 based on the transmission power of the OFDM symbol and whether or not the data matches. Then, a weight calculation of Data1 and Data2 is performed to generate a transmission signal.
Similarly to the fourth embodiment, the channel equalizers 151 of the terminal stations 101-1 and 101-2 perform channel equalization for each OFDM symbol regardless of whether the OFDM symbols match or do not match.
The above is the fifth embodiment.

[6. effect]
In the conventional communication system using multi-user MIMO, since the total transmission power of the base station is limited, the transmission power per terminal station is limited and the inter-user interference becomes large. There is a problem in that the reception power of the desired signal is insufficient in the station and the transmission quality deteriorates.
In the above-described embodiment, the base station compares the signals transmitted simultaneously in multiuser MIMO on a symbol basis, and performs a broadcast weight calculation using broadcast weights for matching signals and unicast weights for different signals. .
As a result, the power efficiency of the matching signals is increased, and the transmission quality is improved as a whole.

[7. Supplementary items]
In addition, each function part of base station 100, 100a, 100b, 100c and terminal station 101, 101b in embodiment mentioned above may be implement | achieved by dedicated hardware (for example, wired logic etc.), The program may be recorded on a computer-readable recording medium, the program recorded on the recording medium is read into a computer system, and executed to realize the function. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). 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” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

100, 100a, 100b, 100c Base station 101, 101-1, 101-2, 101-3, 101b Terminal station 111 Multiple antennas 112 Radio unit 113 Propagation channel acquisition unit 114 Transmission weight calculation unit 115 Transmission signal generation unit 116 Information Storage unit 117 Network interface unit 121 Antenna 122 Radio unit 123 Propagation channel acquisition unit 124 Notification unit 125 Information storage unit 126 Received signal acquisition unit 127 Channel equalization unit 131 Transmission weight calculation unit 132 Transmission signal generation unit 141 Transmission weight calculation unit 142 Transmission Signal generation unit 151 Channel equalization unit 161 Transmission signal generation unit

Claims (6)

A transmitting station device that performs wireless communication simultaneously with a plurality of receiving station devices,
A plurality of antennas for transmitting and receiving radio signals;
A reception process for a radio signal from the receiving station apparatus received by the plurality of antennas and a transmission process for generating a radio signal from a plurality of transmission signals addressed to the receiving station apparatus and transmitting the signals simultaneously from the plurality of antennas A radio unit;
A propagation channel acquisition unit for acquiring propagation channel information of the receiving station device from the radio signal received and processed in the radio unit;
Using the propagation channel information of the plurality of receiving station apparatuses acquired by the propagation channel acquisition unit, a broadcast weight that is a transmission weight used when transmitting the same data and a transmission weight used when transmitting different data A transmission weight calculating unit that calculates a unicast weight according to a combination of transmission signals addressed to the plurality of receiving station devices,
The transmission signals transmitted simultaneously to the plurality of receiving station apparatuses are compared for each symbol, and the broadcast weight is used for the symbols having the same data according to the combination of the receiving station apparatuses having the same data. A transmission signal generation unit that performs a weight calculation, generates a transmission signal by performing a weight calculation using the unicast weight for symbols having different data, and outputs the transmission signal to the radio unit;
A transmitting station apparatus comprising: The transmission signal generation unit performs two-phase shift keying or four-phase shift keying to generate the transmission signal,
The transmission weight calculation unit uses the propagation channel information of the plurality of reception station devices acquired by the propagation channel acquisition unit, and performs the broadcast according to a combination in which transmission signals addressed to the plurality of reception station devices are the same. Calculating a weight and a unicast weight that gives the same phase rotation amount as the phase rotation amount in the receiving station device when transmission using the broadcast weight is performed;
The transmitting station apparatus according to claim 1. The transmission weight calculation unit uses the propagation channel information of the plurality of reception station devices acquired by the propagation channel acquisition unit, and performs the broadcast according to a combination in which transmission signals addressed to the plurality of reception station devices are the same. Calculating a weight and a unicast weight that gives the same phase rotation amount as the phase rotation amount in the receiving station device when transmission using the broadcast weight is performed,
The transmission signal generation unit generates the transmission signal by quadrature amplitude modulation representing a predetermined number of states or more, and in the case of a symbol whose transmission power is larger than a predetermined value, a transmission signal that is simultaneously transmitted to the plurality of receiving station devices Depending on the combination of the receiving station devices of the same destination, the weight calculation is performed using the broadcast weight for symbols having the same data, and the unicast weight is used for symbols having different data. When the calculation is performed and the transmission power is a symbol lower than a predetermined value, the transmission signal is generated by performing a weight calculation using the unicast weight, and is output to the radio unit.
The transmitting station apparatus according to claim 2. The transmission signal generation unit sets information indicating whether the broadcast weight or the unicast weight is used for each symbol in the transmission signal.
The transmitting station apparatus according to claim 1. The radio unit transmits a propagation channel information estimation signal from the plurality of antennas to the receiving station device,
The plurality of antennas receive radio signals in which propagation channel information measured by the receiving station apparatus based on propagation channel information estimation signals is set, and output the radio signals to the radio unit.
The transmitting station apparatus according to claim 1. A wireless communication method executed by a transmitting station device that performs wireless communication simultaneously with a plurality of receiving station devices,
A reception step of performing reception processing on a radio signal from the reception station apparatus received by a plurality of antennas;
A propagation channel acquisition step of acquiring propagation channel information of the receiving station device from the radio signal received and processed in the reception step;
Using the propagation channel information of the plurality of receiving station devices acquired in the propagation channel acquisition step, a broadcast weight that is a transmission weight used when transmitting the same data and a transmission weight used when transmitting different data A transmission weight calculating step for calculating a unicast weight according to a combination in which transmission signals addressed to the plurality of receiving station devices are the same;
The transmission signals transmitted simultaneously to the plurality of receiving station apparatuses are compared for each symbol, and the broadcast weight is used for the symbols having the same data according to the combination of the receiving station apparatuses having the same data. A transmission signal generation step of performing a weight calculation, performing a weight calculation using the unicast weight for symbols having different data, and generating the transmission signal;
A transmission step of performing a transmission process for simultaneously transmitting a plurality of transmission signals addressed to the receiving station device generated in the transmission signal generation step from the plurality of antennas;
A wireless communication method comprising:

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