JP4503539B2 - Wireless communication system and spatial multiplexing wireless communication method - Google Patents

Description

  The present invention provides a wireless communication system and spatial multiplexing wireless communication in which both a base station apparatus and a terminal station apparatus have a plurality of antennas, and one base station apparatus communicates with a plurality of terminal station apparatuses at the same frequency and the same timing. Regarding the method.

  In recent years, the IEEE802.11g standard, the IEEE802.11a standard, and the like are remarkable as high-speed wireless access systems using the 2.4 GHz band or the 5 GHz band. In these systems, an orthogonal frequency division multiplexing (OFDM) modulation scheme, which is a technique for stabilizing characteristics in a multipath fading environment, is used, and a transmission rate of 54 Mbps at the maximum is realized. However, the transmission rate here is a transmission rate on the physical layer, and the transmission efficiency in the MAC (Medium Access Control) layer is actually about 50 to 70%. It is about 30 Mbps. On the other hand, in the world of wired LANs, the provision of 100Mbps high-speed lines has become widespread due to the widespread use of Ethernet (registered trademark) 100Base-T interface and FTTH (Fiber to the home) using optical fiber in each home. In the world of wireless LAN, further increase in transmission speed is demanded.

  As a technology for that purpose, the MIMO technology is promising. The MIMO technology is such that different independent signals are transmitted on the same channel from a plurality of transmitting antennas on the transmitting station apparatus side, and signals are received using the same plurality of antennas on the receiving station apparatus side, and each transmitting antenna / receiving A transfer function matrix between antennas is obtained, and the independent signal transmitted from each antenna is estimated on the transmitting station apparatus side using this matrix, and data is reproduced.

Here, a case is considered where N signals are transmitted using N transmitting antennas and signals are received using M antennas. First, there are M × N transmission paths between the antennas of the transmission / reception station apparatus, and the transfer function when transmitted from the i-th transmitting antenna and received by the j-th receiving antenna is defined as h _{j, i.} A matrix of M rows and N columns where is a (j, i) th component is denoted as H. Further, a transmission signal from the i-th transmitting antenna is denoted by t _i , a column vector whose components are (t ₁ , t ₂ , t ₃ ,... T _N ) is Tx, and a received signal at the j-th receiving antenna is r _j (R ₁ , r ₂ , r ₃ ,... R _M ) as a column vector, Rx, and the thermal noise of the jth receiving antenna as n _j (n ₁ , n ₂ , n ₃ ,. A column vector having n _M ) as a component is denoted as n. In this case, the following relational expression holds.

Therefore, there is a need for a technique for estimating the transmission signal Tx based on the signal Rx received on the receiving station apparatus side. In this MIMO communication, communication can be most efficiently performed by using a propagation path information and transmitting a signal in an optimum situation with respect to the propagation path. For example, in MIMO transmission using an eigenmode SDM (Space Division Multiplexing) method described in “Wireless communication method and wireless communication system using the method” described in Patent Document 1, MIMO in the signal transmission direction is used. When the transfer function matrix H of the channel can be acquired on the transmitting station apparatus side, the transmission signal corresponding to this transfer function matrix is optimized. Specifically, the transfer function matrix H and its Hermitian conjugate matrix H ^{H (symbol} right shoulder "H" denotes the Hermitian conjugate) acquires diagonalizable unitary matrix U the product of this unitary matrix To convert the transmission signal and transmit the signal. The following relational expression is established between the unitary transformation matrix U and the transfer function matrix H.

  Here, the matrix Λ on the right side is a diagonal matrix in which only the diagonal component has a value and the other components are zero. By transmitting a signal by applying the unitary matrix U having such characteristics to the column vector Tx, (Equation 1) is converted as follows.

  By this conversion, the transmission signal is orthogonalized for each MIMO channel, and each transmission signal has good SNR characteristics for each MIMO channel even when a simple ZF (Zero Forcing) method is used in processing on the reception side. It is adjusted to become. Further, each column vector of this unitary matrix gives a coefficient (hereinafter referred to as “transmission weight”) for multiplying each antenna when the column vector Tx as a transmission signal is distributed to each transmission antenna. By using this transmission weight, orthogonal beam forming is performed for each MIMO channel, and the gain of the channel corresponding to each beam (eigen beam) becomes the eigenvalue of the eigenvector. Therefore, the upper limit of the channel capacity C of all MIMO channels is given by the following equation.

Here, B is the bandwidth, P _i is the total transmission power of the i-th MIMO channel, and σ ² is the noise power variance. From this equation, it is possible to apply a transmission mode of what transmission rate (here, a mode defined by a combination of a modulation scheme such as QPSK or 64QAM and an error correction coding rate is defined as a “transmission mode”), It can also be estimated how many MIMO channels can be multiplexed.

Incidentally, (Equation 4) transmit power P _i in need not be common values for all MIMO channel, also may be changed to the transmission mode for each MIMO channel. In general, it is possible to optimize the value of the P _i by using a technique called water filling. Among these, if there is a MIMO channel with P _i = 0, it means that it is more efficient to allocate power to other MIMO channels without using that channel for actual propagation. . That is, the number of MIMO multiplexing is set to be smaller than the original upper limit value. In this way, it is possible to determine the optimum value of the MIMO channel to be multiplexed.

The eigenmode SDM technique described above forms a transmission beam having directivity on the transmission side, and enables a signal to be multiplexed in space to be efficiently separated on the reception side. Here, normal MIMO communication, that is, communication between one transmitting station apparatus and one receiving station apparatus is called single user MIMO. Taking a wireless LAN or mobile phone as an example, the base station device (transmitting station device) is relatively large in size, and the terminal station device (receiving station device) side is a portable terminal and the size is much larger than the base station device Small. Even if a plurality of antennas for MIMO communication are mounted in such a small terminal, the distance between the antennas is short and the antenna correlation becomes very large. In this case, the value of the eigenvalue λ _i in (Equation 4) tends to be small, and the number of MIMO channels that can actually be used for communication is not so large. In such a case, while reducing the number of spatially multiplexed MIMO channels with each individual terminal, multi-user MIMO communication in which communication is performed on the same frequency channel simultaneously with a plurality of different terminals is effective.

  The multi-user MIMO system includes, for example, a base station device 101 and terminal station devices 102 to 104. At this time, the number of terminal station apparatuses actually accommodated by one base station apparatus is large, but several stations are selected (terminal station apparatuses 102 to 104) to perform communication. Each terminal station apparatus generally has a smaller number of transmission / reception antennas than the base station apparatus. For example, consider a case where communication (downlink) from the base station apparatus to the terminal station apparatus is performed. The base station apparatus 101 uses a plurality of antennas to form a plurality of directional beams. For example, consider a case in which three MIMO channels are assigned to each of the terminals 102 to 104 and nine signal sequences are transmitted as a whole. At that time, the signal transmitted to the terminal station apparatus 102 is adjusted so that the directivity gain becomes extremely low in the direction of the terminal station apparatus 103 and the terminal station apparatus 104. As a result, the terminal station apparatus 103 and the terminal station Suppresses interference with the device 104. Similarly, the signal transmitted to the terminal station apparatus 103 is adjusted so that the directivity gain becomes extremely low in the direction of the terminal station apparatus 102 and the terminal station apparatus 104. Similar processing is performed on the terminal station device 104. The reason why the directivity control is performed in this way is that, for example, in the terminal station apparatus 102, there is no way of knowing the information of the signals received by the terminal station apparatus 103 and the terminal station apparatus 104. I can't. That is, it is very difficult to separate all nine signal sequences in the reception process of only the terminal station apparatus 102 having only three antennas. Therefore, interference separation is performed in advance on the transmission side so that each terminal station device does not receive signals addressed to other terminal station devices. The above is the outline of the existing multi-user MIMO system.

Next, a method for forming a directional beam will be described below. First, in the multi-user MIMO system, a transfer function between the first reception antenna of the terminal station apparatus 102 and the j-th antenna of the base station apparatus 101 is denoted as h _1j . The row vector h ₁ is expressed as (h ₁₁ , h ₁₂ , h ₁₃ ,..., H ₁₈ , h ₁₉ ) using transfer functions related to all antennas j = 1 to 9 of the base station apparatus 101. Similarly, the transfer functions of the second receiving antenna and the third receiving antenna of the terminal station apparatus 102 and the base station apparatus 101 are h _2j and h _3j , and the corresponding row vectors h ₂ and h ₃ are (h ₂₁ , h ₂₂ , h ₂₃ ,..., H ₂₈ , h ₂₉ ), (h ₃₁ , h ₃₂ , h ₃₃ ,..., H ₃₈ , h ₃₉ ). The receiving antennas of the terminal station device 103 and the terminal station device 104 are assigned similar serial numbers, and the row vectors h ₄ to h ₉ are (h ₄₁ , h ₄₂ , h ₄₃ ,..., H ₄₈ , h ₄₉ ) to (h ₉₁ , _h92 , _h93 , ..., _h98 , _h99 ). In addition, nine systems of signals transmitted by the base station apparatus 101 are denoted as t ₁ to t _9, and column vectors having these as components are represented by Tx ^[all] = (t ₁ , t ₂ , t ₃ ,..., T ₈ , t ₉ ) ^T Here, the letter T on the right shoulder indicates transposition of a vector or a matrix. Similarly, received signals at the nine antennas of the terminal station apparatuses 102 to 104 are denoted as r ₁ to r ₉ , and a column vector having these components as components Rx ^[all] = (r ₁ , r ₂ , r ₃ ,..., R ₈ , r ₉ ) ^T. Finally, a matrix having the row vectors h _{1 to} h ₉ as the first to ninth row components is denoted as an overall transfer function matrix H ^[all] . When expressed in this way, the following relational expression holds for the entire system.

  This corresponds to (Equation 1) in single user MIMO. Similarly, in order to perform the transmission directivity control as shown in (Expression 3), a 9 × 9 transmission weight matrix W is introduced, and (Expression 3) is rewritten as follows.

Furthermore, the transmission weight matrix W is decomposed into column vectors _{w 1 ~w 9, W = (} w 1, w 2, w 3, ... w 8, w 9) when that notation expressed as follows.

Here, for example, the multiplications of the six row vectors h _{4 to} h ₉ and the three column vectors w _{1 to} w ₃ are all zero (the sum of the multiplication of each component, which is different from the inner product in the case of a complex vector). Given that choose _w 1 ~w ₃ in. Similarly, the product of the row vector _h 1 to h ₃ and _h 7 to h ₉ column vector _w 4 to w _6, all the product of a row vector _h 1 to h ₆ column vector _w 7 to w ₉ becomes zero I will choose as follows. Then, the matrix of 9 rows and 9 columns shown in (Equation 7) can be expressed as follows using 9 sub-matrices of 3 rows and 3 columns.

Here, the sub-matrices H ^[1] , H ^[2] and H ^[3] are 3-by-3 matrices, and in this equation, what is indicated by Q is a 3-by-3 matrix with all components being zero. . By selecting a transformation matrix W that satisfies such conditions, (Equation 8) can be decomposed into the following three relational expressions.

_{^{Here, Tx [1] = (t}} 1, t 2, t 3) T, Tx [2] = (t 4, t 5, t 6) T, Tx [3] = (t 7, t 8, t ^{_{9) T, Rx [1]}} = (r 1, r 2, r 3) T, Rx [2] = (r 4, r 5, r 6) T, Rx [3] = (r 7, r 8, r ₉ ) ^T In this way, it can be regarded as three single user MIMO communications.

Next, an example of a method for determining the transmission weight vectors w _{1 to} w ₉ will be described below. As a procedure, transmission weight vectors w _{1 to} w ₃ for the terminal station apparatus 102 are determined, and transmission weight vectors w _{4 to} w ₆ for the terminal station apparatus 103 and transmission weight vectors w _{7 to} w ₉ for _the terminal station apparatus 104 are sequentially determined. To decide. As a first step, determine the six basis vectors _e 4 to e ₉ of the six-dimensional subspace constituted by six row vector _h 4 to h ₉ in the terminal station. There are various methods other than the Gram Schmidt orthogonalization method. The Gram Schmidt orthogonalization method will be described as an example here.

First, paying attention to one vector h ₄ , a vector having an absolute value of 1 in this direction is set as a base vector e ₄ .

Here, (h ₄ h ₄ ^h ) is a scalar quantity that means the square of the absolute value of the same vector, and means that h ₄ is normalized. Next, paying attention to the vector h ₅ , a vector h ₅ ′ in which the component in the e ₄ direction is canceled is obtained from the vector, and further normalized.

Here, Σ _(i) in (Equation 15) means the total sum for integer i of 4 ≦ i ≦ j−1 (j is an integer of 4 to 9). In other words, this means canceling the already determined component in the direction of the base vector. In this way, six basis vectors e _{4 to} e ₉ can be obtained.

Next, as a second step, transmission weight vectors w _{1 to} w ₃ for the terminal station apparatus 102 are obtained. First, the row vector _h 1 to h _3, to cancel the components of the six-dimensional subspace formed by e 4 to e _9. Specifically, it can be expressed by the following formula.

Here, j is an integer of 1 to 3, and Σ _(i) in (Equation 17) means the sum for the integer i of 4 ≦ i ≦ 9. Appropriate orthogonalization processing is performed on the vectors h ₁ ′ to h ₃ ′ thus obtained. For simplicity, the Gram Schmidt orthogonalization is used here as an example, but other methods may be used. The Gramschmitt orthogonalization method has already been described in (Equation 12) to (Equation 16) and will not be described in detail, but can be obtained as follows.

Three basis vectors e ₁ to e ₃ of the three-dimensional space thus obtained are obtained. Furthermore, by obtaining a transposed vector of the complex conjugate vector of this basis vector, that is, a Hermitian conjugate vector, w ₁ = e ₃ ^H , w ₂ = e ₂ ^h , W ₃ = e ₃ ^{h and} a transmission weight vector (column vector) ) Is obtained. Through the processing from (Equation 12) to (Equation 22), transmission weight vectors w _{1 to} w ₃ for the terminal station apparatus 102 can be determined. As a third step, the same processing is performed on the terminal station device 103 and the terminal station device 104, and as a result, all transmission weight vectors w _{1 to} w ₉ are obtained. The above is how to determine the transmission weight matrix in the conventional method.

FIG. 6 is a diagram showing a flow of calculating the transmission weight matrix W in the prior art.
First, in calculating the transmission weight matrix, a transfer function matrix H to all terminals is acquired (S102). When a serial number is assigned to the destination terminal and the number is expressed as k, k is first initialized (S103). Further, k is counted up (S104), the partial transfer function (indicated here as H ^main for convenience) (S105) for the terminal station device 102 corresponding to k = 1 of interest, and other destinations A partial transfer function matrix (in this case, expressed as H ^sub for convenience) is extracted (S106).

Further, an orthogonal basis vector of a subspace composed of each row vector of H ^sub is calculated, and this is set as {e _j } (S107). Next, as a process corresponding to (Equation 17), the component related to the basis vector {e _j } obtained in the process S107 is canceled from the partial transfer function H ^main for the terminal station apparatus 102 of interest, and this is replaced with a matrix H ^~. the ^main (S108). Further, as processing corresponding to (Equation 18) to (Equation 22), an orthogonal basis vector of a subspace composed of row vectors of the matrices H 1 to ^main is calculated, and this is set as {e _i } (S109). Thereafter, a transmission weight vector {w _i } relating to a signal addressed to the terminal station apparatus 102 is determined as a Hermitian conjugate vector (column vector) of each vector of {e _i }. Here, it is determined whether or not the transmission weight vectors of all destination terminal station devices have been verified (S111). If there are remaining terminal station devices, the processing from step S104 to step S110 is repeated. If the transmission weight vectors of all the destination terminal stations have been verified, the transmission weight matrix W is determined as a matrix having the transmission weight vector {w _i } as each column vector (S112), and the processing is completed (S112). S113).

  It should be noted that all the descriptions so far are based on a single carrier system, and only one transmission weight matrix has to be obtained. Currently, MIMO technology is attracting attention in wireless LANs, etc., but standard wireless LANs such as IEEE802.11a and IEEE802.11g employ OFDM (Orthogonal Frequency Division Multiplexing) modulation method using multicarrier. Yes. In the case of a multi-user MIMO system using the OFDM modulation scheme, it is necessary to individually perform the above processing on all subcarriers.

FIG. 7 is a diagram showing a configuration example (in the case of a single carrier) on the transmission station apparatus side in the prior art. This figure is a configuration example of a transmitting station apparatus for realizing the various processes described above.
In FIG. 7, 111a is data dividing circuit, 112a-1~112a-L preamble applying circuit ,, 113a-1~113a-L modulation circuit, 114a are transmitted signal conversion circuit, the _{115a-1~115a-M T} radio unit, _{116a-1~116a-M T} is transmission and reception antennas, 117a is the transfer function matrix acquiring circuit, 118a transmission weight calculating circuit, 119a denotes a spatial multiplexing condition determining circuit. Here, the total number of spatially multiplexed signal sequences is L (L> 2, L is an integer), and the radio units (115a-1 to 115a-M _T ) and the transmission / reception antennas (116a-1 to 116a-M _T ) the number of systems was _{M T.} In addition, although the configuration is on the transmission station apparatus side, generally, the base station apparatus and the terminal station apparatus have both a transmission function and a reception function, and the diagram shown here extracts only the functions related to the transmission. It has become a thing. Therefore, the function for reception is not specified here. In addition, here, downlink multi-user MIMO is assumed and the base station apparatus is implicitly assumed on the transmission station apparatus side, but the base station apparatus is not necessarily required.

The radio units (115a-1 to 115a-M _T ) and the transmission / reception antennas (116a-1 to 116a-M _T ) in the figure individually receive sequential signals. For example, the signal received by the transmission / reception antenna 116a-1 is subjected to frequency conversion by the radio unit 115a-1, and after predetermined processing, the signal is transmitted to each receiving station apparatus by the transfer function matrix acquisition circuit (117a). Collect function information. Regarding the transfer function information collection method here, there are various methods such as a method of feeding back transfer function information from the receiving station apparatus side using a control channel, and a method of appropriately exchanging a preamble signal for propagation channel estimation in both transmission and reception directions. A method can be selected, and any method may be used. The transfer function matrix information acquired for each receiving station apparatus in this way is recorded and managed in the transfer function matrix acquisition circuit (117a). The spatial multiplexing condition determination circuit (119a) manages which receiving station apparatuses are simultaneously spatially multiplexed and how the multiplicity is set when transmitting a signal. Here, when the receiving station apparatus to be spatially multiplexed and the multiplicity are defined, the transmission weight calculation circuit (118a) transmits the transmission weight sequence vectors (w1, w2, w3,..., W _MT corresponding to the above-described conditions. ₋₁ , w _MT ). These pieces of information are input to the transmission signal conversion circuit (114a).

On the other hand, when the data to be transmitted is input to the data dividing circuit (111a), the receiving station apparatus that performs spatial multiplexing and the multiplicity determined by the spatial multiplexing condition determining circuit (119a) (L multiplexing is used for all receiving station apparatuses). The data is divided into L systems according to the above conditions. Each signal is input to a preamble adding circuit (112a-1 to 112a-L), a predetermined channel estimation preamble is added, and input to a modulation circuit (113a-1 to 113a-L). The modulation circuit (113a-1 to 113a-L) performs predetermined modulation processing, and the output is input to the transmission signal conversion circuit (114a). Here, based on the vector group calculated by the transmission weight calculation circuit (118a), a conversion matrix W = (w) for a transmission signal vector whose components are output signals from the modulation circuits (113a-1 to 113a-L). _{1, w 2, w 3,} ..., w MT-1, w MT) is multiplied by. Signal converted _{M T} lineage This multiplication is frequency-converted by the radio unit _{(115a-1~115a-M T)} , it is transmitted through the transmitting and receiving antennas _{(116a-1~116a-M T)} . The above is an example of a single carrier radio system.

FIG. 8 is a diagram illustrating a conventional configuration example on the transmission station apparatus side in a multi-user MIMO system using the OFDM modulation scheme.
In the case of a multi-user MIMO system using the OFDM modulation scheme, the same processing is performed for each subcarrier as shown in FIG. As a difference from FIG. 7 of FIG. 8, each signal series is divided for each subcarrier by the data dividing circuit (111b), and the same processing is performed for each subcarrier. In addition, processing corresponding to the preamble adding circuit (112a-1 to 112a-L), the modulation circuit (113a-1 to 113a-L), and the transmission signal conversion circuit (114a) is performed in parallel on each subcarrier. Then, inverse Fourier transform processing performed IFFT circuits _{(120a-1~120a-M T)} , via the radio unit _{(115b-1~115b-M T)} , the transmitting and receiving antennas _{(116b-1~116b-M T)} Sent.

Next, FIG. 9 shows a configuration example of a receiving station apparatus in the prior art.
Here, description will be made assuming a downlink in which the terminal station apparatus is the receiving station apparatus. In this case, even in the case of a multi-user MIMO system, since the signal directed to the other receiving station apparatus is controlled by the transmission directivity control on the transmitting station apparatus side, the receiving station apparatus is a normal single station. The reception process may be performed similarly to the user MIMO. Here, a case where three antennas are provided will be described as an example.

  9, 121-1 to 121-3 are receiving antennas, 122-1 to 122-3 are radio units, 123 is a channel estimation circuit, 124 is a received signal management circuit, 125 is a transfer function matrix management circuit, and 126 is a matrix. Arithmetic circuits # 1, 127 are matrix arithmetic circuits # 2, 128 are hard decision circuits, 129 is a data synthesis circuit, and 130 is a MIMO reception processing unit. First, the first receiving antenna 121-1 to the third receiving antenna 121-3 individually receive received signals. The received signal is input to the channel estimation circuit 123 via the radio units 122-1 to 122-3. The transfer function between the i-th transmitting antenna and the j-th receiving antenna is acquired here by the channel estimation circuit 123 from the reception state of a predetermined preamble signal given by the transmitting side. The transfer function matrix acquired in this way is managed as a transfer function matrix H by the transfer function matrix management circuit 125.

In the matrix operation circuit # 1 (126), H ^H , H ^H H, (H ^H H) ⁻¹ , (H ^H H) ⁻ based on the transfer function matrix H managed by the transfer function matrix management circuit 125. ¹ H ^H is obtained sequentially by calculation. On the other hand, the data signal following the preamble signal is input to the received signal management circuit 124 for each symbol. The reception signal management circuit 124 temporarily manages the reception signal vector Rx that includes the reception signals (r ₁ , r ₂ , r ₃ ) of each antenna as components. This received signal vector is multiplied by (H ^H H) ⁻¹ H ^H obtained by the matrix operation circuit # 1 (126) in the matrix operation circuit # 2 (127). Since this signal is a signal in which noise is added to the transmission signal vector Tx, the signal is determined by the hard decision circuit (128), and the signal of each symbol and each system is synthesized by the data synthesis circuit (129). The original user data is reproduced and output.

For the sake of simplicity in the above description, the processing in the matrix operation circuit # 1 (126) and the matrix operation circuit # 2 (127) assumes a simple MIMO signal detection method called a ZF (Zero Forcing) method. Although described, MMSE (Minimum Mean Square Error) method, MLD (Maximum Likelihood Detection) method, etc. may be used. Further, the case where the transfer function matrix H other than the square matrix is assumed and the pseudo inverse matrix (H ^H H) ⁻¹ H ^H is used has been described as an explanation of the ZF method. However, if the transfer function matrix H is a square matrix, it is simple. Alternatively, an inverse matrix of the transfer function matrix H may be used. Furthermore, although it is assumed that the hard decision circuit (128) performs the hard decision, it is also possible to combine the error correction and use the soft decision. Furthermore, when the OFDM modulation method is used, the same processing is performed for each subcarrier. In addition, for convenience of the following description, an area surrounded by a dotted line is referred to as a MIMO reception processing unit.
International Publication No. WO2005 / 055484A1 Pamphlet

  Here, in the wireless communication system using the conventional multi-user MIMO communication as described above, a transfer function of communication with all terminal station apparatuses with which the base station apparatus can communicate is estimated, and various terminal station apparatuses For the combination, the transmission rate of information communicated by each terminal station device is obtained, and spatial multiplexing scheduling is performed so as to satisfy the total transmission rate or the service class required by each terminal station device. As a result, as the number of terminal station apparatuses increases, the amount of calculation for determining the scheduling exponentially increases, and there is a problem that a large processing load is applied to the base station apparatus.

  Accordingly, an object of the present invention is to provide a wireless communication system and a spatial multiplexing wireless communication method capable of reducing the processing load of a base station apparatus in a wireless communication system using multi-user MIMO communication.

  In order to achieve the above object, the present invention provides spatial multiplexing in which adaptive modulation / coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas. A wireless communication system that performs transmission, wherein a base station device includes means for communicating with at least one terminal station device using at least one spatial channel, and the base station device among the plurality of terminal station devices A terminal station apparatus waiting to start communication with a station apparatus estimates the transmission rate when one or more of the spatial channels being communicated is received by itself, and is currently communicating on that spatial channel. Means for estimating the data transmission rate being transmitted, and a transmission rate when the one or more spatial channels are received by the own device is higher than the data transmission rate at which the current communication is being performed. If it can communicate in degrees, it is a wireless communication system, characterized by comprising means for requesting a spatial multiplexing in the spatial channel to the base station apparatus.

Further, the present invention is a wireless communication system for performing spatial multiplexing transmission in which adaptive modulation and coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas. And means for communicating with at least one or more terminal station devices using at least one or more spatial channels, and the base station device with the base station device among the plurality of terminal station devices. A terminal station apparatus waiting for communication start, a means for estimating a first transfer function between a beam used by the terminal station apparatus currently communicating and the base station apparatus and the own apparatus; and the first Means for identifying the number of spatial channels s ₂ that maximizes the transmission rate when the device and the base station device communicate with each other using the transfer function, and the number of spatial channels s during communication is expressed as s ₂ ( _s> s ₂₎ before in the case of changing to The first transmission rate between the currently communicating terminal station apparatus and the base station apparatus is set to the number of spatial channels s in which the base station apparatus and the currently communicating terminal station apparatus are communicating with each beam. Means for estimating based on the second transfer function between the terminal station apparatus currently communicating and the modulation method, coding method, and signal-to-noise ratio of the spatial channel; and the first transfer function Means for calculating a second transmission rate when the own apparatus and the base station apparatus are communicatively connected using the number of spatial channels s ₂ , and the first transmission rate and the second transmission rate In the case where the currently communicating terminal station apparatus communicates with the base station apparatus by the number of spatial channels s-s ₂ and the own apparatus communicates with the base station apparatus by the number of spatial channels s ₂ Means for calculating a total transmission rate; When the calculated total transmission rate is higher than the transmission rate when the communicating terminal station device communicates with the base station device using the number of spatial channels s, the base station device a wireless communication system, characterized by comprising means for requesting the spatial multiplexing of the channel s _2.

  The present invention also relates to a wireless communication system for performing spatial multiplexing transmission in which adaptive modulation / coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas. A wireless communication method for spatial multiplexing, wherein a base station apparatus communicates with at least one terminal station apparatus using at least one spatial channel, and communicates with the base station apparatus among the plurality of terminal station apparatuses. The terminal station apparatus waiting for communication starts estimating the transmission rate when one or more of the spatial channels being communicated is received by the own apparatus, and the data transmission currently being communicated on that spatial channel. Estimating the speed, and when the one or more spatial channels are received by the own device, the transmission speed is higher than the data transmission speed currently being communicated. If that is the spatial multiplexing wireless communication method characterized by requesting a spatial multiplexing in the spatial channel to the base station apparatus.

The present invention also relates to a wireless communication system for performing spatial multiplexing transmission in which adaptive modulation / coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas. A wireless communication method for spatial multiplexing, wherein at least one base station apparatus communicates with at least one terminal station apparatus using at least one spatial channel, and the base station apparatus among the plurality of terminal station apparatuses The terminal station apparatus waiting to start communication with the station apparatus estimates the first transfer function between the terminal station apparatus currently communicating and the base station apparatus used for the communication and the own apparatus, When the own apparatus and the base station apparatus communicate with each other using the first transfer function, the number of spatial channels s ₂ that maximizes the transmission rate is specified, and the number of spatial channels s in communication is defined as s−s ₂ ( _s> s ₂₎ in the case of changing to The first transmission rate between the currently communicating terminal station apparatus and the base station apparatus is determined by using each beam of the number of spatial channels s with which the base station apparatus and the currently communicating terminal station apparatus are communicating. And the second transfer function between the terminal station apparatus currently in communication and the modulation method, coding method, and signal-to-noise ratio of the spatial channel, and the first transfer function is And using the number of spatial channels s ₂ to calculate a second transmission rate when the own device and the base station device are in communication connection, and based on the first transmission rate and the second transmission rate Total transmission when the currently communicating terminal station apparatus communicates with the base station apparatus by the number of spatial channels s-s ₂ and the own apparatus communicates with the base station apparatus by the number of spatial channels s ₂ Calculate the speed, and the currently communicating terminal station device When the calculated total transmission rate is higher than the transmission rate when communicating with the base station apparatus using the number of spatial channels s , the base station apparatus performs spatial multiplexing on the spatial channel s _2. It is a wireless communication method for spatial multiplexing characterized by requiring .

  According to the present invention, a terminal station apparatus waiting for communication start autonomously requests a base station apparatus to perform spatial multiplexing scheduling when the transmission speed requested by the terminal apparatus can be satisfied. Thereby, it is possible to reduce the processing load of the spatial multiplexing scheduling of the base station apparatus.

A wireless communication system according to a first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a wireless communication system according to the first embodiment of the present invention.
In this figure, 10 is a base station apparatus, 21 is a terminal station apparatus communicating with the base station apparatus, and 22 is a terminal station apparatus waiting for the start of communication with the base station apparatus. And the base station apparatus 10 is communicating with the terminal station apparatus 21 in communication using two spatial channels. At this time, it is assumed that the base station apparatus 10 forms two beams in radio communication with the terminal station apparatus 21, and independently applies adaptive modulation and coding according to transmission quality to each beam. Here, in the case of using a method in which encoding is realized for both spatial channels by a single encoder, the following operation is performed only for adaptive modulation.

FIG. 2 is a diagram illustrating a processing flow of the base station apparatus of the wireless communication system according to the first embodiment.
First, in the terminal station device 22 waiting for communication start, transmission quality estimation (step S101) for each of the two spatial channels in the wireless communication between the base station device 10 and the terminal station device 21 in communication, The modulation scheme and coding rate used in the spatial channel are estimated (step S102). For estimation of transmission quality, a transfer function is estimated from a method of obtaining SNR from the reception level of each spatial channel (transmission quality estimation method 1), or a correlation between a known signal (training signal) sequence transmitted on each spatial channel and the received signal. In addition, there is a method (transmission quality estimation method 2) for estimating an error rate when a spatial separation algorithm (MLD, MMSE, ZF algorithm, etc.) is applied to each of a modulation scheme and a coding scheme that can be set. .

  Here, the estimation of the modulation scheme and coding rate used in communication using two spatial channels is based on the modulation scheme and coding scheme used for communication with the terminal station apparatus 21 with which the base station apparatus 10 performs communication. Is received by the terminal station device 22 waiting for the start of communication, and the transfer function estimating unit 201 of the terminal station device 22 waiting for the start of communication decodes the signal. Alternatively, the terminal station device 21 that is in communication requests the base station device 10 for the modulation method and the coding method in uplink communication, and the base station device 10 is the terminal station device 22 that is waiting for the start of communication of the modulation method and the coding method. May be estimated by decoding the signal by the transfer function estimation unit 201 of the terminal station device 22. Here, in general, the coding rate is uniquely determined when the coding method is determined. In addition, the modulation method may be specified from the amplitude fluctuation of the signal during communication. Next, the transmission rate estimation unit 203 of the terminal station device 22 waiting for communication start determines the transmission rate of the signal being communicated between the terminal station device 21 and the base station device 10 that are in communication with the estimated modulation method. Estimate from coding rate (step S103). Here, the transmission rate is estimated by estimating the transmission rate as KR when the amount of information transmitted by the estimated modulation scheme is Kbps and the estimated coding rate is R.

  Next, the terminal station device 22 waiting for communication start is set to perform communication at a transmission rate higher than the transmission rate obtained from the modulation scheme and coding rate used by the terminal station device 21 in communication for wireless communication. If it is, it is determined whether or not the device can communicate with a quality higher than the desired transmission quality (step S104). For example, when the transmission quality estimation method 2 is used, the communicable transmission rate estimation unit 202 has already obtained the relationship between the error rate, the modulation method, and the coding method, and therefore, the combination of the modulation method and the coding method. Among them, a modulation scheme capable of obtaining a transmission rate higher than the estimation result of the transmission rate, which is “a transmission rate calculated from a modulation scheme / coding rate used by the terminal station device 21 currently in communication for wireless communication”, Specify a combination of encoding methods. Then, the communicable transmission rate estimation unit 202 refers to the error rate when the combination of the specified modulation method and coding method is used, and the value is set by the own device (terminal station device 22 waiting for communication start). It is determined whether or not the transmission quality (error rate) is satisfied. If the transmission quality is satisfied, the communicable transmission rate estimation unit 202 determines that communication at a higher transmission rate is possible.

  Further, when the transmission quality estimation method 1 is used, a modulation scheme / coding scheme applicable to the own apparatus is extracted from “a predetermined relationship between required SINR, modulation scheme and coding scheme”. Here, “predetermined relationship between required SINR, modulation scheme, and encoding scheme” is, for example, “if SINR is between xdB (decibel) and ydB, use modulation scheme P and encoding scheme Q”. It is a relationship. When the modulation method and the coding method extracted in this way are used, a transmission rate higher than the “transmission rate calculated from the modulation method and coding rate used by the terminal station apparatus 21 currently communicating for wireless communication”. It is determined whether or not. Then, the spatial multiplexing request determination unit 204 of the terminal station device 22 waiting for communication starts the “transmission rate calculated from the modulation scheme and coding rate used by the terminal station device 21 currently communicating for wireless communication” by the above processing. If it is determined that communication at a higher transmission rate is possible, at the start of communication with the base station apparatus 10, a part of the spatial channel used by the terminal station apparatus 21 in communication for communication is determined. A request signal for requesting allocation as a spatial channel is transmitted (step S105). That is, the terminal station device 22 waiting for communication start autonomously requests the base station device 10 for spatial multiplexing scheduling when the transmission rate requested by the terminal device 22 can be satisfied. Thereby, the load of the base station apparatus 10 can be reduced.

FIG. 3 is a diagram showing an outline of the processing result of the wireless communication system according to the first embodiment.
Next, a specific example of the processing result of the wireless communication system will be described.
In FIG. 3, it is assumed that the terminal station device 21 is communicating with the base station device 10 and the terminal station device 22 is waiting to start communication with the base station device 10. Further, it is assumed that the terminal station apparatus 21 transmits information of 1 Mbps using two spatial channels. Further, it is assumed that the terminal station device 22 can use only one spatial channel. In addition, the terminal station device 22 waiting to start communication can transmit at 20 Mbps when communicating with the base station device 10 by itself using one spatial channel, When the terminal station device 21 and the terminal station device 22 waiting for communication start communicate with the base station device 10 using one spatial channel, the terminal station device 21 in communication is 1 Mbps and the terminal waiting for communication start It is assumed that the station device 22 can transmit at 15 Mbps.

  In such a situation, when the terminal station device 22 tries to communicate with the base station device 10, the terminal station device 22 waiting for the communication start communicates with the terminal station device 22 using one spatial channel, and the remaining When the terminal station apparatus 21 communicates using one spatial channel, the total transmission speed can be communicated at a transmission rate higher than the transmission speed at which the terminal station apparatus 21 communicates using two spatial channels. Determine whether it is possible. In this example, the terminal station apparatus 21 is currently communicating at 2 Mbps using two spatial channels, whereas the terminal station apparatus 22 uses one spatial channel and the remaining one spatial channel. Since the total transmission rate when 21 communicates is 15 + 1 = 16 Mbps, it is determined that the total transmission rate is improved. Based on this result, the terminal station device 22 waiting for communication start notifies the base station device 10 of a request for communication using one spatial channel to the base station device 10, and the base station device 10 that has received the request next In communication after the frame, one spatial channel is allocated to the terminal station apparatus 22 waiting for communication start, and the remaining one spatial channel is allocated to the terminal station apparatus 21 to perform communication.

  That is, in the conventional method, after the communication for one frame of the terminal station apparatus 21 is completed, the terminal station apparatus 22 communicates with the base station apparatus 10 independently as the next frame. However, in the present invention, the terminal station apparatus 21 continuously transmits frames using one spatial channel, and the base station apparatus waits for the other spatial channel originally used for communication with the terminal station apparatus 21 to start communication. To the terminal station apparatus 22 and continuously transmit frames using the spatial channel to which the terminal station apparatus 22 is allocated. As a result, the transmission speed of (1 × 2 + 15 × 2) / 2 = 16 Mbps can be improved in the time for transmitting one frame. In this way, it is possible to improve the total transmission rate when communicating with a plurality of terminal devices using a plurality of spatial channels without requiring a new frequency or time timing.

FIG. 4 is a diagram showing a configuration of a wireless communication system according to the second embodiment of the present invention.
FIG. 5 is a diagram showing a processing flow of the base station apparatus of the wireless communication system according to the second embodiment.
Next, the radio | wireless communications system by the 2nd Embodiment of this invention is demonstrated with reference to drawings. 4 are the same as those in FIG. 1, and therefore, the same reference numerals are used for the description.

  The terminal station device 22 waiting to start communication estimates a transfer function between the beam used by the terminal station device 21 and the base station device 10 in communication and the own device (step S201). Based on the estimation result of the function, the transmission speed when the local apparatus (terminal station 22 waiting for communication start) is preferentially connected to the base station apparatus 10 is obtained (step S202). The total transmission rate when each of the device 21 and the terminal station device 22 communicates with the base station device 10 is higher than the transmission rate when the currently communicating terminal station device 21 communicates with the base station device 10 alone. It is determined whether to increase (step S203), and if it increases, a transmission request is made to the base station apparatus 10 (step S204). In this process, when the terminal station device 22 waiting to start communication starts communication with the base station device 10, the terminal station device 21 in communication changes the directivity used for communication with the base station device 10. In other words, the total transmission rate is improved by changing the transmission weight vector described in the prior art. However, the control is complicated as compared with the first embodiment.

First, in the terminal station device 22 waiting for communication start, the transfer function estimation unit 201 estimates a transfer function of communication between the beam and each antenna of the own device in communication between the terminal station device 21 currently communicating and the base station device 10. . Further, the transmission rate estimation unit 203 performs singular value decomposition on the estimated transfer function, and if the respective beams are combined and multiplexed, the own device (the terminal station device 22 waiting for communication start) becomes the base station device 10. Calculate the maximum transmission rate when communicating with Here, when the terminal station device 21 currently communicating is communicating with the base station device 10 using the transmission weight matrix W described in the conventional method, the terminal station device 21 and the base station device 10 are communicating with each other. The transfer function estimated between the signal beam and each antenna of its own apparatus is expressed as H ₂ W. When the terminal station apparatus 21 currently in communication is communicating with the base station apparatus 10 using s spatial channels, the transfer function H ₂ W is a matrix having the number of columns s. Here, H ₂ is a transfer function estimated between each antenna of the base station apparatus 10 and the terminal station apparatus 22 waiting to start communication. And when singular decomposition is performed on this transfer function H ₂ W,

It can be expressed as. In this case k ₂ th diagonal element of D ₂ is, when was the largest among the diagonal elements of D _2, using the k ₂ th column vector v _k2 of V _2, the communication start waiting terminal station device 22 transmission weight vector to be used for communicating with the base station apparatus 10 and _{Wv k2.} Here, the weight vector Wv _k2 used when the terminal station device 22 waiting for communication start communicates with the base station device 10 is s _{2 in} the communication between the terminal station device 22 waiting for communication start and the base station device 10. When the spatial channel is a vector to be used, among the diagonal elements of D ₂ , elements having a large value are sequentially selected by the number of spatial channels to be used, and the eigenvector v _k (k = k = 1-s) and use that vector to derive the transmission weight vector W _vk . Then, when communicating with the base station apparatus 10, the terminal station apparatus 22 waiting to start communication specifies that s ₂ spatial channels are formed by performing transmission using the transmission weight vector W _vk .

Next, the terminal station device 22 waiting to start communication changes the number of spatial channel vectors used for communication with the base station device 10 by the currently communicating terminal station device 21 from s to s−s ₂ . The transmission rate is calculated using the following calculation method based on the transfer function between each beam that the terminal station device 21 in communication with the base station device 10 is communicating with and the terminal station device 21. First, the modulation scheme and coding scheme selected in each spatial channel in communication between the base station apparatus 10 and the terminal station apparatus 21 are estimated by the method described in the first embodiment, and a predetermined “SNR or SINR is selected. SNR and SINR are estimated from a list of modulation schemes and encodings to be performed. The values of SNR and SINR of each spatial channel obtained in this way are defined as γ1 to γs. Further, a matrix Γ having diagonal elements from γ1 to γs is formed. Based on this Γ, (Equation 24) is calculated.

Next, the matrix A is further subjected to singular decomposition, and each singular value is regarded as SINR. Refer to a predetermined “SNR or SINR and a list of modulation schemes / encodings to be selected” and correspond to each singular value. By determining the modulation scheme / coding and determining the sum of the transmission rates when each modulation scheme / coding scheme is used, the terminal station apparatus 21 currently communicating changes the number of spatial channel vectors from s to s−s. Estimate the transmission rate when the number is changed to _two .

  Also, the terminal station device 22 waiting for communication start is based on the estimation result of the transfer function between the beam used by the terminal station device 21 and the base station device 10 in communication and the own device. The transmission speed when the communication connection with the base station apparatus 10 is preferentially given (the terminal station apparatus 22 waiting for communication start) is obtained. Then, the total transmission speed when the terminal devices of the terminal station device 21 and the terminal station device 22 communicate with the base station device 10 is calculated, and the currently communicating terminal station device 21 communicates with the base station device 10 alone. It is determined whether the transmission rate is higher than the transmission rate in the case where the transmission rate is higher.

In this way, the terminal station device 22 waiting to start communication communicates with the base station device 10, and the terminal channel device 21 previously connected for communication reduces the spatial channel vector used for communication with the base station device 10. Thus, the sum of the transmission speeds between the base station apparatus 10 and each terminal station apparatus can be obtained. Here, the spatial multiplexing numbers s and s ₂ used in each terminal station device described above may be determined in advance according to the priority of the terminal station device, and each multiplexing number may be determined using the spatial multiplexing number as a parameter. The total number of combinations may be performed to detect the number of spatial multiplexing that maximizes the total transmission rate.

  Further, when the terminal station device 21 in communication is communicating by a method other than the method of performing spatial multiplexing in an orthogonal space such as an eigen beam, the terminal station device 21 further communicates with the base station device 10. The phase of the transfer function between each beam and the antenna of the terminal station device 21 in communication is introduced as an uncertain parameter, and the total transmission rate when this uncertain parameter is changed is evaluated. The total transmission rate is estimated using the value, x% value (x is a predetermined value), minimum value, and the like. By doing so, in the present invention, complicated scheduling can be easily and reliably performed. Note that the above-described method can be applied as it is even when there are a plurality of terminal station devices 21 in communication and a plurality of terminal station devices 22 waiting to start communication in the wireless communication system.

  The base station apparatus and terminal station apparatus described above have a computer system inside. The process described above is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing this program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  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.

It is a figure which shows the structure of the radio | wireless communications system by 1st Embodiment. It is a figure which shows the processing flow of the base station apparatus of the radio | wireless communications system by 1st Embodiment. It is a figure which shows the outline | summary of the radio | wireless communications system process result by 1st Embodiment. It is a figure which shows the structure of the radio | wireless communications system by 2nd Embodiment. It is a figure which shows the processing flow of the base station apparatus of the radio | wireless communications system by 2nd Embodiment. It is a figure which shows the flow of calculation of the transmission weight matrix W in a prior art. It is a figure which shows the structural example (in the case of a single carrier) by the side of the transmission station apparatus in a prior art. It is a figure which shows the example of a conventional structure by the side of the transmission station apparatus in the multiuser MIMO system using an OFDM modulation system. The structural example of the receiving station apparatus in a prior art is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Base station apparatus 21 ... Terminal station apparatus in communication 22 ... Terminal station apparatus waiting for communication start 201 ... Transfer function estimation part 202 ... Communication possible transmission rate estimation part 203 ... Transmission rate estimation unit 204... Spatial multiplexing request determination unit

Claims (4)

A wireless communication system for performing spatial multiplexing transmission, in which adaptive modulation / coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas,
A base station device comprising means for communicating with at least one or more terminal station devices using at least one or more spatial channels;
Among the plurality of terminal station devices, a terminal station device waiting to start communication with the base station device,
Means for estimating a transmission rate when one or more of the spatial channels in communication is received by the own device, and estimating a data transmission rate currently communicated on the spatial channel;
If the transmission rate when the one or more spatial channels are received by the own device can be communicated at a transmission rate higher than the data transmission rate at which the current communication is performed, the spatial channel is transmitted to the base station device. And a means for requesting spatial multiplexing in the wireless communication system. A wireless communication system for performing spatial multiplexing transmission, in which adaptive modulation / coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas,
Means for communicating with at least one terminal station apparatus using at least one spatial channel with at least one base station apparatus;
Among the plurality of terminal station devices, a terminal station device waiting to start communication with the base station device,
Means for estimating a first transfer function between the beam used by the terminal station apparatus currently communicating and the base station apparatus and the own apparatus;
Means for identifying the number of spatial channels s ₂ that maximizes the transmission rate when the device and the base station device communicate with each other using the first transfer function ;
The first transmission rate between the currently communicating terminal station apparatus and the base station apparatus when the number of spatial channels s during communication is changed to s−s ₂ (s> s ₂ ) A second transfer function between each beam of the number of spatial channels s in communication between the station apparatus and the currently communicating terminal station apparatus and the currently communicating terminal station apparatus, and a modulation scheme of the spatial channel Means for estimating based on the coding scheme and the signal-to-noise ratio;
Means for calculating a second transmission rate when the own apparatus and the base station apparatus are connected for communication using the number of spatial channels s ₂ using the first transfer function ;
Based on the first transmission rate and the second transmission rate, the currently communicating terminal station device communicates with the base station device using the number of spatial channels s−s ₂ , and the own device is the base station. Means for calculating a total transmission rate when communicating with the apparatus by the number of spatial channels s ₂ ;
When the calculated total transmission rate increases from the transmission rate when the currently communicating terminal station device communicates with the base station device using the number of spatial channels s, the base station device Means for requesting spatial multiplexing in the spatial channel s ₂ . Spatial multiplexing wireless communication in a wireless communication system performing spatial multiplexing transmission in which adaptive modulation and coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas A method,
The base station apparatus communicates with at least one or more terminal station apparatuses using at least one or more spatial channels,
Among the plurality of terminal station devices, the terminal station device waiting to start communication with the base station device is
Estimating the transmission rate when the own device receives one or more spatial channels among the spatial channels being communicated, estimating the data transmission rate currently being communicated on the spatial channel,
If the transmission rate when the one or more spatial channels are received by the own device can be communicated at a transmission rate higher than the data transmission rate at which the current communication is performed, the spatial channel is transmitted to the base station device. A wireless communication method for spatial multiplexing, characterized in that spatial multiplexing is required. Spatial multiplexing wireless communication in a wireless communication system performing spatial multiplexing transmission in which adaptive modulation and coding is performed for each spatial channel between a base station apparatus having a plurality of antennas and a plurality of terminal station apparatuses having a plurality of antennas A method,
Communicate with at least one terminal station apparatus using at least one spatial channel with at least one base station apparatus;
Among the plurality of terminal station devices, the terminal station device waiting to start communication with the base station device is
Estimating a first transfer function between the beam used by the terminal station apparatus currently communicating and the base station apparatus and its own apparatus,
Specify the number of spatial channels s ₂ that maximizes the transmission rate when the device and the base station device communicate using the first transfer function ,
The first transmission rate between the currently communicating terminal station apparatus and the base station apparatus when the number of spatial channels s during communication is changed to s−s ₂ (s> s ₂ ) A second transfer function between each beam of the number of spatial channels s in communication between the station apparatus and the currently communicating terminal station apparatus and the currently communicating terminal station apparatus, and a modulation scheme of the spatial channel , Estimation based on coding scheme, signal-to-noise ratio,
Using the first transfer function to calculate the second transmission rate when the base station apparatus and the base station apparatus are connected for communication using the number of spatial channels s ₂ ,
Based on the first transmission rate and the second transmission rate, the currently communicating terminal station device communicates with the base station device using the number of spatial channels s−s ₂ , and the own device is the base station. Calculate the total transmission speed when communicating with the device by the number of spatial channels s ₂ ,
When the calculated total transmission rate increases from the transmission rate when the currently communicating terminal station device communicates with the base station device using the number of spatial channels s, the base station device A wireless communication method for spatial multiplexing, wherein spatial multiplexing on the spatial channel s ₂ is requested .

Images