JP2011254148A - Communication system, transmitter, transmission control method, transmission control program, and processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve transmission efficiency.SOLUTION: An order determination part a122 determines an order of signals so that at least one signal of signals to be transmitted to receivers with many streams has higher priority than signals to be transmitted to receivers with fewer streams.

Description

  The present invention relates to a communication system, a transmission device, a transmission control method, a transmission control program, and a processor.

  In recent years, standardization of fourth-generation mobile communication has been promoted, and various studies have been made for the purpose of improving the transmission speed of a downlink (communication from a base station apparatus to a terminal apparatus). One possible solution is to increase the bandwidth of the system. However, increasing the bandwidth of the system has limited frequency resources, so this solution is limited. Therefore, a MIMO (Multiple-Input Multiple-Output) technique that can spatially multiplex a plurality of signals using the same time and the same frequency without expanding the frequency band has been studied as a useful technique. The MIMO technique is a spatial multiplexing transmission technique in which a plurality of antennas are provided for both transmission and reception, and different signal sequences are simultaneously transmitted from a plurality of transmission antennas.

  In this downlink MIMO transmission, MU-MIMO (Multi User-MIMO), in which a base station apparatus having a plurality of antennas and a plurality of terminal apparatuses communicate simultaneously, is attracting attention as a technique for improving throughput. In MU-MIMO, signals are simultaneously transmitted from a base station apparatus to a plurality of terminal apparatuses, and thus interference occurs between signals between terminal apparatuses. Thus, a technique is known in which the base station apparatus performs precoding in advance so as to remove interference caused by signals addressed to other terminal apparatuses.

  As precoding, for example, a technique of removing a part of inter-user interference by blocking a propagation path and using THP (Tomlinson-Harashima Precoding) for remaining inter-user interference is proposed (for example, non-patent). Reference 1).

Hiroki Mori, Ahide Aoki, Yasuhiko Tanabe, “Proposal of Stream Allocation Method in Multiuser MIMO System Using THP”, Shingaku Sodai, B-5-54, Mar. 2008.

By the way, in the precoding described in the cited document 1, a receiving apparatus whose order of removing interference by THP is later deteriorated in reception quality than a preceding receiving apparatus or a receiving apparatus that does not remove interference. There were drawbacks.
In other words, there is a problem in that the number of errors increases in the receiving apparatus after the order, and the transmission efficiency of the communication system may deteriorate.

  The present invention has been made in view of the above points, and provides a communication system, a transmission device, a transmission control method, a transmission control program, and a processor that can improve transmission efficiency.

  (1) The present invention has been made to solve the above problems, and the present invention includes a plurality of receiving apparatuses and a transmitting apparatus that spatially multiplexes and transmits signals addressed to the plurality of receiving apparatuses. In the communication system provided, the transmission device determines an order related to the spatial multiplexing based on information on the number of signal sequences of signals addressed to each reception device.

  (2) Further, the present invention is characterized in that, in the communication system described above, the transmitting apparatus uses precoding based on a nonlinear operation for the spatial multiplexing.

  (3) Further, in the communication system according to the present invention, the transmission device may receive at least one signal addressed to a reception device having a large number of signal sequences indicated by information on the number of signal sequences of the signal, as the signal. It is characterized in that it is determined in an order earlier than a signal addressed to a receiving apparatus having a small number of streams.

  (4) In the communication system according to the present invention, the information related to the number of signal sequences of the signal is information indicating the number of signal sequences of the signal notified to the transmitting device by the receiving device. And

  (5) Further, the present invention provides a transmitting apparatus that spatially multiplexes and transmits signals addressed to a plurality of receiving apparatuses, based on information related to the number of signal sequences of signals addressed to each receiving apparatus. It is characterized by determining.

  (6) Further, the present invention provides a transmission control method in a transmission apparatus that spatially multiplexes and transmits signals addressed to a plurality of reception apparatuses, wherein the transmission apparatus is based on information on the number of signal sequences of signals addressed to each reception apparatus. A transmission control method characterized by comprising a step of determining an order related to the spatial multiplexing.

  (7) Further, the present invention relates to the spatial multiplexing based on information on the number of signal sequences of signals addressed to each receiving device to a computer of a transmitting device that spatially multiplexes and transmits signals addressed to a plurality of receiving devices. It is a transmission control program for executing a means for determining the order.

  (8) Further, the present invention is a processor characterized in that the order related to the spatial multiplexing is determined based on information related to the number of signal sequences of signals addressed to each receiving apparatus.

  According to the present invention, the communication system can improve transmission efficiency.

It is the schematic which shows an example of the communication system which concerns on the 1st Embodiment of this invention. It is a schematic block diagram which shows the structure of the base station apparatus which concerns on this embodiment. It is a follow chart which shows the operation | movement of the order determination process which concerns on this embodiment. It is a schematic block diagram which shows the structure of the terminal device which concerns on this embodiment. It is the schematic which shows an example of the communication system which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram which shows the structure of the base station apparatus which concerns on this embodiment. It is a schematic block diagram which shows the structure of the multiple signal production | generation part which concerns on this embodiment. It is the schematic which shows an example of allocation of the signal generation order which concerns on this embodiment. It is the schematic which shows another example of allocation of the signal generation order which concerns on this embodiment. It is a schematic block diagram which shows the structure of the base station apparatus which concerns on the 3rd Embodiment of this invention. It is a schematic block diagram which shows the structure of the terminal device which concerns on this embodiment. It is the schematic which shows an example of allocation of the signal generation order which concerns on this embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of a communication system according to the first embodiment of the present invention. In this figure, the communication system includes a base station apparatus a1 and a plurality of terminal apparatuses B1 to BN. In FIG. 1, N = 3, and in this embodiment, N = 3. However, the present invention is not limited to this, and N = 2 or N> 3.
The base station apparatus a1 includes K transmission antennas a161 to a16K. In FIG. 1, K = 4 and K = 4 in the present embodiment, but the present invention is not limited to this, and 1 <K <4 or K> 4. The base station apparatus a1 spatially multiplexes and transmits signals addressed to a plurality of terminal apparatuses using the same frequency at the same time.
The terminal device Bn (n = 1 to N; each of the terminal devices Bn is also referred to as a terminal device b1) includes J _n receiving antennas Bn1 to BnJ _n and receives a signal transmitted from the base station device a1. It is to be 1 in _{J 1, J 2, J 3} = 2, in the present embodiment and _{J 1, J 2, J 3} = 2, the present invention is not limited _thereto, J _{1, J} 2, J ₃ > 2 may be sufficient. Further, J ₁ = J ₂ = J ₃ may not be satisfied, and in this case, any one of J ₁ , J ₂ , and J ₃ may be 1.

In MU-MIMO transmission, interference occurs between signals to terminal apparatuses B1 to BN. The base station apparatus a1 preliminarily transmits a signal addressed to a certain terminal apparatus so as to eliminate interference caused by signals addressed to other terminal apparatuses. Here, the base station apparatus a1 determines the order in precoding based on the number of streams (signal sequences) (also referred to as ranks) of the terminal apparatus BN. For example, in the terminal apparatus Bn having the number of streams of “1”, signals of the same signal sequence may be received by J _n antennas, or may be received by any one antenna. Precoding refers to converting a plurality of transmission signals into signals that can be spatially multiplexed by applying some processing to the signal that should be transmitted.

<About the base station apparatus a1>
FIG. 2 is a schematic block diagram showing the configuration of the base station apparatus a1 according to this embodiment. In this figure, a base station apparatus a1 includes a reception antenna a111, a radio unit a112, an upper layer unit a12, encoding units a131-1 to a131-K, modulation units a132-1 to a132-K, a multiplexed signal generation unit a14, A second reference signal generation unit a151, a first reference signal generation unit a152, a filter multiplication unit a153, a signal multiplexing unit a154, radio units a155-1 to a155-K, and transmission antennas a161 to a16K are configured. The upper layer unit a12 includes a stream number acquisition unit a121, an order determination unit a122, an application unit a123, and an order change unit a124. The multiplexed signal generation unit a14 includes a filter calculation unit a141, an interference calculation unit a142, a subtraction unit a1433-3 to a143-K, a modulo calculation unit a144-3 to a144-K, and a filter multiplication unit a145.
The base station apparatus a1 spatially multiplexes and transmits signals using BT (Block Triangulation) -THP.

The base station apparatus a1 receives signals transmitted from the terminal apparatuses B1 to BN using the reception antenna a111. A signal received by the receiving antenna a111 is input to the wireless unit a112.
The radio unit a112 generates a baseband signal by down-converting the input signal and performs A / D (Analog to Digital) conversion. The radio unit a112 demodulates the A / D converted signal, and outputs the demodulated information to the upper layer unit a12. Here, the radio unit a112 outputs the reception quality information (CQI; Channel Quality Information) of each terminal apparatus Bn among the demodulated information to the reception quality acquisition unit a123, and the propagation path information (CSI; Channel State Information). Is output to the filter calculation unit a141. The reception quality information of each terminal device Bn is information indicating the reception quality at each terminal device of the signal from the base station device a1, and for example, the distance from the base station device a1 to each terminal device Bn, the base station Depending on whether there is an obstacle between the terminal and the terminal, whether the terminal is located indoors or outdoors. Specifically, when the reception quality information represents a reception SNR (Signal-to-Noise Ratio) in each terminal apparatus Bn, the terminal apparatus Bn located in the vicinity of the base station apparatus a1 Since the signal is received with a high SNR, the reception quality indicated by the reception quality information also has a high value. On the contrary, in the terminal device Bn located at a location away from the base station device a1, the reception quality indicated by the reception quality information is a low value.
The radio unit a112, among the information after demodulation, and outputs the stream number information indicating the number of streams t _n of the terminal device Bn respectively, and a receiving antenna number information indicating the number of receive antennas J _n to the stream number obtaining unit a121 .

  The base station apparatus a1 determines the coding rate and the modulation scheme of information addressed to each terminal apparatus Bn (also addressed to the receiving antenna Bn1) based on the reception quality information and propagation path information in each terminal apparatus Bn. decide. In addition, the base station apparatus a1 transmits the determined coding rate of information addressed to each terminal apparatus Bn and control information indicating a modulation scheme to each terminal apparatus Bn.

The stream number acquisition unit a121 of the upper layer unit a12 acquires the stream number information and the reception antenna number information input from the radio unit a112, and outputs them to the order determination unit a122. The number-of-streams acquisition unit a121, based on the number-of-streams information input from the wireless unit a112, and other information such as traffic information or reception quality information of each terminal device Bn, the number of streams t of each terminal device Bn. _n may be determined. In this case, the base station apparatus a1 has the stream number information indicating the determined number of streams t _n, and notifies the terminal Bn.
The order determination unit a122 receives the reception quality information of each terminal apparatus Bn from the radio unit a112, and receives the stream number information and the reception antenna number information from the stream number acquisition unit a121. The order determination unit a122 determines the terminal devices Bn to be spatially multiplexed and the signal generation order c of those terminal devices Bn based on the input information (referred to as order determination processing).

Specifically, the order determination unit a122 determines that the signal generation order c of the terminal device Bn having the larger number of streams t _n indicated by the stream number information is earlier than the signal generation order c of the terminal device Bn having the smaller number of streams t _n. The signal generation order c is determined so that In this case, the order determination unit a122, the signal generation sequence c small terminal Bn of the stream number t _n is the signal generated order so than the signal generation sequence c stream number t _n is greater terminals Bn, made after c will also be determined.
Here, the order determination unit a122, if the stream number t _n have multiple terminals Bn are the same for their terminals Bn, the signal of the receiving antenna number J _n is small terminals Bn indicating the reception antenna number information generating sequence c is from the signal generating sequence c of the number of receive antennas J _n is large terminals Bn, determines the signal generating sequence c so earlier.
In addition, when there are a plurality of terminal apparatuses Bn having the same number of streams t _{n and the} same number of receiving antennas J _n , the order determination unit a122 selects the terminal apparatus Bn having a low reception quality indicated by the reception quality information for those terminal apparatuses Bn. The signal generation order c is determined so that the signal generation order c comes before the signal generation order c of the terminal device Bn having high reception quality.
In the order determination process, the signal generation order c based on the number of reception antennas _Jn and the reception quality is not limited to the above process. For example, the order determination unit a122 may determine the signal generation order c so that the signal generation order c of the terminal apparatus Bn with high reception quality precedes the signal generation order c of the terminal apparatus Bn with low reception quality. . Also, order determining section a122 may determine the signal generating sequence c based on the number of receive antennas J _n or information other than the reception quality information, for example, the terminal device Bn stream number t _n are the same random The order of selection may be determined as the signal generation order c.
The order determination unit a122 outputs the identification information of the terminal device Bn that has determined the signal generation order c and the signal generation order information indicating the signal generation order c to the order conversion unit a124 and the filter calculation unit.

The application unit a123 outputs the information addressed to each terminal device Bn input via the network to the order conversion unit a124. In addition, the identification information of the terminal device Bn is given to the information addressed to the terminal device Bn.
The order conversion unit a124 selects information addressed to the terminal apparatus Bn whose identification information matches the identification information input from the order determination unit a122. The order conversion unit a124 rearranges the information addressed to the selected terminal device Bn based on the signal generation order c input from the order determination unit a122. Hereinafter, the information for the j-th receiving antenna of the terminal device Bn, the signal generation order c of which is the m-th terminal device Bn, is represented as information D _i (i = j + Σ _{s ≦ m−1} J _s ). . The order conversion unit a124 outputs the information D _i to the encoding unit a131-i.
Here, when the number of streams t _n of the terminal device Bn is smaller than the number of reception antennas J _n , the order conversion unit a124 duplicates the information D _i (i = 1 to J _n −t _n ), and each of the information D _{i + 1.} ˜D _Jn . Thus, the signal information _{D i (i = 1~J n -t} n) is to be multiplexed.

The encoding unit a131-i encodes the information D _i addressed to the terminal device Bn input from the application unit a123 at the encoding rate determined by the base station device a1 and the encoding rate of the information addressed to the terminal device Bn. Turn into. Encoding section a131-n, respectively, and outputs the information _{d i} which is encoded in the modulation unit a132-i.
Modulation unit a132-i is information d _i which is input from the coding section a131-i, a coding rate base station apparatus a1 has decided modulated with modulation method information to the terminal device Bn. Examples of the modulation method include QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation). The modulation unit a132-i outputs the modulated signal s _i to the multiplexed signal generation unit a14.

The filter calculation unit a141 generates a propagation matrix H from the propagation path information input from the wireless unit a112. Here, i rows and k columns elements H _ik (k = 1 to N) of the propagation matrix H are propagation path estimation values between the transmission antenna a16k of the base station apparatus a1 and the reception antenna Bmj of the terminal apparatus Bm. . The filter calculating unit a141 arranges the elements H _ik in the order of i based on the identification information of the terminal device Bn and the signal generation order information input from the order determining unit a122.
When the filter calculation unit a141 multiplies the generated propagation matrix H, the matrix M is calculated so that the matrix is triangulated downward. Here, block triangulation means that one matrix of non-diagonal components (referred to as non-diagonal blocks) in a block is 0 when the matrix component is an element (block) for each terminal device b1. (See equation (23)). The filter calculation unit a141 outputs the calculated matrix M as a filter coefficient to the filter multiplication unit a145 and the filter multiplication unit a153.
The filter calculation unit a141 outputs information indicating the matrix A as a result of multiplying the propagation matrix H by the matrix M to the interference calculation unit a142.

The interference calculation unit a142 uses the matrix A indicated by the information input from the filter calculation unit a141 to use another signal s _e (e) for the signal s _i input from the modulation unit a132-i (i = 3 to K). ≠ i), the interference signal f _i is sequentially generated. Specifically, the interference calculation unit a142 uses the matrix A to calculate the interference coefficient matrix C = {Diag (A)} ⁻¹ A−I. Here, Diag (X) represents a matrix in which the non-diagonal block of the matrix X is zero.

The interference calculation unit a142 sequentially generates a vector s _i ′ having the signal s _i input from the modulation unit a132-i as a component.
The interference calculation unit a142 generates the interference signal f _i by multiplying the interference coefficient matrix C by the vector s _i ′. Specifically, the interference calculation section a142 the interference signal _{f 3} is the interference coefficient matrix _{C (s 1, s 2,} 0,0) the third component of the matrix obtained by multiplying the ^T, the interference signal _{f 4} is A fourth component of the matrix obtained by multiplying the interference coefficient matrix C by (s ₁ , s ₂ , 0, 0) ^T is generated.
Note that in the example of FIG. 2, the interference calculation section a142 is a generating only vectors _{s I} 'to the signal _{s i} as a component, if the terminal is in N or more, the Modulo arithmetic unit A144- ( The signals s _{J1 + 1} to s _I-JN may be input from J ₁ +1) to a144- (I−J _N ). In this case, the interference calculation section a24-23 is sequentially generates a vector _{s I} 'to the signal _{s i} and the signal _s J1 + _{1 ~s I-JN} and components.
Interference calculation section a142 the generated interference signal _{f i,} respectively, and outputs to the subtraction section a143-i.

The subtraction unit a143-i receives the signal s _i from the modulation unit a132-i, and receives the interference signal f _i from the interference calculation unit a142. The subtraction unit a143-i subtracts the interference signal f _i from the signal s _i . Subtraction section a143-i outputs a signal _s i -f _i after subtraction Modulo arithmetic unit a 144-i.
Modulo arithmetic unit a 144-i, to the signal _s i -f _i input from the subtraction section a143-i, Modulo operation base station apparatus a1 is based on the modulation scheme of each terminal Bm determining the (non-linear operation) Do. The modulo calculator a144-i outputs the signal s _i ′ after the modulo calculation to the interference calculator a142 and the filter multiplier a145.

The filter multiplication unit a145 receives the signal s _i (referred to as signal s _i ′) input from the modulation unit a132-i (i = ₁ to J _{m = 1} ) and the modulo calculation unit a144-i (i = J _{m = 1 to} K), a vector s _i ′ = (s ₁ ′, s ₂ ′,..., S _I ′) ^T having the signal s _i ′ input as a component is generated. The filter multiplier a145 multiplies the generated vector s _i ′ by the filter coefficient indicated by the information input from the filter calculator a141. The filter multiplication unit a246 outputs the vector component signal after multiplication to the signal multiplexing unit a154.

  The second reference signal generation unit a151 generates a pilot signal (reference signal) transmitted from each of the transmission antennas a16k. The pilot signal is a signal known between the base station apparatus a1 and the terminal apparatus b1 (the waveform is stored in advance), and the transmission antennas a161 to a161 are used so that pilot signals transmitted from a plurality of transmission antennas do not interfere with each other. a164 is orthogonalized. Note that the pilot signal generated by the second reference signal generation unit a151 is used in each terminal apparatus b1 to estimate the propagation path information to be notified to the base station apparatus a1. The second reference signal generation unit a151 outputs the generated pilot signal to the signal multiplexing unit a154.

The first reference signal generation unit a152 generates a pilot signal. The pilot signal is a signal known between the base station apparatus a1 and the terminal apparatus b1 (the waveform is stored in advance), and the transmission antennas a161 to a161 are used so that pilot signals transmitted from a plurality of transmission antennas do not interfere with each other. a164 is orthogonalized. Note that the pilot signal generated by the first reference signal generation unit a152 is used in each terminal apparatus b1 to separate the spatially multiplexed signals. The first reference signal generation unit a152 outputs the generated pilot signal to the filter multiplication unit a153.
The filter multiplier a153 multiplies the filter coefficient indicated by the information input from the filter calculator a141 by the pilot signal input from the first reference signal generator a152. The filter multiplier a153 outputs the multiplied signal to the signal multiplexer a154.

The signal multiplexing unit a154 multiplexes the signals input from the filter multiplication unit a145, the second reference signal generation unit a151, and the filter multiplication unit a153. Here, the pilot signal input from the second reference signal generation unit a151 and the signal input from the filter multiplication unit a153 are orthogonalized and multiplexed in the time domain, for example. In addition, the signal multiplexing unit a154 arranges the signal of the remainder calculation information indicating that the modulo calculation is performed in the band assigned to the terminal device Bm (m ≧ 2) in the control information signal. The present invention is not limited to this, instead of the modulo operation information may transmit information indicating that the stream number t _n is not the smallest terminals.
After performing such signal multiplexing, the signal multiplexing unit a154 places a signal generated from the signal s _i ′ and output in a band to be transmitted by the transmission antenna a16i.
The radio unit a155-k performs D / A (Digital to Analog) conversion on the signal input from the signal multiplexing unit a154. The radio unit a155-k upconverts the converted signal to a radio frequency and transmits it to the terminal device Bn via the transmission antenna a16k.

<About order determination processing>
Hereinafter, the order determination process performed by the order determination unit a122 will be described in detail.
FIG. 3 is a follow chart showing an example of the operation of the order determination process according to the present embodiment. The order determining unit a122 stores terminal device information (terminal identification information, stream number information, reception antenna number information, and reception quality information) for each piece of identification information of the terminal device Bn.

(Step S101) order determination section a122 has a large order of the stream numbers _{t n} indicated stream number information, rearranges the terminal apparatus information. Thereafter, the process proceeds to step S102.
(Step S102) order determination section a122 determines whether there is the same terminal device information of the stream number _{t n.} When it is determined that there is the same terminal device information with the number of streams t _n (YES), the process proceeds to step S103. On the other hand, if it is determined that there is no terminal device information with the same number of streams t _n (NO), the process proceeds to step S108.

(Step S103) order determination section a122 has the stream number _{t n} in step S103 and extracts the determined terminal device information and the same. Thereafter, the process proceeds to step S104.
(Step S104) order determination section a122 the extracted terminal information in step S103, for each stream number _{t n,} rearranges the small order of the number of receive antennas _{J n} indicated in the received antenna number information. Thereafter, the process proceeds to step S105.
(Step S105) order determination section a122 has the same terminal device information of the number of receive antennas _{J n} determines whether or not there are a plurality of. If it is determined that there is the same terminal device information of the number of receiving antennas _{J n} (YES), the process proceeds to step S106. On the other hand, when it is determined that there is no same terminal device information of the number of receiving antennas _{J n} (NO), the process proceeds to step S108.

(Step S106) order determination section a122 has the number of receive antennas _{J n} in step S105 and extracts the determined terminal device information and the same. Thereafter, the process proceeds to step S107.
(Step S107) The order determination unit a122 rearranges the terminal device information extracted in Step S106 into the order of low reception quality in the number of streams t _n and the number of reception antennas J _n . Thereafter, the process proceeds to step S108.

(Step S108) The order determination unit a122 substitutes an initial value “0” for the selection number x. Thereafter, the process proceeds to step S109.
(Step S109) The order determination unit a122 substitutes x + 1 for the selection number x. Then, it progresses to step S110.
(Step S110) The order determination unit a122 determines whether the selection number x is an odd number (x = 2y−1; y is a natural number). If it is determined that the selection number x is an odd number (YES), the process proceeds to step S111. On the other hand, if it is determined that the selected number x is not an odd number (x = 2y) (NO), the process proceeds to step S112.

(Step S111) The order determination unit a122 assigns the signal generation order c = C−y−1 to the terminal device information whose order rearranged in steps S101, S104, and S107 is the yth largest. That is, the order determination unit a122 assigns the signal generation order c = C−y−1 to the terminal device Bn having the yth largest number of streams t _n . Note that the value of C is determined in step S115. Thereafter, the process proceeds to step S113.
(Step S112) The order determination unit a122 assigns the signal generation order c = y to the terminal apparatus information whose order rearranged in steps S101, S104, and S107 is the yth smallest. In other words, the order determination unit a122, the stream number _{t n} is a small terminal unit Bn to y-th, allocates the signal generating sequence c = y. Thereafter, the process proceeds to step S113.

(Step S113) order determination section a122, the total number of receiving antennas _{J n} of the selected terminal device information in step S111 beauty step S112 is equal to or less than the number of transmission antennas K. When the total number of reception antennas is equal to or less than the number K of transmission antennas (YES), the process proceeds to step S114. On the other hand, when the total number of reception antennas is larger than the number K of transmission antennas (NO), the process returns to step S109.
(Step S114) The order determination unit a122 deletes the signal generation order c assigned to the terminal device information selected last (terminal device information selected in either step S111 or step S112), thereby this terminal device information. Cancel assignment to. Thereafter, the process proceeds to step S115.
(Step S115) The order determination unit a122 counts the number of terminal device information to which the signal generation order c is assigned. The order determination unit a122 substitutes the count result for C. As a result, the order determination unit a122 determines C, and the value of the signal generation order c is assigned to the terminal device information. That is, the order determination unit a122 determines the signal generation order c for the terminal device Bn indicated by the identification information of the terminal device information. Thereafter, the operation is terminated.

The order determination processing order determining unit a122 performs is not limited to the operation of FIG. 3, at least one of the number of streams t _n is large reception apparatus Bn addressed signal, the stream number t _n is less receiving apparatus Bn addressed Any process that determines the order in advance of the signal may be used.

The order determination process in FIG. 3 is as follows, for example.
In the communication system of FIG. 1, when the number of streams of the terminal devices B1 and B3 is t _{1 and} t ₃ = 2 and the number of streams of the terminal device B2 is t ₂ = 1, the order determination unit a122 Thus, the terminal apparatuses Bn to be spatially multiplexed and the signal generation order c of those terminal apparatuses Bn are determined. However, it is assumed that the reception quality of the terminal device B1 is higher than the reception quality of the terminal device B3.
In FIG. 3, in step S101, the order determination unit a122 rearranges the terminal device information in the order of the terminal devices B1, B3, and B2 or the order of the terminal devices B3, B1, and B2. In step S103, the order determination unit a122 extracts the terminal device information of the terminal devices B1 and B3. Thereafter, the order of these terminal device information is not determined, and the order determination unit a122 extracts the terminal device information of the terminal devices B1 and B3 in step S106. In step S107, the order determination unit a122 rearranges the terminal device information in the order of the terminal devices B3 and B1. That is, the order determination unit a122 rearranges the terminal device information in the order of the terminal devices B3, B1, and B2.

In step S111, the order determination unit a122 assigns c = C to the terminal device information of the terminal device B2. In step S113, the order determination unit a122 determines that the total number J ₂ (= 1) of reception antennas is equal to or less than the number of transmission antennas K (= 4). In step S112, the order determination unit a122 assigns c = 1 to the terminal device information of the terminal device B3. The order determination unit a122 determines in step S113 that the total number of reception antennas J ₂ + J ₃ (= 3) is less than or equal to the number of transmission antennas K (= 4). In step S111, the order determination unit a122 assigns c = C-1 to the terminal device information of the terminal device B1. In step S113, the order determination unit a122 determines that the total number of reception antennas J ₂ + J ₃ + J ₁ (= 5) is greater than the number of transmission antennas K (= 4). In step S114, the order determining unit a122 cancels the latest assignment (assignment in the latest step S111). That is, the signal generation order c is assigned to the terminal device information of the terminal devices B3 and B2. The order determination unit a122 sets C = 2 as a result of counting in step S115. Therefore, the order determination unit a122 determines the signal generation order “1” and “2” for the terminal device information of the terminal devices B3 and B2, respectively.

In this case, order conversion section a124 has the information _D 1, _{D 2} destined 1, the second receive antenna of the terminal apparatus B3 which is a signal generated sequence c = 1, respectively, the encoding unit a131-1, a131-2 Will be output. The order conversion unit a124 becomes possible to duplicate the information D ₃ addressed first receive antenna of the terminal apparatus B2 is the signal generating sequence c = 2. Order conversion section a124 has the duplicated information as the information _{D 4,} the information _D 3, _{D 4,} respectively, encoding section A131-3, so that the output to A131-4. That is, a signal addressed to the terminal device Bn having a large number of copies and transmitted is output to the encoding unit a131-i having a smaller i than that of the terminal device Bn having a small number of multiplexing.

<Processing in Multiplex Signal Generation Unit a14>
In the communication system of FIG. 1 (K = 4, N = 3, J ₁ , J ₂ , J ₃ = 2), the processing in the multiplexed signal generation unit a14 is as follows according to the configuration of FIG.
The filter calculation unit a141 generates a propagation matrix H of the following equation (1).

Here, the elements H _ik in the first and second rows of the propagation matrix H are propagation path estimation values of the terminal apparatus Bn having the first smallest stream number t _n . Elements H _ik in the third and fourth rows of the propagation matrix H are propagation path estimation values of the terminal device Bn having the first largest stream number t _n .
Filter calculating section a141 extracts a propagation matrix H for each terminal device n (referred propagation matrix _{H n).} Specifically, the filter calculation unit a141 extracts the following expressions (2) and (3).

Filter calculating section a141, as in the equation (4), singular value decomposition propagation matrix _{H 1.}

Here, the matrix V ₁ is a 4 × 4 unitary matrix, and here, the matrix U ₁ is defined as U ₁ ′. Filter calculating section a141 has a 4 2 matrix matrix _{V 1} was a left half of the matrix _{V 1} (1, 2 columns), a left half (3,4 columns) 4 2 matrix, respectively Extract as matrix V _1,1 and matrix V _1,2 . The filter calculation unit a141 calculates a matrix V ₂ ′ by performing singular value decomposition on a matrix obtained by multiplying the matrices V ₁ and ₂ by the matrix H ₂ . Specifically, filter calculating section a141 has the formula (5) to calculate the _{V 2} satisfying (6).

  The filter calculation unit a141 calculates the matrix M by the following equation (7).

The filter multiplier a145 multiplies the signal by using the matrix M in Expression (7) as a filter coefficient.
Multiply the matrix M in equation (7) by the propagation path matrix H. In the base station apparatus a1, a signal transmitted by performing precoding of the expression (7) on the transmission signal and received via the propagation path is converted from the propagation path matrix H to the matrix M of the expression (7) on the terminal apparatus side. It is the same as that through the propagation path equivalent to the multiplied propagation path. This equivalent propagation path is expressed by the following equation (8).

  Expression (8) represents an equivalent propagation path including the filter coefficient between the base station apparatus a1 and the terminal apparatus b1. Equation (8) indicates that the block is triangulated. In the present embodiment, the case where Expression (8) is used as the filter coefficient has been described. However, the present invention is not limited to this, and the filter coefficient calculated by the filter calculation unit a145 is multiplied by the propagation path matrix H. In addition, any filter coefficients that block triangulate the matrix after multiplication may be used.

Off-diagonal elements of the formula (8) indicates that the signal addressed to the stream number t _n is greater terminal Bn is receive the stream number t _n is a small terminal Bn, an interference signal. The interference calculation unit a142 calculates this interference signal. Specifically, the interference calculation unit a142 calculates the interference signals f ₃ and f ₄ using the following equation (9).

  In this case, the relationship of the following formula (10) is satisfied.

In equation (10), the eigenvalues of matrices (elements A ₁₁ , A ₁₂ , A ₂₁ , A ₂₂ ) multiplied by the signals s ₁ , s ₂ addressed to the terminal device Bn having a large number of streams t _n are represented by d ₁ , d ₂ and the eigenvalues of matrices (elements A ₃₃ , A ₃₄ , A ₄₃ , A ₄₄ ) multiplied by the signals s ₃ , s ₄ addressed to the terminal device Bn with a small number of streams t _n are d ₃ , d _4. , D ₁ > d ₃ > d ₂ > d ₄ . Therefore, if the transmission signals s ₁ , s ₂ and s ₃ , s ₄ have the same amplitude, the amplitude of the reception signal s ₁ becomes larger than the amplitude of the reception signal s ₃ , and the amplitude of the reception signal s ₂ is received. greater than the amplitude of the signal _{s 4.}

Subtraction unit a143-3~a143-4 respectively, the interference calculation section a142 subtracts the interference signal _f 3, _{f 4} calculated from the signal _s 3, _{s 4.} As a result, as shown on the right side of Expression (10), a signal obtained by multiplying the transmission signal vector s _i by a block diagonalized matrix is received. That is, spatial multiplexing can be realized so that signals addressed to a plurality of terminal devices do not interfere with each other.

  The modulo operation unit a144-i performs a modulo operation represented by the following equation (11).

Here, Re [u] and Im [u] represent the real part and the imaginary part of the complex number u, respectively. The floor function calculation represents the smallest integer greater than or equal to w. j is an imaginary unit where j ² = −1. The second item and the third item of Equation (4) indicate that the real part and imaginary part of u are integer multiples of τ. Incidentally, tau is a constant determined by the modulation scheme of modulation applied to the signal s _m. For example, τ = 2√2 for QPSK (quadrature phase-shift keying), τ = 8 / √10 for 16 QAM (quadrature amplitude modulation), and τ = 16 / √42 for 64QAM. It is.
By performing the modulo operation, the base station apparatus a1 can limit the amplitude of the transmission signal so that the amplitude of the signal after interference subtraction falls within a predetermined width, and can suppress an increase in transmission power.

<About the terminal device b1>
FIG. 4 is a schematic block diagram illustrating the configuration of the terminal device b1 according to the present embodiment. In this figure, the terminal device b1 includes receiving antennas b111-1 (Bn1), b111-2 (Bn2), radio units b112-1, b112-2, signal separating units b113-1, b113-2, and a control signal processing unit. b114-1, b114-2, propagation path estimator b115, coefficient estimator b116, MIMO demultiplexer b117, residue determiners b118-1, b118-2, modulo calculators b119-1, b119-2, demodulator b120 -1, b120-2, decoding sections b121-1, b121-2, higher layer section b122, radio section b123, and transmission antenna b124.

The radio unit b112-j (j = 1, 2) receives a signal via the receiving antenna b111-j (a signal received by the terminal device Bm is a received signal y _m ). This signal includes a pilot signal, an information signal addressed to the terminal device Bm, and a control information signal. The radio unit b112-j downconverts the received signal to generate a baseband signal, and performs A / D (Analog to Digital) conversion. The radio unit b112-j outputs the converted signal to the signal separation unit b113-j.

The signal separation unit b113-j separates the signal input from the wireless unit b112-j. Of the separated signals, the signal separation unit b113-j outputs a control information signal to the control information reception unit b113-j, and outputs a pilot signal to the propagation path estimation unit b115. The signal demultiplexing unit b113-j outputs the information signal addressed to the own apparatus among the demultiplexed signals to the MIMO demultiplexing unit b117.
The control signal processor b114-j demodulates and decodes the control information signal input from the signal separator b113-j. The control signal processing unit b114-j outputs the remainder calculation information and the modulation scheme among the decoded control information to the residue determination unit b118-j and the modulo calculation unit b119-j, respectively. Control signal processing section b114-j outputs coding rate and modulation scheme information among the decoded control information to demodulation section b120-j and decoding section b121-j, respectively (not shown).

  The propagation path estimation unit b115 estimates the propagation path estimation value for each antenna based on the pilot signal generated by the second reference signal generation unit a151 among the pilot signals input from the signal separation unit b113-j. Moreover, the propagation path estimation part b115 measures reception quality using this pilot signal. Note that this measurement may be performed using a pilot signal transmitted in a frame different from the data signal. The propagation path estimation unit b115 outputs the propagation path information indicating the estimated propagation path estimation value and the reception quality information indicating the measured reception quality to the upper layer part b122.

  The propagation path estimation unit b115 is based on the pilot signal generated by the first reference signal generation unit a152 out of the pilot signals input from the signal separation unit b113-j, and the equivalent propagation path through which the signal addressed to its own device passes. The propagation path estimated value of the propagation path including the filter coefficient multiplied by the base station apparatus a1 is estimated. The propagation path estimation unit b115 outputs equivalent propagation path estimation information indicating the estimated propagation path value of the equivalent propagation path to the coefficient estimation unit b116.

The coefficient estimation unit b116 calculates the filter coefficient of Expression (7) based on the equivalent channel estimation information input from the channel estimation unit b115, and outputs the filter coefficient to the MIMO demultiplexing unit b117.
MIMO demultiplexing section b117 based on the channel information input from the channel estimation unit B115, generates a propagation matrix _{H n.} MIMO demultiplexing section b117 based on the generated filter coefficient input from the propagation matrix _{H n} and a coefficient estimation section b116 has, to extract a signal.
Specifically, the MIMO demultiplexing unit b117 calculates the matrix U ₁ ′ in Expression (4) or the matrix U ₂ ′ in Expression (6). The base station apparatus b3 transmits in advance information indicating whether each terminal apparatus is the terminal apparatus B1 or B2 to each terminal apparatus, and the MIMO demultiplexing unit b117 is based on this information. The matrix U ₁ or U ₂ ′ may be calculated.
The MIMO demultiplexing unit b117 multiplies the signal input from the signal demultiplexing units b113-1 and b113-2 by the calculated matrix U _{n, n} , matrix U ₁ ′, or matrix U ₂ ′. For example, since a matrix obtained by multiplying the product HM of the matrix of Equation (8) by U ₂ ′ becomes D ₂ ′ (diagonal matrix), the MIMO demultiplexing unit b117 divides D ₂ ′ to obtain a signal. Extract. As described above, the MIMO demultiplexing unit b117 extracts the signal of each stream. The MIMO demultiplexing unit b117 outputs the extracted signal to the residue determination units b118-1 and b118-2 for each of the reception antennas b111-1 and b111-2.

When the residue calculation information is input from the control signal processing unit b114-j, the residue determination unit b118-j outputs the signal input from the propagation path compensation unit b117 to the modulo operation unit b119-j. On the other hand, when the residue calculation information is not input from the control signal processing unit b114-j, the residue determination unit b118-j outputs the signal input from the propagation path compensation unit b117-j to the demodulation unit b120-j. This configuration remainder judgment unit B118-j of the stream number _{t n} is greater terminal Bn outputs the input signal to the demodulation unit b 120-j, remainder judgment unit of the stream number _{t n} is less terminal Bn B118- j outputs the input signal to the modulo arithmetic unit b119-j.
In the present embodiment, the case has been described where the remainder calculation information is information indicating that the modulo calculation has been performed. However, the present invention is not limited to this, and the remainder calculation information may be information indicating that the modulo calculation is not performed. In this case, the remainder determination unit b118-j outputs a signal to the modulo operation unit b119-j when the residue operation information is not input, and outputs the signal to the demodulation unit b120-j when the residue operation information is input. output to j.

  The modulo operation unit b119-j performs the same modulo operation as that of the base station device a1 (modulo operation represented by the equation (11)). Here, the modulo calculation unit b119-j selects τ corresponding to the modulation scheme indicated by the information input from the control signal processing unit b114-j, and performs the modulo calculation using the τ. The modulo calculation unit b119-j outputs the calculated signal to the demodulation unit b120-j.

The demodulation unit b120-j demodulates the signal input from the remainder determination unit b118-j or the modulo calculation unit b119-j using the modulation scheme indicated by the information input from the control signal processing unit b114-j. The demodulator b120-j outputs information obtained by demodulating the signal to the decoder b121-j.
The decoding unit b121-j decodes the information input from the demodulation unit b120-j based on the coding rate indicated by the information input from the control signal processing unit b114-j. The demodulation unit b120-j outputs the decoded information to the upper layer unit b122.

The upper layer part b122 outputs the information input from the decoding part b121-j to an output part (not shown), or controls the terminal device b1 based on the input information. The upper layer unit b122 outputs the reception quality information and the channel information input from the channel estimation unit b115 to the radio unit b123 as a signal addressed to the base station apparatus a1.
The radio unit b123 modulates the information input from the upper layer unit b122, and D / A converts the modulated signal. The radio unit b123 up-converts the converted signal to a radio frequency and transmits it to the base station apparatus a1 via the transmission antenna b124.

Thus, in the present embodiment, the base station apparatus a1 has at least one of the number of streams t _n is large reception apparatus Bn destined signal, than the signal addressed to the stream number t _n is less receiving apparatus Bn, previous Decide on order. The base station apparatus a1 transmits the precoded signal according to the determined signal generation order c. The terminal device Bn receives the signal transmitted by the base station device a1. Thus, in the present embodiment, the base station apparatus a1 has the stream number t _n is large reception apparatus Bn destined signal, as compared to the signal addressed to the stream number t _n is less receiving apparatus Bn, a large value it can multiply, it is possible to increase the reception quality of the stream number t _n is large reception apparatus Bn destined signal. Thus, the stream number t _n number, to prevent the error increases with the signal information is often receiving apparatus destined Bn to transmit, it is possible to improve the transmission efficiency.

In the present embodiment, the case where the MIMO demultiplexing unit b117 calculates the matrix U ₁ ′ or the matrix U ₂ ′ has been described, but the present invention is not limited to this. For example, the base station apparatus a2 may calculate these matrices and transmit the calculated matrix information to the terminal apparatus b2. In this case, the MIMO demultiplexing unit b117 of the terminal device b2 extracts a signal using the received matrix information. Further, the MIMO demultiplexing unit b117 may extract a signal by other processing. For example, two received signals in other terminal devices may be separated by MMSE (Minimum Mean Square Error) or MLD (Maximum Likelihood Detection).

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.
In the present embodiment, a case will be described in which, when there are terminal devices having the same number of streams t _n , the base station device switches the signal generation order c assigned to these terminal devices according to time.

FIG. 5 is a schematic diagram illustrating an example of a communication system according to the second embodiment of the present invention. In this figure, the communication system includes a base station device a2 and a plurality of terminal devices B1 to BN (N = 5 in FIG. 5). The base station apparatus a2 includes K transmission antennas a161 to a16K (K = 6 in FIG. 5).
The terminal apparatus Bn includes J _n reception antennas Bn1 to BnJ _n (J _{1 to} J ₅ = 2 in FIG. 4), and receives a signal transmitted from the base station apparatus a1.

FIG. 6 is a schematic block diagram showing the configuration of the base station apparatus a2 according to this embodiment. When the base station apparatus a2 (FIG. 6) according to the present embodiment is compared with the base station apparatus a1 (FIG. 2) according to the first embodiment, the order determination unit a222 and the multiplexed signal generation unit a24 are different. However, the functions of other components are the same as those in the first embodiment. A description of the same functions as those in the first embodiment is omitted.
In the base station apparatus a2, since the number of transmission antennas is K = 6, the encoding units a131-5 and a131-6, the modulation units a132-5 and a132-6, and the radio unit a155- 5, a155-6, and transmission antennas a165 and a165 are different from the first embodiment. Since these configurations have been described in the first embodiment as the encoding unit a131-i, the modulation unit a132-i, the radio unit a155-i, and the transmission antenna a16k, description thereof will be omitted.

Order determining unit a222, to the stream number t _n is the same terminal device information, assigned to the signal generating sequence c varies, assigns a signal generation sequence c. Specifically, the order determination unit a222, for stream number t _n is the same terminal device information for each predetermined time, so that the signal generating sequence c is cyclically allocates the signal generation sequence c (FIG. 8, FIG. 9).

  FIG. 7 is a schematic block diagram illustrating a configuration of the multiple signal generation unit a24 according to the present embodiment. When the multiplexed signal generator a24 (FIG. 7) according to the present embodiment is compared with the multiplexed signal generator a14 (FIG. 2) of the base station apparatus a1 according to the first embodiment, the subtractors a143-5 and a143-6. The modulo arithmetic units a144-5 and a144-6 are different. Since these configurations have the same functions as the subtraction unit a143-i and the modulo calculation unit a144-i in the first embodiment, description thereof will be omitted.

FIG. 8 is a schematic diagram illustrating an example of assignment of the signal generation order c according to the present embodiment. This figure is for the case where the terminal devices B2 and B3 have the same number of streams t ₂ and t ₃ . The order determination unit a222 alternately replaces the signal generation orders 2 and 3 assigned to the terminal device information of the terminal devices B2 and B3 having the same number of streams t _n in a predetermined time unit (for example, a symbol unit).
As shown in FIG. 8, at time 1, signal generation orders 2 and 3 are assigned to the terminal device information of the terminal devices B2 and B3, respectively. At time 2, signal generation orders 3 and 2 are assigned to the terminal device information of the terminal devices B2 and B3, respectively. At time 3, signal generation orders 2 and 3 are assigned to the terminal device information of the terminal devices B2 and B3, respectively. Note that the order determination unit a222 performs the same assignment as that at times 1 and 2 at times 2d + 1 and 2d + 2 (d is a natural number) thereafter.

FIG. 9 is a schematic diagram illustrating another example of assignment of the signal generation order c according to the present embodiment. This figure is for the case where the number of streams t ₃ , t ₄ , and t ₅ of the terminal devices B 3, B 4, and B ₅ are the same. Order determining unit a222 interchanges the signal generating sequence 2, 3, 4 stream number _{t n} is allocated to the terminal device information of the same terminal apparatus B3, B4, and B5, alternately at predetermined time units. In the example of FIG. 9, the order determination unit a222 cycles through the signal generation orders 2, 3, and 4, but the present invention is not limited to the circulation. Further, even in the case of circulation, the order of circulation is not limited to the order of the terminal devices B3, B4, and B5. For example, the signal generation orders 2, 3, and 4 are circulated and assigned in the order of the terminal devices B4, B3, and B5. May be.
As shown in FIG. 9, at time 1, signal generation orders 2, 3, and 4 are assigned to the terminal device information of the terminal devices B3, B4, and B5, respectively. At time 2, signal generation orders 3, 4, and 2 are assigned to the terminal device information of the terminal devices B3, B4, and B5, respectively. At time 3, signal generation orders 4, 3, and 2 are assigned to the terminal device information of the terminal devices B3, B4, and B5, respectively. Note that the order determination unit a222 performs the same assignment as the times 1, 2, and 3 at the subsequent times 3d + 1, 3d + 2, and 3d + 3 (d is a natural number).

Thus, in the present embodiment, the base station apparatus a2, to the stream number t _n is the same terminal device information, assigned to the signal generating sequence c varies, assigns a signal generation sequence c. Thus, in the present embodiment, among the number of streams t _n is the same terminal device Bn, unlike the values to be multiplied is always able to prevent the differences in the receiving quality is increased.

  In the present embodiment, an example is shown in which the time unit for changing the signal generation order c is a symbol unit. However, the present invention is not limited to this, and it may be a time unit longer or shorter than a symbol unit, and may be a frame unit, for example. Further, the signal generation order c may be switched for each predetermined frequency. For example, the signal generation order c may be switched in units of subcarriers or subcarrier groups.

(Third embodiment)
Hereinafter, the third embodiment of the present invention will be described in detail with reference to the drawings.
In the present embodiment, a case where QR-THP (QR-Tomlinson-Harashima Precoding) is used as precoding will be described.
In each of the above embodiments, the equivalent propagation path obtained by precoding is a propagation path matrix that is block-diagonalized for each user. In the precoding according to the present embodiment, a propagation path matrix that is diagonalized for each stream is obtained by using QR decomposition. As a result, the received signal at each receiving antenna of the terminal apparatus becomes only one desired signal component, and it is not necessary to perform the MIMO demultiplexing process in each terminal apparatus as in the above embodiments.
Note that a schematic diagram illustrating an example of a communication system according to the present embodiment is the same as that of the first embodiment (FIG. 1), and a description thereof will be omitted. Hereinafter, the base station apparatus according to the present embodiment is referred to as a base station apparatus a3, and the terminal apparatus is referred to as a terminal apparatus b3.

FIG. 10 is a schematic block diagram showing the configuration of the base station apparatus a3 according to the third embodiment of the present invention. When the base station apparatus a3 (FIG. 10) according to the present embodiment is compared with the base station apparatus a1 (FIG. 2) according to the first embodiment, the order conversion unit a324, the filter calculation unit a341, and the interference calculation unit a342. Is different. However, the functions of other components are the same as those in the first embodiment. A description of the same functions as those in the first embodiment is omitted.
The base station device a3 is different in that the base station device a3 includes a subtraction unit a143-2 and a modulo calculation unit a144-2. Since these configurations have the same functions as the subtraction unit a143-i and the modulo calculation unit a144-i in the first embodiment, description thereof will be omitted.

The order conversion unit a324 selects information addressed to the terminal device Bn whose identification information matches the identification information input from the order determination unit a122. The order conversion unit a324 rearranges the information addressed to the selected terminal device Bn based on the signal generation order c input from the order determination unit a122. The order conversion unit a324 outputs the information D _i to the encoding unit a131-i. Here, the order conversion unit a324 does not output the information D _{i + 1 to} D _Jn when the number of streams t _n of the terminal device Bn is smaller than the number of reception antennas J _n . However, the present invention is not limited to this, and the order conversion unit a324 may duplicate the information D _i as information D _{i + 1 to} D _{Jn in the same} manner as the order conversion unit a124.

The filter calculation unit a341 generates a propagation matrix H from the propagation path information input from the wireless unit a112. Here, the filter calculation unit a341 arranges the elements H _ik in the order of i based on the identification information of the terminal device Bn input from the order determination unit a122 and the signal generation order information.
Filter calculating section a341 is a complex conjugate transpose of the generated propagation matrix H (the Hermitian conjugate) matrix H ^H to QR decomposition to calculate the matrix R and matrix Q. QR decomposition is to decompose a matrix into a unitary matrix Q and an upper triangular matrix R. The filter calculation unit a341 outputs information indicating the calculated matrix R to the interference calculation unit a342.

The interference calculation unit a342 uses the matrix R indicated by the information input from the filter calculation unit a341, and the interference signal f from another signal s _e (e ≠ i) with respect to the signal s _i input from the order conversion unit a124. _i is generated sequentially. Specifically, the interference calculation unit a342 uses the matrix R to calculate the interference coefficient matrix C = {diag (R ^H )} ⁻¹ R ^H −I.
Interference calculation section a342 has a signal _{s 1} is input from the sequence conversion unit A 124, and Modulo arithmetic unit a143-2~a143- the (i-1) signal _{s 2} is input from the _{'~s i-1'} component The vector s _i ′ to be generated is sequentially generated. The interference calculation unit a342 generates the interference signal f _i by multiplying the interference coefficient matrix C by the vector s _i ′.
Interference calculation section a342 the generated interference signal _{f i,} respectively, and outputs to the subtraction section a143-i.

<Processing in Multiplex Signal Generation Unit a34>
With the above configuration, the processing in the multiplexed signal generation unit a34 is as follows.
The filter calculation unit a341 generates the propagation matrix H of the above equation (1).
The filter calculation unit a341 calculates a filter coefficient Q for triangulating the propagation path matrix H. Specifically, filter calculating section a341, as shown in the following equation (12), the complex conjugate transpose matrix H ^H of the propagation matrix H to QR decomposition to calculate the matrix R and the filter coefficient (matrix Q).

As described above, the filter calculation unit a341 calculates the interference coefficient matrix C = {diag (R ^H )} ⁻¹ R ^H −I using this matrix R. Signal _s i -f _i after subtraction of the subtraction unit a143-i outputs is expressed by the following equation (13).

  The modulo operation unit a144-i performs a modulo operation represented by the following equation (14).

Here, Re [u] and Im [u] represent the real part and the imaginary part of the complex number u, respectively. The floor function calculation represents the smallest integer greater than or equal to w. j is an imaginary unit where j ² = −1. The second item and the third item of Equation (14) indicate that the real part and imaginary part of u are integer multiples of τ. Incidentally, tau is a constant determined by the modulation scheme of modulation applied to the signal s _m. For example, τ = 2√2 for QPSK (Quadrature Phase-Shift Keying), τ = 8 / √10 for 16QAM (Quadrature Amplitude Modulation), and τ = 16 / √42 for 64QAM. It is.
The base station apparatus a3 can perform the modulo operation to limit the amplitude of the transmission signal so that the amplitude of the signal after interference subtraction is within a predetermined width, and can suppress an increase in transmission power.
As for the signal output from the modulo arithmetic unit a145-i, for example, the signal s ₂ 'is expressed by the following equation (15).

  When the propagation path matrix H is multiplied by the filter coefficient, the following equation (16) is obtained.

  Expression (16) represents an equivalent propagation path including the filter coefficient between the base station apparatus a3 and the terminal apparatus b3. Note that the filter coefficient calculation processing of the filter calculation unit a341 may not be QR decomposition. That is, the filter calculation unit a341 may calculate a matrix that becomes a triangular matrix when multiplied by the propagation path matrix H as a filter coefficient.

A received signal vector y = (y ₁ , y ₂ , y ₃ , y ₄ ) whose component is a received signal y _i addressed to the j-th receiving antenna of each terminal device Bn is expressed by the following equation (7).

Here, R ₄₄ <R ₃₃ <R ₂₂ <R _{11 because} of the nature of QR decomposition. As described above, the order conversion section a124 has rearranged signal S _n in the order of the stream numbers t _n is large terminal Bn. Thus, the base station apparatus a2 is often stream number t _n, the amplitude of signal s _n of a large amount of information terminal devices destined Bn to transmit per unit time is increased, less number of streams t _n, per unit time in it is possible to reduce the amplitude of the signal s _n of less information terminal device destined Bn to transmit. Therefore, the base station apparatus a1 can reduce the error rate of the stream number t _n is large terminals a3, it is possible to improve the transmission efficiency. In other words, although the number of streams t _n is less terminals a3 in error rate may be higher, reducing the influence on the lowering of the transmission efficiency of the entire communication system that, even if, because a small number of streams t _n it can.

  FIG. 11 is a schematic block diagram illustrating the configuration of the terminal device b3 according to the present embodiment. When the terminal device b3 (FIG. 11) according to the present embodiment is compared with the terminal device b1 (FIG. 4) according to the first embodiment, the propagation path compensation unit b317 is different. The terminal device b3 is different in that the terminal device b3 does not include the coefficient estimation unit b116 of the terminal device b1.

  The propagation path compensation unit b317 performs propagation path compensation by dividing the signal according to the propagation path estimation value indicated by the propagation path information input from the propagation path estimation unit b115. The propagation path compensation unit b116 outputs the signal received by the reception antenna b111-j among the propagation path compensated signals to the remainder determination unit b118-j.

Thus, in the present embodiment, the base station apparatus and a3, at least one of the number of streams t _n is large reception apparatus Bn destined signal, than the signal addressed to the stream number t _n is less receiving apparatus Bn, previous Decide on order. The base station apparatus a3 transmits the precoded signal according to the determined signal generation order c. The terminal device Bn receives the signal transmitted by the base station device a3. Thus, in the present embodiment, the base station apparatus a3, to the stream number t _n is large reception apparatus Bn destined signal, as compared to the signal addressed to the stream number t _n is less receiving apparatus Bn, a large value it can multiply, it is possible to increase the reception quality of the stream number t _n is large reception apparatus Bn destined signal. Thus, the stream number t _n number, to prevent the error increases with the signal information is often receiving apparatus destined Bn to transmit, it is possible to improve the transmission efficiency.

In the third embodiment, the order determination unit a122 may fix the first or last signal generation order c, and replace the other signal generation order c for each reception antenna or terminal device. For example, the order determination unit a122 may determine a pattern as follows and change the pattern at predetermined time intervals.
FIG. 12 is a schematic diagram illustrating an example of assignment of the signal generation order c according to the present embodiment. This figure is a diagram showing two patterns in which the head of the signal generation order c (signal generation order “1”) is fixed and the other signal generation order c is replaced for each reception antenna.
As shown in FIG. 12, in the “pattern 1”, the signal generation order 1, 2, 3 in the order of the reception antenna B11 of the terminal device B1, the reception antenna B12 of the terminal device B1, and the reception antenna B11 of the terminal device B2, respectively. Is assigned.
In “pattern 2”, signal generation orders 1, 2, and 3 are assigned in the order of the reception antenna B11 of the terminal device B1, the reception antenna B11 of the terminal device B2, and the reception antenna B12 of the terminal device B1, respectively.

In each of the above embodiments, the order determination unit a122 assigns the signal generation order c to the terminal apparatus information whose rearranged order is the yth largest, and then assigns the signal generation order c to the yth smallest terminal apparatus information. The case of repeating was explained. However, the present invention is not limited to this, and the order determination unit a122 repeatedly assigns the signal generation order c to the yth smallest terminal apparatus information and then assigns the signal generation order c to the yth largest terminal apparatus information. May be. Moreover, the order determination part a122 does not need to allocate alternately.
In this way, the order determination unit a122 may determine at least one of the signals addressed to the terminal device Bn having a large number of streams in the order earlier than the signal addressed to the terminal device Bn having a smaller number of streams. .

In the above embodiment, when there are a plurality of terminal apparatuses Bn having the same number of streams t _n , the order determining unit a122 determines the signal generation order c assigned to these terminal apparatuses Bn as follows: Also good.
The order determination unit a122 selects the order in which the transmission speed of the terminal device Bn is small and the order in which the data amount is large. The signal generation order c may be determined in the order of the small amount of data, the coding rate, the order of the small number of modulation levels, and the order of the number of retransmissions.

Note that some of the base station devices a1 and a2 and the terminal devices b1 and b2 in the above-described embodiment, for example, the reception quality acquisition unit a123, the precoding determination units 123 and a223, the order conversion unit a141, and the filter calculation units a141 and a24. -12, a24-22, interference calculation unit a142, subtraction units a143-2 to a143-N, modulo calculation units a144-2 to a144-N, filter multiplication units a145 and a246, and precoding selection unit a240 are realized by a computer. You may make it do. In that case, the program for realizing the control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. Here, the “computer system” is a computer system built in the base station devices a1 and a2 or the terminal devices b1 and b2, and includes hardware such as an OS and peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” is a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, In such a case, a volatile memory inside a computer system serving as a server or a client may be included and a program that holds a program for a certain period of time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.
Moreover, you may implement | achieve part or all of base station apparatus a1, a2 and terminal device b1, b2 in embodiment mentioned above as integrated circuits, such as LSI (Large Scale Integration). Each functional block of the base station devices a1 and a2 and the terminal devices b1 and b2 may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, in the case where an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology may be used.

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

  a1, a2, a3 ... base station equipment, B1-5, b1, b3 ... terminal equipment, a111 ... receiving antenna, a112 ... radio part, a12, a22, a32 ... upper layer part , A131-1 to a131-N ... encoding unit, a132-1 to a132 -N ... modulation unit, a14, a24, a34 ... multiplexed signal generation unit, a151 ... second reference signal Generation unit, a152 ... first reference signal generation unit, a153 ... filter multiplication unit, a154 ... signal multiplexing unit, a155-1 to a155-K ... radio unit, a161 to a16K ... Transmission antenna, a121: stream number acquisition unit, a122, a222 ... order determination unit, a123 ... application unit, a124, a324 ... order conversion unit, a141 ... filter calculation unit, a14 ... Interference calculation unit, a143-2 to a143-N ... Subtraction unit, a1442-2 to a144-N ... Modulo operation unit, a145 ... Filter multiplication unit, B11-B51, b111-1, b111-2: reception antenna, b112-1, b112-2 ... radio unit, b113-1, b113-2 ... signal separation unit, b114-1, b114-2 ... control signal processing unit , B115 ... propagation path estimation section, b116 ... coefficient estimation section, b117 ... MIMO demultiplexing section, b317 ... propagation path compensation section, b118-1, b118-2 ... residue determination section, b119-1, b119-2 ... modulo operation unit, b120-1, b120-2 ... demodulation unit, b121-1, b121-2 ... decoding unit, b122 ... higher layer unit, b123.・ ・Line section, b124 ··· transmitting antenna

Claims (8)

In a communication system comprising a plurality of receiving devices and a transmitting device that spatially multiplexes and transmits signals addressed to the plurality of receiving devices.
The transmission apparatus determines a sequence for the spatial multiplexing based on information on the number of signal sequences of signals addressed to each reception apparatus.   The communication system according to claim 1, wherein the transmission apparatus uses precoding based on a nonlinear operation for the spatial multiplexing.   The transmitting device receives at least one signal addressed to a receiving device having a large number of signal sequences indicated by information on the number of signal sequences of the signal, before a signal addressed to a receiving device having a small number of signal sequences. The communication system according to claim 1, wherein the communication system is determined in order.   The communication system according to claim 1, wherein the information related to the number of signal sequences of the signal is information indicating the number of signal sequences of the signal notified to the transmitting device by the receiving device. In a transmission device that spatially multiplexes and transmits signals addressed to a plurality of reception devices,
A transmission apparatus characterized by determining an order related to the spatial multiplexing based on information relating to the number of signal sequences of signals addressed to each reception apparatus. In a transmission control method in a transmission device for spatially multiplexing and transmitting signals addressed to a plurality of reception devices,
A transmission control method comprising a step in which a transmission device determines an order related to the spatial multiplexing based on information on the number of signal sequences of signals addressed to each reception device. To a computer of a transmission device that spatially multiplexes and transmits signals addressed to a plurality of reception devices,
A transmission control program for executing means for determining an order for the spatial multiplexing based on information on the number of signal sequences of signals addressed to each receiving apparatus. A processor for determining an order for the spatial multiplexing based on information on the number of signal sequences of signals addressed to each receiving apparatus.

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