JP4810578B2 - Wireless communication method and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication method and a wireless communication system that perform signal transmission using a plurality of antennas for transmission and reception.

  In recent years, wireless communication has been remarkably popular due to its convenience. For this reason, countermeasures against tight usage frequency are urgently needed. In recent years, research on a MIMO (Multi-Input Multi-Output) system that performs high-speed signal transmission using a plurality of antennas in a transmitter / receiver has been actively conducted as one technique for effectively using this frequency. In the MIMO system, it is known that by using a plurality of antennas in the transceiver, a higher capacity can be achieved than in the case where the transceiver has one antenna.

  In the MIMO system, many researches have been made on SDM (Space Division Multiplexing) transmission in which signals are individually transmitted from a plurality of transmission antennas and each signal is extracted using signal processing on the reception side. Therefore, in the following, representative documents of SDM transmission AVZelst, RVNee, and GAAwater, kako “Space Division Multiplexing (SDM) for OFDM Systems” IEEE Proc. Of VTC2000 SPring, pp. 1070-1074, 2000 or Kurosaki, Asai, Sugiyama, Umehira, “Proposal of SDM-COFDM for broadband mobile communication realizing 100 Mbit / s with MIMO channel”, IEICE Technical Report RC2001-135, oct.2001, will explain the prior art.

FIG. 32 shows the configuration of a transceiver that performs SDM transmission. In SDM transmission, a time-series signal is individually transmitted from each antenna of a transmitter, and the receiver receives a signal using beam forming corresponding to each transmitted signal. This signal processing configuration will be described below. The description will proceed with N transmission antennas, M reception antennas, a propagation coefficient from transmission antenna n to reception antenna m as h _mn , and a propagation characteristic between transmission and reception stations as a matrix H = [h _mn ].

As shown in FIG. 32, a terminal A1 of the transmitter transmits time-series transmission signals s _n (p) (p = 1,..., N) from N transmission antennas 3. The transmission signal passes through the propagation path 5 and is received by the M reception antennas 4. In the terminal B2 of the receiver, with respect to the received signal, it performs signal combining by multiplying the weight v _m at the antenna 4.

In the following, this series of processes is expressed using mathematical expressions. If the received signal at the receiving antenna 4 is x _m (p), the received vector x (p) = [x ₁ (p),..., X _M (p)] ^T ( ^T transpose) is given by .
_{x (p) = Σ n =} 1 N h n s n (p) + z (p)
Here, s ₁ (p),..., S _N (p) are transmission signals, and h _n , = [h _1n ,..., H _Mn ] ^T are transmitted from the transmission antenna 3 to the M reception antennas 4. , Z (p), = [z ₁ (p),..., Z _N (p)] ^T is a noise vector, and z _m (p) is a noise component at the antenna 4.

Further, the receiving terminal B2 determines a weight v _n = [v _n1 ,..., V _nM ] ^T suitable for receiving the signal s _n (p) from the transmitting antenna 3. The output y _n (p) after signal synthesis is given by the following equation.
y _n (p) = v _n ^T x (p)
^{_{= Σ n0 = 1 N (v}} n T h n0) s n0 (p) + v n T z (p)
The reception weight v _n there are various determination methods, but the output y _{n (p)} to determine the respective reception weight v _n to approach the signal s _n (p). For example, the weight determining based on ZF (Zero Forcing) criterion, to determine the weights v _n as the following equation is satisfied.
When v _n ^T h _n0 = 1 n0 = n
= 0 n0 = other than n (Formula 1)

(Expression 1) shows a condition in which the desired signal s _n (p) is strongly received and other signals s _n0 (p) (n0 is an integer other than n) are suppressed. Therefore, only the desired signal can be received satisfactorily. Further, by receiving signals using different weights vn for different _n , a plurality of signals can be separated and extracted, and spatially multiplexed can be transmitted. Here, the weight determination method based on the ZF standard is described as an example, but there are other similar weight calculation methods such as the MMSE synthesis method. Both weight calculation methods are basically intended to suppress signals other than the desired signal, as in (Equation 1).

  As described above, the receiving side terminal B2 can realize a space division multiplexing (SDM) by suppressing signals other than the desired signal from a plurality of signals. In SDM transmission, since a plurality of signals are transmitted simultaneously, there is an advantage that high-speed signal transmission is possible as compared with a conventional transmission method in which a transceiver uses a single antenna.

However, in reality, (Equation 1) can be realized when the signal multiplexing number N is equal to or less than the number M of receiving antennas (N <= M), but cannot be realized when N> M. In order to understand this content, a more detailed explanation will be given. In (Equation 1), it can be expressed as one vector on each vector v _n and h _n0 M-dimensional space. Further, v _n ^T h _n0 is an inner product of vectors, and v _n ^T h _n0 = 0 corresponds to a state in which v _n and h _n0 are orthogonal to each other in the M-dimensional space. Incidentally, it is possible to set a vector v _n orthogonal to M-1 independent vectors h _n0 on the M-dimensional space, sets the vector v _n orthogonal to M or more independent vectors h _n0 It is impossible to do. Therefore, theoretically, it is impossible to satisfy the relationship of v _n ^T h _n0 = 0 for M or more independent vectors h _n0 , and when N> M, (Equation 1) is not feasible. Become.

As a result, when the signal multiplexing number N greater than the number of receiving antennas M, even using any weight v _n is the receiving side can not perform sufficient suppression of the other signals. Therefore, the received signal quality deteriorates rapidly. In order to avoid this situation, a method for smoothly performing spatial multiplexing transmission is required in an environment where the number of transmitting antennas is larger than the number of receiving antennas, but no solution has been shown so far.

A.V.Zelst, R.V.Nee, and G.A.Awater, “Space Division Multiplexing (SDM) for OFDM Systems” IEEE Proc. Of VTC2000 Spring, pp.1070-1074,2000 Kurosaki, Asai, Sugiyama, Umehira “Proposal of SDM-COFDM for broadband mobile communication that realizes 100 Mbit / s by MIMO channel” IEICE Tech. RCS2001-135, oct.2001

  In the conventional beam forming method, when the number of transmitting antennas is smaller than the number of receiving antennas, spatial multiplexing transmission can be performed smoothly. However, in actual wireless communication, there are many environments where the number of transmission antennas is larger than the number of reception antennas. In this case, if different signals are transmitted simultaneously from the respective transmission antennas using the conventional transmission method, the reception side cannot separate the signals from each other, and the received signal quality greatly deteriorates. Therefore, there is a need for a method that can separate signals from each other and perform high-quality signal transmission in an environment where the number of transmitting antennas is larger than the number of receiving antennas.

Even when the number of transmission antennas is smaller than the number of reception antennas, the method of transmitting signals using all the transmission antennas does not necessarily have good transmission efficiency. For example, when the two propagation vectors h _n0 and h _n1 are similar to each other, the desired signal h _n0 may be suppressed by suppressing one of the signals h _n1 . In such a case, it may be possible to perform better signal transmission by stopping one signal than transmitting two signals.

  As described above, controlling the signal transmission method may enable more efficient signal transmission. There is a need for a control method and communication method between transmission and reception that enables more efficient signal transmission in a MIMO system.

A wireless communication method according to the present invention includes:
An output signal is generated from a plurality of information signals in each of a plurality of subcarriers generated in multicarrier transmission, and the output signal is transmitted from N antennas (N is an integer of 2 or more) to a communication partner system. A wireless communication method in a wireless communication system
A receiving step of receiving control information transmitted by the communication partner system;
Based on the received control information, for each of the plurality of subcarriers, a first calculation result obtained by multiplying the first information signal by a first N-dimensional weight vector, and a second information signal A second calculation result obtained by multiplying the second N-dimensional weight vector, and a transmission step of transmitting a transmission signal generated from the N antennas,
The control information includes weight related information consisting of a set of the first and second N-dimensional weight vectors,
The weight related information is common to the plurality of subcarriers .

The wireless communication system according to the present invention is
An output signal is generated from a plurality of information signals in each of a plurality of subcarriers generated in multicarrier transmission, and the output signal is transmitted from N antennas (N is an integer of 2 or more) to a communication partner system. A wireless communication system,
Receiving means for receiving control information transmitted by the communication partner system;
Based on the received control information, for each of the plurality of subcarriers, a first calculation result obtained by multiplying the first information signal by a first N-dimensional weight vector, and a second information signal A second calculation result obtained by multiplying the second N-dimensional weight vector, and a transmission means for transmitting a transmission signal generated from the N antennas,
The control information includes a set of weight related information related to the first and second N-dimensional weight vectors,
The set of weight-related information is common to the plurality of subcarriers .

  In the wireless communication method and the wireless communication system according to the present invention, a first weight corresponding to a plurality of antennas related to one information signal and a second weight corresponding to the plurality of antennas related to another information signal are assigned to the communication partner system. The first weight is multiplied by one information signal to generate a first calculation result, the second weight is multiplied by another information signal to generate a second calculation result, and the first calculation is performed. From the result and the second calculation result, a plurality of output signals corresponding to each of the plurality of antennas are generated and transmitted to the communication partner system, so that the signal can be smoothly separated in the communication partner system. And the transmission efficiency can be improved.

The basic block diagram of the transmitter / receiver for MIMO systems in Embodiment 1 of this invention. 3 is a flowchart showing a transmission control method in the first embodiment. FIG. 3 shows a situation in which a control signal is transmitted from terminal B to terminal A in the first embodiment. FIG. 3 is a diagram illustrating a situation in which a control signal is transmitted from terminal A to terminal B in the first embodiment. FIG. 3 is a format diagram of pilot signals and control signals used in the first embodiment. FIG. 3 is a configuration diagram of a pilot signal detection unit of terminal B in the first embodiment. FIG. 10 is a diagram illustrating an outline of a transmission signal determination unit in the second embodiment. 9 is a flowchart showing a processing procedure in a transmission signal determination unit in the second embodiment. FIG. 10 is a diagram illustrating an outline of a transmission signal determination unit in a third embodiment. 10 is a flowchart illustrating a processing procedure in a transmission signal determination unit according to the third embodiment. FIG. 10 illustrates a configuration of a transmission signal determination unit in the fourth embodiment. 10 is a flowchart illustrating a processing procedure in a transmission signal determination unit in the fourth embodiment. FIG. 10 shows an SINR prediction method in the fourth embodiment. FIG. 10 is a table showing a relationship between output SINR and evaluation values in the fourth embodiment. FIG. 10 is a table showing correspondence between signal combinations and evaluation values in the fourth embodiment. 10 is a flowchart showing a processing procedure in a transmission signal determination unit in the fifth embodiment. FIG. 10 is a table showing the relationship between output SINR, transmission format, and evaluation value in the fifth embodiment. FIG. 10 is a table showing a relationship between output SINR and evaluation values in the fifth embodiment. FIG. 16 is a diagram showing an example of a format of a control signal used in Embodiment 5. 1 is a basic configuration diagram of a multicarrier communication system. FIG. 10 is a configuration diagram of a transceiver for multicarrier SDM transmission in a sixth embodiment. FIG. 10 illustrates a configuration of a transmission signal determination unit in the seventh embodiment. 18 is a flowchart showing a processing procedure in a transmission signal determination unit in the seventh embodiment. FIG. 18 shows a method for calculating an average output SINR in the seventh embodiment. FIG. 16 is a basic configuration diagram of a MIMO system transceiver in an eighth embodiment. 19 is a flowchart illustrating a transmission control method according to the eighth embodiment. FIG. 20 is a conceptual diagram of a MIMO system transceiver in Embodiment 9. 10 is a flowchart illustrating a transmission control method according to the ninth embodiment. FIG. 18 is a table showing a correspondence between signal power combinations and evaluation values in the tenth embodiment. 18 is a flowchart showing a processing procedure in a transmission signal determination unit in the tenth embodiment. FIG. 18 shows an example of a format of a control signal used in the tenth embodiment. The transceiver block diagram at the time of SDMA transmission in a prior art. The conceptual diagram which shows the transceiver structure at the time of SDMA transmission in a prior art, and reception beam formation.

Embodiment 1 FIG.
The present embodiment relates to an efficient signal transmission and communication method in a MIMO system in which a plurality of signals are spatially multiplexed (SDM) transmitted. In the following description, the information signal transmitting side is referred to as terminal A, and the receiving side is referred to as terminal B.

  FIG. 1 is the most basic transmission / reception configuration diagram showing this embodiment. FIG. 2 is a flowchart showing the control procedure of the present embodiment, and FIG. 3 shows how control information is notified from terminal B to terminal A. FIG. 4 shows a state in which an information signal is transmitted from terminal A to terminal B. 5A shows pilot signals transmitted from terminal A, and FIG. 5B shows control information (control signals) transmitted from terminal B to terminal A. FIG. 6 shows a configuration of a pilot signal detection unit in terminal B. Hereinafter, the present embodiment will be described with reference to FIGS.

  The present embodiment is a highly efficient signal transmission method applicable to a MIMO system having any number of transmission antennas.

  A basic control procedure of the present embodiment will be described with reference to FIG. First, in the present embodiment, terminal A transmits a pilot signal from each antenna before transmitting an information signal (S101). When terminal B receives the pilot signal, terminal B estimates the propagation vector of each signal as transmission-related information (S102). There are various methods for estimating the propagation vector, and specific examples will be described later. Terminal B estimates a signal to be used for transmission of an information signal based on the estimated propagation vector (S103), and notifies terminal A of the transmission signal to be used by control information (S104). Receiving the control information, terminal A selects a use antenna from the transmission signal to be used and transmits the information signal to terminal B (S105).

  By performing control based on such a procedure, a transmission antenna can be selected according to the propagation environment, and efficient signal transmission can be performed. Although this embodiment can be applied to any number of transmission / reception antennas, particularly when the number of transmission antennas N is larger than the number of reception antennas M, the number of transmission antennas used for transmission is reduced. Signal separation and reception can be performed smoothly.

FIG. 1 shows the configuration of a transceiver in this control. In the figure, the terminal A1 includes a signal transmission unit 6, a control information reception unit 7, and a transmission signal determination unit 8. On the other hand, the terminal B2 includes a pilot signal detection unit 9, a transmission signal determination unit 10, a control information transmission unit 11, and an information signal reception unit 12.
Further, 3 is an N antenna on the terminal A1 side, 4 is an M antenna on the terminal B2 side, and 5 is a propagation path between transmission and reception with a propagation characteristic matrix H = [h _mn ].

  The operation of this embodiment will be described in more detail with reference to FIGS. Before transmitting an information signal, terminal A transmits a pilot signal from each antenna (S101). The pilot signal detector 9 of the terminal B detects the pilot signal from the terminal A and estimates the propagation vector of each signal (S102). There are various methods for estimating the propagation vector, and specific examples will be described later. The transmission signal determination unit 10 selects a signal to be used for transmitting the information signal based on the estimated propagation vector. In this embodiment, a combination of signals used for information transmission is selected (S103). The control information transmission unit 11 notifies the terminal Aj of the selected combination of information using the control information (S104). FIG. 3 shows transmission of control information from terminal B to terminal A. The terminal A receives control information from the terminal B in the control information receiving unit 7, and the transmission signal determining unit 8 selects an information signal based on the control information. Thereafter, as shown in FIG. 4, terminal A selects an antenna to be used from the selected information signal, transmits a signal from the selected antenna (S105), and terminal B receives the information signal at information signal receiving unit 12. Extract.

FIG. 5 shows an example of the format of (a) pilot signal and (b) control information (control signal) used as transmission signals for this control. Terminal A transmits different pilot signals s _n (p) individually from the respective antennas. Further, in the control information from the terminal B to the terminal A, it is notified that the antenna number is transmitted (“1”) and not transmitted (“0”). Various formats can be considered as the signal format, and this format is only one example. Any pilot signal that can be used for propagation vector estimation and control signal that can notify control information. Any signal format may be used.

FIG. 6 shows a configuration in which propagation vector estimation is performed in pilot signal detector 9 of terminal B. The propagation vector estimation can be obtained by obtaining the correlation between the received pilot signal and the known pilot signal s _n (p) stored in advance in the pilot signal detection unit 9 for each antenna.

That is, for the received vector x (p) = [x ₁ (p),..., X _M (p)] ^T , the propagation vector h _n = [h ₁₁ , h ₂₁ ,. _M1 )] ^T can be estimated.
h _n = Σ _{n = 1} ^N x (p) s _n (p) *
Here, * is a complex conjugate. Normally, this operation is realized using a matched filter (MF). FIG. 6 shows an example in which propagation vector estimation is performed, but any other configuration may be used as long as it detects propagation information that is transmission-related information related to a pilot signal from a received signal. Any parameter other than the propagation vector may be used as long as it is effective propagation information regarding the pilot signal.

  When propagation information (propagation vector estimation) is calculated by the pilot signal detection unit 9, the transmission signal determination unit 10 uses the information to select a transmission signal. Various methods can be considered as a method of selecting a transmission signal. Hereinafter, in the second to fifth embodiments, some embodiments will be described with respect to the selection method of the transmission signal. However, the present invention is not limited to the example of the selection method described in Embodiments 2 to 5, and any selection that controls transmission of information signals using propagation information that is propagation-related information and improves transmission efficiency. It may be a law.

Embodiment 2. FIG.
The present embodiment relates to an efficient transmission control method and communication method in a MIMO system that performs spatial multiplexing (SDM) transmission of a plurality of signals. In particular, one specific method related to the transmission signal selection method in terminal B in the first embodiment will be described.

  FIG. 7 shows the transmission signal determination unit 10 in the present embodiment, and FIG. 8 is a flowchart showing a control procedure in the transmission signal determination unit 10. Hereinafter, a transmission signal selection method according to the present embodiment will be described with reference to FIGS.

As illustrated in FIG. 7, the transmission signal determination unit 10 selects R signals having as much power as possible from a plurality of signals. Specifically, when the transmission signal determination unit 10 of the terminal B receives the propagation vector h _n from the pilot signal detection unit 9, the transmission signal determination unit 10 selects R signals in descending order of the norm || h _n || (S201). Next, the control signal transmission unit 11 is notified of the selected signal number n (S202).

By this selection, a channel with a good propagation environment can be selected and used. Further, by making the number R of signals to be selected smaller than the number M of receiving antennas, the terminal B can also receive each signal separately.
Therefore, according to the present embodiment, it is possible to select a signal having a good propagation environment and perform signal transmission. In addition, each signal can be separated and received smoothly at the receiver.

Embodiment 3 FIG.
The present embodiment relates to an efficient transmission control method and communication method in a MIMO system that performs spatial multiplexing (SDM) transmission of a plurality of signals. In particular, this is a method related to the transmission signal selection method in terminal B in the first embodiment, and shows one method different from the second embodiment.

  FIG. 9 shows the transmission signal determination unit 10 in the present embodiment, and FIG. 10 is a flowchart showing a control procedure in the transmission signal determination unit 10. Hereinafter, the transmission signal determination method according to the present embodiment will be described with reference to FIGS.

As illustrated in FIG. 9, the transmission signal determination unit 10 selects R signals from among a plurality of transmission signals so that the mutual spatial correlation becomes as small as possible. Here, spatial correlation
| h _n1 ^H h _n2 | / (|| h _n1 || || h _n2 ||) or | h _n1 ^H h _n2 |
It can be said that the smaller the parameter is, the closer the signals n1 and n2 are to a spatially orthogonal relationship. The closer the signals are to each other, the easier it is for the terminal B to separate the two signals. Therefore, signal transmission can be performed in an environment in which signals are easily suppressed by this selection. As a result, in the terminal B, each signal can be easily separated.

As a specific control procedure, when the propagation vector h _n is estimated by the pilot signal detection unit 9 of the terminal B, the transmission signal determination unit 10 first selects a signal having a maximum norm || h _n || (S301). ). Next, the selected signal n is added to the group of the variable n1 (S302). In the initial state, the n1 group has no elements. When the number of elements of the variable n1 is less than R (S303), the sum of the spatial correlation between the signal belonging to the group n1 and the signal n Σ _n1 | h _n ^H h _n1 | / (|| h _n || _n1 |)
Is newly selected from other than the group of the variable n1 (S305), and added to the group n1 as an element (S302). When the number of n1 elements is R or more at the end of step S302 (S303), the control information transmission unit 11 is notified of the number selected as the group n1 (S304), and the process is terminated.

  Through such a series of processing, a combination of signals having a small spatial correlation can be selected, and terminal B can smoothly separate and receive each signal. As a result, highly efficient signal transmission is possible. Even when the number of transmitting antennas N is larger than the number of receiving antennas M, the signal B can be separately received by the terminal B by making the selected signal number R smaller than the number of receiving antennas M.

Embodiment 4 FIG.
The present embodiment relates to an efficient transmission control method and communication method in a MIMO system that transmits a plurality of signals to spatial multiplexing (SDM). In particular, this is a method related to the transmission signal selection method at terminal B in the first embodiment, and shows one of the methods different from the second and third embodiments.

  FIG. 11 shows a configuration of the transmission signal determination unit 10 in the present embodiment, and FIG. 12 is a flowchart showing a control procedure in the transmission signal determination unit 10. FIG. 13 is an example of the SINR prediction method used in the present embodiment, and FIG. 14 is a correspondence table between SINR and evaluation value for determining an evaluation value in the transmission signal determination unit 10. FIG. 15 shows the results of calculating evaluation values for various combinations of signals. Hereinafter, the transmission signal determination method according to the present embodiment will be described with reference to FIGS.

  As shown in FIG. 11, the transmission signal determination unit 10 includes a signal candidate selection unit 31, an output signal to interference-plus-noise (SINR) calculation unit (hereinafter referred to as an output SINR calculation unit) 32. , A transmission evaluation unit 33 and a usage signal determination unit 34.

  In the transmission signal determination unit 10, the signal candidate selection unit 31 first selects a transmission signal combination candidate (S401). The output SINR calculation unit 32 predicts the output SINR up to the terminal B obtained when the combination of the transmission signals is transmitted (S402). An example of a specific prediction method will be described later. The transmission evaluation unit 33 determines an evaluation value for a transmission signal combination candidate from the predicted SINR result (S403). This evaluation is performed on all candidates for various combinations of transmission signals (S404), and finally, the combination of transmission signals having the highest evaluation value is selected by the utilization signal determination unit 34, and the control information transmission unit 11 is selected. (S405).

FIG. 13 shows a method of predicting the output SINR of each signal performed in step S402 in the output SINR calculation unit 32.
In calculating the predicted SINR, the reception weight v _n is first calculated using the estimated propagation vector h _n .
For example, in the case of ZF criterion and MMSE combining criterion, reception weight v _n is given by the following equation.
v _n = (Σ _n0 h _n0 h _n0 ^H ) ⁻¹ h _n0 (ZF standard)
v _n = (Σ _n0 h _n0 h _n0 ^H + P _N I) ⁻¹ h _n0 (in the case of MMSE synthesis standard)

By calculating the power of the desired signal and interference noise component for the calculated reception weight, the output SINR can be obtained by the following (Equation 2).
Γ _n = | h _n ^H V _n (p) | ² / {V _n ^H (Σ _n0 h _n0 h _n0 ^H + P _N I) v _n − | h _n ^H V _n (p) | ² } (Formula 2 )
Here, _PN is noise power, and is a value estimated in advance.
The reception weight v _n is may be a ZF criterion, weights operations other than MMSE synthesis standard. It can be applied SINR prediction expression of even (Equation 2) for any weight v _n.

When the output SINR is obtained in this way, the transmission evaluation unit 33 determines a transmission evaluation value based on the SINR. Here, as a specific example, a method of setting the evaluation values to 0 and 1 according to SINR will be described. However, the present embodiment is not limited to the transmission evaluation method based on SINR, and a combination of signals can be selected based on various evaluation criteria.
In addition, the present invention can be applied to any MIMO system that performs transmission evaluation assuming signal combination candidates and performs transmission control using the result.

  The transmission evaluation unit 33 has a table for determining an evaluation value for SINR as shown in FIG. Here, the evaluation value is 1 when the SINR is 4 dB or more, and 0 otherwise. This evaluation is performed on the output SINR of each signal.

  FIG. 15 shows the results of this evaluation performed on various signal combinations 51. In the present embodiment, various combinations of transmission using three antennas are used as signal combinations. Here, the results of SINR prediction 52, evaluation value calculation 53 for each signal, and total evaluation value calculation 54 are summarized. In this way, the comprehensive evaluation value 54 is calculated for each signal combination, and the usage signal determining unit 34 selects the signal combination 55 that maximizes the comprehensive evaluation value 54.

  In the example of FIG. 15, when the antennas 1 and 2 are used and the antenna 3 is not used, the evaluation value is the maximum, and this combination 55 is selected. When there are a plurality of combinations that achieve the maximum evaluation value, any one of them is selected. The selected signal combination is notified to the terminal A through the control information transmission unit 11.

  Based on such a control method, the transmission efficiency can be evaluated from various transmission environments, and a signal combination having the best transmission efficiency can be selected. As a result, a communication system with higher transmission efficiency can be constructed as compared with a conventional MIMO system that does not perform transmission control.

  This embodiment can be used to improve transmission efficiency for any number of transmission / reception antennas. In particular, when the number of transmitting antennas is larger than the number of receiving antennas, the transmission effect can be improved while simultaneously achieving a state in which terminal B can perform signal separation, and thus the application effect is great.

Embodiment 5 FIG.
The present embodiment relates to an efficient transmission control method and communication method in a MIMO system that performs spatial multiplexing (SDM) transmission of a plurality of signals. This embodiment has the same transceiver configuration as that of Embodiment 1, but the control information notified from terminal B to terminal A is different, and in this embodiment, the transmission format of each signal is notified as transmission related information. To do.

  FIG. 16 shows a flowchart of a control procedure in the transmission signal determination unit 10 in the present embodiment. FIG. 17 is a correspondence table between the output SINR and the evaluation value for determining the evaluation value in the transmission signal determination unit 10. FIG. 18 shows the results of calculating evaluation values for various combinations of signals. FIG. 19 shows an example of a frame format of control information transmitted from terminal B to terminal A. Hereinafter, the present embodiment will be described with reference to FIGS.

  The transmission signal determination unit 10 of the present embodiment has the configuration of FIG. 11 as in the fourth embodiment, and includes a signal candidate selection unit 31, an output SINR calculation unit 32, a transmission evaluation unit 33, and a use signal determination unit 34. Consists of As a control procedure, first, the signal candidate selection unit 31 selects a transmission signal combination candidate (S501), and the output SINR calculation unit 32 predicts the output SINR of the signal for the combination (S502). The transmission evaluation unit 33 determines an evaluation value based on the output SINR result (S503). This evaluation value is calculated for all candidates for various combinations of signals (S504), and finally the combination of transmission signals having the highest evaluation value is selected by the utilization signal determination unit 34. At this time, the utilization signal determination unit 34 determines a transmission format suitable for transmitting the combination of signals, and notifies the control information transmission unit 11 of the transmission format (S505).

  FIG. 17 is a table for determining an evaluation value for the output SINR prediction value. This table shows a transmission format and a transmission speed that realize a predetermined communication quality even for an output SINR prediction value. Here, the predetermined communication quality is a request standard relating to a bit error rate (BER) or a packet error rate (PER). That is, a format such as an encoding method (encoding rate, constraint length, etc.), a modulation method, etc. is set so that the transmission rate is as high as possible within a range that satisfies the required standard BER or PER.

In FIG. 17, a coding rate 64, a modulation scheme 63, and the like to be used under a certain SINR 62 are described. In general, the higher the SINR, the stronger the bit error, so that the coding rate can be set larger. Multilevel modulation can also be used. As a result, the transmission rate 65 increases as the SINR increases.
By using this table, it is possible to determine a transmission format and a transmission rate for achieving a predetermined required quality under a certain SINR. If the transmission rate is treated as an evaluation value, the evaluation value can be calculated for various combinations of signals.

FIG. 18 shows the result of calculating the total 74 of the evaluation values using the transmission rate as the evaluation value 73 of each signal for various signal combination candidates 71. The utilization signal determination unit 34 selects a combination of signals having the maximum evaluation value 74 in FIG. In the present embodiment, a signal combination (1, 1, 0) with a total evaluation value of 10.5 is selected.
By selecting the combination with the maximum evaluation value, the transmission rate can be improved while satisfying the required quality standard in the MIMO system.

  When a combination of signals is selected in this way, the transmission format is determined with reference to FIG. 17 and notified to the terminal A through the control information transmission unit 11. FIG. 19 shows an example of the configuration of the control information (control signal) 81, and a transmission format is designated for each signal. In this figure, “0” indicates that it is not used as a transmission signal. “8”, “15”, and “6” indicate transmission format numbers when used as transmission signals. As shown in FIG. 17, “1” to “31” are selected in this embodiment. The

  As described above, terminal B uses a combination of transmission signals as transmission-related information, selects a transmission format corresponding to the combination of transmission signals, and notifies terminal A of it. The terminal A that has received the notification transmits an information signal in accordance with the notified transmission format.

  According to this method, communication with higher transmission speed can be realized while satisfying the required communication quality as compared with the conventional MIMO system that does not perform transmission control and the above-described first to fourth embodiments. Thus, by adding a degree of freedom to the transmission format, a more detailed system design is possible, and the transmission speed can be improved.

  In the above description, the transmission rate is used as the evaluation value. However, parameters other than the transmission rate may be used as the evaluation value.

Embodiment 6 FIG.
The present embodiment relates to an efficient transmission control method and communication method in a MIMO system that performs spatial multiplexing (SDM) transmission of a plurality of signals. In particular, SDM transmission that performs multicarrier transmission is shown.

  FIG. 20 is a basic configuration diagram for explaining general multicarrier transmission. FIG. 21 is a configuration diagram of transmission and reception when the MIMO system is applied to multicarrier transmission. Hereinafter, the present embodiment will be described with reference to FIGS.

  Recently, in wireless communication, there is a high demand for a system capable of high-speed transmission and high-speed movement, and it is necessary to perform broadband wireless transmission. As for broadband signal transmission, a multi-carrier scheme that performs parallel signal transmission using a plurality of carriers at the same time has attracted particular attention. In the multi-carrier transmission method, low-speed data is arranged in parallel on the frequency and transmitted simultaneously using different carriers. The transmission speed is improved by performing parallel transmission of signals.

  FIG. 20 shows a basic configuration diagram of a multicarrier communication system. As shown in the figure, the signal transmission unit 91 multiplexes a plurality of signals on a plurality of different frequencies (93 to 96) and transmits the signals. In addition, the signal receiving unit 92 on the receiving side separates signals multiplexed (93 to 96) at different frequencies and uses them as received signals for each carrier. As shown in the figure, the signals multiplexed by the multicarrier signal transmission unit 91 are multiplexed (93 to 96) and transmitted at a plurality of frequencies. At this time, signals transmitted on each carrier can be handled independently. That is, as in the case of single carrier transmission, signal processing can be performed individually for each carrier. Therefore, although Embodiments 1 to 5 have been described for the case of single carrier transmission, the same access control method can also be applied to a multicarrier transmission method.

  FIG. 21 shows a signal processing configuration in which the MIMO system of the present invention is applied to a multicarrier transmission system. As shown in this figure, by achieving the MIMO system shown in Embodiments 1 to 5 for each carrier, the MIMO system of the present invention can be applied to the multicarrier transmission system.

Embodiment 7 FIG.
The present embodiment shows a transmission control method and a communication method different from those of the sixth embodiment, particularly for SDM transmission that performs multicarrier transmission.
By performing control transmission independently for each subcarrier as shown in Embodiment 6, the same control as in the case of a single carrier can be performed. However, when independent control is performed on all subcarriers, there is a problem that the amount of control increases. Therefore, this embodiment describes a method that enables efficient signal transmission in a MIMO system while reducing the control amount.

  FIG. 22 is a configuration diagram of the transmission signal determination unit 10, and FIG. 23 is a flowchart illustrating control performed by the transmission signal determination unit 10. FIG. 24 shows an average SINR calculation method used in the transmission signal determination unit 10. Hereinafter, the present embodiment will be described with reference to FIGS.

  In the sixth embodiment, evaluation and selection are performed for each subcarrier. However, in this embodiment, one transmission evaluation and signal selection are performed for all subcarriers. That is, evaluation values for all subcarriers are set, and transmission signals for all subcarriers are selected according to the evaluation values. Various parameters such as average signal power, average spatial correlation, and average SINR can be used as the evaluation value. Here, the case where average SINR is used as one of them will be described.

  FIG. 22 shows a configuration of the transmission signal determination unit 10 when performing one transmission evaluation and signal selection for all subcarriers. In this method, first, the signal candidate selection unit 31 selects transmission signal combination candidates (S601), and the average output SINR calculation unit 35 predicts the average output SINR (S602). A method for calculating the average output SINR prediction will be described later. The transmission evaluation unit 33 determines an evaluation value for a candidate combination of transmission signals from the prediction result of the average output SINR (S603). This evaluation is performed for all the various combinations of transmission signals (S604). Finally, the combination of transmission signals having the highest evaluation value is selected by the utilization signal determination unit 34, and the control information transmission unit 11 receives the combination. Notification is made (S605).

  This method has the same configuration as that of the fourth embodiment except that the average output SINR is used instead of the output SINR. Further, the second, third, and fifth embodiments can be extended to the control method of the present embodiment at the time of multicarrier transmission by using the average signal power, the average spatial correlation, and the average SINR.

FIG. 24 shows a method for calculating the average SINR. Here, SINRΓ _{n, 1} of each subcarrier is calculated (n: transmission antenna number, l: subcarrier number) for the signal candidates simultaneously with the fourth embodiment. Thereafter, the average SINRΓ _n for all subcarriers is calculated by the following equation by averaging the SINR among the subcarriers.
Γ _n = E ₁ [Γ _{n, 1} ]
Here, E ₁ [·] indicates that an average for l is performed.

  In multicarrier transmission, encoding / decoding is usually performed across a plurality of subcarriers. In this case, the multicarrier reception characteristics greatly depend on the average SINR, and the transmission characteristics can be almost grasped by the average SINR. Therefore, in multicarrier transmission, efficient signal selection can be performed with a small amount of control by using averaging parameters for all subcarriers.

  In the present embodiment, a combination of signals to be used is selected using the average SINR, and the combination is notified to terminal A by a control signal. At this time, the control information is common to all subcarriers, and the control amount can be greatly reduced as compared with the sixth embodiment that requires a control method for each subcarrier.

Embodiment 8 FIG.
This embodiment shows a signal transmission method in terminal A that is different from those in Embodiments 1 to 7 in SDM transmission.

  In the SDM transmission according to Embodiments 1 to 7, terminal A transmits a pilot signal and an information signal from each antenna. However, it does not necessarily have to be a configuration in which a signal is individually transmitted from each antenna. In the present embodiment, a case will be described in which terminal A transmits a pilot signal and an information signal using a transmission beam.

  FIG. 25 is a block diagram of the transceiver in this embodiment, and reference numerals 111 to 113 denote transmission weight multipliers. Reference numerals 117 to 119 denote transmission beam forming. FIG. 26 is a flowchart showing a control procedure in the present embodiment. Hereinafter, the present embodiment will be described with reference to FIGS.

In this embodiment, the terminal A is a weight _{w n = [w n1, w} n2, ···, w nN] by multiplying the ^T signals for each antenna 3 to the transmission signal s _n (p). If there are multiple transmission signal is multiplied by different weights w _n respectively to generate a signal of each antenna 3 separately, transmits a plurality of signals simultaneously. In this case, the transmission signal of the terminal A has directivity and the transmission beams 117 to 119 are formed. In this way, the terminal A can transmit signals from the transmission beams 17 to 119 instead of from the antennas 3.

  A transmission control procedure of the MIMO system using the transmission beamforming will be described below with reference to FIG. Terminal A first transmits a pilot signal from each transmission beam (S701). When terminal B receives the pilot signal, terminal B estimates the propagation vector of each signal (S702). Terminal B determines a transmission beam to be used based on the estimated propagation vector (S703), and notifies terminal A of the transmission beam to be used by control information (S704). Receiving the control information, terminal A selects a transmission beam to be used and transmits an information signal to terminal B (S705).

  Thus, even when terminal A transmits a signal using a transmission beam, efficient SDM transmission is possible by transmission control between terminals A and B. Similarly, all the methods of the first to seventh embodiments can be extended when a transmission beam is used.

  Note that the number of transmission beams does not have to be the same as the number of transmission antennas. The number of transmission beams is determined by counting the number of weight multipliers, and can be made larger or smaller than the number of transmission antennas. For example, a terminal A having two antennas can transmit four signals using four transmission beams.

Embodiment 9 FIG.
This embodiment further expands the application range of the transmission control methods of Embodiments 1 and 8 in SDM transmission.

In Embodiments 1 and 8, the transmission control method has been described on the assumption that (1) terminal A transmits a signal from each antenna (2) terminal A transmits a signal from each transmission beam. However, in practice, terminal B can perform transmission control without recognizing whether the state is (1) or (2).

  FIG. 27 shows the concept of this transmission control method, and FIG. 28 shows an example of a flowchart of the present embodiment. Terminal A transmits a pilot signal in either state (1) or (2) (S801). At this time, the terminal B can estimate the propagation vector for the pilot signal without recognizing either (1) or (2) (S802). Further, if any of signal power, spatial correlation, and output SINR knows only the pilot signal sequence, terminal B can estimate it. Furthermore, an appropriate signal corresponding to the pilot signal can be selected based on the result (S803). The terminal B can also notify the signal to be used by notifying the terminal A of the number of the pilot signal to be used (S804). The terminal A that has received the control information transmits an information signal from the antenna or the transmission beam to the terminal B (S805).

  Therefore, if terminal B knows only the sequence of pilot signals, all transmission control can be performed smoothly without recognizing whether terminal A is in the state (1) or (2). As a result, regardless of the terminal B, the terminal A can use any transmission beam or the like without causing a problem in transmission control.

  From the above results, it is possible to determine in advance between transmitters / receivers using only the pilot signal sequence as a standard, and the use of the transmission beam can be left to the free judgment of each terminal. As a result, it is not necessary to recognize and notify the presence / absence of a beam between terminals, and the terminal A can use transmission beam forming with a small control amount.

Embodiment 10 FIG.
The present embodiment relates to an efficient signal transmission method and communication method in a MIMO system that performs spatial multiplexing (SDM) transmission of a plurality of signals.
In the present embodiment, the control information transmitted from terminal B to terminal A is different from that in the fifth embodiment. In particular, terminal B determines the transmission power of each signal, and in addition to the transmission format, the transmission power is also transmitted to terminal A. It is characterized by notifying.

  FIG. 30 shows an example of a flowchart of the present embodiment used in the transmission signal determination unit 10. FIG. 29 shows the result of calculation of evaluation values for various combinations of signals in the transmission signal determination unit 10. FIG. 31 shows an example of a frame format of control information (control signal) 82 transmitted from terminal B to terminal A. Hereinafter, the present embodiment will be described with reference to FIGS.

  The transmission signal determination unit 10 according to the present embodiment has the same configuration as that shown in FIG. 11, and includes a signal candidate selection unit 31, a SINR calculation unit 32, a transmission evaluation unit 33, and a use signal determination unit 34. However, the fifth embodiment is different from the fifth embodiment in that transmission power is transmitted from the terminal B to the terminal A in addition to the transmission format.

  As a control procedure, first, the signal candidate selection unit 31 selects the transmission power combination 75 of each signal (S901), and the output SINR calculation unit 32 predicts the output SINR 72 at the terminal B (S902). The transmission evaluation unit 33 calculates an evaluation value 73 for each candidate of the transmission signal from the prediction result of each output SINR 72, and determines the transmission evaluation value 74 by adding the evaluation values 73 for each candidate of the transmission signal (S903). . This evaluation is performed for all the various combinations of signal transmission power (S904), and finally, the combination of transmission power having the highest evaluation value is selected by the utilization signal determination unit 34, and the control information transmission unit 11 is selected. (S905).

  FIG. 29 shows the result of calculating the evaluation value by predicting the output SINR 72 for various combinations 75 of signal power. Here, it is assumed that the power of the information signal is changed with respect to the power of the pilot signal, and the output SINR 72 is predicted. This SINR prediction can be performed using the same calculation method as in (Expression 2). Also, an evaluation value is determined using the predicted SINR. In this way, it is possible to optimize transmission power by calculating evaluation values for various power combinations and selecting the combination having the highest evaluation value. However, when creating a combination of power, the combination of power is created so that the total power of the transmission signal is within a predetermined range.

  When a combination of the power levels of the signals is selected in this way, the combined transmission format is determined with reference to FIG. 17 and notified to the terminal A through the control information transmission unit 11 together with the transmission power. FIG. 31 shows an example of the configuration of the control signal. The transmission power corresponding to each signal is described in the left column as a ratio to the current pilot signal, and the numbers in the right column indicate the transmission format numbers. Yes. In the power term of this control signal, “0” to “3” are defined as the transmission power scale when used for the transmission signal, and the transmission format number “0” is not used as the transmission signal. As the number used as the transmission signal, “1” to “3” are selected as in the fifth embodiment.

  As described above, terminal B selects a combination of transmission powers and notifies terminal A of it. The terminal A that has received the notification transmits an information signal according to the notified transmission power and transmission format.

  In Embodiments 1 to 9, changes in signal transmission power are not considered, but in this embodiment, the power of each transmission signal can be optimized. As a result, signal transmission can be performed more efficiently in the MIMO system in consideration of transmission power.

  In the present embodiment, the case where the combination of electric power is applied to the fifth embodiment has been described. Similarly, the same technique can be applied to the first to ninth embodiments. That is, the power selection method using SINR described in this embodiment is only one specific example of the present invention, and various MIMO systems in which terminal B determines power based on propagation information and performs transmission control. Is possible.

Embodiment 11 FIG.
This embodiment shows a case where a MIMO system and a CDMA system are used in combination.

  When the DS-CDMA system, the multi-carrier CDMA system, and the MIMO system are used in combination, the same technique as in Embodiments 1 to 10 can be applied after despreading the code-spread pilot signal at the terminal B. Therefore, the transmission control methods of Embodiments 1 to 10 can be used in combination with a CDMA method such as a DS-CDMA method or a multi-carrier CDMA method.

  In the wireless communication method and the wireless communication system of the present invention, a first weight corresponding to a plurality of antennas for one information signal and a second weight corresponding to a plurality of antennas for another information signal are assigned to the communication counterpart side. Notify the system, use the first weight as the first calculation result obtained by multiplying one information signal, and the second calculation result obtained by multiplying the second weight by another information signal. Since a plurality of output signals to be generated are generated and transmitted to the communication partner system, the communication partner system can smoothly separate signals and can be applied to a wireless communication apparatus that improves transmission efficiency.

1, 2; terminal 3, 4; antenna, 5; propagation path, 6; signal transmission unit, 7; information reception unit, 8; transmission signal determination unit, terminal B2, 9; pilot signal detection unit, 10; Signal determination unit, 11; control information transmission unit, 12; control information reception unit, 31; signal candidate selection unit, 32; output SINR calculation unit, 33; transmission evaluation unit, 34; utilization signal determination unit, 35; Calculation unit, 91, 101, 102, 103; multicarrier signal transmission unit, 92, 104, 105, 106; multicarrier signal reception unit, 113; transmission weight multiplication unit, 114, 115, 116, 131, 132, 133; Receive weight multiplier.

Claims (6)

An output signal is generated from a plurality of information signals in each of a plurality of subcarriers generated in multicarrier transmission, and the output signal is transmitted from N antennas (N is an integer of 2 or more) to a communication partner system. A wireless communication method in a wireless communication system
A receiving step of receiving control information transmitted by the communication partner system;
Based on the received control information, for each of the plurality of subcarriers, a first calculation result obtained by multiplying the first information signal by a first N-dimensional weight vector, and a second information signal A second calculation result obtained by multiplying the second N-dimensional weight vector, and a transmission step of transmitting a transmission signal generated from the N antennas,
The control information includes weight related information consisting of a set of the first and second N-dimensional weight vectors,
The wireless communication method, wherein the weight related information is common to the plurality of subcarriers .   The wireless communication method according to claim 1, wherein the first and second information signals are signals modulated by different modulation schemes or signals encoded by different encoding schemes.   3. The wireless communication method according to claim 1, wherein the weight related information is common to all frequency bands used for signal transmission from the wireless communication system to a communication partner system. An output signal is generated from a plurality of information signals in each of a plurality of subcarriers generated in multicarrier transmission, and the output signal is transmitted from N antennas (N is an integer of 2 or more) to a communication partner system. A wireless communication system,
Receiving means for receiving control information transmitted by the communication partner system;
Based on the received control information, for each of the plurality of subcarriers, a first calculation result obtained by multiplying the first information signal by a first N-dimensional weight vector, and a second information signal A second calculation result obtained by multiplying the second N-dimensional weight vector, and a transmission means for transmitting a transmission signal generated from the N antennas,
The control information includes a set of weight related information related to the first and second N-dimensional weight vectors,
The wireless communication system, wherein the set of weight-related information is common to the plurality of subcarriers .   The wireless communication system according to claim 4, wherein the first and second information signals are signals modulated by different modulation schemes or signals encoded by different coding schemes.   6. The wireless communication system according to claim 4, wherein the weight related information is common to all frequency bands used for signal transmission from the wireless communication system to a communication partner system.

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