JP4570900B2 - Receiver, transmitter, radio communication system, and reception method - Google Patents

Description

  The present invention relates to a multiple input multiple output (MIMO) wireless communication system, a receiver, a transmitter, and a transmission control method, in which a transceiver includes a plurality of antennas.

  Researches have been conducted on adaptive array antennas that combine received signals from a plurality of receiving antennas after adjusting the phase and amplitude, and detect information using the combined signals.

  As a method of mounting this adaptive array antenna, there are a method of configuring to synthesize a radio frequency signal, or a method of configuring to synthesize as a baseband signal.

  First, a receiver that synthesizes a radio frequency signal will be described with reference to FIG.

The receiver 1 is connected to a plurality of antennas 2, multipliers 3 ₁ to ₃ 3 connected to the respective antennas, an adder 4 connected to the multipliers 3 _{1 to} 3 _3, and an adder 4. An RF front end 5, a weight control unit 6 and a signal detection module 7 connected to the RF front end 5 are provided. The weight control unit 6 is connected to the multiplication units 3 _{1 to} 3 ₃ .

Received signals received by the antennas 2 are multiplied by complex weights in the multipliers 3 ₁ to ₃ 3, respectively, and then input to the adder 4. The adder 4 adds the input signals and inputs them to the RF front end 5. The RF front end 5 performs AGC (automatic gain control), filtering, frequency conversion, IQ component separation, and A / D conversion on the input signal to generate a baseband signal, and the weight control unit 6 and the signal Input to the detection module 7. The weight control unit 6 generates a complex weight for the received signal based on the input signal, and inputs the generated complex weight to the multipliers 3 _{1 to} 3 ₃ . The signal detection module 7 performs signal detection.

  Next, a receiver to be combined as a baseband signal will be described with reference to FIG.

The receiver 1 includes a plurality of antennas 2, RF front ends 5 _{1 to} 5 ₃ connected to the respective antennas, and multipliers 3 ₁ to ₃ 3 connected to the RF front ends 5 _{1 to} 5 ₃ , respectively. and a multiplying section 3 ₁ to 3 ₃ and connected to the weight control unit 6 and the signal detection module 7. The weight control unit 6 is connected to each of the multiplication units 3 _{1 to} 3 ₃ .

In the receiver 1, a signal received by each antenna 2 is input to the RF front end 5 ₁ to 5 _3. The RF front ends 5 _{1 to} 5 ₃ generate baseband signals by performing AGC, filtering, frequency conversion, IQ component separation, and A / D conversion on the input signal, and multiplying units 3 ₁ to 3, respectively. 3 Input to ₃ Complex weight Each multiplying unit 3 ₁ to 3 ₃ are multiplied, the signal complex weight is multiplied is inputted to the weight control unit 6 and the signal detection module 7. The weight control unit 6 generates a complex weight for the received signal based on the input signal, and inputs the generated complex weight to the multipliers 3 _{1 to} 3 ₃ . The signal detection module 7 performs signal detection.

  On the other hand, a MIMO channel signal transmission system that includes a plurality of antennas and transmits a plurality of transmission signal sequences at the same frequency and the same time has attracted attention. A channel when transmitting a MIMO channel signal will be described with reference to FIG. 2 by taking as an example the case of transmitting with two antennas and receiving with two antennas.

In general, when a channel between the n-th transmitting antenna and the m-th receiving antenna is expressed as h _mn , the channel matrix H is expressed as shown in Equation (1).

ここで、Mは受信アンテナ数、Ｎａは送信アンテナ数である。

Here, M is the number of receiving antennas and Na is the number of transmitting antennas.

  One effective method of the MIMO channel transmission method is space division multiplexing transmission. In this method, independent signal sequences are transmitted from each transmission antenna.

As the simplest reception method for a signal sequence transmitted by space division multiplexing transmission, there is a reception method using a reception filter corresponding to an inverse matrix of a channel. S ′ = H ⁻¹ HS

ｓ_ｎはアンテナｎからの送信シンボルであり、ｓ´_ｎはアンテナｎからの送信シンボルに対する推定値である。

s _n is a transmission symbol from antenna n, and s ′ _n is an estimated value for the transmission symbol from antenna n.

  here,

Ｗ_ｎ＝[ｗ_ｎ１ ｗ_ｎ２ ・・・ ｗ_ｎＭ]
とする。この場合、受信複素ウエイトＷ_ｎは、ストリームごとに異なる。ＲＦ段で処理する場合では合成後の信号のみしか観測できないので、一種類のウエイトしか適用できない。したがって、ＲＦ段で処理する方法を適用することができない。より高度な受信方法である、受信信号レプリカのキャンセルを用いる方式や、ターボ等化を用いる場合においても、同じ受信信号に対して複数の処理をする必要があるため同様である。

W _n = [w _n1 w _n2 ... W _nM ]
And In this case, the received complex weights W _n is different for each stream. In the case of processing in the RF stage, only the synthesized signal can be observed, so only one type of weight can be applied. Therefore, it is not possible to apply a method of processing in the RF stage. The same applies to a method using cancellation of received signal replicas, which is a more advanced receiving method, and when turbo equalization is used, because a plurality of processes need to be performed on the same received signal.

  On the other hand, in the method of generating baseband signals for all receiving antennas, it can be expected that a large channel capacity can be obtained.

  In order to solve the above-described problem, a method of selecting only an antenna having a good channel state has been studied. A receiver that performs this antenna selection will be described with reference to FIG.

The receiver 1 includes a plurality of antennas (# 1 to # 3) 2, among the plurality of antennas 2, the RF front end _{5 1} and _{5 2} are connected via the two antennas and switches, RF front and a signal detection module 7 and the switch control unit 8 to the end 5 ₁ and 5 ₂ are connected, respectively. The switch control unit 8 controls the switching of switches for connecting the antenna 2 and the RF front end 5 ₁ and 5 _2. In this way, the antenna is selected. However, when antennas are simply selected, the capacity obtained when all receiving antennas are used is excessively limited by not using signals received by some antennas.

  Furthermore, in order to solve this problem, the RF processing is performed by controlling the phase or amplitude of the output signal obtained from the antenna so that the RF output becomes (number of RF stage outputs) <(number of antennas provided in the receiver). A method of outputting a signal has been proposed (see, for example, Non-Patent Document 1).

As shown in FIG. 4, the receiver includes a plurality of antennas 2 (2 ₁ to 2 ₄ ) and multiplication units 3 ₁ and 3 ₂ connected to, for example, antennas 2 ₂ and 2 ₄ among the plurality of antennas _2. When, a multiplication section _{3 1} and the antenna _{2 1} and the connecting summation unit _{4 1,} and the multiplication unit _{3 2} and the antenna _{2 3} connected summation unit _{4 2,} connected to the addition unit _{4 1} and _{4 2} RF It comprises a front end _{5 1} and _{5 2,} and RF front end _{5 1} and _{5 2} and the weight control unit 6 is connected and signal detection module 7.

In the receiver 1, of the signal received by each antenna 2, the signal received by the antenna 2 ₂ and 2 ₄ are complex weight is multiplied in the multiplication unit 3 ₁ and 3 _2, addition section 4 ₁ and 4 is input to ₂ . Adding section 4 _1, a signal received by the antenna 2 _1, complex weight received by the antenna 2 ₂ adds the signal multiplied, and inputs to the RF front end 5 _1. The addition unit 4 _2, a signal received by the antenna 2 _3, complex weight received by the antenna 2 ₄ adds the signal multiplied, and inputs to the RF front end 5 _2. Thereafter, processing similar to that of the above-described receiver is performed.

Here, it is known that the capacity of the channel is C = log ₂ det (I + ρ / NaHH ^H ). Here, det is a determinant, I is a unit matrix, and ρ is a received power to noise power density ratio. The weight control unit 6 controls the complex coefficients so that the channel capacity of the receiver 1 is maximized. In this method, characteristics close to the channel capacity obtained by providing a large number of antennas can be obtained without increasing the number of RF stage output sequences.
Nakatani, Toda et al., "MIMO receiver using RF processing type adaptive array antenna", IEICE Communication Society, B-5-17, pp.394, 2003

  However, the background art described above has the following problems.

  The degree of freedom is limited by restricting the connection between the receiving antenna and the RF front end, and there is a problem that the capacity of the channel is also limited by this limitation.

  Therefore, an object of the present invention is to provide a receiver, a transmitter, a wireless communication system, and a transmission control method that can increase the degree of freedom of a method of generating an RF output and improve characteristics.

The receiver machine,
Multiple antennas,
Among the plurality of antennas, and one or more branch portions branching each received signal of the first group of antenna and received by a portion of the first group of antennas,
A plurality of weight multiplying units for multiplying each received signal branched by the one or more branching units by a complex weight;
A plurality of adder for adding the respective received signals of the second group of antenna and received by the second group of antennas other than the first group of antennas, and an output signal of said plurality of weight multiplication unit,
A plurality of RF front-end based on the output signals of said plurality of summing unit, to generate a baseband signal,
A weight control unit for controlling a complex weight to be multiplied by the weight multiplication unit so that the capacity of the channel capacity is maximized based on the output signals of the plurality of RF front ends .
The weight control unit controls the complex weight based on the received power-to-noise power density ratio and the number of transmitter antennas so that the capacity of the channel capacity is maximized for the received signal.
By doing so, it is possible to obtain an RF output smaller than the number of receiving antennas without limiting the channel capacity.

The receiver machine,
Multiple antennas,
Among the plurality of antennas, for some of the first group of each received signal antenna and received by the first group of antennas, and one or more of the weight multiplying unit for multiplying the complex weight,
And one or more branch portions complex weight branches each received signal multiplied by said first group of antenna by the one or more weight multiplying portion,
A plurality of adder for adding the output of the one or more branches and each received signal of the second group of antenna and received by the second group of antennas other than the first group of antennas,
A plurality of RF front-end based on the output signal of the plurality of summing unit, to generate a baseband signal,
Based on the output signal of the plurality of RF front end, so that the capacity of the channel capacity is maximized, and the weight control unit for controlling the complex weight to be multiplied by the weight multiplying unit
With
The weight control unit controls the complex weight based on the received power-to-noise power density ratio and the number of transmitter antennas so that the capacity of the channel capacity is maximized for the received signal.
By doing so, it is possible to obtain an RF output smaller than the number of receiving antennas without limiting the channel capacity. Further, the number of complex weights can be reduced, and control can be facilitated.

In addition, a channel fluctuation monitoring unit that monitors channel fluctuations
With
The weight control unit may control the complex weight based on the channel fluctuation amount observed by the channel fluctuation amount observation unit .
In this way, stable reception characteristics can be obtained even when channel fluctuations are severe.

Further, based on the received signal the complex weight is multiplied, the channel estimation unit that performs channel estimation
With
The weight control unit may sequentially determine complex weights based on a result of channel estimation by the channel estimation unit .
In this way, complex weights can be sequentially determined according to changes in channel capacity.

Further, it provided on each antenna, and a plurality of switches for switching the input of the respective antennas,
A switch control unit that switches on / off of the plurality of switches, and
The switch control unit may perform control so that a signal received by one antenna is input to the RF front end.
By doing in this way, channel estimation between each transmission-and-reception antenna can be performed.

Furthermore, the weight control unit, based on signals received at each antenna may be determined complex weight.
In this way, the complex weight can be determined.

Further, the switch control unit, when receiving a frame pilot signal for channel estimation of all the antenna has been inserted, based on the insertion position of the pilot signals, the RF front-end, the received signal from the first antenna May be controlled to be input.
By doing in this way, the channel between all the transmission / reception antennas can be estimated.

Further, the switch control unit may determine the timing to turn off the switch based on the transmission / reception status.
By doing in this way, channel estimation of each transmission / reception antenna can be performed separately.

This transmit machine,
A transmission signal generation unit for generating a transmit signal,
A plurality of RF front-end for generating an RF transmission signal from an output signal of the transmission signal generating unit,
One or a plurality of branching portions for branching the RF transmission signals generated by the plurality of RF front ends ;
An adding unit for adding the first output signals of the one or more branch units ;
The output signal of the adder portion, and a plurality of weight multiplying unit for multiplying the complex weight,
Based on the feedback signal from the receiver, and the weight control unit for controlling the complex weight to be multiplied by the weight multiplying unit
A plurality of antennas for transmitting second output signals from the one or more branching units and output signals from the plurality of weight multiplication units ;
The receiver controls the complex weight based on the received power-to-noise power density ratio and the number of antennas of the transmitter so that the capacity of the channel capacity is maximized for the received signal. A feedback signal including a weight is transmitted.

  In space division multiplex transmission, generally only the number of transmission antennas for the number of streams is used. For this reason, when the number of transmission antennas is larger than the number of streams, the capacity can be improved by using the remaining antennas. Further, the number of complex weights can be reduced, and control can be facilitated.

  A wireless communication system according to the present invention includes at least one receiver and at least one transmitter. By doing so, the receiver can obtain an RF output smaller than the number of receiving antennas without limiting the channel capacity. Further, the number of complex weights can be reduced, and control can be facilitated. In addition, in the transmitter, in space division multiplex transmission, generally only the number of transmission antennas for the number of streams is used. For this reason, when the number of transmission antennas is larger than the number of streams, the capacity can be improved by using the remaining antennas. Further, the number of complex weights can be reduced, and control can be facilitated.

The receiving method according to the present invention is as follows.
A branching step of branching each received signal of the first group of antennas received by some of the first group of antennas;
A weight multiplying step for multiplying each received signal branched by the branching step by a complex weight;
An addition step of adding each reception signal of the antenna of the second group received by the antenna of the second group other than the antenna of the first group and a signal multiplied by the complex weight to generate an addition signal;
Based on the addition signal produced by the adding step, with respect to the received signal, and a wait control step of capacity of the channel capacity is controlled complex weight so as to maximize,
Based on the addition signal generated by the adding step, it has a base band signal generating step of generating a baseband signal,
The weight control step is a method of controlling the complex weight so that the capacity of the channel capacity is maximized with respect to the received signal based on the received power-to-noise power density ratio and the number of antennas of the transmitter. is there.
By doing so, it is possible to obtain an RF output smaller than the number of receiving antennas without limiting the channel capacity.

The reception method,
A weight multiplying step of multiplying each received signal of the first group of antennas received by a part of the first group of antennas among the plurality of antennas by a complex weight;
A branching step of branching each received signal of the first group of antennas multiplied by a complex weight in the weight multiplying step ;
An addition step of adding each received signal of the antenna of the second group received by the antenna of the second group other than the antenna of the first group and the signal branched by the branching step to generate an addition signal;
Based on the addition signal produced by the adding step, with respect to the received signal, and a wait control step of capacity of the channel capacity is controlled complex weight so as to maximize,
Based on the addition signal generated by the adding step, it has a base-band signal generating step of generating baseband signals,
The weight control step is a method of controlling the complex weight so that the capacity of the channel capacity is maximized for the received signal based on the received power-to-noise power density ratio and the number of antennas of the transmitter. is there.
By doing so, it is possible to obtain an RF output smaller than the number of receiving antennas without limiting the channel capacity. Further, the number of complex weights can be reduced, and control can be facilitated.

Furthermore, the way DOO control step includes a channel variation in the case of changing the complex weight is measured and based on the channel variation, it calculates a channel capacity based on the channel capacity, the complex weight it may be due to update Unishi.
In this way, complex weights can be sequentially determined according to changes in channel capacity.

In addition, the weight control step may be by that determine the number of updates per complex weight Unishi.
In this way, the number of complex weight updates can be determined.

  According to the embodiments of the present invention, it is possible to realize a receiver, a transmitter, a wireless communication system, and a transmission control method that can increase the degree of freedom of a method of generating an RF output and improve characteristics.

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

  In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

  A receiver according to the first embodiment of the present invention will be described with reference to FIG.

  The receiver according to the present embodiment performs RF processing from signals received by four antennas to obtain 2RF output.

Receiver 100 according to this embodiment includes a plurality of antennas (first to fourth antenna) 102, an adder 104 ₁ and 104 ₂ connected to the first antenna and the third antenna, the second antenna and the fourth the branch unit 108 ₁ and 108 ₂ connected to the antenna, the branch portion 108 ₁ and the addition section 104 ₁ and the multiplication unit 103 ₁ is connected to the branch portion 108 ₁ and the adding section 104 ₂ connected to the multiplying unit 103 ₂ If, the branch section ₁₀₈₂ and addition section 104 ₁ and connected to the multiplication unit 103 _4, a branch unit ₁₀₈₂ and the adder unit 104 ₂ multiplication unit 103 ₃ connected to, coupled with the addition unit 104 ₁ and 104 ₂ RF front end 105 ₁ and 105 ₂ , weight control unit 106 connected to RF front end 105 ₁ and 105 ₂ , and And a signal detection module 107. The weight control unit 106 is connected to the multiplication units 103 ₁ , 103 ₂ , 103 ₃ and 103 ₄ .

First, the signals received by the second antenna and the fourth antenna are branched into _{two at} the branching units 108 ₁ and 108 ₂ , and the signal branched at the branching unit 108 ₁ is input to the multiplying units 103 ₁ and 103 ₂ , the signal branched by the branch section ₁₀₈₂ is input to the multiplier unit 103 ₃ and 103 _4. That is, branching sections 108 ₁ and 108 ₂ branch received signals received by some of the plurality of antennas. Multipliers 103 _{1 to} 103 ₄ multiply the received signals after being branched by complex weights.

The signals multiplied by the complex weights in the multipliers 103 ₁ and 103 ₄ are input to the adder 104 ₁ , and the signals multiplied by the complex weights in the multipliers 103 ₂ and 103 ₃ are input to the adder 104 ₂ . That is, the adding unit 104 ₁ is received by the first antenna signal and second, is received by the fourth antenna, the signal complex weight is multiplied is inputted to the adder unit 104 _2, the third antenna The received signal and the signal received by the second and fourth antennas and multiplied by the complex weight are input.

Adders 104 ₁ and 104 ₂ add the input signals, and input the added signals to RF front ends 105 ₁ and 105 ₂ .

The RF front ends 105 ₁ and 105 ₂ generate and generate baseband signals by performing AGC (automatic gain control), filtering, frequency conversion, IQ component separation, and A / D conversion on the input signal. The baseband signal is input to the weight control unit 106 and the signal detection module 107. The weight control unit 106 calculates a complex weight based on the input baseband signal. Here, to connect the weight control section 106 and the addition unit ₁₀₄ 1, 104 _2, based on the addition unit ₁₀₄ 1, 104 ₂ of the output signal may be performed to calculate the complex weight. The signal detection module 107 performs signal detection based on the input baseband signal.

  In this way, 2RF output can be obtained from the signals received by the four antennas.

  Here, a sequential control method will be described as an example of a complex weight control method.

  An example of updating complex weights along the transition of time will be described with reference to FIGS.

_First , a predetermined complex weight, for example, a complex weight other than the complex weight w ′ ₁ is fixed. Here, the complex weight w _'1 is the weight control unit 106, a weight to be input, for example, in the multiplication 103 _1. Then, the channel change amount when Δw ′ is changed with respect to the complex weight w ′ ₁ is measured (step S702), and the channel capacity is calculated (step S704). For example, the channel capacity is calculated by C = log ₂ det (I + ρ / NaHH ^H ).

  Next, it is determined whether or not the calculated channel capacity has increased (step S706). As a result, if the channel capacity has increased (step S706: YES), the channel capacity is updated to w ′ + μΔw ′ (step S708).

  On the other hand, if the channel capacity has decreased (step S706: NO), the channel capacity is updated to w′−μΔw′−Δw ′ (step S710). Here, μ is a predetermined constant, for example, μ> 1.

  Next, 1 is added to i representing the number of updates (step S712). Next, it is determined whether i representing the number of updates is a set number of updates indicating the upper limit of the number of updates (step S714).

  If i representing the number of updates is less than the set number of updates (step S714: YES), the process returns to step S702.

  On the other hand, if i representing the number of updates is not less than the set number of updates (step S714: NO), the process ends. Thereafter, the same operation is repeated for other complex weights.

  In this way, complex weights can be sequentially determined according to changes in channel capacity. In addition, stable reception characteristics can be obtained even when channel fluctuations are severe.

Further, as shown in FIG. 6, for example, updating the complex weights, for example, for one complex weight w _'1, after three update (decision and setting of the weight), other complex weight w' ₂ is updated. Further, one channel estimation value is obtained from one frame.

  In the above-described embodiment, a case has been described in which one complex weight is updated three times and then another complex weight is updated. However, the number of updates per one complex weight is arbitrary. It is good also as the number of times.

In the above-described embodiment, a case has been described in which one channel estimation value is obtained from one frame. However, when more pilot signals can be inserted in one frame, for example, a complex of w ′ ₁ is used. The weight may be determined within one frame.

  Next, a receiver according to a second embodiment of the present invention will be described with reference to FIG.

  In the above-described embodiment, the method of sequentially updating the complex weight has been described. However, this method requires a relatively long time to converge the complex weight. Therefore, in the receiver according to the present embodiment, in order to perform channel estimation between the antennas, a switch is provided for each antenna, and a part of the switches are turned off at an appropriate timing for a certain period of time. A reception signal of one antenna is input to the front end.

The receiver 100 according to the present embodiment includes a plurality of antennas (first to fourth antennas) 102, a switch control unit 110 connected to each antenna (first to fourth antennas), a first antenna, and a third antenna. a switch 109 ₁ and 109 ₃ connected to the antenna, the switch 109 ₁ and 109 ₃ and connected to the adding unit 104 ₁ and 104 _2, and the second antenna and the fourth switch 109 ₂ and 109 ₄ which are connected to an antenna Branching sections 108 ₁ and 108 ₂ connected to switches 109 ₂ and 109 ₄ , multiplication section 103 ₁ connected to branching section 108 ₁ and adding section 104 _1, and connecting to branching section 108 ₁ and adding section 104 ₂ Multiplication unit 103 ₂ , the branching unit 108 _2, the multiplication unit 103 ₄ connected to the addition unit 104 ₁ , and the branching unit 108 _2. And an adder 104 ₂ and connected to the multiplication unit 103 _3, an adder 104 ₁ and 104 ₂ connected to the RF front-end 105 ₁ and 105 _2, respectively connected weight and RF front-end 105 ₁ and 105 ₂ A control unit 106 and a signal detection module 107; a weight storage unit 111 connected to the weight control unit 106; and a combined channel calculation unit 112 connected to the weight control unit 106, the weight storage unit 111 and the signal detection module 107. Prepare. The weight control unit 106 is connected to the multiplication units 103 ₁ , 103 ₂ , 103 ₃ and 103 ₄ . Further, the switch control unit 110 controls the switches 109 ₁ to 109 ₄ .

  In the present embodiment, a case will be described in which the first antenna and the third antenna are set as the first group, and the second antenna and the fourth antenna are set as the second group.

The switch control unit 110, when performing channel estimation between the respective antennas, for example, the switches 109 ₁ and 109 ₃ to a predetermined time OFF. In this case, the switch 109 ₂ and 109 ₄ is ON. In this case, the weight input to each of the multipliers 103 _{1 to} 103 ₄ is 1. The RF front-end 105 ₁ and 105 ₂ by doing so, the second group that is, only the reception signal of the second antenna and the fourth antenna are inputted.

The baseband signals generated by the RF front ends 105 ₁ and 105 ₂ are input to the weight control unit 106 and the signal detection module 107, respectively. The weight control unit 106 calculates a complex weight based on the input signal and estimates a channel between the transmission and reception antennas, inputs the calculated complex weight to the weight storage unit 111, and combines the channel estimation values between the transmission and reception antennas. Input to the channel calculator 112. Here, to connect the weight control section 106 and the addition unit ₁₀₄ 1, 104 _2, based on the addition unit ₁₀₄ 1, 104 ₂ of the output signal, and to perform the calculation and channel estimation between the transmission and reception antennas of the complex weight Also good. Further, when the channel estimation value is obtained based on the weight of the previous frame, the channel estimation value not multiplied by the weight can be obtained by dividing the channel estimation value by the weight.

Next, the switch 109 ₂ and 109 ₄ for a predetermined time OFF. In this case, the switches 109 ₁ and 109 ₃ are ON. In this case, the weight input to each of the multipliers 103 _{1 to} 103 ₄ is 1. The RF front-end 105 ₁ and 105 ₂ by doing so, the first group that is, only the received signal of the first antenna and the third antenna are inputted. The baseband signals generated by the RF front ends 105 ₁ and 105 ₂ are input to the weight control unit 106 and the signal detection module 107, respectively. The weight control unit 106 calculates a complex weight based on the input signal and estimates a channel between the transmission and reception antennas, inputs the calculated complex weight to the weight storage unit 111, and combines the channel estimation values between the transmission and reception antennas. Input to the channel calculator 112. Here, to connect the weight control section 106 and the addition unit ₁₀₄ 1, 104 _2, based on the addition unit ₁₀₄ 1, 104 ₂ of the output signal, and to perform the calculation and channel estimation between the transmission and reception antennas of the complex weight Also good. Further, when the channel estimation value is obtained based on the weight of the previous frame, the channel estimation value not multiplied by the weight can be obtained by dividing the channel estimation value by the weight.

  Next, the post-combination channel calculation unit 112 calculates a post-combination channel estimation value based on the complex weight and the input signal stored in the weight storage unit 111, and performs signal detection on the calculated post-combination channel estimation value. Input to module 107. The signal detection module 107 performs signal detection based on the input signal.

  By doing in this way, channel estimation between each transmission-and-reception antenna can be performed.

  Further, when receiving a frame in which pilot signals for channel estimation of all antennas are inserted, a reception signal from one antenna is input to the RF front end based on the insertion position of the pilot signal. You may make it control. By doing in this way, the channel between all the transmission / reception antennas can be estimated.

  Furthermore, the timing for turning off the switch may be determined based on the transmission / reception status. By doing in this way, channel estimation of each transmission / reception antenna can be performed separately.

  In this embodiment, a receiver having four antennas has been described. However, even when four or more antennas are provided, a reception signal of one antenna may be input to one RF output at each time point. it can. However, depending on the configuration of the adding unit and the branching unit, the number of groups may be more than two. At this time, it is preferable to terminate the receiving antennas not selected by the switch in consideration of the influence of reflection from these antennas.

  In this embodiment, since it is necessary to perform channel estimation for each transmitting / receiving antenna separately, the number of necessary pilot signals also increases.

A specific frame configuration will be described with reference to FIG.
Although it is possible to insert a pilot signal for the channel estimation value after combining, the insertion loss of the pilot signal increases. Therefore, a combined channel estimation value is obtained from the pilot signals of the first group and the second group and the complex weight applied to the data portion. This makes it possible to estimate the channel between all transmitting and receiving antennas, so prepare multiple complex weight candidates in advance and set the combined channel capacity for these complex weights. Calculate and use the complex weight with the largest capacity.

As candidates for complex weights, for example, a plurality of a _m and θ _n may be prepared as w = a _m exp (jθ _n ).

As for the phase rotation amount, when the number of phase rotation amount candidates is N _θ , θ _n = 2π × (n / N _θ ) (n is 1, 2,..., N _θ ). preferable.

  Next, a receiver according to a third embodiment of the present invention is described with reference to FIG.

  In the embodiment described above, a receiver that obtains 2RF output when received by four antennas has been described.

The receiver according to the present embodiment includes three antennas, and obtains 2 RF output when receiving with three antennas. Receiver 100 according to this embodiment includes a plurality of antennas (first to third antenna) 102, an adder 104 ₁ and 104 ₂ connected to the first antenna and the third antenna is connected to the second antenna and a branching unit 108, a branching unit 108 and the addition unit 104 ₁ and connected to the multiplication unit 103 _1, a branching unit 108 and the addition unit 104 ₂ and connected to the multiplication unit 103 _2, an adder 104 ₁ and 104 ₂ comprises a connection to RF front-end 105 ₁ and 105 ₂ are, the RF front-end 105 ₁ and 105 ₂ and the weight control unit 106 is connected and signal detection module 107. The weight control unit 106 is connected to the multiplication units 103 ₁ and 103 ₂ .

Initially, the signal received by the second antenna is branched into two at the branch unit 108, branch signals are inputted to the multiplication unit 103 ₁ and 103 _2. Multipliers 103 ₁ and 103 ₂ multiply the received signals after branching by complex weights.

Signal complex weight is multiplied by the multiplier 103 ₁ is input to the adder 104 _1, the signal complex weight is multiplied by the multiplication unit 103 ₂ is input to the adder 104 _2. That is, the adding unit 104 _1, a signal complex weight received by the signal and a second antenna and received by the first antenna is multiplied are input to the adder 104 ₂ is received by the third antenna signal The signal received by the second antenna and multiplied by the complex weight is input.

In the adders 104 ₁ and 104 ₂ , the input signals are added, and the added signals are input to the RF front ends 105 ₁ and 105 ₂ . The following operations are the same as those in the above-described embodiment.

In this case, the weight control unit 106 may adaptively control either one of the two coefficients, and the other complex coefficients may be constant values. Here, to connect the weight control section 106 and the addition unit ₁₀₄ 1, 104 _2, based on the addition unit ₁₀₄ 1, 104 ₂ of the output signal may be performed to calculate the complex weight.

In the above-described embodiments, the receiver that performs multiplication of complex coefficients after branching has been described. However, a configuration that performs multiplication of complex coefficients before branching may be employed. As shown in FIG. 11, the receiver 100 that performs multiplication by complex coefficients before branching includes a plurality of antennas (first to third antennas) 102 and an adder 104 ₁ connected to the first antenna and the third antenna. and 104 _2, a multiplying unit 103 connected to the second antenna, a multiplication unit 103, addition unit 104 ₁ and the adding section 104 ₂ connected to the branch portion 108, connected to the addition unit 104 ₁ and 104 ₂ RF front ends 105 ₁ and 105 ₂ , weight control unit 106 and signal detection module 107 connected to RF front ends 105 ₁ and 105 ₂ , respectively. The weight control unit 106 is connected to the multiplication unit 103.

Initially, received by the second antenna, the signal complex weight is multiplied in the multiplication unit 103 is branched into two at the branch unit 108, branch signals are inputted to the adder 104 ₁ and 104 _2.

Adding unit 104 _1, a signal received by the first antenna, complex weight received by the second antenna by adding the signal multiplied, adding unit 104 _2, signal and the received by the third antenna A signal received by two antennas and multiplied by a complex weight is added. Summed signal at the adder unit 104 ₁ and 104 ₂ are inputted to the RF front end 105 ₁ and 105 _2. The following operations are the same as those in the above-described embodiment.

By doing so, the number of complex weights can be made 1, so that control can be facilitated. Here, the signal after branching may be multiplied by a fixed complex weight. Also, connect the weight control section 106 and the addition unit ₁₀₄ 1, 104 _2, based on the addition unit ₁₀₄ 1, 104 ₂ of the output signal may be performed to calculate the complex weight.

  Next, a receiver according to a fourth embodiment of the present invention is described with reference to FIG.

  In the above-described embodiments, a receiver that generates 2RF output when received by four antennas or three antennas has been described.

  The receiver according to the present embodiment receives M antennas and obtains an RF output of M ′ (<M) (M and M ′ are integers of M> 1 and M ′> 0).

The transmitter 100 according to the present embodiment includes a plurality of antennas (first to M-th antennas) 102, branch units 108 _{1 to} 108 _M connected to the respective antennas (first antenna to M-th antenna), and branches. comprising a receiving unit ₁₁₅ 1 to 115 _M'connected to the parts ₁₀₈ 1 -108 _M, and the reception unit ₁₁₅ 1 to 115 _M'the connected RF front-end ₁₀₅ 1 to 105 _M'.

The reception unit ₁₁₅ 1 to 115 _M', described receiving unit 115 ₁ as an example. The reception unit 115 ₁ includes multiplication units 103 _{1 to} 103 _M connected to the branch units 108 _{1 to} 108 _M, and an addition unit 104 connected to the multiplication units 103 _{1 to} 103 _M , respectively. Addition section 104 is connected to the RF front-end 105 _1. Further, complex weights w _{11 to} w _1M are input to the multipliers 103 _{1 to} 103 _M , respectively. Here, the configuration below the RF front end is omitted.

Signals received by the first to Mth antennas are input to branch sections 108 _{1 to} 108 _M provided for each antenna. Each of the branch sections 108 _{1 to} 108 _M branches the input signal to M ′ (<M), and inputs each branch signal to the reception sections 115 _{1 to} 115 _{M ′} .

Each receiver unit ₁₁₅ 1 to 115 _M'is a complex weight multiplied in the multiplier unit ₁₀₃ 1 10 @ 2 to 10 @ 3 _M per branch signal corresponding to each antenna, and inputs to the adder 104. Adding section 104 adds the input signal and input to the RF front end 105 _1.

  In this embodiment, the absence of connection between the corresponding antenna and the RF stage output is equivalent to complex coefficient = 0, and the fact that multiple complex weights are the same variable is weighted before the branching section. Is equivalent to

  By doing so, it is possible to receive with a plurality of antennas and obtain an RF output smaller than the number of antennas.

  Next, a receiver according to a fifth embodiment of the present invention is described.

  Since the receiver according to the present embodiment has the same configuration as that of the above-described embodiment, the description thereof is omitted.

  When communication is performed by TDMA (Time Division Multiple Access), in downlink communication, the base station uses the pilot signal transmitted to other users without changing the frame format such as increasing the pilot signal. The receiver can determine the complex weight.

  A frame format received by the receiver according to the present embodiment will be described with reference to FIG. Here, it is assumed that the transmitter performs transmission in order from the first user to the third user. The channel estimation and complex weight determination processing is shown only for the first user.

  The first user performs channel estimation of the first group and the second group using a pilot signal transmitted to another user, for example, a pilot signal transmitted to the second user. From the channel estimation value thus determined, a complex weight is determined using the method shown in the above-described embodiment, and the complex weight is applied when the next frame is received.

  Also, in this embodiment, an example of application to TDMA has been shown. Similarly, when users are multiplexed by CDMA (Code Division Multiple Access), a common pilot signal is used, or for other users. The complex weight is determined by using the pilot signal transmitted to, and the complex weight can be applied when the next frame is received.

  Next, a transmitter according to a sixth embodiment of the present invention is described.

  Before describing the transmitter according to the present embodiment, the configuration of a frame transmitted by the transmitter will be described. As shown in FIG. 14, the frame configuration is configured by inserting a pilot signal related to the first antenna, a pilot signal related to the second antenna, and a pilot signal related to the third antenna into a normal frame. By doing in this way, the receiver can obtain | require the channel from each transmitting antenna separately.

  The optimum complex weight is determined from the channel estimation value thus obtained (the complex weight determination method is the same as that in the above-described embodiment), and the determined complex weight is fed back to the transmitter. The transmitter sets the complex weight based on the complex weight information fed back.

The transmitter 200 of the present embodiment, as shown in FIG. 15, a plurality of antennas (first to third antenna) 202, and ₂ first antenna and the third antenna and the connecting branch portion 208 ₁ and 208 , A multiplication unit 203 connected to the second antenna, branching units 208 ₁ and 208 ₂ , an addition unit 204 connected to the multiplication unit 203, an RF front end 205 ₁ connected to the branching units 208 ₁ and 208 ₂ , and 205 ₂ , a signal generation unit 213 connected to the RF front ends 205 ₁ and 205 _2, and a weight control unit 206 that receives a feedback (FB) channel and is connected to the multiplication unit 203.

The signal generated by the signal generation unit 213 is input to the RF front ends 205 ₁ and 205 ₂ , converted into a radio signal, and then input to the branching units 208 ₁ and 208 ₂ . The branching units 208 ₁ and 208 ₂ branch the input signal into two, the branching unit 208 ₁ branches the input signal to the first antenna and the adding unit 204, and the branching unit 208 ₂ sends the input signal to the third antenna and the adding unit 204. Branch. The adder 204 adds the input signals and inputs them to the multiplier 203. Multiplier 203 multiplies the input signal by a complex weight and inputs it to the second antenna. In this case, the weight control unit 206 sets a complex weight based on the complex weight information fed back from the receiver. The first to third antennas transmit input signals. In space division multiplex transmission, generally only the number of transmission antennas corresponding to the number of streams is used. For this reason, when the number of transmission antennas is larger than the number of streams, the capacity can be improved by using the remaining antennas.

  Also in the transmitter according to the present embodiment, in the TDMA downlink communication, by using the pilot signal transmitted to other users, the insertion of the pilot signal for performing the individual channel estimation in the antenna of each group is omitted. May be.

  Next, a receiver according to a seventh embodiment of the present invention is described.

  In the above-described embodiment, the method of controlling the weight following the channel variation has been described. However, these weights are applied to the next frame at the earliest. However, when processing is actually performed on the RF circuit, it may take time for the weight adjustment as compared with the baseband processing. In particular, when the channel changes suddenly, such as when the terminal is moving at high speed, or when sequential control is used to determine the optimum weight, the channel does not wait from the point of channel observation even if weight control is performed. There may be a significant change between the application time points, and in some cases, the communication path capacity may be deteriorated by the control. In such a case, it is better to fix the weight to a specific fixed value.

  Therefore, when the channel capacity is improved by the control according to the channel variation, the weight control as shown in the above-described embodiment is performed. If the characteristic deteriorates even if the control is performed, the weight is set to a constant value. Fix it. Whether the control following the channel change is possible or not is determined by providing the following mechanism for determining the amount of change in the received signal.

  As shown in FIG. 16, the receiver 100 according to the present embodiment includes a received signal fluctuation amount determination unit connected to the weight control unit 106 in the above-described embodiment, for example, the receiver 100 described with reference to FIG. 5. 114 is provided.

  The received signal fluctuation amount determination unit 114 determines the | H (of each component of the matrix from the channel matrix H (k) observed by a pilot of a certain frame and the channel matrix H (k + x) observed by a pilot of a frame separated by a certain time. k) -H (k + x) | / | H (k) | Here, | H (k) −H (k + x) | is the norm of H (k) −H (k + x) with respect to the elements of H, and | H (k) | The element takes the norm of H (k). That is, a relative error is calculated for each norm of H. When each element exceeds a preset threshold value of | H (k) −H (k + x) | / | H (k) |, the weight is fixed to a constant value, and unless it exceeds, the above weight control method is followed. Take control.

  A method for determining a constant value when the weight is fixed will be described.

  Based on the directivity pattern of each antenna in advance, that is, the directivity pattern realized at the stage where the antenna is mounted on the terminal and the antenna installation position, the directivity pattern synthesized by the antenna group (two or more) to be RF combined is omnidirectional In order to make the directivity close to the directivity, the phase gain adjustment amount is determined so as to minimize the amplitude deviation.

  For example, when a dipole antenna is used for horizontal polarization reception, the directivity pattern of one antenna is as shown in FIG. Therefore, by arranging two dipole antennas as shown in FIG. 17B and combining them with a phase difference of 180 °, the directivity pattern shown in FIG. 17C can be obtained. By adopting such directivity, even when the incoming wave comes from an arbitrary direction, almost the same antenna gain can be ensured.

  In the present embodiment, the case where the antenna is not mounted on the housing as a dipole antenna is shown, but the weight can be similarly determined even when the antenna is mounted on the housing. Further, not only the dipole antenna but also other antennas such as a microstrip antenna and an inverted F antenna can be applied by determining the weight in advance in the same manner.

  Next, when a limited pattern is prepared as a controllable weight, as a method of determining a constant value when fixing the weight, a method of fixing the weight having the highest frequency among the weights used so far to control is used. explain.

  In this case, as shown in FIG. 18, the receiver 100 described with reference to FIG. 5 includes a received signal fluctuation amount determination unit 114 and a weight storage unit 115 connected to the weight control unit 106.

  The weight storage unit 115 stores the frequency of each complex weight that has been used for control until now. The reception signal fluctuation amount determination unit 114 selects the weight having the highest frequency among the weights recorded in the weight storage unit 115 when it is determined to fix the weight to a constant value. This is because when the directivity of each antenna is an omnidirectional antenna, the frequency of each recorded weight may be uniform, but when each antenna has a biased directivity. This is effective because the weight also has a certain bias.

  Next, a radio communication system according to an eighth example of the present invention is described.

  The wireless communication system according to the present embodiment includes the receiver and transmitter according to the above-described embodiment.

  By doing so, the receiver can obtain an RF output smaller than the number of receiving antennas without limiting the channel capacity. In addition, in the transmitter, in space division multiplex transmission, generally only the number of transmission antennas for the number of streams is used. For this reason, when the number of transmission antennas is larger than the number of streams, the capacity can be improved by using the remaining antennas.

  By using the present invention, it is possible to obtain M ′ (<M) RF outputs, that is, RF outputs smaller than the number of receiving antennas, from M received signals capable of increasing the channel capacity.

  According to the embodiment of the present invention, a signal received from one receiving antenna is branched, each multiplied by a complex weight, and then added to the received signals of a plurality of antennas. With such a configuration, the degree of freedom in the method of generating the RF output can be increased and the characteristics can be improved.

  The radio communication system, the receiver, the transmitter, and the transmission control method according to the present invention can be applied to a multiple input multiple output (MIMO) radio communication system in which a transceiver includes a plurality of antennas.

It is a partial block diagram of a receiver. It is explanatory drawing for demonstrating MIMO channel signal transmission. It is a partial block diagram of a receiver. It is a partial block diagram of a receiver. It is a partial block diagram of the receiver concerning one Example of this invention. It is explanatory drawing for demonstrating the control method of a weight. It is a flowchart for demonstrating the control method of a weight. It is a partial block diagram of the receiver concerning one Example of this invention. It is a block diagram for demonstrating a frame structure. It is a partial block diagram of the receiver concerning one Example of this invention. It is a partial block diagram of the receiver concerning one Example of this invention. It is a partial block diagram of the receiver concerning one Example of this invention. It is a block diagram for demonstrating a frame structure. It is a block diagram for demonstrating a frame structure. It is a partial block diagram of the transmitter concerning one Example of this invention. It is a partial block diagram of the receiver concerning one Example of this invention. It is explanatory drawing for demonstrating the determination method of the phase gain adjustment amount. It is a partial block diagram of the receiver concerning one Example of this invention.

Explanation of symbols

1, 100 Receiver 200 Transmitter

Claims (16)

Multiple antennas,
Among the plurality of antennas, one or a plurality of branching units for branching each received signal of the first group of antennas received by some of the first group of antennas;
A plurality of weight multiplying units for multiplying each received signal branched by the one or more branching units by a complex weight;
A plurality of adders for adding each received signal of the second group of antennas received by the second group of antennas other than the first group of antennas and the output signals of the plurality of weight multipliers;
A plurality of RF front ends that generate baseband signals based on the output signals of the plurality of adders;
A weight control unit for controlling a complex weight to be multiplied by the weight multiplication unit so that the capacity of the channel capacity is maximized based on the output signals of the plurality of RF front ends.
The weight control unit controls complex weight based on the received power-to-noise power density ratio and the number of antennas of the transmitter so that the capacity of the channel capacity is maximized for the received signal. Features receiver. Multiple antennas,
Among the plurality of antennas, one or a plurality of weight multipliers for multiplying each received signal of the first group of antennas received by a part of the first group of antennas by a complex weight;
One or more branching units for branching each received signal of the first group of antennas multiplied by complex weights by the one or more weight multiplication units;
A plurality of adders for adding each received signal of the second group of antennas received by the second group of antennas other than the first group of antennas and the output of the one or more branching units;
A plurality of RF front ends for generating a baseband signal based on output signals of the plurality of adders;
A weight control unit for controlling a complex weight to be multiplied by the weight multiplication unit so that the capacity of the channel capacity is maximized based on the output signals of the plurality of RF front ends.
The weight control unit controls complex weight based on the received power-to-noise power density ratio and the number of antennas of the transmitter so that the capacity of the channel capacity is maximized for the received signal. Features receiver. The receiver according to claim 1 or 2,
The weight control unit C = log2det (I + ρ / NaHH ^H ) (C is the capacity of the channel capacity, det is the determinant, I is the unit matrix, ρ is the received power to noise power density ratio, Na is the number of transmitting antennas, H is a channel determinant), and the complex weight is controlled so that the capacity of the channel capacity is maximized. The receiver according to any one of claims 1 to 3,
A channel fluctuation monitoring unit that monitors channel fluctuations
The receiver, wherein the weight control unit controls complex weights based on a channel fluctuation amount observed by the channel fluctuation amount observation unit. The receiver according to any one of claims 1 to 4,
A channel estimation unit for performing channel estimation based on the received signal multiplied by the complex weight;
The receiver, wherein the weight control unit sequentially determines complex weights based on a result of channel estimation by the channel estimation unit. The receiver according to any one of claims 1 to 5,
A plurality of switches provided in each antenna, for switching the input of each antenna;
A switch controller for switching on / off of the plurality of switches;
With
The receiver is characterized in that the switch control unit controls the RF front end to receive a signal received by one antenna. The receiver according to claim 6, wherein
The receiver, wherein the weight control unit determines a complex weight based on a signal received by each antenna. The receiver according to claim 6 or 7,
When receiving a frame in which pilot signals for channel estimation of all antennas are inserted, the switch control unit receives a reception signal from one antenna with respect to the RF front end based on the insertion position of the pilot signal. A receiver characterized by being controlled to be input. The receiver according to any one of claims 6 to 8,
The receiver, wherein the switch control unit determines a timing to turn off the switch based on a transmission / reception state. A transmission signal generator for generating a transmission signal;
A plurality of RF front ends for generating an RF transmission signal from an output signal of the transmission signal generator;
One or more branching units for branching the RF transmission signals generated by the plurality of RF front ends;
An adding unit for adding the first output signals of the one or more branch units;
A plurality of weight multipliers for multiplying the output signal of the adder by complex weights;
Based on a feedback signal from the receiver, a weight control unit that controls a complex weight to be multiplied by the weight multiplication unit;
A plurality of antennas for transmitting second output signals from the one or more branching units and output signals from the plurality of weight multiplication units;
The receiver controls the complex weight based on the received power-to-noise power density ratio and the number of antennas of the transmitter so that the capacity of the channel capacity is maximized for the received signal. A transmitter characterized by transmitting a feedback signal including a weight. A receiver according to at least one of claims 1 and 2;
A wireless communication system comprising: the transmitter according to claim 10. A branching step of branching each received signal of the first group of antennas received by some of the first group of antennas;
A weight multiplying step for multiplying each received signal branched by the branching step by a complex weight;
Each received signal of the second group antenna received by the second group antenna other than the first group antenna is added to the signal multiplied by the complex weight in the weight multiplication step to generate an added signal. Adding step;
A weight control step for controlling the complex weight so that the capacity of the channel capacity is maximized with respect to the received signal based on the addition signal generated by the addition step;
A baseband signal generation step for generating a baseband signal based on the addition signal generated by the addition step;
The weight control step controls the complex weight based on the received power to noise power density ratio and the number of antennas of the transmitter so that the capacity of the channel capacity is maximized for the received signal. A characteristic reception method. A weight multiplying step of multiplying each received signal of the first group of antennas received by a part of the first group of antennas among the plurality of antennas by a complex weight;
A branching step of branching each received signal of the first group of antennas multiplied by a complex weight in the weight multiplying step;
An addition step of adding each received signal of the antenna of the second group received by the antenna of the second group other than the antenna of the first group and the signal branched by the branching step to generate an addition signal;
A weight control step for controlling the complex weight so that the capacity of the channel capacity is maximized with respect to the received signal based on the addition signal generated by the addition step;
A baseband signal generation step for generating a baseband signal based on the addition signal generated by the addition step;
The weight control step controls the complex weight based on the received power to noise power density ratio and the number of antennas of the transmitter so that the capacity of the channel capacity is maximized for the received signal. A characteristic reception method. The receiving method according to claim 12 or 13 ,
The weight control step includes: C = log2det (I + ρ / NaHH ^H ) (C is the channel capacity, det is the determinant, I is the unit matrix, ρ is the received power to noise power density ratio, Na is the number of transmitting antennas, H And a complex weight is controlled based on the channel determinant so that the capacity of the channel capacity is maximized. The reception method according to any one of claims 12 to 14 ,
The weight control step includes
A receiving method, comprising: measuring a channel change amount when the complex weight is changed, calculating a channel capacity based on the channel change amount, and updating the complex weight based on the channel capacity. The reception method according to claim 15 ,
In the receiving method, the weight control step determines the number of updates per complex weight.

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