JP4230933B2 - Receiver, transmitter, wireless communication system, and power distribution method - Google Patents

Description

  The present invention relates to a multiple input multiple output (MIMO) wireless communication system, a receiver and a transmitter, and a power distribution method, in which a transceiver is provided with a plurality of antennas.

  In a multi-input multi-output wireless communication system, by applying a method of feeding back a transmission form or the like to a transmitting side based on a channel estimation value, the communication capacity can be greatly increased as compared to a case where the feedback method is not applied. Can do.

In particular, a method of performing channel estimation on the receiving side and feeding back a rate and power indicator for each data substream based on the estimated value has a good tradeoff in feedback information amount and performance improvement (for example, patents) Reference 1 and Non-Patent Document 1).
JP 2002-217762 A STChung, A. Lozano, HCHuang, A. Sutivong, JMCioffi, "low Complexity Algorithm for Rate and Power Quantization in Extended V-BLAST"

  However, the background art has the following problems.

  In the receiver, the transmission signal from each transmission antenna received by each reception antenna is detected serially for each channel, and the power distribution value is calculated for each channel based on the detected transmission signal. For this reason, there is a problem that it is easily affected by error propagation when performing interference removal.

  In addition, there is a problem that power cannot be distributed to a receiver that detects each transmission data stream in parallel.

  Even when only some antennas are used, there is a problem that the communication capacity cannot be improved because power is distributed to all antennas.

  Accordingly, an object of the present invention is to provide a receiver, a transmitter, a MIMO wireless communication system, and a power distribution method that can improve the communication capacity.

  In order to solve the above problems, a receiver according to the present invention is a receiver in a wireless communication system of a multiple input multiple output (MIMO) scheme, and generates a channel estimation amount from a received data stream. Channel estimation means and power allocation determination means for simultaneously determining the power value to be allocated to each data stream based on the channel estimation amount so as to maximize the throughput.

  Further, the power allocation determining unit includes a power initialization unit that initializes a power value allocated to each data stream, a reception characteristic estimation unit that estimates a reception characteristic of each data stream, and a modulation and code based on the reception characteristic. MCS selection means for selecting a set of data and power distribution calculation means for simultaneously determining power values to be distributed to each data stream based on the set of modulation and coding so as to maximize the throughput. May be.

  Further, the MCS selection unit may select a set of modulation and coding based on the throughput.

Further, the power distribution calculating means calculates a first reception characteristic value corresponding to the selected modulation and coding set for each data stream, and uses the estimated reception characteristic value to calculate surplus power Δ = (Estimated reception characteristic value)-(First reception characteristic value) surplus power calculation means for calculating, and the first corresponding to the modulation and coding set having better reception characteristics than the reception characteristic corresponding to the modulation and coding set 2 and calculating a power difference δ = (second reception characteristic value) − (estimated reception characteristic value), a minimum value δ _min of the power difference δ is selected, and δ is selected. Sum of data streams other than _min

を計算する演算手段と、ここで、ｍは各データストリームに割り当てられた番号、strminは電力差δが最小値δ_minとなる場合のデータストリームに割り当てられた番号、P_mはｍ番目のデータストリームに対する電力配分値の初期値を示す、Δ_sumに基づいて、電力再配分を行うか否かを判断する判断手段と、判断に基づいて、電力配分値を計算する電力配分手段とを備えるようにしてもよい。

Where m is the number assigned to each data stream, strmin is the number assigned to the data stream when the power difference δ is the minimum value δ _min, and P _m is the mth data. A determination unit for determining whether to perform power redistribution based on _Δsum indicating an initial value of a power distribution value for the stream, and a power distribution unit for calculating a power distribution value based on the determination. It may be.

Further, the determining means determines whether or not to perform power redistribution based on Δsum and (10 ^{δmin / 10} −1) × P _strmin × GP, and the power distributing means is based on the determination result,
P _strmin = P _strmin × 10 ^{δmin / 10}
P _{m (m ≠ strmin)} = P _{m (m ≠ strmin)} -((1-10 ^{-Δm / 10} ) / Δ _sum ) × P _strmin × (10 ^{δmin / 10} -1)
Here, P _strmin may be calculated by calculating the power distribution value distributed to the data stream in which the power difference δ is the minimum value δ _min .

Further, the power distribution calculating means calculates a third reception characteristic value indicating a reception characteristic corresponding to the modulation and coding set having a higher throughput than the throughput in the modulation and coding set, and estimates the estimated reception characteristic value , Second power difference calculation means for calculating second power difference δ = (third reception characteristic value) − (estimated reception characteristic value), and throughput, modulation, and code in a set of modulation and coding Select the maximum difference Th _max between the modulation corresponding to the throughput corresponding to the encoding set and the throughput corresponding to the encoding set, and the sum of the data streams other than the data stream that becomes Th _max.

ここで、strmaxはTh_maxに対応するデータストリームの番号を示す、を計算する第２の演算手段と、Δ_sumに基づいて、電力再配分を行うか否かを判断する判断手段と、判断に基づいて、電力配分値を計算する電力配分手段とを備えるようにしてもよい。

Here, Strmax the second calculating means for calculating a indicates the number of the data stream corresponding to Th _max, based on the delta _sum, determining means for determining whether to perform the power redistribution, the determination Based on this, power distribution means for calculating a power distribution value may be provided.

Further, a first reception characteristic value corresponding to the selected modulation and coding set for each data stream is calculated, and the surplus power Δ = (estimated reception characteristic value is calculated using the estimated reception characteristic value. )-(First reception characteristic value) surplus power calculation means, and a third reception characteristic value indicating the reception characteristic corresponding to the modulation and coding set having higher throughput than the throughput in the modulation and coding set And second power difference calculation means for calculating second power difference δ = (third reception characteristic value) − (estimated reception characteristic value), and throughput, modulation, and code in a set of modulation and coding Select the maximum difference Th _max between the modulation corresponding to the throughput corresponding to the encoding set and the throughput corresponding to the encoding set, and the sum of the data streams other than the data stream that becomes Th _max.

ここで、strmaxはTh_maxに対応するデータストリームの番号を示す、
を計算する第２の演算手段と、第２の演算手段の出力Δ_sumに基づいて、電力再配分を行うか否かを判断する第２の判断手段と、第２の判断手段の判断に基づいて、第２の電力配分値を計算する第２の電力配分手段と、電力配分値及び第２の電力配分値に基づいて、スループットを見積もるスループット推定手段とを備え、電力配分手段は、見積もられたスループットに基づいて電力配分値を決定するようにしてもよい。

Here, strmax indicates the number of the data stream corresponding to Th _max .
Second calculating means for calculating a, on the basis of the output delta _sum of the second arithmetic unit, a second determination means for determining whether or not to perform power redistribution, based on the determination of the second determining means The second power distribution means for calculating the second power distribution value and the throughput estimation means for estimating the throughput based on the power distribution value and the second power distribution value. The power distribution value may be determined based on the obtained throughput.

  Further, the judging means has a maximum or minimum throughput corresponding to the selected modulation and coding set for each data stream, and a difference in reception characteristics corresponding to the modulation and coding set is a predetermined value. If it is less than or equal to the value, it may be determined that power redistribution is performed, and the power distribution unit may perform power distribution so that reception characteristics are equal.

Further, determination means, delta _sum and ⁽¹⁰ δstrmax ^/ 10 -1) × based on the _P strmax × GP, it may be determined whether to perform the power redistribution.

  Furthermore, antenna pattern setting means for setting the antenna pattern to be used, throughput estimation means for estimating the throughput based on the calculated power distribution value, and antenna selection for selecting the antenna pattern to be used based on the throughput Means.

  Further, the transmitter according to the present invention is a transmitter in a radio communication system of a multiple input multiple output (MIMO) system, receiving means for receiving a power distribution value, and based on the power distribution value, Receiver-side reception characteristic estimation means for estimating reception characteristics on the receiver side.

Furthermore, an encoding & modulation means for performing encoding and modulation processing based on the received modulation and encoding set may be provided.
The wireless communication system according to the present invention is a multiple input multiple output (MIMO) wireless communication system including a transmitter and a receiver, and the transmitter receives a power distribution value. Means and receiver-side reception characteristic estimation means for estimating reception characteristics on the receiver side based on the power distribution value, and the receiver comprises channel estimation means for generating a channel estimation amount from the received data stream; Power distribution determining means for simultaneously determining the power value to be allocated to each data stream based on the channel estimation amount so as to maximize the throughput.

  Further, the power distribution method according to the present invention is a power distribution method in a multiple input multiple output (MIMO) wireless communication system, and generates a channel estimation amount from a received data stream. And simultaneously determining the power value to be allocated to each data stream based on the channel estimation amount so as to maximize the throughput.

  In addition, the reception characteristics of each data stream are estimated, and the throughput corresponding to the modulation and coding set selected for each data stream is the maximum or minimum value, and the modulation and coding set is supported. A step of determining that power redistribution is performed when a difference in reception characteristics is equal to or less than a predetermined value.

  And a step of setting an antenna pattern to be used, a step of estimating a throughput based on the calculated power distribution value, and a step of selecting an antenna pattern to be used based on the throughput. May be.

  According to the embodiments of the present invention, it is possible to realize a receiver, a transmitter, a MIMO wireless communication system, and a power distribution method that can improve communication capacity.

  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 configuration of a MIMO wireless communication system that performs adaptive transmission power control according to a first embodiment of the present invention will be described with reference to FIG.

  The MIMO wireless communication system 100 according to the present embodiment includes a transmitter 110 and a receiver 120.

  Transmitter 110 includes encoding & modulation sections 101-1 to 101-N to which transmission data is input, and power amplification sections 103-1 to 103 connected to encoding & modulation sections 101-1 to 101-N, respectively. -N, transmission antennas 105-1 to 105-N connected to power amplifiers 103-1 to 103-N, respectively, and rate control unit 102 connected to encoding & modulation units 101-1 to 101-N And a power control unit 104 connected to the power amplification units 103-1 to 103 -N.

  The transmission data is encoded and modulated by encoding and modulation sections 101-1 to 101-N. In this case, the modulation scheme and transmission rate are controlled by the rate control unit 102. The encoded and modulated transmission signals are power-amplified by power amplification sections 103-1 to 103-N and transmitted from transmission antennas 105-1 to 105-N. In this case, transmission power is controlled by the power control unit 104.

In addition, a receiver-side reception characteristic estimation unit (not shown) that estimates reception characteristics on the receiver 120 side based on the feedback signal transmitted from the receiver 120 is provided. The rate control unit 102 and the power control unit 104 are The transmission rate and transmission power may be controlled based on the estimated reception characteristics.
The receiver 120 includes reception antennas 111-1 to 111 -N, a channel estimation unit 112 connected to the reception antennas 111-1 to 111 -N, and a power distribution / MCS (Modulation and MCS) connected to the channel estimation unit 112. (Coding Set) (modulation and coding set) selection unit 113, signal separation unit 114 connected to reception antennas 111-1 to 111-N, and decoding & demodulation unit 115 connected to signal separation unit 114 Prepare.

The reception data received by the reception antennas 111-1 to 111 -N is input to the channel estimation unit 112 and also input to the signal separation unit 114.
The received data input to the signal separation unit 114 is separated into signals for each transmission sequence, and is decoded and demodulated by the decoding & demodulation unit 115. On the other hand, the channel estimation unit 112 examines a change caused by a propagation path related to amplitude, delay, or phase for each received reception antenna from the input reception signal, performs channel estimation, and outputs the result as a power distribution / MCS selection unit 113 is input. The power distribution / MCS selection unit 113 performs MCS selection based on the input channel estimation value, and determines power distribution based on the selected MCS. Further, the power distribution / MCS selection unit 113 transmits the result of MCS and power distribution to the rate control unit 102 and the power control unit 104 of the transmitter 100.

  Before describing the power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system according to the present embodiment, the configuration and processing of the conventional power distribution / MCS selection unit will be described with reference to FIGS. Will be described with reference to FIG.

  As shown in FIG. 2, the power distribution / MCS selection unit includes a data stream contour 1, a power initialization unit 2 connected to the data stream contour 1, and a SINR (Signal-to-to-connection unit) connected to the power initialization unit 2. Interference plus Noise Ratio) estimation unit 3, MCS selection unit 4 connected to SINR estimation unit 3, power mapping unit 5 connected to MCS selection unit 4, power mapping unit 5 and data stream contour 1 And the MCS reselection unit 7 connected to the determination unit 6 and the power mapping unit 5.

  The data stream contour 1 controls the number of the data stream transmitted by the transmitter based on the channel estimation amount generated by the channel estimation unit. For example, after assigning m as a data stream number, m = m−1 (1 <m <M) (m is a positive integer), thereby sequentially assigning a number to each data stream. Here, m is the number of data streams.

The power initialization unit 3 initializes the power distribution value. For example, the power is initialized by P _m = P _remain / m. Here, P _m is the power of the m-th data stream, and P _remain is the power that can be allocated to the m-th data stream, that is, the remaining power.

The SINR estimation unit 3 estimates SINR after the reception process is performed.
The MCS selection unit 4 performs MCS selection based on the SINR estimated by the SINR estimation unit 3.

The power mapping unit 5 is provided in advance and performs mapping of power corresponding to the selected MCS using a table in which MCS and power are associated with each other. For example, the power P _m for the selected MCS is mapped.
The determination unit 6 determines whether the allocated power exceeds the undistributed power. For example, first

を計算する。ここで、Pは総電力(total power)、Mは受信アンテナの数である。次に、P_remain−P_m>0であるか否かの判定を行う。

Calculate Here, P is the total power and M is the number of receiving antennas. Next, it is determined whether or not P _remain −P _m > 0.

As a result of the determination by the determination unit 6, the MCS reselection unit 7 determines that the allocated power P _m exceeds the remaining power P _remain , that is, if P _remain −P _m <0. Reselect. For example, a process for lowering the MCS by one step is performed.
Next, the processing flow of the power distribution / MCS selection unit will be described with reference to FIG.

  When the channel estimation amount is input from the channel estimation unit 112, in the data stream contour 1, for example, m is assigned as a data stream number to m data streams larger than 0, and the value of m is reduced by 1. By repeating the process of assigning m obtained by subtracting the value of m to the next data stream, control for assigning a number to the data stream is performed (step S1).

Next, power initialization is performed. For example, a value obtained by dividing the remaining power P _remain by the number of data streams m, that is, P _m = P _remain / m is set as an initial value (step S2).

  Next, SINR after reception processing is estimated (step S3), MCS is selected based on the estimated SINR (step S4), and power mapping is performed based on the selected MCS (step S4). Step S5).

Next, it is determined whether or not the allocated power exceeds the remaining power P _remain (step S6). If the allocated power exceeds the remaining power (step S6: NO), the MCS is reselected (step S8). On the other hand, when the allocated power does not exceed the remaining power (step S6: YES), the power distribution value is output (step S7).

  Next, the configuration of the power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system 100 according to the present embodiment will be described with reference to FIG.

  The power distribution / MCS selection unit 113 includes a power initialization unit 113-1, a reception characteristic estimation unit 113-2 connected to the power initialization unit 113-1, and an MCS connected to the reception characteristic estimation unit 113-2. A selection unit 113-3 and a power distribution calculation unit 113-4 connected to the MCS selection unit 113-3 are provided.

  In addition, the power distribution calculation unit 113-4 includes an upper MCS power difference (δ) calculation unit 113-41 and a surplus power (Δ) calculation unit 113-42 connected to the MCS selection unit 113-3, and an upper MCS power difference. (Δ) calculation unit 113-41 and surplus power (Δ) calculation unit 113-43 and determination unit 113-44 connected to calculation unit 113-42, upper MCS power difference (δ) calculation unit 113-41, surplus A power distribution unit 113-45 connected to the power (Δ) calculation unit 113-42, the calculation unit 113-43, and the determination unit 113-44. The calculation unit 113-43 is connected to the determination unit 113-44.

The power initialization unit 113-1 sets the initial value of the power distribution value for each data stream. For example, when the number of repetitions (loop) of the power distribution calculation is 0, that is, when the calculation is performed for the first time, the power coefficient distributed to each antenna is P = (P ₁ ,..., P _M ). However,

である。
次に、電力を規格化し

It is.
Next, standardize power

とする。P_m=P/M(m=1,…,M)とすると、各データストリームの初期値は、Ｐ_１＝，．．．，Ｐ_Ｍ＝１となる。

And When P _m = P / M (m = 1,..., M), the initial value of each data stream is P ₁ =,. . . , P _M = 1.

When loop> 0, the power distribution value determined by the power distribution unit 113-45 described later is set as the initial value. After setting the initial value, increase the number of repetitions (loop = loop + 1).
The reception characteristic estimation unit 113-2 estimates reception characteristics after reception, for example, SINR. For example,
SINR _m = u _m ² / u _m -u _m ² = u _m / 1-u _m
u _m = h _m ^H w _m
W _m = [hA _m h ^H + σ ² I] ^-1 h _m

により、各データストリームの受信後等価SINRの計算を行う。ここで、SINR_mは、ｍ番目のデータストリームのSINR、h_mはｍ番目のチャネル値（伝達関数）、^Hは行列の共役転置、w_mはフィルタ係数、σ²は受信機の内部雑音電力（雑音成分の共分散）、Iは単位行列、A_mは単位対角行列である。

Thus, after receiving each data stream, the equivalent SINR is calculated. Here, SINR _m is, SINR of the m-th data stream, h _m is the m-th channel values (transfer function), the conjugate transpose of ^H is a matrix, w _m filter coefficients, sigma ² is the internal noise power of the receiver (Covariance of noise components), I is a unit matrix, and _Am is a unit diagonal matrix.

  Based on the reception characteristics of each data stream estimated by the reception characteristics estimation section 113-2, the MCS selection section 113-3 selects an MCS set that satisfies a predetermined reception quality for each data stream. Here, the desired reception characteristics for each data stream are different. For example, MCS corresponding to each reception quality, for example, reception characteristics, modulation scheme, transmission rate, throughput, and the like are associated with each other, and an MCS corresponding to the estimated reception characteristics is selected from a prestored table. If there are a plurality of corresponding MCS sets, the MCS set having the largest throughput is selected. For example, based on the estimated SINR value, an MCS necessary for the frame error rate (FER) to reach a constant value e is selected for each data stream.

  The upper MCS power difference (δ) calculation unit 113-41 has a reception characteristic that is higher than the MCS set arranged in the upper stage of the MCS set selected by the MCS selection unit 113-3, that is, the reception characteristic corresponding to the selected MCS set. The difference between the SINR corresponding to the good MCS set and the SINR of each data stream is obtained.

For example, the desired SINR of each MCS at FER = e is (γ ₁ ,..., Γ _L ), and the number of the MCS set selected for each data stream is I _m (1 <m <M). However, it is assumed that a total of L set, and _{γ 1 <... <γ l <} ... γ L. in this case,
δ _m = γ _{Im + 1} -SINR _m
Is calculated.

The surplus power (Δ) calculation unit 113-42 obtains a difference between the SINR of each data stream and the desired SINR. For example,
Δ _m = SINR _m -γ _Im
Is calculated.

The calculation unit 113-43 calculates the minimum value δ _min of δ calculated by the upper MCS power difference (δ) calculation unit 113-41. In addition, the sum of the surplus power _Δsum excluding _δmin is calculated. For example, δ _min = {δ ₁ ,..., Δ _M } is obtained, and the number of the data stream having the value is defined as strmin. next,

の計算を行う。

Perform the calculation.

The determination unit 113-44 determines whether to perform power distribution. For example, by comparing the delta _sum and ^{(10 δmin / 10 -1) ×} P strmin × GP, it determines whether or not to power distribution. Here, GP is guard power and is a parameter set in advance.

である場合には、電力配分を行う旨の判断が行われる。
一方、Δ_sum<(10^δmin/10-1)×P_strmin×GPである場合には、電力配分を行わない旨の判断が行われる。

If so, a determination is made to perform power distribution.
On the other hand, if Δ _sum <(10 ^{δ min / 10} −1) × P _strmin × GP, it is determined that power distribution is not performed.

The power distribution unit 113-45 obtains a power distribution value when it is determined to perform power distribution. For example,
P _strmin = P _strmin × 10 ^{δmin / 10}
P _{m (m ≠ strmin)} = P _{m (m ≠ strmin)} -((1-10 ^{-Δm / 10} ) / Δ _sum ) × P _strmin × (10 ^{δmin / 10} -1)
To obtain the power distribution value. The result is fed back to the power initialization unit 113-1.

  On the other hand, when it is determined that power distribution is not performed, the process is stopped, and the current power distribution value and the selected MCS set are fed back to the transmitter 110.

  Next, a power distribution method in the MIMO wireless communication system according to the present embodiment will be described with reference to FIGS.

  The channel estimation unit 112 performs channel response and noise estimation using the input pilot signal. The channel estimation unit 112 inputs the result to the power initialization unit 113-1, and the power initialization unit 113-1 uses the output result from the channel estimation unit 112 to assign the power distribution value to each data stream. An initial value is set (step S100).

  Next, the reception characteristic estimation unit 113-2 calculates reception characteristics after reception processing, for example, equivalent SINR after reception of each data stream (step S110). For example, when OFDM (Orthogonal Frequency Division Multiplexing) is used as the modulation method, the reception characteristics of the data stream are estimated using the reception characteristics of each subcarrier and the dispersion of the reception characteristics.

  Next, based on the estimated reception characteristics of each data stream, the MCS selection unit 113-3 performs, with respect to each data stream, one MCS set that satisfies a predetermined reception quality, for example, FER. The MCS set with the highest throughput is selected (step S120).

  Based on the result of the MCS selection unit 113-3, the power distribution determination unit 113-4 determines whether or not to perform power distribution, and performs power distribution based on the determination result.

This will be specifically described. The upper MCS power difference (δ) and surplus power (Δ) are calculated in the upper MCS power difference (δ) calculating unit 113-41 and the surplus power (Δ) calculating unit 113-42 (step S130). Next, the arithmetic unit 113-43 performs surplus power sum delta _sum calculations excluding the minimum value [delta] _min and [delta] _min of [delta] (step S140). Next, the determination unit 113-43 determines whether to perform power distribution (step S150).

  When it is determined that power distribution is to be performed (step S150: YES), the power distribution unit 113-45 performs power distribution and feeds back the result to the power initialization unit 113-1 (step S160). In addition, the power distribution unit 113-45 feeds back the MCS and the power distribution value to the transmitter 110 (step S170).

  The power initialization unit 113-1 sets the fed back power distribution value as the initial power value, and the reception characteristic estimation unit 113-2 transmits the power distribution value calculated using the power distribution value. Is estimated. That is, the processing of Step S100 to Step S170 is repeatedly performed using the fed back power distribution value. Thus, by repeating the process, a more optimal power distribution value can be calculated.

  On the other hand, when it is determined that power distribution is not performed, the power distribution unit 113-45 feeds back the power distribution value at the current stage and the selected MCS set to the transmitter 110 (step S170).

  The rate control unit 102 of the transmitter 110 that has received the feedback information from the receiver 120 controls the encoded & modulated signal of each data stream based on the feedback information. The power control unit 104 controls transmission power of each data stream.

  When a receiver-side reception characteristic estimation unit (not shown) that estimates reception characteristics on the receiver 120 side based on the feedback signal transmitted from the receiver 120 is provided, the rate control unit 102 and The power control unit 104 controls the transmission rate and transmission power based on the estimated reception characteristics.

  Next, a power distribution method in the MIMO wireless communication system according to the present embodiment will be described in detail with reference to FIG. FIG. 6 shows a case where power distribution is performed on four data streams. Note that the MCS selection unit 113-3 selects an optimal MCS from three types of MCS.

First, a data stream having a minimum Δ is selected (1), and power is transferred from another data stream to the data stream selected in (1) (2). Next, recalculation is performed and (1) and (2) described above are repeated (3). Here, Δ is the difference between the reception characteristic corresponding to the MCS set having better reception characteristics than the reception characteristic corresponding to the MCS set and the estimated reception characteristic.
By doing so, the power distribution value and MCS of each transmission data stream can be determined at the same time, and can be brought closer to the optimum value by repeated calculation, so that a larger communication capacity can be achieved.

  Next, a MIMO radio communication system according to the second embodiment of the present invention will be described.

In the MIMO wireless communication system according to the present embodiment, the configuration of the transmitter / receiver is the same as that of the first embodiment, and thus the description thereof is omitted.
Next, the configuration of the power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system 100 according to the present embodiment will be described.

  The power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system 100 according to this embodiment is different from the power distribution / MCS selection unit 113 described in the first embodiment in the upper MCS power difference (δ). The functions of the calculation unit 113-41, the calculation unit 113-43, and the determination unit 113-44 are different.

The upper MCS power difference (δ) calculation unit in the MIMO wireless communication system 100 according to the present embodiment obtains the throughput corresponding to the MCS set selected by the MCS selection unit 113-3, and the MCS having a higher throughput than the obtained throughput. Obtain the reception characteristics corresponding to the set. For example, determine the throughput Th _m for each data stream, obtains the reception characteristics corresponding to the larger one than Th _m determined throughput, input from the reception characteristic obtained a reception characteristic estimating unit 113-2 receives Find the difference from the characteristics.

Calculating unit 113-43 has upper MCS power difference ([delta]) was determined in the calculation unit _{Th m (m = 1, ...} , M) is greater than Th _m obtained with, for example, the throughput corresponding to a single large MCS sets And the maximum value Th _max of the difference is obtained, and the number of the data stream corresponding to the Th _max is defined as strmax. Also,

の計算を行う。

Perform the calculation.

The determination unit 113-44 determines whether to perform power distribution. For example, by comparing the delta _sum and ^{(10 δstrmax / 10 -1) ×} P strmax × GP, it determines whether or not to power distribution. Here, δ _strmax is δ _whose data stream number is strmax. If it is ^{_{Δ sum <(10 δstrmax / 10}} -1) × P strmax × GP performs judgment to the effect that performs power distribution. on the other hand,

である場合には、電力配分を行わない旨の判断を行う。

If it is, it is determined that power distribution is not performed.

  In addition, the determination unit 113-44 has a maximum or minimum throughput corresponding to the selected modulation and coding set for each data stream, and a difference in reception characteristics corresponding to the modulation and coding set. Is determined to be redistributed when the value is equal to or less than a predetermined value. In this case, the power distribution unit 113-45 performs power distribution so that the reception characteristics are equal.

  Next, a power distribution method in the MIMO wireless communication system according to the present embodiment will be described with reference to FIG.

  Since the power distribution method in the MIMO wireless communication system according to this embodiment differs from the power distribution method in the MIMO wireless communication system according to the first embodiment in the processes after step S130, the processes after step S130 will be described. To do.

  As illustrated in FIG. 7, when the MCS is selected by the MCS selection unit 113-3 (step S120), the power distribution determination unit 113-4 performs power distribution based on the result of the MCS selection unit 113-3. Is determined, and power distribution is performed based on the determination result. That is, the calculation of the throughput, the upper MCS power difference (δ), and the surplus power (Δ) is performed in the upper MCS power difference (δ) calculation unit 113-41 and the surplus power (Δ) calculation unit 113-42 (steps). S180).

Next, the calculating unit 113-43, a surplus power sum delta _sum calculations are performed except for the data stream corresponding to Th _max and Th _max (step S190). Next, the determination unit 113-43 determines whether or not to perform power distribution (step S200). When it is determined that power distribution is to be performed (step S200: YES), power distribution is performed, and the result is fed back to the power initialization unit 113-1 (step S210).

  Next, in the power distribution unit 113-45, the MCS and the power distribution value are fed back to the transmitter 110 (step S220).

  The power initialization unit 113-1 sets the fed back power distribution value as the initial power value, and the reception characteristic estimation unit 113-2 transmits the power distribution value calculated using the power distribution value. Is estimated. That is, the processing of steps S100 to S120 and steps S180 to S220 is repeatedly performed using the fed back power distribution value.

  On the other hand, when it is determined that power distribution is not performed (step S200: NO), the power distribution unit 113-45 feeds back the current power distribution value and the selected MCS set to the transmitter 110. (Step S220).

  Upon receiving the feedback information from the receiver 120, the transmitter 110 controls the coding & modulation signal of each data stream based on the feedback information, and the power control unit 104 determines the transmission power of each data stream. Control.

  Further, in step S200, the throughput corresponding to the modulation and coding set selected for each data stream is the maximum value or the minimum value, and the difference in reception characteristics corresponding to the modulation and coding set is a predetermined value. If the value is less than or equal to the value, the determination unit 113-43 determines to perform power redistribution. In this case, in step S200, the power distribution value is calculated so that the reception characteristics are equal.

  When a receiver-side reception characteristic estimation unit (not shown) that estimates reception characteristics on the receiver 120 side based on the feedback signal transmitted from the receiver 120 is provided, the rate control unit 102 and The power control unit controls the transmission rate and the transmission power based on the estimated reception characteristics.

  With this configuration, the power distribution value can be calculated simultaneously so as to maximize the throughput of the wireless communication system.

  Next, a MIMO radio communication system according to the third embodiment of the present invention is described.

  In the MIMO wireless communication system according to the present embodiment, the configuration of the transmitter / receiver is the same as that of the first embodiment, and thus description thereof is omitted.

  Next, the configuration of the power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system 100 according to the present embodiment is the same as the configuration of the power distribution / MCS selection unit 113 described in the first and second embodiments. In addition, a throughput estimation unit (not shown) that estimates throughput based on the selected MCS and power distribution value is provided.

  Next, a power distribution method in the MIMO wireless communication system according to the present embodiment will be described.

  In the power distribution method in the MIMO wireless communication system according to the present embodiment, both the power distribution method described in the first embodiment and the power distribution method described in the second embodiment are executed. Next, the throughput estimation unit estimates the throughput using the selected MCS and the calculated power distribution value. The power distribution unit 113-45 selects, for example, the larger desired throughput based on the result estimated by the throughput estimation unit, performs power distribution, and feeds back the result to the power initialization unit 113-1. Further, the power distribution unit 113-45 feeds back the MCS and the power distribution value to the transmitter 110.

  By doing so, it is possible to improve throughput while ensuring communication capacity.

  Next, a MIMO radio communication system according to the fourth embodiment of the present invention will be described with reference to FIGS.

In the MIMO wireless communication system according to the present embodiment, the configuration of the transmitter / receiver is the same as that of the first embodiment, and thus the description thereof is omitted.
Next, the configuration of the power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system 100 according to the present embodiment will be described.

  The power distribution / MCS selection unit 113 of the receiver 120 in the MIMO wireless communication system 100 according to the present embodiment includes a power initialization unit 113-1 in addition to the power distribution / MCS selection unit 113 described in the first embodiment. An antenna usage pattern initialization unit 113-5 connected to the power distribution unit 113-45, a throughput estimation unit 113-46 connected to the power distribution unit 113-45, and an antenna selection unit 113-47 connected to the throughput estimation unit 113-46. It differs in that it is equipped with.

  The antenna usage pattern initialization unit 113-5 inputs the antenna pattern to be used to the power initialization unit 113-1 under the condition that the total transmission power is constant. The antenna pattern indicates which antenna is used when some of the M antennas are used.

  The throughput estimation unit 113-46 estimates a desired throughput when the current antenna pattern is used. The antenna selection unit 113-47 selects an antenna pattern that maximizes the desired throughput based on the desired throughput estimated by the throughput estimation unit 113-46, and transmits the power distribution value corresponding to the selected antenna pattern to the transmitter. 110 is fed back.

  Next, a power distribution method in the MIMO wireless communication system according to the present embodiment will be described with reference to FIG.

  The power distribution method in the MIMO wireless communication system according to the present embodiment and the power distribution method in the MIMO wireless communication system according to the first embodiment are that antenna initialization pattern initialization processing is performed before step S100, As a result of the determination, processing is different when it is determined that power distribution is not performed.

  As shown in FIG. 9, first, an antenna usage pattern is initialized (step S90). For example, when a part of the M reception antennas is used, the antenna usage pattern initialization unit 113-5 determines the antenna pattern indicating the antenna to be used as the power initialization unit 113-1. (Step S90).

  As a result of the determination in step S150, when it is determined that power distribution is not to be performed (step S150: NO), the throughput estimation unit 113-46 of the power distribution calculation unit 113-4 uses the current antenna pattern. The desired throughput is estimated (step S230).

  Next, antenna selection section 113-47 selects the antenna pattern having the highest throughput from the desired throughput estimated by throughput estimation section 113-46, and transmits the power distribution value corresponding to the selected antenna pattern. The feedback is made to the machine 110 (S240).

  In the transmitter 110 that has received the feedback information from the receiver 120, the rate control unit 102 controls the encoding and modulation signal of each data stream based on the feedback information, and the power control unit 104 determines the transmission power of each data stream. Be controlled.

  When a receiver-side reception characteristic estimation unit (not shown) that estimates reception characteristics on the receiver 120 side based on the feedback signal transmitted from the receiver 120 is provided, the rate control unit 102 and The power control unit 104 controls the transmission rate and transmission power based on the estimated reception characteristics.

  Next, effects of the embodiment of the present invention will be described with reference to FIG.

  FIG. 8 is a diagram for explaining the effect of the multiple input multiple output wireless communication system according to the embodiment of the present invention. In FIG. 8, the Y axis indicates the communication capacity. According to FIG. 8, it can be seen that the MIMO wireless communication system according to the present embodiment has a clear effect of improving the communication capacity as compared with the conventional wireless communication system.

  In this embodiment, the influence of error propagation is reduced by changing the power distribution value for all data streams from the method of serial calculation to the method of simultaneous calculation so that the throughput of the wireless communication system is maximized. be able to.

  Furthermore, by feeding back the calculation result of the power distribution value to the power initialization unit and the reception characteristic estimation unit and performing recalculation, the power distribution value can be approached to the optimum value, thereby improving the characteristics. Can do.

  Furthermore, the present invention can be applied not only to a receiving device that detects a received signal serially but also to a receiving device that detects signals simultaneously in all data streams.

  Furthermore, since it can be applied to the case where only a part of the antennas are used, the communication capacity can be improved particularly in a region where SINR is low.

  The radio communication system according to the present invention can be applied to a multiple input multiple output radio communication system.

It is a block diagram for demonstrating the structure of the radio system of a MIMO system which concerns on the Example of this invention. It is a block diagram for demonstrating the structure of the electric power allocation and MCS selection part in the receiver which comprises the radio | wireless communications system of a MIMO system. 5 is a flowchart for explaining a power distribution method in a MIMO wireless communication system. It is a block diagram for demonstrating the structure of the electric power allocation and MCS selection part in the receiver which comprises the radio | wireless communications system of the MIMO system which concerns on 1st Example of this invention. 3 is a flowchart for explaining a power distribution method in the MIMO wireless communication system according to the first embodiment of the present invention; It is explanatory drawing for demonstrating the power distribution method in the radio | wireless communications system of the MIMO system which concerns on 1st Example of this invention. 7 is a flowchart for explaining a power distribution method in a MIMO wireless communication system according to a second embodiment of the present invention. It is a block diagram for demonstrating the structure of the power distribution and MCS selection part in the receiver which comprises the radio | wireless communications system of the MIMO system which concerns on 3rd Example of this invention. 6 is a flowchart for explaining a power distribution method in a MIMO wireless communication system according to a third embodiment of the present invention. It is explanatory drawing for demonstrating the effect of the radio system of a MIMO system which concerns on the Example of this invention.

Explanation of symbols

100 wireless communication system 105-1 to 105-N transmitting antenna 111-1 to 111-M receiving antenna

Claims (15)

A receiver in a wireless communication system of multiple input multiple output (MIMO) system:
Channel estimation means for generating a channel estimator from the received data stream;
Power initialization means for setting an initial value to a power value allocated to each data stream based on the channel estimation amount;
Receiving characteristic estimating means for estimating the receiving characteristic of each data stream;
MCS selection means for selecting a set of modulation and coding based on the reception characteristics;
Power allocation calculation means for simultaneously determining power values to be allocated to each data stream based on the set of modulation and coding so as to maximize the throughput;
A receiver comprising: In the receiver of claim 1 :
The receiver according to claim 1, wherein the MCS selection means selects a set of modulation and coding based on throughput. In the receiver according to claim 1 or 2 ,
The power distribution calculating means includes
A first reception characteristic value corresponding to the selected modulation and coding set selected for each data stream is calculated, and surplus power Δ = (estimated reception characteristic value is calculated using the estimated reception characteristic value. )-(First received characteristic value) surplus power calculating means;
A second reception characteristic value corresponding to the modulation and coding set having better reception characteristics than the reception characteristic corresponding to the modulation and coding set is calculated, and a power difference δ = (second reception characteristic value) − (estimation). Power difference calculating means for calculating (reception characteristic value);
Select the minimum value δ _min of the power difference δ, and the sum of the data streams other than the data stream that becomes δ _min

Computing means for calculating
Here, m is the number assigned to each data stream, strmin is the number assigned to the data stream when the power difference δ is the minimum value δ _min, and P _m is the initial power distribution value for the mth data stream Indicating the value,
Judgment means for judging whether to redistribute power based on _Δsum ;
Power distribution means for calculating a power distribution value based on the determination;
A receiver comprising: In the receiver of claim 3 :
The determination means determines whether to perform power redistribution based on Δsum and (10 ^{δmin / 10} −1) × P _strmin × GP;
The power distribution means is based on the determination result,
P _strmin = P _strmin × 10 ^{δmin / 10}
P _{m (m ≠ strmin)} = P _{m (m ≠ strmin)} -((1-10 ^{-Δm / 10} ) / Δ _sum ) × P _strmin × (10 ^{δmin / 10} -1)
Here, P _Strmin is shows the power distribution value allocated to the data stream power difference [delta] is a minimum value [delta] _min, GP represents a guard power,
And calculating a power distribution value. In the receiver according to claim 1 or 2 ,
The power distribution calculating means includes
A first reception characteristic value corresponding to the selected modulation and coding set selected for each data stream is calculated, and surplus power Δ = (estimated reception characteristic value is calculated using the estimated reception characteristic value. )-(First received characteristic value) surplus power calculating means;
A third reception characteristic value indicating a reception characteristic corresponding to a modulation and coding set having a higher throughput than that of the modulation and coding set is calculated, and a second power difference δ = (third reception characteristic value). )-(Estimated reception characteristic value) second power difference calculating means for calculating;
Select the maximum value Th _max of the throughput in the modulation and coding set and the difference between the throughput corresponding to the modulation and coding set having a higher throughput than the throughput corresponding to the modulation and coding set, and Th _max and Sum of data streams other than

Here, strmax indicates the number of the data stream corresponding to Th _max .
Second computing means for calculating
Judgment means for judging whether to redistribute power based on _Δsum ;
Power distribution means for calculating a power distribution value based on the determination;
A receiver comprising: In the receiver of claim 3 :
A third reception characteristic value indicating a reception characteristic corresponding to a modulation and coding set having a higher throughput than that of the modulation and coding set is calculated, and a second power difference δ = (third reception characteristic value). )-(Second estimated power characteristic value) second power difference calculating means;
Select the maximum value Th _max of the throughput in the modulation and coding set and the difference between the throughput corresponding to the modulation and coding set having a higher throughput than the throughput corresponding to the modulation and coding set, and Th _max and Sum of data streams other than

Here, strmax indicates the number of the data stream corresponding to Th _max .
Second computing means for calculating
Second determination means based on the output delta _sum of said second arithmetic means, to determine whether to power redistribution;
Second power distribution means for calculating a second power distribution value based on the determination of the second determination means;
Throughput estimation means for estimating throughput based on the power distribution value and the second power distribution value;
With
The receiver, wherein the power distribution means determines a power distribution value based on the estimated throughput. In the receiver according to claim 5 or 6 :
The judging means has a maximum or minimum throughput corresponding to the selected modulation and coding set for each data stream, and a difference in reception characteristics corresponding to the modulation and coding set is predetermined. If it is less than the value of
The receiver, wherein the power distribution means performs power distribution so that reception characteristics are equal. In the receiver according to claim 5 or 6 :
The determining means, based on the delta _sum and ^{(10 δstrmax / 10 -1) ×} P strmax × GP, determines whether to perform the power redistribution, wherein, GP represents a guard power,
A receiver characterized by that. In the receiver according to any one of claims 1 to 8:
Antenna pattern setting means for setting the antenna pattern to be used;
A throughput estimating means for estimating the throughput based on the calculated power distribution value;
Antenna selection means for selecting a pattern of an antenna to be used based on the throughput;
A receiver comprising: A transmitter in a wireless communication system of multiple input multiple output (MIMO) system:
Receiving means for receiving the power distribution value;
Receiver-side reception characteristic estimation means for estimating reception characteristics on the receiver side based on the power distribution value;
A transmitter comprising: In the transmitter of claim 10 ,
Coding and modulation means for performing coding and modulation processing based on the received modulation and coding set;
A transmitter comprising: A multiple input multiple output (MIMO) wireless communication system including a transmitter and a receiver:
The transmitter is
Receiving means for receiving the power distribution value;
Receiver-side reception characteristic estimation means for estimating reception characteristics on the receiver side based on the power distribution value;
With
The receiver
Channel estimation means for generating a channel estimator from the received data stream;
A power allocation determining means for simultaneously determining a power value to be allocated to each data stream based on the channel estimation amount so as to maximize the throughput;
A wireless communication system comprising: A power distribution method in a multiple input multiple output (MIMO) wireless communication system:
Generating a channel estimator from the received data stream;
Setting an initial value to a power value allocated to each data stream based on the channel estimation amount generated in the step of generating the channel estimation amount;
Estimating the reception characteristics of each data stream;
Selecting a set of modulation and coding based on the reception characteristics estimated in the step of estimating the reception characteristics;
Simultaneously determining a power value to be allocated to each data stream based on the modulation and coding set selected in the step of selecting the modulation and coding set so as to maximize throughput;
A power distribution method characterized by comprising: The power distribution method according to claim 13:
The throughput corresponding to the modulation and coding set selected for each data stream is the maximum value or the minimum value, and the difference in reception characteristics corresponding to the modulation and coding set is equal to or less than a predetermined value. Determining to redistribute power if
A power distribution method characterized by comprising: In the power distribution method according to claim 13 or 14,
Setting the antenna pattern to be used;
Estimating the throughput based on the calculated power distribution value;
Selecting an antenna pattern to be used based on the throughput;
A power distribution method characterized by comprising:

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