JP2011103583A - Mimo evaluation device, and mimo evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate reception characteristics in a receiver including a plurality of reception antennas regardless of the configuration of the antennas. <P>SOLUTION: The MIMO evaluation device 100 evaluates the reception characteristics of a receiver that receives, via N reception antennas, a signal transmitted by a transmitter having M transmission antennas. Using one evaluation antenna 101, a wireless receiving unit 102 receives signals transmitted by each of the M transmission antennas, and on the basis of the received signals, a data computation unit 103 estimates M estimated channel values between each of the M transmission antennas and the evaluation antenna. Subsequently, a calculation unit 106 uses the M estimated channel values and a correlation matrix of the N reception antennas to calculate a channel matrix between the M transmission antennas and the N reception antennas, and an evaluation unit 107 evaluates the reception characteristics using the channel matrix. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MIMO evaluation apparatus and a transmission method for a MIMO evaluation method.

  In recent years, the field of wireless communication has been remarkably developed, and research has been continued to further increase the transmission speed. One of the techniques for realizing an increase in transmission speed is a MIMO (Multiple Input Multiple Output) transmission technique.

  MIMO transmission is a communication method in which a plurality of streams are simultaneously transmitted on the same frequency using a plurality of transmission antennas and a plurality of reception antennas. In MIMO transmission, a receiver (for example, a mobile terminal) performs a process of separating a plurality of streams transmitted on the same frequency from a transmitter (for example, a base station).

  At this time, the reception characteristic of the receiver changes depending on the propagation path (channel) condition. Therefore, it is necessary to grasp the characteristics of the incoming signal at the receiving end in each area where data communication is performed between the transmitter and the receiver (that is, the area where the MIMO communication service is performed). Here, in the MIMO transmission, it is necessary to grasp the reception characteristics at the receiver by measuring the limit value of the communication capacity at the reception end in addition to the measurement of the electric field strength of the incoming signal at the reception end.

  Therefore, in order to evaluate the reception characteristics at the receiver, it is conceivable to measure the maximum throughput (for example, transmission quality in an ideal state such as Shannon's channel capacity) in each area where the MIMO communication service is performed. The maximum throughput (Shannon's channel capacity) is the bandwidth of the received signal (BW: Band Width), the signal-to-noise ratio (SNR), and the channel between multiple transmit antennas and multiple receive antennas. It is calculated using a channel matrix (MIMO channel matrix) indicating the estimated value.

  For example, in order to evaluate the reception characteristics (maximum throughput) of a receiver in a MIMO communication system, a mobile terminal having a plurality of reception antennas receives signals transmitted from the plurality of transmission antennas and obtains a channel matrix. Has been proposed (see, for example, Patent Document 1).

JP 2009-182679 A

  However, the mobile terminal is variably controlled in the data area allocated to the own terminal according to the channel environment (that is, the channel estimation value measurement environment). For this reason, when other mobile terminals other than the mobile terminal that evaluates the reception characteristics exist in the same area, the data area of the mobile terminal that evaluates the reception characteristics may be changed. Therefore, the obtained reception characteristics (maximum throughput) may change depending on the data area allocated to the mobile terminal whose reception characteristics are evaluated.

  Moreover, since the arrangement position of the antenna of the mobile terminal is determined in consideration of the design of the mobile terminal and the like, there is a restriction that the reception antenna cannot be arranged at an ideal position for evaluating reception characteristics (maximum throughput). That is, when evaluating the reception characteristics of a mobile terminal (receiver) in MIMO transmission, the antenna arrangement of the mobile terminal varies depending on the type of mobile terminal, and the obtained reception characteristics are values specific to the mobile terminal. Therefore, if it is intended to evaluate the reception characteristics with the mobile terminal itself, the evaluation must be performed for the number of types of mobile terminals, and the evaluation work becomes complicated.

  Therefore, it is conceivable to use a MIMO evaluation apparatus that has a plurality of antennas and is a dedicated apparatus for evaluating reception characteristics. This makes it possible to evaluate the reception characteristics (maximum throughput) of MIMO transmission with an ideal antenna arrangement. However, the obtained reception characteristic (maximum throughput) is a result depending on the physical configuration of a plurality of reception antennas (for example, the distance between the antennas or the orientation of the antenna with respect to the transmitter). That is, the MIMO evaluation apparatus can obtain only reception characteristics depending on the physical configuration of the antenna.

  An object of the present invention is to provide a MIMO evaluation apparatus and a MIMO evaluation method capable of measuring reception characteristics of a receiver having a plurality of reception antennas without depending on the arrangement of antennas.

  The MIMO evaluation apparatus according to the present invention is a MIMO evaluation apparatus that evaluates reception characteristics of a receiver that receives signals transmitted from a transmitter having M transmission antennas by N reception antennas, Receiving means for receiving signals transmitted from the transmitting antennas with one evaluation antenna, and M channel estimation between each of the M transmitting antennas and the evaluation antenna based on the received signals A channel matrix between the M transmit antennas and the N receive antennas using an estimation means for estimating a value, the M channel estimate values, and a correlation matrix of the N receive antennas A configuration is provided that includes calculation means for calculating the reception characteristics and evaluation means for evaluating the reception characteristics using the channel matrix.

  The MIMO evaluation method of the present invention is a MIMO evaluation method for evaluating the reception characteristics of a receiver that receives signals transmitted from a transmitter having M transmission antennas by N reception antennas. A reception step of receiving signals transmitted from the transmission antennas by one evaluation antenna, and M channel estimation between each of the M transmission antennas and the evaluation antenna based on the received signals A channel matrix between the M transmit antennas and the N receive antennas using an estimation step for estimating a value, the M channel estimate values, and a correlation matrix of the N receive antennas And a calculation step for calculating the reception characteristic using the channel matrix.

  According to the present invention, it is possible to evaluate reception characteristics of a receiver having a plurality of reception antennas without depending on the antenna arrangement.

The block diagram which shows the structure of the MIMO evaluation apparatus which concerns on one embodiment of this invention The figure which shows the example of arrangement | positioning of the pilot signal which concerns on one embodiment of this invention The figure which shows the MIMO communication system which concerns on one embodiment of this invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the MIMO evaluation apparatus according to the present embodiment. In the following description, the MIMO evaluation apparatus receives reception characteristics (maximum) of a receiver (mobile terminal) that receives a signal transmitted from a transmitter (base station) having M transmission antennas by N reception antennas. Throughput).

  A MIMO evaluation apparatus 100 shown in FIG. 1 has one antenna 101 (evaluation antenna). In MIMO evaluation apparatus 100, radio reception section 102 receives signals transmitted from M transmission antennas of a transmitter (base station) via antenna 101, down-converts the received signal, performs A / D conversion, and the like. Receive processing. Then, the wireless reception unit 102 outputs the reception signal after the reception process to the data calculation unit 103. The received signal includes a pilot signal (sometimes referred to as a pilot signal or a reference signal) transmitted from each transmitting antenna of the transmitter (base station) (a signal known on the transmission / reception side) and Contains data signals.

  The data calculation unit 103 obtains a channel estimation value, a bandwidth (BW) of the received signal, and an S / N ratio (SNR) using the received signal input from the wireless receiving unit 102. Specifically, the data calculation unit 103 estimates a channel estimation value between each transmission antenna of the transmitter (base station) and the antenna 101 (evaluation antenna) based on a pilot signal included in the received signal. That is, the data calculation unit 103 estimates M channel estimation values between each of the M transmission antennas of the transmitter (base station) and the antenna 101, that is, (M × 1) channel estimation values. In addition, the data operation unit 103 obtains the bandwidth and SNR of the received signal by demodulating the received signal. Then, the data calculation unit 103 outputs the obtained channel estimation value, received signal bandwidth and SNR to the calculation unit 106 of the data integration processing unit 105.

  In the information acquisition unit 104, position information including information indicating the position (area) of the MIMO evaluation apparatus 100 or information indicating the progress of the position of the MIMO evaluation apparatus 100 obtained from GPS data or vehicle speed pulses, etc. From the processing unit (not shown). The information acquisition unit 104 acquires time information indicating the time when the information included in the position information is measured from an external processing unit (not shown). Then, the information acquisition unit 104 outputs the acquired position information to the integration unit 108 of the data integration processing unit 105. Note that the information acquisition unit 104 may have a GPS processing function therein, and acquire position information using the GPS processing function.

  The data integration processing unit 105 includes a calculation unit 106, an evaluation unit 107, and an integration unit 108. Further, the data integration processing unit 105 holds a correlation matrix (a matrix that models the reception antenna configuration) unique to the N reception antenna configurations of the receiver that is the evaluation target. Specifically, the correlation matrix of the receiving antenna defines a value specific to the receiving antenna configuration (for example, the antenna interval), and the arrival angle of the signal (arriving wave) received by the receiving antenna or the signal (arriving wave) It is a matrix in which angular spread (angle spread) is made constant.

  The calculation unit 106 uses the M channel estimation values input from the data calculation unit 103 and the correlation matrix of the N reception antennas to determine the channel between the M transmission antennas and the N reception antennas. Calculate the matrix. Specifically, the calculation unit 106 first arranges N (M × 1) channel estimation values between the M transmission antennas of the transmitter (base station) and the antenna 101 in the row direction, XN) channel estimates are generated. Then, the calculation unit 106 multiplies the (N × N) correlation matrix and the generated (M × N) channel estimation value to calculate the (M × N) channel matrix. Then, the calculation unit 106 outputs the received signal bandwidth, SNR, and the calculated channel matrix to the evaluation unit 107.

  The evaluation unit 107 evaluates reception characteristics (maximum throughput) of a receiver having N reception antennas using the bandwidth, SNR, and channel matrix of the reception signal input from the calculation unit 106. Then, the evaluation unit 107 outputs information including the obtained reception characteristics (maximum throughput) to the integration unit 108.

  The integration unit 108 integrates the reception characteristics (maximum throughput) input from the evaluation unit 107 and the information (time information, position information, etc.) input from the information acquisition unit 104. That is, the integration unit 108 associates the reception characteristic (maximum throughput) with the time or position (area) at which the reception characteristic is evaluated. Then, the integration unit 108 outputs the integrated data to the storage unit 109 and the display unit 110.

  The accumulation unit 109 accumulates data input from the integration unit 108.

  The display unit 110 displays data input from the integration unit 108 or data (past data) input from the storage unit 109. For example, the display unit 110 may plot and display a mark indicating the size of the maximum throughput on each area where the maximum throughput is evaluated based on map data (not shown). Or the display part 110 may display the magnitude | size of the maximum throughput in a specific area for every different transmitter (base station), for example with a bar graph or a line graph.

  Next, the operation of the MIMO evaluation apparatus 100 will be described in detail.

  In the following description, the pilot signal transmitted from the transmitter (base station) is transmitted independently for each stream. For example, FIG. 2 shows an example of pilot signal arrangement when performing (4 × 4) MIMO communication which is the maximum format in 3GPP LTE (3rd Generation Partnership Project Long Term Evolution). ‘1’, ‘2’, ‘3’, and ‘4’ illustrated in FIG. 2 represent pilot signals transmitted from each of the four transmission antennas 1 to 4. Therefore, each receiving antenna of the receiver can individually perform channel estimation of a plurality of streams from the transmitter (base station).

  Further, in the following description, in the MIMO communication system shown in FIG. 3, the number of transmitting antennas M of the transmitter (base station) is two (antennas # T1 and # T2), and the number of receiving antennas of the receiver (mobile terminal). Let N be two (antennas # R1, # R2). That is, MIMO evaluation apparatus 100 according to the present embodiment evaluates reception characteristics (maximum throughput) of a receiver (mobile terminal) when performing (2 × 2) MIMO communication. In FIG. 3, the antenna 101 of the MIMO evaluation apparatus 100 corresponds to the reception antenna # R1 of the receiver.

In FIG. 3, S ₁ (t) is a signal transmitted from the transmission antenna # T1 of the transmitter (base station), and S ₂ (t) is a transmission antenna # T2 of the transmitter (base station). It is a signal transmitted from. In FIG. 3, h ₁₁ (f) is a channel estimation value when signal S ₁ (t) of transmission antenna #T ₁ is received by reception antenna #R 1 (antenna 101). H ₁₂ (f) is a channel estimation value when the signal S ₂ (t) of the transmission antenna # T2 is received by the reception antenna # R1 (antenna 101). In FIG. 3, h ₂₁ (f) is a channel estimation value when the signal S ₁ (t) of the transmission antenna # T1 is received by the reception antenna # R2, and h ₂₂ (f) is a transmission antenna. This is a channel estimation value when the signal S ₂ (t) of # T2 is received by the reception antenna # R2 of the mobile terminal.

Therefore, the data calculation unit 103 of the MIMO evaluation apparatus 100 shown in FIG. 1 has 2 (= M) pieces of data based on the pilot signals respectively transmitted from the transmission antennas # T1 and # T2 of the transmitter (base station). Channel estimation values (a channel estimation value h ₁₁ (f) between transmission antenna # T1 and antenna 101 and a channel estimation value h ₁₂ (f) between transmission antenna # T2 and antenna 101) are estimated.

Next, the calculation unit 106 of the data integration processing unit 105 uses the channel estimation value [h ₁₁ (f) h ₁₂ (f)] obtained by the data calculation unit 103 as the evaluation target receiver. (2 × 2) channel estimation values are generated by arranging them in the row direction by the number of reception antennas (N = 2 in FIG. 3). That is, the calculation unit 106 arranges N (M × 1) channel estimation values obtained by the data calculation unit 103 to generate a (M × N) channel estimation value.

Next, the calculation unit 106 calculates the (N × N) correlation matrix of N (= 2) reception antennas and the generated (M × N) channel estimation (here, (2 × 2) matrix). (M × N) channel matrix (here, (2 × 2) between M (= 2) transmit antennas and N (= 2) receive antennas according to the following equation (1): ) Matrix).

In Expression (1), ρ _a (0) and ρ _a (Δx) included in the correlation matrix indicate complex spatial correlation coefficients, and Δx indicates an interval between receiving antennas. Further, while ρ _a (0) = 1, ρ _a (Δx) is expressed by the following equation (2).

In Expression (2), θ represents an arrival angle of a received signal with respect to a baseline where a plurality of receiving antennas are arranged, and Ω (θ) represents an angular space profile. That is, the complex spatial correlation coefficient ρ _a (Δx) is weighted with a profile (Ω (θ)) on the angle space in consideration of a change in the phase of the wave (received signal) due to a change in the position of the receiving antenna. It is an integral value.

Here, the distribution of the received level variation assumed in the propagation path between the transmitting and receiving (channel), a method of deriving a complex spatial correlation coefficient [rho _a is different. Hereinafter, as an example of the derivation of the complex spatial correlation coefficient ρa, _a case where the distribution of the reception level fluctuation is the Rayleigh distribution (derivation example 1) or the angle distribution (derivation example 2) will be described. However, in the receiver, it is assumed that all receiving antennas are arranged on the baseline (that is, the antenna configuration of the receiver is a linear array).

[Derivation example 1: Rayleigh distribution]
The Rayleigh distribution models a channel environment (hereinafter referred to as a Rayleigh environment) when there is no excellent wave such as a line-of-sight wave. The angular space profile Ω (θ) in the Rayleigh environment is expressed by the following equation (3). However, here, the receiving antennas have omni directivity, and the receiving antennas are orthogonal to each other.

Here, _{P R} represents the received power. Thus, the complex spatial correlation coefficient [rho _a Rayleigh environment is represented by the following formula (4).

In other words, if it is a Rayleigh environment, the theoretical value of the complex spatial correlation coefficient ρ _a included in the correlation matrix is the positional relationship between the plurality of receiving antennas of the receiver, as shown in the above equation (4). It can be derived by (Δx).

[Derivation example 2: Angular distribution]
The angular distribution models a channel environment such as when the receiving antenna has directivity or when the incoming waves of signals transmitted by the transmitter (base station) are not uniformly distributed. The angular space profile Ω (θ) when using the angular distribution is expressed by the following equation (5).

Here, θ ₀ indicates the angle of arrival of the radio wave from the transmitter to the receiving antenna, and σ _θ indicates the angle spread. Therefore, the complex spatial correlation coefficient ρ _a when using the angular distribution is expressed by the following equation (6).

As shown in the above equation (6), when using the angle distribution, not only the interval Δx between the receiving antennas but also the arrival angle θ ₀ and the angle spread σ _θ need to be known (in equation (4)). In the Rayleigh distribution shown, the arrival angle θ ₀ and the angle spread σ _θ need not be known).

The example of deriving the complex spatial correlation coefficient ρ _a has been described above.

Thereby, as shown in Expression (1), the calculation unit 106 calculates the channel estimated value [h ₁₁ (f) h ₁₂ (f)] obtained based on the received signal received only by the antenna 101 (in FIG. 3). H ₂₁ (f) = ρ _a (Δx) h ₁₁ (f) and h ₂₂ (f) = ρ _a (Δx) h ₁₂ (f)) (dotted line shown in FIG. 3) Arrow) can be calculated. In other words, the calculation unit 106 does not actually measure channel estimation values [h ₂₁ (f) h ₂₂ (f)] between the transmission antennas # T1 and # T2 and the reception antenna # R2 illustrated in FIG. Obtainable. As a result, the MIMO evaluation apparatus 100 uses only one antenna 101 (evaluation antenna), and estimates channel values between 2 (= M) transmission antennas and 2 (= N) reception antennas. (2 × 2) channel matrix can be calculated.

  Then, the evaluation unit 107 evaluates reception characteristics (maximum throughput) using the bandwidth of the received signal, the SNR, and the channel matrix shown in Expression (1).

  As described above, the MIMO evaluation apparatus 100 receives signals transmitted from a plurality of M transmission antennas using one reception antenna. In other words, the MIMO evaluation apparatus 100 uses only one antenna 101, so that only the external environment (channel environment between transmission and reception) is used regardless of the arrangement of receiving antennas (distance between antennas or antenna orientation with respect to the transmitter). Can be estimated. In addition, the correlation matrix obtained by modeling (constantizing) the configuration of the receiving antenna is a matrix that does not depend on the channel environment between transmission and reception, but depends only on the receiving antenna.

  That is, as shown in Equation (1), MIMO evaluation apparatus 100 uses a channel matrix (M = N = 2 in Equation (1)) between M transmission antennas and N reception antennas as reception antennas. Calculation is performed using a correlation matrix that depends only on the configuration and a channel estimation value that depends only on the channel environment between transmission and reception. That is, MIMO evaluation apparatus 100 obtains the reception characteristics between M transmission antennas and N reception antennas by individually obtaining a correlation matrix that depends on the antenna configuration and a channel estimation value that depends on the channel environment. (Maximum throughput) can be evaluated. That is, the MIMO evaluation apparatus 100 can evaluate the reception characteristic (maximum throughput) indicating the MIMO performance regardless of the reception antenna configuration of the receiver.

  Further, since the channel estimation value estimated (measured) by the MIMO evaluation apparatus 100 does not depend on the arrangement of the receiving antennas, the channel estimation value estimation (measurement) is highly reproducible. Therefore, the MIMO evaluation apparatus 100 uses the channel estimation value that depends only on the channel environment between transmission and reception as it is, and only changes the definition of the correlation matrix of the reception antenna, so that the reception characteristics ( Maximum throughput). That is, the MIMO evaluation apparatus 100 can evaluate the reception characteristics (maximum throughput) of receivers having various reception antenna configurations without actually measuring channel estimation values for the receivers having various reception antenna configurations. .

  Thus, according to the present embodiment, it is possible to evaluate the reception characteristics at the receiver without depending on the arrangement of the antennas.

  Furthermore, according to the present embodiment, since the channel estimation value is estimated using only one antenna included in MIMO evaluation apparatus 100, a circuit (hardware resource) that performs reception characteristic evaluation processing is only for one antenna. It's okay. That is, in the MIMO evaluation apparatus having a plurality of reception antennas, a circuit for performing reception characteristic evaluation processing is required for the number of reception antennas, whereas in the MIMO evaluation apparatus according to the present embodiment, reception characteristic evaluation processing is performed. The circuit to be performed can be minimized. Thereby, the power consumption in the MIMO evaluation apparatus 100 can be suppressed, and further, the cost required for the MIMO evaluation apparatus 100 can be suppressed.

  In this embodiment, a case has been described in which a channel matrix is calculated using theoretical values assuming an ideal receiver (ideal receiver). However, the channel matrix may be actually measured in an actual receiver (practical receiver). Then, by comparing the maximum throughput obtained using the measured channel matrix and the maximum throughput obtained using the channel matrix calculated from the theoretical values, the amount of degradation in the practical receiver relative to the ideal receiver can be grasped. It becomes possible to do.

  In this embodiment, the case where a correlation matrix based on a Rayleigh distribution or an angular distribution is used as the correlation matrix of the reception antenna has been described. However, the correlation matrix of the reception antenna is not limited thereto. For example, the complex spatial correlation coefficient included in the correlation matrix of the receiving antenna may be obtained in advance by actual measurement.

  The MIMO evaluation apparatus and the MIMO evaluation method of the present invention are useful for evaluating reception characteristics at a receiver without depending on antenna arrangement.

DESCRIPTION OF SYMBOLS 100 MIMO evaluation apparatus 101 Antenna 102 Radio | wireless receiving part 103 Data calculating part 104 Information acquisition part 105 Data integration process part 106 Calculation part 107 Evaluation part 108 Integration part 109 Accumulation part 110 Display part

Claims (2)

A MIMO evaluation apparatus that evaluates reception characteristics of a receiver that receives signals transmitted from a transmitter having M transmission antennas by N reception antennas,
Receiving means for receiving the signals respectively transmitted from the M transmitting antennas by one evaluation antenna;
Estimating means for estimating M channel estimates between each of the M transmit antennas and the evaluation antenna based on received signals;
Calculating means for calculating a channel matrix between the M transmitting antennas and the N receiving antennas using the M channel estimation values and a correlation matrix of the N receiving antennas;
An evaluation means for evaluating the reception characteristics using the channel matrix;
A MIMO evaluation apparatus comprising: A MIMO evaluation method for evaluating reception characteristics of a receiver that receives signals transmitted from a transmitter having M transmission antennas by N reception antennas,
A reception step of receiving signals transmitted from the M transmission antennas by one evaluation antenna;
An estimation step for estimating M channel estimates between each of the M transmit antennas and the evaluation antenna based on a received signal;
A calculation step of calculating a channel matrix between the M transmission antennas and the N reception antennas using the M channel estimation values and a correlation matrix of the N reception antennas;
An evaluation step of evaluating the reception characteristics using the channel matrix;
A MIMO evaluation method comprising:

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