JP5099124B2 - Wireless communication quality estimation method and apparatus - Google Patents

Description

  The present invention relates to a radio communication quality estimation method and apparatus, and more particularly to a method and apparatus for estimating radio communication quality between a radio communication terminal or radio communication base station and an opposing base station or terminal. .

  A conventionally known wireless communication quality estimation method and apparatus will be described below with reference to FIG. 3 and FIG. Here, as an example, description will be made based on OFDM (Orthogonal Frequency Division Multiple Access) technology.

  First, as a system for estimating wireless communication quality, consider a system including a wireless communication terminal 1, a desired base station 2, and an interference base station 3, as shown in FIG.

Assuming that frame synchronization of the radio communication signal is normally established, a downlink signal model at the k-th frequency point f _k after FFT (Fast Fourier Transform) is defined as the following equation (1).

Here, y (f _k ) is a received signal after FFT at terminal 1, x (f _k ) is a known signal (preamble) sent from desired base station 2 to terminal 1 (BPSK: ± 1), v ( f _k ) is a known signal (BPSK: ± 1) sent from the interfering base station 3 to the terminal 1, h (f _k ) is the propagation path response from the desired base station 2 to the terminal 1, and u (f _k ) is the interference The propagation path response from the base station 3 to the terminal 1, n (f _k ) represents the thermal noise on the terminal 1 side. Note that x (f _k ) and v (f _k ) are assumed to be known signals with low auto-correlation and cross-correlation.

を用いて等価的に表している。At this time, according to the conventional method, the wireless communication quality CINR (Carrier to Interference and Noise Ratio) _conv is _calculated from the following equation (2) as an estimate of the channel response h (f _k ).

Equivalently expressed using

はh(f_k)の推定値である。here

Is an estimate of h (f _k ).

を演算して出力する。この推定値

は電力計算部130及び140に送られる。That is, as shown in FIG. 4, in the terminal 1, the received signal y (t) is subjected to an FFT calculation by the FFT calculation unit 110 and converted into a frequency domain received signal y (f _k ), and then the received signal y (f _k ), The channel estimation unit 120 estimates the channel response h (f _k )

Is calculated and output. This estimate

Is sent to the power calculators 130 and 140.

と既知信号発生部150から発生された既知信号x(f_k)とを乗算し、その二乗和を計算することによりチャネル推定値

を用いた所望信号の電力

を求める。電力計算部140では、推定値

と既知信号x(f_k)と受信信号y(f_k)とで端末1側の干渉信号及び雑音の電力

を求める。In power calculator 130, the channel estimation value

Is multiplied by the known signal x (f _k ) generated from the known signal generator 150, and the sum of squares thereof is calculated.

Power of desired signal using

Ask for. In the power calculator 140, the estimated value

And the known signal x (f _k ) and the received signal y (f _k ), the interference signal and noise power on the terminal 1 side

Ask for.

Then, the calculation unit 160 obtains the wireless communication quality CINR _conv according to the above equation (2) using the calculated values of the power calculation units 130 and 140 as the numerator and denominator, respectively.

  A correlator for outputting a predetermined pilot sequence correlated to a plurality of subcarriers for each element, a correlation value for a plurality of subcarriers output from the correlator, and a correlation value obtained from at least one adjacent subcarrier. A signal noise calculation unit that calculates and outputs a difference between the signal noise calculation unit and an interference and noise power calculation unit that obtains interference and noise power from a difference between correlation values for the subcarriers from the signal noise calculation unit There is an interference and noise estimation apparatus and method therefor (see, for example, Patent Document 1).

In this Patent Document 1, a CINR estimated value is obtained by a calculation formula of wireless communication quality CINR = (received signal power−interference noise power) / interference noise power.
JP 2005-204307 A

の一番簡単な求め方は、

であるが、この場合、当該

を式(2)に代入すると下記の式(3)に示すように分母が“0”になるため、CINR_convは無限大となってしまい、正しい値を求めることができない。Estimated value above

The easiest way to find is

In this case,

When is substituted into equation (2), the denominator becomes “0” as shown in equation (3) below, so CINR _conv becomes infinite and a correct value cannot be obtained.

So the estimated value

Determination of changes the propagation path responses before and after the sub-carriers _{f k (h (f k-} 1); h (f k); h (f k + 1), u (f k-1); u ( Taking advantage of the fact that f _k ); u (f _{k + 1} )) has almost no frequency selectivity, an estimation method defined by the following equation (4) is used.

  Substituting Equation (1) and Equation (4) into Equation (2) yields Equation (5) below.

  On the other hand, ideal wireless communication quality information is defined by the following equation (6).

Here, P _SOI , P _SNOI , and P _n are expressed by the following formula (7).

Note that since the cross-correlation between u (f _k ) v (f _k ) and n (f _k ) in equation (6) is low, the multiplication value of both is ignored.

As described above, since x (f _k ) and v (f _k ) are assumed to be known signals with low autocorrelation and cross-correlation, the first term in the denominator of equation (5) is the above equation (7). If is used, the relationship of the following formula (8) is obtained.

  In addition, the second term in the denominator of equation (5) is the addition of Gaussian distribution, so if equation (7) is used, there is a relationship of equation (9) below.

  Further, the second term in the numerator of the formula (5) has the relationship of the following formula (10) when the formula (7) is used.

  In addition, the third term in the numerator of equation (5) is the addition of Gaussian distribution, so if equation (7) is used, there is a relationship of equation (11) below.

  From the above equations (8) and (9), the range that the denominator of equation (5) can take is given by the following equation (12).

  Further, from the formulas (10) and (11), the range that the numerator of the formula (5) can take is given by the following formula (13).

From the above equations (12) and (13), the wireless communication quality CINR _conv obtained by the conventional method takes values different from the ideal denominator and numerator of equation (6). Furthermore, the expression (13) includes unnecessary P _SNOI and P _n components, and there is a problem that an error from an ideal value becomes large.

  Here, the propagation path response is obtained as an average value with three subcarriers, but the same problem as described above occurs even in cases other than three.

  Accordingly, an object of the present invention is to provide a method and apparatus that can estimate a radio communication quality (CINR) as close to an ideal value as possible.

In order to achieve the above object, a wireless communication quality estimation method (or apparatus) according to the present invention includes a first step (or means) for obtaining a first power indicating the power of a received desired signal, and a received interference signal. A second step (or means) for obtaining a second power indicating the sum of the power of the noise and the noise power, and a third step (or means) for obtaining the wireless communication quality from the ratio of the first power and the second power. And the first step (or means) obtains the first power based on a product of conjugate complex numbers of ratios of received signals and known signals in two adjacent subcarriers (or And the second step (or means) includes the step (or means) of determining the second power based on the received signal, the known signal, and a channel estimate for the received signal. Features.

That is, in the conventional method represented by the formula (5), the numerator of the formula (5) includes unnecessary P _SNOI and P _n, so in the present invention, in two adjacent subcarriers. since obtaining a first power indicating a power of the desired signal received on the basis of the received signal and the complex conjugate product between the ratio of the known signal, it is removed the component of P _SNOI and P _n becomes Rukoto formula (6 It is possible to make the value (desired signal power) close to the numerator of the ideal wireless communication quality information represented by ().
Then, since the second power is obtained based on the received signal, the known signal, and the channel estimation value for the received signal, the ratio of the first power to the second power is expressed by Equation (6). Ideal wireless communication quality can be obtained.

Further, since only the P _SNOI and P _{n to} be obtained are included with respect to the denominator of the equation (5) , the second variable may be multiplied by a scalar variable. By multiplying by the scalar variable, it is possible to make the value close to the ideal denominator of the wireless communication quality information expressed by Equation (6).

  The second step includes a step of obtaining a power ratio between the known signal portion and the data portion in the received signal, a step of obtaining an average received power of a guard band in the received signal, and the power ratio and Determining the second power using the average received power.

That is, the P _SNOI and P _n components can be corrected in consideration of the case where the known signal portion in the received signal is larger than the data portion.

Incidentally, it is preferable sufficiently large to correspond to the number of when the F FT samples were determined assuming white Gaussian noise.

  The present invention increases the accuracy of wireless communication quality information. As a result, adaptive modulation / coding can be performed without error. Therefore, not only the throughput of the system can be increased by reducing the number of overheads such as retransmission requests, but also the processing delay can be suppressed, and thus an efficient system can be constructed.

Example [1]
In the embodiment [1] of the present invention, first, the denominator (interference signal + noise power) of the radio communication quality CINR is multiplied by the scalar variable α by the denominator of the equation (2) as in the following equation (14).

は、

の範囲の値をとるので、平均的に

に近い値になる。従って、αとしては9/8から3/2の間

を取ればよい。 From equation (12)

Is

Take a value in the range of

A value close to. Therefore, α is between 9/8 and 3/2

Just take it.

  In addition, for the numerator (carrier (desired signal) power) of wireless communication quality CINR, an estimated value defined by the following equation (15) is used instead of the numerator of equation (2).

  The reason why two adjacent subcarriers are used in the above equation (15) is to suppress radio waves from other base stations, but there is almost no frequency selectivity between adjacent subcarriers as described above. As a result, the product of conjugate complex numbers is substantially obtained with the same subcarrier.

と定義すると、

は下記の式(16)式で与えられる。here,

Defined as

Is given by the following equation (16).

は下記の式(17)で与えられる。From equation (16) above,

Is given by equation (17) below.

As mentioned above, x (f _k ) and v (f _k ) have low autocorrelation and cross-correlation, and n (f _k ) assumes white Gaussian noise, so there are enough sample points for k. Then, the second to fourth terms on the right side of the above equation (17) are substantially equal to “0”, and thus equation (15) approaches the value of equation (18) below.

Since this equation (18) is equivalent to the P _SOI of the above equation (7), the ideal CINR _ideal of the equation (6) is expressed by the following equation (19) in the equations (14) and (15). It can be seen that it can be realized as follows.

That is, in the wireless communication quality estimation method and apparatus according to the present invention shown in FIG. 1, the power calculation unit 13 uses the received signal y (f _k ) and the known signal x (f _k ) to obtain the desired value according to the equation (15). While calculating the power of the signal, the power calculation unit 14 multiplies the interference signal + noise power according to the equation (14) by the scalar variable α.

Ask for. Then, the CINR _prp of the present invention according to the equation (19) is obtained by using the power obtained by the power calculating units 13 and 14 as the numerator and denominator, respectively.
・ Computer simulation results
The method of this embodiment is evaluated by computer simulation with reference to the IEEE standard 802.16-2004 system. The simulation parameters are shown in Table 1 below.

  When the FFT size is 1024, the number of known signals inserted (subcarrier number k) is 284.

  Further, the conventional method and the present invention method are specifically defined by the equations (20) and (21), respectively.

とする。また、式(21)の分母における“282”はチャネル推定値

がサブキャリアの端の値を取れないため、“1”だけ少なくなっている。In the above equations (20) and (21), the propagation path estimation value is from equation (4),

And In addition, “282” in the denominator of Equation (21) is the channel estimation value.

However, since the value at the end of the subcarrier cannot be taken, it is decreased by “1”.

The simulation results based on the above equations (20) and (21) are shown in FIGS. 2 (2) and (1). The horizontal axis is the absolute value display [db] of the error from the ideal value CINR _ideal, and the vertical axis is the CDF (cumulative density function: probability). That is, the simulation result of FIG. 2 shows that the wireless communication quality CINR calculated using the equations (6), (19), and (20) from the reception signal y (f) discretely given to the terminal 1 respectively. The accuracy (error from ideal radio communication quality CINR _ideal ) is shown.

Scenarios 1 to 6 change the parameters (known signals x, v, thermal noise n on the terminal side, and propagation path responses h, u from the desired base station and the interference base station) by changing the equation (6). The ideal radio communication quality CINR _ideal corresponds to an assumed system with an average of 2, 8, 14, 20, 25, and 25 [dB], respectively.

It can be confirmed that the method of the present invention shown in (1) has a higher probability of being close to the ideal wireless communication quality CINR _ideal and has better characteristics than the conventional method shown in (2).

Example [2]
In the above embodiment [1], the known signal (preamble) in the received signal frame is assumed to be the data part and the wireless communication quality CINR is obtained. In practice, however, the known signal part is better than the data part. The power may be large, and in this embodiment [2], an offset is applied to this.

That is, when the power ratio β between the known signal portion and the data portion is given by the following equation (22) (when β ≧ 1), the present invention sets the CINR _prp of the above equation (21) to the following equation (23): Can be calculated with

はP_nの推定値である。具体的にはガードバンドの平均受信電力を求めることで計算できる。here,

Is an estimate of P _n . Specifically, it can be calculated by obtaining the average received power of the guard band.

を加えればよいが、同第一項にはP_nが含まれているので、

としている。In the above equation (23), in the denominator, the noise power component is expressed in the same first term as above.

But the first term contains P _n, so

It is said.

  It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that various modifications can be made by those skilled in the art based on the description of the scope of claims.

It is the block diagram which showed the structural example of the estimation method and apparatus of the radio | wireless communication quality which concerns on this invention. It is the graph which showed radio | wireless communication quality CINR by the computer simulation of this invention and a prior art example. It is the block diagram which showed the general radio | wireless communication system common to this invention and a prior art example. It is the block diagram which showed the example of a structure of the estimation method and apparatus of the radio | wireless communication quality by a prior art example.

Explanation of symbols

1 terminal
2 Desired base station
3 Interfering base station
11 FFT calculator
12 channel estimation unit
13, 14 Power calculator
15 Known signal generator
16 CINR calculator In the figure, the same reference numerals indicate the same or corresponding parts.

Claims (8)

A first step of determining a first power indicating the power of the received desired signal;
A second step of obtaining a second power indicative of a sum of the received interference signal power and noise power;
A third step of obtaining a wireless communication quality from a ratio between the first power and the second power;
The first step includes determining the first power based on a product of conjugate complex numbers of ratios of received signals and known signals in two adjacent subcarriers, and the second step comprises: A wireless communication quality estimation method comprising: calculating the second power based on the received signal, the known signal, and a channel estimation value for the received signal. In claim 1,
The wireless communication quality estimation method, wherein the second step includes a step of multiplying the second power by a predetermined scalar variable. In claim 1,
The second step includes a step of obtaining a power ratio between the portion of the known signal and the data portion of the received signal, a step of obtaining an average received power of a guard band in the received signal, and the power ratio and the average reception And determining the second power using power. A wireless communication quality estimation method comprising: In claim 1,
A wireless communication quality estimation method characterized in that the number of F FT samples is sufficiently large corresponding to the number when white Gaussian noise is assumed. First means for obtaining a first power indicative of the power of the received desired signal;
A second means for obtaining a second power indicating a sum of the power of the received interference signal and the noise power;
A third means for obtaining a wireless communication quality from a ratio between the first power and the second power;
The first means includes means for determining the first power based on a product of conjugate complex numbers of ratios of received signals and known signals in two adjacent subcarriers, and the second means comprises: wireless communication quality estimation apparatus, wherein the including that the means for determining the power of the second based on the channel estimates for the received signal and said known signal and the received signal. In claim 5,
The wireless communication quality estimating apparatus, wherein the second means includes means for multiplying the second power by a predetermined scalar variable. In claim 5,
The second means comprises means for determining a power ratio between the portion of the known signal and the data portion of the received signal; means for determining an average received power of a guard band in the received signal; and the power ratio and the average reception A wireless communication quality estimation apparatus comprising: means for obtaining the second power using power. In claim 5,
A wireless communication quality estimation apparatus characterized in that the number of F FT samples is sufficiently large to correspond to the number when white Gaussian noise is assumed.

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