KR20050074884A - Apparatus and method for estimating noise and interference in communication system and apparatus and method for estimating cinr - Google Patents

Abstract

In an OFDM / OFDMA / DMT system according to the present invention, an apparatus for estimating power of an interference and noise signal includes a correlator for correlating and outputting a pilot sequence preset to a plurality of subcarriers for each element, and a plurality of subcarriers output from the correlator. An interference and noise calculating unit for calculating and outputting a difference between a correlation value for and a correlation value obtained from at least one adjacent subcarrier, and a sum of the difference of correlation values for each subcarrier from the interference and noise calculation unit; And an interference and noise power calculator for obtaining interference and noise power from the apparatus.

Description

Apparatus and method for estimating noise and interference in communication system and apparatus and method for estimating CINR}

The present invention provides a carrier to CINR (Carrier to measure) as a measure of reception performance in a wireless communication system based on orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDM). An apparatus and method for estimating noise and its CINR estimation apparatus and method for estimating interference and noise ratio) are provided.

Orthogonal frequency division multiplexing, which has recently been used as a useful method for high-speed data transmission in wired / wireless channels, is a method of transmitting data using a plurality of carriers, and converts serially input data in parallel and for each of them. It refers to a method of modulating and transmitting a plurality of sub-carriers having a mutual orthogonality, that is, a sub channel.

This orthogonal frequency division multiplexing is widely applied to digital transmission technologies such as digital / audio broadcasting, digital TV, wireless local area network (WLAN) or wireless asynchronous transfer mode (WATM). have. Although not widely used due to hardware complexity, various digital signal processing technologies including fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) have been recently realized. The orthogonal frequency division multiplexing scheme is similar to the conventional frequency division multiplexing (FDM) method, but most of all, it is possible to obtain optimal transmission efficiency in high-speed data transmission by maintaining orthogonality between a plurality of subcarriers. It is characterized by good frequency efficiency and strong resistance to multi-path fading. In addition, the orthogonal frequency division multiplexing scheme is strong in frequency selective fading by using overlapping frequency spectrum, and reduces the influence of intersymbol interference by using a guard interval, and it is possible to simply design the equalizer structure in hardware and impulse It has the advantage of being resistant to sex noise.

In such an OFDM system, a carrier to interference noise ratio (CINR), which is an essential parameter in power control or adaptive modulation and demodulation, needs to be measured.

Conventional technology includes a US patent "Method and apparatus for Signal to Noise Ratio (SNR) measurement (patent 6456653)". This patent discloses a method for estimating noise level in unused subcarriers. In an OFDM system, data to be sent by a transmitter is transmitted by performing fast inverse Fourier transform (IFFT). In this case, if the size of the IFFT is NFFT point, not all of them are used, but only Nused subcarriers are used and 0 is sent to the remaining Nunused subcarriers. This results in a mix of data and noise in the Nused subcarriers of the signals resulting from the fast Fourier transform of the receiver, and only noise in the remaining Nunused subcarriers. The patent measures the noise level from the remaining Nunused subcarriers and estimates the pure signal level by subtracting this noise level from the power level received from the Nused subcarriers assuming that the value is equal to the noise level intermingled with the data. do. As a result, the ratio of pure signal level to noise level is the SNR estimate.

However, in the conventional SNR estimation method, when the number of unused subcarriers (Nunused) is too small compared to the number of used subcarriers (Nused), there is severe degradation in estimation performance. In addition, since interference signals from other users who use the same band do not enter unused subcarriers, there is no way to estimate them.

Accordingly, it is an object of the present invention to provide a noise estimation apparatus and method and an apparatus and method for estimating a CINR, that is, a signal-to-interference and noise ratio, in an OFDMOFDMA / DMT system.

In order to achieve the above object, the present invention provides an apparatus for estimating power of an interference and noise signal, comprising: a correlator for correlating and outputting a pilot sequence preset to a plurality of subcarriers for each element, and a plurality of subcarriers output from the correlator; An interference and noise calculating unit for calculating and outputting a difference between a correlation value for and a correlation value obtained from at least one adjacent subcarrier, and a sum of the difference of correlation values for each subcarrier from the interference and noise calculation unit; And an interference and noise power calculation section for obtaining the noise power from.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a block diagram showing the configuration of a typical OFDM transmitter. Referring to FIG. 1, the OFDM transmitter 100 includes a pilot / preamble inserter 121, an IFFT unit 123, a parallel / serial converter 125, a guard interval inserter 127, an RF processor 131, and an antenna. 133.

The pilot / preamble inserter 121 generates pilot symbols and preambles set in a plurality of sub-channels and an orthogonal frequency division multiplexing communication system, and generates the generated pilot symbols in a plurality of subchannels, that is, data symbols. Insert it. Here, the reason for inserting and transmitting the pilot symbol together with the subchannel through which the data symbol is transmitted is for channel estimation, and the transmission position of the pilot subchannel in the orthogonal frequency division multiplexing communication system is pre-defined. In addition, the generated preamble is mainly located in front of the frame in the form of one OFDMA symbol. The pilot and preambles used in the preferred embodiment of the present invention use different sequences for each base station, and thus the more orthogonal the base stations, the more effective the performance of the present invention.

The inverse fast Fourier transformer (IFFT) 123 performs an inverse Fourier transform on the input subchannels and outputs the inverse Fourier transform to the parallel / serial converter 125. The parallel / serial converter 125 converts the input parallel signal into a serial signal and outputs it to the guard interval inserter 127. The guard interval inserter 127 inserts a guard interval for reducing the effects of inter-symbol interference (ISI) between subchannels output from the IFFT apparatus 123 and then the RF processor 131. Will output The RF processor 131 transmits the channel data received from the guard interval inserter 127 through the antenna 133 in a wireless channel.

2 is a block diagram showing the configuration of an OFDM receiver including a CINR estimator of the present invention. Referring to FIG. 2, the OFDM receiver 200 includes an antenna 211, an RF processor 213, a guard interval remover 215, a serial / parallel converter 217, an FFT unit 219, an equalizer 221, The channel estimator 223 and the channel quality information (hereinafter referred to as "CQI") estimator 225 are included.

The RF processor 213 outputs channel data to the guard interval remover 215 from the wireless channel received through the antenna 211. The guard interval remover 215 removes the guard interval from the received channel data. The serial / parallel converter 217 converts the serial data and the redundant data from which the guard interval has been removed into a plurality of parallel data and outputs the data to the fast Fourier transformer 219. The fast Fourier transformer 219 performs Fourier transform on the parallel data and the surplus data at high speed, and outputs the Fourier transformed data to the equalizer 221. The equalizer 221 removes the signal distortion due to the Fourier transformed information data and the channel of the surplus data, and outputs data from which the signal distortion is removed. The channel estimator 223 estimates the channel state according to the distortion of the phase and amplitude in the frequency domain due to the channel degradation occurring in transmission and reception, and compensates for the distortion of the phase amplitude in the frequency domain. The CQI estimator 225 measures channel quality, i.e., CINR.

As described above, in an OFDM system, a transmitter performs a fast Fourier Inverse Transform (IFFT), and then attaches a guard interval, and in contrast, the receiver first removes the guard interval and then performs a Fast Fourier Transform (FFT) and demodulates it. To get the transmitted signal.

According to the present invention, when an OFDM transmitter sends a digital signal of a known pattern called a pilot signal, the OFDM receiver which receives it estimates the CINR using the received signal. Specifically, the present invention uses a pilot signal after a fast Fourier transform to estimate the CINR. It is assumed that the pilot signal has a preset sequence and uses binary phase shift keying (BPSK) modulation for convenience. Suppose that the pilot sequence used here consists of '1' and '0'. The signal '1' is sent as a complex signal '1' and the signal '0' is sent as a complex signal '-1'.

3 is a block diagram illustrating a configuration of a CINR estimator according to the present invention.

The CINR estimator 400 receives the pilot signal output from the FFT 219 and outputs it to the signal power estimator 420 and the interference and noise power estimator 430. The signal power estimator 420 estimates the power of the received signal. In detail, the signal power estimator 420 obtains the power of each subcarrier of the signal received from the FFT unit 219, and then obtains the power of the signal by adding up the powers of the respective subcarriers and outputs the power of the signal to the subtractor 440.

In addition, the interference and noise power estimator 430 estimates the noise power of the received signal. The present invention estimates the noise power of a signal using the fact that subcarriers of a received signal have similar characteristics of a channel experienced by each adjacent subcarrier. That is, the present invention takes advantage of the difference from the adjacent carrier signal. In the embodiment of the present invention, the method includes: Difference of Adjacent Sub-carrier Signal; Let's call it the DASS method.

In detail, the interference and noise power estimator 430 correlates the pilot sequence preset to the plurality of subcarriers of the received signal for each element to obtain correlation values for the plurality of subcarriers. The interference and noise power estimator 430 then calculates the difference between the correlation value for each subcarrier and the correlation value obtained from at least one adjacent subcarrier. In this case, the number of adjacent subcarriers with similar channel characteristics may be arbitrarily determined. In general, adjacent subcarriers for each subcarrier may be immediately adjacent subcarriers. That is, the number of subcarriers may vary according to the characteristics of the communication system to which the present invention is applied. For example, to simplify the implementation of the system, only one subcarrier immediately adjacent to each subcarrier may be used. In addition, different numbers of adjacent subcarriers may be used for each subcarrier.

On the other hand, since adjacent subcarriers have almost the same channel characteristics, the difference between the correlation values cancels the signal components from each other and leaves the interference and noise components. The interference and noise power estimator 430 obtains the interference and noise signal power from each of these interference and noise components and outputs it to the subtractor 440. The subtractor 440 subtracts the noise power from the interference and noise power estimator 430 from the signal power from the signal power estimator 420 and obtains the power of the signal from which the interference and noise have been removed. The interference and noise signal power from the interference and noise power estimator 430 is then inversed in the inverse generator 450 and provided to the multiplier 460. The CINR estimate is calculated by the multiplier 460 dividing this total received power minus the total noise power by the total noise power. In other words, the ratio of the estimated value of the pure signal power and the estimated value of the interference and noise signal becomes the estimated CINR.

Meanwhile, there are three methods depending on which subcarrier signal of the pilot signal received according to the present invention is used to estimate the CINR, which will be described with reference to FIGS. 4A to 4C.

4A to 4C are diagrams for describing a CINR estimation method according to the first to third embodiments of the present invention, respectively. First, referring to FIG. 4A, a first embodiment of the present invention uses a pilot signal or a preamble signal composed of N subcarrier signals during one OFDM symbol period. As shown in FIG. 4A, a plurality of subcarriers exist in the same time domain in one OFDM symbol period. The first embodiment of the present invention takes advantage of the fact that subcarriers in the same time domain each have similar characteristics of a channel experienced by adjacent subcarriers. Accordingly, according to the first embodiment of the present invention, the CINR estimator 400 uses a plurality of subcarriers having the same time domain and different frequency domains in subcarriers of the pilot signal output from the FFT 219.

The second embodiment of the present invention uses a pilot signal or preamble signal composed of N subcarrier signals during a plurality of OFDM symbol periods. As shown in FIG. 4B, there are a plurality of subcarriers on the same frequency domain during a plurality of OFDM symbol periods. In a second embodiment of the present invention, a channel in which subcarriers on the same frequency domain suffer from each adjacent subcarrier is present. Take advantage of the fact that Accordingly, according to the second embodiment of the present invention, the CINR estimator 400 uses a plurality of subcarriers having the same frequency domain and different time domain in subcarriers of the pilot signal output from the FFT 219.

On the other hand, the third embodiment according to the present invention uses a pilot signal or preamble signal composed of N subcarrier signals in a predetermined data region including subcarriers of different frequency domains and different time domains from the received pilot signal. That is, as shown in FIG. 4C, in the third embodiment, a plurality of subcarrier signals to be used for estimating CINR in a predetermined data area are randomly selected. At this time, each subcarrier and its adjacent subcarriers are determined to have a correlation coefficient close to one. The third embodiment of the present invention takes advantage of the fact that subcarriers with close distances in a given data region have similar characteristics of channels experienced by adjacent subcarriers, respectively. Accordingly, according to the third embodiment of the present invention, the CINR estimator 400 uses sub-broadcast waves randomly selected in a predetermined data region consisting of subcarriers of the pilot signal output from the FFT unit 219.

Next, a detailed configuration and operation of the interference and noise power estimator 430 will be described with reference to FIG. 5.

5 is a block diagram of an interference and noise power estimator 430 according to an embodiment of the present invention. Referring to FIG. 5, an interference and noise power estimator 430 according to an embodiment of the present invention may include a pilot signal selector 510, a correlator 520, a signal noise calculator 530, and an interference and noise power calculator. 540. The pilot signal selector 510 selects a plurality of subcarrier signals to be used for estimating the CINR according to the first to third embodiments of the present invention. In the present embodiment, the pilot signal or the preamble is exemplified as a plurality of subcarrier signals for use in estimating the CINR, and the present invention is not limited thereto, and the reference signal is sufficient as a mutually regulated reference signal.

The pilot signal selector 510 selects a plurality of subcarriers having the same time domain and different frequency domains among subcarriers of the pilot signal or preamble received according to the first embodiment. The pilot signal selector 510 selects a plurality of subcarriers having the same frequency domain and different time domains among subcarriers of the pilot signal according to the second embodiment. The pilot signal selector 510 randomly selects a plurality of subcarriers in a predetermined data area including subcarriers of different frequency domains and different time domains from the received pilot signal according to the third embodiment. In this case, as described above, in the preferred embodiment of the present invention, each subcarrier and its adjacent subcarriers are determined to have a correlation coefficient close to 1, but are not limited thereto.

As described above, the pilot signal selector 510 selects a plurality of subcarrier signals to be used for estimating the CINR and outputs them to the correlator 520. The correlator 520 correlates the pilot sequence preset to the plurality of subcarriers from the pilot signal selector 510 for each element, obtains correlation values for the plurality of subcarriers, and outputs the correlation values to the signal noise calculator 530. The signal noise calculator 530 calculates a difference between a correlation value for the plurality of subcarriers output from the correlator 520 and a correlation value obtained from at least one adjacent subcarrier. In this case, the signal noise calculator 530 operates properly according to how many adjacent subcarriers are set for each subcarrier. As a result, the signal components cancel each other out and leave noise components. The noise component for each subcarrier obtained as described above is output to the interference and noise power calculator 540, and the interference and noise power calculator 540 squares the noise component for each subcarrier to obtain a noise signal power. Next, a noise power estimation method when the interference and noise power estimator 430 is implemented in software will be described with reference to FIG. 6.

6 is a control flowchart for estimating noise power according to an embodiment of the present invention. Referring to FIG. 6, the interference and noise power estimator 430 first selects a plurality of subcarrier signals to be used to estimate the CINR as described above in step 610. The interference and noise power estimator 430 proceeds to step 620 to correlate the pilot sequences preset to the plurality of subcarriers for each element. The interference and noise power estimator 430 then proceeds to step 630 to calculate the signal noise by calculating the difference between the correlation values for the plurality of subcarriers and the correlation values obtained from at least one adjacent subcarrier. The interference and noise power estimator 430 obtains the noise signal power from the noise component for each subcarrier in step 640. Next, a case of configuring a CINR estimator according to an embodiment of the present invention will be described with reference to FIG. 7.

7 is a diagram illustrating a configuration of a CINR estimator according to an embodiment of the present invention. The CINR estimator according to an embodiment of the present invention uses a pilot signal consisting of N subcarrier signals during one OFDM symbol period, and uses two immediately adjacent subcarriers as adjacent subcarriers for each subcarrier, but is not limited thereto. It is obvious to

As shown in FIG. 7, the CINR estimator 400 includes a signal power estimator 420 and an interference and noise power estimator 430. The interference and noise power estimator 430 receives N pilot signals from the N output terminals output from the FFT 219. In this embodiment, the interference and noise power estimator 430 does not need the pilot signal selector 510 of FIG. 5 since the N signals output from the FFT 219 are used as they are. However, the CINR estimator 400 may include a pilot signal selector for selecting a pilot signal according to the characteristics of the communication system to which the present invention is applied.

Let k k of the IFFT input of the transmitted signals be xk and k k of the FFT output of the received signals yk. In this case, assuming that the pilot signal uses binary phase shift keying (BPSK) modulation, xk = 1 or -1 (k = 1, 2, ..., N) is used for convenience. In addition, if the characteristics of the channel between xk and yk are Hk and the noise is nk, the received signal may be represented by Equation 1.

Since x _k is a preset pilot sequence, the receiver knows the value, and y _k is a value obtained from the measurement.

The CINR we want to estimate is defined as in Equation 2. In Equation 2, the numerator is the sum of the powers of the pure received signals excluding noise and the denominator is the sum of the powers of the noise signals.

In this embodiment, in order to separate the noise component from the received signals, a value of Fk is defined as in Equation 3. This value is the intermediate value of the calculation used to estimate the noise component.

Specifically, as shown in FIG. 7, the N multipliers 310-1 to 310 -N multiply the N outputs from the FFT 219 by the transmitted signals, that is, the preset sequences. Accordingly, the same condition may be applied when the transmitting side transmits 1 and -1. These N multipliers 310-1 to 310 -N correspond to the correlators 520 of FIG. 5.

Outputs from the N multipliers 310-1 to 310-N are positively input to the N adders 320-1 to 320-N, respectively, and to the N adders 320-1 to 320-N. The outputs from the N multipliers 310-1 through 310-N for adjacent subcarriers are negatively input.

Accordingly, the outputs from the N adders 320-1 to 320-N are the difference between the values obtained in the respective subcarriers and the values obtained in the adjacent subcarriers, thereby canceling the signal components and leaving only the noise components. These N adders 320-1 to 320-N correspond to the signal noise calculator 530 of FIG.

As shown in FIG. 7, y1, the first signal of N signals, has one adjacent signal y2, and yN, the last signal has one adjacent signal yN-1. The remaining signals are two adjacent signals. For example, the yk signal has two adjacent signals, yk-1 and yk + 1. Therefore, the first signal y1 and the last signal yN of the N signals are subtracted from the value of the signal transmitted to the output of the adjacent subcarrier from the value of the signal transmitted to the output of each subcarrier. The remaining signals, eg, yk, double the value obtained by multiplying the transmitted signals by the outputs of the subcarriers, and subtract the value obtained by multiplying the outputs of the two adjacent subcarriers by each transmitted signal.

As a result, the result of F1 ~ FN cancels the signal component and leaves only the noise component.

Equation 1 is substituted into y values of each of F1 to FN, and the equations 1 are expanded to separately collect components by signals and components by noise.

In Equation 4, terms before the parenthesis are components due to signals, and values in parentheses are components due to noise. In addition, assuming that adjacent subcarrier channels have almost the same channel characteristics, it can be expressed as in Equation 5.

Then, in Equation 4, the values before the parentheses become 0, so that the signal component is canceled and only the noise component remains. This noise component is squared for substitution into equation (2) to estimate the noise signal power. That is, when the parenthesis, which is a component of noise, is squared in Equation 4, the power of Fk is expressed by Equation 6 below.

Where | F _k | ^In order to calculate the sum of ² , K _k is defined as Equation 7 for convenience.

Substituting such Equation 7 into F _k ² of Equation 6 provides Equation 8 below.

The sum of the second term, Kk, is close to zero. Because the pilot sequence is a PN sequence, since 1 and -1 have similar distributions, and each noise component has an average value of 0 and independent of each other, it becomes as shown in Equation (9).

In other words, it is expressed as Equation 10.

Therefore, F1 for the first signal, y1, and FN for the last signal, yN, have two noise components, so they are squared and divided by two, and the noise components Fk for the remaining signals are four | n _k | ² , 1 | n _k-1 | ² and 1 | n _{k + 1} | ^{Since we have 2} , we square and divide by 6. This is done by the N computing devices 330-1 through 330-N in FIG. The total noise power is added by the adder 340 and becomes as shown in Equation (11).

In this case, the values in the parentheses of Equation 11 and the following terms are very small values compared to the total value of Equation 11, and thus can be ignored.

In this case, the first and second terms of Equation 12 may also be omitted.

Finally, the power of the signal becomes as shown in equation (13).

Y ₁ | ² to | y _N | Subtracting the total noise power from the sum of the ^two gives the power of the signal with the interference and noise removed. Accordingly, the N computing devices 330-1 to 330 -N and the adders 340 correspond to the noise power calculator 540 of FIG. 5.

In addition, as shown in FIG. 7, the output signal from the FFT unit 219 is calculated by the square operators 360-1 to 360 -N, respectively. The outputs of the square operators 360-1 to 360 -N are added to the adder 370 to obtain the power of the entire received signal. Therefore, the square operators 360-1 through 360 -N and the adder 370 correspond to the signal power estimator 420 of FIG. 3.

Subtractor 440 subtracts the total interference and noise power from the power of this total received signal, as shown in equation (13). Since the last term in Equation 13 is negligible, we will approximate the total received power by subtracting the power of noise. As a result, an estimate of the CINR can be obtained as shown in Equation 14.

The total received power minus the total noise power is divided by the total noise power in the multiplier 460 and the CINR estimate is calculated.

Meanwhile, one embodiment of the above-described CINR estimator of the present invention uses two immediately adjacent subcarriers for each subcarrier as adjacent subcarriers. In general, when using W subcarriers, Equation 3 is represented by the general formula. If the following equation (15).

Accordingly, Equation 12 for obtaining the noise power is expressed as Equation 16 below.

As described above, the performance of the CINR estimator to which the present invention is applied is shown in FIGS. 8 and 9. 8 shows the performance of the CINR estimator to which the present invention is applied in an AWGN environment, and FIG. 9 shows the average performance of the CINR estimator to which the present invention is applied in a channel model environment of an International Telecommunication Union Radiocommunication Sector (ITU-R). Interference from other transmitters will be modeled as Additive White Gaussian Noise (AWGN). This is because the Central Limit Theorem shows that the sum of a large number of random variables, i.e., interference signals from other transmitters, follows the Gaussian distribution.

The simulation environment uses a 2048 FFT with a bandwidth of 10 MHz and a pilot sequence length of 776. The mean, maximum, minimum, and standard deviation of the 1000 estimates are shown, respectively. As shown in FIG. 8 and FIG. 9, it can be seen that the estimated CINR value and the actual CINR value almost coincide with the present invention.

In the foregoing description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. In addition, the present invention described above has been described as being applied to an OFDM system, but may also be applied to an OFDMA system and Discrete Multitone Technology (DMT).

Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the equivalent of claims and claims.

The present invention can accurately estimate a carrier to interference noise ratio (CINR), which is an essential parameter in power control, adaptive modulation and demodulation, etc. in an OFDM receiver.

1 is a block diagram showing the configuration of a typical OFDM transmitter;

2 is a block diagram showing the configuration of an OFDM receiver including a CINR estimator of the present invention;

3 is a block diagram illustrating a configuration of a CINR estimator according to the present invention;

4A to 4C are diagrams for describing a CINR estimation method according to the first to third embodiments of the present invention, respectively;

5 is a block diagram of an interference and noise power estimator 430 according to an embodiment of the present invention;

6 is a control flowchart for estimating interference and noise power according to an embodiment of the present invention;

7 is a diagram illustrating a configuration of a CINR estimator according to an embodiment of the present invention;

8 is a diagram showing the performance of the CINR estimator to which the present invention is applied in the AWGN environment,

9 is a view showing the average performance of the CINR estimator to which the present invention is applied in the channel model environment of the ITU-R.

Claims (17)

An apparatus for estimating the power of a noise signal of a communication system, A correlator for correlating and outputting, for each element, a reference sequence preset to a plurality of subcarriers; A signal noise calculator for calculating and outputting a difference between correlation values of the plurality of subcarriers output from the correlator and correlation values obtained from at least one adjacent subcarrier; And a noise power calculator for obtaining a noise power from a difference between correlation values for each subcarrier from the signal noise calculator. The noise power estimation apparatus of claim 1, further comprising a pilot signal selector configured to select and output a plurality of subcarrier signals to be used to estimate carrier to interference noise ratio (CINR). The noise power estimation apparatus of claim 2, wherein the pilot signal selector selects a plurality of subcarriers having the same time domain and different frequency domains among the subcarriers of the received pilot or preamble signal. The noise power estimation apparatus of claim 2, wherein the pilot signal selector selects a plurality of subcarriers having the same frequency domain and different time domains from the subcarriers of the received pilot or preamble signal. The noise power estimation apparatus of claim 2, wherein the pilot signal selector randomly selects a plurality of subcarriers in a predetermined data region including subcarriers of different frequency domains and different time domains from received pilot or preamble signals. . 6. The apparatus of claim 5, wherein the plurality of subcarriers are selected to have a high correlation coefficient with adjacent subcarriers. 6. The apparatus of claim 5, wherein the plurality of subcarrier signals are orthogonal frequency division multiple access (OFDMA) signals. The noise power estimation apparatus of claim 5, wherein the plurality of subcarrier signals are orthogonal frequency division multiplexing (OFDM) signals. The noise power estimation apparatus of claim 5, wherein the plurality of subcarrier signals are discrete multitone technology (DMT) signals. In a method for estimating the power of a noise signal in a communication system, Correlating, by element, a reference sequence preset to a plurality of subcarriers received; Calculating a difference between correlation values of the plurality of subcarriers and correlation values obtained from at least one adjacent subcarrier; Obtaining a noise power from a difference of correlation values for each subcarrier. 12. The method of claim 10, further comprising selecting a plurality of subcarriers having the same time domain and different frequency domains among the subcarriers of the received pilot or preamble signal. 12. The method of claim 11, wherein a plurality of subcarriers having the same frequency domain and different time domain are selected from the subcarriers of the received pilot or preamble signal. 12. The method of claim 11, wherein a plurality of subcarriers are randomly selected from a received data region including subcarriers of different frequency domains and different time domains from the received pilot or preamble signal. 15. The method of claim 13, wherein the plurality of subcarriers are selected to have a high correlation coefficient with adjacent subcarriers. A signal power estimator for measuring the total power of the signal from the FFT processed signal; A correlation value of a plurality of subcarriers is obtained by correlating an FFT-processed signal with a preset sequence for each element by using a DIF (Difference of Adjacent Sub-carrier Signal) method, and the correlation value for each subcarrier and at least one or more angles. An estimator for calculating a difference between correlation values obtained from adjacent subcarriers and estimating interference and noise power; A CINR estimator for estimating the ratio of the estimated power of the pure signal and the ratio of the estimated value of the interference and noise signal (CINR) using the signal power value output from the signal power estimator and the noise value output from the interference and noise power estimator Device. Measuring the total power of the signal from the FFT processed signal, Obtaining a correlation value for a plurality of subcarriers by correlating the FFT-processed signal with a preset sequence for each element using a DIF (Difference of Adjacent Sub-carrier Signal) method; Estimating a difference between a correlation value for each subcarrier and a correlation value obtained from at least one adjacent subcarrier, and estimating interference and noise power; Estimating a ratio (CINR) of the estimated power of the pure signal and the estimated value of the interference and noise signal using the signal power value output from the signal power estimator and the noise value output from the interference and noise power estimator. CINR estimation method, characterized in that. In the noise signal estimated from the received plurality of subcarriers, The subcarriers of the received signal are calculated based on the similarity of the characteristics of the channels experienced by the adjacent subcarriers, and the difference between the at least one neighboring subcarrier signals is calculated, and the noise is estimated to be only a noise component from which the signal components are removed. signal.