CN101800721B - Method and device for estimating interference in orthogonal frequency division multiplexing communication system - Google Patents

Abstract

The embodiment of the invention relates to a method and a device for estimating interference in an orthogonal frequency division multiplexing communication system. The method mainly comprises the following steps that: data output by a decoder is encoded, interwoven, modulated and processed, and a modulation symbol estimation value is obtained and transmitted to an interference estimator. The interference estimator estimates the interference through a plurality of times of iterative processing according to a received modulation symbol sequence, the modulation symbol estimation value and a channel estimation result, and obtains the interference estimation results of all subcarriers in an OFDM symbol. By adopting the processing process of iterative algorithm in interference estimation, the embodiment of the invention greatly improves the interference estimation precision, so as to lead an OFDM communication system to obtain nearly the best system performance.

Description

Method and device for interference estimation in OFDM communication system

technical field

The present invention relates to the technical field of wireless communication, in particular to a method and device for interference estimation in an OFDM (orthogonal frequency division multiplexing, orthogonal frequency division multiplexing) communication system.

Background technique

In recent years, people have higher and higher requirements for communication quality and more and more services that communication networks can provide. With the continuous development of communication requirements, the spectrum resources available for communication have become increasingly scarce. Most of the Frequency resources have been fixedly allocated, so the new wireless communication system will face the problem of co-existing and sharing frequency spectrum with the existing wireless communication system. For example, wireless LAN and Bluetooth share the 2.4G frequency band. On the other hand, the research results show that the spectrum utilization rate is not high, and the spectrum utilization rate fluctuates greatly in the same area. In order to solve the contradiction between the shortage of spectrum resources and the low utilization rate, people have proposed cognitive radio technology. In a communication system based on cognitive radio technology, communication equipment can detect the surrounding wireless electromagnetic environment and make adaptive adjustments to perform frequency multiplexing in different time and space, which greatly improves the efficiency of spectrum utilization.

OFDM is a communication modulation and multiplexing technology widely used in wireless and wired communication systems, and it can effectively combat frequency selective fading. In the wireless communication of spectrum coexistence and sharing, OFDM wireless communication is vulnerable to colored interference from other wireless communication systems, and the receiver based on the maximum likelihood criterion can effectively suppress the colored interference when the location and power of the interference are known.

A schematic structural diagram of an OFDM communication system using cognitive radio technology is shown in Figure 1. There is rapidly changing narrowband interference in the channel of the OFDM communication system. The signal transmission process of the OFDM communication system is as follows:

In order to reduce the bit error rate during signal transmission, the OFDM transmitter channels the original signal to be transmitted through an encoder. In order to reduce the impact of burst errors, the signal output by the encoder is sent to the interleaver for interleaving processing, and then output to the modulator. The modulator outputs modulation symbols, and then undergoes serial-to-parallel conversion, IFFT (Inverse Fast Fourier Transform, inverse Fast Fourier Transform) conversion and parallel-to-serial conversion to obtain OFDM time-domain symbols, which are passed through OFDM after adding a cyclic prefix to the OFDM time-domain symbols. The transmitter fires out.

After receiving the OFDM communication signal transmitted by the OFDM transmitter, the OFDM receiver performs synchronization on the OFDM communication signal and removes the cyclic prefix to obtain OFDM time domain symbols. Then, the above OFDM time-domain symbols are converted through serial-to-parallel conversion, FFT (Fast Fourier Transform, fast Fourier transform) conversion and parallel-to-serial conversion to obtain modulation symbol sequences, which are subjected to fading channels, colored interference and Gaussian white noise Impact. At the same time, the channel estimation module of the OFDM receiver outputs the channel estimation of the current channel. The data detection module of the OFDM receiver detects the original signal received by the OFDM transmitter according to the modulation symbol sequence and channel estimation information.

A scheme for estimating the location and power of the interference of the receiver in the prior art is: using a sliding window average algorithm to estimate the location and power of the interference. The processing flow of this scheme is shown in Figure 2, specifically The processing process is as follows: first, judge the modulation symbol for the input received signal, and then subtract the received signal and the judged modulation symbol for each modulation symbol to obtain an error signal, find the square of the modulus of the error signal, and then perform frequency domain Filtering, frequency domain filtering adopts the sliding window averaging method with a set length, and finally obtains the position and power information of the interference.

In the process of realizing the present invention, the inventors found that the above-mentioned scheme for estimating the position and power of the interference of the receiver has at least the following problems: the estimation accuracy of the interference is not high, and the main reason is that the bit error rate of the modulation symbol judgment is relatively high; Larger sliding window length. This scheme can only be applied to occasions where the interference power has a large correlation in the frequency domain and the time domain, it is difficult to adapt to the situation of narrowband interference and rapid changes in interference, and it cannot meet the requirements of OFDM wireless communication systems based on cognitive radio technology to combat colored interference. requirements.

Contents of the invention

Embodiments of the present invention provide a method and device for estimating interference in an OFDM communication system, so as to solve the problem of low interference estimation accuracy in existing solutions and cannot be applied to OFDM wireless communication based on cognitive radio technology system problem.

A device for interference estimation in an OFDM communication system, comprising:

The interference estimator is used to perform interference estimation through iterative processing according to the received modulation symbol sequence, modulation symbol estimation value and channel estimation result, and obtain the interference estimation result of each subcarrier in the OFDM symbol, the modulation The estimated value of the symbol is obtained by encoding, interleaving and modulating the data output by the decoder;

The demodulator is configured to perform soft demodulation processing to obtain each coded bit in the OFDM symbol according to the received modulation symbol sequence, the channel estimation result and the interference estimation result transmitted by the interference estimator measure value;

A deinterleaver, configured to perform deinterleaving processing according to the metric value of each coded bit in the OFDM symbols transmitted by the demodulator, to obtain data symbols;

The decoder is configured to perform decoding processing on the data symbols output by the deinterleaver, and obtain decoded data.

A method for interference estimation in an OFDM communication system, comprising:

According to the received modulation symbol sequence, modulation symbol estimation value and channel estimation result, perform interference estimation through iterative processing, obtain the interference estimation result of each subcarrier in the OFDM symbol, and then according to the interference estimation result, modulation The symbol sequence and channel estimation results are processed by soft demodulation to obtain the metric value of each coded bit in the OFDM symbol;

Perform deinterleaving processing according to the metric value of each coded bit in the OFDM symbol, perform decoding processing on the data symbols output after the deinterleaving processing, and obtain decoded data, and the modulated The symbol estimation value is obtained by encoding, interleaving and modulating the decoded data.

It can be seen from the technical solutions provided by the above embodiments of the present invention that the embodiment of the present invention greatly improves the estimation accuracy of interference by adopting the iterative algorithm processing process in the interference estimation, so that the OFDM communication system obtains approximately optimal system performance.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of an OFDM communication system using cognitive radio technology in the prior art;

Fig. 2 is a flow chart of the processing procedure of a scheme for estimating the position and power of the interference of the receiver in the prior art;

FIG. 3 is a schematic structural diagram of a device for joint interference estimation and encoding and decoding proposed by Embodiment 1 of the present invention;

FIG. 4 is a processing flowchart of a method for estimating interference in an OFDM communication system according to Embodiment 4 of the present invention;

FIG. 5 is a schematic diagram of the performance of the interference estimation method proposed in the embodiment of the present invention, and a schematic diagram of simulation results under different interference intensities.

Detailed ways

In the embodiment of the present invention, the interference estimator performs interference estimation through multiple iterative processing according to the received modulation symbol sequence, modulation symbol estimation value and channel estimation result, obtains the interference estimation result of each subcarrier in the OFDM symbol, and converts the obtained The above interference estimation result is transmitted to the demodulator. The demodulator performs soft demodulation processing according to the received modulation symbol sequence, the channel estimation result and the interference estimation result transmitted by the interference estimator to obtain the metric value of each coded bit in the OFDM symbol , and transmit the metric value of each coded bit to the deinterleaver. The deinterleaver performs deinterleaving processing according to the metric value of each coded bit in the OFDM symbols transmitted from the demodulator, and transmits the obtained data symbols to the decoder. The decoder performs decoding processing on the data symbols output by the deinterleaver to obtain decoded data.

Further, the modulation symbol sequence is obtained by performing cyclic prefix removal, serial-to-parallel conversion, fast Fourier transform, and parallel-to-serial conversion on the OFDM symbols sent from the encoding end. The estimated value of the modulation symbol is obtained by encoding, interleaving and modulating the data output by the decoder.

Further, the data output by the decoder is subjected to error correction coding through the same coding process as that of the sending end to obtain coded bits of the OFDM symbol, and the coded bits of the OFDM symbol are processed and sent The interleaving process is the same as that of the terminal, and the estimated value of each bit of the modulation symbol on each subcarrier in the OFDM symbol is obtained, and the estimated value of each bit is modulated to obtain the orthogonal frequency division multiplexing symbol. Estimated value of the modulation symbol on each subcarrier in the frequency division multiplexing symbol.

Further, when the number of iterative processing in the interference estimation reaches a predetermined value, or the difference between the interference estimation results output twice consecutively by the interference estimation is less than a predetermined value, it is judged that the iteration in the interference estimation Processing has converged.

Further, the estimated value of the modulation symbol on each subcarrier in the OFDM symbol obtained according to the data output for the first time after the decoding process, and the channel estimation of each subcarrier in the OFDM symbol The result and the modulation symbol sequence are used for interference estimation by a predetermined algorithm, and an initial interference estimation result of each subcarrier in the OFDM symbol is obtained;

The estimated value of the modulation symbol on each subcarrier in the OFDM symbol obtained according to the data output last time after the decoding process, and the channel estimation result of each subcarrier in the OFDM symbol and the The symbol sequence is modulated, the interference estimation is performed by a predetermined algorithm, and the interference estimation result of this iteration of each subcarrier in the OFDM symbol is obtained.

Further, acquiring information on undisturbed subcarriers in OFDM symbols obtained according to the data output for the first time after the decoding process, and averaging the interference estimation results of all undisturbed subcarriers;

Obtaining information on uninterferenced subcarriers in OFDM symbols obtained according to the last output data after the decoding process, and averaging the interference estimation results of all uninterferenced subcarriers.

Further, performing sliding window filtering on the initial interference estimation results of each subcarrier in the OFDM symbol, where the size of the sliding window is set according to the number of subcarriers;

Perform sliding window filtering processing on the interference estimation results of the current iteration of each subcarrier in the OFDM symbol, and the size of the sliding window is set according to the number of the subcarriers.

In order to facilitate the understanding of the embodiments of the present invention, several specific embodiments will be taken as examples for further explanation below in conjunction with the accompanying drawings, and each embodiment does not constitute a limitation to the embodiments of the present invention.

Embodiment one

This embodiment proposes a schematic structural diagram of a device for joint interference estimation and encoding and decoding, as shown in Figure 3. The device is set in an OFDM receiver and includes the following modules: interference estimator, demodulator, deinterleaver, decoder , encoder, interleaver, modulator, and judgment control module. These units form a loop, and the process of interference estimation and encoding and decoding can be iteratively carried out in this loop until a more accurate original signal is obtained. The specific functions of each unit are introduced as follows:

1. Interference estimator:

The interference estimator performs interference estimation according to the modulation symbol transmitted by the modulator, the channel estimation result transmitted by the channel estimation module, and the received modulation symbol sequence, and obtains the power estimation of noise superimposed interference on each subcarrier (hereinafter referred to as interference estimated), and output to the demodulator.

The modulation symbol sequence is obtained by performing cyclic prefix removal, serial-to-parallel conversion, FFT conversion, and parallel-to-serial conversion on the OFDM symbols sent from the coding end.

The aforementioned interference estimator includes an initial interference estimation module and an iterative interference estimation module.

1.1, the initial interference estimation module, used for the estimated value of the modulation symbol on each subcarrier in the OFDM symbol obtained according to the data output by the decoder for the first time, and the channel estimation result and the modulation symbol sequence of each subcarrier in OFDM, performing interference estimation through a predetermined algorithm, and obtaining an initial interference estimation result of each subcarrier in an OFDM symbol;

的计算方法如下：Initial interference estimation of modulation symbols sent on the kth subcarrier in the Lth OFDM symbol in the OFDM communication signal received by the OFDM receiver

The calculation method is as follows:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; \&chi;</span>}}{\mathrm{<span\; class="notranslate">\; min</span>}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

The above x is the set of all signal points on the modulation constellation diagram, α _k ^l is the channel estimate of the kth subcarrier in the Lth OFDM symbol output by the channel estimation module of the OFDM receiver, and y _k ^l is the modulation symbol sequence .

为：Superimpose the initial interference estimates of the modulation symbols on the kth subcarrier from 1 to L OFDM symbols to obtain the initial interference estimates

for:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

1.2, the iterative interference estimation module, used for obtaining the estimated value of the modulation symbol on each subcarrier in the OFDM symbol according to the data output last time by the decoder, and the channel estimation result and the modulation symbol sequence of each subcarrier in the OFDM symbol, The interference estimation is performed by a predetermined algorithm, and the interference estimation result of this iteration of each subcarrier in the OFDM symbol is obtained.

In the device shown in Figure 3, the data output by the decoder is re-encoded, interleaved and modulated to obtain modulation symbols, and fed back to the interference estimator. The iterative interference estimation module uses the fed-back modulation symbols to go through multiple iterations An interference estimate is made, referred to as an interference estimate in an iteration.

，上述交织后的信号再通过调制器得到第p次迭代中对第L个OFDM符号中第k个子载波上的调制符号的干扰估计

，将从1到L个OFDM符号中第k个子载波上的调制符号的干扰估计进行叠加，得到的新的迭代中的干扰估计

为：The above initial interference estimate is the interference estimate in the 0th iteration. After the signal bits output by the decoder are re-encoded and interleaved, the estimated value of the i-th bit of the modulation symbol on the k-th subcarrier in the L-th OFDM symbol in the p-th iteration is obtained

, the above interleaved signal is then passed through the modulator to obtain the interference estimation of the modulation symbol on the kth subcarrier in the Lth OFDM symbol in the pth iteration

, superimpose the interference estimates of the modulation symbols on the kth subcarrier from 1 to L OFDM symbols, and obtain the interference estimation in the new iteration

for:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

2. Demodulator

The demodulator receives the modulation symbol sequence, the channel estimate transmitted by the channel estimation module and the interference estimate transmitted by the interference estimator, performs soft demodulation processing on the above received signal, and outputs the metric of each coded bit in the OFDM symbol value to the deinterleaver.

First calculate the corresponding $c_k^{i,l}=b$ , where c _k ^{i, l} is the i-th bit of the modulation symbol on the k-th subcarrier of the L-th OFDM symbol, 1≤i≤m, m is the order of modulation, b∈{0, 1}

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&Element;</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; min</span>}}\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="p"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">p</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

In the above formula ${\mathrm{\&chi;}}_b^i=\left\{\mathrm{\&mu;}(c_{k,p}^{1,l},...c_{k,p}^{i,l},...c_{k,p}^{m,l})\right|c_{k,p}^{i,l}=b\}$ is the set of all signal points corresponding to the i-th bit equal to b on the modulation constellation diagram, where μ is the modulation mapping function, and its function is to map m bits into a modulation symbol, is the interference estimation on the kth subcarrier of the pth iteration. For each coded bit, the metric output by the demodulator is:

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>$

3. Deinterleaver

The deinterleaver receives the metric value of each coded bit in the OFDM symbol output by the demodulator, and performs deinterleaving processing. The deinterleaving processing process is the inverse process of the interleaving processing, and outputs the obtained data symbols to the decoder.

4. Decoder

The decoder performs error correction decoding processing on the data symbols output by the decoder, corrects the error symbols, removes redundant information, and outputs the obtained data.

5. Encoder

The encoder performs error correction encoding on the data output by the decoder through the same encoding process as the sending end, and outputs the obtained encoded OFDM symbol information bits to the interleaver.

6. Interleaver

，将该估计值

输出到调制器。The interleaver performs interleaving processing on the encoded information bits of the OFDM symbol output by the encoder, that is, scrambles the order of the encoded information bits in the same manner as the sending end. After the information bits of the encoded OFDM symbols are interleaved, the estimated value of the i-th bit of the modulation symbol on the k-th subcarrier of the L-th OFDM symbol in the p-th iteration is obtained

, the estimated value

output to the modulator.

7. Modulator

The modulator modulates the estimated value of each bit of the modulation symbol on the kth subcarrier of the Lth OFDM symbol output by the interleaver to obtain the modulation symbol on the kth subcarrier of the Lth OFDM symbol in the pth iteration estimated value

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; (</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; c</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="p"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">p</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; c</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span>$

The modulator outputs the estimated value of the modulation symbol obtained above to the interference estimator.

8. A judging control module, configured to judge whether the iterative processing in the interference estimator converges, and if so, control to use the data output by the decoder as the final decoding result of the OFDM symbol; otherwise, control to The data output by the decoder is encoded, interleaved and modulated, and the estimated value of the obtained modulation symbol is transmitted to the interference estimator.

The data output by the above-mentioned decoder is not immediately output as the final decoding result, but is fed back to the interference estimator to complete new interference estimation and realize iteration. When the iteration reaches stability, that is, for any k, we have ${\widehat{\mathrm{\&sigma;}}}_{k,p+1}^2\&ap;{\widehat{\mathrm{\&sigma;}}}_{k,\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">p</figure-callout>}}^2,$ Or the number of iterations reaches a preset value, and the iterative process converges, and the data output by the decoder is controlled as the final decoding result of the OFDM symbol.

In this embodiment, by adopting an iterative algorithm processing process in interference estimation, the estimation accuracy of interference is greatly improved, so that the OFDM communication system obtains approximately optimal system performance.

Embodiment two

This embodiment improves the processing process of the interference estimator in the above-mentioned embodiment 1, and adds a frequency-domain part average processing process in the interference estimator. The principle of the average processing in the frequency domain is: determine the number information s of the interfered sub-carriers, obtain the positions of the s sub-carriers, average the noise power on the remaining sub-carriers determined not to be interfered, and obtain the average value.

1. Added the initial interference estimation of the average processing in the frequency domain

According to the calculation method of the initial interference estimate described in the first embodiment above, the initial interference estimate of the modulation symbol on the kth subcarrier in the 1 to L OFDM symbols is superimposed to obtain the initial interference estimate for:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

. Determine that the s subcarriers with the largest interference power in the above interference estimation are interfered subcarriers, and the judgment method is as follows:

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="k"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \&ForAll;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&Element;</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&ForAll;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Greater\; Equal;</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span>$

In the above formula, R is the set of sequence numbers of s subcarriers that are interfered, and R is the set of sequence numbers of all subcarriers, then the initial interference estimate output after the average processing in the frequency domain is as follows:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}\\ {\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}\end{array}\right.$

In the formula, K is the number of all subcarriers of OFDM.

2. Increase the interference estimation in the iteration of the average processing of the frequency domain part

为：According to the calculation method of the interference estimation in the iteration described in the first embodiment above, in the p-th iteration, the interference estimation of the modulation symbol on the k-th subcarrier in the 1 to L OFDM symbols is superimposed, and the obtained iteration Interference Estimation of

for:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

.Determine that the s subcarriers with the largest interference power in the interference estimation are interfered subcarriers, and the judgment method is as follows:

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="k"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; \&ForAll;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&Element;</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&ForAll;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Greater\; Equal;</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span>$

In the formula, R is the set of serial numbers of the interfered subcarriers, R is the set of serial numbers of all subcarriers, then the interference estimation of the p+1th iteration output after the average processing in the frequency domain is as follows:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}\\ {\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}\end{array}\right.$

This embodiment can effectively increase the convergence speed of the iterative process in the interference estimator, reduce the delay of signal detection, and enable the communication system to cope with narrow-band and rapidly changing interference conditions.

Embodiment three

This embodiment improves the processing process of the interference estimator in the first embodiment above, and adds a frequency domain sliding window filtering processing process in the interference estimator.

1. Added initial interference estimation for frequency domain sliding window filtering processing

为：According to the calculation method of the initial interference estimate described in the first embodiment above, the initial interference estimate of the modulation symbol on the kth subcarrier in the 1 to L OFDM symbols is superimposed to obtain the initial interference estimate

for:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

The initial interference estimate output after adding frequency domain sliding window filtering is:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

where ω _m is the sliding filter coefficient, ω _m satisfies $\underset{m=-m}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_m=1,$ The size of the sliding window is 2M+1, and the size of the sliding window is set according to the number of subcarriers.

Taking the size of the sliding window as 4 and the number of subcarriers as 8 as an example, the basic principle of the above sliding window filtering processing will be described below. First, the 1st to 4th subcarriers are extracted, and the interference power of these 4 subcarriers is averaged to obtain the first average value. Then, the 2nd to 5th subcarriers are extracted, and the interference power of these 4 subcarriers is averaged to obtain the second average value. By analogy, the 3-6th, 4-7th, and 5-8th subcarriers are respectively extracted to obtain the 3rd, 4th, and 5th average values respectively. Finally, the 1st, 2nd, 3rd, 4th, and 5th average values obtained above are used as new subcarrier interference power sequences.

2. Increase the interference estimation in the iteration of frequency domain sliding window filtering processing

为：According to the calculation method of the interference estimation in the iteration described in the first embodiment above, in the p-th iteration, the interference estimation of the modulation symbol on the k-th subcarrier in the 1 to L OFDM symbols is superimposed, and the obtained iteration Interference Estimation of

for:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}\underset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

The interference estimation of the p+1th iteration output after adding the frequency domain sliding window filtering process is as follows:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

where ω _m is the sliding filter coefficient, ω _m satisfies $\underset{m=-m}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_m=1,$ The size of the sliding window is 2M+1, and the size of the sliding window is set according to the number of subcarriers.

This embodiment can effectively increase the convergence speed of the iterative process in the interference estimator, reduce the delay of signal detection, and enable the communication system to cope with broadband interference.

Embodiment four

The processing flow of a method for estimating interference in an OFDM communication system provided in this embodiment is shown in FIG. 4 , including the following processing steps:

Step 41: According to the received modulation symbol sequence, modulation symbol estimation value and channel estimation result, perform interference estimation through multiple iterative processes, and obtain the interference estimation results of each subcarrier in the OFDM symbol.

The modulation symbol sequence is obtained by performing cyclic prefix removal, serial-to-parallel conversion, fast Fourier transform, and parallel-to-serial conversion on the OFDM symbols sent by the encoding end, and the estimated value of the modulation symbol is the output data after decoding It is obtained after encoding, interleaving and modulation processing.

In the above interference estimation process, the estimated value of the modulation symbol on each subcarrier in the OFDM symbol obtained according to the output data after the first decoding process, and the channel estimation result and the modulation symbol of each subcarrier in the OFDM symbol sequence, performing interference estimation through a predetermined algorithm, and obtaining an initial interference estimation result of each subcarrier in the OFDM symbol;

According to the estimated value of the modulation symbol on each subcarrier in the OFDM symbol obtained by the data output after the last decoding process, as well as the channel estimation result of each subcarrier in the OFDM symbol and the modulation symbol sequence, perform interference estimation by a predetermined algorithm, Obtain the interference estimation result of this iteration for each subcarrier in the OFDM symbol.

In practical applications, the above interference estimation process can also be improved. For example: obtain the subcarrier information that is not disturbed in the OFDM symbol obtained according to the data output after the first decoding process, average the interference estimation results of all subcarriers that are not disturbed, and obtain the average value; obtain according to The information on subcarriers not subjected to interference in the OFDM symbol obtained from the data output after the last decoding process is averaged to obtain an average value of the interference estimation results of all subcarriers not subjected to interference.

For another example, sliding window filtering is performed on the initial interference estimation results of each subcarrier in the OFDM symbol, and the size of the sliding window is set according to the number of the subcarriers; The interference estimation result of this iteration is processed by sliding window filtering, and the size of the sliding window is set according to the number of subcarriers.

Step 42: Perform soft demodulation processing to obtain the metric value of each coded bit in the OFDM symbol according to the interference estimation result of each subcarrier in the OFDM symbol, the modulation symbol sequence and the channel estimation result.

Step 43: Perform deinterleaving processing according to the metric value of each coded bit in the OFDM symbol, perform decoding processing on the data symbols output after the deinterleaving processing, and output the obtained data.

Step 44, judging whether the iterative processing in the interference estimation is convergent, if yes, use the output data after the decoding processing as the final decoding result of the OFDM symbol; otherwise, execute step 45.

When the number of iterative processing in the interference estimation reaches a predetermined value, or the difference between the interference estimation results output twice consecutively by the interference estimation is smaller than a predetermined value, it is judged that the iterative processing in the interference estimation has converged .

Step 45: After the decoded output data is subjected to the same encoding, interleaving and modulation processing as the sending end, the estimated value of the modulation symbol is obtained, and the estimated value of the modulation symbol is transmitted to the interference estimation process.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be implemented through computer programs to instruct related hardware, and the programs can be stored in a computer-readable storage medium. During execution, it may include the processes of the embodiments of the above-mentioned methods. Wherein, the storage medium may be a magnetic disk, an optical disk, a read-only memory (Read-Only Memory, ROM) or a random access memory (Random Access Memory, RAM), etc.

To sum up, the embodiment of the present invention greatly improves the interference estimation accuracy by adopting the iterative algorithm processing process in the interference estimation, so that the OFDM communication system obtains approximately optimal system performance. The computational complexity of the above iterative algorithm is twice that of the general non-iterative interference estimation method. This increase in complexity is acceptable.

The embodiment of the present invention also greatly improves the convergence speed of interference estimation and decoding by adopting frequency domain part averaging processing and frequency domain sliding window filtering processing, so that the communication system can cope with narrow-band and fast-changing, as well as broadband interference situations.

The embodiment of the present invention can not only be used in cognitive radio scenarios, but also suitable for situations where there is interference from other communication systems in wireless communication. For example, in the coexistence of a broadband OFDM communication system and a relatively narrowband Bluetooth communication system, it can be used for The wideband OFDM communication system suppresses the interference from the Bluetooth communication system; or it is used to suppress the interference from adjacent cells in the cellular mobile communication system using OFDM technology.

In order to verify the performance advantages of the embodiments of the present invention, a computer simulation is performed, and part of the simulation content and results are attached below. The first thing to do is to simulate the system under different interference conditions. The simulation environment is narrow-band interference. The simulation results are shown in Figure 5. In Fig. 5, the abscissa is the interference intensity, and the ordinate is the bit error rate. LIED represents the performance of the interference estimation method proposed in the embodiment of the present invention, IED represents the limit performance of the interference estimation method proposed in the embodiment of the present invention, MLD represents the limit performance of all interference estimation methods, and conventional represents the performance when the interference estimation method is not used Performance, the parameter P represents the number of iterations. It can be seen from FIG. 4 that the performance of the interference estimation method proposed by the embodiment of the present invention can reach the MLD limit performance under all interference strength conditions.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (9)

1. An apparatus for interference estimation in an orthogonal frequency division multiplexing communication system, comprising:

the interference estimator is used for carrying out interference estimation through iterative processing according to a received modulation symbol sequence, a modulation symbol estimation value and a channel estimation result to obtain an interference estimation result of each subcarrier in the orthogonal frequency division multiplexing symbol, wherein the modulation symbol estimation value is obtained by coding, interweaving and modulating data output by the decoder;

the demodulator is used for carrying out soft demodulation processing according to the received modulation symbol sequence, the channel estimation result and the interference estimation result transmitted by the interference estimator to obtain the metric value of each coding bit in the orthogonal frequency division multiplexing symbol;

the de-interleaver is used for performing de-interleaving processing according to the metric value of each coding bit in the orthogonal frequency division multiplexing symbol transmitted by the demodulator to obtain a data code element;

the decoder is used for decoding the data code element output by the de-interleaver to obtain the decoded data;

the interference estimator specifically includes:

an initial interference estimation module, configured to perform interference estimation according to a modulation symbol estimation value on each subcarrier in an orthogonal frequency division multiplexing symbol obtained by decoding processed data for the first time, and a channel estimation result and the modulation symbol sequence of each subcarrier in the orthogonal frequency division multiplexing symbol, by using a predetermined algorithm, and obtain an initial interference estimation result of each subcarrier in the orthogonal frequency division multiplexing symbol;

the iterative interference estimation module is used for carrying out interference estimation through a preset algorithm according to the modulation symbol estimation value on each subcarrier in the orthogonal frequency division multiplexing symbol obtained by decoding the processed data for the last time, and the channel estimation result of each subcarrier in the orthogonal frequency division multiplexing symbol and the modulation symbol sequence to obtain the interference estimation result of the current iteration of each subcarrier in the orthogonal frequency division multiplexing symbol;

specifically, the initial interference estimation module is further configured to obtain information of subcarriers that are not interfered in the ofdm symbol and obtained according to the data after the first decoding processing, average interference estimation results of all subcarriers that are not interfered, and obtain an average value;

the iterative interference estimation module is further configured to obtain non-interfered subcarrier information in the ofdm symbol obtained according to the data decoded and processed last time, average interference estimation results of all non-interfered subcarriers, and obtain an average value;

or,

the initial interference estimation module is further configured to perform sliding window filtering processing on initial interference estimation results of each subcarrier in the ofdm symbol, where the size of the sliding window is set according to the number of the subcarriers;

the iterative interference estimation module is further configured to perform sliding window filtering processing on an interference estimation result of the current iteration of each subcarrier in the orthogonal frequency division multiplexing symbol, where the size of the sliding window is set according to the number of the subcarriers.

2. The apparatus for interference estimation in an orthogonal frequency division multiplexing communication system of claim 1, wherein the apparatus further comprises:

a judgment control module, configured to judge whether iteration processing in the interference estimator converges, and if so, take the decoded data as a final decoding result of the ofdm symbol; otherwise, the data after decoding processing is further processed by coding, interleaving and modulation, and the obtained modulation symbol estimation value is transmitted to the interference estimator.

3. The apparatus of interference estimation in an orthogonal frequency division multiplexing communication system of claim 2, wherein:

the judgment control module is further configured to judge that the iterative processing in the interference estimator has converged if the number of iterative processing in the interference estimator reaches a predetermined value, or if a difference between interference estimation results output by the interference estimator for two consecutive times is smaller than a predetermined value.

4. The apparatus for interference estimation in an orthogonal frequency division multiplexing communication system of claim 1, wherein the apparatus further comprises:

the encoder is used for carrying out error correction coding on the decoded data in the same coding process as that of the sending end to obtain the coded bits of the orthogonal frequency division multiplexing symbols;

the interleaver is used for interleaving the coded bits of the orthogonal frequency division multiplexing symbols transmitted by the encoder in the same interleaving process as that of the transmitting end to obtain the estimated value of each bit of the modulation symbols on each subcarrier in the orthogonal frequency division multiplexing symbols;

and the modulator is used for modulating the estimated value of each bit transmitted by the interleaver to obtain the estimated value of the modulation symbol on each subcarrier in the orthogonal frequency division multiplexing symbol, and transmitting the estimated value of the modulation symbol to the interference estimator.

5. A method of interference estimation in an orthogonal frequency division multiplexing communication system, comprising:

performing interference estimation through iterative processing according to a received modulation symbol sequence, a modulation symbol estimation value and a channel estimation result to obtain an interference estimation result of each subcarrier in an orthogonal frequency division multiplexing symbol, and performing soft demodulation processing according to the interference estimation result, the modulation symbol sequence and the channel estimation result to obtain a metric value of each coding bit in the orthogonal frequency division multiplexing symbol;

performing de-interleaving processing according to the metric value of each coded bit in the orthogonal frequency division multiplexing symbol, decoding the data code element output after the de-interleaving processing, and acquiring the data after the decoding processing, wherein the modulation symbol estimated value is obtained after the data after the decoding processing is subjected to coding, interleaving and modulation processing;

the interference estimation through iterative processing to obtain the interference estimation result of each subcarrier in the orthogonal frequency division multiplexing symbol specifically includes:

performing interference estimation according to the modulation symbol estimation value on each subcarrier in the orthogonal frequency division multiplexing symbol obtained by the data after the first decoding processing, and the channel estimation result and the modulation symbol sequence of each subcarrier in the orthogonal frequency division multiplexing symbol by a preset algorithm to obtain the initial interference estimation result of each subcarrier in the orthogonal frequency division multiplexing symbol;

performing interference estimation through a preset algorithm according to the modulation symbol estimation value on each subcarrier in the orthogonal frequency division multiplexing symbol obtained by the data after the last decoding processing, and the channel estimation result of each subcarrier in the orthogonal frequency division multiplexing symbol and the modulation symbol sequence to obtain the interference estimation result of the current iteration of each subcarrier in the orthogonal frequency division multiplexing symbol;

specifically, obtaining non-interfered subcarrier information in an orthogonal frequency division multiplexing symbol obtained according to the data after the first decoding processing, averaging interference estimation results of all non-interfered subcarriers, and obtaining an average value;

obtaining the information of the sub-carriers which are not interfered in the orthogonal frequency division multiplexing symbol obtained according to the data after the last decoding processing, averaging the interference estimation results of all the sub-carriers which are not interfered, and obtaining an average value;

or,

performing sliding window filtering processing on initial interference estimation results of each subcarrier in the orthogonal frequency division multiplexing symbol, wherein the size of the sliding window is set according to the number of the subcarriers;

and performing sliding window filtering processing on the interference estimation result of the current iteration of each subcarrier in the orthogonal frequency division multiplexing symbol, wherein the size of the sliding window is set according to the number of the subcarriers.

6. The method of claim 5, wherein the modulation symbol sequence is obtained by performing cyclic prefix removal, serial-to-parallel conversion, fast Fourier transform, and parallel-to-serial conversion on the OFDM symbols transmitted from the encoder.

7. The method of interference estimation in an orthogonal frequency division multiplexing communication system of claim 5, wherein the method further comprises:

judging whether the iterative processing in the interference estimation is converged, if so, taking the data after decoding processing as the final decoding result of the orthogonal frequency division multiplexing symbol; otherwise, the data after decoding processing is coded, interleaved and modulated to obtain a modulation symbol estimation value, and the modulation symbol estimation value is transmitted to the interference estimation process.

8. The method of estimating interference in an ofdm communication system according to claim 7, wherein the determining whether iterative processing in the interference estimation converges specifically comprises:

and judging that the iterative processing in the interference estimation is converged if the number of iterative processing in the interference estimation reaches a preset value or the difference value between interference estimation results output by the interference estimation for two consecutive times is smaller than a preset value.

9. The method of claim 7, wherein the obtaining the modulation symbol estimation value after the data output after the decoding process is further encoded, interleaved, and modulated, comprises:

carrying out error correction coding on the data output after the decoding processing through the same coding process as that of the sending end to obtain the coding bits of the orthogonal frequency division multiplexing symbols;

interleaving the coded bits of the orthogonal frequency division multiplexing symbol in the same interleaving process as that of a sending end to obtain the estimated value of each bit of the modulation symbol on each subcarrier in the orthogonal frequency division multiplexing symbol;

and modulating the estimated value of each bit to obtain the estimated value of the modulation symbol on each subcarrier in the orthogonal frequency division multiplexing symbol.

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