RU2289883C2 - Method for quasi-coherent reception of multibeam signal - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: proposed method for quasi-coherent reception of multibeam signal that enables solving problem of enhancing noise immunity of multibeam signal reception in orthogonal frequency division multiplexing (OFDM) communication systems is characterized in use of statistics-adapted channel for propagating complex harmonic envelope estimate algorithm that does not need much money for computer services.

EFFECT: enhanced precision of complex harmonic estimates and, consequently, enhanced noise immunity in data reception.

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Description

The invention relates to the field of radio engineering, in particular to a method for the quasicoherent reception of a multipath signal in communication systems with many subcarriers (OFDM - Orthogonal Frequency Division Multiplexing).

Recently, OFDM communication systems have been greatly developed. An OFDM signal is a sequence of OFDM symbols. Each such symbol consists of two parts - a prefix and a multi-frequency information symbol. A multi-frequency information symbol is the sum of modulated harmonics. Usually multilevel phase (PSK - phase-shift keying) and amplitude-phase (QAM - quadrature amplitude modulation) types of signal modulation are used. The prefix means a certain sequence of samples of the signal, which immediately precedes each multi-frequency information symbol and is a part of this symbol. As a rule, the prefix duration is less than the duration of the information symbol. The presence of a prefix during signal processing allows you to reduce or completely eliminate intersymbol interference (see IEEE Std 802.11a - 1999, Prokis J., Digital Communications, Translation from English, M .: Radio and Communications, 2000, p. 593) [1 ].

The transmitted message is a sequence of information symbols (modulating harmonics). Known pilot symbols designed to evaluate the complex harmonic envelope are periodically inserted into this sequence. In the IEEE 802.11a communication system (see Supplement to IEEE Standard for Information technology. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHZ Band) [2] the second part of the preamble, which includes two long training multi-frequency symbols and a guard interval (prefix), can also be used to evaluate the complex harmonic envelope. A preamble is a special known signal that precedes an informational message. An example of the structure of the reference signals (pilot symbols and the second part of the preamble) is presented in figure 1.

In communication systems, the signal propagation channels between the receiver and the data transmitter are multipath and non-stationary. When receiving MPSK or MQAM modulated signals, the effectiveness of communication systems is largely determined by the ability of channel estimation algorithms to provide the necessary accuracy of complex envelope estimation in multipath non-stationary channels. Note that in OFDM communication systems, the complex envelope is estimated in the two-dimensional time-frequency domain.

Known methods for quasi-coherent signal reception in OFDM communication systems are described, for example, in the work of Sandell M, O. Efors A Comparative Study of Pilot-Based Channel Estimators for Wireless OFDM, Research Report TULEA, Sep., 1996 [3]. In this paper, several algorithms for estimating the complex envelope from a pilot signal are proposed. Two main approaches to the estimation of the complex envelope are distinguished. The first is the use of a filter in a two-dimensional time-frequency domain. The second is the use of two filters (in the frequency and time domains). When using a filter in a two-dimensional time-frequency domain, the estimate of the complex envelope of information symbols is the result of weight summation of the complex envelope and the nearest (in the time-frequency domain) pilot symbols. The use of two separate filters in the frequency and time domains allows us to implement a slightly simpler algorithm for estimating the complex envelope. First, weight summation of the values of the complex envelope of the pilot symbols is carried out in the time domain, and then in the frequency domain.

When using pilot symbols to estimate the complex envelope, high-quality demodulation of information symbols is possible if the multipath interval of the received signal τ _max satisfies the inequality (see Richard van Nee, Ramjee Prasad, OFDM Wireless Multimedia Communications, Artech House, Boston-London, 2000) [4 ]

where F _p is the frequency difference corresponding to neighboring pilot symbols. In accordance with the specifications of the communication system [2], the frequency difference of adjacent pilot symbols F _p = 4375 kHz. In this case, in accordance with (1), the admissible multipath interval of the received signal is 0≤τ _max ≤110 ns, which is significantly less than the required interval 0≤τ _max ≤800 ns. Thus, the use of only pilot symbols to estimate the complex envelope is unacceptable.

формируется в соответствии со следующим выражениемThere is a method of channel estimation that minimizes the mean square error (MMSE) of the mean envelope estimate described in J. - J. van de Beek, O. Edfors, M. Sandell, SKWilson and POBorjesson. On channel estimation in OFDM systems. In Proc. IEEE Vehic. Technol. Conf., Vol. 2, pages 815-819, Chicago, IL, July 1995 [5]. In accordance with the MMSE algorithm, an estimate of the complex envelope of harmonics (subcarriers)

formed in accordance with the following expression

- дисперсия шума. В алгоритме MMSE производится адаптация к каналу распространения за счет оценки автоковариационной матрицы R_gg. Структура алгоритма MMSE оценки канала показана на фиг.2.where y is the observed implementation of the signal, X is the transmitted data, F is the Fourier transform matrix, R _gg is the autocovariance matrix of the impulse response of the propagation channel,

- noise variance. In the MMSE algorithm, adaptation is made to the distribution channel by evaluating the autocovariance matrix R _gg . The structure of the MMSE channel estimation algorithm is shown in FIG.

The described MMSE algorithm allows a fairly high-quality estimate of the complex envelope. However, the implementation of the algorithm is quite complicated, since in addition to performing the inverse and direct Fourier transforms, it is necessary to evaluate the autocovariance matrix R _gg , inverse and multiply the matrices.

Closest to the claimed solution is a method of quasi-coherent signal reception, described in the book Nee R. Prasad R., OFDM for Wireless Multimedia Communication, London: "Artech House", 2000, chapter 5. Coherent and Differential Detection, 5.2. Coherent Detection, 5.2.3. Special Training Symbols, pp. 104-106; chapter 10. Applications of OFDM. 10.5.4 Training, pp. 246-248 [6].

This method of quasi-coherent signal reception is as follows:

the input signal is filtered, amplified, transferred to the video frequency, its analog-to-digital conversion and decimation are carried out, forming the input digital complex signal at the video frequency;

carry out time-frequency synchronization, determining the temporary position of the beginning of the preamble and the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal,

correcting the phase of the input digital complex signal, taking into account the estimate of the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal;

find complex spectra of long multi-frequency symbols of the preamble of the phase-corrected input digital complex signal, the temporal positions of which are determined by the temporal position of the beginning of the preamble,

form estimates of the complex envelope of modulated harmonics of the long multi-frequency symbols of the preamble using the complex spectra of long multi-frequency symbols of the preamble,

combine estimates of the complex envelope of modulated harmonics of long multi-frequency symbols of the preamble, forming preliminary estimates of the complex envelope of modulated harmonics,

find complex spectra of multi-frequency information symbols of the phase-corrected input digital complex signal, the temporal positions of which are determined by the temporal position of the beginning of the preamble,

remember the components of the complex spectra of multi-frequency information symbols corresponding to modulated harmonics,

form estimates of the complex envelope of the harmonics of the multi-frequency information symbols modulated by the pilot symbols using the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols,

for each multi-frequency information symbol, a correction value is generated using the estimates of the complex envelope of the harmonics modulated by the pilot symbols of this multi-frequency information symbol and the corresponding preliminary estimates of the complex envelope of the modulated harmonics,

for each multifrequency information symbol, final estimates of the complex envelope of modulated harmonics with information symbols are generated by correcting preliminary estimates of the complex envelope of modulated harmonics using a correction value corresponding to this multifrequency information symbol,

form soft decisions about information symbols using the corresponding components of the complex spectra of multi-frequency information symbols and the final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols.

In this case, the time-frequency synchronization is carried out, for example, as given in the book Nee R. Prasad R., OFDM for Wireless Multimedia Communication, London: "Artech House", 2000, chapter 4. Synchronization. 4.6. Synchronization using Special Training Symbols, pp. 86-88; chapter 10. Applications of OFDM. 10.5.4 Training, pp. 246-247 [7].

The phase of the input digital complex signal is adjusted by multiplying the samples of the input digital complex signal by a complex factor of unit amplitude, the phase of which is equal to the product of the frequency shift estimate by the time positions of the samples.

Complex spectra of multi-frequency symbols are determined by fast discrete Fourier transform of samples of the phase-corrected input digital complex signal corresponding to the analyzed multi-frequency symbols. The temporary position of the beginning of the long multi-frequency symbol of the preamble is defined as the sum of the temporary position of the beginning of the preamble and the a priori known temporary position of this long multi-frequency symbol relative to the beginning of the preamble. The temporary position of the beginning of the multi-frequency information symbol is defined as the sum of the temporary position of the beginning of the preamble, a priori known temporary position of the OFDM symbol including this multi-frequency symbol, relative to the beginning of the preamble and the duration of the prefix.

Estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols form, for example, by multiplying the components of the complex spectra of long multi-frequency preamble symbols by the complex conjugate values of the symbols modulating the corresponding harmonics. The meanings of the symbols modulating the harmonics of the long multi-frequency symbols of the preamble are a priori known.

Combining estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols is performed by averaging the sums of the estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols.

Estimates of the complex envelope of the multi-frequency information symbol harmonics modulated by the pilot symbols are multiplied by multiplying the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols by the complex conjugate values of the pilot symbols modulating the corresponding harmonics. The values of the pilot symbols are a priori known.

The correcting value of the multifrequency information symbol is formed as the average sum of the relations of the product of the complex envelope modulation modulated by the harmonic pilot symbol and the corresponding complex conjugate preliminary estimate of the complex envelope to the square of the complex envelope modulated harmonic pilot symbol estimation module.

The final estimates of the complex envelope of the harmonics of the multifrequency information symbol modulated by information symbols are generated by multiplying the preliminary estimates of the complex envelope of the modulated harmonics by the correction value corresponding to this multi-frequency information symbol.

Soft decisions about information symbols are formed, for example, by multiplying the corresponding components of the complex spectra of multi-frequency information symbols by the complex conjugate final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols.

Note that the values of the envelope of harmonics vary according to a continuous law, being correlated, as a rule, over the interval of several harmonics. Therefore, the main disadvantage of the prototype method is the refusal to use the estimates of the complex envelope of neighboring harmonics when obtaining a preliminary estimate of the complex envelope of the harmonic, which impairs the noise immunity of the quasi-coherent multipath signal reception.

The problem that the claimed invention solves is to increase the noise immunity of the quasi-coherent reception of a multipath OFDM signal of a communication system.

The technical result is achieved due to the fact that in the method of quasicoherent reception of a multipath signal, which consists in the fact that:

the input signal is filtered, amplified, transferred to the video frequency, its analog-to-digital conversion and decimation are carried out, forming the input digital complex signal at the video frequency,

carry out time-frequency synchronization, determining the temporary position of the beginning of the preamble and the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal,

correct the phase of the input digital complex signal, taking into account the estimate of the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal,

find complex spectra of long multi-frequency symbols of the preamble of the phase-corrected input digital complex signal, the temporal positions of which are determined by the temporal position of the beginning of the preamble,

form estimates of the complex envelope of modulated harmonics of the long multi-frequency symbols of the preamble using the complex spectra of long multi-frequency symbols of the preamble,

combine estimates of the complex envelope of modulated harmonics of long multi-frequency symbols of the preamble, forming preliminary estimates of the complex envelope of modulated harmonics,

find complex spectra of multi-frequency information symbols of the phase-corrected input digital complex signal, the temporal positions of which are determined by the temporal position of the beginning of the preamble,

remember the components of the complex spectra of multi-frequency information symbols corresponding to modulated harmonics,

form estimates of the complex envelope of the harmonics of the multi-frequency information symbols modulated by the pilot symbols using the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols,

for each multi-frequency information symbol, a correction value is generated using the estimates of the complex envelope of the harmonics modulated by the pilot symbols of this multi-frequency information symbol and the corresponding preliminary estimates of the complex envelope of the modulated harmonics,

for each multifrequency information symbol, final estimates of the complex envelope of modulated harmonics with information symbols are generated by correcting preliminary estimates of the complex envelope of modulated harmonics using a correction value corresponding to this multifrequency information symbol,

form soft decisions about information symbols using the corresponding components of the complex spectra of multi-frequency information symbols and the final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols,

according to the invention, the following sequence of actions is introduced:

form the average value of preliminary estimates of the complex envelope of modulated harmonics,

correct the preliminary estimates of the complex envelope of the modulated harmonics, subtracting the average value of these estimates,

form estimates of the correlation function samples of the complex envelope of harmonics using adjusted preliminary estimates of the complex envelope of modulated harmonics,

form an estimate of the multipath interval of the input signal using the generated estimates of the samples of the correlation function of the complex envelope of harmonics,

filtering corrected preliminary estimates of the complex envelope of the modulated harmonics, determining the weighting coefficients of the filter according to the evaluation of the multipath interval of the input signal,

formulate refined preliminary estimates of the complex envelope of modulated harmonics, adding the average value of preliminary estimates of the complex envelope of modulated harmonics to the filtered corrected preliminary estimates of the complex envelope of modulated harmonics,

after generating estimates of the complex envelope of the harmonics of the multi-frequency information symbols modulated by the pilot symbols, the updated estimates of the complex envelope of the harmonics of the multi-frequency information symbols modulated by the pilot symbols are generated by filtering the estimates of the complex envelope of the modulated pilot symbols of the harmonics of the multi-frequency information symbols,

moreover, when generating a correction value for each multi-frequency information symbol, accurate estimates of the complex envelope of the harmonics modulated by the pilot symbols of the harmonics of this multi-frequency information symbol and the corresponding updated preliminary estimates of the complex envelope of modulated harmonics are used,

final estimates of the complex envelope of harmonics modulated by information symbols for each multifrequency information symbol are formed by correcting the updated preliminary estimates of the complex envelope of modulated harmonics using a correction value corresponding to this multifrequency information symbol.

Moreover, the time-frequency synchronization is carried out, for example, as described in [7].

The phase of the input digital complex signal is adjusted by multiplying the samples of the input digital complex signal by a complex factor of unit amplitude, the phase of which is equal to the product of the frequency shift estimate by the time positions of the samples.

The complex spectra of multi-frequency symbols are determined by the fast discrete Fourier transform of the samples of the phase-corrected input digital complex signal corresponding to these multi-frequency symbols.

The temporary position of the beginning of the long multi-frequency symbol of the preamble is defined as the sum of the temporary position of the beginning of the preamble and the a priori known temporary position of this long multi-frequency symbol relative to the beginning of the preamble.

Estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols are formed by multiplying the components of the complex spectra of long multi-frequency preamble symbols by complex conjugate values of symbols modulating the corresponding harmonics, and the values of symbols modulating harmonics of long multi-frequency preamble symbols are a priori known.

Combining estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols is performed by averaging the sums of the estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols.

The average value of preliminary estimates of the complex envelope of modulated harmonics is formed as the ratio of the sum of preliminary estimates of the complex envelope of modulated harmonics by their number.

The corrected preliminary estimates of the complex envelope of modulated harmonics are obtained by subtracting from the preliminary estimates of the complex envelope of modulated harmonics the average value of the preliminary estimates of the complex envelope of modulated harmonics.

Estimates of the samples of the correlation function of the complex harmonic envelope form as a half-sum of the estimates of the correlation function samples of the in-phase and quadrature components of the complex harmonic envelope.

An estimate of the multipath interval of the input signal is formed by averaging estimates of the multipath interval of the input signal obtained from various estimates of the samples of the correlation function of the complex harmonic envelope, and finding the ratio of the difference in the estimate of the correlation function of the complex harmonic envelope and parameter b by the product of the reference number, the frequency difference of neighboring harmonics and parameter but.

The parameters b and a depend on the magnitude of the estimate of the reference of the correlation function and are the coefficients of approximation of the broken line of the correlation function of the in-phase and quadrature components of the complex envelope.

The adjusted preliminary estimates of the complex envelope of the modulated harmonics are filtered by weighting the adjusted preliminary estimates of the complex envelope of the modulated harmonics, while the filtering weights are proportional to the zero-order Bessel function of the product of the multipath of the input signal and the harmonic frequency difference.

The complex spectra of multi-frequency information symbols are determined by the fast discrete Fourier transform of the samples of the phase-corrected input digital complex signal corresponding to these multi-frequency symbols.

The temporary position of the beginning of the multi-frequency information symbol is defined as the sum of the temporary position of the beginning of the preamble, a priori known temporary position of the beginning of the OFDM symbol, a signal block including this multi-frequency symbol, relative to the beginning of the preamble and the duration of the prefix.

Estimates of the complex envelope of harmonics of the multi-frequency information symbols modulated by pilot symbols are multiplied by multiplying the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols by the complex conjugate values of the pilot symbols modulating the corresponding harmonics, and the values of the pilot symbols are a priori known.

Refined estimates of the complex envelope of the modulated by pilot symbols harmonics of multi-frequency information symbols are generated by averaging the estimates of the complex envelope of the modulated pilot symbols of harmonics of multi-frequency information symbols.

The correction value of the multi-frequency information symbol is formed as the average sum of the product relations of the refined estimate of the complex envelope modulated by the harmonic pilot symbol and the corresponding complex conjugate refined preliminary estimate of the complex envelope to the square of the complex envelope estimation module modulated by the harmonic pilot symbol.

The final estimates of the complex envelope of the harmonics of the multifrequency information symbol modulated by the information symbols are generated by multiplying the refined preliminary estimates of the complex envelope of the modulated harmonics by the correction value corresponding to this multi-frequency information symbol.

Soft decisions about information symbols are formed by multiplying the corresponding components of the complex spectra of multi-frequency information symbols by the complex conjugate final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols.

The inventive method of quasi-coherent reception of a multipath signal has significant differences from the closest technical solutions identified from the prior art. The differences lie in the use of a statistics-adaptive distribution channel estimation algorithm for estimating the complex envelope of harmonics, which is based on the developed original algorithm for estimating the propagation channel multipath interval.

These differences provide increased noise immunity of quasi-coherent multipath signal reception in an OFDM communication system.

The description of the invention is illustrated by examples and drawings:

Figure 1 shows the structure of the reference signals (pilot symbols and the second part of the preamble).

Figure 2 is a structural diagram of a well-known MMSE algorithm.

Figure 3 is a structural diagram of a device on which the inventive method is carried out.

Figure 4 - structural diagram of block 8 of the time synchronization.

Figure 5 is a structural diagram of a block 11 for the formation of refined preliminary estimates of the complex envelope of modulated harmonics.

Figure 6 is a structural diagram of a block 1 forming a correction value.

7 is a structural diagram of block 14 for the formation of final estimates of the complex envelope of modulated harmonics.

On Fig is a structural diagram of block 13 for the formation of soft decisions about information symbols.

Structural diagrams of blocks 8, 11, 12, 13 and 14, made respectively in FIGS. 4, 5, 6, 8 and 7, are given as examples of execution.

The inventive method of quasi-coherent multipath signal reception is carried out using the following sequence of actions.

The input signal is filtered, amplified, transferred to the video frequency, its analog-to-digital conversion and decimation are carried out, forming the input digital complex signal at the video frequency.

The time-frequency synchronization is carried out, determining the temporary position of the beginning of the preamble and the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal. Moreover, the time-frequency synchronization is carried out, for example, as described in [7].

The phase of the input digital complex signal is adjusted taking into account the estimate of the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal. Moreover, the phase of the input digital complex signal is corrected, for example, by multiplying the samples of the input digital complex signal by a complex factor of unit amplitude, the phase of which is equal to the product of the frequency shift estimate by the time positions of the samples.

Complex spectra of long multi-frequency symbols of the preamble of the phase-corrected input digital complex signal are found, the temporal positions of which are determined by the temporal position of the beginning of the preamble. Moreover, the complex spectra of multi-frequency symbols are determined by the fast discrete Fourier transform of the samples of the phase-corrected input digital complex signal corresponding to these multi-frequency symbols, and the temporary position of the beginning of the long multi-frequency symbol of the preamble is determined as the sum of the temporary position of the beginning of the preamble and the a priori known temporal position of this long multi-frequency symbol relative to beginning of the preamble.

Estimates of the complex envelope of modulated harmonics of the long multi-frequency symbols of the preamble are generated using the complex spectra of the long multi-frequency symbols of the preamble. In this case, estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols are formed, for example, by multiplying the components of complex spectra of long multi-frequency preamble symbols by complex conjugate values of symbols modulating the corresponding harmonics, and the values of symbols modulating harmonics of long multi-frequency preamble symbols are a priori known.

Combine the estimates of the complex envelope of the modulated harmonics of the long multi-frequency symbols of the preamble, forming preliminary estimates of the complex envelope of the modulated harmonics. Moreover, for example, combining estimates of the complex envelope of modulated harmonics of long multi-frequency preamble symbols is performed by averaging the sums of estimates of the complex envelope of the corresponding modulated harmonics of long multi-frequency preamble symbols.

The average value of preliminary estimates of the complex envelope of modulated harmonics is formed. Moreover, the average value of preliminary estimates of the complex envelope of modulated harmonics is formed, for example, as the ratio of the sum of preliminary estimates of the complex envelope of modulated harmonics by their number.

The preliminary estimates of the complex envelope of modulated harmonics are corrected by subtracting the average value of these estimates.

Estimates of the samples of the correlation function of the complex envelope of harmonics are generated using the adjusted preliminary estimates of the complex envelope of modulated harmonics. Moreover, estimates of the samples of the correlation function of the complex envelope of harmonics are formed, for example, as a half-sum of estimates of the samples of the correlation function of the in-phase and quadrature components of the complex envelope of harmonics, as described in Cooper J., McGill K. Probabilistic methods for the analysis of signals and systems: Per. from English - M .: Mir, 1989 .-- 376 p. silt. Chapter 11 - Digital methods of analysis, 11.4.1. - Direct estimation of covariance function, p. 380 [8].

An estimate of the multipath interval of the input signal is generated using the generated estimates of the samples of the correlation function of the complex harmonic envelope. Moreover, the estimate of the multipath interval of the input signal is formed, for example, by averaging the estimates of the multipath interval of the input signal obtained from various estimates of the correlation function samples of the complex harmonic envelope, and finding the ratio of the difference in the estimate of the correlation function of the complex harmonic envelope and parameter b by the product of the reference number, the frequency difference of adjacent harmonics and parameter a, while parameters b and a depend on the value of the estimate of the correlation function and represent the coefficients cients approximation polyline correlation function phase and quadrature components of the complex envelope.

The adjusted preliminary estimates of the complex envelope of the modulated harmonics are filtered, determining the weighting coefficients of the filter by estimating the multipath interval of the input signal. Moreover, the corrected preliminary estimates of the complex envelope of modulated harmonics are obtained, for example, by subtracting from the preliminary estimates of the complex envelope of modulated harmonics the average value of the preliminary estimates of the complex envelope of modulated harmonics.

Refined preliminary estimates of the complex envelope of modulated harmonics are generated by adding the average value of preliminary estimates of the complex envelope of modulated harmonics to the filtered corrected preliminary estimates of the complex envelope of modulated harmonics.

The complex spectra of multi-frequency information symbols of the phase-corrected input digital complex signal are found, the temporary positions of which are determined by the temporary position of the beginning of the preamble. The complex spectra of multi-frequency information symbols are determined, for example, by the fast discrete Fourier transform of the samples of the phase-corrected input complex digital signal corresponding to these multi-frequency symbols, and the time position of the beginning of the multi-frequency information symbol is determined as the sum of the time position of the beginning of the preamble, a priori known time position of the beginning of the OFDM symbol - a signal unit including this multi-frequency symbol, relative to the beginning of the preamble prefix length.

The components of the complex spectra of multi-frequency information symbols corresponding to modulated harmonics are remembered.

Estimates of the complex envelope of the harmonics of the multi-frequency information symbols modulated by the pilot symbols are estimated using the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols.

Refined estimates of the complex envelope of the multi-frequency information symbol harmonics modulated by the pilot symbols are generated by filtering and, for example, averaging the estimates of the complex envelope estimates of the multi-frequency information symbol harmonics modulated by the pilot symbols.

For each multi-frequency information symbol, a correction value is generated using the updated estimates of the complex envelope of the harmonics of the multi-frequency information symbol modulated by the pilot symbols and the corresponding updated preliminary estimates of the complex envelope of the modulated harmonics. Moreover, the correcting value of the multi-frequency information symbol is formed, for example, as the average sum of the relations of the product of the refined estimate of the complex envelope modulated by the harmonic pilot symbol and the corresponding complex conjugate refined preliminary estimate of the complex envelope to the square of the complex envelope estimation module modulated by the harmonic pilot symbol.

For each multifrequency information symbol, final estimates of the complex envelope of the harmonics modulated by the information symbols are generated by correcting the adjusted preliminary estimates of the complex envelope of the modulated harmonics using the correction value corresponding to this multifrequency information symbol. Moreover, the final estimates of the complex envelope of the harmonics of the multifrequency information symbol modulated by the information symbols are formed, for example, by multiplying the refined preliminary estimates of the complex envelope of the modulated harmonics by the correction value corresponding to this multi-frequency information symbol.

Soft decisions about information symbols are formed using the corresponding components of the complex spectra of multi-frequency information symbols and the final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols. Moreover, soft decisions about information symbols are formed, for example, by multiplying the corresponding components of the complex spectra of multi-frequency information symbols by the complex conjugate final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols.

The inventive method is carried out for the quasi-coherent reception of a multipath signal on a device whose structural diagram is shown in FIG. 3.

The quasi-coherent multipath signal receiving device (Fig. 3) contains a receiving path 1, a time-frequency synchronization unit 2, a complex multiplier 3, a harmonic generation unit 4, a first register 5 and a second register 6, a clock 7, a time synchronization unit 8, block 9 for calculating the complex spectrum of the signal, switching unit 10, block 11 for generating refined preliminary estimates of the complex envelope of modulated harmonics, block 12 for generating a correction value, block 13 for generating soft decisions about information symbols and block 14 for generating final estimates of the complex envelope of modulated harmonics, while the input of the receiving path 1 is the input of the device, the first and second outputs of the receiving path are connected respectively to the first and second inputs of the complex multiplier 3 and block 2 of the time-frequency synchronization, the first output of which connected to the first input of the harmonic generation unit 4, the second input of which is combined with the third input of the time-frequency synchronization unit 2 and the first input of the time synchronization unit 8 and connected to the output of the clock generator 7, the first and second outputs of the harmonic generation unit 4 are connected respectively to the third and fourth inputs of the complex multiplier 3, the first and second outputs of which are connected respectively to the inputs of the first 5 and second 6 registers, the outputs of which are connected respectively to the first and the second inputs of the complex signal spectrum calculation unit 9, the third input of which is connected to the first output of the time synchronization unit 8, the second input of which is connected to the second output of the unit 2 frequency time synchronization, the second output of the time synchronization unit 8 is connected to the second input of the switching unit 10, the first input of which is connected to the output of the complex signal spectrum calculating unit 9, the first output of the switching unit 10 is connected to the first input of the unit 11 for generating updated preliminary estimates of the complex envelope of modulated harmonics, the second input of which is connected to the third output of the time synchronization block 8, the output of the block 11 for generating the updated preliminary estimates of the complex envelope modulated of harmonics is connected to the third input of block 14 for generating final estimates of the complex envelope of modulated harmonics and the second input of block 12 for generating correction values, the first input of which is combined with the first input of block 13 for generating soft decisions about information symbols and connected to the second output of block 10 for switching, the first and the second outputs of the correcting value generating unit 12 are connected respectively to the first and second inputs of the final estimating unit 14 of the complex envelope module Rowan harmonics, whose output is connected to the second input 13 of the block forming soft decisions about information symbols whose output is an output device.

The device operates (figure 3) as follows. In the receiving path 1, the input signal that arrives at its input is pre-filtered, amplified, transferred to the video frequency, carried out its analog-to-digital conversion, decimation, etc. As a result, an input digital complex signal is formed at a video frequency.

The in-phase and quadrature components of the input digital signal from the first and second outputs of the receiving path 1 are received respectively at the first and second inputs of the complex multiplier 3 and, respectively, at the first and second inputs of the block 2 of the time-frequency synchronization.

Frequency-time synchronization is carried out, for example, as described in [7]. A device with which it is possible to carry out time-frequency synchronization is described in the patent of the Russian Federation No. 2235429, published on August 27, 2004 in BI No. 24/2004 [9].

In the device (figure 3), which carry out the inventive method, the clock of the unit 2 of the time-frequency synchronization (in contrast to [9]) is taken out of its limits. In this case, the clock signal is supplied from the output of the clock generator 7 to the third input of the block 2 of the time-frequency synchronization. From the first output of the time-frequency synchronization block 2, the frequency shift estimate is supplied to the first input of the harmonic generation block 4. Assessment of the temporary position of the end of the first long multi-frequency preamble symbol from the second output of the frequency-time synchronization block 2 is supplied to the second input of the time-synchronization block 8.

In the harmonic generation unit 4, according to the frequency shift estimate and the signal from the clock generator 7 supplied to its second input, a complex unit amplitude multiplier is formed, the phase of which is equal to the product of the frequency shift estimate by the time position of the current samples. The quadrature components of the complex factor from the first and second outputs of the harmonic generation unit 4 are respectively supplied to the third and fourth inputs of the complex multiplier 3, in which the phase of the input digital complex signal is corrected. To do this, in the complex multiplier 3 carry out the well-known operation of multiplying the samples of the input digital complex signal by a complex factor. The in-phase component of the phase-corrected input digital complex signal from the first output of the complex multiplier 3 is input to the first serial-parallel register 5, and the quadrature component from the second output of the complex multiplier 3 is input to the second serial-parallel register 6. In registers 5 and 6 are stored samples of quadrature components of the phase-corrected input digital complex signal at intervals of duration of multi-frequency symbols.

Registers 5 and 6 with sequential recording and parallel reading can be implemented, for example, on the basis of standard microcircuits of the 561PR1 series or 1564IR8 series or the like.

From the output of the first register 5, the set of samples of the in-phase component of the phase-corrected input digital complex signal corresponding to the analyzed multi-frequency symbols is fed to the first input of the complex signal spectrum calculation unit 9. From the output of the second register 6, the set of samples of the quadrature component of the phase-corrected input digital complex signal corresponding to the analyzed multi-frequency symbols is fed to the second input of the complex signal spectrum calculation unit 9. The third input of block 9 for calculating the complex spectrum of the signal from the first output of block 8 of the time synchronization receives the end signal of the multi-frequency symbol (long multi-frequency preamble symbol or the next multi-frequency information symbol). By the signal of the end of the multi-frequency symbol, the complex spectrum of the corresponding multi-frequency symbol is calculated, the quadrature components of the reports of the input digital signal of which at this point in time are stored in register 5 and register 6 respectively. The signal of the end of the multi-frequency symbol is generated in block 8 of the time synchronization signal of the time position of the end of the first long multi-frequency symbol of the preamble, arriving at its second input, and the clock signal, which arrives at and his first entry.

From the output of block 9 for calculating the complex spectrum of the signal, the quadrature components (real and imaginary parts) of the components of the complex spectrum are fed to the first input of the switching unit 10, the second input of which receives a control signal from the second output of the time synchronization block 8. Block 10 switching is a collection of keys with a common controlled input. When processing signals of long multi-frequency symbols of the preamble, the control signal is logical zero, and the quadrature components of the complex spectrum components are supplied from the first output of the switching unit 10 to the first input of the unit 11 for generating updated preliminary estimates of the complex envelope of modulated harmonics. Then, when receiving multi-frequency information symbols, the control signal is a logical unit, and the quadrature components of the components of the complex spectrum corresponding to the information symbols are received from the second output of the switching unit 10 to the first input of the soft decision block 13 for forming information symbols, and the quadrature components of the components of the complex spectrum, corresponding to the pilot symbols, come from the second output of the switching unit 10 to the first input of the correction value generating unit 12.

At the second input of block 11 for the formation of refined preliminary estimates of the complex envelope of modulated harmonics, a reset signal is received from the third output of time synchronization block 8. The reset signal is generated after the end of the reception of the entire information message and provides the ability to receive the next information message. From the output of block 11 for the formation of refined preliminary estimates of the complex envelope of modulated harmonics, the quadrature components of the refined preliminary estimates of the complex envelope of harmonics modulated with information symbols go to the third input of block 14 for the formation of final estimates of the complex envelope of modulated harmonics, and the quadrature components of refined preliminary estimates of the complex envelope of modulated harmonics pilot symbols are fed to the second input of the block 12 formation corrective value.

From the first output of the correcting value generating unit 12, the in-phase component of the correcting value of the current multi-frequency information symbol is fed to the first input of the generating unit 14 of the final estimates of the complex envelope of modulated harmonics. From the second output of the correcting value generating unit 12, the quadrature component of the correcting value of the current multi-frequency information symbol is fed to the second input of the generating unit 14 of the final estimates of the complex envelope of modulated harmonics.

From the output of block 14 for the formation of final estimates of the complex envelope of modulated harmonics, the quadrature components of the final estimates of the complex envelope for modulated information symbols of harmonics go to the second input of block 13 for forming soft decisions about information symbols.

The output of block 13 for forming soft decisions about information symbols is the output of the device.

For a better understanding of the implementation of the proposed method, let us consider in more detail the operation of blocks 8, 11, 12, 13 and 14 included in the device (Fig. 3). Block diagrams of the blocks are given as an example of execution, respectively, in FIGS. 4, 5, 6, 8 and 7.

Block 8 of the time synchronization (figure 4) contains the OR circuit 15, the first register 16, the second register 19, the third register 23, the first key 17 and the second key 20, the first counter 18, the second counter 21 and the third counter 22, while the second inputs of the first key 17 and the second key 20 are combined to form the first input of the time synchronization block 8, the first, second inputs of the first register 16 and the first input of the OR circuit 15 are combined to form the second input of the time-frequency synchronization block 8, the output of the first register 16 connected to the first input of the first key 17, the output of which is connected with the input of the first counter 18, the output of which is connected to the third input of the first register 16, the first and second inputs of the second register 19 and the second input of the OR circuit 15, the output of which is the first output of the time synchronization unit 8, the output of the second register 19 is connected to the first input the second key 20, the output of which is connected to the input of the second counter 21, the output of which is connected to the third input of the OR circuit 15, the input of the third counter 22 and the first and second inputs of the third register 23, the output of which is the second output of block 8, the third input of tego register 23 is combined with the third input of the second register 19 and is connected to the output of the third counter 22, whose output is the output of the third unit 8 time synchronization.

Block 8 time synchronization operates as follows.

In the first arm containing the first register 16, the first key 17 and the first counter 18, the end signal of the second long multi-frequency preamble symbol is generated. In the second arm containing the second register 19, the second key 20 and the second counter 21, end signals of multi-frequency information symbols are generated.

At the first (data input) and second (write input) inputs of the first register 16 and the first input of the OR circuit 15 from the second input of the time synchronization unit 8, the end signal of the first long multi-frequency preamble symbol is received. When the signal ends the first long multi-frequency preamble symbol at the output of the OR circuit 15, a start signal is generated for calculating the spectrum of the multi-frequency symbol, which is transmitted to the first output of the time synchronization block 8.

When the end signal of the first long multi-frequency preamble symbol arrives in the first register 16, a signal equal to a logical unit is written, which from the output of the first register 16 is fed to the first controlled input of the first key 17. To the second inputs of the first key 17 and second key 20 from the first input of block 8 a signal is received from the clock generator 7, which through the first key 17 is fed to the input of the first counter 18. At the third input (reset) of the first register 16, the output of the first counter 18 receives the zeroing (control) signal.

After the arrival of the end signal of the first long multi-frequency preamble symbol, the first counter 18 accumulates clock pulses. It is programmed in such a way that the end signal of the second long multi-frequency preamble symbol, equal to a logical one, appears at its output at a point in time equal, for example, to the sum of the temporary position of the end of the first long multi-frequency preamble symbol and the duration of the long multi-frequency preamble symbol.

The end signal of the second long multi-frequency preamble symbol is supplied to the second input of the OR circuit 15. At the same time, at the output of the OR circuit 15, a start signal is generated for calculating the spectrum of the multi-frequency symbol (second long multi-frequency symbol of the preamble).

By the signal of the end of the second long multi-frequency preamble symbol, which is fed to the first data input and the second input of the second register 19, a signal equal to a logical unit is recorded in the register 19, which from the output of the second register 19 is supplied to the first controlled input of the second key 20. In this case the signal from the clock generator 7 through the second key 20 is fed to the input of the second counter 21.

After the arrival of the end signal of the second long multi-frequency preamble symbol, the second counter 21 accumulates the clock pulses. It is programmed in such a way that a pulse signal is generated at its output with a period equal to the duration of the OFDM symbol. The pulses of the signal (signals equal to a logical unit) correspond to the time moments of the end of the next multi-frequency information symbol. The end signal of the next multi-frequency information symbol is fed to the third input of the OR circuit 15. At the same time, at the output of the OR circuit 15, a start signal is generated for the spectrum calculation procedure for the next multi-frequency information symbol.

The signal from the output of the second counter 21 also goes to the first and second inputs of the third register 23 and to the input of the third counter 22. According to the signal of the end of the first multi-frequency information symbol, a signal equal to a logical unit is written to the third register 23, which is output from the third register 23 to the second the output of block 8 time synchronization. The second output of the time synchronization unit 8 is a control output to the switching unit 10.

The third counter 22 accumulates the end pulses of the next multi-frequency information symbol. It is programmed in such a way that at its output a signal is generated for the end of the information message, equal to a logical unit, which goes to the third input of the second register 19, the third input of the third register 23 and resets their contents. Also, the output of the third counter 22 is the third output of the block 8 time synchronization.

Counters 18, 21 and 23 can be implemented, for example, on the basis of standard programmable counters such as 564IE10 or the like.

Block 11 for the formation of refined preliminary estimates of the complex envelope of modulated harmonics (Fig. 5) contains L nodes for generating preliminary estimates of the complex envelope of modulated harmonics 24 ₁ -24 _L , the first node 30 and the second node 31 averaging, L nodes 32 ₁ -32 _{L of} complex subtraction, filtering the first node 33 and second node 34 filtering unit 35 forming weighting filter coefficient and L units 36 ₁ -36 _L complex summation, each assembly 24 ₁ -24 _L forming preliminary estimates of the complex envelope modulirova GOVERNMENTAL harmonic element 25 comprises removing information from the first reservoir 26 and second discharge drive 27 with reset, the first member 28 and second normalization element 29 valuation, the first and second input member 25 reading information in each node on January ₂₄ -24 _L forming preliminary assessments the complex envelope of the modulated harmonics form a first input block 11, the second inputs of accumulators 26 and 27 with discharge at each node January ₂₄ -24 _L forming preliminary estimates of the complex envelope of the modulated harmonic form a second input of block 11, the first and second outputs of item 25 reading information in each node on January ₂₄ -24 _L forming preliminary estimates of the complex envelope of the modulated harmonics are respectively connected to first inputs of accumulators 26 and 27 with reset, outputs of which are respectively connected to the inputs of the first member 28 and second member valuation 29 normalization, the output of the first element 28 normalization of each node 24 ₁ -24 _{L the} formation of preliminary estimates of the complex envelope of modulated harmonics is connected to the first input of the corresponding nodes la 32 ₁ -32 _L complex subtraction and the corresponding input of the first averaging node 30, the output of the second normalization element 29 of each node 24 ₁ -24 _L generating preliminary estimates of the complex envelope of modulated harmonics is connected to the second input of the corresponding complex 32 ₁ -32 _L complex subtraction node and the corresponding input of the second averaging unit 31, the output of the first averaging unit 30 is connected to the third inputs of each complex subtraction unit 32 ₁ -32 _L and each complex summing unit 36 ₁ -36 _L , the output of the second unit 31 averaging is connected to the fourth inputs of each node 32 ₁ -32 _L complex subtraction and each node 36 ₁ -36 _L complex summation, the first outputs of nodes 32 ₁ -32 _L complex subtraction are connected to their corresponding first L inputs of the first filter node 33 and their corresponding first L input node 35 forming weighting filter coefficients, the second output node 32 ₁ -32 _L complex subtraction connected to their respective first L inputs of the second filter unit 34 and the corresponding second input node 35 L forming veso th filter coefficient, the output node 35 forming weighting filter coefficients is coupled to second inputs of the first node 33 and the second filtering unit 34 filtering, the first node L filter 33 outputs are connected to first inputs of corresponding nodes 36 ₁ -36 _L complex summing unit outputs a second L 34 filter connected to the second inputs of the corresponding nodes 36 ₁ -36 _L complex summing the first and second outputs of each node 36 ₁ -36 _L form a complex summation output (bus) 11 forming a block of refined n edvaritelnyh assessments of the complex envelope of the modulated harmonics.

Block 11 for the formation of refined preliminary estimates of the complex envelope of modulated harmonics works as follows.

From the first input of block 11, the set of in-phase and quadrature components L of the complex spectra of long multi-frequency preamble symbols is supplied to the first and second inputs L of the nodes 24 ₁ -24 _L, respectively, of forming preliminary estimates of the complex envelope of modulated harmonics, each of which forms in-phase and quadrature components (components ) a preliminary estimate of the complex envelope of one modulated harmonic. In each node 24 ₁ -24 _{L of the} formation of preliminary estimates of the complex envelope of modulated harmonics, the in-phase and quadrature components of the component (harmonic) of the complex spectra arrive respectively at the first and second inputs of the information pickup element 25, where they are multiplied by the complex conjugate value of the symbol modulating this spectrum component (harmonic). The meanings of the symbols modulating the harmonics of the long multi-frequency symbols of the preamble are a priori known. From the first output of the information pickup element 25, the in-phase components of the estimates of the complex envelope of the modulated harmonic of the long multi-frequency preamble symbols are sent to the first input of the first drive 26 with a reset. From the second output of the information pickup element 25, the quadrature components of the estimates of the complex envelope of the modulated harmonic of the long multi-frequency preamble symbols are sent to the first input of the second drive 27 with a reset. In accumulators 26 and 27 with reset, the common-mode and quadrature components of the estimates of the complex envelope of the modulated harmonic of all long multi-frequency preamble symbols are summed, respectively. The results of the summation (accumulation) of the in-phase component from the output of the first drive 26 with a discharge are fed to the input of the first element 28 normalization. The results of the summation (accumulation) of the quadrature component from the output of the second drive 27 with a discharge are fed to the input of the second element 29 normalization. In the elements 28 and 29 normalization is the division of the results of the summation (accumulation) by the number of long multi-frequency characters. The in-phase and quadrature components of the preliminary estimates of the complex envelope of L modulated harmonics generated from the first and second outputs of the L nodes 24 ₁ -24 _{L of the} formation of preliminary estimates of the complex envelope of the modulated harmonics generated (in elements 28 and 29 of the normalization) arrive at the first and second inputs of the nodes 32 ₁ - 32 _L complex subtraction. The common-mode components of the preliminary estimates of the complex envelope L of modulated harmonics from the first outputs of L nodes 24 ₁ -24 _L also arrive respectively at the L inputs of the first averaging node 30. The quadrature components of the preliminary estimates of the complex envelope L of modulated harmonics from the second outputs of the L nodes 24 ₁ -24 _L also arrive respectively at the L inputs of the second averaging node 31. In the nodes 30 and 31 of averaging, the input quantities are summed, followed by dividing the result by L. As a result, the in-phase component is formed at the output of the first averaging unit 30, and the quadrature component of the average value of the preliminary estimates of the complex envelope of modulated harmonics is formed at the output of the second averaging unit 31.

The second inputs of drives 26 and 27 with a reset receive a reset signal from the second input of block 11 (the output signal from block 8 of temporary synchronization), by which the contents of the drives 26 and 27 are reset to zero.

In L nodes 32 ₁ -32 _{L of the} complex subtraction, in-phase and quadrature components of L adjusted preliminary estimates of the complex envelope of modulated harmonics are formed by subtracting from the preliminary estimates of the complex envelope of modulated harmonics the average value of the preliminary estimates of the complex envelope of modulated harmonics, the in-phase and quadrature components of which arrive respectively at the third and the fourth inputs of the nodes 32 ₁ -32 _L. The in-phase and quadrature components of the corrected preliminary estimates of the complex envelope of modulated harmonics formed in L nodes 32 ₁ -32 _{L of the} complex subtraction come from the first and second outputs of the nodes 32 ₁ -32 _L to the L and L second inputs of the node 35 for forming filtering weighting coefficients, respectively.

The common-mode components of the corrected preliminary estimates of the complex envelope L of modulated harmonics from the first outputs of L nodes 32 ₁ -32 _{L of} complex subtraction also arrive respectively at the first L inputs of the first filtering node 33. The quadrature components of the corrected preliminary estimates of the complex envelope L of modulated harmonics from the second outputs of the L nodes 32 ₁ -32 _L complex subtraction also arrive respectively at the first L inputs of the second filtering node 34.

In the node 35 of the formation of weighting filtration coefficients perform the following calculations:

, находя полусумму оценок отсчетов корреляционной функции синфазной и квадратурной составляющих комплексной огибающей гармоник.1. Form estimates of the correlation function samples of the complex envelope of harmonics K _n ,

, finding half the sum of the estimates of the correlation function in-phase and quadrature components of the complex envelope of harmonics.

where A _{c, i} , A _{s, i} are respectively in-phase and quadrature components of the corrected preliminary estimates of the complex envelope of modulated harmonics, M is the number of generated experimental readings of the channel correlation function.

, попадающих в диапазон значений: -0.30÷0.932. Find normalized estimates of the multipath interval of the input signal for each of M 'experimental values

falling into the range of values: -0.30 ÷ 0.93

Parameters b, a are presented in the table.

3. Averaging the estimate of the multipath interval of the input signal over all values of K _j , we obtain the final estimate of the multipath interval of the input signal

4. Determine the filtering weights in proportion to the zero order Bessel function

The second inputs of the filtering units 33 and 34 receive the weighting coefficients of the filter from the output of the block 35 of forming the weighting coefficients of the filtering. In the filtering nodes 33 and 34, the in-phase and quadrature components of the adjusted preliminary estimates of the complex envelope of the modulated harmonics are filtered, by weighting the in-phase and quadrature components of the adjusted preliminary estimates of the complex envelope of the modulated harmonics, respectively.

From the L outputs of the first filtering node 33, the in-phase components of the filtered corrected preliminary estimates of the complex envelope of the modulated harmonics arrive respectively at the first inputs of the L nodes 36 ₁ -36 _{L of the} complex summation. From the L outputs of the second filtration unit 34, the quadrature components of the filtered corrected preliminary estimates of the complex envelope of the modulated harmonics arrive respectively at the second inputs of the L nodes 36 ₁ -36 _{L of the} complex summation. The third and fourth inputs of the L nodes 36 ₁ -36 _L complex summing respectively receive signals from nodes 30 and 31 averaging.

In L nodes 36 ₁ -36 _{L of the} complex summation, in-phase and quadrature components of L updated preliminary estimates of the complex envelope of modulated harmonics are formed, adding to the filtered corrected preliminary estimates of the complex envelope of modulated harmonics, the average value of preliminary estimates of the complex envelope of modulated harmonics, the in-phase and quadrature components of which arrive respectively from the outputs of the first averaging unit 30 and the second averaging unit 31.

The outputs of the nodes 36 ₁ -36 _L complex summation form the output (bus) of the block 11 forming the updated preliminary estimates of the complex envelope of modulated harmonics.

The correction value generating unit 12 (Fig. 6) contains P nodes 37 ₁ -37 _{P for} generating an updated estimate of the complex envelope of multi-frequency information symbols harmonics modulated by pilot symbols; P nodes 44 ₁ -44 _P calculation of the correction value, the first adder 50 and the second adder 51, the first division unit 52 and the second division unit 53. Each node 37 ₁ -37 _{P of the} formation of a refined estimate of the complex envelope of the multi-frequency information symbols harmonics modulated by the pilot symbols of the harmonics contains a modulation removal subassembly 38, a first filtering element 39 and a second filtering element 40, each filtering element comprising a delay line 41, an adder 42 and a subelement 43 rationing. Each node 44 ₁ -44 _P calculation of the correction value contains a complex multiplier 45, element 46 complex conjugation, element 47 of finding the square of the module of complex value, the first element 48 division and the second element 49 division A / B. The first and second inputs of the modulation removal subassembly 38 at each node 37 ₁ -37 _{P of the} formation of a refined estimate of the complex envelope of the multi-frequency information symbols harmonic modulated by pilot symbols are the first and second inputs of nodes 37 ₁ -37 _P and form the first input of block 12 (bus) of forming a correction value, the first output of the modulation removal unit 38 is connected to the input of the delay line 41 in the first filter element 39, the second output of the modulation removal unit 38 is connected to the input of the delay line 41 in the second filter element 40 tration, the first, second and third output lines 41 delay elements 39 and 40 filter are connected respectively to the first, second and third inputs of the adder 42, whose output is connected to the input sub-element 43 valuation, yield subelement 43 normalization is the first output of each node 37 ₁ - 37 _P forming a refined estimation of the complex envelope of the modulated pilot symbols harmonics multifrequency information symbols and the output of the second filter element 40 - respectively the second output of each node 37 ₁ -37 _P forming a refinement hydrochloric evaluation of the complex envelope of the modulated pilot symbols harmonics multifrequency information symbols, first and second outputs of nodes 37 ₁ -37 _P forming a refined estimation of the complex envelope of the modulated pilot symbols harmonics multifrequency information symbols are respectively connected to first and second inputs of the corresponding nodes 44 ₁ -44 calculating the correction value _P, the first and second inputs of which form respective first and second inputs of complex multipliers 45, third and fourth inputs com integrated polices multipliers 45 in each node 44 ₁ -44 _P are respectively connected to first and second outputs of complex conjugation element 46, first and second inputs of which are combined respectively with the first and second input element 47 of finding the square magnitude of complex modulus, forming respectively the third and fourth input nodes 44 ₁ -44 _P , which are the second input of block 12 (bus), the first and second outputs of the complex multiplier 45 are connected respectively to the first input of the first A / B division element 48 and the first input of the second element and 49 A / B divisions, the second inputs of the elements 48 and 49 are combined and connected to the output of the element 47 of finding the square of the module of complex magnitude, the output of the first element 48 is the first output of each node 44 ₁ -44 _P , and the output of the second element 49 is the second output of each node 44 ₁ -44 _P , the first outputs P nodes 44 ₁ -44 _{P of the} calculation of the correction value are connected to the corresponding P inputs of the first adder 50, the second outputs P nodes 44 ₁ -44 _{P of the} calculation of the correction value are connected to the corresponding P inputs of the second adder 51 the output of the first adder 50 connected to the input of the first node 52 dividing by P, the output of which is the first output of block 12, the output of the second adder 51 is connected to the input of the second node 53 of dividing by P, the output of which is the second output of block 12.

The block 12 for the formation of the correction value is as follows.

From the first input of block 12, in-phase and quadrature components P of the complex spectra of multi-frequency information symbols used to transmit pilot symbols are received at the first and second inputs P of the nodes 37 ₁ -37 _{P of the} formation of a refined estimate of the complex envelope of the harmonics of the multi-frequency information symbols modulated by pilot symbols In-phase and quadrature components P of the constituent complex spectra of multi-frequency information symbols used to transmit pilot symbols, at each node 37 ₁ -37 _P , respectively, are supplied to the first and second inputs of the modulation removal subunit 38. In the submodule 38 for removing the modulation, estimates of the complex envelope of the multi-frequency information symbol harmonics modulated by the pilot symbols are generated by multiplying the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols by the complex conjugate values of the pilot symbols modulating the corresponding harmonics. The values of the pilot symbols are a priori known. The in-phase components of the estimates of the complex envelope of the harmonics modulated by the pilot symbols from the first output of the modulation removal unit 38 are input to the first filtering element 39. The quadrature components of the estimates of the complex envelope of the harmonics modulated by the pilot symbols from the second output of the modulation removal unit 38 are input to the second filtering element 40. In the filtering elements 39 and 40, quadrature estimates of the complex envelope of the harmonic modulated by the pilot symbols are summed by summing in the adder 42 delayed estimates of the complex envelope modulated by the pilot symbol of the corresponding harmonics of the multi-frequency information symbols stored in the delay line 41, followed by dividing the summation by the number of sum members in the sub-element 43 rationing. The outputs of the sub-elements 43 of normalization of the first filtering elements 39 are the first outputs of the nodes 37 ₁ -37 _P forming an updated estimate of the complex envelope of the multi-frequency information symbols harmonic modulated by the pilot symbols, which are connected to the first inputs of the correcting value calculation nodes 44 ₁ -44 _P of them. The outputs of the subelement 43 of normalization of the second filtering elements 40 are the second outputs of the nodes 37 ₁ -37 _P forming an updated estimate of the complex envelope of the multi-frequency information symbols harmonic modulated by the pilot symbols, which are connected to the second inputs of the corresponding correction value calculation nodes 44 ₁ -44 _P.

The third and fourth inputs of the nodes 44 ₁ -44 _P for calculating the correction value from the second input of block 12 receive, respectively, in-phase and quadrature components P of updated preliminary estimates of the complex envelope of the harmonics corresponding to the pilot symbols.

In each node 44 ₁ -44 _{P, the} calculation of the correction value is formed in the first division element 48 and in the second division element 49, the ratio (formed in the complex multiplier 45) of the product of the refined estimate of the complex envelope modulated by the pilot symbol of the harmonic and the corresponding complex conjugate (in element 46 complex conjugation) of the refined preliminary estimate of the complex envelope to the square of the module for estimating the complex envelope modulated by the harmonic pilot symbol (formed in element 47 the squared modulus of a complex quantity).

The in-phase components of the correction values from the output of the first A / B dividing element 48 and, accordingly, from the first outputs P of the nodes 44 ₁ -44 _{P of the} calculation of the correction value are supplied respectively to the P inputs of the first adder 50. The quadrature components of the correction values from the output of the second A / B dividing element 49 and accordingly, from the second outputs of the P nodes 44 ₁ -44 _{P, the} calculation of the corrective values are received respectively at the P inputs of the second adder 51.

From the output of the first adder 50, the signal enters the input of the first division unit 52 by P, and from the output of the second adder 51, the signal enters the input of the second division unit 53 by P. As a result, in-phase and in-site 53 quadrature components of the correction value of the current multi-frequency information symbol, which respectively arrive at the first and second outputs of block 12.

Block 14 for the formation of final estimates of the complex envelope of modulated harmonics can be performed, for example, as shown in Fig. 7, and contains N complex multipliers 54 ₁ -54 _N , the first and second inputs of which are the third inputs of block 14 (bus), the third and fourth the inputs of N complex multipliers 54 ₁ -54 _N are respectively the first and second inputs of block 14, and the first and second outputs of complex multipliers 54 ₁ -54 _N are the outputs of block 14 (bus).

A unit 14 for generating final estimates of the complex envelope of modulated harmonics operates as follows.

The common-mode and quadrature components of N refined preliminary estimates of the complex envelope modulated by information symbols of harmonics from the third input of block 14 are respectively supplied to the first and second inputs of N complex multipliers 54 ₁ -54 _N , the third and fourth inputs of which respectively receive the common-mode and quadrature components of the correction value of the current symbol, respectively, from the first and second inputs of block 12. In complex multipliers 54 ₁ -54 _N , the well-known operation of multiplying two k complex quantities. The set of multiplication results, which is the in-phase and quadrature components of the N final estimates of the complex envelope modulated with information symbols of harmonics, from the first and second outputs of the complex multipliers 54 ₁ -54 _N goes to the output of block 14 for the formation of the final estimates of the complex envelope of modulated harmonics.

Block 13 for the formation of soft decisions about information symbols (Fig. 8) contains N first lines 55 ₁ -55 _{N of} delay and N second lines 56 ₁ -56 _{N of} delay, N nodes 57 ₁ -57 _{N of} calculation of soft decisions, each of which contains a complex a multiplier 58 and an integrated coupling element 59, wherein the inputs of the N first delay lines 55 ₁ -55 _N and the N second delay lines 56 ₁ -56 _N are the first inputs of block 13, the outputs of the N first delay lines 55 ₁ -55 _N and the N second lines 56 ₁ -56 _N delays connected respectively with the first and second inputs of the corresponding units 57 ₁ -57 _N calculation softly second solutions, the first and second inputs of which are formed by the first and second inputs of the complex multiplier 58, the third and fourth inputs which are respectively connected to first and second output element 59 of complex conjugation, the first and second inputs of which are respectively the third and fourth inputs of each node 57 ₁ -57 _N calculating a soft decision, these inputs are the second input of block 13 (bus). The first and second outputs of the complex multiplier 58 of each soft decision calculation node 57 ₁ -57 _N form the first and second outputs of the soft decision nodes 57 ₁ -57 _N , respectively, which are the outputs of block 13 (bus).

The block 13 for the formation of soft decisions about information symbols works as follows.

In-phase and quadrature components of the N constituent complex spectra of multi-frequency information symbols used to transmit information symbols from the first input of block 13 are received at the inputs of N first delay lines 55 ₁ -55 _N and N second delay lines 56 ₁ -56 _N , respectively, where they are stored . The delay of the components of the complex spectra of multi-frequency information symbols is necessary to compensate for the delay in the formation of the final estimates of the complex envelope arising in the block 12 for the formation of the correction value.

From the outputs of the N first delay lines 55 ₁ -55 _N and N the second delay lines 56 ₁ -56 _N, respectively, the common-mode and quadrature components of the N components of the complex spectra of multi-frequency information symbols respectively arrive at the first and second inputs of N nodes 57 ₁ -57 _N for calculating soft solutions , the third and fourth inputs of which respectively receive in-phase and quadrature components of N final estimates of the complex envelope of harmonics modulated by information symbols. At nodes 57 ₁ -57 _{N, the} soft decision calculations are performed by multiplying (in the complex multiplier 58) the components of the complex spectra of multi-frequency information symbols by the corresponding complex conjugate (in the complex conjugation element 59) final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols.

The set of generated in-phase and quadrature components of N soft decisions about information symbols from the first and second outputs of nodes 57 ₁ -57 _N for calculating soft decisions is sent to the output of block 13 (bus) of forming soft decisions about information symbols.

Thus, the inventive method does not require significant costs during implementation, significantly increases the noise immunity of the quasi-coherent reception of a multipath signal in an OFDM communication system and expands the scope.

Claims (16)

1. The method of quasi-coherent reception of a multipath signal, namely, that the input signal is filtered, amplified, transferred to the video frequency, its analog-to-digital conversion and decimation are performed, forming the input digital complex signal at the video frequency, time-frequency synchronization is carried out, determining the time position of the beginning the preambles and the frequency shift between the carrier frequency of the input signal and the frequency of the reference signal, adjust the phase of the input digital complex signal, taking into account the frequency of the shift between the carrier frequency of the input signal and the frequency of the reference signal, find the complex spectra of long multi-frequency symbols of the preamble of the phase-corrected input digital complex signal, the temporal positions of which are determined by the time position of the beginning of the preamble, form estimates of the complex envelope of modulated harmonics of the long multi-frequency symbols of the preamble using complex spectra of long multi-frequency symbols of the preamble and a priori known values of symbols modulating monics of long multi-frequency symbols of the preamble, combine estimates of the complex envelope of modulated harmonics of long multi-frequency symbols of the preamble, forming preliminary estimates of the complex envelope of modulated harmonics, find complex spectra of multi-frequency information symbols phase-corrected digital input complex signal, the temporary positions of which are determined by the time position of the beginning of the preamble, remember components of the complex spectra of multi-frequency information x symbols corresponding to modulated harmonics form estimates of the complex envelope of multi-frequency information symbols harmonics modulated by pilot symbols of harmonics using the components of complex spectra of multi-frequency information symbols used to transmit pilot symbols and a priori known values of pilot symbols modulating the corresponding harmonics for each multi-frequency information of the symbol form a correction value, for each multi-frequency information symbol the form final estimates of the complex envelope modulated by information symbols of harmonics, form soft decisions about information symbols using the corresponding components of the complex spectra of multi-frequency information symbols and final estimates of the complex envelope of modulated information symbols harmonics of these multi-frequency information symbols, characterized in that after the preliminary estimates of the complex envelope are formed modulated harmonics form the mean e preliminary estimates of the complex envelope of modulated harmonics, correct preliminary estimates of the complex envelope of modulated harmonics, generate estimates of the correlation function of the complex envelope of harmonics using the adjusted preliminary estimates of the complex envelope of modulated harmonics, form an estimate of the multipath of the input signal using the generated estimates of the samples of the correlation function of the complex envelope of the complex filter adjusted precursors Estimates of the complex envelope of modulated harmonics, using the estimate of the multipath interval of the input signal, form refined preliminary estimates of the complex envelope of modulated harmonics, adding the average value of the preliminary estimates of the complex envelope of modulated harmonics to the filtered corrected preliminary estimates of the complex envelope of modulated harmonics, after generating estimates of the complex envelope of modulated harmonics multi-frequency harmonics characterization symbols generate refined estimates of the complex envelope modulated by pilot symbols of harmonics of multi-frequency information symbols, filtering the values of the estimates of the complex envelope modulated by pilot symbols of the harmonics of multifrequency information symbols, and when generating a correction value for each multifrequency information symbol, refined estimates of the complex envelope of modulated pilot are used -harmonic symbols of this multi-frequency information symbol la and their corresponding pre-specified evaluation of the complex envelope of the modulated harmonics, the final assessment of the complex envelope of the modulated information symbols harmonics for each multifrequency information symbol is formed by correcting the revised preliminary estimates of the complex envelope of the modulated harmonics using multifrequency corresponding to this information symbol correction value. 2. The method according to claim 1, characterized in that the phase of the input digital complex signal is corrected by multiplying the samples of the input digital complex signal by a complex factor of unit amplitude, the phase of which is equal to the product of the frequency shift estimate by the time positions of the samples. 3. The method according to claim 1, characterized in that the complex spectra of long multi-frequency preamble symbols are determined by the fast discrete Fourier transform of the samples of the phase-corrected input digital complex signal corresponding to these multi-frequency symbols. 4. The method according to claim 1, characterized in that the temporary position of the beginning of the long multi-frequency symbol of the preamble is defined as the sum of the temporary position of the beginning of the preamble and the a priori known temporary position of this long multi-frequency symbol relative to the beginning of the preamble. 5. The method according to claim 1, characterized in that estimates of the complex envelope of modulated harmonics of the long multi-frequency preamble symbols are formed by multiplying the components of the complex spectra of long multi-frequency preamble symbols by the complex conjugate values of the symbols modulating the corresponding harmonics. 6. The method according to claim 1, characterized in that the combination of the estimates of the complex envelope of the modulated harmonics of the long multi-frequency preamble symbols is performed by averaging the sums of the estimates of the complex envelope of the corresponding modulated harmonics of the long multi-frequency preamble symbols. 7. The method according to claim 1, characterized in that the average value of preliminary estimates of the complex envelope of modulated harmonics is formed as the ratio of the sum of preliminary estimates of the complex envelope of modulated harmonics by their number. 8. The method according to claim 1, characterized in that the corrected preliminary estimates of the complex envelope of modulated harmonics are obtained by subtracting from the preliminary estimates of the complex envelope of modulated harmonics the average value of the preliminary estimates of the complex envelope of modulated harmonics. 9. The method according to claim 1, characterized in that the estimate of the multipath interval of the input signal is formed by averaging the estimates of the multipath interval of the input signal, previously obtained from various estimates of the correlation function samples of the complex harmonic envelope, as the ratio of the difference of the estimated estimates of the correlation function of the complex harmonic envelope and parameter b to the product of the reference number, the frequency difference of the neighboring harmonics and parameter a, the parameters b and a depend on the value of the estimate of the reference of the correlation function and vlyayut the coefficients approximating broken line correlation function phase and quadrature components of the complex envelope. 10. The method according to claim 1, characterized in that the adjusted preliminary estimates of the complex envelope of the modulated harmonics are filtered by weighting the adjusted preliminary estimates of the complex envelope of the modulated harmonics, while the weighting coefficients are determined in proportion to the zero-order Bessel function of the product of the multipath of the input signal and frequency differences of harmonics. 11. The method according to claim 1, characterized in that the complex spectra of multi-frequency information symbols are determined by the fast discrete Fourier transform of the samples of the phase-corrected input digital complex signal corresponding to these multi-frequency symbols. 12. The method according to claim 1, characterized in that the temporary position of the beginning of the multi-frequency information symbol is defined as the sum of the temporary position of the beginning of the preamble, a priori known temporary position of the beginning of the OFDM symbol, a signal block including this multi-frequency symbol, relative to the beginning of the preamble and the duration of the prefix. 13. The method according to claim 1, characterized in that estimates of the complex envelope of the harmonics of the multi-frequency information symbols modulated by the pilot symbols are multiplied by multiplying the components of the complex spectra of the multi-frequency information symbols used to transmit the pilot symbols by the complex conjugate values of the pilot symbols modulating the corresponding harmonics. 14. The method according to claim 1, characterized in that the corrective value of the multi-frequency information symbol is formed as the average sum of the relations of the product of the refined estimate of the complex envelope modulated by the harmonic pilot symbol and the corresponding complex conjugate refined preliminary estimate of the complex envelope to the square of the complex envelope modulated pilot estimation module -harmonic symbol. 15. The method according to claim 1, characterized in that the final estimates of the complex envelope modulated by information symbols of the harmonics of the multi-frequency information symbol are formed by multiplying the refined preliminary estimates of the complex envelope of the modulated harmonics by a correction value corresponding to this multi-frequency information symbol. 16. The method according to claim 1, characterized in that soft decisions about information symbols are formed by multiplying the corresponding components of the complex spectra of multi-frequency information symbols by complex conjugate final estimates of the complex envelope of the harmonics of these multi-frequency information symbols modulated by information symbols.

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