RU2341905C2 - Method for data transfer and reception in system of radio communication and device for its realisation - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: in orthogonal frequency multiplexed symbols in the sections of normalised frequency, where changes of phases or normalised modules of pilot signals exceeded preset value, number of pilot signals is increased.

EFFECT: increase of noise community.

2 cl, 11 dwg

Description

The invention relates to radio engineering, in particular to a method and device for transmitting and receiving data in a radio communication system, and can be used in telecommunication systems according to the standard 802.16, as well as in other communication systems with orthogonal frequency-multiplexed signals.

In communication systems with orthogonal frequency-multiplexed signals, a sequence of binary symbols is received at the transmitting station. The sequence is broken into words. Each word is assigned a modulated data symbol in the form of a complex number. A sequence of modulated data symbols is converted into parallel groups of N modulated symbols. An inverse fast Fourier transform (IFFT) is performed with each group. Convert parallel output groups of OBPF values to a serial form and supplement them with a guard interval. Thus, the frequency multiplexed symbol represents the sum of N modulated subcarriers.

The amplitudes and phases of the subcarriers may differ from each other. However, in the time interval T _N = T _i N, where T _{i is} the sampling interval, the subcarriers have an integer number of periods and the difference in the number of periods between adjacent subcarriers is one. In this case, the subcarrier spectra overlap, and the subcarriers are orthogonal to each other.

The use of multi-position types of subcarrier modulation and overlapping spectra provides a high level of spectral efficiency of communication systems with orthogonal frequency-multiplexed signals. (Richard van Nee, Ramjee Prasad, OFDM Wireless Multimedia Communications, Artech House, Boston-London, 2000; Prokis J., Digital Communications. Translated from English, Moscow: Radio and Communications, 2000)

Frequency multiplexed symbols are converted to a radio frequency and transmitted to a receiving station, where the inverse frequency conversion of the received signal is performed.

At the receiving station, the received guard interval is removed from the received orthogonal frequency multiplexed symbols and the samples of the received symbols are converted into parallel groups. A fast Fourier transform (FFT) is performed with each group of N samples, thus forming N modulated symbols. After demodulation, a sequence of binary symbols is output to the receiving station.

Each frequency multiplexed symbol consists of N signal samples and N _GP prefix samples. The prefix samples are located before the signal samples and represent the N _{GP of the} last signal samples. The prefix duration is longer than the duration of the channel impulse response.

The use of the prefix is twofold: the presence of the prefix allows to reduce or completely eliminate intersymbol interference (it acts as a guard interval at which the multipath components of one symbol are not interference of another symbol) and also allows to reduce or completely eliminate interference between subcarriers (the prefix, making the signal periodic, supports orthogonality of subcarriers). (Richard van Nee, Ramjee Prasad, OFDM Wireless Multimedia Communications, Artech House, Boston-London, 2000; Prokis J., Digital Communications, Translated from English, Moscow: Radio and Communications, 2000)

An advantage of OFDM systems is also their resistance to frequency selective fading. Frequency selective fading affects only a certain percentage of subcarriers. These subcarriers either do not transmit data at all, or apply methods that increase the noise immunity of data transmission at these frequencies (coding, adaptation of the data transfer rate to the signal-to-noise ratio in the band affected by the fading, etc.). (Richard van Nee, Ramjee Prasad, OFDM Wireless Multimedia Communications, Artech House, Boston-London, 2000.)

In communication systems with orthogonal frequency multiplexed signals, pilot signals are used for coherent data reception. As a rule, the distance between the pilot signals in the frequency domain is (N _F +1) Δf, where N _F is the number of modulated data symbols located between the pilot signals in the frequency domain, and Δf is the frequency shift between subcarriers of the orthogonal frequency multiplexed symbol, choose so that the inequality holds

where τ _{max is the} maximum signal delay in the multipath channel. (Richard van Nee, Ramjee Prasad, OFDM Wireless Multimedia Communications, Artech House, Boston-London, 2000.)

There are various methods and devices for transmitting and receiving data in a radio communication system with orthogonal frequency multiplexed signals and devices for their implementation, for example, the method and device described in the article [Michele Morelli and Umberto Mengali. A comparison of pilot-aided channel estimation methods for OFDM systems. IEEE transactions on signal processing, vol. 49, no.12, December 2001].

In this method, a sequence of modulated data symbols and a pilot signal is transmitted to the transmitting station. In this case, the pilot signal is repeated every N _f modulated data symbols.

The sequence of modulated data symbols and the pilot signals are converted into parallel groups of modulated and pilot symbols, each of which consists of Q modulated symbols and K pilot signals.

Groups of modulated symbols and pilot signals are supplemented with sequences consisting of Z zero symbols, placing them at the beginning and end of the group. Moreover, N = Q + K + 2Z.

Each group performs the inverse fast Fourier transform, then IFFT, forming parallel output groups of IFFT values.

Convert the parallel output groups of IFFT values into serial form, thus forming a sequence of transmitted characters, each of which contains N received IFFT values.

Each transmitted symbol is supplemented with a guard interval, thus forming a sequence of orthogonal frequency multiplexed symbols.

A sequence of orthogonal frequency multiplexed symbols is transmitted to the receiving station.

At the receiving station, they are received and the guard interval is removed, thus forming a sequence of received symbols.

Convert received characters to parallel groups of input values.

An FFT is performed with each group of input values, thus forming N modulated symbols in each group.

In each group, the pilot channel estimates the communication channel.

Using the obtained communication channel estimation results, demodulation of the obtained estimates of modulated data symbols is performed, thus forming a sequence of binary data.

A device that implements the method in question comprises a transmitting station and a receiving station. The transmitting station contains a block of serial-parallel conversion of a sequence of modulated data symbols and a pilot signal into parallel groups, a block for supplementing these parallel blocks with sequences of zero symbols, an IFFT block, a parallel-serial conversion unit (serialization of parallel output groups of IFFT values), and an attachment block guard interval (supplement of each transmitted character with a guard interval). The receiving station contains a series-parallel-parallel conversion unit (converting received characters into parallel groups of input values), a guard interval removal unit, an FFT unit, a channel estimation unit, and a demodulation unit.

In a multipath channel with frequency selective fading, the signal spectrum is uneven. Moreover, the phase and the modulus of the spectral components in the narrow parts of the spectrum relative to the signal band varies widely. Consider an example.

Figure 1 shows the spectrum of a single-beam signal of the return channel according to the 802.16 standard, obtained by modeling, with the following parameters: FFT size is 1024, the signal band is 10 MHz, the duration of the orthogonal frequency multiplexed symbol with a guard interval Ts is 100.8 μs, the type of modulation - quadrature amplitude 16 position modulation (16-QAM), the transmitted information consists of "zero bits". This figure shows that the signal spectrum without fading is uniform.

Figure 2 and 3 shows, obtained by modeling, the moduli of spectra of multipath signals with the above parameters at a fading frequency of 200 Hz. The signal spectrum during fading is uneven. Moreover, the modulus of the spectral components in the narrow sections of the frequency relative to the signal bandwidth varies approximately from minimum to maximum values. If the pilot signals are evenly distributed over frequency areas where the spectrum varies widely, the accuracy of the estimation of the phase and amplitude of the pilot signals may be impaired.

Closest to the claimed invention is the method described in the article by Sinem Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai. Channel estimation techniques based on pilot arrangement in OFDM systems. IEEE transactions on broadcasting, vol. 48, no.3, September 2002. The prototype method is as follows.

The transmitting station receives a sequence of binary characters. The sequence is divided into words consisting of d characters, where d is a given number.

Each word is assigned a modulated data symbol in the form of a complex number.

Convert a sequence of modulated data symbols into parallel groups of modulated symbols.

In parallel groups of modulated symbols, pilot signals are placed between the modulated data symbols, thus forming a sequence of groups, each of which consists of N modulated symbols, N = Q + K, where Q is the number of modulated data symbols in the parallel group, K is the number Signal pilot in parallel group.

OBPFs are performed with each group, forming parallel output groups of OBPF values.

Supplement each block of OBPF values with a guard interval.

Convert parallel blocks of OBPF values with a guard interval into a serial form, thus forming a sequence of orthogonal frequency multiplexed symbols.

A sequence of orthogonal frequency multiplexed symbols is transmitted to the receiving station.

At the receiving station, they are received, converted into parallel blocks of input values and the guard interval is removed.

A fast Fourier transform is performed with each group of input values, thus forming N modulated symbols in each group.

An FFT is performed with each group of input values, thus forming N modulated symbols in each group.

In each group, the pilot channel estimates the communication channel.

Using the obtained results of the evaluation of the communication channel, an evaluation of the modulated data symbols is performed, forming groups of estimates of the modulated data symbols.

The group of estimates of modulated data symbols is converted into a serial form, thus forming a sequence of estimates of modulated data symbols.

Demodulation of the obtained estimates of the modulated data symbols is performed, thus forming a sequence of binary data.

The structural diagram of a device that implements the prototype method described above is made in FIG.

The prototype device (figure 4) contains a transmitting station 1 and a receiving station 2, which are connected via a communication channel 3, while the input of the transmitting station 1 is the input of the device, the output of the receiving station is the output of the device, the output of the transmitting station 1 is connected to the input of the receiving station 2 through communication channel 3,

the transmitting station 1 contains a modulator 4, a serial-parallel conversion unit 5, a pilot signal installation unit 6, an inverse fast Fourier transform unit 7, a guard interval 8 attachment unit, a parallel-serial conversion unit 9, a transmitter 10, while the input of the modulator 1 is an input transmitting station 1, the output of modulator 1 is connected to the input of the serial-parallel conversion unit 5, the outputs of which are connected to the inputs of the installation block of the pilot signal 6, the outputs of which are connected to Dams of the inverse fast Fourier transform block 7, the outputs of which are connected to the inputs of the attachment block of the guard interval 8, the outputs of which are connected to the inputs of the parallel-serial conversion block 9, the output of which is connected to the input of the transmitter 10, the output of which is the output of the transmitting station and connected to the channel input communication 3,

the receiving station 2 comprises a receiver 11, a serial-parallel conversion unit 12, a guard interval removal unit 13, a fast Fourier transform unit 14, a channel estimator 15, a parallel-serial conversion unit 16 and a demodulator 17, while the input of the receiver 11 is the input of the receiving station 2, which is connected to the output of the communication channel 3, the output of the receiver 11 is connected to the input of the serial-parallel conversion unit 12, the outputs of which are connected to the inputs of the removal unit of the guard interval 13, the outputs of orogo connected to the inputs of a fast Fourier transform unit 14, the outputs of which are connected to the inputs of the channel estimation unit 15, which outputs are connected to the inputs of a block parallel-to-serial conversion 16, whose output is connected to the input of a demodulator 17 whose output is the output of the receiving station.

The device (figure 4) that implements the prototype method, works as follows.

The transmitting station 1 receives a sequence of binary characters. In modulator 4, a sequence of binary characters is divided into words consisting of d characters, where d is a given number. Each word is assigned a modulated data symbol in the form of a complex number.

In the series-parallel conversion unit 5, the sequence of modulated data symbols is converted into parallel groups of modulated symbols.

In the installation block of the pilot signals 6, pilot signals are arranged in parallel groups of modulated symbols between the modulated data symbols, thus forming a sequence of groups, each of which consists of N modulated symbols, N = Q + K, where Q is the number of modulated data symbols in parallel group, K is the number of pilot signals in the parallel group.

In block OBPF 7 with each group perform OBPF, forming parallel output groups of values OBPF.

In the attachment block of the guard interval 8, the parallel output groups of IFFT values are supplemented with a guard interval.

In the parallel-serial conversion unit 9, parallel output groups of IFFT values with a guard interval are converted into a serial form, thereby forming a sequence of orthogonal frequency multiplexed symbols.

A sequence of orthogonal frequency-multiplexed symbols is transmitted from the output of the transmitter 10 via the communication channel 3 to the receiving station 2.

At the receiving station 2, they are received through the communication channel 3 in the receiver 11, and the received frequency-multiplexed symbols are converted into parallel groups of input values in the serial-parallel conversion unit 12.

In the guard interval removal unit 13, the guard interval is deleted.

An FFT is performed with each group of input values in the FFT block 14, thus forming N modulated symbols in each block.

In the channel estimator 15 in each group, the channel estimation is performed by the pilot signals. Using the obtained results of the evaluation of the communication channel, an evaluation of the modulated data symbols is performed, forming groups of estimates of the modulated data symbols.

In the block parallel-sequential conversion 16 transform the group of estimates of modulated data symbols in serial form, thus forming a sequence of estimates of modulated data symbols.

In the demodulator 17, demodulation of the obtained estimates of the modulated data symbols is performed, thus forming a sequence of binary data that is output from the demodulator 17 to the output of the receiving device 2.

It is known that the signal spectrum during fading is uneven. Moreover, the phase and the modulus of the spectral components in narrow sections of the frequency relative to the signal bandwidth varies widely. If the pilot signals are evenly distributed over relatively narrow frequency sections, where the phase and spectrum modulus vary approximately from minimum to maximum values, the accuracy of estimating the phase and amplitude of the pilot signals deteriorates and, therefore, noise immunity in a communication system with orthogonal frequency multiplexing deteriorates.

Therefore, in the frequency domain, in parts of the signal spectrum, where the magnitude of the change in the spectrum varies widely, the number of pilot symbols must be proportional to the magnitude of the change in the values of the modules or phases of the pilot symbols, which is proposed to be performed in the claimed invention.

The objective of the invention is to increase noise immunity in communication systems with orthogonal frequency multiplexing.

The problem is solved by the claimed method of data transmission-reception in a radio communication system and device for its implementation.

The inventive method of transmitting / receiving data in a radio communication system is that

a sequence of binary characters arrives at the transmitting station. The sequence is divided into words consisting of d characters, where d is a given number,

each word is assigned a modulated data symbol in the form of a complex number,

transform a sequence of modulated data symbols into parallel groups of modulated symbols,

complement the groups of modulated data symbols with sequences consisting of Z zero symbols, positioning them at the beginning and end of the group, and every N _f modulated data symbols have a pilot signal, where N _f = Q / K, and Q is a multiple of K and N = Q + 2Z + K, and K is the number of pilot signals,

OBPF is performed with each group of the generated sequence, forming parallel output groups of OBPF values,

converting parallel output blocks of OBPF values into serial form, thus forming a sequence of transmitted characters, each of which contains N received consecutive OBPF values,

supplement each transmitted symbol with a guard interval, thus forming a sequence of orthogonal frequency multiplexed symbols,

transmitting a sequence of orthogonal frequency multiplexed symbols to a receiving station;

at the receiving station, they are received and the guard interval is removed, thus forming a sequence of received symbols,

convert the received characters into parallel groups of input values,

FFT is performed with each group of input values, thus forming parallel groups of modulated symbols, consisting of N modulated symbols each,

associate with each modulated symbol the frequency of the subcarrier normalized to the frequency shift between the subcarriers, and the frequency of the subcarrier is equal to its serial number in the group, taking a value from 1 to N,

isolate and store in groups modulated data symbols and pilot signals, as well as their normalized frequencies,

in each group, the modules and phases of the pilot signals are calculated,

determine the maximum value of the pilot signal module in each group and normalize the calculated pilot signal modules to the maximum value of the pilot signal module of this group,

in each group, for all subcarriers with pilot signals, the pilot signals are calculated in a sliding window of a given size of the phase changes of the pilot signals as the ratio of the phase difference of the pilot signals at the beginning and at the end of the window to the difference of the normalized frequencies corresponding to them, and the subcarrier for which the pilot phase changes are calculated signals, is the center of the window,

in each group for all subcarriers with pilot signals, the changes in the normalized modules of the pilot signals are calculated in a sliding window of a given size as the ratio of the difference between the modules of the pilot signals corresponding to the beginning and end of the window to the difference of the normalized frequencies corresponding to them, and the subcarrier corresponding to the calculated change in the normalized modules of the pilot signals, is the center of the window,

the calculated changes in the phases and the normalized modules of the pilot signals are compared with the specified values of the changes in the phase and the module and remember the first and last values of the selected sections of the normalized frequency where the specified values are exceeded, and changes in the normalized modules and phases of the pilot signals in this section,

calculate the average values of the phases and the normalized modules of the pilot signals in the selected sections of the normalized frequency, where there has been an excess of phase changes or the normalized modules of the pilot signals of specified values,

if the average value is a fractional number, then it is rounded to an integer,

from the calculated average values of the phases and modules of the pilot signal changes, the adjusted number of modulated symbols between the pilot signals is determined for the corresponding allocated sections of the normalized frequency so that the number of modulated symbols between the pilot signals is proportional to the magnitude of the phase changes or the normalized pilot signal modules,

if at some intervals the selected sections of the normalized frequency, on which the adjusted number of modulated symbols between the pilot signals are determined, overlap, then at these intervals the maximum is selected from the two adjusted numbers of modulated symbols between the pilot signals,

transmit from the receiving station to the transmitting station the first and last values of the allocated sections of the normalized frequency, as well as the adjusted number of modulated symbols between the pilot signals in each of these sections;

at the receiving station, pilot signals are used to evaluate the communication channel,

using the obtained results of the evaluation of the communication channel, perform an assessment of Q modulated data symbols,

converting the group of estimates of the modulated data symbols in serial form, thus forming a sequence of estimates of modulated data symbols,

perform demodulation of the obtained estimates of the modulated data symbols, thus forming a sequence of binary data;

at the transmitting station, the first and last values of the allocated sections of the normalized frequency are received, where there has been an excess of phase changes or normalized modules of the pilot signals of specified values, as well as the adjusted number of modulated symbols between the pilot signals in each of these sections, and the number of modulated symbols is adjusted in accordance with them between pilot signals.

The inventive device for transmitting / receiving data in a radio communication system, contains a transmitting and receiving station,

wherein the transmitting station contains a modulator, an inverse fast Fourier transform unit, a parallel-serial conversion unit, a guard interval attachment unit, a transmitter, a receiver, a splitter and an antenna, while the input of the modulator is the first input of the transmitting station — an input of a sequence of binary symbols, the output of the transmitter is connected with the first input of the splitter, the first output of which is connected to the first input of the antenna, the first output of which is the first output of the transmitting station transmitting from Vågå output radio frequency frequency-multiplexed symbols, a second input of the antenna is the second input of the transmitting station-input frequency-multiplexed symbols transmitted on the radio frequency from the transmitting station, the second antenna output is connected to the second input coupler, the second output of which is connected to the receiver input;

the receiving station contains an antenna, a splitter, a receiver, a transmitter, a block of parallel-parallel conversion and removal of the guard interval, a fast Fourier transform block, a channel estimation block, a parallel-serial conversion block and a demodulator, while the first input of the antenna is the first input of the receiving station, the input frequency-multiplexed symbols on the radio frequency, the first output of the antenna is connected to the first input of the splitter, the first output of which is connected to the input of the receiver, the output of which ohm is connected to the first input of the serial-parallel conversion unit and removing the guard interval, the outputs of which are connected respectively to the inputs of the fast Fourier transform unit, the outputs of which are connected to the inputs of the channel estimator, the outputs of which are connected to the inputs of the parallel-serial conversion unit, the output of which is connected to the input of the demodulator, the output of which is the first output of the receiving station, forming a sequence of binary data on this output, the output of the transmitter ka is connected to the second input coupler, the second output of which is connected to the second input of the antenna, the second output of which is the second output of the receiving station,

according to the invention:

at the transmitting station, a pilot signal alignment block is introduced, the first input of which is connected to the modulator output, the second input of the pilot signal alignment block is combined with the first input of the guard interval attachment unit, forming the third input of the transmitting station, which is the input of the initial setting signal, the third, fourth and fifth the inputs of the pilot signal arrangement block are connected respectively to the first, second, and third outputs of the receiver, which forms the first values of the selected sections of the normalized simplicity, the second output - the last value selected portions of the normalized frequency at the output of the third - the number of corrected modulation symbols between pilot signals in each of the selected portions,

the outputs of the pilot signal alignment unit are connected to the inputs of the IFFT unit, the outputs of which are connected to the inputs of the parallel-serial conversion unit, the output of which is connected to the second input of the guard interval connection unit, the output of which is connected to the transmitter input;

at the receiving station are entered:

a unit for calculating the magnitude of changes in the values of the normalized modules and phases of the pilot signals and determining the selected sections of the normalized frequency and the block for generating a signal of the return channel

the outputs of the fast Fourier transform unit are connected to the first inputs of the unit for calculating the changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency, which forms the first values of the selected sections of the normalized frequency at the first output, and the last values of the selected sections of the normalized frequency at the second output , on the third output, the adjusted number of modulated symbols between the pilot signals in each selected portion of the normalized frequency, the first, second and third outputs of the unit for calculating the magnitude of changes in the values of the normalized modules and phases of the pilot signals and determining the allocated sections of the normalized frequency are connected respectively to the first, second and third inputs of the unit for generating the signal of the return channel, the output of which is connected to the input of the transmitter, the second inputs of the unit for calculating the values changes in the values of the normalized modules and phases of the pilot signals and the definition of the selected sections of the normalized frequency and block serial-parallel conversion and removing the guard interval are combined to form a second input of the receiving station, which is the input signal the initial installation.

A comparison of the proposed method with the prototype shows that the inventive method has the following distinctive features, namely:

at the transmitting station in each group, the modules and phases of the pilot signals are calculated,

determine the maximum value of the pilot signal module in each group and normalize the calculated pilot signal modules to the maximum value of the pilot signal module of this group,

in each group, for all subcarriers with pilot signals, the pilot signals are calculated in a sliding window of a given size of the phase changes of the pilot signals as the ratio of the phase difference of the pilot signals at the beginning and at the end of the window to the difference of the normalized frequencies corresponding to them, and the subcarrier for which the pilot phase changes are calculated signals, is the center of the window,

in each group for all subcarriers with pilot signals, the changes in the normalized modules of the pilot signals are calculated in a sliding window of a given size as the ratio of the difference between the modules of the pilot signals corresponding to the beginning and end of the window to the difference of the normalized frequencies corresponding to them, and the subcarrier corresponding to the calculated change in the normalized modules of the pilot signals, is the center of the window,

the calculated changes in the phases and the normalized modules of the pilot signals are compared with the specified values of the changes in the phase and the module and remember the first and last values of the selected sections of the normalized frequency where the specified values are exceeded, and changes in the normalized modules and phases of the pilot signals in this section,

calculate the average values of the phases and the normalized modules of the pilot signals in the selected sections of the normalized frequency, where there has been an excess of phase changes or the normalized modules of the pilot signals of specified values,

if the average value is a fractional number, then it is rounded to an integer,

from the calculated average values of the phases and modules of the pilot signal changes, the adjusted number of modulated symbols between the pilot signals is determined for the corresponding allocated sections of the normalized frequency so that the number of modulated symbols between the pilot signals is proportional to the magnitude of the phase changes or the normalized pilot signal modules,

if at some intervals the selected sections of the normalized frequency, on which the adjusted number of modulated symbols between the pilot signals are determined, overlap, then at these intervals the maximum is selected from the two adjusted numbers of modulated symbols between the pilot signals,

transmit from the receiving station to the transmitting station the first and last values of the allocated sections of the normalized frequency, as well as the adjusted number of modulated symbols between the pilot signals in each of these sections;

at the transmitting station, the first and last values of the allocated sections of the normalized frequency are received, where there has been an excess of phase changes or normalized modules of the pilot signals of specified values, as well as the adjusted number of modulated symbols between the pilot signals in each of these sections, and the number of modulated symbols is adjusted in accordance with them between pilot signals.

A patent and scientific and technical search by the prior art and comparative analysis did not reveal these signs in analogues.

New in the inventive device for transmitting / receiving data in a radio communication system is:

on the transmitting side, a pilot signal placement unit has been introduced and, accordingly, new communications providing the implementation of all the method features on the transmitting side,

on the receiving side, a block for calculating the values of changes in the values of the normalized modules and phases of the pilot signals and determining the allocated frequency sections and a block for generating the signal of the return channel, as well as new communications, which ensure the implementation of all the features of the method on the receiving side, are introduced.

EFFECT: increased noise immunity in communication systems with orthogonal frequency multiplexing, is achieved by implementing all the features of the claimed invention.

Further, the description of the invention is illustrated by examples and drawings.

Figure 1 shows the spectrum of a single-beam signal of the reverse channel according to the standard 802.16 obtained by simulation.

Figure 2 and 3 shows the modules of the spectra of multipath signals at a fading frequency of 200 Hz, obtained by simulation.

Figure 4 is a structural diagram of a prototype device.

Figure 5 is a structural diagram of the inventive device is a transmitting station.

Figure 6 is a structural diagram of the inventive device is a receiving station.

7 is an example of a temporal structure of orthogonal frequency multiplexed symbols.

On Fig is a structural diagram of the block connecting the protective interval, shown as an example implementation.

Figure 9 is a structural diagram of the arrangement of the pilot signals, shown as an example implementation.

Figure 10 is a structural diagram of a block serial-parallel conversion and removal of the guard interval, shown as an example implementation.

Figure 11 is a structural diagram of a unit for calculating changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency, is given as an example implementation.

The inventive device for transmitting / receiving data in a radio communication system, contains transmitting 1 (Fig. 5) and receiving 2 (Fig. 6) stations,

wherein the transmitting station 1 (Fig. 5) contains a modulator 4, an inverse fast Fourier transform unit 7, a parallel-serial conversion unit 9, a guard interval 8 attachment unit, a transmitter 10, a receiver 18, a splitter 19, and an antenna 20, while the modulator input 4 is the first input of the transmitting station 1 - the input of a sequence of binary characters, the output of the transmitter 10 is connected to the first input of the splitter 19, the first output of which is connected to the first input of the antenna 20, the first output of which is the first output of the transmitter station 1, transmitting frequency-multiplexed symbols from the first output on the radio frequency, the second input of the antenna 20 is the second input of the transmitting station 1, the input of frequency-multiplexed symbols transmitted on the radio frequency from the transmitting station, the second output of the antenna 20 is connected to the second input of the splitter 19, the second output of which is connected to the input of the receiver 18;

according to the invention

at the transmitting station, a pilot signal placement unit 25 is introduced, the first input of which is connected to the output of the modulator 4, the second input of the pilot signal placement unit 25 is combined with the first input of the guard interval 8 attachment unit, forming the third input of the transmitting station 1, which is the input of the initial setting signal, the third, fourth and fifth inputs of the block of arrangement of the pilot signals 25 are connected respectively to the first, second and third outputs of the receiver 18, forming on the first output the first values of the selected sections of the normal frequency, at the second output - the last values of the selected sections of the normalized frequency, at the third output - the adjusted number of modulated symbols between the pilot signals in each of the selected sections, the outputs of the pilot signal spacing unit 25 are connected to the inputs of the inverse Fourier transform unit 7, the outputs of which are connected to the inputs of the block of parallel-serial conversion 9, the output of which is connected to the second input of the block connecting the protective interval 8, the output of which is connected to the input before tchika 10;

the receiving station 2 (FIG. 6) comprises an antenna 24, a splitter 23, a receiver 11, a transmitter 22, a serial-parallel conversion and removal of the guard interval 21, a fast Fourier transform unit 14, a channel estimation unit 15, a parallel-serial conversion unit 16, and demodulator 17, while the first input of the antenna 24 is the first input of the receiving station 2 - the input of frequency-multiplexed symbols, the first output of the antenna 24 is connected to the first input of the splitter 23, the first output of which is connected to the input of the receiver 11, the output of which is connected to the first input of the serial-parallel conversion and removal of the guard interval 21, the outputs of which are connected respectively to the inputs of the fast Fourier transform unit 14, the outputs of which are connected to the inputs of the channel estimator 15, the outputs of which are connected to the inputs of the parallel-serial block conversion 16, the output of which is connected to the input of the demodulator 17, the output of which is the first output of the receiving station 2, forming at this output a sequence of binary OF DATA, the transmitter output 22 is connected to the second input coupler 23, a second output is connected to the second input of the antenna 24, which second output is the second output of the receiving station 2,

according to the invention:

at the receiving station 2 introduced:

a unit for calculating the magnitude of changes in the values of the normalized modules and phases of the pilot signals and determining the selected sections of the normalized frequency 26 and a signal generating unit for the return channel 27,

the outputs of the fast Fourier transform unit 14 are connected to the first inputs of the unit for calculating the changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency 26, which forms the first values of the selected sections of the normalized frequency at the first output, and the last values of the selected sections at the second output normalized frequency, on the third output - the adjusted number of modulated symbols between the pilot signals in each selected section of the normalized frequency you, the first, second and third outputs of the unit for calculating the changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency 26 are connected respectively to the first, second and third inputs of the signal conditioning unit of the return channel 27, the output of which is connected to the input of the transmitter 22, the second inputs of the unit for calculating the magnitude of the changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency 26 and the serial-parallel block mation and removing the guard interval 21 together, forming a second input of the receiving station 2, which is the input signal the initial installation.

Consider in detail how to implement the inventive method of transmitting and receiving data in a radio communication system on a device whose structural diagram is made in figure 5 and 6.

The first input of the transmitting station 1 (figure 5) receives a sequence of binary characters. From the first input of the transmitting station 1, the sequence of binary symbols is input to the modulator 4. In modulator 4, the sequence is divided into words consisting of d characters, where d is a given number. Each word is assigned a modulated data symbol in the form of a complex number. From the output of modulator 4, the signal is supplied to the first input of the pilot signal arrangement 25, to the second input of which the initial setting signal is received.

In the arrangement of the pilot signal arrangement 25, the sequence of modulated symbols is converted into parallel groups of modulated symbols and supplemented with sequences of Z zero symbols, positioning them at the beginning and end of the group, and after each N _f modulated data symbols, a pilot signal is located, where N _f = Q / K, with Q being a multiple of K and Q + 2Z + K = N, and K is the number of pilot signals.

In block OBPF 7 with each group perform OBPF, forming parallel output groups of values OBPF, which from the output of block 7 are fed to the inputs of the block parallel-serial conversion 9.

In the parallel-serial conversion unit 9, parallel output groups of IFFT values are converted into a serial form, thus forming a sequence of transmitted symbols, each of which contains N received IFFT values, which from the output of block 9 go to the second input of the attachment block of the guard interval 8, the first input of which receives the initial setup signal.

In the attachment unit of the guard interval 8, each transmitted symbol is supplemented with a guard interval, thereby forming a sequence of orthogonal frequency multiplexed symbols.

Frequency multiplexed symbols from the output of the attachment unit of the guard interval 8 are fed to the input of the transmitter 10. The output signal of the transmitter through the first input of the splitter is fed to the antenna 20. Thus, the multiplexed symbols are transmitted to the receiving station.

At the receiving station 2 (Fig.6), the signal from the antenna 24 through the first input of the splitter 23 from the first output is fed to the input of the receiver 11.

In the receiver 11 perform amplification, frequency selection, frequency signal conversion, frequency and time synchronization.

From the output of the receiver 11, the frequency-multiplexed symbols are fed to the first input of the serial-parallel conversion block and the removal of the guard interval 21, to the second input of which the initial setting signal is received.

In the block of serial-parallel conversion and removal of the guard interval 21, the guard interval is removed and the received symbols are converted into parallel groups of input values, which from the outputs of block 21 go to the inputs of the FFT unit 14.

An FFT is performed with each group of input values in the FFT block 14, thus forming N modulated symbols in each group.

The output values of the FFT unit 14 are supplied to the inputs of the channel estimator 15 and the inputs of the unit for calculating the magnitudes of changes in the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency 26.

In the channel estimator 15 in each group, the channel estimation is performed by the pilot signals. Using the obtained results of the evaluation of the communication channel, an evaluation of the modulated data symbols is performed, forming groups of estimates of the modulated data symbols, which are output from the outputs of block 15 to the inputs of the block of parallel-serial conversion 16.

In the block parallel-sequential conversion 16 convert the group of estimates of modulated data symbols in serial form, thus forming a sequence of estimates of modulated data symbols, which from the output of block 16 are fed to the input of demodulator 17.

In the demodulator 17, demodulation of the obtained estimates of the modulated data symbols is performed, thus forming a sequence of binary data that is received at the first output of the receiving station 2.

In the unit for calculating the magnitude of the changes in the values of the normalized modules and phases of the pilot signals and determining the allocated sections of the normalized frequency 26, the changes in the values of the normalized modules and phases of the pilot signals are calculated, compared with the set values, the first and last values of the selected sections of the normalized frequency are stored, where the set values are exceeded , and determine in these areas the corrected number of modulated symbols between the pilot signals. Thus, block 26 generates at the first output the first values of the selected sections of the normalized frequency, at the second output - the last values of the selected sections of the normalized frequency, at the third output - the adjusted number of modulated symbols between the pilot signals in each selected section of the normalized frequency, which, respectively, from the first, the second and third outputs are fed to the first, second and third inputs of the signal conditioning unit of the return channel 27.

In the block for generating the signal of the return channel 27, the calculated first and last values of the selected sections of the normalized frequency, as well as the adjusted number of modulated symbols between the pilot signals in each of these sections, are converted into frequency-multiplexed symbols that are received from the output of the block for the formation of the signal of the return channel 27 at the input of the transmitter 22. The output signal of the transmitter 22 through the second input of the splitter 23 is fed to the second input of the antenna 24. The output signal is transmitted from the second output of the antenna 24.

At the transmitting station 1 (Fig. 5), the first and last values of the allocated sections of the normalized frequency are received, where there has been an excess of phase changes or normalized modules of the pilot signals of predetermined values, as well as the adjusted number of modulated signals between the pilot signals in each of these sections, and in accordance with them in the block of arrangement of the pilot signals 25 adjust the number of modulated symbols between the pilot signals.

The initial setup signal, as a rule, is supplied to all devices of the receiving and transmitting stations. However, this signal is not essential for understanding the operation of the device, and therefore it is indicated only on electrical circuits, and on a structural diagram this signal is not indicated. In figure 5 and figure 6 for a better understanding of the operation of the device, such a signal is indicated.

For a better understanding of the operation of the proposed method for transmitting and receiving data in a radio communication system and device for its implementation, we will now consider examples of the execution of blocks included in the transmitting and receiving stations of the claimed device.

Block parallel-serial conversion 16 can be performed in the form of a parallel-serial register. Modulated characters are written to the register in parallel, and read sequentially.

The channel estimator 15 may be implemented in various ways. For example, channel estimation by pilot signals may be performed as described in [Michele Morelli and Umberto Mengali. A comparison of pilot-aided channel estimation methods for OFDM systems. IEEE transactions on signal processing, vol. 49, no.12, December 2001] and [Sinem Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai. Channel estimation techniques based on pilot arrangement in OFDM systems. IEEE transactions on broadcasting, vol. 48, no.3, September 2002]. It is easiest to implement the above procedure for channel estimation by pilot signals on a microprocessor.

Examples of FFT 14 and OBPF 7 blocks are given in the book [Digital Filters and Signal Processing Devices on Integrated Circuits. Ed. B. F. Vysotsky, M .: Radio and communications, 1984], in the patent of the Russian Federation [No. 2012051 "Device for fast Fourier transform", IPC ⁵ G06F 15/352 (publication date - 1994.04.30)] and in the article [ Jaesung Lee, Jeonghoo Lee, Myung H. Sunwoo, Sangman Moh, and Seongkeun Oh A DSP Architecture for High-Speed FFT in OFDM Systems. ETRI Journal, Volume 24, Number 5, October 2002]. The FFT block 7 can be implemented on the basis of a signal microprocessor (for example, from the TMS 320 series) or a microprocessor for fast Fourier transform of 1815VFZ.

The operation of attaching the guard interval is illustrated in Fig.7. In figure 7, the time interval corresponding to the guard interval is indicated as T _g , and the transmitted symbol T _N. For example, for 802.16, the guard interval is T _g = 11.2 μs (128 samples), and the duration of the transmitted symbol is T _N = 89.6 μs (1024 samples). Figure 7 shows that the attachment of the guard interval consists in the fact that after IFFT and parallel-serial conversion, the last G of N samples of the transmitted symbol are repeated at the beginning of this symbol. Thus, the orthogonal frequency multiplexed symbol consists of G + N samples.

The attachment unit of the guard interval 8 can, for example, be implemented according to the block diagram shown in FIG.

The attachment block of the guard interval 8 (Fig. 8) contains the first 28, second 29, third 30, fourth 31, fifth 32, sixth 33, seventh 34 and eighth 35 gates And, the first 36 and second 37 registers, the first 38, second 39 and the third 40 logical gates OR, counter 41, clock 42, and trigger 43, while the first inputs of the first 28 and second 29 logic gates And are combined to form the second input of block 8, the outputs of the first 28 and second 29 logic gates And are connected respectively with the first inputs of the first 36 and second 37 registers, the first outputs to which are connected respectively to the first inputs of the third 30 and fourth 31 logic gates And, G of the second parallel outputs of the first 36 registers are connected to the second G inputs of this register, G of the second parallel outputs of the second 37 registers are connected to the second G inputs of this register, the second input of the third logical element And 30 is combined with the second input of the second logical element And 29 and the first inputs of the sixth 33 and seventh 34 of the logical elements And and are connected to the first output of the trigger 43, the second output of which is connected to the second the inputs of the first 28 and fourth 31 logic gates And and the first inputs of the fifth 32 and eighth 35 logic gates And, the first input of the trigger 43 is combined with the first inputs of the counter 41 and the clock generator 42, forming the first input of block 8, which is the input of the initial setting signal, the first output of the clock 42 is connected to the second inputs of the counter 41, fifth 32 and the seventh 34 logic elements And, the second output of the clock 42 is connected to the second inputs of the sixth 33 and eighth 35 logic elements in AND, the outputs of the eighth 35 and seventh 34 logic gates AND are connected respectively to the first and second inputs of the third logical element OR 40, the outputs of the sixth 33 and fifth 32 logic gates AND are connected respectively to the first and second inputs of the second logical element OR 39, the output of the counter 41 connected to the second input of the trigger 43 and the third inputs of the first 36 and second 37 registers, the fourth input of the first register 36 is connected to the output of the second logical element OR 39, the fourth input of the second register 37 is connected to the output of the third logical element OR 40, the outputs of the third 30 and fourth 31 logical elements AND are connected respectively to the first and second inputs of the first logical element OR 38, the output of which is the output of block 8.

Moreover, the clock generator 42 comprises a clock driver and a divider. Thus, to the first output, the clock generator 42 generates an output signal from the driver of clock pulses, and to the second output, the signal from the divider.

The block connecting the protective interval (Fig) is as follows.

The input samples of the transmitted symbol come from the second input of block 8 to the first inputs of the first 28 and second 29 logic gates I. From the first outputs of the first 28 and second 29 logic gates AND the input samples of the transmitted symbol arrive alternately respectively at the first inputs of the first 36 and second 37 registers and sequentially written respectively in the first 36 or second 37 registers.

Then, the recorded samples of the transmitted symbol from the outputs of the first 36 and second 37 registers are supplied to the first inputs of the third 30 and fourth 31 logical elements AND, the outputs of which are alternately fed respectively to the first and second inputs of the first logical element OR 38, from the output of which they go to the output of the block 8. That is, if samples are recorded in the first register 36, then read from the second register 37 and, conversely, if samples are recorded in the second register 37, then they are read from the first register 36. The read rate is greater than the write frequency. Moreover, after writing to the register of samples of one transmitted symbol, the last G of N samples are written in the register at the beginning of this symbol.

Using the counter 41, trigger 43, fifth 32, sixth 33, seventh 34 and eighth 35 logic gates AND, second 39 and third 40 logic gates OR, clock pulses and control signals for the first 28, second 29 are generated from clock pulses of the clock generator 42 , the third 30 and the fourth 31 logical elements And, the first 36 and second registers, which are fed to the second inputs of these elements. Moreover, the read clock pulses come from the first output of the clock generator 42, and the write clock pulses come from the second output of the clock generator 42. In this case, the counter 41 determines the duration of the recording interval of the samples of the transmitted symbol in the register. The initial setup signal, which comes from the first input of block 8, performs the initial setup of the clock 42, counter 41, and trigger 43.

Block arrangement of the pilot signals 25 can be performed, for example, according to the structural diagram shown in Fig.9.

The pilot signal arrangement 25 (Fig. 9) contains the first 44, the second 45, and the third 46 logical elements AND, the first 47 and second 48 logical elements OR, the first 49 and second 50 read-only memory (ROM), the first 51, the second 52, and the third 53 random access memory (RAM), the first 54 and second 55 comparison circuits, the first 56 and second 57 counters, trigger 58, clock 59 (GTI), register 60, while the first input of the first logical element And 44 is the first input block 25 - input modulated characters, the second input of the first logical of the element And 44 is connected to the first output of the first counter 56, the second output of which is connected to the first input of the second logical element And 45 and the input of the first ROM 49, the output of which is connected to the second input of the second logical element And 45, the output of which is connected to the second input of the first logical OR element 47, the first input of which is connected to the output of the first logical element AND 44, the output of the first logical element OR 47 is connected to the input of the register 60, the outputs of which are the outputs of block 25, the input of the second ROM 50 and the first input of the logical OR gate 48 are combined and connected to the output of the third logical gate AND 46, the output of the second ROM 50 is connected to the second input of the second logical gate OR 48, the output of which is connected to the first input of the first counter 56, the second input of which is combined with the first inputs of the second RAM 52 and a trigger 58 and connected to the output of the first comparison circuit 54, the third input of the first counter 56 is combined with the first inputs of the clock generator (GTI) 59 and the second counter 57, forming the second input of block 25, which is the signal input initial installation, the fourth input of the first 56 and the second input of the second 57 counters are connected to the output of the GTI 59, the input of the first RAM 51 is the fifth input of block 25 - the input of the adjusted number of modulated signals between the pilot signals in each of the selected sections of the normalized frequency, the output of the first RAM 51 is connected with the first input of the third logical element And 46, the second input of which is connected to the output of the trigger 58, the second input of which is combined with the second input of the third RAM 53 and connected to the output of the second comparison circuit 55, the first input the third RAM 53 is the fourth input of block 25 - the input of the last values of the selected sections of the normalized frequency, the output of the third RAM 53 is connected to the first input of the second comparison circuit 55, the second input of which is combined with the first input of the first comparison circuit 54 and connected to the output of the second counter 57, the second the input of the second RAM 52 is the third input of block 25 - the input of the first values of the selected sections of the normalized frequency, the output of the second RAM 52 is connected to the second input of the first comparison circuit 54.

Works block the placement of the pilot signals 25 as follows. Modulated symbols coming from the first input of block 25 through the first logical element AND 44 and the first logical element OR 47 are sequentially written in a series-parallel register 60. In this case, either every N _f modulated data symbols (N _f is a given number), or through the adjusted number of modulated symbols position the pilot signal.

From the outputs of the serial-parallel register 60, the modulated symbols are simultaneously sent to the output of block 25.

In the serial-parallel register 60, the first and last Z digits are set to zero, and therefore, when parallel reading from the register 60, zero characters are read from them.

The pilot signals from the output of the first ROM 49 through the second input of the second logical element AND 45 and the second input of the first logical element OR 47 from the output of the first logical element OR 47 are fed to the input of the register 60. Moreover, the temporary position of the pilot signals (the moment the pilot reads the signals from the first ROM 49 ) is determined by the first counter 56, which generates a signal from its second output to the first input of the second logical element And 45 and the input of the first ROM 49. From the first output of the first counter 56, a signal is supplied to the second input of the first FRESH AND gate 44. At this time, the modulated symbols on the output of the first AND gate 44 is not received.

The value of the specified distance N _{f is} read from the output of the second ROM 50 and through the second input of the second logical element OR 48 is written through the first input of the first counter 56 to the counter 56. Clock pulses are received at the fourth input of the first counter 56 from the output of the GTI 59, which are formed by the GTI 59 the initial installation signal supplied to the input of the GTI 59 from the second input of block 25. The clock pulses and the initial installation signal are also supplied to the first input of the second counter 57.

The adjusted number of modulated symbols between the pilot signals at each of the selected sections, determined at the receiving station 2, is received from the fifth input of block 25 to the input of the first RAM 51 and is accordingly recorded in it. The first and last values of the selected sections of the normalized frequencies corresponding to these adjusted distances come respectively from the third and fourth inputs of block 25 to the second input of the second RAM 52 and the input of the third RAM 53 and are accordingly recorded in them.

The adjusted number of modulated symbols between the pilot signals at each of the selected sections of the normalized frequency determined at the receiving station 2, from the output of the first RAM 51 through the first input of the third logical element And 46 goes to the first input of the second logical element OR 48, and from its output to the first input of the first counter 56 and is recorded in it.

The allocated sections of the normalized frequency for the corresponding corrected distances between the pilot signals are determined by the first 54 and second 55 comparison schemes. At the second input of the first 54 comparison circuit and the first input of the second 55 comparison circuit are received respectively the outputs of the second 52 and third 53 RAM, respectively, the first and last values of the selected sections of the normalized frequencies. The first input of the first comparison circuit 54 and the second input of the second comparison circuit 55 receive output values from the second counter 57 that represent a sequence of normalized subcarrier frequencies. When the first values of the selected sections of the normalized frequency or the last values of the selected sections of the normalized frequency are equal to the values of the second counter 57, the outputs of the first 54 and second 55 comparison circuits receive signals, respectively, at the first and second inputs of the trigger 58. Thus, from the output of the first comparison circuit 54 to the first input of the trigger 58 receives a signal that sets the trigger 58 in a state in which the adjusted distance between the pilot signals received from the output of the first RAM 51 to the first input of the third Skog member 46 through the second input of the third AND gate 46 and a first input of the second OR gate 48 is recorded to its output via a first input to the first counter 56.

From the output of the second comparison circuit 55, a signal is received at the second input of the trigger 58, setting the trigger 58 to a state in which its output signal is supplied to the second input of the third logic element And 46. In this case, the adjusted distances between the pilot signals received from the output of the first RAM 51 are the first input of the third logical element AND 46, the output of this element is not received.

Block serial-parallel conversion and removal of the guard interval 21, for example, can be implemented according to the structural diagram, which is performed in figure 10.

Block serial-parallel conversion and removal of the guard interval 21 contains a register 61, a clock generator (GTI) 62, a logical element And 63, a counter 64 and a trigger 65, while the input of the clock generator 62, the first inputs of the counter 64 and trigger 65 are combined, forming the second input of block 21, which receives the initial setup signal from the second input of block 21, the output of the clock generator 62 is connected to the second input of the counter 64 and the first input of the logical element And 63, the second input of which is connected to the output of Igger 65, the second and third inputs of which are connected respectively to the first and second outputs of the counter 64, the output of the logic element And 63 is connected to the second input of the register 61, the first input of which receives a signal from the first input of the block 21, the outputs of the register 61 are the outputs of the block in series parallel conversion and removal of the guard interval 21.

Works block serial-parallel conversion and removal of the guard interval 21 as follows. The samples of the orthogonal frequency multiplexed symbols are sequentially fed to the first input of the serial-parallel conversion block and the removal of the guard interval 21. Each of these symbols contains G + N samples. From the first input of block 21, the samples of the orthogonal frequency multiplexed symbols are received at the first input of the serial-parallel register 61 and sequentially written to it. Of the 61 G + N samples received at the first input of the register of one frequency multiplexed symbol, only N samples are recorded in the register 61 itself. The guard interval samples are not recorded in register 61. From the outputs of the register 61 N samples in parallel arrive at the outputs of block 21.

The counter 64 on the signal of the initial installation, which is supplied to its first input from the first input of block 21, and the signal, which is fed to its second input from the output of the GTI 62, determines the duration of the received symbol and the duration of the guard interval. The logical element And 63, the trigger 65 and the counter 64 of the clock pulses of the GTI 62, arriving at their inputs, form the clock pulses for the register 61, arriving at its second input.

The unit for calculating the magnitude of the changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized frequency 26 can be performed according to the structural diagram shown in Fig.11.

The unit for calculating the magnitude of changes in the values of the normalized modules and phases of the pilot signals and determining the allocated sections of the normalized frequency 26 (Fig. 11) contains the first 66, second 67 and third 68 registers, random access memory (RAM) 69, counter 70, clock generator (GTI) ) 71, the node of calculation of the module 72, the first 73 and second 74 nodes of subtraction, the first 75 and second 76 nodes of division, the first 77 and second 78 nodes of comparison with the threshold, the first 79, second 80, third 81 and fourth 82 logical elements AND (LE I), the first 83 and second 84 nodes calculation average about the values, the first 85 and second 86 rounding nodes, the first 87 and second 88 decoders, the first 89 and second 90 read-only memory (ROM), the phase calculation unit 91 and the comparison unit 92, while the inputs of the first register 66 are inputs of the block 26 - inputs of values of the fast Fourier transform of modulated symbols, the output of the first register 66 is connected to the first input of RAM 69, the second input of which is combined with the first inputs of the second 80 and fourth 82 logic elements And and connected to the output of the counter 70, the first input of which is combined with the input GTI 71, forming the second input of block 26, which is the input of the initial setting signal, the second input of the counter is connected to the output of the GTI 71, the output of RAM 69 is connected to the inputs of the calculation unit of module 72 and the calculation unit of phase 91, the output of the calculation unit of module 72 is connected to the input of the second register 67, the first and second outputs of which are connected respectively to the first and second inputs of the first subtraction node 73, the output of which is connected to the input of the first division node 75, the output of which is connected to the input of the first comparison node with a threshold 77 and the first input of the first about the logical element And 79, the second input of which is combined with the second input of the second logical element And 80 and connected to the output of the first comparison node with a threshold 77, the output of the first logical element And 79 is connected to the input of the first node calculating the average value 83, the output of which is connected to the input the first rounding node 85, the output of which is connected to the input of the first decoder 87, the output of which is connected to the input of the first ROM 89, the output of which is connected to the first input of the comparison unit 92, the output of the second logical element And 80 is not the first output of block 26, which receives the first values of the selected sections of the normalized frequency, the output of the fourth logical element And 82 is the second output of the block 26, which receives the last values of the selected sections of the normalized frequency, the output of the phase calculation unit 91 is connected to the input of the third register 68, the first and the second outputs of which are connected respectively to the first and second inputs of the second subtraction unit 74, the output of which is connected to the input of the second division unit 76, the output of which is connected to the input of the second node and comparisons with a threshold 78 and the first input of the third AND gate 81, the first and second outputs of the second comparison node with a threshold 78 are connected respectively to the second input of the fourth gate And 82 and the second input of the third gate And 81, the output of the third gate And 81 is connected with the input of the second node for calculating the average value 84, the output of which is connected to the input of the second rounding node 86, the output of which is connected to the input of the second decoder 88, the output of which is connected to the input of the second ROM 90, the output of which the second is connected to the second input of the comparison node 92, the output of which is the third output of the block 26, which receives the corrected number of modulated symbols between the pilot signals in each selected section of the normalized frequency.

The unit 26 (Fig. 11) operates as follows.

The FFT values (modulated symbols) received at the inputs of the first register 66 are written to it in parallel, and then sequentially read from it into RAM 69.

From RAM 69, the FFT values are sequentially read to the computing unit of module 72 and the computing unit of phase 91.

In the computing node of module 72, pilot signals are extracted and their modules are calculated.

The node calculation module 72 can be performed in the form of a register and counter, forming a signal, gating the pilot signals, as well as circuit calculation module.

From the output of the node calculation module 72, the sequence of modules of the pilot signals is fed to the input of the second register 67, which is a serial-parallel register. From the first and last bits of the register (the beginning and the end of the window), the pilot signal modules arrive respectively from the first and second outputs to the first and second inputs of the first subtraction unit 73. From the output of the first subtraction unit 73, the difference of the pilot signal modules is fed to the input of the first division unit 75.

Further, in the first division node 75, the calculated difference of the pilot signal modules is divided by the difference of the normalized frequencies corresponding to the beginning and end of the window. Thus, the changes in the normalized modules of the pilot signals are calculated.

The calculated changes in the normalized modules of the pilot signals from the output of the first division unit 75 are fed to the input of the first comparison node with a threshold of 77 and the second input of the first logical element And 79.

In the first comparison node with threshold 77, the calculated changes in the normalized pilot signal modules are compared with a predetermined threshold value. Changes to the normalized pilot signal modules that exceed a predetermined value, through the first logic element And 79, are input to the first node for calculating the average value 83, in which the average value of the changes to the normalized pilot signal modules is calculated.

If the average value is a fractional number, then it is rounded to an integer in the first rounding node 85.

The average value of the changes in the normalized modules of the pilot signals from the output of the first rounding node 85 is fed to the input of the first decoder 87, which converts the average value to the address of the first ROM 89, which goes to the input of the first ROM 89, at this address the corrected number of modulated symbols is written to this ROM 89 (tabular method for calculating the adjusted number of modulated symbols). Thus, the output of the first ROM 89 at the first input of the comparison unit 92 receives the corrected number of modulated signals between the pilot signals.

In the phase 91 calculation node, pilot signals are extracted and their phases are calculated.

The node calculation phase 91 can be performed in the form of a register and counter, forming a signal, strobe the pilot signals, and phase calculation circuit. The phase can be calculated using the tabular method.

From the output of the phase calculation unit 91, the phase sequence of the pilot signals is input to a third register 68, which is a serial-parallel register. From the first and last bits of the third register 68 (the beginning and the end of the window) of the phase from the first and second outputs, the pilot signals are received respectively at the first and second inputs of the second subtraction unit 74.

From the output of the second subtraction unit 74, the calculated phase difference of the pilot signals is input to the second division unit 76, in which the calculated phase difference of the pilot signals is divided by the difference of the normalized frequencies corresponding to the beginning and end of the window. In this way, the phase changes of the pilot signals are calculated.

The calculated changes in the phase of the pilot signals received from the output of the second division node 76 to the input of the second comparison node with a threshold of 78 and the first input of the third logical element And 81 are compared with a predetermined threshold value in the second comparison node with a threshold of 78. Changes in the phases of the pilot signals that exceed the specified the threshold value, through the second input of the third logical element And 81 from its output go to the input of the second node calculating the average value 84, in which the average value of these changes in the phase of the pilot signals is calculated.

If the average value is a fractional number, then it is rounded to an integer in the second rounding node 86.

The average values of the phase changes of the pilot signals are fed to the input of the second decoder 86, which converts the average value to the address of the second ROM 90, which is fed to this ROM 90, which records the corrected number of modulated symbols between the pilot signals. Thus, the output of the second ROM 90 at the second input of the comparison unit 92 receives the corrected number of modulated symbols between the pilot signals.

In the comparison node 92, two corrected numbers of modulated symbols are compared between the pilot signals arriving at its first and second inputs, and the larger one is fed to its output and then to the third output of block 26.

The initial installation signal from the second input of block 26 is supplied to the first input of the counter 70 and the input of the clock pulse generator 71 (GTI), which are set to the initial state by this signal.

Clock pulses from the output of the GTI 71 are fed to the second input of the counter 70. The output of the counter 70 is fed to the second input of the RAM 69 and the first inputs of the second and fourth logical elements And 80 and 82.

The counter signal 70 provides the recording of modulated symbols (output FFT values) in RAM 69 and reading them from RAM 69.

Each modulated symbol corresponds to a subcarrier with a normalized frequency equal to its serial number from 1 to N, and the addresses of the modulated symbols recorded in RAM 69 also vary from 1 to N. Thus, the counter 70 generates the normalized frequencies of the modulated symbol subcarriers.

When the second logic element AND 80 receives a signal from the output of the first comparison node with a threshold 77, the output signal of the counter 70, as the first values of the allocated sections of the normalized frequency, goes to the first input of the second logical element And 80 and then from its output to the first output of block 26.

When the second input of the fourth logical element And 82 receives a signal from the output of the second comparison node with a threshold 78, the output signal of the counter 70, as the last values of the allocated sections of the normalized frequency, goes to the first input of the fourth logical element And 82 and then to the second output of block 26.

Thus, the output of block 26 receives the first and last values of the selected sections of the normalized frequency, where there was an excess of phase changes or normalized modules of the pilot signals of given values.

The signal conditioning unit of the return channel 27 can be implemented in various ways. For example, in the form of a series-connected node of parallel-serial conversion and the transmitting part of the prototype (from modulator 4 to transmitter 10). The parallel-serial conversion node can be performed on the basis of parallel-serial registers. In this case, the input parallel characters are converted into serial form and then fed to the input of the modulator.

Thus, the implementation of all of the above features of the claimed invention improves the noise immunity in communication systems with orthogonal frequency multiplexing.

Claims (2)

1. The method of transmitting and receiving data in a radio communication system, namely, that a sequence of binary characters is received at the transmitting station, the sequence is divided into words consisting of d characters, where d is a given number, each word is assigned a modulated data symbol in the form of a complex number, transform the sequence of modulated data symbols into parallel groups of modulated symbols, complement the groups of modulated data symbols with sequences consisting of Z zero characters, position Single them at the beginning and end of the group, and every N _f modulated data symbols a pilot signal, where N _f = Q / K, and Q is a multiple of K and N = Q + 2Z + K, and K is the number of pilot signals in the group, with OBPFs are performed by each group of the generated sequence, forming parallel output groups of OBPF values, and the parallel output blocks of OBPF values are converted into a serial form, thus forming a sequence of transmitted characters, each of which contains N received consecutive OBPF values, complement each transmitted th symbol guard interval, thereby forming a sequence orthogonal frequency multiplexed symbol sequence transmitted orthogonal frequency multiplexed symbols to the receiving station; they are received at the receiving station and the guard interval is removed, thus forming a sequence of received symbols, the received symbols are converted into parallel groups of input values, FFT is performed with each group of input values, thus forming parallel groups of modulated symbols consisting of N modulated each symbol, associate with each modulated symbol the frequency of the subcarrier normalized to the frequency shift between the subcarriers, and the frequency of the subcarrier is equal to its ordinal the number in the group, taking a value from 1 to N, the modulated data symbols and the pilot signals, as well as the corresponding normalized frequencies are allocated and stored in the groups, the modules and phases of the pilot signals are calculated in each group, the maximum value of the pilot signal module in each group is determined and the calculated pilot signal modules are normalized to the maximum value of the pilot signal module of this group, in each group for all subcarriers with pilot signals, the pilot signal phase changes are calculated in a sliding window of a given size, as the ratio of the phase difference of the pilot signals at the beginning and at the end of the window to the difference of the normalized frequencies corresponding to them, and the subcarrier for which the phase changes of the pilot signals are calculated is the center of the window, in each group for all subcarriers with the pilot signals are calculated in the sliding window of the specified the size of the change of normalized pilot signal modules, as the ratio of the difference of the pilot signal modules corresponding to the beginning and end of the window to the difference of the normalized frequencies corresponding to them, the subcarrier corresponding to the calculated change in the normalized modules of the pilot signals is the center of the window, the calculated changes in the phases and the normalized modules of the pilot signals are compared with the specified values of the changes in the phase and the module and the first and last values of the selected sections of the normalized frequency, where the specified values are exceeded, and changes in the normalized modules and phases of the pilot signals in this section, calculate the average values of the phases and normalized modules of the pilot signals in the selected sections of the normalized hour where the change in phases or normalized modules of the pilot signals of predetermined values has occurred, if the average value is a fractional number, then it is rounded to an integer, the calculated number of phases and modules of the pilot signals calculated for the corresponding selected sections of the normalized frequency determines the corrected number of modulated symbols between the pilot signals so that the number of modulated symbols between the pilot signals is proportional to the magnitude of the phase changes or normalized x pilot signal modules, if at some intervals the allocated sections of the normalized frequency, on which the adjusted number of modulated symbols between the pilot signals are determined, overlap, then at these intervals, the maximum is selected from the two adjusted numbers of modulated symbols between the pilot signals, transmitted from the receiving station to the transmitting station the first and last values of the selected sections of the normalized frequency, as well as the adjusted number of modulated symbols between the pilot signals at k each of these sites; at the receiving station, on the pilot signals, the communication channel is estimated using the obtained communication channel estimation results, Q modulated data symbol estimates are performed, the modulated data symbol rating groups are converted into a serial form, thereby forming a sequence of modulated data symbol estimates, demodulated received estimates modulated data symbols, thereby forming a sequence of binary data; the transmitting station receives the first and last values of the allocated sections of the normalized frequency, where there has been an excess of phase changes or normalized modules of the pilot signals of specified values, as well as the adjusted number of modulated symbols between the pilot signals in each of these sections, and the number of modulated symbols is adjusted in accordance with them between pilot signals. 2. A device for transmitting / receiving data in a radio communication system containing a transmitting and receiving station, wherein the transmitting station comprises a modulator, an inverse fast Fourier transform unit, a parallel-serial conversion unit, a guard interval attachment unit, a transmitter, a receiver, a splitter and an antenna, this modulator input is the first input of the transmitting station, the input of a sequence of binary characters, the output of the transmitter is connected to the first input of the splitter, the first output of which is connected to the first input of the antenna, the first output of which is the first output of the transmitting station transmitting frequency-multiplexed symbols from the first output on the radio frequency, the second input of the antenna is the second input of the transmitting station - the input of frequency-multiplexed symbols transmitted on the radio frequency from the transmitting station, the second output of the antenna is connected with the second input of the splitter, the second output of which is connected to the input of the receiver; the receiving station contains an antenna, a splitter, a receiver, a transmitter, a block-parallel-parallel conversion and removal of the guard interval, a fast Fourier transform block, a channel estimation block, a parallel-serial conversion block and a demodulator, the first input of the antenna being the first input of the receiving station-input frequency-multiplexed symbols, the first output of the antenna is connected to the first input of the splitter, the first output of which is connected to the input of the receiver, the output of which is connected to the first input of the serial-parallel conversion unit and removing the guard interval, the outputs of which are connected respectively to the inputs of the fast Fourier transform unit, the outputs of which are connected to the inputs of the channel estimator, the outputs of which are connected to the inputs of the parallel-serial conversion unit, the output of which is connected to the input of the demodulator, the output of which is the first output of the receiving station, forming a sequence of binary data at this output, the output of the transmitter is connected to the second input of the splitter, the second output of which is connected to the second input of the antenna, the second output of which is the second output of the receiving station, characterized in that a pilot signal placement unit is introduced at the transmitting station, the first input of which is connected to the modulator output, the second input of the pilot signal placement unit is combined with the first input of the guard interval attachment unit, forming the third input of the transmitting station, which is the input of the initial setup signal, the third, fourth and fifth inputs of the arrangement unit the pilot signals are connected respectively to the first, second and third outputs of the receiver, which forms the first values of the selected sections of the normalized frequency at the first output, the last values of the selected sections of the normalized frequency at the second output, and the adjusted number of modulated symbols between the pilot signals at each of the selected signals at the third output sections, while the pilot signal alignment unit corrects the number of modulated symbols between the pilot signals based on the signals received from the first, second and the third outputs of the receiver, the outputs of the pilot signal alignment unit are connected to the inputs of the inverse Fourier transform unit, the outputs of which are connected to the inputs of the parallel-serial conversion unit, the output of which is connected to the second input of the guard interval connection unit, the output of which is connected to the transmitter input; at the receiving station, a unit for calculating the values of changes in the values of the normalized modules and phases of the pilot signals and determining the allocated sections of the normalized frequency and a block for generating a signal of the return channel are introduced, while the outputs of the fast Fourier transform unit are connected to the first inputs of the unit for calculating the values of the values of the normalized modules and phases of the pilot signals and determining the selected sections of the normalized frequency, forming on the first output the first values of the selected sections of the normalized frequency, on the second output - the last values of the selected sections of the normalized frequency, the third output - the adjusted number of modulated symbols between the pilot signals in each selected section of the normalized frequency, the first, second and third outputs of the unit for calculating the changes in the values of the normalized modules and phases of the pilot signals and determine the selected sections of the normalized the frequencies are connected respectively to the first, second and third inputs of the reverse channel signal generating unit, the output of which is connected to the input sensor, the second inputs of the unit for calculating the changes in the values of the normalized modules and phases of the pilot signals and determine the allocated sections of the normalized frequency and the block of serial-parallel conversion and removal of the guard interval are combined to form the second input of the receiving station, which is the input of the initial setup signal.

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