KR100612647B1 - System and method for estimating channel using orthogonal sequency - Google Patents

Abstract

The present invention relates to a channel estimation system and method using orthogonal sequences.

A channel estimation system and method using an orthogonal sequence include a characteristic of an orthogonal frequency division multiplex (OFDM), a unique spreading code and an orthogonal code used in a code division multiple access (CDMA) system, and a channel estimation state. In the applied system, a pilot channel using a pseudo noise sequence of a unique spreading code used to increase channel capacity is inserted into grouped data channels to obtain characteristics required for channel estimation for each subchannel group, and each orthogonal frequency division multiplexing is performed. The performance of the system can be improved by estimating the channel related to delay characteristics, frequency offset, phase rotation, etc. using the interpolation and extrapolation of the characteristics of the subchannels.

Orthogonal frequency division multiple, code division multiple access, unique spreading code, orthogonal code, channel estimation

Description

Channel Estimation System Using Orthogonal Sequence and Its Method {SYSTEM AND METHOD FOR ESTIMATING CHANNEL USING ORTHOGONAL SEQUENCY}

1 illustrates a configuration of a channel estimation system using an orthogonal sequence according to a first embodiment of the present invention.

FIG. 2 illustrates a configuration of an orthogonal coder which is a part of FIG. 1.

3 illustrates a configuration of a receiver of a channel estimation system using an orthogonal sequence according to an embodiment of the present invention.

4 illustrates a configuration of a channel estimation / phase delay compensator, which is a part of FIG. 3.

FIG. 5 illustrates a configuration of an inverse orthogonal code part which is a part of FIG. 3.

The present invention relates to a channel estimation system and method using an orthogonal sequence, and more particularly, to a channel estimation system using an orthogonal sequence for estimating a channel related to a delay characteristic and a frequency offset in increasing channel capacity using an orthogonal code and a non-binary signal value. It is about.

In the modulation and demodulation method, a data rate is increased by using a QAM modulation method to support an increasing data rate in a limited frequency band. However, in the modulation scheme of 16-QAM or higher, there is a problem in terms of performance in terms of mobility and a certain separation distance.

After the recent announcement that the channel capacity is proportional to the number of transmit / receive antennas in the same bandwidth by using multiple input / receive antennas (MIMO) in a channel having rich scattering characteristics, the MIMO technique receives multiple receptions. The application method using the signal detection method is researched.

The received signal detection method using the MIMO procedure is difficult to implement because it must have a plurality of antennas in the mobile terminal and rich scattering of the channel must be maintained.

In the received signal detection method using MIMO procedure, since the state of the channel is changed, the performance is improved by using a transmission rate suitable for the channel state, and the user uses a unique spreading code and an orthogonal code. The data rate is increased without increasing the overall bandwidth, and OFDM is used to solve problems such as signal interference.

Orthogonal Frequency Division Multiplexing (OFDM) is sensitive to phase delay and frequency offset, and thus orthogonality must be maintained between subchannels, so channel estimation of subchannels is required.

The subchannel frequency, which is the transmission frequency in OFDM, is sensitive to the offset of the frequency. As a result, the orthogonality of OFDM is destroyed, so that there is a problem of estimating characteristics of the transmission channel such as delay and frequency offset.

The technical problem to be achieved by the present invention is to interpolate and extrapolate the characteristics of each OFDM subchannel by inserting a pilot channel using a unique spread code pseudo-random noise sequence into grouped data channels to increase channel capacity. Provided are a channel estimation system and method using an orthogonal sequence for estimating a channel using a method to improve performance.

In order to solve this problem, the present invention inserts a pilot channel using a pseudo noise sequence of a unique spreading code into grouped data channels, and delays characteristics of each orthogonal frequency division multiple subchannel using interpolation and extrapolation. To estimate the frequency, frequency offset, phase rotation, etc.

A channel estimation system using an orthogonal sequence according to the first aspect of the present invention, the channel estimation system using an orthogonal sequence for transmitting input data, comprising: a mapper for generating and outputting the input data as a non-binary signal; A serial / parallel converter for serially / parallel converting the non-binary signal transmitted from the mapper, an orthogonal code converter for outputting the serialized / parallel converted signal with each orthogonal code, and an adder for adding each orthogonal code; An orthogonal code unit for increasing channel capacity; A unique spreading code synthesizer for synthesizing a signal output from the orthogonal coder using a unique spreading code; A serial / parallel converter for serially / parallel converting the signals output from the eigenspread code synthesizer, and grouping the serial / parallel signals into sub-channel groups, and inserting a pilot signal for inserting a unique spread code of each group as a pilot signal An orthogonal frequency division multiplexer for outputting a pilot signal on which the guard interval processing is performed, including a guard interval inserter for guard period processing of the signal output from the pilot signal inserter; And a modulation controller for performing complex inverse Fourier transform on the signal output from the orthogonal frequency division multiplexer and performing parallel / serial conversion to output the signal.

A channel estimating system using an orthogonal sequence includes first and second multipliers for receiving data output from the modulation controller one by one and multiplying and modulating the high frequency signal input from the outside; And a synthesizer configured to receive modulated data from the first and second multipliers and synthesize the synthesized data to propagate the airwaves.

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A channel estimating system using an orthogonal sequence according to a second aspect of the present invention includes a channel estimating system using an orthogonal sequence for recovering received data into an original signal, comprising: a low pass filter for removing high frequency components from the received data; A signal processor for performing analog / digital conversion, frame / fourier conversion start point estimation, and guard interval elimination for the data output from the low pass filter; A fast Fourier transform unit for performing fast Fourier transform by inputting a Fourier transform start point estimation signal from the signal processor; A channel including a correlator for obtaining a correlation value of some sub-channels by inputting a frame start point estimation signal and a signal output from the fast Fourier transform unit in the signal processor, and an estimation processor for performing phase compensation and channel state estimation based on the correlation values Estimation / phase delay compensator; A plurality of equalization demodulators for equalizing and demodulating subchannel data grouped with the estimated values output from the channel estimation / phase delay compensator, respectively; A multiplier for multiplying the signals equalized and demodulated by the equalization demodulator using a unique spreading code; An inverse orthogonal code unit for integrating and outputting values output from the multiplier using respective orthogonal codes (DE-ORTHOGONAL CODE); And an inverse mapper (DE0MAPPER) for dividing the values integrated in the inverse orthogonal coder by using a non-binary signal to recover the original signal.

A channel estimating system using an orthogonal sequence includes: first and second multipliers for multiplying the received data and outputting the low-pass filter, and a parallel / serial conversion unit for performing parallel / serial conversion of the equalized demodulated signal from the equalization demodulator, The apparatus may further include a serial / parallel converter configured to transmit output data obtained by serially / parallel converting signals output from the inverse mapper.

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The inverse orthogonal code unit may include: an orthogonal code converter that multiplies the synthesized signal output from the eigenspread code synthesizer with each orthogonal code; An integrator for integrating each orthogonal code output from the orthogonal code conversion unit by a predetermined period based on one period of the intrinsic spreading code; And a parallel / serial conversion unit for outputting the parallel / serial conversion of the values integrated in the integrator.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

First, a channel estimation system using an orthogonal sequence according to a first embodiment of the present invention will be described in detail with reference to FIG. 1.

1 illustrates a configuration of a channel estimation system using an orthogonal sequence according to a first embodiment of the present invention.

As shown in FIG. 1, in a channel estimation system using an orthogonal sequence according to a first embodiment of the present invention, a transmitter includes a mapper 120, an orthogonal coder 130, an orthogonal frequency division multiplexer 150, and modulation control. The unit 160 is included.

When the input data is input through the first serial / parallel converter 110, the mapper 120 generates and outputs the input data as a non-binary signal value.

The orthogonal coder 130 receives the non-binary signal value from the mapper 120 to increase the channel capacity using the orthogonal code, and the value output from the orthogonal coder 130 is a unique spread code synthesizer 140 and the second. Output is via serial / parallel converter 151.

The orthogonal frequency division multiplexer 150 includes a second serial / parallel converter 151, a pilot signal inserter 152, and a guard interval inserter 153.

The orthogonal frequency division multiplexer 150 groups the parallel-parallel signals output from the second serial / parallel converter 151 into n1 subchannel groups, and inherent of W1 in each group in the pilot signal inserter 152. After the spread code is inserted into the pilot sequence, a signal which has undergone the guard interval processing of the pilot signal insertion unit 153 is output.

The modulation controller 160 inputs a signal output from the orthogonal frequency division multiplexer 150 into an imaginary input and a real input of a complex inverse Fourier transform (IFFT) input, and then performs parallel / serial conversion to a multiplier 170. Output

The multiplier 170 receives data one by one from the modulation controller 160 and multiplies the radio frequency (RF) input from the outside to output the modulated data to the synthesizer 180.

The synthesizer 180 receives two modulated data from the two multipliers 170, synthesizes the modulated data, and propagates it over the airwaves.

The operation of the channel estimation system using the orthogonal sequence according to the first embodiment of the present invention configured as described above will be described using a non-binary signal value 16-QAM.

Input data is input to the mapper 120 via the first serial / parallel converter 110, and the mapper 120 outputs a gray coded non-binary signal.

In this case, the non-binary signals output from the two mappers 120 are referred to as d (1) = (d, -d, 3d, d), d (2) = (-3d, 3d, d, -d), where d means the minimum distance of the 16-QAM constellation.

FIG. 2 illustrates a configuration of an orthogonal code unit, which is a component of FIG. 1, and as shown in FIG. 2, the orthogonal code unit 130 converts a non-binary signal output from the mapper 120 into a serial / parallel converter 131. ) And serialized / parallel conversion, and the converted signals are input from the orthogonal code conversion unit 132 and each orthogonal code Sub-w (1), Sub-w (2), Sub-w (3), and Sub- Output to w (4). Then, the adder 133 outputs the sum of the orthogonal codes to the unique spread code synthesizer 140.

Respective orthogonal codes, inherent spread codes, and non-binary signal data are represented by 0 as ?? and 1 by +, respectively, as shown below.

<Orthogonal code>

Sub-w (1) = (1 1 1 1)-> (+ + + +)

Sub-w (2) = (1 0 1 0)-> (+-+-)

Sub-w (3) = (1 1 0 0)-> (+ +--)

Sub-w (4) = (1 0 0 1)-> (+--+)

<Unique diffusion code>

W1 = (0 1 0 1 0 1 0 1)-> (-+-+-+-+)

<Gray-coded non-binary signal>

d (1) = (d, -d, 3d, d),

d (2) = (-3d, 3d, d, -d)

In the gray coded non-binary signal above, d is regarded as a constant and is multiplied after elimination, d (1) = (+1 -1 +3 +1), d (2) = (-3 +3 +1- 1) becomes.

At this time, the orthogonal codes Sub-w (1), Sub-w (2), Sub-w (3), and Sub-w (4) of the first mapper among the two mappers 120 receive the non-binary signal d (1). (A1), the orthogonal codes Sub-w (1), Sub-w (2), Sub-w (3), and Sub-w (4) of the second mapper multiply the non-binary signal d (2) (A2). ).

Then, the result of multiplying each orthogonal code and a non-binary signal is as follows.

A1: A2:

C (1) = (+1 + 1 + 1 +1) C (1) = (-3 -3 -3 -3)

C (2) = (-1 +1 -1 +1) C (2) = (+3 -3 +3 -3)

C (3) = (+3 +3 -3 -3) C (3) = (+1 +1 -1 -1)

C (4) = (+1 -1 -1 +1) C (4) = (-1 +1 +1 -1)

The result of multiplying the orthogonal codes and the non-binary signal (A1, A2) is summed again, and the result (ㅠ 1, B2) is as follows.

B1: (+4 +4 -4 0), B2 :( 0 -4 0 -8)

The sum of the above values (B1, B2) is multiplied by W1, respectively, to have the following result values (D1, D2).

D1: (-4 +4 -4 +4 +4 -4 0 0) D2 :( 00 +4 -4 00 +8 -8)

The above D1 and D2 values are output values through the input data through the mapper 120, the orthogonal code unit 130, and the unique spread code synthesizer 140.

In the orthogonal frequency division multiplexing unit 150, signals paralleled through the second serial / parallel unit 151 are grouped into n1 subchannel groups, and a unique spreading code of W1 is inserted into each group in a pilot sequence. It is input to the modulation controller 160 through the guard interval processing.

The imaginary input and the real input of the complex IFFT input from the modulation controller 160 and performing the parallel / serial conversion are output to the two multipliers 170 one by one, and the multiplier 170 receives the respective data from the outside. Modulated data is output by multiplying by high frequency (RF).

The synthesizer 180 synthesizes two modulated data input from the two multipliers 170 to propagate in the airwaves.

Hereinafter, a channel estimation system using an orthogonal sequence according to an embodiment of the present invention will be described.

3 is a block diagram of a receiver of a channel estimating system using an orthogonal sequence according to an embodiment of the present invention, and FIG. 4 is a block diagram of a channel estimation / phase delay compensator, which is a part of FIG. 5 illustrates a configuration of an inverse orthogonal code part which is a part of FIG. 3.

In the second embodiment of the present invention, since the inverse process of the first embodiment is performed to find the original signal, a description of the elements for performing the inverse process of some components of the first embodiment is omitted.

As shown in FIG. 3, a receiver of a channel estimation system using an orthogonal sequence according to a second embodiment of the present invention finds an original signal by demodulating and inversely mapping a signal transmitted from a transmitter.

That is, the data S (t) received at the receiver is output to the low pass filter 220 through the two multipliers 210, and the two low pass filters remove the high frequency components from the received data to signal Output to the processor 230.

The signal processor 230 performs functions such as analog / digital conversion, guard interval elimination, and Fourier transform (FFT) / frame start point estimation. The analog signal is converted into a digital signal from a signal output from the low pass filter (LPF) 220. After conversion to the protection section is removed and output to the fast Fourier transform unit 240.

The frame / FFT starting point estimation signal is input to the complex FFT and the channel estimation / phase delay compensator 150, respectively.

The FFT starting point estimation signal is input to the fast Fourier transformer 240, and the frame starting point estimation signal is input to the correlator 251 of the channel estimation / phase delay compensator 250.

The channel estimation / phase delay compensator 250 includes a correlator 251 and an estimation processor 252, as shown in FIG. 4, each of which is a pilot of the unique spreading code sequence W1 of the subchannel group. Correlating with the channel signal input, the estimation processor 252 estimates the phase compensation, the channel characteristics, etc. based on the output values correlated by the correlator 251.

In this case, the estimated value of each pilot subchannel estimates each grouped data subchannel and phase delay using interpolation and extrapolation.

That is, the correlator 251 is periodically received in the frame start point estimation signal in accordance with the FFT / frame start point to measure the reception channel state, and receives the received signal of each grouping pilot subchannel in the unique spreading code sequence W1 of each group. To the pilot channel signal.

Then, the correlator 251 obtains correlation values of some subchannels among the subchannels using the signals, and the estimation processor 252 performs phase compensation and channel state estimation.

The estimated output value is input to the equalization demodulator 260 of n1 groups that equalizes and demodulates the grouped subchannel data to equalize and demodulate the input data of the subdata channel, and then the parallel / serial converter 270. Will be printed).

The data output from the parallel / serial converter 270 is output to each unique spreading code multiplier 280, and the value output from the unique spreading code multiplier 280 is output to the inverse orthogonal coding unit 290. Then, the inverse orthogonal code unit 290 is composed of an orthogonal code converter 291, an integrator 292, and a parallel / serial converter 293, so that the data input from the multiplier 280 is respectively sub-w (1). After multiplying to (4) as follows, the output is output to the inverse mapper 300.

(1) (+4 +4 +4 +4 -4 -4 0 0) (00 -4 -4 00 -8 -8)

(2) (+4 +4 -4 -4 -4 -4 0 0) (00 +4 +4 00 +8 +8)

(3) (+4 +4 +4 +4 +4 +4 0 0) (00 -4 -4 00 +8 +8)

(4) (+4 +4 -4 -4 +4 +4 0 0) (00 +4 + -4 00 -8 -8)

In this case, the inverse orthogonal code unit 290 sums each value for one period and multiplies the value divided by the value for one period by d (minimum distance of the 16-QAM signal point), respectively, (d, -d, 3d , d), (-3d, 3d, d, -d). Here, one period of W1 is integrated by 1/8 period sections, respectively, so as to be the total integration section.

An embodiment of the present invention is applied to the characteristics of orthogonal frequency division multiplexing (OFDM), unique spreading codes and orthogonal codes used in a code division multiple access (CDMA) system, and a channel estimation state. In order to obtain characteristics required for channel estimation for each channel, a pilot channel may be configured using a unique spreading code, and a channel related to delay characteristics and frequency offset may be estimated.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto, and various other changes and modifications are possible.

As described above, in the channel estimation system and method using the orthogonal sequence according to the present invention, in order to obtain characteristics required for channel estimation for each subchannel group, a pilot channel using a unique spreading code in a unique spreading code and an orthogonal code is used to delay and By estimating a channel related to the frequency offset, etc., the system performance can be improved.

Claims (12)

In the channel estimation system using an orthogonal sequence for transmitting input data, A mapper generating and outputting the input data as a non-binary signal; A serial / parallel converter for serially / parallel converting the non-binary signal transmitted from the mapper, an orthogonal code converter for outputting the serialized / parallel converted signal with each orthogonal code, and an adder for adding each orthogonal code; An orthogonal code unit for increasing channel capacity; A unique spreading code synthesizer for synthesizing a signal output from the orthogonal coder using a unique spreading code; A serial / parallel converter for serially / parallel converting the signals output from the eigenspread code synthesizer, and grouping the serial / parallel signals into sub-channel groups, and inserting a pilot signal for inserting a unique spread code of each group as a pilot signal An orthogonal frequency division multiplexer for outputting a pilot signal on which the guard interval processing is performed, including a guard interval inserter for guard period processing of the signal output from the pilot signal inserter; And A modulation controller for performing complex inverse Fourier transform on the signal output from the quadrature frequency division multiplexer and then performing parallel / serial conversion Channel estimation system using an orthogonal sequence comprising a. The method of claim 1, First and second multipliers configured to receive data output from the modulation controller one by one and multiply and modulate the high frequency signal input from the outside; And A synthesizer that receives modulated data from the first and second multipliers and synthesizes the synthesized data to propagate the airwaves. Channel estimation system using an orthogonal sequence further comprising. The method of claim 1, The non-binary signal output from the mapper is represented by d (n) = (d, -d, nd, d), and d is a channel estimation system using an orthogonal sequence means a minimum distance of the signal point. delete delete The method of claim 1, The modulation control unit, And an orthogonal sequence for inputting signals output from the orthogonal frequency division multiplexing unit using imaginary input and real input, respectively, and performing parallel inverse Fourier transformation to output parallel and serial transformations. In the channel estimation system using an orthogonal sequence for recovering the received data to the original signal, A low pass filter for removing high frequency components from the received data; A signal processor for performing analog / digital conversion, frame / fourier conversion start point estimation, and guard interval elimination for the data output from the low pass filter; A fast Fourier transform unit for performing fast Fourier transform by inputting a Fourier transform start point estimation signal from the signal processor; A channel including a correlator for obtaining a correlation value of some sub-channels by inputting a frame start point estimation signal and a signal output from the fast Fourier transform unit in the signal processor, and an estimation processor for performing phase compensation and channel state estimation based on the correlation values Estimation / phase delay compensator; A plurality of equalization demodulators for equalizing and demodulating subchannel data grouped with the estimated values output from the channel estimation / phase delay compensator, respectively; A multiplier for multiplying the signals equalized and demodulated by the equalization demodulator using a unique spreading code; An inverse orthogonal code unit for integrating and outputting values output from the multiplier using respective orthogonal codes (DE-ORTHOGONAL CODE); And An inverse mapper (DE0MAPPER) for dividing the values integrated in the inverse orthogonal coder by using a non-binary signal to recover the original signal Channel estimation system using an orthogonal sequence comprising a. The method of claim 7, wherein And a first and second multipliers for multiplying the received data and outputting the multiplied output signals to the low pass filter. The method of claim 7, wherein And a parallel / serial conversion unit configured to perform parallel / serial conversion of the equalized demodulated signal by the equalization demodulator and output the parallel / serial conversion unit. The method of claim 1, And a serial / parallel converter configured to transmit output data obtained by serially / parallel converting signals output from the inverse mapper. delete The method of claim 7, wherein The reverse orthogonal code portion, An orthogonal code converter for multiplying the synthesized signal output from the eigenspread code synthesizer with each orthogonal code; An integrator for integrating each orthogonal code output from the orthogonal code conversion unit by a predetermined period based on one period of the intrinsic spreading code; And A parallel / serial conversion unit for outputting the parallel / serial conversion of the values integrated in the integrator Channel estimation system using an orthogonal sequence comprising a.

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