KR101496504B1 - Receiving apparatus for single carrier frequency division multiple access and method for channel equaling thereof - Google Patents

Abstract

The present invention relates to a receiving apparatus and a channel equalizing method for a single carrier frequency division multiple access (OFDM) system, and more particularly, to a channel equalizing method using overlaying in a receiver of a single carrier frequency division multiple access transmission system. The present invention relates to a receiving apparatus for a single carrier frequency division multiple access (SC-FDMA) system, in which a sampling interval obtained by dividing the length of one OFDM block by the number of useful periods and the guard interval is set to an overhead a fast Fourier transform processor for fast Fourier transforming a signal of the oversampled baseband SC-FDMA sampled signal with a guard interval removed, and outputting a frequency-domain SC-FDMA symbol; A channel equalizer for receiving the SC-FDMA symbols in the frequency domain and channel-equalizing the user signals in consideration of channel characteristics; An inverse fast Fourier transform processor for performing an inverse fast Fourier transform on the channel equalized SC-FDMA signal by the channel equalizer to a size considering oversampling and outputting a time-domain SC-FDMA signal; And a decision feedback equalizer for linearly filtering the output SC-FDMA signal of the inverse fast Fourier transform processor and performing down sampling on a multiple of the received signal considering oversampling and then performing channel equalization in a time domain to output a final demodulated signal of the SC- A receiving apparatus and a channel equalizing method for a single carrier frequency division multiple access system are provided.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus for a single carrier frequency division multiple access system and a channel equalizing method for a single carrier frequency division multiple access (OFDMA) system,

The present invention relates to a receiving apparatus and a channel equalizing method for a single carrier frequency division multiple access (OFDM) system, and more particularly, to a channel equalizing method using overlaying in a receiver of a single carrier frequency division multiple access transmission system.

In the 3GPP LTE system, which is a next generation mobile communication, the uplink uses a single-carrier frequency division multiple access (SC-FDMA) scheme.

The SC-FDMA scheme can reduce the complexity of the channel equalizer differently from the conventional single carrier scheme by implementing a channel equalizer in the frequency domain.

Meanwhile, in addition to the frequency domain channel equalizer, a time domain decision feedback equalizer may be used together to improve the performance of the receiver, and such a structure will be described with reference to the accompanying drawings.

1 is a block diagram illustrating an equalizer configuration of a conventional SC-FDMA receiver.

Referring to FIG. 1, a conventional SC-FDMA receiver samples a baseband SC-FDMA signal at a symbol interval and inputs the output to a guard interval remover to remove a guard interval. At this time, the SC-FDMA sample signal sampled at symbol intervals and input to the guard interval canceller is shown as a continuous form of an OFDM (Orthogonal Frequency Division Multiplexing) block composed of Ng guard intervals and N usable intervals as shown in FIG. 2 .

The output of the guard interval eliminator is such that the previous Ng samples are removed and the remaining N useful intervals are displayed continuously. Since a plurality of consecutively transmitted blocks have the same structure as one block, only one OFDM block will be described below.

When the length of one OFDM block is Ts, it is composed of (N + Ng) samples, so the sampling interval at symbol interval sampling is Ts / (N + Ng).

N samples of the useful section, which is the output of the guard interval eliminator, are input to a serial-parallel converter (S / P, Serial-Parallel) and are converted into parallel. The parallel-transformed N samples perform an N-point FFT through an N-point FFT (Fast Fourier Transform) processor. The output of the N-point FFT processor is a multiplexed signal of several users with N subcarrier components.

Therefore, M samples (subcarrier components) corresponding to one user are extracted through a user extractor. Since the channel between the transmitter and the receiver is different for each user, channel equalization is performed on each extracted user signal.

In general, there is a relation of N = kM (k is an integer) between the total number of subcarriers N and the number of subcarriers M of each user. Here, it is assumed that the channel characteristics necessary for channel equalization are already known.

Signals of other users are processed in the same manner, and only one user signal is considered here.

The channel equalized signal is input to an IFFT (Inverse FFT) processor to perform an M point IFFT. The IFFT output is a time-domain signal composed of M samples. Since this signal is a parallel signal, it is converted into M serial signals through a parallel-to-serial converter (P / S).

The M signals are sequentially input to a linear filter whose z-transform is V (z). Is subtracted from the output of the feedback filter whose characteristic is V (z) -1 at the output of the linear filter, and is determined according to the signal point transmitted to the determiner and transmitted. The output of the decision unit is the final demodulated signal of the SC-FDMA signal, and at the same time this output is fed back to the feedback filter.

However, the conventional SC-FDMA receiver has a problem in that a timing error occurs in sampling the received signal.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a receiver for a single carrier frequency division multiple access system, And a channel equalizing method therefor.

It is another object of the present invention to provide a receiving apparatus and a receiving apparatus for a single carrier frequency division multiple access system in which a received signal is overexposed so as not to be sensitive to a timing error with respect to a sampling instant, And to provide the channel equalization method.

It is still another object of the present invention to provide a receiving apparatus and a channel equalizing method for a single carrier frequency division multiple access system in which a partial interval equalizer can be applied in frequency domain and time domain to equalize overexposed samples .

According to another aspect of the present invention, there is provided a receiving apparatus for a single carrier frequency division multiple access (SC-FDMA) system, Of the baseband SC-FDMA sampled signal obtained by dividing the length of the guard interval by the number of the guard interval and the usable interval is oversampled. A fast Fourier transform processor for outputting an SC-FDMA symbol in a frequency domain; A channel equalizer for receiving the SC-FDMA symbols in the frequency domain and channel-equalizing the user signals in consideration of channel characteristics; An inverse fast Fourier transform processor for performing an inverse fast Fourier transform on the channel equalized SC-FDMA signal by the channel equalizer to a size considering oversampling and outputting a time-domain SC-FDMA signal; And a decision feedback equalizer for linearly filtering the output SC-FDMA signal of the inverse fast Fourier transform processor and performing down sampling on a multiple of the received signal considering oversampling and then performing channel equalization in a time domain to output a final demodulated signal of the SC- .

Preferably, the sampling interval is Ts / 2 (N + Ng), wherein the sampling interval is twice the length (Ts) of one OFDM block during overexposure, 2Ng guard intervals and 2N useful intervals.

Preferably, the decision feedback equalizer includes: a linear filter for performing z-conversion sequentially on an SC-FDMA signal in a time domain transformed by inverse fast Fourier transform to filter noise in a time domain; A descending sampling unit for descrambling the signal filtered by the linear filter and outputting the sampled signal in a multiple of the oversampling; A calculator for subtracting the feedback-filtered signal from the down-sampling filtering signal output by the down-sampling unit and outputting the result; A determiner that compares a signal point corresponding to an output signal of the computing unit with a threshold value and determines that the final demodulation signal of the SC-FDMA signal can be output according to the comparison result; And a feedback filter that receives the final demodulation signal output from the demodulator and performs z-1 conversion to feed back the feedback-filtered signal to the operator.

A channel equalization method of a receiver for a single carrier frequency division multiple access system according to another aspect of the present invention is a channel equalization method of a receiver for a single carrier frequency division multiple access (SC-FDMA) system, In the SC-FDMA sampled signal with a sampling rate that is obtained by dividing the length of the block by the number of guard intervals and the usable intervals, the guard interval is removed, Converting; And SC-FDMA symbols in a frequency domain obtained by the fast Fourier transform are channel-equalized with respect to a user signal in consideration of a channel characteristic, and the channel-equalized SC-FDMA signals are subjected to inverse fast Fourier transform And performing a first linear filtering on the SC-FDMA signal in the time domain to output a final demodulated signal of the SC-FDMA signal by channel-equalizing in a time domain.

Preferably, the sampling interval is Ts / 2 (N + Ng), wherein the sampling interval is twice the length (Ts) of one OFDM block during overexposure, 2Ng guard intervals and 2N useful intervals.

Preferably, the step of outputting the final demodulated signal comprises: z-converting sequentially the time-domain SC-FDMA signals transformed by the inverse fast Fourier transform to filter the noise in the time domain, And outputs the final demodulated signal of the SC-FDMA signal according to the result of the comparison. In this case, the down sampled filtered signal is output as a result of the comparison. And the feedback signal is fed back by receiving the final demodulation signal and performing z-1 conversion on the feedback signal.

In order to improve the performance of a conventional channel equalizer used in an SC-FDMA receiver, the present invention adopts oversampling and uses a partial interval equalizer to reduce the influence of a timing error And the equalization performance can be improved by the partial interval equalizer.

1 is a block diagram showing an equalizer configuration of a conventional SC-FDMA receiver;
FIG. 2 is a diagram illustrating the structure of one OFDM block signal when the SC-FDMA reception signal is symbol-spaced sampled in FIG.
3 is a block diagram illustrating a receiving apparatus for an SC-FDMA system according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating the structure of one OFDM block signal when the SC-FDMA reception signal is symbol-spaced sampled in FIG.
5 and 6 are flowcharts illustrating a channel equalization method of a receiving apparatus for an SC-FDMA system according to an embodiment of the present invention.

In the following description, specific details of a receiving apparatus and a channel equalization method for a single carrier frequency division multiple access system of the present invention are shown in order to provide a more thorough understanding of the present invention, It will be apparent to those skilled in the art that the present invention can be readily practiced by those skilled in the art.

In order to facilitate understanding of overexposure of the present invention, the following description will be made by way of example of double-overimposing. However, since this is merely to assist understanding of the present invention, It can be an integer multiple or a multiple integer multiple.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings, with reference to the parts necessary for understanding the operation and operation according to the present invention.

3 is a block diagram illustrating a receiver for a single carrier frequency division multiple access system according to an embodiment of the present invention.

3, a reception apparatus 100 for a single carrier frequency division multiple access system according to the present invention includes a guard interval eliminator 11, an S / P 13, an FFT processor 15, An equalizer 17, a channel equalizer 19, an IFFT processor 21, a P / S 23, a decision feedback equalizer 30, and the like.

The guard interval remover 11 doubles the received baseband SC-FDMA signal so that the sampling interval is T / 2 (N + Ng). In this case, since one OFDM block has a structure as shown in FIG. 4, 2 Ng samples corresponding to the guard interval are removed through the guard interval eliminator. Overlapping can be both integer and non-integer.

The S / P 13 converts 2N remaining usable sections outputted through the guard interval eliminator 11 from serial to parallel.

The FFT processor 15 calculates a guard interval of a baseband SC-FDMA sampled signal obtained by over sampling the sampling interval obtained by dividing the length of one OFDM block by the number of guard intervals and usable intervals, Performs a 2N point FFT by fast Fourier transforming the removed signal into a size considering oversampling and outputting a frequency-domain SC-FDMA symbol (2N subcarrier components).

The user extracting unit 17 extracts 2M samples (subcarrier components) corresponding to one user since the output of the FFT processor 13 is a multiplexed signal of several users with 2N subcarrier components.

Since the channel between the transmitter and the receiver is different for each user, channel equalization is performed on each extracted user signal.

The channel equalizer 19 receives the SC-FDMA symbols of the frequency domain from the 2M samples extracted from one user and channel-equalizes the user signals in consideration of the channel characteristics.

The IFFT processor 21 performs an inverse fast Fourier transform on the channel equalized SC-FDMA signal by a channel equalizer 19 to a size considering oversampling, and outputs the time-domain SC-FDMA signal.

The P / S 23 converts the parallel signal of the IFFT processor 21 back into 2M serial signals. Thereafter, the 2M serial signals are sequentially input to the decision feedback equalizer 30.

The decision feedback equalizer 30 receives the SC-FDMA signal, which is the output of the P / S 23, and linearly filters the signal, downsamples the downsampled signal in consideration of oversampling, And outputs a demodulation signal. The decision feedback equalizer 30 includes a linear filter 31 for performing z-conversion sequentially on the 2M SC-FDMA signals in the time domain converted by the inverse fast Fourier transform to filter the noise in the time domain, a linear filter A down sampling unit 33 for down sampling the signal filtered by the sampling filter 31 by a multiple of 1/2 in consideration of overexposure and outputting a down sampling filtered signal output by the down sampling unit 33, And a decision unit 35 for comparing the signal point according to the output signal of the computing unit 35 with a threshold value and determining that the final demodulation signal of the SC-FDMA signal can be outputted according to the comparison result, And a feedback filter 39 that receives the final demodulation signal output from the demodulator 37 and performs z-1 conversion to feed back the feedback-filtered signal to the calculator 35. Here, the coefficient of the decision feedback equalizer 30 is determined so that the frequency response is equal to V (z) obtained by adding 1 to the z-transform of the feedback filter.

5 and 6 are flowcharts illustrating a channel equalization method of a receiving apparatus for an SC-FDMA system according to an embodiment of the present invention.

Referring to FIGs. 5 and 6, a protection interval of an oversampled baseband SC-FDMA sample signal obtained by dividing the length of one OFDM block by the number of guard intervals and usable intervals is a fixed ratio The removed signal is subjected to fast Fourier transform to a size considering overexposure (S510).

Then, the SC-FDMA symbols in the frequency domain obtained by the fast Fourier transform are channel-equalized with respect to the user signals in consideration of the channel characteristics, and the channel equalized SC-FDMA signals are subjected to inverse fast Fourier transform (Step S520). In step S520, the SC-FDMA signal is subjected to a first linear filtering and down-sampled down to a multiple of oversampling, followed by channel equalization in a time domain to output a final demodulated signal of the SC-FDMA signal.

As shown in FIG. 6, in operation 520, the SC-FDMA signal in the time domain transformed by the inverse fast Fourier transform is sequentially subjected to z transform to filter the noise in the time domain, The down sampled filtered signal obtained by down sampling with respect to overhead sampling is subtracted from the feedback filtered signal and the signal point according to the output signal is compared with a threshold value and the final demodulated signal of the SC- (Step S521). At this time, when performing the step 521 (S521), the final demodulation signal is received and z-1 conversion is performed to feed back the feedback-filtered signal (S523).

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Claims (6)

A receiver for a single carrier frequency division multiple access (SC-FDMA) system,
The length of one OFDM block is divided by the number of the guard interval and the usable interval, and the signal obtained by removing the guard interval of the baseband SC-FDMA sampled signal in which the sampling interval is oversampled at a certain rate is divided into a size A fast Fourier transform processor for performing fast Fourier transform on the frequency domain and outputting the SC-FDMA symbol in the frequency domain;
A channel equalizer for receiving the SC-FDMA symbols in the frequency domain and channel-equalizing the user signals in consideration of channel characteristics;
An inverse fast Fourier transform processor for performing an inverse fast Fourier transform on the channel equalized SC-FDMA signal by the channel equalizer to a size considering oversampling and outputting a time-domain SC-FDMA signal; And
And a decision feedback equalizer for linearly filtering the output SC-FDMA signal of the inverse fast Fourier transform processor and performing down sampling on a multiple of the overhead considering the oversampling and then channel equalizing in the time domain to output a final demodulated signal of the SC- Receiving apparatus for a single carrier frequency division multiple access system.
2. The method of claim 1,
(N + Ng), which is composed of a length (Ts) of one OFDM block and a 2Ng guard interval and 2N useful intervals at the time of double oversampling. Receiving device.
The apparatus of claim 1, wherein the decision feedback equalizer comprises:
A linear filter for performing z-conversion sequentially on an SC-FDMA signal (the number of subcarriers of each user) in a time domain transformed by inverse fast Fourier transform to filter noise in a time domain;
A descending sampling unit for descrambling the signal filtered by the linear filter and outputting the sampled signal in a multiple of the oversampling;
A calculator for subtracting the feedback-filtered signal from the down-sampling filtering signal output by the down-sampling unit and outputting the result;
A determiner that compares a signal point corresponding to an output signal of the computing unit with a threshold value and determines that the final demodulation signal of the SC-FDMA signal can be output according to the comparison result; And
And a feedback filter for receiving the final demodulation signal output from the demodulator and performing z-1 conversion to feed back the feedback-filtered signal to the calculator. .
A channel equalization method of a receiver for a single carrier frequency division multiple access (SC-FDMA) system,
The length of one OFDM block is divided by the number of the guard interval and the usable interval, and the SC-FDMA sampled signal of the oversampled sampling rate obtained by dividing the guard interval by the number of the guard interval is divided into a size To a fast Fourier transform; And
The SC-FDMA symbols in the frequency domain obtained by the fast Fourier transform are channel-equalized with respect to the user signals in consideration of the channel characteristics, and the channel-equalized SC-FDMA signals are obtained by inverse fast Fourier transform A first linear filtering of the SC-FDMA signal in the time domain, a down sampling in a multiple of the overhead view, and a channel equalization in the time domain to output a final demodulated signal of the SC-FDMA signal. A channel equalization method of a receiver for a frequency division multiple access system.
5. The method of claim 4,
(N + Ng), which is composed of a length (Ts) of one OFDM block and a 2Ng guard interval and 2N useful intervals at the time of double oversampling. A method of channel equalization of a receiving device.
5. The method of claim 4, wherein outputting the final demodulated signal comprises:
The noise is time-domain filtered by sequentially performing z-transform on the time-domain SC-FDMA signal transformed by the inverse fast Fourier transform, and the down-sampled filtered signal obtained by downsampling the filtered signal by a multiple of over- Filtering the feedback-filtered signal and comparing the signal point according to the output signal with a threshold value, and determining that the final demodulated signal of the SC-FDMA signal can be output according to the comparison result,
And the feedback signal is fed back by performing a z-1 conversion on the final demodulated signal, and feeding back the feedback-filtered signal to the receiving apparatus for the single carrier frequency division multiple access system.

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