KR100860213B1 - Receiver with tap location variable adaptive equalizer and method for adaptive equalizing of multi path signal using the same - Google Patents

Abstract

The present invention relates to a receiver having a tap position variable adaptive equalizer capable of efficiently controlling the equalizer by adapting the tap position of the equalizer to the change of the multipath of the radio channel, and an adaptive equalization method using the same.

According to the present invention, a receiver having a variable tap position adaptive equalizer according to the present invention includes a path searcher searching for a multipath signal from a signal received at a receiver, and a multipath signal using the signal of the receiver and the output of the path searcher. A tap position converting processor for determining a tap position in correspondence with a signal distribution state, a tap position variable adaptive equalizer for performing adaptive equalization by applying a changed tap position according to the output of the tap position converting processor, and the tap position variable adaptation And a finger for performing demodulation by receiving the output of the equalizer.

According to the configuration of the present invention as described above, the efficiency of using the equalizer tap is increased, and the equalization is also possible for signals exceeding the window size.

Receiver, Adaptive Equalizer, Positionable Tap, Tap Position Conversion

Description

Receiver with tap location variable adaptive equalizer and method for adaptive equalizing of multi path signal using the same}

1 is a diagram illustrating a structure of a conventional rake receiver for removing intersymbol interference caused by a multipath signal.

2 illustrates a structure of a receiver having a chip level adaptive equalizer according to the prior art.

3 is a block diagram illustrating a receiver having a variable tap position adaptive equalizer according to an embodiment of the present invention.

4 is a view for explaining the operation of a receiver having a variable tap position adaptive equalizer according to the present invention;

5 is a flowchart illustrating an adaptive equalization method using a receiver having a variable tap position adaptive equalizer according to the present invention.

<Explanation of symbols for the main parts of the drawings>

310: tap position variable adaptive equalizer 320: finger

330: tap position conversion processing unit 331: signal distribution analysis unit

332: tap position determining unit 340: demux

350: route navigator

The present invention relates to an apparatus for adjusting the tap position of an adaptive equalizer according to a multi-path channel situation in a wireless communication system, and an adaptive equalization method using the same.

Recently, the demand for increasing the capacity of communication systems used in the mobile communication field is increasing year by year. Numerous techniques are being applied to this, one of which is a code division multiple access (CDMA) system. In particular, a system that is differentiated from the existing CDMA is being built around Japan and Europe, which is a wideband code division multiple access (W-CDMA) system. The W-CDMA system uses a wider frequency band than the conventional CDMA system, and a technology for guaranteeing a high data rate is applied. In particular, there is a trend to provide high quality service by applying high-speed downlink packet access (HSDPA).

The feature of CDMA is that several users use the same frequency band, and the differentiation of signals between users takes advantage of the orthogonality of the code. Therefore, the signal of another user acts as noise that degrades the quality of the magnetic signal. In addition, the characteristic of the wireless environment is that unlike a wired environment, a signal transmitted through an antenna has a large number of reflectors such as a building or a mountain. That is, inter-symbol interference (ISI) is generated through multipath propagation, thereby degrading the quality of the received signal.

The higher the data rate, the greater the impact of this ISI, and only if it is effectively filtered for high-quality data transmission services. To this end, an adaptive equalizer is introduced. The key is to apply the equalizer to the characteristics of the wireless channel that is different from the wired environment. As such, a rake receiver is used as an adaptive equalizer for multipath channel environment compensation in a wireless communication system.

FIG. 1 is a diagram illustrating a structure of a conventional rake receiver for removing intersymbol interference caused by a multipath signal.

As shown in FIG. 1, the conventional general rake receiver 100 searches for a multipath signal from a signal received by the signal receiver 101 through a plurality of paths to search for a signal for each path. 150 and a plurality of fingers 120a to 120n for receiving signals demultiplexed by the path searcher 150 to despread and convert the signal of a chip unit into a signal of a symbol unit; Combiner 130 for summing and outputting the data signals output from the plurality of fingers (120a to 120n) and demux 140 for demultiplexing and outputting the multiplexed signal output from the combiner 130 and the like It is configured to include.

The operation of the conventional general rake receiver 100 configured as described above will be described.

The signal received by the signal receiver 101 through the antenna of the terminal is input to the plurality of fingers 120a to 120n of the rake receiver 100 according to the path searched by the path searcher 150.

The plurality of fingers 120a to 120n despread the input signal to convert the signal in the chip unit into the signal in the symbol unit and output the signal.

The combiner 130 of the rake receiver 100 conjugates and multiplies the channel estimation value obtained by the channel estimator to output the channel compensation to the demux 140.

If the signal transmitted from the base station is received by the terminal through L multiple paths, the number of the plurality of fingers 120a to 120n becomes L and the combiner 130 of the rake receiver 100 L. The L-compensated L signals of the four fingers are combined and output by MRC (Maximal-Ratio-Combining) or the like.

On the other hand, the signal-to-noise ratio of the demodulated signal in each of the plurality of fingers (120a to 120n) is determined by the channel environment of each path and the degree to which the signal of each path acts as noise in the other path, the channel environment of each path If independent of each other, the signal-to-noise ratio of the signal combined in the combiner 130 is high.

In the CDMA system, the signal of each path is distinguished by a code when there is a difference of one chip or more. Therefore, a structure of separating and adding the signals of each path is possible. In this case, it is based on the premise that the signals in each path are independent of each other. Since the rake receiver structure sums the multipath signals, there is an advantage that the diversity effect can be obtained along with the effect of raising the signal-to-noise ratio.

However, the above structure shows a performance limit for ISI of a signal having a high data rate. Therefore, the adaptive equalizer is used as a method for effectively suppressing ISI. An adaptive equalizer is a circuit that removes and sums ISI between multipath signals and processes them at the receiver as signals transmitted over only one path.

The adaptive signal processing in the adaptive equalizer of the digital communication system receiver uses a reference signal included in the original signal and transmitted by the transmitter. The reference signal is a signal that is transmitted to sufficiently reflect the characteristics of the channel to the receiving apparatus. For example, the PN sequence (Pseudo Noise Sequence) corresponds to this. That is, the adaptive equalizer of the receiving device compares the reference signal known in advance with the reference signal included in the original signal converted according to the characteristics of the channel in the process of being transmitted through the channel from the transmitting device to minimize the difference between the two reference signals. The adaptation process is performed. Representative algorithms of the adaptive signal processing include a Least Mean Square (LMS) algorithm.

2 is a diagram illustrating a structure of a receiver having a chip level adaptive equalizer according to the prior art.

As shown in FIG. 2, a receiver having a chip level adaptive equalizer according to the prior art includes:

A chip level adaptive equalizer 210 for outputting the sum of the multipath signals from which the ISI has been removed after removing the ISI between the multipath signals;

And a finger 220 and a demux for despreading and outputting the signal output from the chip level adaptive equalizer 210.

In the receiver having the chip level adaptive equalizer according to the related art configured as described above, the chip level adaptive equalizer 210 performs equalization before despreading the signal at the finger 220. When the equalization is performed at the chip level with respect to the received signal, the demodulator input terminal can remove the ISI between the respective paths and thus look like a single path signal, thereby demodulating the signal with one finger 220.

However, in the chip level adaptive equalizer 210 according to the conventional method, the signal sampled from the taps 211 (T1 to T8) arranged at regular intervals should be multiplied by a coefficient, but the total number of taps is determined. As a result, signals beyond the size of the equalizer cannot be processed. In other words, equalization cannot be performed on signals s9 and s10 outside the size of the equalizer due to the limit of the number of taps and the number of adaptive equalizers arranged at regular intervals.

In addition, even if the signal within the window size of the equalizer is not distributed over the entire area in the window, there is a disadvantage that the utilization efficiency of each tap (T5, T6) in the adaptive equalizer is inferior.

According to the present invention, by assigning each tap of the equalizer to a path having a strong signal component according to the signal distribution of the multipath signal found in the path searcher, it is possible to increase the efficiency of using the equalizer tap and to equalize the signal beyond the window size. It is an object of the present invention to provide a receiver having a variable tap position adaptive equalizer and an adaptive equalization method using the same.

In order to achieve the above object, a receiver having a variable tap position adaptive equalizer according to the present invention includes a path searcher for searching for a multipath signal from a signal received at a receiver, and a signal of the receiver and an output of the path searcher. A tap position converting processor for determining a tap position in response to a signal distribution state of a multi-path signal, a tap position variable adaptive equalizer for performing adaptive equalization by applying a changed tap position according to the output of the tap position converting processor, and the tap And a finger for performing demodulation by receiving the output of the position-adaptive adaptive equalizer.

The tap position conversion processor may include a signal distribution analyzer configured to analyze and output a signal distribution state of a multipath signal by using the signal of the receiver and an output of a multipath searcher, and a multipath signal according to the output of the signal distribution analyzer. And a tap position determiner configured to determine the tap position in correspondence with the signal distribution state.

In order to achieve the above object, an adaptive equalization method using a receiver having a variable tap position adaptive equalizer according to the present invention includes periodically analyzing signal distribution of a multipath signal, and analyzing the signal distribution of the analyzed multipath signal. And determining the position of each tap for the signal processing according to the present invention, and performing an adaptive equalization by applying the determined position of the tap.

The analyzing of the distribution of the multipath signal may include searching for a multipath signal from a received signal and analyzing a signal distribution state of the searched multipath signal.

The searching of the signal distribution of the multipath signal may include searching for a signal distribution by filtering the received multipath signal longer than a coherence time.

Hereinafter, a receiver having a variable tap position adaptive equalizer according to the present invention and an adaptive equalization method using the same will be described in detail with reference to the accompanying drawings.

3 is a block diagram illustrating a receiver having a variable tap position adaptive equalizer according to an embodiment of the present invention.

As shown in FIG. 3, a receiver including a variable tap position adaptive equalizer according to an embodiment of the present invention includes a variable tap position adaptive equalizer 310, a finger 320, and a tap position converting processor 330. ), A demux 340, a path searcher 350, and the like.

The path searcher 350 receives the signals of the multipath received through the antenna from the signal receiver 301, searches for each signal according to the multipath, and outputs a signal for each path.

The tap position conversion processor 330 determines the tap position in correspondence with the signal distribution state of the multi-path signal by using the signal of the signal receiver 3010 and the output of the path searcher 350 and outputs the tap position.

To this end, the tap position conversion processing unit 330, the signal distribution analysis unit 331 for analyzing and outputting the signal distribution state of the multi-path signal using the signal of the receiver and the output of the multi-path searcher, and the signal distribution analysis And a tap position determiner 332 which determines the tap position in response to the signal distribution state of the multipath signal according to the negative output.

The variable tap position adaptive equalizer 310 applies an adaptive equalization to a signal of a multipath received through an antenna by the signal receiver 301 by applying a changed tap position according to the output of the tap position converter 330. Run it and print it out.

The finger 320 receives the output of the variable tap position adaptive equalizer and demodulates the output.

The demux 140 demultiplexes the multiplexed signal output from the finger 320 and outputs the demultiplexed signal.

An operation of a receiver having a variable tap position adaptive equalizer and an adaptive equalization method using the same according to an embodiment of the present invention configured as described above will be described.

 4 is a view for explaining the operation of a receiver having a variable tap position adaptive equalizer according to the present invention, Figure 5 is a diagram for explaining an adaptive equalization method using a receiver having a variable tap position adaptive equalizer according to the present invention It is a flow chart.

The distribution of the multipath signal is determined by the peripheral reflectors of the receiver and as the receiver moves the distribution of the received signal changes. When the distribution of the received signal changes over time, the equalization is performed using all the received signals. In the case of the chip level adaptive equalizer, the number of taps required increases.

For example, when the distribution of the signal received by the signal receiving unit 301 at a predetermined time is shown as shown in FIG. 4, in the case of the conventional method, the adaptive equalization is performed using all the received signals. T1 to t12 Twelve taps are required for the processing of the signal up to, thus increasing the hardware and the amount of computation required for the signal processing. In addition, since the taps T01 to T04 allocated for signal processing corresponding to t5, t6 and t9 and t10 having no signal are used unnecessarily, it is difficult to efficiently use the taps provided in the adaptive equalizer.

In addition, in the case of using only a tap limited to a certain number of sizes, a signal corresponding to S7 and S8 of the received signals is missed, thereby degrading the performance of the receiver.

Accordingly, the tap position conversion processing unit 330 of the receiver having the variable tap position adaptive equalizer according to the present invention is input to the variable tap position adaptive equalizer 310 according to the distribution of the multipaths searched by the path searcher 350. The tap 310 for processing each signal is appropriately allocated according to the signal distribution.

To this end, the path searcher 350 receives the signals of the multipath received from the signal receiver 301 and searches the signals for each path according to the multipath at predetermined time intervals, and then converts the search results into the tap position conversion processor 330. Output (S510).

The signal distribution analyzer 331 of the tap position conversion processor 330 analyzes and outputs a signal distribution state of the multipath signal received from the signal receiver 301 using the output of the path detector 350. (S520).

In the analyzing of the signal distribution of the multipath signal (S520), it is preferable to analyze the signal distribution by filtering the received multipath signal longer than the coherence time. This is because the distribution of the multipath signal changes from time to time depending on the channel environment and detects signals beyond the window size of the adaptive equalizer. This is to make more use of the signal transmitted from the base station.

Referring to FIG. 4, the signal distribution analyzer 331 detects signals S1 to S8 as the strongest signals, and outputs information including detection information about S7 and S8 signals that are excluded in the conventional process. do.

The tap position determining unit 332 of the tap position conversion processing unit 330 is a tap position variable adaptive equalizer 310 in a path having a strong signal component according to the signal distribution of the multipath signal output from the signal distribution analyzer 331. In order to allocate each tap 311 (T1 to T8), the allocation position of the tap is determined, and a control signal is output to the tap position variable adaptive equalizer 310 (S530).

That is, the positions of the taps are allocated so that the signals of S1 to S8 can be processed by the plurality of taps 311 to T8.

Accordingly, the tap position variable adaptive equalizer 310 applies the equalization position of the determined tap 312 to perform adaptive equalization on the multipath signal received from the signal receiver 301 (S540).

That is, in the plurality of taps 311 (T1 to T8) of the tap position variable adaptive equalizer 310, coefficients are multiplied by a sampled signal for signals S1 to S8 input to each tap. And the sum unit 312 of the tap position variable adaptive equalizer 310 adds the respective outputs of the plurality of input taps 311 (T1 to T8) to output the summed signal to the finger 320. It becomes (S550).

Therefore, since no taps for signal processing are allocated to t5, t6 and t9, t10 for which no signal is detected, unnecessary use of taps T01 and T02 for signal processing is prevented, and instead, at t11 and t12. The performance of the receiver is improved by adding the signal components S7 and S8, which are valid signals, by the taps T7 and T8 allocated for the corresponding signal processing.

Thereafter, the finger 320 receives the output of the variable tap position adaptive equalizer 310 and despreads it, converts the signal of the chip unit into the signal of the symbol unit, and outputs the signal to the demux 340. .

The demux 340 receives the signal in the symbol unit and demultiplexes it and outputs the signal.

In the above, the operation of a receiver having a variable tap position adaptive equalizer and an adaptive equalization method using the same have been described in detail. However, the present invention is not limited thereto, and the present invention is included in the present invention even if changes and modifications are made without departing from the basic spirit of the present invention, and the facts will be apparent to those skilled in the art.

According to an operation of a receiver having a variable tap position adaptive equalizer and an adaptive equalization method using the same according to the present invention, an adaptation to a signal beyond a window size without increasing the number of taps used or the amount of computation required accordingly Equalization is possible.

In addition, since the position of each tap used in an adaptive equalizer of a receiver having a variable tap position adaptive equalizer according to the present invention is variable, it can be used for combining a dedicated subscriber channel (DPCH) during soft handover of W-CDMA. There is an advantage. In particular, in the case of W-CDMA, signal processing using an equalizer can be performed even for a signal having a large time difference between signals transmitted from each base station during soft handover.

Claims (5)

A path searcher for searching for a multipath signal from the signal received by the receiver; A tap position converting processor configured to determine a tap position in correspondence with the signal distribution state of the multipath signal by using the signal of the receiver and the output of the multipath searcher; A tap position variable adaptive equalizer for performing adaptive equalization by applying the changed tap position according to the output of the tap position conversion processing unit; And a finger for performing demodulation by receiving the output of the variable tap position adaptive equalizer. The method of claim 1, wherein the tap position conversion processing unit, A signal distribution analyzer configured to analyze and output a signal distribution state of the multipath signal by using the signal of the receiver and the output of the multipath searcher; And a tap position determining unit configured to determine a tap position in response to a signal distribution state of a multipath signal according to an output of the signal distribution analyzer. Periodically analyzing a signal distribution state of the multipath signal; Determining the position of each tap for signal processing according to the signal distribution of the analyzed multipath signal; And performing adaptive equalization by applying the determined position of the tap. 12. The adaptive equalization method using a receiver having a variable tap position adaptive equalizer. The method of claim 3, wherein analyzing the signal distribution of the multipath signal comprises: Searching for a multipath signal from the received signal; And analyzing a signal distribution state of the searched multipath signal. The method of claim 4, wherein analyzing the signal distribution of the searched multipath signal comprises: An adaptive equalization method using a receiver having a variable tap position adaptive equalizer, characterized in that the signal distribution is analyzed by filtering the received multipath signal longer than the coherence time.

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