KR100391293B1 - An interference cancellation receiver and control method thereof for TDD-CDMA system - Google Patents

Abstract

The present invention relates to a multi-user interference cancellation receiver and an interference cancellation control method for a TD-CD system, and to eliminate interference signal components among multiple users of a TD-CD system. The present invention relates to a multi-user interference cancellation receiver for a TD-CD-M system that can reduce the data throughput required for interference cancellation processing while performing interference cancellation processing, and can reduce errors even when the power difference of each user signal is large. The interference cancellation screening unit 300 extracts channel information using the midamble signal from the received original signals and selects and outputs the first interference elimination target user, and receives the data portion of the received signal. The primary interference elimination target user selected at 300 is first performed parallel interference elimination and regeneration is performed. The second stage interference cancellation block 400 for outputting a call and the data portion of the received signal are received and the second parallel interference cancellation is performed by using the first reproduction signal output from the first stage interference cancellation block 400. It comprises a second stage interference elimination block 500 for outputting.

Description

{An interference cancellation receiver and control method about for TDD-CDMA system}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Time Division Duplex (Code Division Multiple Access) system (TDD-CDMA), and more specifically, to a TDD-CDMA system. In removing interference signal components among multiple users of the A-system, by considering the reliability of each received signal component, the interference cancellation processing can be efficiently performed by the multiplex for CD-CD system It relates to a user interference cancellation receiver and an interference cancellation control method.

In general, the wireless transmission technology adopts a CDM method, and uses a Frequency Division Duplex (FDD) CDM method and a TVD CDM according to a division duplex method. It can be largely divided in this way.

In the TDM-CD system, a frame is divided into a plurality of time slots and used for forward and reverse signal transmission. Multiple access is supported through this. In such a code division system, interference between multiple users occurs due to time delay caused by reflected waves.

In order to solve the problems caused by such interference, an interference canceller is used. The interference canceller may be divided into a parallel interference canceller and a serial interference canceller, and the parallel interference canceller and the serial interference canceller of the prior art are shown in FIGS. It is.

Hereinafter, a parallel interference canceller of the prior art will be described with reference to the accompanying drawings.

As shown in FIG. 1, in the parallel interference canceller of the prior art, a plurality of stages of interference cancellation blocks 10, 20, and 30 are connected in series, wherein the second interference cancellation block 20 is an adder ADD20. , The interference cancellation unit 21, 22, ..., 2x corresponding to the number of multi-users.

As shown in FIG. 2, the first interference canceling unit 21 includes an adder 1 for adding a signal output from the adder ADD20 and a signal of a corresponding user reproduced at a previous stage, and the adder 1. A first multiplier 2 for generating a demodulated signal by receiving a signal output from the signal and user information of the corresponding signal, and a matched filter for extracting an information string from a signal output from the first multiplier 2; 3), a signal value determiner 4 for determining the value of the signal output from the matched filter 3, and a reproduced signal is generated using the user information on the signal output from the signal value determiner 4, and then generated. The second multiplier 5 outputs to the stage 30.

The configuration of the second interference elimination unit 22 to the x-th interference elimination unit 2x is the same as that of the first interference elimination unit 21, and description thereof is omitted to avoid duplication.

In addition, since the first interference elimination block 10 and the third interference elimination block 30 are configured in the same manner as the second interference elimination block 20, description thereof will be omitted.

Operation of the prior art parallel interference canceller made as described above is as follows.

In FIG. 1, 'x' means the number of multi-users. Each received signal is subjected to interference cancellation signal processing in parallel, and after the interference cancellation processing is performed in the first interference cancellation block 10, the signal is decoded. After receiving the input from the second interference cancellation block 20 and performing the interference cancellation process again, the processed signal is input again from the third interference cancellation block 30 to perform the interference cancellation process.

Here, referring to the operation of the second interference canceling block 20, the adder ADD20 is canceled and reproduced in the first interference canceling block 10, which is the previous stage in the entire received signal t-sT. Signals for each time slot , ,… , ) Is supplied to each user-specific interference canceling unit (21, 22, ..., 2x).

Then, each user-specific interference canceling unit (21, 22, ..., 2x) receives the signal output from the adder (ADD20) and the signal reproduced by the interference cancellation for each user of the front end, the user's signal Remove secondary interference.

Referring to FIG. 2, the interference elimination operation of the signal of the first user is described. The first adder 1 is a corresponding user of the first interference elimination block 10 which is a front end of the signal output from the adder ADD20. The interference canceling unit 11 (not shown) first receives and adds a signal reproduced by removing interference.

The signal output from the adder 1 is multiplied by user information such as a spreading code and a scrambling code of the corresponding user to demodulate the signal of the corresponding time slot.

The matched filter 3 receives a signal output from the multiplier 2, extracts signals of a corresponding user, and the signal value determiner 4 receives the signal and receives a signal value of more than a predetermined value and less than a predetermined value. Complete the demodulation by correctly determining.

The second multiplier 5 receives the signal output from the signal value determiner 4 and reproduces the signal of the corresponding user as a signal that can be transmitted using user information such as a spreading code and a scrambling code. .

The second interference canceling unit 22 to the x-th interference canceling unit 2x are operated in the same manner as the first interference canceling unit 21 performs the interference cancellation processing operation on the signal of the first user. The signal of the signal to the x-th user is subjected to interference cancellation.

In addition, the third interference cancellation block 30 receives the reproduced signals after the above-described interference elimination processing operation is completed, and performs interference elimination processing once again with the same operation, thereby increasing the interference elimination rate between the overall signals. .

Similarly, the first interference cancellation block 10 provides a signal to the second interference cancellation block 20 by performing primary interference cancellation in the same manner as the second interference cancellation block 20.

By the way, the prior art parallel interference canceller has a good signal quality due to interference cancellation when the power values of the users are similar, but when the power difference between users is large, the signal quality of the user whose power value is low due to the interference cancellation is high. There is a downside to falling.

Due to the above disadvantages, a series interference canceller is used when the power difference between users is large, an example of which is illustrated in FIGS. 3 and 4.

Hereinafter, a series interference canceller of the prior art will be described with reference to the accompanying drawings.

As shown in FIG. 3, the serial interference eliminator of the prior art is connected to the multi-level interference elimination blocks 40, 50, and 60, wherein the first interference elimination block 40 corresponds to the number of users. And an adder (ADD40) for summing signals output from the interference canceling units (41, 42, ..., 4x), respectively.

As shown in FIG. 4, the first interference canceling unit 41 receives a first received signal {varupsilon _1} ^ 1 and demodulates the first multiplier 71 by using the information signal of the corresponding user. A matching filter 72 for extracting a desired information string from the signal output from the first multiplier 71, a signal value determiner 73 for determining a value of a signal output from the matching filter 72, and the signal; A second multiplier 74 that generates and outputs a reproduction signal by using user information to the signal output from the value determiner 73, and receives the entire received signal from the first multiplier 71 to the second multiplier 74; A delayer 75 for delaying and outputting a delayed time as much as required, and an adder 76 for removing and outputting a signal output from the second multiplier 74 from a signal output from the delayer 75. Is done.

The configuration of the second interference elimination unit 42 to the x-th interference elimination unit 4x is the same as that of the first interference elimination unit 41, and description thereof is omitted to avoid duplication.

In addition, since the second interference elimination block 50 and the third interference elimination block 60 are configured in the same manner as the first interference elimination block 40, description thereof will be omitted.

The operation of the prior art series interference canceller made as above is as follows.

Referring to FIG. 3, the interference cancellation signal processing is performed serially for each time user. After the interference cancellation processing is performed in the first interference cancellation block 40, the signal is received from the second interference cancellation block 50. The interference elimination process is performed again, and the processed signal is received from the third interference elimination block 60 to perform the interference elimination process.

Here, referring to the operation of the first interference cancellation block 40, the first interference cancellation unit 41 receives the entire received signal {varupsilon _1} ^ 1 and extracts only the signal corresponding to the first user to remove the interference. The second interference canceller 42 outputs a first user signal processed by the interference canceling signal from the first interference canceller 41 in the entire received signal {varupsilon _1} ^ 1. Signal except) ), Only the signal corresponding to the second user is extracted, the interference is removed, and the output is performed.

In addition, the adder ADD40 may include the interference canceled signals corresponding to the respective users ( , ,… , ) Is added to generate a received signal before the interference cancellation and output to the second interference cancellation block 50, which is the next stage.

Referring to FIG. 4, the operation of the first interference canceller 41 will be described in detail. The first multiplier 71 receives an entire received signal and receives an information signal Inf1 such as a spreading code and a scrambling code of a corresponding user. And demodulate using the filter, and the matching filter 72 receives the signal to extract the corresponding information string, and the signal value determiner 73 receives the signal to accurately determine and output the signal value.

In addition, the second multiplier 74 receives the signal output from the signal value determiner 73 and reproduces and outputs a signal which can be transmitted using the information signal of the corresponding user.

In addition, the delay unit 75 receives the entire received signal and outputs the delayed signal as much as the time required for signal processing from the first multiplier 71 to the second multiplier 74, and the adder 76 outputs the delay unit. Receives the signal output from the (75) and subtracts the regenerated signal output from the second multiplier 74 and outputs to the second interference canceler (42).

Then, the second interference canceller 42 receives a signal from which the information of the first user is excluded from all received signals output from the adder 76, and operates in the same manner as the first interference canceller 41. Do this.

The third interference eliminator 43 to the x-th interference eliminator 4x also operate in the same manner as the first interference eliminator 41, and description thereof will be omitted to avoid duplication.

Similarly, the second interference cancellation block 50 performs an interference cancellation operation using the signal output from the adder ADD40 of the first interference cancellation block, and the third interference cancellation block 60 is also performed. The interference output operation is performed by receiving the signal output from the second interference cancellation block 50, thereby improving the efficiency of interference cancellation and improving the signal quality.

By the way, the conventional serial interference canceller as described above can reduce the error due to interference cancellation compared to the parallel interference canceller when the power values of the users are not uniform and different, but the interference cancellation signal processing for each user Since it is made in series, there is a disadvantage that the time required for the interference cancellation signal processing is increased by that much.

In addition, the parallel interference canceller can reduce the time required for interference cancellation compared to the serial interference canceller because the interference cancellation signal processing for each user is performed simultaneously, but the amount of interference cancellation signal processing to be processed per unit time is increased. There are more problems.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above. In order to remove interference signal components among multiple users of a TD-CD system, an interference cancellation process is performed in a short time. In addition, it can reduce the data throughput required for the interference elimination process, and provide a multi-user interference elimination receiver and interference elimination control method for the TD-CDMA system that can reduce errors even when the power difference of each user signal is large. There is.

1 is a block diagram applying a parallel interference canceller of the prior art,

2 is a block diagram showing the structure of an interference canceling unit in FIG. 1;

3 is a block diagram applying a series interference canceller of the prior art,

4 is a block diagram illustrating a structure of an interference canceling unit in FIG. 3;

5 is a block diagram of a multi-user interference cancellation receiver for a CD-CD system according to an embodiment of the present invention;

6 is a flowchart illustrating an operation of a multi-user interference cancellation receiver for a TMD-CD system according to an embodiment of the present invention.

The configuration of the present invention for achieving the above object,

In the multi-user interference cancellation receiver for TMD-CD system comprising two or more interference cancellation means,

An interference elimination screening means for extracting a midamble signal from the received original signals and selecting and outputting a primary interference elimination target user;

A first stage interference elimination means for receiving a data portion of the received original signal and performing parallel interference elimination on a primary interference elimination target user selected by the interference elimination selecting means and outputting a reproduction signal; And

And a second stage interference elimination means for receiving the data portion of the original signal received and outputting the second parallel interference elimination by using the first reproduction signal output from the first stage interference elimination means.

Another configuration of the present invention for achieving the above object,

In the multi-user interference cancellation receiver for TMD-CD system including two or more interference cancellation units,

Calculating power for each signal by reading channel estimation signals for each user;

Calculating an average value of power for each signal calculated in the step; And

And controlling only one-step interference cancellation of a signal of a user having a power equal to or greater than the average value of the power calculated in the above step.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

As shown in Figure 5, the configuration of a multi-user interference cancellation receiver for a TD-CD system according to an embodiment of the present invention

In the multi-user interference cancellation receiver for TMD-CD system comprising two or more interference cancellation means,

A data extraction unit 100 for extracting and outputting a data portion from a received signal;

A signal delay unit 200 for delaying and outputting a signal output from the data extraction unit 100 by a predetermined time;

An interference cancellation screening unit 300 for selecting and outputting a primary interference cancellation target user by extracting a midamble signal channel from the received original signals;

Receives the data portion of the received signal output from the data extraction unit 100 and performs parallel interference cancellation for the primary interference elimination target user selected by the interference elimination screening unit 300 and outputs a playback signal. And the first stage interference elimination block 400,

Receives the data portion of the received signal delayed by the predetermined time output from the signal delay unit 200 and secondly removes the parallel interference by using the first reproduction signal output from the first stage interference elimination block 400 It characterized in that it comprises a second stage interference elimination block 500.

The interference elimination selector 300 extracts and outputs a channel information signal from the received signals using the midamble signal, and outputs a midamble signal output from the channel estimator 300. It comprises a signal selection unit 320 for selecting the target user to receive the first input to the interference cancellation to output to the first stage interference cancellation block 400.

The first stage interference elimination block 400, the first interference elimination unit for receiving the data portion of the received signal to perform parallel interference elimination for the primary interference elimination target user screened by the interference elimination screening unit 300 And a first signal reproducing unit 420 which receives the signal output from the interference canceling unit 410 and reproduces and outputs the signal.

The second stage interference elimination block 500 receives a data portion of a received signal and outputs the second interference elimination unit 510 for performing parallel interference elimination for all users and the interference elimination unit 510. And a second signal reproducing unit 520 for receiving a signal and reproducing and outputting the signal.

Operation of the embodiment of the present invention made as described above is as follows.

The data extractor 100 receives the received signal, extracts only the signal of the data portion among the signals, and outputs the signals. Each delay unit 210, 220,... Of the signal delay unit 200 is the data extractor. Receives the signal output from the (100), and delays by the time required for signal processing in each interference cancellation block (400, 500, ...) and outputs.

The interference elimination selector 300 extracts a midamble signal from the received signals and selects a user to be subjected to primary interference elimination. The channel estimator 310 uses the midamble signal from the received signals to output the channel information signal. Extract and print

In addition, the signal selector 320 receives the channel estimation values output from the channel estimator 300 and selects a target user to be primarily subjected to interference cancellation and outputs the result to the first stage interference elimination block 400. The operation of the signal selector 320 is as shown in FIG. 6.

That is, the signal selector 320 receives a channel estimation signal for each user of the channel output from the channel estimator 310 (S10), and calculates power for each signal (S20).

Then, the average value of the total power for each user calculated in the step (S20) is calculated (S30).

Then, the power of each user-specific signals is compared with the average power (S40), and the first stage interference elimination block 400 is controlled to perform the interference elimination process for the user that is greater than the average power value (S50).

However, for the user's signal that is less than the average power value in step S40, the first stage interference elimination block 400 does not perform the interference elimination process, and thereby, the signal of the first stage interference elimination block 400. The amount of processing is reduced to half of the amount of interference signal processing of the second stage interference elimination block 500 or the third stage interference elimination block 600.

The first interference canceling unit 410 of the first stage interference elimination block 400 operates according to the signal output from the signal selecting unit 320 to generate a first signal among the data signals output from the first delay unit 210. Only the user's signal corresponding to 1-stage interference elimination performs parallel interference elimination.

In addition, the first signal reproducing unit 420 reproduces the interference canceled signal output from the first interference eliminating unit 410 as a signal capable of transmitting and outputs the signal to the second stage interference eliminating block 500.

The second stage interference elimination block 500 performs the interference elimination processing operation on the signals of all users as in the conventional art, and the method is the same as the operation of the conventional parallel interference elimination block.

By doing the above, since the amount of interference cancellation signal processing of the first stage interference elimination block can be reduced by half, the signal quality per unit time can be reduced to improve the signal quality.

In addition, by first performing interference cancellation processing on signals having a large value of signal power, signal processing errors due to a large power difference of signals for each user, which is a disadvantage of the parallel interference canceller, may also be reduced.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Accordingly, the present invention operating as described above can solve the problem of excessive amount of interference cancellation signal processing, which is a disadvantage of the parallel interference canceller.

In addition, the present invention has an effect of minimizing an error in detecting a user signal having a small value of signal power by first performing interference cancellation on signals having a large power value when a large difference in signal power of each user occurs. .

Claims (5)

In the multi-user interference cancellation receiver for TMD-CD system comprising two or more interference cancellation means, An interference elimination screening means for extracting a midamble signal from the received original signals and selecting and outputting a primary interference elimination target user; A first stage interference elimination means for receiving a data portion of the received original signal and performing parallel interference elimination on a primary interference elimination target user selected by the interference elimination selecting means and outputting a reproduction signal; And And a second stage interference elimination means for receiving the data portion of the original signal received and outputting the second parallel interference elimination by using the first reproduction signal output from the first stage interference elimination means. Multi-User Interference Cancellation Receiver for CD-CDMA Systems. The method of claim 1, wherein the interference elimination screening means, Channel estimating means for extracting channel information from the received original signals using a midamble signal and outputting the channel information; And And a signal selection means for selecting a target user to be subjected to interference cancellation primarily by receiving the channel information output from the channel estimation means and outputting the target user to the first stage interference elimination means. Multi-User Interference Cancellation Receiver for AM Systems. The method of claim 2, wherein the signal selection means, And a user for performing interference cancellation for a user whose magnitude of the midamble signal output from the channel estimating means is equal to or greater than an average value. The method of claim 1, wherein the first stage interference elimination means, Interference cancellation means for receiving a data portion of the received original signal and performing parallel interference cancellation for the primary interference elimination target user selected by the interference elimination screening means; And And a signal reproducing means for receiving a signal output from the interference eliminating means and reproducing the signal to output the signal. In the multi-user interference cancellation receiver for TMD-CD system comprising two or more interference cancellation unit, Calculating power for each signal by reading channel estimation signals for each user; Calculating an average value of power for each signal calculated in the step; And And controlling only the user's signal having a power equal to or greater than the average value of the power calculated in the step to perform one-stage interference cancellation.