KR100307703B1 - Simplifed paralel interference canceller and its implementation method for the mobile stations of handover region in reverse link synchronous transmission - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and method for parallel multi-stage interference cancellation for a mobile station in a handover region using a reverse synchronization scheme.

2. The technical gist of the invention to solve

According to the present invention, in detecting signals in which reverse synchronization with a target base station is synchronized using a multi-user reception method, interference of all received signals using only an interference signal reproduced only from a signal transmitted from a mobile station in a handover region The present invention aims to provide a parallel multi-stage interference canceling device and a method for a mobile station in a handover area that can simplify hardware configuration and thereby easily implement hardware.

3. Summary of the Solution of the Invention

The present invention includes a first step of extracting a decision variable by despreading a received signal; Reproducing only the signal in the handover region of the despread received signal according to whether the interference cancellation process is performed, and reproducing the interference signal in the handover region; Despreading the signal from which the interference has been removed to extract a new decision variable; And a fourth step of restoring the received signal according to whether all predetermined interference cancellation steps have been performed.

4. Important uses of the invention

The present invention is used in a communication system using a reverse synchronization technique.

Description

Sparlifed paralel interference canceller and its implementation method for the mobile stations of handover region in reverse link synchronous transmission

The present invention relates to a parallel multi-stage interference cancellation apparatus for a mobile station in a handover region using a reverse synchronization scheme and a method thereof. In particular, a signal in which backward synchronization is synchronized with a target base station using a multi-user reception scheme. The present invention relates to a parallel multi-stage interference canceling device and a method for canceling interference of an entire received signal by reproducing only interference of a signal transmitted from a mobile station in a handover area upon detection of these signals.

In general, in the forward direction of a code division multiple access (CDMA) system, orthogonality is established between channels, channel interference using orthogonal codes is reduced, but in the reverse direction, individual stations are random from a base station. Since the synchronization between the channels is not established, the interference through the orthogonal code cannot be reduced.

Therefore, the synchronization between channels is set in the reverse direction by adjusting the transmission time of the private station according to the time adjustment command bit transmitted by the base station.

Through this procedure, orthogonality between channels can be established in the reverse direction, thereby reducing interference between reverse channels.

In addition, an operation in which a specific mobile station is moved from a serving base station to a target base station is called a handover. When such a handover occurs, the mobile station occupies not only the serving base station but also one physical channel independent of the target base station.

If the mobile station currently establishes backward synchronization with the serving base station, the handover region still maintains backward synchronization with the serving base station, and thus backward synchronization with the target base station cannot be established.

FIG. 1 is a schematic diagram of backward synchronization associated with a handover area mobile station, and indicates that backward synchronization with a target base station is not established since the mobile station entering the handover area maintains backward synchronization with the serving base station.

In addition, from the perspective of the target base station, if the mobile stations located in the handover area among the mobile stations in the base station are about 30% of the total, 70% of the mobile stations have established reverse synchronization in the target base station. There will be about 30% of mobile stations that are out of sync.

In this way, the signals transmitted from the existing 30% of the mobile stations act as interference at the receiving end of the target base station, thereby degrading the performance of reverse synchronization.

Currently, the proposed broadband CDMA schemes can be largely classified into an inter-base station synchronous scheme and an inter-base station asynchronous scheme, both of which are affected by mobile stations in the handover region during backward synchronization.

That is, in the case of the asynchronous method between base stations, a maximum of 0.125 ms (= 512 chips) of network synchronization error occurs between base stations, which means that a signal transmitted from a mobile station in the handover region is up to 512 chips from the reverse synchronization time of the target base station. Since it means that it can be shifted, reverse synchronization cannot be established. Even in the case of the inter-base station synchronization method, a Global Positoning System (GPS) system is used, but since the error between the base stations is more than a few chips, the reverse synchronization is not established in the position of the target base station. Means no.

Therefore, mobile stations belonging to the handover region cannot establish reverse synchronization during reverse synchronization, and signals from the mobile stations in the handover region interfere with other mobile station signals in the target base station to which the reverse synchronization is matched. There was a problem that can not take full advantage of the advantages.

In addition, the reception principle of the CDMA system despreads the pseudo noise code of the signal to be detected at the receiver, so that other signals are suppressed and only its own signal is restored. Conventional Single User Detection ".

However, the single user reception technique is ideal when the orthogonality between signals is completely established. If the despreading is performed in a state where the orthogonality of each user signal is broken in a channel, the other user signal is added to the last detected signal. Will remain.

Accordingly, a method has been invented in which multiple user signals mixed in a channel do not interfere with each other, but rather can be used for optimal reception, which is referred to as "multiuser detection technique".

The multi-stage interference elimination method, which is one of the multi-user reception techniques, is a sub-optimal multi-user reception technique that can secure implementation and further improve performance by applying a single user reception technique in multiple stages.

The multi-stage interference cancellation method is classified into a serial interference cancellation scheme and a parallel interference cancellation scheme according to the type of interference cancellation.

FIG. 2 is a block diagram illustrating a conventional parallel multi-stage interference cancellation device, and is broadly divided into a receiver 100 and a multi-stage interference cancellation step 200 or 300.

The receiver 100 despreads the received signal using the pseudo noise codes PN1 to PN10 to output determinants Z1 to Z10 to be used for estimating a received power value of the user, and a pseudo noise code. And a respreader 140 for outputting interference signals S1 to S10 reproduced by respreading and reproducing the output signal of the despreader 110 using the PN1 to PN10.

The despreader 110 of the receiving end integrates the multipliers 111 to 120 and the output signals of the multipliers 111 to 120 for correspondingly multiplying the pseudo noise codes PN1 to PN10 and the received signal, respectively. For the integrators 121 to 130.

The respreading unit 140 of the receiving end includes multipliers 141 to 150 for correspondingly multiplying the pseudo noise codes PN1 to PN10 and the output signal of the despreading unit 110.

The first interference canceller 200 is an interference canceller 210 for canceling interference of a received signal transmitted through the delayer 101 by using the interference signals S1 to S10 reproduced by the receiver 100. And a despreader 260 which despreads the signal from which the interference is removed by the interference canceling unit 210 using pseudo noise codes PN1 to PN10 and outputs new decision variables / Z1 to / Z10. Re-spread the signal despread by the despreader 260 using the pseudo noise codes PN1 to PN10 and output the interference signals / S1 to / S10 to be used for the interference cancellation of the next interference cancellation stage. The diffusion part 270 is provided.

The interference canceller 210 of the first interference canceller 200 is an addition value obtained by adding all the interference signals S2 to S10 output from the receiver 100 to the received signal transmitted through the delayer 101. A subtractor 211 for subtracting A1, and A2, which is an addition value obtained by adding all the interference signals S1 and S3 to S10 output from the receiving terminal 100, from the received signal transmitted through the delayer 101. A subtractor 213 and a subtractor 213 for subtracting A3, which is an addition value obtained by adding all the interference signals S1, S2, and S4 to S10 from the received signal transmitted through the delayer 101, and a delayer ( A subtractor 214 for subtracting A4, which is an addition value obtained by adding all the interference signals S1, S2, S3, and S5 to S10 from the received signal transmitted through 101, and the received signal transmitted through the delay unit 101. A subtraction for subtracting A5 which is an addition value obtained by adding all of the interference signals S1 to S4 and S6 to S10 from the signal. A subtractor 216 and a subtractor 216 for subtracting A6, which is an addition value obtained by adding all the interference signals S1 to S5 and S7 to S10 from the received signal transmitted through the delayer 101, In the received signal transmitted through the delayer 101 and the subtractor 217 for subtracting A7, which is an addition value obtained by adding all the interference signals S1 to S6 and S8 to S10 from the received signal transmitted through 101). A subtractor 218 for subtracting A8 which is an addition value obtained by adding all the interference signals S1 to S7 and S9 and S10, and the interference signals S1 to S8 and S10 in the received signal transmitted through the delay unit 101; A subtractor 219 for subtracting A9, which is the sum of all of them, and a subtractor for subtracting A10, the sum of all of the interference signals S1 to S9, from the received signal transmitted through the delayer 101; 220.

The despreader 260 of the first interference canceller 200 may correspondingly multiply pseudo noise codes PN1 through PN10 and output signals of the subtractors 211 through 220 of the interference canceller 210. Multipliers 221 to 230 and integrators 231 to 240 for integrating output signals of the multipliers 221 to 230, respectively.

The respreader 270 of the first interference canceling stage 200 may multiply the pseudonoise codes PN1 to PN10 and the output signals of the despreader 260 correspondingly. Is done.

The second interference cancellation stage 300 may remove the interference of the received signal transmitted through the delayer 201 using the interference signals / S1 to / S10 reproduced by the first interference cancellation stage 200. Outputs new decision variables (// Z1 to // Z10) by despreading the signal from which the interference has been removed by the interference canceling unit 310 and the pseudo noise codes PN1 to PN10. The despreader 360 and the pseudo noise codes PN1 to PN10 may be used to remove the interference of the next interference canceling stage by respreading the signal despread by the despreader 360. And a respreading unit 370 that outputs / S1 to // S10.

The interference canceling unit 310 of the second interference elimination stage 300 receives / S2 to / S10 which are interference signals output from the first interference elimination stage 200 in the received signal transmitted through the delay unit 201. A subtractor 311 for subtracting the added value / A1, and / S1 and / S3 which are the interference signals outputted from the first interference cancellation terminal 200 in the received signal transmitted through the delayer 201. A subtractor 312 for subtracting / A2, which is an addition value of / S10, and all of the interference signals / S1, / S2 and / S4 to / S10 in the received signal transmitted through the delayer 201. A subtractor 313 for subtracting the added value / A3 and the interference signals / S1, / S2, / S3 and / S5 to / S10 are added to the received signal transmitted through the delayer 201. A subtractor 314 for subtracting an addition value / A4, and all the interference signals / S1 to / S4 and / S6 to / S10 from the received signal transmitted through the delayer 201 are added. A subtractor 315 for subtracting one addition value / A5, and an addition value obtained by adding all of the interference signals / S1 to / S5 and / S7 to / S10 in the received signal transmitted through the delayer 201 A subtractor 316 for subtracting / A6, and / A7 which is an addition value obtained by adding all the interference signals / S1 to / S6 and / S8 to / S10 from the received signal transmitted through the delayer 201 A subtractor 317 for subtracting / A8 which is the sum of all the interference signals / S1 to / S7 and / S9 and / S10 from the received signal transmitted through the delayer 201 ( 318 and a subtractor 319 for subtracting / A9, which is an addition value obtained by adding all of the interference signals / S1 to / S8 and / S10 from the received signal transmitted through the delayer 201, and a delayer ( And a subtractor 320 for subtracting the added value / A10 obtained by adding all the interference signals / S1 to / S9 from the received signal transmitted through 201).

The despreader 360 of the second interference cancellation stage 300 is configured to correspondingly multiply the output signals of the pseudo noise codes PN1 to PN10 and the subtractors 311 to 320 of the interference cancellation unit 310. Multipliers 321 to 330 and integrators 331 to 340 for integrating output signals of the multipliers 321 to 330, respectively.

The respreader 370 of the second interference cancellation stage includes multipliers 341 to 350 for correspondingly multiplying the pseudo noise codes PN1 to PN10 and the output signals of the despreader 360.

Referring to the operation of the conventional parallel multi-stage interference cancellation device having the structure as described above is as follows.

The decision variables Z1 to Z10 obtained from the output of the despreader 110 of the receiver 100 for the existing single user are received power values of each user, and the respreader 140 corresponds to the received power value. The noise signals PN1 to PN10 are used to respread the output signal of the despreader 110 to reproduce the interference signals S1 to S10.

As such, since the reproduced signals S1 to S10 are signals acting as interference to other signals, the interference canceling unit 210 of the first interference canceling stage 200 receives the multiple access signals except for the signal to be detected from the received signal. At the same time, the signal is removed from the receiver 100 for the existing single user by despreading the output signal of the interference canceling unit 210 using the pseudo noise codes PN1 to PN10 again. It is possible to obtain new decision variables (/ Z1 to / Z10) in which the interference component is further reduced compared to the obtained decision variables (Z1 to Z10).

Subsequently, the respreading unit 270 of the first interference elimination stage 200 re-spreads the output signal of the despreading unit 260 using the corresponding pseudo noise codes PN1 to PN10 to interfere with the interference signals / S1 to /. S10) to play.

In this way, the interference signals / S1 to / S10 reproduced by the first interference elimination stage 200 are used by the second interference elimination stage 300 to remove the interference of the received signal.

As such, the interference cancellation process is simultaneously performed on the received signals from all users.

Here, up to the step of obtaining new decision variables / Z1 to / Z10 by the despreader 260 of the first interference elimination stage 200 is the first stage of the parallel multi-stage interference elimination process, and the first interference elimination stage From the step of obtaining the interference signals / S1 to / S10 by the re-spreading unit 270 of (200), the new decision variable (// Z1 to -1) by the despreading unit 360 of the second interference elimination stage 300; // Z10) is a second step of the parallel multi-stage interference cancellation process.

This multi-stage interference cancellation process can be repeated repeatedly until the desired signal quality is achieved.

In addition, each interference elimination stage of the parallel multi-stage interference elimination apparatus simultaneously estimates the received power value of each user by using a decision variable output from a receiver for an existing single user for each user.

Here, the decision variable is a value obtained by the output of the existing single user receiving end, and in the conventional reception method, the final detection signal is obtained by hard decision or soft decision of this decision variable.

Since the determinants are despread without orthogonality, interferences from other signals as well as their own signals are included. The interference cancellation process is shown in FIG. 3. As it is.

3 is a flowchart illustrating a conventional parallel multi-stage interference cancellation method.

As shown in Fig. 3, a signal transmitted from a mobile station is received (301), the received signals are despread (302), and a decision variable is extracted (303).

Subsequently, it is determined whether the interference elimination process is performed (304). If the interference elimination process is performed, the despread signal is re-spread to reproduce the interference signals (305), and the interference signal of the received signal is removed using the reproduced interference signal. (306).

In this way, by despreading the signal from which the interference is removed (307), after extracting a new decision variable (308), it is determined whether or not the interference cancellation process has been performed until the predetermined interference cancellation step (K) (309). Here, the interference elimination step K is set by the user.

If the interference cancellation is performed until the predetermined interference cancellation step K in the interference cancellation determination process 309, the received signal is restored to the original signal (310).

If the interference elimination is not performed until the predetermined interference elimination step K in the determination process 309, whether the interference elimination has been completed, the process proceeds to the process of reproducing the interference signal 305, and the predetermined interference elimination step ( Until K), the interference of the received signal is continuously removed until the interference cancellation process is performed.

Meanwhile, if the interference elimination process is completed in the process of determining whether the interference elimination process is 304, the process 310 of restoring the received signal is immediately performed.

However, in the case of the conventional parallel multi-stage interference cancellation apparatus as described above, there is a problem that the configuration of the hardware is very complicated by detecting all the interference signals for all received signals.

The present invention has been proposed to solve the above problems, and in detecting signals having reverse synchronization with a target base station using a multi-user reception method, only a signal transmitted from a mobile station in a handover area is detected. Provided are a parallel multi-stage interference canceling device and a method for a mobile station in a handover area, which can simplify hardware configuration and thereby easily implement hardware by removing interference of all received signals using only reproduced interference signals. Its purpose is to.

1 is a schematic diagram of reverse synchronization associated with a handover area mobile station;

Figure 2 is a block diagram of a conventional parallel multi-stage interference cancellation device.

3 is a flow chart of a conventional parallel multi-stage interference cancellation method.

4 is a block diagram of an embodiment of a parallel multi-stage interference cancellation apparatus for a mobile station in a handover region using a reverse synchronization scheme according to the present invention.

5 is a flow diagram of an embodiment of a parallel multi-stage interference cancellation method for a mobile station in a handover region using a reverse synchronization scheme according to the present invention.

Explanation of symbols on the main parts of the drawings

100, 400: receiver

200, 500: first interference cancellation stage

300, 600: second interference cancellation stage

110, 260, 360, 410, 560, 660: despreader

140, 270, 370, 440, 570, 670: respread section

210, 310, 510, 610: interference cancellation unit

The present invention for achieving the above object comprises a receiving processing means for despreading and then respreading a received signal, and a plurality of interference canceling means connected in parallel to remove the interference of the received signal at each step; 13. A parallel multi-stage interference cancellation apparatus, said reception processing means comprising: first despreading means for despreading said received signal using a plurality of preset pseudo noise signals; And a first respreading signal outputting an interference signal by respreading only a signal in a handover area among the output signals of the first despreading means using only pseudo noise signals in a handover area among the plurality of pseudo noise signals. Means for removing the interference of the received signal by using an interference signal in the handover region immediately outputted; Second despreading means for despreading a signal from which interference is removed by the interference canceling unit by using the plurality of pseudo noise signals; And second respreading means for respreading a signal despread by the second despreading means and outputting an interference signal in the handover area by using only the pseudo noise signals in the handover area. The interference signal in the handover region output from the first respreading means is used in the interference canceling unit of the first interference eliminating means from the reception processing means, and the interference signal in the handover region output from the second respreading means is immediately Next, the interference canceling unit of the interference canceling unit connected in parallel may be used.

The present invention also provides a parallel multi-stage interference cancellation method for removing interference of a received signal, comprising: a first step of despreading the received signal to extract a decision variable; Reproducing only the signal in the handover region of the despread received signal according to whether the interference cancellation process is performed, and reproducing the interference signal in the handover region; A third step of extracting a new decision variable by despreading the signal from which the interference is removed after removing the interference of the received signal by using the interference signal in the handover region reproduced in the second step; And a fourth step of restoring the received signal to the original signal according to whether all of the predetermined interference cancellation steps have been performed.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4 and 5.

4 is a diagram illustrating an embodiment of a parallel multi-stage interference cancellation apparatus for a mobile station in a handover region using a reverse synchronization scheme according to the present invention.

As shown in FIG. 4, the apparatus for parallel multi-stage interference cancellation for a mobile station in the handover area according to the present invention, as described above with reference to FIG. 2, includes a receiver 400 and a multi-stage interference cancellation stage 500 and 600. It is largely divided into).

The structure and function of the parallel multi-stage interference cancellation device of the present invention are almost similar to the conventional parallel multi-stage interference cancellation device shown in FIG.

However, in the conventional parallel multi-stage interference cancellation apparatus, all received signals are re-spread to reproduce the interference signals for all received signals. However, in the parallel multi-stage interference cancellation apparatus of the present invention, the received signals are received from a mobile station in the handover region. Only the transmitted signal is re-spread to reproduce only the interference signal in the handover area. Here, the signal for the mobile station is about 30% of the total received signals.

Looking at the structure of the parallel multi-stage interference cancellation device of the present invention having such features as follows.

The receiver 400 uses a despreader 410 having the same structure and function as the receiver of FIG. 2 and a hand among the output signals of the despreader 410 using pseudo noise codes PN8 to PN10 for the mobile station. And a respreading unit 440 for outputting the interference signals S8 to S10 reproduced by respreading only the signal transmitted from the mobile station in the over area.

The despreader 410 of the receiver 400 multiplies the multipliers 411 to 420 and the output signals of the multipliers 411 to 420 to correspondingly multiply the received noise signals with the pseudo noise codes PN1 to PN10. Integrators 421 to 430 for integrating, respectively.

The respreader 440 of the receiving end multiplier for multiplying only the signals in the handover region among the pseudonoise codes PN8 to PN10 for the mobile stations in the handover region and the output signals of the despreader 410. 448 to 450).

The first interference canceling unit 500 uses the interference signals S8 to S10 reproduced by the receiving unit 400 to remove the interference of the received signal transmitted through the delay unit 401. And a despreader 560 which despreads the signal from which the interference is removed by the interference canceling unit 510 using pseudo noise codes PN1 to PN10 and outputs new decision variables / Z1 to / Z10. Re-spread the signal despread by the despreader 560 using the pseudo noise codes PN1 to PN10 to output the interference signals / S8 to / S10 to be used for the interference cancellation of the next interference cancellation stage. The diffusion part 570 is provided.

The interference canceller 510 of the first interference canceller 500 may be an addition value obtained by adding all the interference signals S8 to S10 output from the receiver 400 from the received signal transmitted through the delay unit 401. A subtractor 511 for subtracting B1 and a subtractor for subtracting B2, which is an addition value obtained by adding all the interference signals S8 to S10 output from the receiver 400 from the received signal transmitted through the delay unit 401 ( 512 and a subtractor 513 for subtracting B3, which is an addition value obtained by adding all the interference signals S8 to S10, from the received signal transmitted through the delay unit 401, and transmitted through the delay unit 401. A subtractor 514 for subtracting B4, which is an addition value that adds all of the interference signals S8 to S10 from the received signal, and all the interference signals S8 to S10 are added to the received signal transmitted through the delay unit 401. The subtractor 515 is used to subtract one additional value B5, and the delay is passed through the delayer 401. A subtractor 516 for subtracting B6, which is an addition value, by adding all the interference signals S8 to S10 from the received signal, and all of the interference signals S8 to S10 in the received signal transmitted through the delayer 401. A subtractor 517 for subtracting the added value B7 and a subtractor 518 for subtracting the added value B8 obtained by adding the interference signals S9 and S10 to the received signal transmitted through the delayer 401. And a subtractor 519 for subtracting B9, which is an addition value of the interference signals S8 and S10, from the received signal transmitted through the delay unit 401, and the received signal transmitted through the delay unit 401. And a subtractor 520 for subtracting B10, which is an addition value obtained by adding the interference signals S8 and S9.

The despreader 560 of the first interference canceller 500 may correspondingly multiply the pseudo-noise codes PN1 to PN10 and the output signals of the subtractors 511 to 520 of the interference canceller 510. Multipliers 521 to 530 and integrators 531 to 540 for integrating output signals of the multipliers 521 to 530, respectively.

The respreader 570 of the first interference canceling stage 500 transmits a signal transmitted from the mobile station in the handover region among the pseudo noise codes PN8 to PN10 and the output signals of the despreader 560 for the mobile station. Multipliers 548 to 550 for correspondingly multiplying the bay.

The second interference cancellation stage 600 may use the interference signals / S8 to / S10 reproduced by the first interference cancellation stage 500 to remove the interference of the received signal transmitted through the delay unit 501. Despread the signal from which the interference is removed by the interference canceling unit 610 using the interference canceling unit 610 and pseudo noise codes PN1 to PN10 to output new decision variables (// Z1 to // Z10). Despreader 660 and pseudo noise codes PN1 to PN10 are used to despread only the signals transmitted from the mobile stations in the handover region among the signals despread by the despreader 660 to immediately remove the next interference. And a respreading unit 670 for outputting interference signals (// S8 to // S10) to be used for interference cancellation.

The interference canceling unit 610 of the second interference elimination stage 600 receives / S8 to / S10 which are interference signals output from the first interference elimination stage 500 in the received signal transmitted through the delay unit 501. A subtractor 611 for subtracting the added value / B1, and / S8 to / S10 which are the interference signals outputted from the first interference canceller 500 from the received signal transmitted through the delayer 501 A subtractor 612 for subtracting / B2, which is an added value, and / B3, which is the sum of all the interference signals / S8 to / S10, is subtracted from the received signal transmitted through the delayer 501. A subtractor 614 for subtracting / B4, which is an addition value obtained by adding all the interference signals / S8 to / S10, from the received signal transmitted through the delayer 501, and a delayer A subtractor for subtracting / B5, which is an addition value obtained by adding all the interference signals / S8 to / S10, from the received signal transmitted through 501 615 and a subtractor 616 for subtracting / B6, which is an addition value obtained by adding all of the interference signals / S8 to / S10, from the received signal transmitted through the delayer 501, and the delayer 501. A subtractor 617 for subtracting / B7 which is the sum of all the interference signals / S8 to / S10 from the received signal transmitted through the signal, and the interference signal in the received signal transmitted through the delay unit 501. A subtractor 618 for subtracting / B8, which is an addition value of / S9 and / S10, and an added value obtained by adding the interference signals / S8 and / S10 to the received signal transmitted through the delay unit 501; A subtractor 619 for subtracting phosphorus / B9 and a subtractor 620 for subtracting / B10 which is an addition value of the interference signals / S8 and / S9 from the received signal transmitted through the delay unit 501. It is provided.

The despreader 660 of the second interference canceling stage 600 is configured to correspondingly multiply the output signals of the pseudo noise codes PN1 to PN10 and the subtractors 611 to 620 of the interference canceller 610. Multipliers 621 through 630 and integrators 631 through 640 for integrating output signals of the multipliers 621 through 630, respectively.

The respreader 670 of the second interference cancellation stage 600 is a signal in the handover region among the pseudo noise codes PN8 to PN10 and the output signals of the despreader 660 for the mobile station in the handover region. Multipliers 648-650 for correspondingly multiplying the bay.

Referring to the operation of the multi-stage interference cancellation device of the present invention having the structure as described above in detail.

It is assumed that 30% of all received signals received by the target base station are transmitted from mobile stations existing in the handover region, and the total number of transmitted signals of the received mobile stations is 10, and the receiving end of the 10 signals is received. It is assumed that the three signals input to the multipliers 418 to 420 of the despreader 410 of 400 are signals transmitted from mobile stations in the handover area.

In case of the conventional reception method that does not use the parallel multi-stage interference cancellation device of the present invention, the hard decision of the decision variables Z1 to Z10 obtained from the despreader 410 of the receiver 40 is performed. To detect the output signal.

When the parallel multi-stage interference cancellation apparatus of the present invention is applied, the interference cancellation step by the first interference cancellation stage 500 is performed.

Here, the first interference cancellation stage 500 removes the interference of the received signal using only the interference signals S8 to S10 belonging to the handover region reproduced by the receiver 400. At this time, the interference signals S8 to S10 are interference signals belonging to the handover region, which is re-spread by the re-spreading unit 440 of the receiving end 400 using the pseudo noise signals PN8 to PN10.

The interference cancellation process performed by the interference cancellation unit 510 of the first interference cancellation stage 500 may be divided into interference cancellation by the subtractors 511 to 517 and interference cancellation by the subtractors 518 to 520. In the case of interference cancellation by the subtractors 511 to 517, in the detection of 70% of the mobile station signals having backward synchronization with the target base station, the interference from the signals in the handover region is eliminated. In the case of interference cancellation by 518 to 520, the interference of signals in the handover region is eliminated.

Here, the process of detecting the 70% signal after the backward synchronization has been removed by interference, the first stage interference performed by the first interference cancellation stage 500 for each 70% of the signal interference removal unit 510 The despreading unit 560 despreads it again using its pseudo noise signal, and outputs the decision variables / Z1 to / Z10 after the first stage interference elimination.

In this way, hard decision of the decision variables (/ Z1 to / Z10) obtained by the despreading unit 560 of the first interference cancellation stage 500 restores the desired data, and the restored data at this time performs parallel interference cancellation. The data after the first run. This process is repeated as many times as the desired interference cancellation step. As the level of interference cancellation increases, the values of the decision variables become more accurate, and they are again removed from the overall received signal, resulting in better detection performance.

In addition, as the interference cancellation proceeds in multiple stages, the interference cancellation scheme proposed by the present invention has an advantage over the conventional parallel interference cancellation scheme for removing interference of all received signals in terms of hardware implementation complexity.

Here, the interference can be removed from the entire received signal by selecting only the mobile station signals in the handover area because the target base station already has information on the mobile stations in the handover area.

That is, when a specific mobile station enters the handover area, the mobile station requests a new physical channel allocation to the target base station for handover, and the target base station newly allocates a physical channel for handover with the mobile station according to this request.

The base station controller manages all these processes, and information about the channel for handover is stored in the base station controller, and the target base station can refer to the information on the handover channel from the base station controller.

In the same manner as described above, the interference signals in the handover area are removed from the entire received signal, and 70% of the normal mobile station signals having backward synchronization with the target base station are not affected by the interference from the handover area mobile station signals of the target base station. Detection is possible.

In the above, the procedure for detecting 70% of the mobile station signals having backward synchronization with the target base station is described. Hereinafter, detection of about 30% of the mobile station signals belonging to the handover area among the target base stations will be described.

Factors affecting the detection of signals belonging to the handover area include interference from 70% of the mobile stations that do not exist in the handover area, and the remaining 30% of the mobile stations within the handover area except for their own signals. There is also interference from the signals.

Conventional parallel interference cancellation eliminates both interferences when detecting signals in the handover region. However, this introduces hardware complexity and is complicated to implement.

Therefore, in the present invention, as shown in FIG. 4, the interference from 70% of the signals that are in reverse synchronization is not removed when detecting the handover region signals, and only the interference between the signals belonging to the handover region is removed. have. The signals of the handover region are removed by the interference canceling unit 510 of the first interference canceling stage 500, and at this time, only the interference signals S8 to S10 reproduced by the receiving terminal 400 are used. It does not cause additional hardware complexity for spreading.

In the present invention, as in the case of detecting signals of mobile stations belonging to the handover region through the first interference cancellation stage 500, the parallel interference cancellation method can be applied using only interference signals in the handover region. This is because a good reception signal detected from a synchronous serving base station can be used as signals in a handover area.

That is, since the signals of the mobile stations existing in the handover area are simultaneously detected by the serving base station and the target base station, it is possible to optimally receive the signals in the handover area by utilizing the diversity advantage.

5 is a flowchart illustrating an embodiment of a parallel multi-stage interference cancellation method for a mobile station in a handover region using a reverse synchronization scheme according to the present invention.

Referring to FIG. 5, a signal transmitted from a mobile station is received (501), the received signals are despread (502), and a decision variable is extracted (503).

Subsequently, it is determined whether the interference cancellation process is performed (504). If the interference cancellation process is performed, only the signal transmitted from the mobile station in the handover region is re-spread among the despread received signals to reproduce the interference signal in the handover region (505). The interference signals of all received signals are removed using the interference signals in one handover region (506).

In this manner, by despreading the signal from which the interference is removed (507), after extracting a new decision variable (508), it is determined whether or not the interference cancellation process has been performed until the predetermined interference cancellation step (K) (509). Here, the interference elimination step K is set by the user.

If the interference cancellation is performed until the interference elimination step K is set in the interference elimination determination process 509, the received signal is restored to the original signal (510).

If the interference elimination is not performed until the predetermined interference elimination step K in the determination process 509, whether the interference elimination has been completed, the process proceeds to the process of reproducing the interference signal 505, and the predetermined interference elimination step ( Until K), the interference of the received signal is continuously removed until the interference cancellation process is performed.

On the other hand, if the interference cancellation process is completed in step 504 of determining whether the interference cancellation process is completed, a process 510 of restoring the received signal is immediately performed.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

The present invention as described above, by applying the interference cancellation apparatus to the target base station to remove the interference of the entire received signal using the interference signal of the mobile stations belonging to the handover area, the mobile station that the remaining reverse synchronization in the target base station is matched There is an effect that the signals from are not affected, and in particular, can maximize the reverse link system capacity.

Claims (6)

In the parallel multi-stage interference elimination apparatus having a receiving processing means for despreading and respreading a received signal again, and a plurality of interference canceling means connected in parallel to remove the interference of the received signal at each stage, The reception processing means, First despreading means for despreading the received signal using a plurality of preset pseudo noise signals; And A first respreading means for re-spreading only the signals in the handover region among the output signals of the first despreading means and outputting an interference signal using only the pseudonoise signals in the handover region among the plurality of pseudonoise signals; And The plurality of interference cancellation means, respectively An interference canceling unit for canceling interference of the received signal by using an interference signal in a handover region immediately output; Second despreading means for despreading a signal from which interference is removed by the interference canceling unit by using the plurality of pseudo noise signals; And A second respreading means for respreading a signal despread by the second despreading means and outputting an interference signal in the handover area by using only pseudo noise signals in the handover area, The interference signal in the handover area output from the first respreading means is used in the interference canceling portion of the first interference eliminating means from the receiving processing means, The interference signal in the handover region output from the second respreading means is immediately used in the interference canceling unit of the interference canceling means connected in parallel next to the parallel multi-stage for the mobile station in the handover region using the reverse synchronization technique. Interference Cancellation Device. The method of claim 1, The second respreading means, A plurality of multiplication means for correspondingly multiplying the signals in the handover region among the pseudonoise signals in the handover region and signals despread by the second despreading means; Parallel multistage interference cancellation apparatus for a mobile station in the handover region using a reverse synchronization scheme comprising a. In the parallel multi-stage interference cancellation method for removing interference of the received signal, Extracting a decision variable by despreading the received signal; Reproducing only the signal in the handover region of the despread received signal according to whether the interference cancellation process is performed, and reproducing the interference signal in the handover region; A third step of extracting a new decision variable by despreading the signal from which the interference is removed after removing the interference of the received signal by using the interference signal in the handover region reproduced in the second step; And A fourth step of restoring the received signal to the original signal according to whether all predetermined interference cancellation steps have been performed; A parallel multi-stage interference cancellation method for a mobile station in a handover region using a reverse synchronization scheme, including. The method of claim 3, wherein The second step, A fifth step of determining whether the interference cancellation process is performed; A sixth step of reproducing only the signal in the handover region of the despread received signals and reproducing the interference signal in the handover region if the determination result in the fifth step is performed; And If the result of the determination in the fifth step is not the interference cancellation process, the seventh step is passed to the fourth step. A parallel multi-stage interference cancellation method for a mobile station in a handover region using a reverse synchronization scheme, including. The method of claim 3, wherein The third step, A fifth step of eliminating interference of the received signal by using the interference signal in the reproduced handover region; And A sixth step of extracting a new decision variable by despreading the signal from which the interference is removed in the fifth step A parallel multi-stage interference cancellation method for a mobile station in a handover region using a reverse synchronization scheme, including. The method according to any one of claims 3 to 5, The fourth step, An eighth step of determining whether all of the predetermined interference cancellation steps have been performed; A ninth step of restoring the received signal to an original signal when all of the predetermined interference cancellation step has been performed as a result of the determination in the eighth step; And A tenth step that goes to the third step if the predetermined interference cancellation step is not performed as a result of the determination in the eighth step; A parallel multi-stage interference cancellation method for a mobile station in a handover region using a reverse synchronization scheme, including.