CN1184766C - Integration receiver used for code division multiple access (CDMA) communication system - Google Patents

Abstract

The present invention discloses integration receiver used for code division multiple access (CDMA) communication systems, which comprises a matched filter set, multi-stage interference cancellation sets and a multi-path searcher set. In the present invention, after the multi-path searcher set is arranged on a plurality of multi-stage interference cancellation sets, multi-path searching is carried out in a signal without multi-address interference. Obtained time delay information is accurate. The accurate time delay information can effectively improve the performance of a de-spread and interference cancellation module. The performance improvement of de-spread and interference cancellation reacts on the multi-path searching, so the precision of the multi-path searching is high to achieve the effect of positive feedback. The present invention can effectively improve the performance of the multi-path searching and the de-spread and interference cancellation, so the performance of the whole receiver is improved.

Description

A kind of joint receiver that is used for code division multiple address communication system

Technical field

The present invention relates to the mobile communication system interference mitigation technology, more specifically refer to a kind of joint receiver that is used for code division multiple address communication system.

Background technology

Along with the development of mobile communication, DS-CDMA (direct sequence spread spectrum one code division multiple access) has obtained to use widely.In the DS-CDMA system, Rake (RAKE) receiver is a kind of general receiver.By doing the relevant of slice-level to received signal, can the despreading received signal.Usually despread values also will multiply by the estimated value of channel fading, and to remove the phase of received signal rotation that channel fading causes, the output that obtains this moment is being declared firmly or softly declared the back and sent to decoding usually.

Yet in typical multi-user environment, the application of Rake receiver is subjected to certain restriction and exists, and this is because CDMA is an interference limiting system, exist between each subscriber signal multiple access disturb (MultipleAccess Interference, MAI).Along with the increase of number of users, multiple access disturbs the main interference that just becomes cdma communication system, has seriously influenced systematic function.In order to eliminate the multiple access interference effect, people have proposed to utilize other users' Given information to remove to eliminate the multiuser detection that multiple access disturbs on the basis of Rake receiver.Multistage parallel interference cancellation (MPIC) receives the concern of engineering circle for a long time as a kind of superior performance and the higher multi-user test method of realizability always.The multiple access that parallel interference cancellation can effectively suppress in the cdma system disturbs, and improves power system capacity, improves system communication quality, and improve coverage, reduces advantages such as power control requirement.

Do not comprise interference cancellation in traditional Rake receiver structure, a plurality of channel independent process, and the receiver that has an interference cancellation structure need utilize the information of a plurality of channels to carry out Combined Treatment.Usually we call traditional receiver to the former, and the latter is called joint receiver.

The block diagram of a typical joint receiver as shown in Figure 1.It mainly comprises two parts: matched filter banks 100 and multistage interference cancellation module 104, wherein matched filter banks 100 has comprised a plurality of independently modules 105, each module 105 is matched filters, and each matched filter mainly comprises three modules 101,102,103.The 101st, the Multipath searching module, its main effect is the multipath information that searches out each user, comprises the number and the delayed data of multipath.The multipath direct information despreading module 102 that Multipath searching module 101 extracts is carried out despreading.The main effect of despreading module 102 is that to utilize known scrambling code information and delayed data to do to received signal relevant, and modulation intelligence is extracted from spread-spectrum signal.103 modules are that channel estimating and Rake merge module, and its main effect is a decline value of estimating complex channel, and phase place rotation and the changes in amplitude of utilizing this estimated value compensating signal to suffer through channel.When multipath existed, module 103 was also carried out the operation that Rake merges, and promptly the signal in each footpath was superposeed to improve signal to noise ratio by certain criterion.Multistage interference cancellation module 104 includes a plurality of interference cancellations unit 106, and the effect of multistage interference cancellation module 104 is phase mutual interference of eliminating between the user.Common interference cancellation structure has: parallel interference cancellation (PIC); Successive interference cancellation (SIC); Mix interference cancellation (GSIC); Wherein parallel interference cancellation (PIC) is most widely used.

Fig. 2 is typical parallel interference cancellation (PIC) internal frame diagram.Its operation principle is as follows: at first utilize the symbol judgement of each channel of matched filter banks 100 outputs to disturb regeneration, after the interference regeneration that obtains each user, can carry out interference eliminated, thereby obtain the spread-spectrum signal of elimination from each user of other users' interference.This signal is carried out despreading and Rake merging, can be adjudicated more accurately.

Though the interference cancellation module in the existing joint receiver can suppress multi-user interference, make the detection performance better.But because below, existing joint receiver structure also is subjected to bigger restriction.

The first, the Multipath searching module as the interference cancellation front end is to carry out in the environment that is full of the multiple access interference, affects to the multiple access serious interference performance of the Multipath searching of system, thus the signal to noise ratio of signal after the reduction despreading.

The second, the signal to noise ratio of signal reduces the reduction of the efficient directly caused interference cancellation after the despreading.

Three, because interference cancellation needs accurate multipath delay information, so the reduction of Multipath searching performance has further influenced the efficient of interference cancellation.

Four, interference cancellation reduces the system works signal to noise ratio, and whole system just can be held more user, but this causes the Multipath searching process to be forced to be operated in more multiple access interference down again, and performance further descends, and becomes the performance bottleneck of whole band receiver of base.

Summary of the invention

The above-mentioned multiple access that exists at traditional joint receiver disturbs too much gives influence that the Multipath searching performance brings and Multipath searching precise decreasing to rear end interference cancellation efficient shortcoming, the purpose of this invention is to provide a kind of joint receiver that is used for code division multiple address communication system.

To achieve these goals, the present invention adopts following technical scheme: this joint receiver comprises matched filter banks, multistage interference cancellation group and multipath group, matched filter group of received multiple user signals, the pre-judgement of output signal is to multistage interference cancellation group, multistage interference cancellation group output decision signal and interference cancellation signals, wherein, interference cancellation signals inputs to the Multipath searching group, and the Search Results of Multipath searching group feeds back to matched filter banks and many group interference cancellation groups more respectively.

Described matched filter banks comprises a plurality of independently matched filter module, contains despreading module and channel estimating and Rake in each matched filter module again and merges module;

Described multistage interference cancellation group comprises a plurality of interference cancellations unit;

Described multipath group comprises a plurality of Multipath searching modules;

The despreading module of each matched filter module in the described matched filter banks utilizes known scrambling code information to do relevant with delayed data to multi-user's received signal, modulation intelligence extracted from spread-spectrum signal deliver to channel estimating and Rake and merge module, channel estimating and Rake merge the decline value that module is estimated complex channel, and the phase place rotation and the changes in amplitude that take place when utilizing this estimated value compensating signal through channel, carry out the first order interference cancellation unit of delivering to after the Rake merging superposes in the multistage interference cancellation group, afterbody interference cancellation unit is eliminating to export after multiple access disturbs to organize signals more, each group signal comprises decision signal and interference cancellation signals, wherein interference cancellation signals inputs to each multipath in the multipath group more respectively, each multipath extracts multipath delay information, and the result is fed back to each grade interference cancellation unit in the despreading module of each corresponding matched filter in the matched filter banks and the multistage interference cancellation group respectively.

In above-mentioned joint receiver of the present invention, the multipath group is placed after many group interference cancellation groups, make Multipath searching in having eliminated the multiple access interference signals, carry out, resulting delayed data will be more accurate, and delayed data can improve the performance of despreading and interference cancellation module effectively more accurately.And the raising of despreading and interference cancellation performance reacts on Multipath searching, makes the Multipath searching precision higher, thereby reaches a kind of effect of positive feedback.The present invention improves the performance of Multipath searching and despreading and interference cancellation effectively, thereby improves the performance of whole receiver.

Description of drawings

Fig. 1 is a receiver square frame principle schematic diagram behind the traditional connection.

Fig. 2 is the interference cancellation unit square frame principle schematic diagram in traditional joint receiver.

Fig. 3 joins back receiver square frame principle schematic diagram for the present invention.

Embodiment

In joint receiver, for despreading and the interference cancellation that carries out the CDMA signal, receiver need obtain the multipath delay information of signal, the number and the position that comprise multipath, there is document to show, multipath delay information is very big to the effectiveness affects of interference cancellation, when error surpasses the performance that 1/8chip will serious disturbance offsets.In the tradition receiver, Multipath searching is to carry out before despreading fully, so the influence that the performance of Multipath searching is disturbed by multiple access also, than under the serious situation, the performance of whole system is with the main precision that is limited by Multipath searching in the multiple access interference ratio that exists between each subscriber signal.For traditional receiver, this situation can't be avoided, and is unique signal that can be used for carrying out Multipath searching because enter the CDMA signal of receiver, still, for the joint receiver that has interference cancellation, the signal after the interference eliminated can be used for carrying out Multipath searching.Because the signal after the interference eliminated has higher signal to noise ratio, can improve search performance so it is carried out Multipath searching.

Based on above-mentioned consideration, the guiding theory of joint receiver of the present invention is that Multipath searching is placed on after the interference eliminated, specifically, joint receiver of the present invention comprises matched filter banks 200, multistage interference cancellation group 204 and multipath group 205, matched filter banks 200 receives multiple user signals r, the pre-judgement of output signal d1, d2 ... dk is to multistage interference cancellation group 204, multistage interference cancellation group 204 output decision signal d1 ', d2 ' ... dk ' and interference cancellation signals r-1, r-2, r-k, wherein, interference cancellation signals r-1, r-2, r-k inputs to Multipath searching group 205, the Search Results p1 of Multipath searching group 205, p2 ... pk feeds back to matched filter banks 200 and many group interference cancellation groups 204 more respectively.

Matched filter banks 200 comprises a plurality of independently matched filter module 201, contain despreading module and channel estimating and Rake in each matched filter module 201 again and merge module, multistage interference cancellation group 204 comprises a plurality of interference cancellations unit 202, multipath group 205 comprises a plurality of Multipath searching modules, the despreading module of each matched filter module 201 in the matched filter banks 200 utilizes known scrambling code information to do relevant with delayed data to multi-user's received signal, modulation intelligence extracted from spread-spectrum signal deliver to channel estimating and Rake and merge module, channel estimating and Rake merge the decline value that module is estimated complex channel, and the phase place rotation and the changes in amplitude that take place when utilizing this estimated value compensating signal through channel, when multipath exists, carry out Rake and merge stack, promptly the signal in each footpath is superposeed by certain criterion, to improve signal to noise ratio, deliver to the first order interference cancellation unit in the multistage interference cancellation group 204 after the stack, the effect of multistage interference cancellation group 204 be regeneration and to interference among multiple users, afterbody interference cancellation unit is eliminating to export after multiple access disturbs to organize signals more, each group signal comprises decision signal and interference cancellation signals, wherein interference cancellation signals inputs to each multipath in the multipath group 205 more respectively, the effect of multipath group 205 is from regenerated signal { r_1, r_2, ..., extract multipath delay information in the r_K}, because regenerated signal { r_1, r_2, ..., r_K} has eliminated the subscriber signal that multiple access disturbs, so the multipath information of utilizing them to extract will be more accurate.Each multipath extracts multipath delay information, and the result is fed back to each grade interference cancellation unit 202 in the despreading module of each corresponding matched filter 201 in the matched filter banks 200 and the multistage interference cancellation group 204 respectively.The result of search so just make Multipath searching after interference cancellation, carry out, so will be more accurate.Again because the performance of despreading and interference cancellation all depends on the estimated accuracy of multipath delay, mean the performance (signal to noise ratio of signal after the despreading) that improves despreading and the efficient of interference cancellation so improve search precision.

If

It is j user's interference signal to k user.Then $r_{\_k}\left(t\right)=r\left(t\right)-{\mathrm{\Σ}}_{j\≠k}{\hat{s}}_j\left(t\right)$ It is the signal of removing the k user after disturbing.Utilize r _{_ k}(t) rather than r (t) as the input of k user's multipath, can improve the precision of Multipath searching.

In the present invention, the input signal of multipath is each user's of multistage interference cancellation output regenerated signal { r_1, r_2, r_K}, rather than the CDMA signal before the despreading.

According to multipath information change characteristic slowly, utilization has the multipath information of certain time-delay to carry out despreading and interference cancellation, matched filter banks 200 and multistage interference cancellation group 204 receive the multipath information of being extracted by multipath group 205, because having introduced, matched filter banks 200 and multistage interference cancellation group 204 handle time-delay T0 second, so the multipath information that despreading module and channel estimating and Rake merging module use is actually the multipath information of T0 signal before second.Because handling time-delay T0 generally is less than several ms, is far smaller than cycles tens ms that the signal multipath changes, so utilize the multipath information of T0 before second to go to predict that current multipath information is reliable.And startup stage, only need be disturbed regeneration and give null value, can obtain the effect identical with traditional joint receiver, treats the stable back of received signal (required time depends primarily on the channel estimating smooth length), switches to normal interference cancellation pattern.

Joint receiver of the present invention can improve the precision of Multipath searching, thereby improve the signal to noise ratio of despread signal and the efficient of interference cancellation, especially in the multiple access serious interference, when the system works signal to noise ratio is low, its effect is more obvious, in this case, confirms through emulation, the present invention can improve systematic function and reach 0.5db～1db, approximately amounts to into 13%～25% power system capacity increase.

In addition, of the present invention after receiver do not increase system complexity, only do certain adjustment to handling structure.Because interface is clear between the module, the upgrading of can more easily making amendment on traditional joint receiver.

Claims (2)

1, a kind of joint receiver that is used for code division multiple address communication system, it is characterized in that: this joint receiver comprises matched filter banks, multistage interference cancellation group and multipath group, matched filter group of received multiple user signals, the pre-judgement of output signal is to multistage interference cancellation group, multistage interference cancellation group output decision signal and interference cancellation signals, wherein, interference cancellation signals inputs to the Multipath searching group, and the Search Results of Multipath searching group feeds back to matched filter banks and many group interference cancellation groups more respectively.

2, the joint receiver that is used for code division multiple address communication system as claimed in claim 1 is characterized in that:

Described matched filter banks comprises a plurality of independently matched filter module, contains despreading module and channel estimating and Rake in each matched filter module again and merges module;

Described multistage interference cancellation group comprises a plurality of interference cancellations unit;

Described multipath group comprises a plurality of Multipath searching modules;

The despreading module of each matched filter module in the described matched filter banks utilizes known scrambling code information to do relevant with delayed data to multi-user's received signal, modulation intelligence extracted from spread-spectrum signal deliver to channel estimating and Rake and merge module, channel estimating and Rake merge the decline value that module is estimated complex channel, and the phase place rotation and the changes in amplitude that take place when utilizing this estimated value compensating signal through channel, carry out the first order interference cancellation unit of delivering to after the Rake merging superposes in the multistage interference cancellation group, afterbody interference cancellation unit is eliminating to export after multiple access disturbs to organize signals more, each group signal comprises decision signal and interference cancellation signals, wherein interference cancellation signals inputs to each multipath in the multipath group more respectively, each multipath extracts multipath delay information, and the result is fed back to each grade interference cancellation unit in the despreading module of each corresponding matched filter in the matched filter banks and the multistage interference cancellation group respectively.

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