CN1287424A - Interference eliminator in CDMA receiver - Google Patents

Interference eliminator in CDMA receiver Download PDF

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Publication number
CN1287424A
CN1287424A CN00118791A CN00118791A CN1287424A CN 1287424 A CN1287424 A CN 1287424A CN 00118791 A CN00118791 A CN 00118791A CN 00118791 A CN00118791 A CN 00118791A CN 1287424 A CN1287424 A CN 1287424A
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China
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interference
adjustment factor
signal
power
eliminator
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CN00118791A
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Chinese (zh)
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二见哲宏
关宏之
田中良纪
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Fujitsu Ltd
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Fujitsu Ltd
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Abstract

Interference eliminator in code division multiple access(CDMA)receiver is able to eliminate interference from the received signal by multiplying the interference replication with an adjustment coefficient and then removing the resulted interference replication from the received signal. The interference eliminator comprises an adjustment coefficient control unit used for adjusting the adjustment coefficient based on the estimation for interference eliminating characteristic to improve the interference eliminating characteristic.

Description

Interference eliminator in the cdma receiver
The present invention relates generally to a kind of interference eliminator, relate in particular to a kind ofly, in the receiver that honeycomb fashion direct sequence CDMA mode (DS/CDMA) radio base stations in mobile communication is used, eliminate the interference eliminator of the interference that causes by other channel.
In honeycomb fashion direct sequence CDMA mode (DS/CDMA) mobile communication system, the interference that the cross-correlation of being encoded by channel spread produces causes the decline of system channel capacity and transmission quality.Therefore, preferably from received signal, remove this interference as much as possible.
Fig. 1 has illustrated a formation that comprises direct sequence CDMA mode (DS/CDMA) the radio base station receiver of a common interference eliminator 24.This receiver has adopted digital modulation techniques such as Quadrature Phase Shift Keying (QPSK) technology.
As shown in Figure 1, the CDMA ripple is received by antenna 20 and is sent to receiving element 21, is demodulated to baseband signal.Convert this baseband signal to digital signal by modulus (A/D) transducer 22 then and deliver to passage searching circuit 23.After this, this digital signal is input to common interference eliminator 24 as received signal " r ".
This interference eliminator 24 produces a plurality of interference replicas according to received signal " r ", according to received signal " r ", each corresponding channel, then from received signal " r " thus remove that these interference replicas are eliminated because the interference between the asynchronous spread spectrum coding that causes of mobile radio station, promptly from the interference of other channel.Received signal " r " after elimination is disturbed is input to each receiving element (demodulating unit) 5 of user (channel 1 is to k) 1To 5 k
The formation that it is so-called parallel interference canceller that Fig. 2 illustrates common interference eliminator 24.
As shown in Figure 2, received signal " r " is input to each interference eliminator unit (ICU) 1 corresponding with mobile radio station (user) k 1To 1 kInterference eliminator unit (ICU) 1 1To 1 kProduce and mobile radio station k corresponding symbol reproducing signals S 1To S kWith interference replica signal d 1To d kSymbol reproducing signals S 1To S kBe sent to the receiving element corresponding 5 respectively with mobile radio station k 1To 5 k, while interference replica signal d 1To d kDeliver to adder 2.
Adder 2 adds up by corresponding interference eliminator unit (ICU) 1 1To 1 kThe interference replica signal d that produces 1To d kAnd accumulated value is delivered to interference remove unit (subtracter) 4, from received signal " r ", remove this accumulated value, thereby obtain a residual signal " e ".
Here because interference replica signal d 1To d kReliability low, as the interference replica signal d of low reliability 1To d kWhen from received signal " r ", removing, can reduce the interference eliminated characteristic of interference eliminator.Therefore, the adjustment factor β of reaction reliability is according to relevant received power, and information such as mobile radio station quantity are determined, so that pass through interference replica signal d 1To d kMultiply by adjustment factor β and improve the interference eliminated characteristic.
Fig. 2 illustrates an example, its adder 2 interference replica signal d that adds up 1To d kAnd accumulated value delivered to multiplier 3; Multiplier 3 with this add up on duty in adjustment factor β and will take advantage of the result deliver to subtracter 4; Subtracter 4 from received signal " r " thus remove this take advantage of the result obtain a residual signal " e ".So just improved the interference eliminated characteristic.
After this, the symbol reproducing signals S of residual signal " e " and mobile radio station 1To S kAll be input to the corresponding receiving element 5 corresponding with mobile radio station 1To 5 kReceiving element 5 1To 5 kTo corresponding mobile station decoding residual signal " e " and reproducing signals S 1To S k
Fig. 3 graphic extension 1 1To 1 kI interference eliminator unit ICU in the interference eliminator unit (ICU) i, wherein i represents the sequence number of corresponding certain mobile radio station (user).
As shown in Figure 3, the received signal " r " that is input to ICU at first is input to despread unit 10, utilizes the spread spectrum coding despreading received signal " r " corresponding with mobile radio station " i " so that export a receiving symbol R iThen, receiving symbol R IBe input to the channel estimation circuit 11 that is used to estimate channel (transmission line characteristics, such as: rotation of phase place in the transmission space or amplitude variations etc.), and utilize existing information such as: be included in the channel estimation value ξ of frequency pilot sign output in the transmission signals i
Fig. 5 illustrates time-division pilot transmission information frame figure.As shown in the figure, frequency pilot sign and information symbol all insert in each time slot of a transmission signals (as: 0.625ms).
The received signal R of multiplier 12 by despread unit 10 is produced iMultiply by the channel estimation value ξ that produces by channel estimation circuit 11 iConjugate complex number ξ iAnd after removing the phase shift that transmission symbol is applied, just obtain a received signal R who removes phase shift *, iξ i*.Then, with this received signal R iξ i* deliver to data determining unit 13, with received signal R iξ i* compare with a threshold values, so that finish the temporary transient judgement of data symbol.
Multiplier 14 was by judging temporarily that symbol multiply by channel estimation value ξ i, produced one as receiving symbol R iThe symbol reproducing signals S that duplicates iAfterwards, symbol reproducing signals S iUnit 15 is expanded in input again, utilizes the spread spectrum coding of corresponding mobile radio station (i.e. i mobile radio station) to expand symbol reproducing signals S again iSo that produce an interference replica signal d iAfterwards, interference replica signal d iDeliver to disturb and remove unit 4, symbol reproducing signals S IDeliver to the receiver corresponding 5 with the i mobile radio station i
Fig. 4 graphic extension receiving element 5 1To 5 kIn corresponding to the receiving element 5 of i mobile radio station iFormation.
As shown in Figure 4, receiving element 5 iMainly comprise a despreading processing unit 50 and a decoder 55.Despreading processing unit 50 have with above-mentioned ICU in despread unit and the essentially identical despread unit 51 of channel estimation circuit and a channel estimation circuit 52.By disturbing the residual signal " e " of removing unit 4 generations to deliver to despread unit 51, by carrying out and ICU iIdentical process produces a receiving symbol Qi.Adder 53 is with receiving symbol Qi with by corresponding ICU iThe symbol reproducing signals S that produces iThereby addition produces a receiving symbol R who has removed the interference of other mobile radio station iAfterwards, multiplier 54 is with receiving symbol R iMultiply by the channel estimation value ξ that produces by channel estimation circuit 52 iConjugate complex number ξ i*, produce a receiving symbol R who removes the transmission line phase shift iξ i*, and with this receiving symbol R iξ i* deliver to decoder 55.Decoder 55 is with receiving symbol R iξ i* compare with a threshold values and as decoded symbol data.
Yet, in common interference eliminator, eliminate interference by from received signal, removing its inner interference replica that produces, if the interference replica that is produced inaccurate (low reliability), owing to can from received signal, remove interference replica mistakenly, can increase interference power.As a result, the unsteadiness of interference replica has had a strong impact on the interference eliminated characteristic of interference eliminator.
Therefore, the adjustment factor β that interference replica be multiply by an expression reliability can improve the interference eliminated characteristic effectively so that alleviate the influence that is caused by the low interference replica of reliability.
Usually, according to the information of relevant received power or mobile radio station quantity, can be before disturb removing the predicted interference reliability of duplicating in advance, determine an adjustment factor β according to prediction.Yet the reliability of interference replica depends on multiple condition, and what work out an adjustment factor table that comprises the combination of various conditions in order to find the optimum adjustment factor beta and be difficulty also is unpractical.Wherein, maximum doppler frequency is a key factor determining the reliability of interference replica, but radio base station can not obtain the information about it.As a result, the predetermined adjustment factor beta differs and obtains Optimal Jamming surely and eliminate characteristic.
A basic purpose of the present invention provides a kind of interference eliminator that can overcome above-mentioned deficiency.
Thereby of the present invention another more specifically purpose provide a kind of interference eliminator that improves the interference eliminated characteristic by adjustment factor of suitable control as far as possible.
Above-mentioned purpose of the present invention and other purpose are realized by a kind of interference eliminator of cdma communication system, disturb in order to eliminate from received signal, remove from described received signal after interference replica be multiply by an adjustment factor, and described interference eliminator comprises:
Estimation according to the interference eliminated characteristic is controlled described adjustment factor and is improved the adjustment factor control unit of interference eliminated characteristic.
Can understand the features and advantages of the present invention better by following detailed description of the invention and with reference to the accompanying drawing of the leading case that is used for the diagram application principle of the invention.
Fig. 1 illustrates a structure that comprises the base station receiver of common interference eliminator;
Fig. 2 illustrates the structure of common interference eliminator shown in Figure 1;
Fig. 3 illustrates the structure of the interference eliminator unit (ICU) of common interference eliminator shown in Figure 2;
Fig. 4 illustrates the structure of the receiving element of common interference eliminator shown in Figure 2.
Fig. 5 shows time-division pilot transmission information frame figure;
Fig. 6 illustrates the structure according to an interference eliminator of first scheme of the present invention;
Fig. 7 illustrates the structure according to an interference eliminator of alternative plan of the present invention;
Fig. 8 illustrates the structure according to an interference eliminator of third party's case of the present invention;
Fig. 9 illustrates the structure according to an interference eliminator of cubic case of the present invention;
Figure 10 illustrates the structure according to an interference eliminator of the 5th scheme of the present invention;
Figure 11 illustrates the structure of n interference eliminator unit (ICU) of the interference eliminator of the 5th scheme; With
Figure 12 illustrates the structure according to an interference eliminator of the 6th scheme of the present invention.
Below with reference to description of drawings preferred version of the present invention.
The interference eliminator of the present invention's first scheme at first, is described with reference to figure 6.
The interference eliminator of first scheme shown in Fig. 6 can be applied to the receiver that use CDMA mobile communication system base station shown in Figure 1.
As shown in Figure 6, interference eliminator comprises interference eliminator unit (ICU) 1 1To 1 k, adder 2, adjustment factor multiplier 3, disturb and remove unit 4 and receiver 5 1To 5 k, in " explanation of technology related to the present invention ", they are illustrated.
Different with common interference eliminator, the interference eliminator of first scheme further comprises an adjustment factor control circuit 6, an interference power measuring circuit 7 and an interference power measuring circuit 8.
Interference power measuring circuit 7 be used to measure received signal " r " power and disturb before removing with this power definition be interference power (hereinafter referred to as: the interference power before removing).Interference power measuring circuit 8 be used to measure by the power that disturbs the residual signal " e " of removing unit 4 outputs (removing the received signal " r " after disturbing) and with the power definition of residual signal " e " be removed interference power after disturbing (hereinafter referred to as: the interference power after the removal).Adjustment factor control circuit 6 is determined adjustment factor according to interference power before removing and the interference power after the removal.
In this scheme, received signal " r " comprises the signal of whole a plurality of mobile radio stations.When utilizing the coding despreading received signal " r " of each mobile radio station, all signals except that the our station signal all are counted as disturbing.The power that is received signal " r " becomes big more, and it is big more that the power of interference also becomes.Equally, the interference power after the power of removing the residual signal " e " of interference replica gained by received signal " r " is counted as removing.Correspondingly, interferometry circuit 7 is measured the power of received signal " r " as the interference power before removing, and interferometry circuit 8 is measured the power of residual signal " e " as the interference power after removing.
About the estimation to the interference eliminated characteristic, the most direct method is exactly with the interference power before removing and the interference power after removing compares.Should notice that the interference eliminated characteristic becomes good more (accurate more), it is just many more that the interference power after the removal reduces.At this, by the interference power before corresponding interference power measuring circuit 7 and 8 removals that record and the interference power after removing deliver to adjustment factor control circuit 6, when regulating adjustment factor β, they are compared the minimizing value that makes interference power become maximum (interference power before removing and remove after the difference of interference power become maximum).
In this scheme, adjustment factor β can be set between the 0-1.So both made the transmission conditions in transmission channel have uncertain variation, adapted to transmission conditions, eliminated characteristic so always can obtain Optimal Jamming owing to can regulate adjustment factor β.
In addition, in this scheme, two interferometry circuit 7 and 8 be used to measure the interference power before removing and remove after interference powers.The interference eliminated characteristic can be estimated by certain interferometry circuit, the interference power before removing like this and remove after interference power can measure or only according to the interference power estimation after removing in the mode of timesharing.
The interference eliminator of alternative plan of the present invention then, is described below with reference to Fig. 7.
Different with the interference eliminator of first scheme of the interference power after interference power before removing and the removal being done mutual comparison, in the interference eliminator of alternative plan, will disturb the signal interference/noise before from received signal " r ", removing to compare mutually than (SIR) with disturbing the signal interference/noise after from received signal " r ", removing than (SIR).In this scheme,, when regulating adjustment factor β, estimate the interference eliminated characteristic by comparing these two ratios.
After this, disturb signal interference/noise before from received signal " r ", removing than (SIR) with disturb the signal interference/noise after from received signal " r ", removing to be hereinafter referred to as the signal interference/noise of the preceding signal interference/noise of removal after than (SIR) than (SIR) and removal than (SIR).
As shown in Figure 7, compare with comprising interference power measuring circuit 7 and 8 in first scheme, the interference eliminator of alternative plan comprises that the signal interference/noise is than (SIR) average circuit 9 and 10.Furtherly, interference eliminator unit (ICU) 1 1To 1 kWith receiver 5 1To 5 kThe signal interference/noise that can measure corresponding mobile station received signal compares SIR 1To SIR kIn addition, according to the average power of the received signal after the despreading " r ", interference eliminator unit (ICU) 1 1To 1 kIn each interference eliminator unit ICU i(1≤i≤k) obtain a diffusion component as interference utilizes average power and diffusion component picked up signal interference/noise to compare SIR afterwards i
In order to obtain an average signal interference/noise before the removal than (SIR), and will be in corresponding interference eliminator unit (ICU) 1 1To 1 kThe signal interference/noise of measuring compares SIR 1To SIR kDeliver to the signal interference/noise than (SIR) average circuit 9 and average.On the other hand, in order to obtain a signal interference/noise after the removal than (SIR), needing will be at corresponding receiving element 5 1To 5 kThe signal interference/noise of measuring compares SIR 1To SIR kDeliver to the signal interference/noise than (SIR) average circuit 10 and average.Then, average signal interference/noise before the removal that produces than (SIR) average circuit 10 than (SIR) average circuit 9 and signal interference/noise by corresponding signal interference/noise than (SIR) and the average signal interference/noise after removing all be sent to adjustment factor control circuit 6 than (SIR), according to these two average signal interference/noise than (SIR) adjusting adjustment factor β.
From description, be appreciated that and estimate the interference eliminated characteristic by the average signal interference/noise of the average signal interference/noise before relatively removing after than (SIR) than (SIR) and removal to alternative plan.It is good more that the interference eliminated characteristic becomes, and the signal interference/noise of the receiving symbol of mobile radio station compares SIR 1To SIR kJust big more.In this scheme, when regulating adjustment factor β, the average signal interference/noise of the average signal interference/noise before adjustment factor control circuit 6 is relatively removed after than (SIR) and removal improved the signal interference/noise and compared SIR to realize the best than (SIR) 1To SIR k
In this scheme, for the average signal interference/noise before obtaining to remove than (SIR), and in corresponding interference eliminator unit (ICU) 1 1To 1 kThe signal interference/noise of measuring mobile radio station compares SIR 1To SIR kAnd average than (SIR) average circuit 9 in the signal interference/noise; For the average signal interference/noise after obtaining to remove than (SIR), and at corresponding receiving element 5 1To 5 kThe signal interference/noise of measuring mobile radio station compares SIR 1To SIR kAnd average than (SIR) average circuit 10 in the signal interference/noise.
Then, below with reference to Fig. 8 the interference eliminator of third party's case of the present invention is described.
In third party's case, mobile radio station is divided into several groups by certain standard.In every group, the mobile radio station in organizing is carried out the adjusting of public adjustment factor, the conditioning desired factor beta can be determined flexibly to this group like this, and the interference eliminated characteristic can be improved.
Promptly in first and second schemes, whole mobile radio stations are carried out adjustment factor control, and because the mutual transmission conditions difference of mobile radio station, the optimum value of adjustment factor β changes according to mobile radio station.Yet because the scale of system can become very huge, it is unpractical that each mobile radio station is carried out adjustment factor control separately.Furtherly, if only improve the interference eliminated characteristic of certain mobile radio station, because this improvement is too small, so it can be offset by the variation of noise or transmission conditions.As a result, in first and second schemes, come the regulating and controlling coefficient unsatisfactory based on the improvement of characteristic.
Correspondingly, in third party's case, mobile radio station is divided into several groups, at every group public adjustment factor is controlled.
As shown in Figure 8, in this scheme, all interference eliminator unit (ICU) are divided into M group #1 to #M, and every group comprises a plurality of interference eliminators unit (ICU).The definition of desirable grouping standard is that the mobile radio station in same group has interference replica reliability at the same level.For example, standard can be that receiving symbol power, receiving symbol signal interference/noise are than (SIR), transmission rate or the like.If with the receiving symbol power definition is the grouping standard, because receiving symbol power is subjected to the influence of distance between mobile radio station and the base station, for example mobile radio station can be divided into a distant place group, and mobile radio station wherein is away from the base station; And a nearly side group, mobile radio station wherein is near the base station.Can organize in the distance like this and nearly Fang Zuzhong adjusting adjustment factor β.
Every group among the mobile radio station group #1 to #M comprises: the adder (2 of the interference replica that produced by every group interference eliminator unit (ICU) of being used to add up 1-2 M), a multiplier (3 that is used for interference replica be multiply by adjustment factor β #1-3 #M), one disturb to remove unit (4 #1-4 #M), one according to removing forward and backward interference power regulating and controlling coefficient (β #1-β #M) adjustment factor control circuit (6 #1-6 #M) and an interference that is used to measure the interference power after the removal remove circuit (8 #1-8 #M).
In addition, in Fig. 8, " M " is group number, and " M, KM " is the number that belongs to the mobile radio station of #M group.
In this structure, adjustment factor is to control separately in every group of mobile radio station group #1 to #M, therefore adjustment factor can be adjusted to a best relatively value for the mobile radio station in this group in every group.As a result, can determine neatly that the conditioning desired coefficient also can improve the interference eliminated characteristic.
The interference eliminator of the cubic case of the present invention then, is described below with reference to Fig. 9.
In mobile communication system,, often adopt space diversity reception to communicate to merge the signal that receives by a plurality of antenna branch in order to obtain good reception.In each antenna branch, can adopt to have first the interference eliminator of adjustment factor control unit to arbitrary scheme of third party's case.
As shown in Figure 9, in this scheme, have and have adjustment factor control circuit 6 identical and first antenna branch and second antenna branch of 6 ＇ respectively with adjustment factor control circuit 6 in first scheme.The interference eliminator corresponding with first and second antenna branch has same structure.Receiver 5 1To 5 kDespreading processing unit (50 1-50 kWith 50 1＇-50 k＇) with shown in Figure 4 identical, the multiplier that each branch includes despread unit, is used for the adder of summation sign reproducing signals, channel estimation circuit and is used for reproducing signals be multiply by channel estimation value.
In first and second antenna branch, two received signals " r1 " and " r2 " are handled by two interference eliminated and despreading.To each mobile radio station, signal " r1 " and " r2 " are by diversity merge cells 56 then 1To 56 kDiversity merges, and outputs to decoder 55 1To 55 kData are decoded.
The interference eliminator of the 5th scheme according to the present invention then, is described below with reference to Figure 10.
The interference eliminator of the 5th scheme belongs to a kind of interference eliminator of multi-stage type, and the generation of its interference replica signal and elimination repeat repeatedly, and the interference meeting that can not eliminate fully in one-level is further eliminated in following stages like this.This interference eliminator can be configured to, be provided with any adjustment factor control circuit in first to fourth scheme in each interference cancellation stage.
As shown in figure 10, in this scheme, this interference eliminator comprises every grade of two-stage that all has the adjustment factor control unit of first scheme.
Notice that if adopt the multi-stage type interference eliminator, level (n) (n＞1, level number is eliminated in " n " representative) is eliminated by configuration shown in Figure 11 by configuration shown in Figure 3 in the interference eliminator unit (ICU) of eliminating level (1).
Different with the interference eliminator unit (ICU) of eliminating level (1), as shown in figure 11, each interference eliminator unit (ICU) of eliminating level (n) is configured to have: one will be duplicated S by the last symbol of eliminating interference eliminator unit (ICU) input of level (n-1) i (n-1)With despread unit 10 (n)An output addition and produce a receiving symbol R i (n)Adder 16 (n), one symbol is duplicated S i (n-1)With by with data determining unit 13 (n)The data symbol and the channel estimation value ξ of output i (n)The symbol of the elimination level (n) that obtains of multiplying each other duplicates S i (n)The adder 17 of anti-phase adding (promptly subtracting each other) (n)With adder 17 (n)Subtract result input expand unit 15 again (n)To produce an interference replica signal d i (n)In this configuration, interference replica signal d i (n)Be to produce according to interference of all eliminating in last elimination level (n-1).
Figure 12 illustrates a kind of interference eliminator of the present invention's the 6th scheme.The 6th scheme is cubic case and the 5th scheme mixture, has adopted space diversity and multistage interference eliminated.As shown in figure 12, interference eliminator comprises two antenna branch and has two interference cancellation stage of the adjustment factor control unit of first scheme employing at each grade, and measures interference power so that estimate the interference eliminated characteristic.
It is all can use the present invention and the realization best mode of being imagined by the inventor of the present invention has been described for any technical staff who makes this area that above-mentioned explanation is provided.
The present patent application is that its full content proposes for reference in the lump based on the No.11-188911 Japanese priority application that proposed on July 2nd, 1999.
Obviously, when application is of the present invention, may adopt the present invention program's described herein various alternatives.Appended claim attempts to determine scope of the present invention and contained its structure and method in these claims and equivalent thereof.

Claims (6)

1. interference eliminator in cdma communication system disturbs in order to eliminate from received signal, and interference replica be multiply by an adjustment factor and removes from described received signal, and described interference eliminator comprises:
A basis is controlled the adjustment factor control section that described adjustment factor improves described interference eliminated characteristic to the estimation of interference eliminated characteristic.
2. interference eliminator according to claim 1, it is characterized in that, when regulating described adjustment factor, described adjustment factor control section compares with the interference power of eliminating after the described interference the interference power of eliminating before the described interference, so that reduce interference power as much as possible.
3. interference eliminator according to claim 1, it is characterized in that, when regulating described adjustment factor, the signal power of described adjustment factor control section before to described interference eliminated compares the ratio of interference power and the signal power after the described interference eliminated ratio to interference power, so that improve the ratio of signal power to interference power as much as possible.
4. interference eliminator according to claim 2, it is characterized in that, described adjustment factor control section is arranged in each group in a plurality of groups that have divided receive channel, so that the independent described adjustment factor of control in each group in described a plurality of groups.
5. interference eliminator according to claim 1, it is characterized in that, described adjustment factor control section is arranged in each branch in a plurality of antenna branch, so that the described adjustment factor of control separately in each branch in described a plurality of antenna branch.
6. interference eliminator according to claim 1, it is characterized in that, described adjustment factor control section is arranged in every grade of a plurality of interference cancellation stage, the generation of described interference replica and eliminate and can repeat is so that at every grade of the described interference cancellation stage described adjustment factor of control separately.
CN00118791A 1999-07-02 2000-06-29 Interference eliminator in CDMA receiver Pending CN1287424A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP18911199 1999-07-02
JP188911/1999 1999-07-02

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Publication Number Publication Date
CN1287424A true CN1287424A (en) 2001-03-14

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CN00118791A Pending CN1287424A (en) 1999-07-02 2000-06-29 Interference eliminator in CDMA receiver

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CN (1) CN1287424A (en)

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