CN1142688C - Selective merging method and device in multi-path diversity receiving - Google Patents

Abstract

The present invention provides a selective multi-path reception method for combining maximum ratios of a mobile communication system, which screens branches which can bring combination gain to combine maximum ratios in the process of multi-path reception, and two different communication systems using the method for incoherent multi-path reception and pilot auxiliary multi-path diversity reception. Quasi-maximum ratios are combined in an incoherent receiver; the present invention is enhanced greatly in performance compared with as equal gain combination or selectivity combination; diversity branched can be selected effectively in the incoherent receiver. The present invention makes full use of multi-path information, and enhances the accuracy of channel parameter estimation to combine the maximum ratios.

Description

The method and apparatus that selectivity merged during a kind of rake received

The present invention relates to the receiving system of mobile communication, especially relate to the method and apparatus that the selectivity high specific merges in the rake reception.

In mobile communication system, diversity reception is to produce from the characteristics of multipath transmisstion itself, and it is one of effective ways that overcome decline.The signal that receives from fading channel be the different delay that arrives receiver, out of phase the multipath vector and.If manage to get several groups of different vectors and, since each arrive vector and phase relation, each organizes vector and inevitable variant with the decline situation.Therefore, if selected several groups of vectors and independently of one another, then they will rise one after another, and the probability of several groups of vectors and decline simultaneously is just much smaller than one group of vector and the independent probability that declines.And then with suitable method several groups of vectors with merge use, total quality of reception is greatly improved.

In present mobile communication system, mainly contain two types Rake receiver: incoherent reception and pilot tone are assisted coherent reception.For incoherent reception, require multipath must find out multipath respectively on subscriber channel, this structure is relatively complicated, so adopt equal gain combining or selectivity to merge usually, can't make full use of the signal of other branch roads, receptivity is very limited; And in having the system of pilot signal,,, when merging, can run into the validity problem that participates in the multipath component that merges for Rake receiver provides time delay, intensity and the phase place of multipath component though can utilize pilot signal to carry out channel parameter estimation.

In view of there being abominable multipath fading phenomenon in the mobile telecommunication channel, the method that adopts rake to receive usually overcomes multipath fading, thereby realizes more efficiently reception.But participate in merging the result that just can bring receptivity to worsen in case more weak relatively branch road occurred; Even for mobile communication system, because the inexactness of channel parameter estimation if pure interference signal participates in merging, also can worsen receptivity with pilot channel.

Mathematical analysis below by the incoherent reception method during above-mentioned traditional rake is received illustrates the deficiency that this method exists.

The decision signal of k demodulation paths after despreading that is received by RAKE receiver can be expressed as:

r _k(t)＝s _k(t)+n _k(t) (1)

S in the following formula _k(t) be the signal composition, be actually baseband signal ± 1, pass through the response behind the RAKE receiver channel compensation again through Rayleigh channel.n _k(t) be noise component, comprise that multiple access disturbs and thermal noise (promptly common alleged white noise).

Following formula can get after merging:

$r\left(t\right)=\underset{k=1}{\overset{l}{\mathrm{\Σ}}}{c}_k{r}_k\left(t\right)=\underset{k=1}{\overset{l}{\mathrm{\Σ}}}{c}_k{s}_k\left(t\right)+\underset{k=1}{\overset{l}{\mathrm{\Σ}}}{c}_k{n}_k\left(t\right)........\left(2\right)$

C wherein _kBe gain coefficient, but l is the merge way number.Suppose that now first path signal is the strongest, order

α _k＝s _k/s _l 0≤α _k≤1 (3)

Because of the noise approximately equal of each demodulation paths in receiving end, the residual noise after demodulation is approximately equal also, makes that noise power is σ ², the noise of establishing each path is uncorrelated, and the signal to noise ratio after then can merging is:

$\mathrm{SNR}=\frac{{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{c}_k{s}_k\right)}^2}{{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{c}_k{n}_k\right)}^2}=\frac{{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{c}_k{a}_k\right)}^2}{{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{c}_k\right)}^2}\&CenterDot;\frac{{\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="C0110585400101.png"\; state="\{\{state\}\}">s</figure-callout>}}_1^2}{{\mathrm{\&sigma;}}^2}={\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="C0110585400101.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1\&CenterDot;\frac{{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{c}_k{a}_k\right)}^2}{{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{c}_k\right)}^2}........\left(4\right)$

Desire to make the signal noise ratio maximum, c _k(k=1 ... l) must satisfy condition:

$\frac{\&PartialD;\mathrm{SNR}}{{\&PartialD;c}_k}=0........\left(5\right)$

$\frac{{\&PartialD;}^2\mathrm{SNR}}{{\&PartialD;c}_k\&PartialD;c_m}=0$

As can be seen, merge in order to realize high specific, need the actual signal to noise ratio of measuring each branch road, so that in time gain coefficient is adjusted, this method implements the comparison difficulty, and cost is also bigger.

The objective of the invention is, the deficiency at the auxiliary coherent receiver of above-mentioned incoherent diversity receiver and pilot tone exists in the merging process after reception proposes a kind of performance and high specific and merges quite, but the lower method of complexity of realization.Promptly treat a plurality of paths that participate in to merge and do further screening, guarantee each path of adding can both bring to merge gain.

Another object of the present invention is under the certain situation of system processing power, to make a way that participates in handling less, thereby improve the processing speed of Rake receiver.

In noncoherent receiver, use this method, can realize that accurate high specific merges, on performance, improve a lot than equal gain combining or selectivity merging; In coherent receiver, use this method, then can select diversity branch effectively, make full use of the information on the multipath, improve the accuracy of channel parameter estimation, reach high specific and merge.

This selectivity high specific merging method of the present invention may further comprise the steps: in the multipath reception process, filter out and can bring the branch road that merges gain, carry out high specific and merge, said method comprising the steps of:

A) find out diversity branch possible in the received signal by Multipath searching, and arrange according to the watt level of described each branch road;

B) prominent branch road in the described arrangement is distributed to initial efficient set;

C) carry out validity and judge, determine whether next branch road in the described arrangement is merged to described efficient set,, enter step f) if can not merge;

D) the revision parameter is upgraded described efficient set;

E) get back to step c), carry out the judgement of a branch road behind the next-door neighbour of next branch road described in the described arrangement;

F) the effective branch road in the efficient set that judgement is obtained carries out despreading, demodulation respectively;

G) signal after described despreading, the demodulation is merged.

The invention still further relates to the auxiliary rake receiving system of pilot tone that a kind of selectivity high specific merges, comprising:

Multipath, received signal is also differentiated the possible diversity branch of described received signal;

The validity judgment means links to each other with multipath, is used to screen to bring merge each diversity branch that gain improves;

The PSA channel estimator according to the pilot signal of described validity each branch road that judgment means provides, is used to provide pilot signal to estimate channel parameter;

Despreading, demodulator link to each other with described validity judgment means, are used for according to described channel parameter, and each diversity branch that described validity judgment means is screened carries out despreading, demodulation respectively;

Combiner links to each other with the output of despreading, demodulator, is used to receive the signal behind described despreading, the demodulator despread-and-demodulation, merges then.

The non-coherent multi pathway diversity receiving device that the present invention also provides another kind of selectivity high specific to merge comprises:

Multipath, received signal is also differentiated the possible diversity branch of described received signal;

The validity judgment means links to each other with multipath, is used to screen to bring merge each diversity branch that gain improves;

Despreading, demodulator, be used for to each effective branch road expand respectively, demodulation;

Combiner links to each other with despreading, demodulator, is used to receive the signal after described despreading, the demodulator processes, realizes merging.

Adopt this method can realize effectively merging receiving, all there is certain contribution in each path that participates in merging to output signal, can obtain the highest merging signal to noise ratio.In addition, way N props up with regard to definite its treatable maximum usually in system when design, when the number of elements #A of effective set A props up way less than maximum, can put (N-#A) individual processing unit according to the validity sign E of gained is idle condition, so just can improve the processing speed of Rake receiver.

Suppose that each branch road arranges from big to small by its power, so have:

α _l≤α _l-1≤…≤a ₂≤a ₁ (7)

A wherein ₁=1.

If waiting each branch road that participates in merging satisfies:

$\frac{1}{l}{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{a}_k\right)}^2\&GreaterEqual;\frac{1}{l-1}{\left(\underset{k=1}{\overset{l-1}{\mathrm{\&Sigma;}}}{a}_k\right)}^2.........\left(8\right)$

Promptly add power ratio sum behind the l branch road greater than the power ratio sum of (l-1) bar branch road, this just expression can guarantee the l branch road merge after this path can bring gain, promptly the l branch path is effective diversity branch.

Wherein,

$P_l=\frac{1}{l}{\left(\underset{k=1}{\overset{l}{\mathrm{\&Sigma;}}}{a}_k\right)}^2{\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="C0110585400101.png"\; state="\{\{state\}\}">s</figure-callout>}}_1^2..........\left(9\right)$

P _lIt is the signal power after l branch road merges.In other words, in order not worsen the receptivity after the merging, when the signal to noise ratio of demodulation paths is reduced to a certain degree, it must be rejected.

Below in conjunction with accompanying drawing, by detailed description of the present invention, advantage of the present invention, characteristic and purpose will be apparent.

Fig. 1 is the flow chart that adopts validity determination methods in the multipath selection course of the present invention;

Fig. 2 is the structural representation of the auxiliary Rake receiver of pilot tone of the present invention;

Fig. 3 is the structural representation of non-coherent multi pathway diversity receiver of the present invention;

The high specific that Fig. 4 is to use the Cossap simulation software to produce merges the merging design sketch of (MRC), equal gain combining (ERC) and the inventive method.

Below, describe preferred embodiment of the present invention in detail with reference to accompanying drawing.

Fig. 1 provides the flow process that realizes validity determination methods in the multipath selection course.Before carrying out the validity judgement, multipath received signal in being received by RAKE is earlier also found out each possible diversity branch, enter step 100 then, select a front distinguishable N branch road, and N bar diversity branch that will be to be screened according to the branch power size by descending; Next enter step 101, initialization set and parameter suppose that A represents active set, promptly put into being to bring and merging gain wherein, participate in effective branch road collection of merging the most at last, and U represents to treat selected works, inserts the branch road that will accept to screen, E _iThe validity sign that expression branch road set pair is answered represents that with 0 and 1 i bar branch road turn-offs or effective two states, C _iThe weighted factor of representing its each branch road correspondence participates in final merging process.Here use L _iRepresent i bar branch road, because the branch road collection is through ordering, so each branch road L ₁, L ₂, L ₃..., L _NPower also be from big to small, in case detect the merging power that adds behind the i bar branch road power less than front (i-1) bar branch road, arriving, this stops judging.

Specifically, in the initialization procedure, set active set A=(L ₁), promptly at first be positioned among the active set A according to first branch road after the watt level descending (branch power maximum), treat selected works U=(L this moment ₂, L ₃..., L _N), E ₁=1, C ₁=1.

Then, enter step 102 and carry out two power calculation respectively, if filter out (i-1) individual diversity branch, i.e. A=(L in the active set A ₁, L ₂..., L _I-1), the power after this (i-1) individual diversity branch merges is P _I-1, the power after i branch road merges behind the calculating adding i bar branch road is P _iEnter validity determining step 103 then, if P _i〉=P _I-1, then can conclude to add to have brought behind the i bar branch road to merge gain, change step 104 over to, with L _iAdd among the active set A, then according to (C ₁, C ₂..., C _I-1) and before the power ratio in relative the 1st path of i branch road calculate C _iUpgrade each set, at this moment, active set A=(L ₁, L ₂..., L _i), treat selected works U=(L _I+1, L _I+2..., L _N), E _i=1, then get back to step 102, carry out the validity of next branch road and judge; If P _i≤ P _I-1, then changing step 105 over to, end loop draws final active set A and each branch road relevant parameters C, E.

After effectively being merged collection A, just can the despreading respectively of each branch road, the demodulation that is wherein screened be merged then.This method can be applied in a flexible way in different communication systems.Describe in conjunction with two kinds of diversity receivers respectively below.

With reference to Fig. 2, be depicted as the structural representation of the auxiliary Rake receiver of pilot tone.

In the auxiliary coherent receiver of pilot tone, received signal r (t) tells the possible multipath (L of N bar through multipath 1 ₁, L ₂..., L _N), these branch roads get the branch road collection (L that participates in merging to the end after handling through validity judgment means 2 ₁, L ₂..., L _n), PSA channel estimator 3 utilization waits that the pilot signal of effective branch road of participating in merging forms channel parameter then, and this channel parameter sent in despreading, the demodulator 4, according to each effective branch road and channel parameter corresponding, each branch road expands, the demodulation computing, effective branch road after the demodulation finally enters combiner 5, carries out high specific according to equation (2) and merges.

In incoherent diversity receiver, received signal r (t) tells the possible multipath (L of N bar through multipath 6 ₁, L ₂..., L _N), these branch roads get the branch road collection (L that participates in merging to the end after handling through validity judgment means 7 ₁, L ₂..., L _n) and weighted factor collection (C ₁, C ₂..., C _n), use 8 couples of L of despreading, demodulator of corresponding each branch road then ₁～L _nEach branch road carries out despreading, demodulation process respectively, realizes that according to equation (2) accurate high specific merges by combiner 9 at last.

Please refer to Fig. 4, be depicted as the simulated effect figure that adopts a preferred embodiment of selectivity high specific merging method of the present invention.With Cossap simulation software formation double antenna data instance (signal is through the Rayleigh channel decline), three curves represent that respectively high specific merges (MRC), equal gain combining (ERC) and selectivity high specific of the present invention and merge the schematic diagram that (SRC) three kinds of methods concern between diversity branch number and merging benefit among the figure.As can be seen, the merging gain that this method realizes very merges curve near high specific along with the increase of diversity branch number.In this example, the signal strength signal intensity of each branch road that merges when selected participation must satisfy: a ₁=1, a ₂〉=0.414, a ₃〉=0.318, a ₄〉=0.268 o'clock, just can participate in merging, corresponding gain coefficient is: C ₁=1, C ₂=0.75, C ₃=0.5, C ₄=0.25.

The front provides the description to preferred embodiment, so that any technical staff in this area can use or utilize the present invention.Various modifications to these embodiment are conspicuous to those skilled in the art, can be applied to other embodiment to total principle described here and not use creativeness.Thereby, the embodiment shown in the present invention will be not limited to here, and the wide region of principle that should disclose and new feature according to meeting here.

Claims (6)

1. the method that mobile communication system multipath reception selectivity high specific merges in the multipath reception process, filters out and can bring the branch road that merges gain, carries out high specific and merges, and said method comprising the steps of:

A) find out diversity branch possible in the received signal by Multipath searching, and arrange according to the watt level of described each branch road;

B) prominent branch road in the described arrangement is distributed to initial efficient set;

C) carry out validity and judge, determine whether next branch road in the described arrangement is merged to described efficient set,, enter step f) if can not merge;

D) the revision parameter is upgraded described efficient set;

E) get back to step c), carry out the judgement of a branch road behind the next-door neighbour of next branch road described in the described arrangement;

F) the effective branch road in the efficient set that judgement is obtained carries out despreading, demodulation respectively;

G) signal after described despreading, the demodulation is merged.

2. method according to claim 1 is characterized in that, described validity determining step c) comprising:

A ') power of described all branch roads of efficient set of calculating;

B ') by descending branch road is added described efficient set, and calculate and to incorporate behind one branch road of back the power of all branch roads in the efficient set into;

C ') more above-mentioned a ') and b ') power of one branch road of back described in the step before and after incorporating into, according to effectiveness condition described branch road is judged.

3. method according to claim 2 is characterized in that, described comparison step c ') comprising:

A ") is if after adding described back one branch road, and the power before the power after merging in the described efficient set merges is big, and described branch road is retained in the efficient set;

B ") is if after adding described back one branch road, and the power before the power after merging in the described efficient set merges is little, cancels described branch road, finishes validity and judges.

4. method according to claim 1 and 2 is characterized in that, described parameter comprises weighted factor and the validity sign that described each set is corresponding.

5. the pilot tone of a selectivity high specific merging is assisted the rake receiving system, comprising:

Multipath, received signal is also differentiated the possible diversity branch of described received signal;

The validity judgment means links to each other with multipath, is used to screen to bring merge each diversity branch that gain improves;

The PSA channel estimator according to the pilot signal of described validity each branch road that judgment means provides, is used to provide pilot signal to estimate channel parameter;

Despreading, demodulator link to each other with described validity judgment means, are used for according to described channel parameter, and each diversity branch that described validity judgment means is screened carries out despreading, demodulation respectively;

Combiner links to each other with the output of despreading, demodulator, is used to receive the signal behind described despreading, the demodulator despread-and-demodulation, merges then.

6. the non-coherent multi pathway diversity receiving device that merges of a selectivity high specific comprises:

Multipath, received signal is also differentiated the possible diversity branch of described received signal;

The validity judgment means links to each other with multipath, is used to screen to bring merge each diversity branch that gain improves;

Despreading, demodulator, be used for to each effective branch road expand respectively, demodulation;

Combiner links to each other with despreading, demodulator, is used to receive the signal after described despreading, the demodulator processes, realizes merging.

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