CN1145293C - Joint detection and processing method under variable bandspread factor - Google Patents
Joint detection and processing method under variable bandspread factor Download PDFInfo
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- CN1145293C CN1145293C CNB011000937A CN01100093A CN1145293C CN 1145293 C CN1145293 C CN 1145293C CN B011000937 A CNB011000937 A CN B011000937A CN 01100093 A CN01100093 A CN 01100093A CN 1145293 C CN1145293 C CN 1145293C
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Abstract
The present invention relates to a combined detecting and processing method under a variable frequency-spreading factor, which adopts a frequency-spreading factor which is generated according to a tree structure. The present invention is characterized in that a single user which uses a short first frequency-spreading factor is equivalent to a plurality of users which use a long second frequency-spreading factor according to the tree structure of the generated frequency-spreading factor. The combined detection under a fixed frequency-spreading factor is carried out, and then, a demodulation result of the user which uses the first frequency-spreading factor is reduced according to demodulation results of the equivalent users.
Description
The present invention relates to multi-user's spread spectrum radio communication system, particularly relate to a kind of united detection processing method that becomes under the spreading factor of in multi-user's spread spectrum radio communication system, using.
For general spectrum-spread multi-user communicaltion system, multiple access disturbs the key factor that influences systematic function such as power system capacity etc. often.In the prior art, adopt the technology of joint-detection to overcome the multiple access interference sometimes, or weaken the influence of multiple access interference systematic function.
Associated detection technique is a kind of in the multiuser detection, and associated detection technique can improve the performance of system greatly.In traditional DS-CDMA system, utilize conventional matched filter to detect each user's signal, and disturb (MAI) not deal with to multiple access, and in joint-detection, a plurality of users' code word, channel information join together to detect each individual consumer's information, and each user's of supposition code word and channel information are known in joint-detection.The optimum detection mode of joint-detection is maximum likelihood sequence detector (MLS), but difficult the realization, and accurate best detector comprises linear solution correlation detector, subtractive interference cancellation device, multistage detector etc.Wherein concrete algorithm such as successive interference cancellation device (SIC), parallel interference cancellation device (PIC), ZF decision-feedback (ZF-DF) detector etc.Associated detection technique under the regular length spreading factor has been suitable mature technique.
But because diversity of operations and time variation that the complexity of channel and time variation and system are transmitted, at recent spread spectrum system, especially in the 3-G (Generation Three mobile communication system), the technology that become spreading factor of using more, promptly use the spreading factor of different length, obtain preferable performance at different business, different user, different channel characteristics.
But conventional associated detection technique is all at the fixing situation of spreading factor.For the few system of the number that has number of users on the time, the technology of joint-detection has been practical, is the synchronous CDMA system under 16 the situation as spreading factor, and the application of associated detection technique has bigger improvement to systematic function.But when the user's who works simultaneously in same time slot spreading factor length was inequality, conventional method was just no longer suitable.
The objective of the invention is to propose a kind of united detection processing method that becomes under the spreading factor, it goes for the change spreading factor system under some situation, thereby improves the performance of system.
According to an aspect of the present invention, a kind of united detection processing method that becomes under the spreading factor is provided, wherein the spreading factor of Cai Yonging is pressed the tree generation, it is characterized in that: the tree of the sole user who uses the first short spreading factor according to the generation spreading factor, equivalence is for using a plurality of (a plurality of among the present invention the be meant two or more) user of the second long spreading factor, fix again joint-detection under the spreading factor is used the user's of first spreading factor demodulation result then according to a plurality of users' of described equivalence demodulation result reduction.
Preferably, described second spreading factor is positioned at the next stage adjacent with this first spreading factor on code tree.
Preferably, the length of described second spreading factor is identical with the length of scrambler in the system.
Preferably, adopt decision-feedback during joint-detection under doing described fixedly spreading factor and can set a threshold value,, do not carry out decision-feedback for the user data of absolute value less than threshold value.
Preferably, the described spreading factor that generates by tree is ovsf code (orthogonal variable frequency extension factor code).
Preferably, when the user's who uses first spreading factor according to a plurality of users' of described equivalence demodulation result reduction demodulation result, specifically comprise: each user after the equivalence is corresponding with a short sequence respectively, will lack described second spreading factor that promptly obtains the user's correspondence after this equivalence behind the sequence spread spectrum with described first spreading factor; The demodulating data of user after the equivalence be multiply by the pairing short sequence of this user, corresponding data addition that again will the pairing a plurality of short sequences of these a plurality of users, gained with sequence promptly as the user's of described use first spreading factor demodulation result.
Preferably, when the user's who uses first spreading factor according to a plurality of users' of described equivalence demodulation result reduction demodulation result, specifically comprise: each user after the equivalence is corresponding with a short sequence respectively, will lack described second spreading factor that promptly obtains the user's correspondence after this equivalence behind the sequence spread spectrum with described first spreading factor; In the user after the equivalence, the pairing described short sequence of that user of its demodulating data absolute value maximum multiply by this user's demodulating data, and the sequence of gained is as the user's of described use first spreading factor demodulation result.
A kind of united detection processing method that becomes under the spreading factor of the present invention goes for the change spreading factor system under some situation, and it can realize joint-detection simply in becoming the spreading factor system, thereby improves the performance of system.
For making the purpose, technical solutions and advantages of the present invention clearer, by the following examples, and in conjunction with the accompanying drawings, the present invention is described in more detail.Institute it should be understood that it only is used for elaboration of the present invention explanation and unrestricted.Wherein
Fig. 1 shows the code tree schematic diagram of the ovsf code that uses in the preferred embodiment of the present invention;
Fig. 2 shows the generation method of the ovsf code that uses in the preferred embodiment of Fig. 1;
Fig. 3 shows the schematic diagram that becomes united detection processing under the spreading factor in another preferred embodiment of the present invention;
Fig. 4 shows the schematic diagram of the ZF feedback joint-detection that adopts among the step D in the preferred embodiment of Fig. 3.
The present invention will use the user of short spreading factor equivalence be the user of the long spreading factor of a plurality of uses, do joint-detection again, and last a plurality of users' according to equivalence result reduces user's the demodulation result of short spreading factor.Its core concept is to be the user of the long spreading factor of a plurality of uses by the sole user's equivalence that will use short spreading factor, be converted into joint-detection problem under fixing spreading factor dexterously and will become joint-detection problem under the spreading factor, thereby can use associated detecting method and program under the conventional fixedly spreading factor, realize becoming the joint-detection under the spreading factor easily.
In present mobile communication system, especially in the 3-G (Generation Three mobile communication system), ovsf code is mostly selected in choosing of spreading code or channel code, and the generation of this yard generally generates according to the relation of the Hadamard matrix of different rank.On the basis of using ovsf code, add scrambler under many situations.Fig. 1 shows the code tree schematic diagram of the ovsf code that uses in the preferred embodiment of the present invention, and Fig. 2 shows the generation method of the ovsf code that uses in the preferred embodiment of Fig. 1.
Present embodiment is primarily aimed at the particular condition that becomes spreading factor: promptly have two class spreading factors in the system, the long spreading factor of the one class i.e. length of second spreading factor is N2, the short spreading factor of the one class i.e. first spreading factor length is N1, its short-and-medium spreading factor is adjacent with long spreading factor progression on code tree, for ovsf code, long spreading factor length is the twice of short spreading factor.Therefore if the spreading factor length of certain user A (N1) is N1, this user user (A that to be equivalent to two spreading factor length be N2 then
1(N2), A
2(N2)).
For the situation that contains shorter scrambler in the said system, the length that then also can get scrambler is N2, but the spreading factor length in the system can only be one or both length of selecting among N1, the N2.
Do joint-detection according to channel estimating of the number of users after the equivalence and corresponding spreading code and system or the like, the method for this joint-detection can adopt various algorithms commonly used such as ZF (ZF) algorithm, ZF-DF (ZF decision-feedback) algorithm or the like.Obtain the demodulating data of the user after the equivalence.Fixedly spreading factor joint-detection in this step is if use the decision-feedback technology, to the equivalent user (A of A (N1)
1(N2), A
2(N2)) demodulated data can be set a decision threshold when doing decision-feedback in, is made as 0 for absolute value less than the user data value of feedback of threshold value.
The demodulating data of user A (N1) before the equivalence is according to a plurality of user (A of its equivalence
1(N2), A
2(N2)) demodulation result obtains.Specific practice can be: with each the user A after the equivalence
i(N2) respectively with a short sequence (a
1, i, a
2, i) corresponding, this short sequence (a
1, i, a
2, i) obtain like this, promptly will lack described second spreading factor that promptly obtains the user's correspondence after this equivalence behind the sequence spread spectrum with described first spreading factor.With the user A after the equivalence
i(N2) demodulating data multiply by the pairing short sequence (a of this user
1, i, a
2, i), corresponding data addition that again will the pairing a plurality of short sequences of these a plurality of users, gained and sequence
Promptly as the demodulation result of the user A (N1) of described use first spreading factor.Another kind of according to a plurality of user (A after the equivalence
1(N2), A
2(N2)) way that demodulation result obtains the demodulating data of user A (N1) can be: get (A
1(N), A
2(N2)) that user A of demodulating data absolute value maximum in
k(N2) Dui Ying short sequence (a
1, k, a
2, k), multiply by this user's demodulating data, the sequence of gained is as the demodulation result of the user A (N1) of described use first spreading factor.
More concrete, in another preferred embodiment of the present invention, with reference to the TD-SCDMA system of CWTS (China Wireless Telecommunication Standar tissue) proposition, system is a structure of time slot with burst (burst), and spreading factor is 16 to the maximum, the number of users of co-frequency co-time slot is l6 to the maximum in certain sub-district, user's spreading factor can be 1,2,4,8,16.Adopt ovsf code to carry out spread spectrum, and scrambled code, the length of scrambler is 16, the QPSK modulation.When having plural user in the burst of system, use associated detection technique that user data is carried out demodulation.Present embodiment adopts the joint detection algorithm of ZF decision-feedback (ZF-DF).Be better explanation, supposing the system has 3 user C, B, and A, having spreading factor is 16,16,8, corresponding OVSF spreading code is ch
16,3, ch
16,4, ch
8,3The schematic flow sheet of entire process is seen Fig. 3.Fig. 3 shows the schematic diagram that becomes united detection processing under the spreading factor in another preferred embodiment of the present invention.
Because scrambler and maximum spreading factor are 16, so get the length N 2=16 of second spreading factor; Because the user less than N2 has only an A, the length N 1=8 of its spreading factor is so can be that (A1, A2), its corresponding spreading code is the generation tree according to ovsf code to 16/8=2 user, with ch with the A equivalence
8,3For tree root obtains corresponding spreading code ch
16,5, ch
16,6, original system can be regarded 2+2=4 user as and did joint-detection this moment, and spreading code is ch accordingly
16,3, ch
16,4, ch
16,5, ch
16,6, add scrambler after, obtain compound spreading code
, please refer to the 1O frame among Fig. 3.
At next step, channel is estimated to obtain A, B, C user's channel characteristics
, user A1 wherein, the channel characteristics of user A2 is with the channel characteristics of user A.Please refer to 20 frames among Fig. 3.
At next step, generate compound channel transfer matrix (being transmission matrix) by user characteristics after the equivalence and channel characteristics
。Please refer to 30 frames among Fig. 3.
Further, in 40 frames in Fig. 3, utilize the channel transfer matrix that obtains suddenly by previous step
Input and the fixing joint-detection under the spreading factor of the input that receives data.Fixedly the joint detection algorithm under the spreading factor can be referring to document [1], promptly, " Zero Forcing and MinimumMean-Square-Error Equalization for Multiuser Detection in Code-DivisionMultiple-Acess channels ", A.Klein G.K.KalehP.W.Basier, IEEE Trans.onVehicular Technology.Vol.45 no.2, l996, May.Fig. 4 shows the schematic diagram of the ZF feedback joint-detection that adopts among the step D in the preferred embodiment of Fig. 3.Wherein in decision-directed algorithm, to A1, A2, thresholding m of data setting, when the absolute value of its demodulating data during less than m, the value that feeds back to is made as 0, rather than the value of being adjudicated.
Please refer to 50 frames among Fig. 3, suddenly fixedly after the joint-detection of spreading factor, will export A1, A2, B, the demodulating data after four users' of C the joint-detection in previous step.This demodulating data will be handled in this step, reduction obtains using the data of the user A of first spreading factor, and user B, the data of C are directly exported and are got final product.
Utilize user A1, the demodulating data of the A2 also method of the demodulating data of original subscriber A can be: suppose user A1, certain data demodulates value of A2 is respectively b1, b2, then party A-subscriber's data can by be approximately equal to (b1+b2, b1-b2).The rest may be inferred can obtain all data of party A-subscriber.
Utilize user A1, the demodulating data of the A2 also method of the demodulating data of original subscriber A can also be: suppose A1, A2, certain data demodulates value be respectively b1, b2, then obtain | b1|, | the value of b2| maximum might as well be assumed to be | b2|, the channel code ch of A2 correspondence
16,6, can (be the short sequence described in the technical scheme) by (1 ,-1) through ch
8,3Spread spectrum obtains, thus the demodulating data that can obtain party A-subscriber's correspondence position for (b3 ,-b3).The rest may be inferred can obtain all data of party A-subscriber.
Claims (7)
1, a kind of united detection processing method that becomes under the spreading factor, wherein the spreading factor of Cai Yonging is pressed the tree generation, it is characterized in that: the tree of the sole user who uses first spreading factor according to the generation spreading factor, equivalence is for using a plurality of users of second spreading factor of being longer than this first spreading factor, fix again joint-detection under the spreading factor is used the user's of first spreading factor demodulation result then according to a plurality of users' of described equivalence demodulation result reduction.
2, the united detection processing method under the change spreading factor as claimed in claim 1, it is characterized in that: described second spreading factor is positioned at the next stage adjacent with this first spreading factor on code tree.
3, the united detection processing method under the change spreading factor as claimed in claim 1, it is characterized in that: the length of described second spreading factor is identical with the length of scrambler in the system.
4, the united detection processing method under the change spreading factor as claimed in claim 1, it is characterized in that: can adopt decision-feedback and can set a threshold value during joint-detection under doing described fixedly spreading factor, for the user data of demodulation value, do not carry out decision-feedback less than threshold value.
5, the united detection processing method under the change spreading factor as claimed in claim 1 is characterized in that: the described spreading factor that generates by tree is an orthogonal variable frequency extension factor code.
6, the united detection processing method under the change spreading factor as claimed in claim 1, it is characterized in that: when the user's who uses first spreading factor according to a plurality of users' of described equivalence demodulation result reduction demodulation result, specifically comprise: each user after the equivalence is corresponding with a short sequence respectively, will lack described second spreading factor that promptly obtains the user's correspondence after this equivalence behind the sequence spread spectrum with described first spreading factor; The demodulating data of user after the equivalence be multiply by the pairing short sequence of this user, corresponding data addition that again will the pairing a plurality of short sequences of these a plurality of users, gained with sequence promptly as the user's of described use first spreading factor demodulation result.
7, the united detection processing method under the change spreading factor as claimed in claim 1, it is characterized in that: when the user's who uses first spreading factor according to a plurality of users' of described equivalence demodulation result reduction demodulation result, specifically comprise: each user after the equivalence is corresponding with a short sequence respectively, will lack described second spreading factor that promptly obtains the user's correspondence after this equivalence behind the sequence spread spectrum with described first spreading factor; Among the user after equivalence, with the pairing described short sequence of that user of demodulating data absolute value maximum, multiply by this user's demodulating data, the sequence of gained is as the user's of described use first spreading factor demodulation result.
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| CN1961510B (en) * | 2004-06-08 | 2013-01-09 | 美商内数位科技公司 | Method and apparatus for reducing multi-user processing in wireless communication systems |
| CN101944931B (en) * | 2010-09-07 | 2012-05-23 | 华为技术有限公司 | Method and user equipment for obtaining orthogonal variable spreading factor codes |
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