CN1141796C - Real-time decorrelation receiver - Google Patents
Real-time decorrelation receiver Download PDFInfo
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- CN1141796C CN1141796C CNB001190091A CN00119009A CN1141796C CN 1141796 C CN1141796 C CN 1141796C CN B001190091 A CNB001190091 A CN B001190091A CN 00119009 A CN00119009 A CN 00119009A CN 1141796 C CN1141796 C CN 1141796C
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Abstract
The present invention provides a new real-time decorrelation receiver. The present invention is characterized in that a spread spectrum code generator module which only carries out decorrelation processing to interference generated by the current data of other users is corrected, namely that only equivalent interference spread spectrum codes generated by data sent by every user in current time are fetched to calculate orthogonal vectors, and an interference counteracter module is added finally and utilizes a decorrelation result of every user in preceding time to counteract the data interference of other users in the preceding time. The present invention not only decreases a constraint number to be met by the decorrelation receiver and enormously reduces needed amount of calculation, but can completely counteract the interference caused by other users through real-time processing.
Description
Technical field:
The invention belongs to code division multiple access (CDMA) mobile communication technology field, particularly relate to the method for reseptance and the receiver that are used for asynchronous cdma system.
Background technology:
Code division multiple access (CDMA) spread spectrum communication system is a kind of rapidly multi-access mode of development in recent years, and occupies an important position in 3-G (Generation Three mobile communication system).Cdma system has the ability of good anti-fading and multipath, and power system capacity is big.In cdma system, all users take identical frequency band jointly, distinguish with different code words between each user, separate transmission, therefore the signal of different user is asynchronous at receiving terminal, brings the non-orthogonal of code word between each user thus, and cross correlation value is non-vanishing even quite big.When each subscriber signal power of receiving was unequal, the high power signal was very serious to the interference of weak power signal, forms so-called near-far interference.
Existing conventional receiver adopts matched filter to add the method demodulation of decision device, and this method has also obtained the energy that each multiple access disturbs when acquisition is waited to separate signal energy.But this method is disturbed multiple access and is regarded white Gaussian noise simply as and handle, and in fact the character of these two kinds of interference is distinct, and such simplification is handled and made power system capacity be subjected to the very big restriction that multiple access disturbs.
The scheme of existing Multiuser Detection, as " international electronics communicate by letter journal " (IEEETrans.Commun. with The Institution of Electrical Engineers, vol.COM-38, pp.496-508, Apr.1990) scheme of described Multiuser Detection, because need handling all reception data of whole communication process, it could eliminate other users' interference fully, so be difficult to practicality.
Another kind of " Multiuser Detection " book (the Multiuser Detection that publishes as the U.S., Sergio Verdu, pp.246-248, Cambridge University Press, 1998) described, can export the real-time decorrelation receiver of user's current sign court verdict in real time, though only need handle the received signal of current time is the exportable restituted signal that not disturbed by other user, but this method requires all correction spreading codes of while quadrature of an interference vector that the specific user is formed with the data in other previous moment of all users and this data constantly, when user's number is bigger, owing to need satisfied constraint too many, this correlation of revising spreading code and original spreading code becomes very poor, causes the decline of systematic function; On the other hand, find the solution corresponding to the required amount of calculation of a user's vector greatly about O (N
2) to O (N
3) between, wherein N is the number of the constraint that will satisfy, and this method is because the constraint that will satisfy is too many, and solution procedure can consume more time.
Summary of the invention:
The invention provides a kind of new real-time decorrelation receiver, can reduce the constraint number that decorrelation receiver will satisfy, reduce required amount of calculation greatly, can offset the interference that other users cause fully by real-time processing again simultaneously.
This real-time decorrelation receiver obtains received signal 1 specific user's decorrelation result 3 by each user's decorrelation processing module structure 2;
Described each user's decorrelation processing module structure 2 comprises and revises spectrum-spreading code generator module 4, multiplier 6 and integrator 7; This revises the correction spreading code 5 of the equivalence interference spreading code quadrature that spectrum-spreading code generator module 4 produces and the transmission data of other user's current times form, the equivalence that the transmission data of described other user's current times form disturbs spreading code to adopt following method to constitute: the part of the time period of place as a result that the result of the transmission data band spectrum modulation of each interference user current time is dropped on the transmission data band spectrum modulation of specific user's current time intercepts, and added for zero time period at place as a result that expands to the transmission data band spectrum modulation of whole specific user's current time, obtain the equivalence that the transmission data of each interference user current time form and disturb spreading code; Spreading code is disturbed in the equivalence that in like manner can obtain the transmission data formation in each previous moment of interference user; Described integrator module 7 is carried out integration with received signal 1 and product corresponding to specific user's correction spreading code 5 in the time corresponding to specific user's a symbol, and output correlated results 8;
It is characterized in that:
The processing of decorrelation is carried out in the interference that described correction spectrum-spreading code generator module 4 only produces other user's current datas, and in the end increased interference offset device module 11, the interference that utilizes the decorrelation result 3 in the previous moment of each user that feeds back to offset the previous moment data of other users.
Described received signal 1 in multiplier 6 and integrator module 7 with the correction spreading code 5 of revising 4 outputs of spectrum-spreading code generator module carry out relevant, decorrelation result 8; The decorrelation result 3 in the previous moment of other users with revise the interference coefficient 9 that spectrum-spreading code generator module 4 produces and multiply each other, obtain the interference components 10 that 3 pairs of correlated results 8 of decorrelation result in the previous moment of other users cause; Interference offset device module 11 deducts interference components 10 from correlated results 8, export the decorrelation result 3 of current time at last;
This correction spectrum-spreading code generator module 4 is onlyed demand the correction spreading code 5 that the spreading code quadrature is disturbed in the equivalence that forms with the transmission data of each interference user current time; Obtain revising after the spreading code 5, choosing the equivalence of the transmission data formation in each previous moment of interference user again disturbs spreading code to constitute the individual interference spreading code of another group (number of users-1), then, carry out relevantly respectively with the individual interference spreading code of the specific user's who tries to achieve previously correction spreading code 5 and this (number of users-1), obtain other users respectively and send the interference coefficient 9 of data the previous moment this specific user's correction spreading code 5 with spreading code appearance etc.;
Described interference offset device module 11 deducts the interference components 10 that decorrelation result 3 and these users in other users' the previous moment are multiplied each other and obtained respectively the interference coefficient 9 of this specific user's correction spreading code 5 in multiplier 6 from the correlated results 8 of integrator module 7 output, as decorrelation result 3 outputs of specific user's current time.
Disturb spreading code to constitute interference space because real-time decorrelation receiver of the present invention has only been chosen the equivalence that the transmission data of each interference user current time form in revising spectrum-spreading code generator module 4, thereby make the constraints of this real-time decorrelation receiver requirement have only half of existing real-time decorrelation receiver.The benefit of bringing like this is many-sided; Because the minimizing of constraints, require to revise the linear space of spreading code 5 quadratures also along with reducing with the specific user, this makes that correction spreading code 5 is more approaching with original spreading code, it is bigger that thereby the specific user revises the vector length of spreading code 5, correspondingly have bigger spreading gain, this can bring more performance for system; On the other hand because constraints reduces, in revising spectrum-spreading code generator module 4, ask specific user's correction spreading code 5 in, required amount of calculation also reduces thereupon, is under the situation of N in the number of vector, asks amount of calculation with this N vectorial quadrature at O (N
2) to O (N
3) between, in this real-time decorrelation receiver, the quantity of constraints has reduced half than former rice, thus amount of calculation reduces to original 1/8 to 1/4; On the other hand, the equivalence that the transmission data of each interference user current time form disturbs the interference of spreading code to be offset by the interference offset device module 11 of back, thereby has eliminated the interference that multi-user environment brings fully.
Description of drawings:
Accompanying drawing 1 is the structural principle schematic diagram of real-time decorrelation receiver of the present invention;
Accompanying drawing 2 is the error rate-signal to noise ratio analog result of receiver under 10 user situations.
Embodiment:
Below in conjunction with the description of drawings embodiments of the invention.
Embodiment 1:
Suppose that number of users is K, module 2 is the decorrelation processing module structure at unique user, signal 1 is the received signal of input decorrelation processing module structure 2, from the signal 3 of decorrelation processing module structure 2 outputs is the output of each user's decorrelation, be sent to back level and do next step processing, deliver to processing module structure 2 at other users simultaneously to offset the interference that these data cause.
In decorrelation processing module structure 2, module 4 is for revising spectrum-spreading code generator; Signal 5 is for revising the correction spreading code that spectrum-spreading code generator produces; Module 6 is a multiplier; Module 7 is an integrator; Signal 8 carries out relevant result for input signal 1 with correction spreading code 5; The data that other users that signal 9 produces for correction spectrum-spreading code generator 4 send in the previous moment are to the interference coefficient of signal 8; The data that signal 10 sends for other users in the previous moment are to the correlated results 8 actual interference components that cause; Module 11 is an interference offset device, and it is made of subtracter.
Revising spectrum-spreading code generator 4 adopts the method described in " Multiuser Detection " book to constitute the equivalence interference spreading code of the transmission data formation of other user's current times, try to achieve correction spreading code then as follows: at first use Si Mite (Gram-Schmidt) orthogonalization method to obtain one group of orthogonal basis of the linear space that number of users-1 and the interference spreading code of spreading code appearance etc. open at each specific user, the component of the spreading code of asking the specific user again and this group orthogonal basis (the also linear space of promptly opening with number of users-1 and the interference spreading code of spreading code appearance etc.) quadrature, and with its correction spread-spectrum code signals 5 as the specific user; Spreading code is disturbed in the equivalence that the transmission data that adopt the method described in " Multiuser Detection " book to constitute the previous moment of other users again form, and these equivalences are disturbed spreading codes and revise spreading code 5 and carry out relevantly, obtain revising the interference coefficient 9 of the data of the previous moment transmission of other users that spreading code takes place respectively to correlated results 8.
If there are 10 users to send information simultaneously in this example, revise the correction spread-spectrum code signals 5 that requires to disturb the spreading code quadrature in the spectrum-spreading code generator 4 with 9 equivalences, handle required multiplication number of times 9 with Si Mite (Gram-Schmidt) orthogonalization method
2=81 to 9
3Between=729, and in the prior art, require to disturb with 19 equivalences a vector of spreading code quadrature, the multiplication number of times that requires with Si Mite (Gram-Schmidt) orthogonalization method is 19
2=361 to 19
3Between=6859, this shows that the required amount of calculation of real-time decorrelation receiver of the present invention greatly reduces.
In the performance simulation below, choose 10 length and be 31 frequency expansion sequence (Gold sequence), each user's time delay picked at random, and other 9 users' signal amplitude is 10 times of first subscriber signal amplitude.Accompanying drawing 2 has provided the analog result of a user under other 9 users' disturbed condition, and curve is the error rate-signal to noise ratio curve of this user among the figure, and wherein ordinate is the error rate (BER1), and abscissa is signal to noise ratio (SNR1), and it is defined as: SNR
1=10logA
1/ σ, wherein A
1Be user's 1 signal amplitude, σ
2Power for additive white Gaussian noise.Solid line is the curve under single user situation among the figure, and pecked line is for adopting the curve under traditional matched filter receiver situation, and dotted line is for adopting the curve under this real-time decorrelation receiver situation.As we can see from the figure, along with the increase of Signal-to-Noise, adopt the also corresponding reduction of the error rate under this real-time decorrelation receiver situation, and the error rate of adopting under traditional matched filter receiver situation remains unchanged substantially.This shows that this real-time decorrelation receiver can be removed the interference that other interference user causes, and has reasonable anti-multiple access interference capability.
Claims (1)
1, a kind of real-time decorrelation receiver obtains received signal 1 specific user's decorrelation result 3 by each user's decorrelation processing module structure 2;
Described each user's decorrelation processing module structure 2 comprises and revises spectrum-spreading code generator module 4, multiplier 6 and integrator 7; This revises the correction spreading code 5 of the equivalence interference spreading code quadrature that spectrum-spreading code generator module 4 produces and the transmission data of other user's current times form, the equivalence that the transmission data of described other user's current times form disturbs spreading code to adopt following method to constitute: the part of the time period of place as a result that the result of the transmission data band spectrum modulation of each interference user current time is dropped on the transmission data band spectrum modulation of specific user's current time intercepts, and added for zero time period at place as a result that expands to the transmission data band spectrum modulation of whole specific user's current time, obtain the equivalence that the transmission data of each interference user current time form and disturb spreading code; Spreading code is disturbed in the equivalence that in like manner can obtain the transmission data formation in each previous moment of interference user; Described integrator module 7 is carried out integration with received signal 1 and product corresponding to specific user's correction spreading code 5 in the time corresponding to specific user's a symbol, and output correlated results 8;
It is characterized in that:
The processing of decorrelation is carried out in the interference that described correction spectrum-spreading code generator module 4 only produces other user's current datas, and in the end increased interference offset device module 11, the interference that utilizes the decorrelation result 3 in the previous moment of each user that feeds back to offset the previous moment data of other users.
Described received signal 1 in multiplier 6 and integrator module 7 with the correction spreading code 5 of revising 4 outputs of spectrum-spreading code generator module carry out relevant, decorrelation result 8; The decorrelation result 3 in the previous moment of other users with revise the interference coefficient 9 that spectrum-spreading code generator module 4 produces and multiply each other, obtain the interference components 10 that 3 pairs of correlated results 8 of decorrelation result in the previous moment of other users cause; Interference offset device module 11 deducts interference components 10 from correlated results 8, export the decorrelation result 3 of current time at last;
This correction spectrum-spreading code generator module 4 is onlyed demand the correction spreading code 5 that the spreading code quadrature is disturbed in the equivalence that forms with the transmission data of each interference user current time; Obtain revising after the spreading code 5, choosing the equivalence of the transmission data formation in each previous moment of interference user again disturbs spreading code to constitute the individual interference spreading code of another group (number of users-1), then, carry out relevantly respectively with the individual interference spreading code of the specific user's who tries to achieve previously correction spreading code 5 and this (number of users-1), obtain other users respectively and send the interference coefficient 9 of data the previous moment this specific user's correction spreading code 5 with spreading code appearance etc.;
Described interference offset device module 11 deducts the interference components 10 that decorrelation result 3 and these users in other users' the previous moment are multiplied each other and obtained respectively the interference coefficient 9 of this specific user's correction spreading code 5 in multiplier 6 from the correlated results 8 of integrator module 7 output, as decorrelation result 3 outputs of specific user's current time.
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