Method of using long cellized codes in a joint detection system
View Patent ↗The invention discloses a method of applying a long cell-code in a joint detection system. At transmitters, multiples of the spreading code (spreading factor) is taken as the length of the long cell-code to scramble the signal, and at receivers, the method still takes the multiuser detection to process the received signal. The method includes that: for every antenna unit, making channel estimation to obtain a channel estimation result of each antenna unit; generating a first mid-matrix of the received data of each antenna unit that relates to selected length of said long cell-code and the channel estimation result; based on the first mid-matrix, generating a second mid-matrix and its associate matrix, and then based on said generated second mid-matrix and its associate matrix, generating a third mid-matrix; making Cholesky decomposition of said third mid-matrix, wherein the number of decomposition order relates to the length of said long cell-code; making demodulation processing based on said Cholesky decomposition result and said received signals of all antenna units having been matching filtered. The whole computation loads of the method are acceptable.
1. A demodulation method in a joint detection system where a long cell-code is applied, comprising,
A. making a channel estimation by a receiver for midamble code part of a signal received by every antenna unit, to obtain a channel estimation result of each antenna unit;
B. calculating a first mid-matrix of the received signal of each antenna unit; wherein the first mid-matrix relates to length of the long cell-code and the channel estimation result of each antenna unit, length of the long cell-code is multiples of 16;
C. based on the first mid-matrix of the received signal of each antenna unit, calculating a second mid-matrix and its associate matrix; and then based on the second mid-matrix and its associate matrix, calculating a third mid-matrix, which is a symmetric definite matrix;
D. making Cholesky decomposition for the third mid-matrix, wherein the number of decomposition order relates to the length of long cell-code;
E. matched filtering the received signals of all antenna units, and then making demodulation calculation based on the Cholesky decomposition result of the third mid-matrix and the matching filtered received signals.
2. The method according to the claim 1 , wherein Step A comprises,
calculating channel estimation result h k a of the k a th antenna unit with the following formula:
h (k a ) =IDFT ( G −1 ·DFT ( e m (k a ) )), k a =0 . . . K a −1,
where e m is the midamble code of the received signal; k a is one of the total K a antenna units and takes value 0 to K a −1; G −1 is the inverse matrix of the correlation matrix of a midamble code; and h is a channel estimation result;
Step B comprises,
B1. dividing the long cell-code L by 16 to obtain M=L/16 sections; making dot product with the WALSH code for each section, respectively, and then multiplying with a corresponding value j, which is a angle transform based on communication standard, to obtain M vectors c m , the length of c m is 16, and m is from 1 to M;
B2. computing each column of a matrix in the first mid-matrix A Ka with the formula b m (k a ,k vru ) = h (k a ,k vru ) {circle around (×)} c m (k vru ) , to obtain M matrixes B ka 1 , B ka 2 . . . B ka M ; forming the first mid-matrix with repeating the obtained M matrixes in a diagonal direction of the first mid-matrix, wherein k vru is one of the total K vru code channels occupied by the subscriber and takes value from 0 to K vru −1, and, each of matrixes is constituted of M columns;
Step C comprises,
C1. calculating the second mid-matrix A according to K a results of first mid-matrix, and then calculating the associate matrix A′ of the second mid-matrix A:
A
=
[
A
k
1
A
k
2
A
k
3
⋮
A
K
a
]
;
C2. Obtaining the third mid-matrix R from the formula R =A′A,
R
=
[
R
0
1
R
1
1
R
1
1
R
0
2
R
1
1
R
1
2
R
0
3
R
0
M
R
1
M
R
1
M
R
0
1
R
1
1
R
1
1
]
;
Step D comprises,
making Cholesky decomposition according to the formula: R =H T H,
wherein, in case of the length of the long cell-code being three or more than three multiple of 16, the decomposed result matrix H is:
H
=
[
H
1
H
2
H
3
H
4
H
5
H
6
H
41
H
42
H
43
H
44
]
;
where H 1 , H 3 , H 5 , . . . , H 43 are 16×16 triangle matrixes, and H 2 , H 4 , H 6 . . . H 44 are 16×16 matrixes, all other elements of the H matrix are zero.
3. The method according to the claim 1 , wherein matched filtering the received signals of all antenna units in Step E comprises, calculating the received signal of all antenna units except the midamble code through formula: e MF =A′×e, where e MF is the received signal of all antenna units except the midamble code; e is the received signal of all antenna units, and A′ is the associate matrix of second mid-matrix.