US 7,248,623 B2 · Wireless communications systems and methods for short-code multiple user detection

Abstract

The invention provides methods and apparatus for multiple user detection (MUD) processing that have application, for example, in improving the capacity CDMA and other wireless base stations. One aspect of the invention provides a multiprocessor, multiuser detection system for detecting user transmitted symbols in CDMA short-code spectrum waveforms. A first processing element generates a matrix (hereinafter, “gamma matrix”) that represents a correlation between a short-code associated with one user and those associated with one or more other users. A set of second processing elements generates, e.g., from the gamma matrix, a matrix (hereinafter, “R-matrix”) that represents cross-correlations among user waveforms based on their amplitudes and time lags. A third processing element produces estimates of the user transmitted symbols as a function of the R-matrix.

Claims19

Dependent claims

A method of processing short code spread spectrum waveforms transmitted by one or more users of a spread spectrum system, comprising

generating a matrix indicative of cross correlations among the waveforms as a composition of a first component that represents correlations among time lags and short codes associated with the waveforms transmitted by the users and a second component that represents correlations among multipath signal amplitudes associated with the waveforms transmitted by the users,
generating, as a function of the correlation matrix, detection statistics corresponding to symbols generated by the users and encoded in the waveforms, and generating estimates of the symbols based on the detection statistics,
wherein the first component is updated on a time scale commensurate with a rate of change of the time lags associated with the waveforms transmitted by the users and the second component is updated on a time scale commensurate with a rate of change of the multipath amplitudes associated with waveforms transmitted by the users.

A method of processing short code spread spectrum waveforms transmitted by one or more users of a spread spectrum system, comprising

generating a matrix indicative of cross correlations among the waveforms as a composition of a first component that represents correlations among time lags and short codes associated with the waveforms transmitted by the users and a second component that represents correlations among multipath signal amplitudes associated with the waveforms transmitted by the users,
generating estimates of symbols transmitted by the users and encoded in said waveforms as a function of the cross-correlation matrix,
wherein the correlations among the short codes associated with the waveforms transmitted by the users are defined in accord with by the relation:
Γ
ik
⁡
[
m
]
≡
1
2
⁢
N
l
⁢
∑
n
=
0
N
-
1
⁢
c
l
*
·
c
k
⁡
[
n
-
m
]
wherein
Γlk[m] represents correlation between l and k users corresponding to mth transmitted symbol,
cl*[n] represents complex conjugate of the short code sequence associated with the lth user,
ck[n−m] represents the short code sequence associated with kth user,
m is a symbol period,
N represents the length of the code, and
Nl represent the number of non-zero length of the code,
wherein the step of estimating the symbols further comprises generating, as a function of the correlation matrix, detection statistics corresponding to symbols generated by the users and encoded in the waveforms, and
wherein the step of estimating the symbols comprises utilizing the detection statistics to estimate the symbols
wherein the first component of the cross-correlation matrix is defined in accord with the relation:
C
lkqq
·
[
m
]
=
∑
m
⁢
g
⁡
[
mN
c
+
τ
]
·
Γ
lk
⁡
[
m
]
wherein
g is a pulse shape vector,
Nc is the number of samples per chip,
τ is a time lag, and
Γ represents the Γ matrix defined above.

73 more elements

Dependencies are inferred from the claim text.

Wireless communications systems and methods for short-code multiple user detection

Life of this patent

Wireless communications systems and methods for short-code multiple user detection

Life of this patent

Abstract

Claims19