Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2001-12-31
2003-09-23
Vo, Don N. (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C370S342000
Reexamination Certificate
active
06625203
ABSTRACT:
BACKGROUND
The invention generally relates to wireless communication systems. In particular, the invention relates to data detection in a wireless communication system.
FIG. 1
is an illustration of a wireless communication system
10
. The communication system
10
has base stations
12
1
, to
12
5
(
12
) which communicate with user equipments (UEs)
14
1
to
14
3
(
14
). Each base station
12
has an associated operational area, where it communicates with UEs
14
in its operational area.
In some communication systems, such as frequency division duplex using code division multiple access (FDD/CDMA) and time division duplex using code division multiple access (TDD/CDMA), multiple communications are sent over the same frequency spectrum. These communications are differentiated by their channelization codes. To more efficiently use the frequency spectrum, TDD/CDMA communication systems use repeating frames divided into timeslots for communication. A communication sent in such a system will have one or multiple associated codes and timeslots assigned to it.
Since multiple communications may be sent in the same frequency spectrum and at the same time, a receiver in such a system must distinguish between the multiple communications. One approach to detecting such signals is multiuser detection (MUD). In MUD, signals associated with all the UEs
14
, users, are detected simultaneously. Another approach to detecting a multi-code transmission from a single transmitter is single user detection (SUD). In SUD, to recover data from the multi-code transmission at the receiver, the received signal is passed through an equalization stage and despread using one or multiple codes. Approaches for implementing MUD and the equalization stage of SUD include using a Cholesky or an approximate Cholesky decomposition. These approaches have a high complexity. The high complexity leads to increased power consumption, which at the UE
14
results in reduced battery life. Accordingly, it is desirable to have alternate approaches to detecting received data.
SUMMARY
K data signals are transmitted over a shared spectrum in a code division multiple access communication system. A combined signal is received and sampled over the shared spectrum. The combined signal has the K transmitted data signals. A combined channel response matrix is produced using the codes and impulse responses of the K transmitted data signals. A block column of a combined channel correlation matrix is determined using the combined channel response matrix. Each block entry of the block column is a K by K matrix. At each frequency point k, a K by K matrix &Lgr;
(k)
is determined by taking the fourier transform of the block entries of the block column. An inverse of &Lgr;
(k)
is multiplied to a result of the fourier transform. Alternately, forward and backward substitution can be used to solve the system. An inverse fourier transform is used to recover the data from the K data signals.
REFERENCES:
patent: 6144711 (2000-11-01), Raleigh et al.
patent: 6208295 (2001-03-01), Dogan et al.
patent: 6252540 (2001-06-01), Hale et al.
patent: 6370129 (2002-04-01), Huang
De Parthapratim
Pan Jung-Lin
Zeira Ariela
InterDigital Technology Corporation
Nguyen Dong X.
Vo Don N.
Volpe and Koenig P.C.
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