Reduced computation in joint detection

Details Reduced computation in joint detection Reduced computation in joint detection

2000-09-14

2004-12-14

Tse, Young T. (Department: 2637)

Pulse or digital communications

Spread spectrum

Direct sequence

C375S152000, C370S335000

Reexamination Certificate

active

06831944

ABSTRACT:

BACKGROUND
The invention generally relates to wireless communication systems. In particular, the invention relates to joint detection of multiple user signals 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
which communicate with user equipments (UEs)
14
1
to
14
3
. Each base station
12
1
has an associated operational area where it communicates with UEs
14
1
to
14
3
in its operational area.
In some communication systems, such as code division multiple access (CDMA) and time division duplex using code division multiple access (TDD/CDMA), multiple communications are sent over the same frequency spectrum. These communications are typically differentiated by their chip code sequences. To more efficiently use the frequency spectrum, TDD/CDMA communication systems use repeating frames divided into time slots for communication. A communication sent in such a system will have one or multiple associated chip codes and time slots assigned to it based on the communication's bandwidth.
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 single user detection. In single user detection, a receiver detects only the communication from a desired transmitter using a code associated with the desired transmitter, and treats signals of other transmitters as interference.
In some situations, it is desirable to be able to detect multiple communications simultaneously in order to improve performance. Detecting multiple communications simultaneously is referred to as joint detection. Some joint detectors use Cholesky decomposition to perform a minimum mean square error (MMSE) detection and zero-forcing block equalizers (ZF-BLEs). These detectors have a high complexity requiring extensive receiver resources.
Accordingly, it is desirable to have alternate approaches to joint detection.
SUMMARY
A plurality of transmitted data signals are received at a receiver. The receiver measures a channel response associated with the transmitted data signals. A system response is determined. The system response is expanded to be piecewise orthogonal. The received data signals data is retrieved based on in part the expanded system response.


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