Optimizing multi-user detection

Abstract

Multi-user detection (MUD) performance is optimized to eliminate redundant use of power during processing. An overbuilt A-matrix, i.e., a system response matrix, is provided. The overbuilt A-matrix uses all possible codes, e.g., all codes identified in a candidate code list (CCL) provided by blind code detection (BCD). The overbuilt A-matrix is passed to the MUD which extracts only those rows or columns required for codes that have actually been received, thus eliminating the need to recompute whitening matched filter (WMF) outputs that do not correspond to the actually received code.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 10 / 725,808 filed Dec. 2, 2003, which claims the benefit of U.S. Patent Application No. 60 / 452,162, filed Mar. 3, 2003, which are incorporated by reference as if fully set forth.FIELD OF INVENTION [0002] This invention generally relates to wireless communications, and more particularly, to joint detection in such systems. BACKGROUND [0003] Joint detectors, such as multi-user detectors (MUD), reduce the effect of multiple access interference, and hence increase the system capacity. A MUD cancels intra-cell interference and the system capacity is determined by the efficiency of the MUD algorithm and the intercell interference. In addition to capacity improvement, MUD alleviates the near / far problem typical to direct sequence—code division multiple access (DS-CDMA) systems. [0004] Conventional MUD algorithms extract all codes from a system response matrix (i.e., the A-ma...

AI Technical Summary

Benefits of technology

The invention provides a method and system for identifying which codes have been received in a given time slot and eliminating redundant calculations when performing MUD, BCD, and / or DTX related processing. This is done by constructing an A-matrix using a list of possible codes and channel responses associated with their codes, and computing soft symbol estimates for the first N symbols of each code. The identities of received codes are determined based on the N soft symbol estimates, which are then used by a MUD to extract user data. Codes in the A-matrix that are not received are marked as invalid. The method and system improve efficiency and accuracy in wireless communication.

Problems solved by technology

This is a substantial waste of computation power and it increases the system delay.

More particularly, calculations in support of blind code detection (BCD) and discontinuous transmission (DTX) involve processing that uses power and may require redundant circuitry or software.

Even so, the MUD represents a large portion of receiver processing and also causes delay in the received signal path.

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