Patent Number: 6,426,973

Title: Differential minimum mean squared error communication signal compensationmethod

Abstract: This invention reformulates the MMSE criterion to apply to systems in whichthe desired data to be tracked is the ratio of the data appearing insuccessive observation intervals. The resulting differential MMSEcriterion leads to a number of novel algorithms for adaptiveimplementation of the MMSE receiver. Applications include equalization forsingle user systems, and multiuser detection, or interference suppression,for direct sequence CDMA with short spreading sequences (i.e., the periodof the spreading sequence equals the symbol interval). The invention alsoprovides blind (i.e., without the requirement of a training symbolsequence for the user of interest) equalization and beamforming (using areceive antenna array) for direct sequence CDMA systems with longspreading sequences (i.e., systems in which the spreading sequences areaperiodic, or have period much larger than the symbol interval). Theinvention enables recovery of the desired symbol sequence up to an unknownphase. The invention is therefore well suited to the demodulation ofdifferentially modulated data, in which information is encoded in thephase differences of successive transmitted symbols. Assuming that thechannel amplitude and phase is approximately constant over two successivesymbol intervals, the demodulator can use the differences in phases of twosuccessive received symbols to recover differentially encoded data. Theinvention may also be used in conjunction with a separate phase recoverymethod to demodulate data without differential modulation.

Inventors: Madhow; Upamanyu (Urbana, IL), Zhu; Liping Julia (San Jose, CA), Galup; Luis (Niskayuna, NY)


International Classification: H04B 7/08 (20060101); H04B 1/707 (20060101); H04L 25/03 (20060101); H03H 007/30 (); H03H 007/40 (); H03K 005/159 ()

Expiration Date: 07/30/2014