Patent Document ID: 20020122392
Application ID: 09957339
Patent Flag: 0

Claim One:
1. A method for demodulating a multiuser signal using a subtractive interference cancellation (IC) detector and single-user decoders for a convolutionally-encoded code-division multiple-access (CDMA) system, the method comprising: (a) receiving a signal containing information for a plurality of users in a convolutionally encoded CDMA system employing spreading sequences that span a plurality of symbol periods; (b) despreading the received signal using a signature sequence for each user to produce individual user signals having multiple-access interference (MAI); (c) determining tentative bit estimates for each of the individual user signals; (d) applying subtractive interference cancellation (IC) to each of the individual user received signals based on the tentative bit estimates to remove the MAI from the individual user signals and thereby producing individual user signals containing residual multiple-access interference (RMAI); and (e) decoding each of the individual user signals after the subtractive IC using a Viterbi decoder with a branch metric that accounts for the time-dependence of the variance of the RMAI in the individual user signals based on a model of the RMAI.