Patent ID: 7639758
Filing Date: 2009-12-29
Classification: H04B,H04L

Abstract:
1. A method for a blind detection of BPSK signals in a multi-user environment with multiple simultaneous transmitters, comprising: precoding uniquely for each user of the BPSK symbols at a transmitter, the precoding being achieved by using a phase rotation of the BPSK symbols at the transmitter for detection of a desired user's signals in an unknown multi-path channel, dividing data to be transmitted by each user into blocks of N-symbols, assigning to each user a unique random binary (+1, −1) precoding sequence of length N, multiplying each binary symbol in the data block of each user by a factor of either j=√{square root over ( )}−1 or 1 depending upon whether the corresponding bit in the precoding sequence is +1 or −1, thereby obtaining a QPSK-like signal, multiplying by an inverse of the user's precoding sequence at a receiver to detect the desired user's signal, and detecting at the receiver the precoded symbols of the desired user by forcing a zero response for interfering signals while producing a fixed or large response for the desired signal based on the desired user's symbols being real and the symbols of the interference being complex.