초록 ▼

A method and an apparatus for demodulating trellis coded direct sequence spread spectrum communication signals are provided. A transmitted QPSK signal is received. Binary phase-shift keyed (BPSK) despreading is performed on the QPSK signal. The BPSK despreading includes correlating the in-phase and

A method and an apparatus for demodulating trellis coded direct sequence spread spectrum communication signals are provided. A transmitted QPSK signal is received. Binary phase-shift keyed (BPSK) despreading is performed on the QPSK signal. The BPSK despreading includes correlating the in-phase and the quadrature components of the received QPSK signal with independent PN sequences for the each of the in-phase and the quadrature components. The despread signal is then demultiplexed, and the pilot signal and the BPSK data signal are recovered. The recovered pilot signal is used to provide a channel phase estimate and a channel magnitude estimate. The recovered BPSK data signal is demodulated, despread, and decoded. The despreading and decoding includes determining a number of cross-correlation terms of the received signal using a number of transmitted biorthogonal Walsh sequences. The cross-correlation terms are used as the branch metrics in a maximum likelihood decoding algorithm. The branch metrics may be computed with a Fast Walsh Transform scaled in response to the channel phase estimate from the recovered pilot signal. The maximum likelihood decoding algorithm may be a Viterbi algorithm in which the optimum path is the path with the maximum accumulated branch metric. The decoding algorithm recovers and outputs a transmitted data bit sequence.

대표청구항 ▼

[ What is claimed is:] [1.] A method for spread spectrum communication, the method comprising the steps of:performing binary phase-shift keyed (BPSK) despreading on a received quadrature phase-shift keyed (QPSK) signal;demultiplexing the despread signal to form a BPSK data signal; andrecovering a pi

[ What is claimed is:] [1.] A method for spread spectrum communication, the method comprising the steps of:performing binary phase-shift keyed (BPSK) despreading on a received quadrature phase-shift keyed (QPSK) signal;demultiplexing the despread signal to form a BPSK data signal; andrecovering a pilot signal from the BPSK data signal.