A method and apparatus for direct sequence spread spectrum communication having
low complexity. In the transmitter, the data bit is spreaded by a code sequence,
a reference code is interleaved with the code sequence, and together they are transmitted
by the transmitter. The corresponding receiver recovers the data signal from the
received signal by transforming the received signal to a complex base band signal
and differentially decoding the base band signal at the chip level. The spreaded
signal is despreaded by the chip-level differential operation, thus eliminating
the decorrelation operation, and so significantly reducing the cost of the overall
system. Furthermore, this system is very robust to any carrier frequency drift
since the chip-level differential operation is used, thus releasing the reference
clock or crystal requirements, and so further reducing the cost of the system.