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 .