A spread-spectrum system employing permutation modulation

In satellite communications, spread-spectrum techniques offer several advantages because they have the inherent capability of reducing multiple fading and intra-system as well as inter-system interference. Spread-spectrum techniques also permit easy multiple access in the form of CDMA. The authors propose applying permutation modulation to direct-sequence (DS) CDMA systems. The performance of DS-CDMA employing multitone FSK (MT-FSK) permutation modulation technique is evaluated over AWGN and fading channels. FEC coding is also considered. By using orthogonal PN codes, the implementation complexity can be greatly reduced.