Performance of multi-carrier CDMA with MSK modulation and one-bit differential detection in a multi-path fading channel

Abstract

A direct sequence code division multiple access (DS-CDMA) multi-carrier system with minimum-shift-keying (MSK) modulation is proposed. Transmitted data bits are serial to parallel converted into M parallel streams. The bits on each stream are transmitted on S carriers with successively non-overlapping spectra using MSK modulation. Then the modulated streams are spread by a pseudo random (PN) code with a suitable chip rate. The resulting signal will have overlapping spectra. It is shown that the condition of single path fading for each carrier can be achieved by increasing the number of carriers and the separation between successive carriers. Also frequency diversity is achievable for the same bit transmitted on different carriers. The system is analyzed with one-bit differential detector in a static Rayleigh-fading multi-path channel. A simple formula for the probability of error is derived. MSK with one-bit differential detector has the advantage of simpler implementation than BPSK with CMF since the exact frequency and phase of the carrier are not required in the differential detector.