Unequal error protection for digital mobile DS-CDMA radio systems

Unequal error protection (UEP) is investigated for coded direct-sequence code-division multiple access (DS-CDMA) mobile radio systems. The UEP techniques considered include (i) different channel code rates, (ii) different number of chips/symbol, and (iii) different symbol energies. Analytical approximations of the bit error rate (BER) in correlated Rayleigh fading are presented taking carrier phase synchronization into account. Binary PSK modulation with pilot-symbol-aided coherent detection and binary DPSK modulation with differential detection are considered. Both schemes are candidates for an asynchronous up-link, which is the critical link. Technique (i) has advantages in fast fading, otherwise technique (ii) is recommended. Technique (iii), although basically identical with technique (ii), is likely to suffer from side effects