In MC-CDMA, the data rate can be increased by reducing the spreading factor SF or by allowing multicode transmission. In this paper, we examine by computer simulations which gives a better bit error rate (BER) performance - lower SF or multicode operation - when high level modulation is used in addition to error control coding. For a coded system in a frequency selective channel, there is a trade-off among frequency diversity gain due to spreading, improved coding gain due to better frequency interleaving effect and orthogonality distortion. It is found that for QPSK, the performance of OFDM (MC-CDMA with SF=1) is almost the same as that of a fully spread MC-CDMA system. However, for 16QAM and 64QAM, the BER performance is better for lower SF unlike the uncoded system, wherein higher SF gives a better BER.
- Channel coding
- Frequency diversity
- High-level modulation
- Spreading factor
ASJC Scopus subject areas
- Computer Networks and Communications
- Electrical and Electronic Engineering