Impact of Frequency Diversity and Multi-User Diversity in IFDMA

Single-carrier frequency division multiple access (SC-FDMA) has been decided to be adopted in the uplink of the future wireless communication system. Interleaved frequency division multiple access (IFDMA), whose transmitted signal is generated in the time domain, is a candidate of SC-FDMA. The number of comb like spectrum and the spectral interval between each spectrum depend on the number of transmission data symbols Q in one IFDMA block and repetition number L. In the case of large Q and small L, large frequency diversity gain can be obtained due to the number of spectrum is increased. However, inter-chip interference (ICI) owing to the multipaths environment increases. In the multi-user environment, it is difficult to get multi-user diversity due to the decrease of the degree of freedom for channel allocation to each user with large Q and small L. On the other hand, in the case of small Q and large L, frequency diversity gain becomes smaller and ICI is decreased. Furthermore, multi-user diversity gain can be obtained due to the increase of the degree of the freedom for channel allocation. Thus, it is quite interesting to see how the parameters in IFDMA, i.e., Q and L, affect the average bit error rate (BER) performance in the multi-user environment. In this paper, we derive average BER performance of IFDMA in the multi-user environment theoretically by taking into account of frequency diversity, multi-user diversity and ICI when Q and L are changed and then average BER performance of IFDMA is compared to that of OFDM. In addition, the validity of the theoretical analysis is confirmed by computer simulation.