On Interference in Uplink SDMA SC-FDE system

In this paper, the issue of channel estimation with multiple in-cell co-channel users (ICUs) in the presence of out of cell interferers (OCIs) is addressed. A single carrier frequency domain equalization (SC-FDE), uplink space division multiple access (SDMA) system with iterative block decision feedback equalization (IBDFE), based on the soft decisions is considered. To overcome the intra-cell interference, it is shown that if orthogonality between users during their training phase is assured, then good performance is achievable compared to non-orthogonal training. Moreover, we have shown that the way to multiplex the training either in time or frequency, does not affect the performance in time-variant channels as long as the orthogonality is maintained. It is also shown that inter- cell interference could be mitigated with a combination of in-cell orthogonal pilots, spatial diversity and iterative receiver processing. Performance improvement by an IBDFE based on the soft decisions is also shown.