Abstract
Using the OFDM parameters for broadband wireless access systems, this paper first clarifies the performance disparities between the sets of modulation, detection and FEC rates, assuming the same information rate : specifically, 8PSK and 16QAM for coherent detection, and D8PSK and 16DAPSK for differential detection are examined. It is revealed that 8PSK achieves substantial required-E_b/N_o performance improvements over the others. Moreover, differential detection incurs severe PER performance degradation in non-linear environments and long-multipath-existing environments. For actual application of coherent detection, this paper proposed a RLS-algorithm-based initial-equalization (IE) scheme, with practical implementation in mind. It is revealed that the proposed scheme exhibits excellent PER performance when the preamble of 2 OFDM symbols or more is allowed for coherent detection. It also revealed that the simple frequency-domain IE scheme can be a practical choice when the single-FFT- period preamble must be used.
