Experimental evaluation of hybrid ARQ employing packet combining in forward link for VSF-OFCDM broadband wireless access

摘要

This paper compares the throughout performance using Incremental redundancy (Type-II) and Chase combining (Type-I with packet combining) for VSF-OFCDM (Variable Spreading Factor - Orthogonal Frequency and Code Division Multiplexing) with two-dimensional spreading prioritizing time-domain spreading by the laboratory experiments in the broadband multipath fading channel. The implemented OFCDM transceiver achieves maximum throughput of more than 100 Mbps. Experimental results elucidate that when adaptive modulation and channel coding (AMC) is employed, the measured throughput using Incremental redundancy is increased by approximately 10 % compared to that using Chase combining for the high Doppler frequency channel such as f{sub}D = 140 and 400 Hz, while, the measured throughput values are almost identical for slow Doppler frequency channel such as f{sub}D = 20 Hz.