Experiments on IP Packet Transmission Performance Employing Adaptive Modulation and Channel Coding in Forward Link for VSF-OFCDM Broadband Wireless Access

摘要

This paper presents experimental results on IP packet throughput and delay performance over Radio Access Network (RAN) employing Adaptive Modulation and channel Coding (AMC) and hybrid ARQ with packet combining in the forward link using 100-MHz bandwidth for VSF-OFCDM (Variable Spreading Factor-Orthogonal Frequency and Code Division Multiplexing) broadband wireless access. Experimental results when AMC and Incremental redundancy were employed, the time delay was decreased as the number of paths was increased since the fluctuations of the received signal level becomes smaller and it was increased according to the increase of fading maximum Doppler frequency.f{sub}D due to the degradation of tracking ability of AMC. Furthermore, it was elucidated that the maximum total time delay over RAN at the cumulative distribution of 99 (50) %, including the delay caused by buffering in MAC (Medium Access Control) layer hybrid ARQ and reordering control, became approximately 25 (10) msec in the region of average received E{sub}s/N{sub}0 (signal energy per symbol-to-background noise power spectrum noise density ratio) more than approximately OdB assuming the user throughput of 20 Mbps and channel model as 6-path channels with, f{sub}D = 20 Hz.