Packet transmission in fourth-generation broadband multimedia wireless communication systems

In this paper, different hybrid ARQ techniques consisting of type I chase combining, type II incremental redundancy and type III variant incremental redundancy have been investigated for the chosen variable spreading factor orthogonal frequency code division multiplexing (VSF-OFCDM) based fourth generation communication systems for both outdoor and indoor scenarios. The efficient linkage to channel coding and modulation schemes has also been considered. The results show that type II incremental redundancy hybrid ARQ achieves best throughput performance compared to other schemes. It is also shown that the throughput performance for outdoor scenario is better than that for indoor scenario. This is because broadband outdoor channel model provide more diversity for hybrid ARQ scheme which is not true for third generation system. It is observed that Type I can save up to 77% memory requirement compare to type II at the penalty of 3 dB E_b/N₀ loss for both outdoor and indoor scenarios, at the point of view that memory is not a crucial issue for fourth generation application, we may conclude that type II incremental redundancy is the most suitable hybrid ARQ scheme for fourth generation communication system.