Performance Improvement of WiMedia-Based UWB Systems by Hybrid ARQ

The automatic repeat request (ARQ) scheme makes use of error detection to identify if retransmission is required. Hybrid ARQ (HARQ) uses an error control code in conjunction with ARQ and can reduce the number of transmissions required, thus giving a better goodput performance. When packet combining (PC) is carried out in the HARQ scheme, PER can be greatly improved. This paper investigates the performance of different HARQ schemes under various data rates based on the WiMedia specifications. It has been found that Type 1 HARQ with packet combining works best for low data rates and greatly reduces PER while increasing goodput. At higher data rates, both Type 3 HARQ with packet combining, as well as Type 2 HARQ, are more suitable. Type 2 HARQ can decrease the number of transmissions required and thus increase goodput, while Type 3 HARQ with packet combining greatly reduces PER and thus increases goodput as well. The tradeoff of implementing HARQ for performance improvement would be an increase in the implementation complexity. If device complexity is a concern, Type 1 with PC is the ideal HARQ scheme to use at all data rates.