Performance of hybrid ARQ for high speed downlink packet access in UMTS

An expanded effort is underway to support the evolution of the UMTS standard to meet the rapidly developing needs associated with wireless Internet applications. The support of packet-switched high-speed data users is provided by means of a new, shared channel called HS-DSCH (high speed downlink shared channel) that preferably serves one packet data user at a time in a time-multiplexed manner. A number of performance enhancing technologies are included in the high speed downlink packet access (HSDPA) proposal to ensure high peak and average packet data rates while supporting circuit switched voice and packet data on the same spectrum. These techniques include adaptive modulation and coding (AMC), hybrid ARQ (HARQ), fat-pipe scheduling, fast cell site selection (FCSS) and multiple input multiple output (MIMO) antenna techniques. In this paper, we provide the performance comparison of different HARQ schemes being considered for HSDPA