Channel Estimation for SIR Measurement in HSDPA Systems

To achieve good throughput performance and small delay, HSDPA are introduced in WCDMA systems. One of the key features of HSDPA is adaptive modulation and coding (AMC), which involves adaptively changing the transport format according to the condition of the receiver. To decide the transport format, the mobile station should measure SIR and send CQI (channel quality indicator) based on the SIR value. This paper proposes a method of SIR measurement for CQI in HSDPA systems. We also show that straightforward implementation of SIR measurement causes performance degradation for the high speed moving environment, and propose a new SIR measurement method. Specifically we propose a new channel estimation method for interference measurement. In this method, only the CPICH symbol within a measurement period is used for channel estimation while the reference signal for interference is still a moving average. We show by simulation that the throughput of the proposed method is 50% better than that of a conventional method under a high speed moving environment.