Channel Equalization in HSDPA Receivers: Trade-Off between Performance and Complexity with a Variable Oversampling

In this paper algorithms for HSDPA receivers are investigated and optimized to achieve the specified performance while obtaining a low energy consumption. Different approaches including standard Rake combiner, MMSE and prefilter-Rake equalizers in combination with a variable oversampling ratio are discussed. The bit error rate (BER) is simulated within a complete fixed point physical layer model and the complexity of the different algorithms is compared. All equalizers fulfil the requirements of the specifications even for a vehicular propagation channel with a receiver velocity of 30 km/h. The prefilter-Rake equalizer using the Levinson algorithm reaches a throughput of 1.5 Mbit/s for SNR values greater than 6.1 dB. The comparison of performance and complexity demonstrates that the oversampling ratio can be tuned down to 2 samples per chip depending on the environment to reduce the complexity and energy consumption while maintaining the demanded performance