Throughput Analysis for a UMTS High Speed Downlink Packet Access LMMSE Equalizer

Abstract — UMTS addresses future packet services over chan-nels with fluctuating quality via its High Speed Downlink Packet Access (HSDPA) sub-system. The throughput over HSDPA decreases significantly due to Multiple Access Interference (MAI). In this contribution, it is shown by simulation that the Linear Minimum Mean Square Error (LMMSE) equalizer shows supe-rior throughput than a conventional RAKE receiver. The gain in Ec/Ior is approximately 1.6–2 dB depending on the modulation scheme. We have developed a simulation environment specifically tai-lored to HSDPA for investigating the HSDPA receiver requirements. The downlink physical layer for the user data on the High Speed Physical Downlink Shared Channel (HS-PDSCH) is modelled in detail, whereas the associated signalling is idealised as error-free. The interference from signalling and data channels on the HS-PDSCH is modelled adequately. As a general guideline for system settings in the simulations, we use the test cases specified in 3GPP TS 25.101 whenever applicable. I