Radio Link Performance on High-Speed Down Link Packet Access and Its Advanced Receivers in W-CDMA Downlink

다국어 초록 (Multilingual Abstract)

This paper presents the radio link performance when employing adaptive modulation and channel coding (AMC) coupled with hybrid automatic repeat request (ARQ) with packet combining based on the High-Speed Downlink Packet Access (HSDPA) air interface in the forward link in multipath fading channels, based on laboratory and field experiments in cellular environments. In the implemented equipment, the optimum modulation and coding scheme (MCS) is selected among four candidates, MCS1 (QPSK data modulation with the channel coding rate R=1/2, hereafter simply referred to as QPSK with R=1/2), MCS2 (QPSK with R=3/4), MCS3 (16QAM with R=1/2), and MCS4 (16QAM with R=3/4), according to the received signal-to-interference power ratio (SIR) over one transmission time interval (TTI) (=2msec) in AMC, and Chase combining and Incremental redundancy are implemented. Field experimental results verify that the peak throughput of approximately 6.4 Mbps is achieved when the instantaneous received SIR is greater than 21dB, at the average moving speed of approximately 30km/h in an actual multipath fading channel (note that the achieved peak throughput of approximately 6.4Mbps at 9-code multiplexing in the experiments suggest the possibility of peak throughput above 10Mbps when 15-code multiplexing is applied). Furthermore, field experiments elucidate that Incremental redundancy exhibits superior throughput performance to Chase combining in lower received SIR environments, thereby in a low throughput channel below approximately 2.3Mbps, where retransmission of data packets frequently occurs caused by the selection errors of the optimum MCS in the AMC. In addition, this paper addresses the usage of advanced receivers such as the multipath interference canceller (MPIC), chip equalizer in the time domain, and frequency-domain equalizer that effectively suppress multipath interference (MPI).

Finally, we demonstrate the MPI suppression effect of MPIC based on experimental investigations: the measured throughput at the cumulative probability of 50% is increased by approximately 1 Mbps.