DS-CDMA with frequency-domain equalization for high speed downlink packet access

The next generation mobile communications system is anticipated to support data rates up to and exceeding 100 Mbps. In this paper, we consider a DS-CDMA high-speed downlink packet access (HSDPA) as in 3G W-CDMA systems. Adaptive modulation and coding (AMC), multicode operation and hybrid automatic repeat request (HARQ) will be the technologies. With such high-speed data transmissions, however, multicode operation severely suffers from destruction of orthogonality among the spreading codes since the wireless channel becomes severely frequency-selective. In this paper, we apply frequency-domain equalization (FDE) instead of conventional RAKE combining for receiving the packet. It is shown that the use of FDE for the reception of the multicode signal gives an improved throughput irrespective of the channel's frequency selectivity.