Chip-level equalization in the WCDMA downlink
Qihui Wu · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2004
In the downlink of WCDMA systems, the different users are multiplexed synchronously to transmission channel by short orthogonal spreading codes that user specific and a long overlay scrambling code that is base-station specific. It is well known that in a multiple-user synchronous DS-CDMA system with multi-path fading, the widely used rake receiver is sub-optimal. Moreover, as the chip rate increases in high rate wireless applications, the underlying multi-path channels become time dispersive, and introduce frequency selective effects. For WCDMA downlink, receivers based on channel equalization at chip level have been proposed to ensure adequate performance even with a high number of active users. These receivers equalize the channel prior to the dispreading, thus restoring the orthogonality of users and resulting multiple access interference (MAI) suppression. The chip-level equalizer has proven to be one of the most promising terminal receivers for WCDMA/FDD downlink. In this paper, we summarize the technology of the chip-level equalization for WCDMA downlink.