Space-time eigenrake and downlink eigenbeamformer: Exploiting long-term and short-term channel properties in WCDMA

For WCDMA base stations using adaptive antennas, we present a new space-time rake structure for uplink reception. Our approach combines short-term and long-term spatial and temporal channel properties using an eigenanalysis. By choosing dominant eigenbeams in time and space, the algorithm enhances interference suppression as well as spatial and temporal receive diversity. In contrast to previously introduced well-known receiver structures, the space-time eigenrake inherently adapts to different propagation environments and achieves higher spectral efficiency than other receivers, e.g., the beamformer rake. This is illustrated by Monte-Carlo simulations. Finally, we extend the proposed concept to the downlink, improving closed-loop downlink diversity compared to other proposals in standardization. Even though the feedback rate remains unchanged, additional antenna elements can be included to increase antenna and diversity gains.