In this paper it is shown how spatial and temporal processing can be combined to increase the capacity of CDMA-based wireless communications systems. Degrees of freedom provided by space-time processing can be exploited to combat both fading and co-channel interference (the near-far effect). Specifically, we formulate and study the following methods: (1) space-time diversity, (2) cascade optimum spatial-diversity (RAKE) temporal, (3) cascade optimum spatial-optimum temporal, and (4) joint domain optimum processing. It is shown that, due to its interference cancellation capability, optimum combining provides significantly better performance than diversity processing. In particular, it is shown that in a typical CDMA scenario with two antennas, the joint domain optimum combining system provides at least a 25% increase in capacity over diversity processing. Optimum combining may be applied to compensate for imperfect power control of the signals received at the base station.
All Science Journal Classification (ASJC) codes
- Computer Science Applications
- Electrical and Electronic Engineering