PRECODING FOR COOPERATIVE MIMO

Abstract

Cooperative MIMO has emerged as an attractive way of increasing the spectral efficiency of cellular wireless communication. However, for this idea to work, both intra-cell and inter-cell interference has to be mitigated. Interference cancellation techniques for conventional MIMO systems are not capable of handling inter-cell interference. For this reason, precoding for cooperative MIMO has received a lot of attention recently. Cooperation among receiving nodes, known as relaying, received initial attention and proved to be instrumental in improving link level reliability. Precoding criteria and technique for different relaying schemes has been addressed in our work. However, because of difficulty in practical implementation of cooperation among nodes, base station cooperation appeared to be a more promising solution. Precoding for cooperative MIMO, with base station cooperation, depends largely on capacity of the backhaul network that connects the base stations for information exchange. If capacity of backhaul network is low then `interference coordination' strategy is used, where precoding is done based on global CSI only. But if capacity of backhaul network is high, then the more powerful strategy of `full cooperation' is used. In this case precoding is done based on global CSI as well as user data. Zero forcing precoding, which comes under the category of `full cooperation' has been studied. Performance of `ICBF', which is an `interference coordination' strategy, has been investigated and compared with zero forcing precoding. A novel precoding technique, called `cooperative ICTS', based on combination of base station cooperation and ICTS scheme is proposed. Performance of this proposed scheme is evaluated and compared with other schemes. Finally, another precoding technique for `full cooperation' has been investigated using an iterative algorithm.