Multicell Downlink Capacity with Coordinated Processing

This paper considers the application of cooperative base-station (BS) transmission schemes to the downlink of multicell networks. Based on a simplified Wyner-type network model with users clustered at the cell-edges, closed form sum rate expressions for non-fading channels are derived for dirty-paper coding (DPC), linear zero-forcing (ZF) precoding, and co-phasing with reuse. By extending the model to include cell-interior users, the capacity region for various transmission strategies is determined for the rate pairs achievable by the two classes of users. In addition to the upper bound of DPC across the whole network and the simple approach of having adjacent BSs alternate between serving cell-edge and cell-interior users, we consider several hybrid approaches to serve cell-interior users in each cell but cell-edge users in alternating cells. These hybrid approaches allow the cooperation to be localized among adjacent BSs based on either DPC or superposition coding (SPC). The resulting capacity regions show the tradeoff for improving performance based on techniques that have differing levels of BS cooperation and processing complexity and differing requirements for channel state information at the transmitter.