Downlink sum-rate performance for cooperation and coordination between three interfering sectors

In this paper we investigate the performance of various transmission schemes for the downlink cellular system. These schemes are either biased towards interference minimisation or the efficient utilisation of the available resources. A mathematical model for the various schemes is presented and the performance measure is based on the information theoretic sum rate and the user rate share. The identified schemes are: avoid intra-cell and tolerate inter-cell interference, full orthogonality, single cell cooperation, cooperation for critical users only and the full cooperation scheme. Two categories of users are identified in this paper: non critical users which are close to the base station and the critical user which are at the cell boundary. It is observed that the full cooperation provides an upper bound on the achievable sum rate and has a user rate distribution whose fairness can be improved by allocating more power to the critical users. The full orthogonality scheme has the fairest user rate distribution and much lower achievable sum rate compared with the full cooperation. The performance of the cooperation of critical user scheme can approach the upper bound of full cooperation scheme with lower complexity