Spectral efficiency of dynamic coordinated beamforming: a stochastic geometry approach

Abstract

This paper characterizes the performance/nof coordinated beamforming with dynamic clustering. A/ndownlink model based on stochastic geometry is put/nforth to analyze the performance of such base station/n(BS) coordination strategy. Analytical expressions for the/ncomplementary cumulative distribution function (CCDF)/nof the instantaneous signal-to-interference ratio (SIR) are/nderived in terms of relevant system parameters, chiefly the/nnumber of BSs constituing the coordination clusters, the/nnumber of antennas, and the pathloss exponent. Utilizing/nthis CCDF, with pilot overheads further incorporated into/nthe analysis, we formulate the optimization of the BS/ncoordination clusters for a given fading coherence. Our/nresults indicate that (i) coordinated beamforming is most/nbeneficial to users that are in the outer part of their cells/nyet in the inner part of their coordination cluster, and that/n(ii) the optimal cluster cardinality for the typical user is/nsmall and it scales with the fading coherence. Simulation/nresults verify the exactness of the SIR distributions derived/nfor stochastic geometries, which are further compared/nwith the corresponding distributions for deterministic grid/nnetworks.