  Coordinated multi-point (CoMP) transmission is an effective means of
improving network throughput in heterogeneous cellular networks (HetNets).
However, its performance is seriously weakened if imperfect coordination
happens between base stations (BSs). Many prior CoMP works do not consider
inter-cell overhead message delays such that a seemingly astonishing CoMP
throughput gain is attained. In this paper, the quantization error and delay
that actually exist in overhead messages was modeled and we developed a much
tractable SIR model based on the stochastic geometry framework. We proposed
adaptive CoMP that is applied to downlink zero-forcing beamforming (ZFBF) and
it can mitigate the interference from the coordinated cells with delayed
overhead messages. The bounds on the complementary cumulative distribution
function (CCDF) of the SIR of a user are characterized such that the average
throughput of a user is able to be analytically evaluated. Numerical results
show that the proposed adaptive CoMP scheme can make the throughput gain very
robust to the overhead delay and thus significantly increase the throughput
even when BSs are not perfectly coordinated.
