Adaptive Downlink CoMP in Heterogeneous Cellular Networks with Imperfect Overhead Messaging

TL;DR

This paper models the impact of overhead message delays in CoMP for HetNets and proposes an adaptive scheme that maintains throughput gains despite imperfect coordination.

Contribution

It introduces an adaptive CoMP method for downlink ZFBF that accounts for message delays, enhancing robustness of throughput in HetNets.

Findings

Adaptive CoMP mitigates interference with delayed messages.

Throughput gains are robust to overhead delays.

Analytical bounds for user SIR are derived.

Abstract

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.