Distributed opportunistic medium access control in two-tier femtocell networks

In this paper we propose distributed opportunistic access techniques for femtocell-overlaid cellular networks, where each femtocell access point (FAP) decides to access the medium independently and in a distributed manner based on local link quality information. Specifically we introduce various opportunistic medium access policies, namely channel-based, interference-based, SIR-based, and rank-based, under which each FAP transmits after comparing a certain link quality metric with a predefined threshold. Considering a network in which FAPs are located according to a homogeneous Poisson point process, the performance of distributed low-overhead access schemes in terms of success probability, area spectral efficiency, and average data rate is evaluated. Furthermore, we determine the probabilistic access thresholds that provide the best possible tradeoff between spatial reuse and network throughput. Simulation results support the analysis and quantify the network throughput gains of different access policies in various operating regimes.