Coverage and ergodic rate in K-tier downlink heterogeneous cellular networks

Cellular networks are becoming increasingly heterogeneous due to the co-deployment of many disparate infrastructure elements, including micro, pico and femtocells, and distributed antennas. This introduces new challenges in the modeling, analysis, and design of these networks. While grid- based models have been quite popular in modeling classical macrocell networks, they are both analytically intractable and have limited applicability to heterogeneous cellular networks (HCNs). We propose a flexible, accurate and tractable model for a general downlink HCN consisting of K tiers of randomly located BSs, where each tier may differ in terms of average transmit power, supported data rate, and BS density. Assuming 1) a mobile connects to the strongest BS, and 2) received power is subject to Rayleigh fading and path loss, we derive expressions for the coverage probability, ergodic rate and the average rate conditioned on the mobile being in coverage as the functions of target Signal-to-Interference-Ratio (SIR).