Performance analysis in indoor femtocell networks using ESPAR antennas

This paper investigates the coverage performance of indoor downlink femtocell networks where we use directional reception at the user terminal (UT) by deploying an electronically steerable parasitic array receptor (ESPAR) antenna. The ESPAR antenna uses only a single radio frequency (RF) chain surrounded by passive elements to form electronic beampatterns. It therefore, can be made practical to fulfill the requirements of wireless user terminals constrained by low-cost, low-power and small-size. The femtocell access points (FAPs) are assumed to be distributed as a homogenous spatial poisson point process (SPPP) and each femtocell access point (FAP) is equipped with an omnidirectional antenna. Considering this scenario, we derive a closed-form formula for coverage probability by using a simplified mathematical model introduced in [1]. This model provides an approximate indoor femtocell co-channel interference distribution by approximating the number of FAPs to a binomial distribution by considering only the strong interfering FAPs. In particular, as the user terminals equipped with ESPAR antennas form receiver beampatterns that divide the receiving angular space into several sectors. The angles of arrival (AoA) of FAPs interferers then lie within the desired sector and within a specified distance R from the user. These interfering FAPs are considered as the strong and effective interferences when deriving the analytical closed form formula of the coverage probability. Finally, the simulated and the analytical closed-form of the coverage probability performance are compared for various interference intensities of the proposed indoor femtocell networks and we show that considerable improvement can be achieved when ESPAR antenna is deployed at the UT.