Performance Evaluation of Adaptive Array Using ZF and MMSE Algorithms with Measured K-Factor and Correlation in Heterogeneous Networks

In LTE-Advanced heterogeneous networks, a typical cell layout to enhance frequency utilization is to incorporate picocells and femtocells in a macrocell. However, the co-channel interference between the marcocell and picocell/femtocell is an important issue when the same frequency band is used between these systems. In this paper, we evaluate the interference rejection characteristics by an adaptive array for user equipment (UE) with Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) algorithms. The characteristics are evaluated based on the K-factor used in the Nakagami-Race Fading model and the spatial correlation that is obtained in an actual outdoor environment. It is shown that a two-element adaptive array at the macro UE (M-UE) can sufficiently reduce the interference from the femto base station (F-BS) to the M-UE even if the number of total signals exceeds the degrees of freedom of the array. Moreover, 1.5 dB SINR difference is observed when comparing ZF and MMSE algorithms when the number of interfering signals is two.