The Impact of Interference on Macrodiversity Gain in mmWave Cellular Networks

In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks in presence of blockage and interference. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to non-LOS (NLOS). We identify macrodiversity as an important strategy for mitigating blocking, as with macrodiversity the user will attempt to connect with more than one base station. Diversity is achieved because if the closest base station is blocked, then the next base station might still be unblocked. However, since it is possible for the transmitters have LOS path to more than one base station simultaneously the received signal is also affected by the sum interference, the issue of interference should be taken into account by the analysis. Our analysis characterizes the macrodiverity gain in the presence of co-channel interference arising from other cells. To do so, we develop a framework to determine the distribution Signal to Interference and Noise Ratio (SINR) by taking into account blocking. We consider a cellular uplink with both diversity combining and selection combining schemes. We show that other performance matrices that ignore the effect of interference such as LOS probability and SNR can lead to an incorrect evaluation of macrodiversity gain, as interference tends to decrease macrodiversity gain.