Connectivity in mmWave Cellular Networks With Energy Harvesting Relays and Correlated Blockages

This paper considers a mmWave network with energy harvesting relays, where a source transmitter connects to the nearest base station either directly or through the closest relay. The source transmitter is connected to the base station if either the direct path is line-of-sight (LOS) or the indirect path is LOS and the relay has sufficient energy. Under these conditions, A closed-form expression for the connectivity probability is derived, considering the possibility of correlated blockages. The accuracy of the derived mathematical expressions is validated through Monte Carlo simulations. The paper examines how correlated blockages, blockage density, and the energy harvesting rate impact system performance. In addition, the performance of the relaying system is compared to second-order macrodiversity, which employs two base stations. The results indicate that, for a given set of system parameters, the impact of correlation is less significant on energy harvesting relaying systems than on macrodiversity systems. Furthermore, while an increase in the energy harvesting rate improves connectivity probability, its effect becomes negligible beyond a certain threshold. At high blockage densities, the impact of energy harvesting rates is significantly reduced, as the connectivity probability is primarily governed by blockage events. Lastly, to achieve similar performance to a second-order macrodiversity system, the relay density in the relaying system needs to be 3 times that of the base station density, i.e., more relays are required than base stations. However, relays offer a more cost-effective and less complex solution.