Optimum Placement of Radio Relays in Millimeter-Wave Wireless Dual-Hop Networks [Wireless Corner]

In modern wireless mesh networks, the transmitted-information signals from the source node arrive at the final destination through relay stations. The introduction of relay stations into metropolitan-area networks allows the provision of ubiquitous broadband access, even in remote places, and increases the scalability potential. Due to the increased demand for bandwidth and the spectral congestion at low frequencies, these wireless mesh networks usually operate at frequencies above 10 GHz, satisfying the line-of-sight condition. In this frequency range, the most dominant fading mechanism degrading the availability of radio links and exposing spatial and temporal stochastic variation is rain attenuation. In this paper, the optimum placement of radio relays in a dual-hop configuration is studied, based on physical prediction models for the total outage probability. The focus is on the spatial inhomogeneity of rain attenuation over the converging microwave paths, which leads to the incorporation of the two-dimensional lognormal distribution. The impact of various operational and geometrical properties of adaptive gain transparent and regenerative radio relays on the outage performance and on the optimum relay position for various locations is investigated through a series of extended numerical results.