Optimisation of Spectrum Utilisation for Backhaul Networks in the 7–8 GHz Band

Abstract

In the electromagnetic spectrum, the 7–8 GHz frequency band has long been used for wireless communication due to the favourably low rain attenuation. Today, in Canada and many other countries, incumbent use of this band includes microwave backhaul links, also referred to as Fixed Services (FS). However, the band’s future is under discussion, with FS preparing for a possible increase in network capacity and other services investigating whether the band can be shared. This thesis investigated whether the current FS network could be replanned to optimise spectrum utilisation, thereby providing a baseline for discussions on opportunities to increase microwave link capacity and utilisation in the band. Each FS link in Toronto, Montreal, and Vancouver was modelled using public Canadian data from Innovation, Science and Economic Development of Canada (ISED). While preserving link properties, a greedy heuristic algorithm was applied to optimise spectrum utilisation. The results of the optimisation algorithm show that fixed services can use a smaller interval of carrier frequencies both within channel allocation subplans and across the frequency band. In Toronto, Montreal and Vancouver, all FS links could be concentrated within a 550 MHz interval, leaving approximately 600 MHz of continuous spectrum available. For future capacity increase, the results indicate that additional capacity may be possible within the 550 MHz interval, although a comprehensive study is left for future work. In Vancouver, the spectral footprint could only be reduced for the mainland urban area, mainly due to multi-link hops limiting further compression. Overall, the results are promising and indicate that spectrum utilisation in the Canadian 7–8 GHz FS band can be improved through replanning, while also highlighting topologydependent constraints that should be considered in future studies.