Study on Scheduling Techniques for Ultra Dense Small Cell Networks

The next generation of wireless cellular networks (5G) must encapsulate different technologies to meet the wireless throughput demand over the next decade. A promising approach to enhance network capacity is spatial densification, which benefits from the extensive spatial reuse of the spectrum and the reduced distance between transmitters and receivers. In this paper, we examine the performance of different schedulers in ultra dense small cell deployments. We discuss that, due to LOS presence at low ISDs, the Rican fading channel model is more suitable to study network performance than the Rayleigh one, and model the Rician K factor as a function of distance between the UE and its serving BS. We also construct a cross-correlation shadowing model that takes into account the ISD. We investigate the potential of multi-user diversity gains in ultra dense small cell deployments by comparing the performances of proportional fair (PF) and round robing (RR) schedulers. Simulation results show that as network becomes denser, the LOS component starts to dominate the path loss model which significantly increases the interference. They further show that multi-user diversity is considerably reduced at low ISDs, and thus the PF scheduling gain over the RR one is very small, around 10% in terms of cell throughput. As a result, the RR scheduling may be preferred for dense small cell deployments due to its simplicity. Our results also show that despite both the interference aggravation as well as the multi-user diversity loss, network densification is still worth it from a capacity view point.