Performance analysis and optimal cooperative cluster size for randomly distributed small cells under cloud RAN

One major advantage of cloud/centralized radio access network is the ease of implementation of multi-cell coordination mechanisms to improve the system spectrum efficiency (SE). Theoretically, large number of cooperative cells lead to a higher SE; however, it may also cause significant delay due to extra channel state information feedback and joint processing computational needs at the cloud data center, which is likely to result in performance degradation. In order to investigate the delay impact on the throughput gains, we divide the network into multiple clusters of cooperative small cells and formulate a throughput optimization problem. We model various delay factors and the sum-rate of the network as a function of cluster size, treating it as the main optimization variable. For our analysis, we consider both base stations' as well as users' geometric locations as random variables for both linear and planar network deployments. The output signal-to-interference-plus-noise ratio and ergodic sum-rate are derived based on the homogenous Poisson point processing model. The sum-rate optimization problem in terms of the cluster size is formulated and solved. Simulation results show that the proposed analytical framework can be utilized to accurately evaluate the performance of practical cloud-based small cell networks employing clustered cooperation

Rate Region of the Multi-Cell Multiple Access Channel under Backhaul and Latency Constraints

Recently, multi-cell joint transmission and joint detection schemes have been identified as promising features of next generation mobile communications systems, as they enable to actively exploit inter-cell interference rather than treating it as noise. Both for uplink and downlink, concrete algorithms have been proposed, and strong increases in spectral efficiency and system fairness have been predicted. Besides posing strong requirements towards the time and frequency synchronization of communicating entities, one essential problem connected to multi-cell cooperative signal processing is the large extent of backhaul required between base stations and an increased detection latency. In this paper, we focus on the latter two aspects in the context of a cellular uplink. We consider different schemes of multi-cell cooperative detection and introduce a framework that allows to derive general backhaul- or latency-constrained rate regions for multi-cell multiple access channels (MAC)