Cloud Based Small Cell Networks: System Model, Performance Analysis and Resource Allocation

In cloud-based small cell networks (C-SCNs), radio resource allocation at the base station (BS) is moved to a cloud data centre for centralised optimisation. In the centre, multiple processors referred to as the cloud computational unit (CCU), is used for the optimisation. As the cell size and networks become respectively smaller and denser, the number of BSs to be optimised grows exponentially, resulting in high computational complexity and latency at CCUs. This thesis propose belief propagation (BP) based power allocation schemes for C-SCNs that can be used for any network optimisation objectives such as energy efficiency at the centre and BSs; and spectral efficiency (SE). The computation for the schemes is done in parallel, leading to very low latency and computational complexity with increasing number of BSs. The transmission-latency depends on the number of bits used to quantise the received signal from terminals at the remote radio head (RRH). The computational-latency depend on the speed of resource allocation procedure at the CCU. BP based joint SE and latency optimisation scheme that compute the optimum terminal’s uplink power and number of quantisation bits for each RRHs. The results indicate a significant reduction in transmission and computational-latencies compared to other schemes. This thesis further investigates a user association (UA) to the BS and subcarrier allocation (SCA) where a BS allocates different number of SC to different users associated to it. In jointly optimising the UA and SCA, the Sharpe Ratio (SR) is used as the utility function, which is defined as the ratio between the mean of user achievable rates to its standard deviation. Thus, the achieved user rates will be closer to each other, leading to a fair network access. By using binary BP algorithm, the results show that the achievable user rates are doubled in comparison with other schemes