Performance Analysis of Centralized RAN Deployment with Non-Ideal Fronthaul in LTE-Advanced Networks

Centralized RAN and baseband pooling architectures are increasingly being seen as the way cellular technologies will be deployed in the future due to a number of advantages they provide to the operator. However, LTE and LTE-Advanced were designed with a distributed architecture in mind. Therefore, there are certain inherent technical issues when the link connecting the baseband and RRU (Remote Radio Unit) has a non-negligible latency. In this paper, we study the impact of this non-ideal fronthaul on the downlink and uplink performance of LTE-Advanced networks. We show that, while the impact on the peak throughput is quite severe, it is more modest when we have a larger number of active UEs. The degradation in performance is larger in the uplink than in the downlink due to the synchronous HARQ mechanism used in LTE uplink. In the downlink, we compare the performance of centralized RAN with that of distributed RAN in case of non-ideal fronthaul (FH) and backhaul (BH), respectively, and determine whether it is better to incur backhaul or fronthaul latency from a performance perspective. In the uplink, we analyze the loss in performance due to fronthaul latency. We have developed a novel look-ahead scheduling scheme that results in significant improvement in performance, especially when the number of active UEs is small.