Frequency allocation in non-coherent joint transmission CoMP networks

In this paper, we study the problem of joint transmission (JT) in coordinated multipoint (CoMP) networks from a new point of view where the system performance is optimized via frequency allocation for 5G small cells. Moreover, we investigate the implementation of hybrid automatic repeat request (HARQ), as an efficient scheme facing the feedback load problem in CoMP setups. The results are obtained for the cases with slow and fast fading conditions. Considering the channel state information (CSI) only at the receiver, we show that at low and medium signal to noise ratios (SNRs) sharing the frequency resources between users outperforms the case when the frequency resources are dedicated under non-coherent JT-CoMP setting. We find that the maximum long term throughput is achieved by either sharing the entire frequency resources between the users or allocating each user in a disjoint dedicated frequency resource. These extreme cases show the best performance in the SNR region of interest. Finally, as demonstrated analytically and numerically, HARQ feedback increases the long term throughput and reduces the outage probability substantially, with an affordable average delay.