Outage Performance of Uplink User-Assisted Relaying in 5G Cellular Networks

We use stochastic geometry to analyze the performance of a user-assisted decode-and-forward (DF) relaying scheme where an active user relays data through another idle user in uplink cellular communication. We propose a new geometric policy based on the random selection of an idle user within a certain area mid-way between the active user and base station, and compare this policy to the common nearest neighbor geometric policy. These probabilities are further used in the analytical derivation of the moments of inter-cell interference power caused by system-wide deployment of this user-assisted DF relaying. We then numerically evaluate the outage probability performance and show that user-assisted relaying can significantly improve reliability for active users near the cell edge. We also show that the proposed mid-way policy significantly improves outage performance over the nearest neighbor policy even when the nearest neighbor cooperation probability is higher. This result suggests that mid-way relay selection is a highly effective cooperation policy.