In this paper, we propose a novel approach for the enhancement of slotted ALOHA protocol in general cellular networks, deploying relays to expand their coverage area. In our study, we focus on uplink access and consider a moderate access rate of users to the wireless medium, i.e most of the collisions occur between two packets. When two users transmit simultaneously during the same time slot, a Spatial Successive Interference Cancellation (SSIC) is performed at the destination to separate collided packets. If this separation fails, our idea is that a relay selected from the set of available relays amplifies and forwards the signals received from the two users. Then, the destination combines the received signals coming from the interfering users and from the relay. We evaluate the performance of the proposed approach in terms of throughput and bit error rate (BER). Simulation results show that our approach achieves significantly better performances in terms of BER and through put than both conventional slotted ALOHA protocol and collision resolution with interference cancellation.