Performance Analysis of Irregular Repetition Slotted Aloha with Multi-Cell Interference

Irregular repetition slotted aloha (IRSA) is a massive random access protocol in which users transmit several replicas of their packet over a frame to a base station. Existing studies have analyzed IRSA in the single-cell (SC) setup. In this work, we analyze multi-cell (MC) IRSA, accounting for pilot contamination and multi-user/MC interference. We find that, in practical settings, the throughput of MC IRSA can be up to 70% lower than SC IRSA. Further, MC IRSA requires a significantly higher training length (about 4 − 5x compared to SC IRSA) to support the same user density and achieve the same throughput. We provide insights into the impact of the pilot length, number of antennas, and SNR on the performance of MC IRSA.