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Irregular Repetition Slotted ALOHA Scheme with Multi-Packet Reception in Packet Erasure Channel

In massive machine-type communications (mMTC), a large amount of devices demand to access to the network via a commonly sharing wireless channel. Uncoordinated frequent channel contention associated with channel variation bring a big challenge for improving the performance of massive access system. Irregular repetition slotted ALOHA (IRSA), as a typical grant-free random access protocol, exploits collided signals for packets recovery and possesses a great potential in improving the access capability and throughput of the mMTC system. In this paper, we analyze the performance of IRSA scheme with multi-packet reception where the access point (AP) can simultaneously retrieve multiple packets in a collided signal under packet erasure channel. In particular, decoding failure probabilities during each round of iterative packet recovery are expressed clearly, based on which the packet loss ratio and the throughput of the system are characterized in detail. Simulation results validate the correctness of the theoretical analyses. By selecting appropriate distribution of the replica number of packet, the error floor caused by the packet erasure can be decreased. Besides, the throughput of the massive access system can be improved by optimizing the link load of the IRSA scheme.