Abstract
To reduce the throughput loss caused by the slot erasure channel (SEC), we propose a polar slotted ALOHA (PSA) framework where the access procedure is decomposed into twostage and jointly optimized under the slot polarization idea. In the first stage, guided by the slot polarization, a slot subset is constructed at each active user side and the receiver side. With an irregular degree distribution, each active user randomly selects slots from the slot subset to transmit the packet replicas. Subsequently, in the second stage, by using the packet-based polarization transform, the slotted packets are encoded by using a packet-level polar code. Correspondingly, at the receiver side, a packet-oriented successive cancellation (pSC) or pSC list decoding algorithm is performed to overcome the corruption caused by the SEC. And then, the success interference cancellation procedure is executed to recover the packet. Furthermore, for a given average transmission rate, the irregular degree distribution is optimized by searching the maximum within all feasible traffic load thresholds. Then, an upper bound of the polar-code rate for the PSA scheme is derived. Simulation results indicate that the proposed PSA scheme can achieve an improved throughput over the irregular repetition slotted ALOHA scheme for the SEC.
