In this paper, we design a new polar slotted ALOHA (PSA) protocol over the slot erasure channels, which uses polar coding to construct the identical slot pattern (SP) assembles within each active user and base station. A theoretical analysis framework for the PSA is provided. First, by using the packetoriented operation for the overlap packets when they conflict in a slot interval, we introduce the packet-based polarization transform and prove that this transform is independent of the packet's length. Second, guided by the packet-based polarization, an SP assignment (SPA) method with the variable slot erasure probability (SEP) and a SPA method with a fixed SEP value are designed for the PSA scheme. Then, a packet-oriented successive cancellation (pSC) and a pSC list (pSCL) decoding algorithm are developed. Simultaneously, the finite-slots throughput bounds and the asymptotic throughput for the pSC algorithm are analyzed. The simulation results show that the proposed PSA scheme can achieve an improved throughput with the pSC/SCL decoding algorithm over the traditional repetition slotted ALOHA scheme.Index Terms-Slotted ALOHA, polar code, slot erasure channel, successive cancellation list decoding.
I. INTRODUCTIONMotivated by the critical need to better support massive machine to machine communication in the upcoming cellular communications, contention resolution diversity slotted ALOHA (CRDSA) [1], irregular repetition slotted ALOHA (IRSA) [2] and coded slotted ALOHA (CSA) [3] were proposed to enhance the throughput of uncoordinated random access schemes by using the iterative successive interference cancellation (SIC) technique to resolve packet collisions. In slotted ALOHA schemes, a binary vector, called as the users slot pattern (SP), is used to denote the slot positions whereby the copies of the user information packet will be transmitted within these slots and marked them as '1's, otherwise marked as '0's. The number of non-zero elements in the vector is denoted as SPs weight. For example, a user's SP is (1, 0, 0, 0, 0, 0, 1, 0) which means that the 1st and 7th slots are used to transmit the user's packet copies in a slot-frame. It is well known that the CRDSA scheme uses an identical 1/2rate repetition encoding of the information packet for each active user, that is, guided by optimized weight-2 SPs, each user transmits twice copies within a slot-frame simultaneously. Compared to the CRDSA, the most different aspect of the IRSA schemes lies in the multiple weights of SPs. In the CSA scheme, as a generalization of IRSA scheme, before