A New Two-User Binary Polar Coded Multiple Access Scheme with Power and Rate Allocation

A new polar-code-based scheme with power and rate allocation is proposed to enhance the block error rate (BLER) performance in a two-user binary Gaussian multiple access channel (GMAC). Unlike previous works which mainly focused on the capacity-achieving capability of polar codes in the multiple access channel, we improve their finite-blocklength coding performance in the specific two-user channel. In our proposed scheme, each user employs two blocks of polar codes with unequal transmit power levels, and a notable feature of our approach is that the code construction and rate allocation of these two blocks as well as their power levels can be jointly optimized to give rise to performance improvement. We analytically derive the BLER upper bound of the proposed scheme using the information-theoretic coding performance approximation in the finite blocklength regime. We demonstrate the validity of our approach through simulations and show the performance advantages of the proposed scheme over the previously reported two-user LDPC-based and polar-coded GMAC of similar blocklength.