Orthogonal Sparse Superposition Codes

This paper presents a new class of sparse superposition codes for efficient short-packet and low-rate communication over the AWGN channel. The new codes are orthogonal sparse superposition codes, in which a codeword is constructed by a superposition of orthogonal columns of a dictionary matrix. We propose a successive encoding technique to construct such codewords. In addition, we introduce a near-optimal decoding, named an element-wise maximum a posterior decoding with successive support set cancellation, which has a linear decoding complexity in block lengths. Via simulations, we demonstrate that the proposed encoding and decoding techniques are less complex and better performing than existing coded modulation techniques for reliable short packet communications.