Universal multiple access via spatially coupling data transmission

We consider a signaling format where information is modulated via a superposition of independent data streams. Each data stream is formed by replication and permutation of encoded information bits. The relations between data bits and modulation symbols transmitted over the channel can be represented in the form of a sparse graph. The modulated streams are transmitted with time offsets enabling spatial coupling of the sparse modulation graphs. We prove that iterative demodulation based on symbol estimation and interference cancellation followed by parallel error correction decoding is a universal multiple access technique which achieves the entire capacity region of the additive white Gaussian noise (AWGN) multiple access channel.