Bits-to-Symbol Mappings for Superposition Coding
(English)Manuscript (preprint) (Other academic)
Superposition coding can be used in scenarios where orthogonal sharing of resources is not efficient. In this paper, we consider two such scenarios in which superposition coding is used to send two or more users data (or packets of data) to the destination with efficient utilization of resources. Conventional way of superposing users data in Euclidean space leads to a natural mapping of bits-to-superposed-symbols. We propose the use of Gray mapping of bitsto-superposed-symbols and study the effect in terms of mutual information at the destination for the two scenarios considered in this paper. We also present some numerical results showing that using a Gray mapping of bitsto-superposed-symbols has better performance compared to the conventional natural mapping. From the results, we also conclude that the choice of optimal superposition ratio values for the AWGN channel using Gray mapping of bits for two and three user scenarios results in 4-PAM and 8-PAM constellation points for the superposed modulation symbols respectively.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-68282OAI: oai:DiVA.org:liu-68282DiVA: diva2:417355