Abstract
A K-user multi-rate code is proposed for a Gaussian multiple access channel with binary inputs, equal-power, and symbol synchronisation. In this multi-rate transmission, K users are equally divided into M groups. For each user in the mth group, a rate- 1 / q m regular repeat-accumulate code serially concatenated with a length- L m spreading is employed. The transmitted rate of each user in the mth group is 1 / ( q m L m ) . At the receiver, iterative joint decoding (IJD) and hybrid interference cancellation (HIC) schemes are considered. For each decoding scheme, a bivariate fixed-point analysis is applied to explicitly represent ( q m , L m ) as a function of mutual information outputs. On the basis of these basic explicit representations, a united unreliable region is given, where users in at least one group are undecodable. The complementary set of the united unreliable region gives an optimal rate profile that achieves the maximum sum rate. Numerical results show that, for the IJD scheme with M increments, the maximum sum rate increases, approaches the Shannon limit, and exceeds that in conventional equal rate transmission. The maximum sum rate of the HIC scheme, which provides much lower decoding complexity than the IJD scheme, is superior to the conventional successive interference cancellation scheme.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call