Threshold-Based Edge Selection MPA for SCMA
Abstract
Abstract—Sparse Code Multiple Access (SCMA) has been
proposed for the newest generation of communication systems,
considering overloaded non-orthogonal multiple access. To deal
with the overload, SCMA exploits the sparsity feature with
the aid of receivers based on the messsage-passing algorithm
(MPA). In this paper, we review a low-complexity MPA receiver
based on edge selection and gaussian approximation (ESGA). We
improve this receiver by proposing a threshold-based criterion for
the edge selection (TB-ESGA). With the threshold, the number
of interfering neighbors considered in the calculation of each
message of the MPA becomes a random variable. We derive the
probability of selecting a given number of edges in our strategy
and also an expression for the average complexity order, as
a function of the threshold. We also show that the proposed
threshold results in a better trade-off between complexity and
error-rate performance.