  In this paper, by considering multiple slices, a downlink transmission of a
sparse code multiple access (SCMA) based cloud-radio access network (C-RAN) is
investigated. In this regard, by supposing multiple input and single output
(MISO) transmission technology, a novel robust radio resource allocation is
proposed where considering uncertain channel state information (CSI), the worst
case approach is applied. The main goal of the proposed radio resource
allocation is to, maximize the system sum rate with maximum available power at
radio remote head (RRH), minimum rate requirement of each slice, maximum
frounthaul capacity of each RRH, user association, and SCMA constraints. To
solve the proposed optimization problem in an efficient manner, an iterative
method is deployed where in each iteration, beamforming and joint codebook
allocation and user association subproblem are solved separately. By
introducing some auxiliary variables, the joint codebook allocation and user
association subproblem is transformed into an integer linear programming, and
to solve the beamforming optimization problem, minorization-maximization
algorithm (MMA) is applied. Via numerical results, the performance of the
proposed system model versus different system parameters and for different
channel models are investigated.
