Impact of Header on Coded Slotted Aloha with Capture Among the recently proposed nonorthogonal multiple access techniques, the Coded Slotted Aloha (CSA) scheme has been identified as one of the most efficient ones. This scheme relies on the subdivision of a packet into segments and of a slot into slices, in order to enable the transmission of different segments in different slices. With respect to SA, the CSA implementation is more sophisticated, since the header of each segment must contain proper pointers specifying the slices where the other segments of that packet lie. Purpose of this paper is to investigate the impact of these pointers on the CSA throughput by properly considering the capture effect at the receiver. To this aim, a capture analysis accounting for the modulation and the header coding rate in the presence of Rayleigh fading is developed. The numerical results, which also involve a realistic millimeterwave channel, show that the beneficial interference diversity effect introduced by the segmentation process is not significantly reduced by the overhead due to the pointers, thus confirming the practical usefulness of the CSA scheme.

On the Analysis of TFold Coded Slotted ALOHA for a Fixed Error Probability In this paper we consider a Tfold coded slotted ALOHA (CSA) scheme. The main difference of this scheme in comparison to an ordinary CSA is as follows: we assume that any collisions of order up to T can be resolved. The main goal of the work is to achieve maximum throughput (the number of successfully decoded packets per slot) on condition of a fixed error probability varepsilon. A modified density evolution (DE) method was proposed and used to find an asymptotically optimal repetition count distribution for different value of T. The capacity bound has been proved for different T, admitting an error to be less than varepsilon.