Exploiting capture and interference cancellation for uplink random multiple access in 5G millimeter-wave networks

The forthcoming 5G technology aims to provide massive device connectivity and ultra-high capacity with reduced latency and costs. These features will be enabled by increasing the density of the base stations, using millimeter-wave (mmWave) bands, massive multiple-input multiple-output systems, and non-orthogonal multiple access techniques. The ability to support a large number of terminals in a small area is in fact a great challenge to guarantee massive access. In this context, this paper proposes a new receiver model for the uplink of 5G mmWave cellular networks. The receiver, called Iterative Decoding and Interference Cancellation (IDIC), is based on the Slotted Aloha (SA) protocol and exploits the capture effect alongside the successive IC process to resolve packet collisions. A 5G propagation scenario, modeled according to recent mmWave channel measurements, is used to compare IDIC with the widely adopted Contention Resolution Diversity SA (CRDSA) scheme to show the performance gain of IDIC, when elements of practical relevance, like imperfect cancellation and receive power diversity, are considered. The impact of packet and power diversity is also investigated to derive the preferable uplink random access strategy that maximizes the system throughput according to the offered channel load.

     

Considerations on adaptive techniques for time-divisionmultiplexing radio systems

This paper addresses the problem of providing a fair comparison among the performance of the different techniques that adapt the transmission parameters, such as the modulation, power, and bit rate, to the channel characteristics. A coordinated time-division multiplexing (TDM) scheme is adopted. Both an isolated cell scenario and a cellular system scenario are taken into consideration. In the single-cell case, closed-form expressions of the optimum power and modulation adaptation law are found. It is shown that the examined techniques offer a similar performance in most cases, although modulation adaptation is somewhat superior to power control in the cellular case. It is made clear that the improvement obtained by adopting an adaptive technique should not be evaluated without specifying the acceptable consequences on service distribution because it is the service distribution that determines the achievable gain ultimately. Previously, a new wireless access system, called Infostations, has been proposed which provides isolated pockets of high-bandwidth connectivity for future data and messaging services. Although the main considerations hold in general, they are particularly useful for defining a time multiplexing scheme for Infostations