Analysis of Downlink Connectivity in NB-IoT Networks Employing NOMA with Imperfect SIC

Abstract

We study the problem of maximizing the number of served devices in a non-orthogonal multiple access (NOMA) based Narrowband Internet of Things (NB-IoT) network for supporting massive connectivity in the downlink. We analyze this problem under practical system limitations of imperfect successive interference cancellation (SIC) at the receiver along with data rate, power and bandwidth constraints. We propose a strategy for joint device and power allocation through an iterative solution for a system of linear equations on each sub-carrier that maximizes the number of connected devices. We evaluate the performance of the proposed solution over a wide range of service scenarios through extensive computer simulations and demonstrate the sensitivity of connectivity in power domain NOMA based NB-IoT systems to the residual interference resulting from imperfect SIC.

Maximizing Downlink User Connection Density in NOMA-aided NB-IoT Networks Through a Graph Matching Approach

“…We employ the non-orthogonal multiple access (NOMA) technique, comprising of superposition coding at the transmitter, which is the base station (BS) in our scenario considering the downlink. Successive interference cancellation (SIC) is used at the receiver [3], which is the user equipment (UE). There has been some studies regarding the uplink connectivity, most notably the authors in [4] develop a convex optimization based heuristic framework to show the connectivity gains achieved by NOMA in an NB-IoT system.…”