Study of IoT Networks Inspired by the Emerging NOMA Technique: Analysis, Simulations and Improvements

Abstract

The dissertation deals with the study of internet of things (IoT) networks inspired by the non-orthogonal multiple access (NOMA) technique, which is a key technology in next-generation wireless communication networks. An ever growing number of IoT devices require large connections, low latency and locations which depend on variable environments such those found in ad hoc and opportunistic networks.

First, I designed a novel multi-points cooperative relay (MPCR) NOMA model, in which the base station (BS) selects the nearest user equipment (UE) and sends a superposed signal to this UE as the first relay node, the selection is performed on the basis of the channel state information (CSI). The network contains N UE, and the N-th UE, which is farthest from the BS and has the poorest CSI from the BS compared other UE. The N-th UE receives a forwarded signal from N-1 relaying nodes which consist of UE with better CSI. At the i-th (i in N) relaying node, it detects its own message by using successive information cancelation (SIC) and then forwards the superimposed signal to the next nearest UE, namely the (i + 1)-th UE, and includes an excess power which will be used to energy harvesting (EH) at the next UE. Through this process, the performance of the farthest UE in a network can be significantly improved.

Next, I examined various forwarding protocols, i.e., decode-and-forward (DF), amplify-and-forward (AF) with fixed gain (FG) or variable gain (VG). Then, I designed a multiple protocol switching selection (PSS) framework over cooperative-NOMA (C-NOMA) networks to minimize the outage probability (OP) and maximize the system throughput and energy efficiency (EE). The dissertation investigates six scenarios, i.e., a C-NOMA system with paired (i) half-duplex (HD) and DF; (ii) full-duplex (FD) and DF; (iii) HD and AF with FG; (iv) HD and AF with VG; (v) FD and AF with FG; and (vi) FD and AF with VG protocols at the relay. The PSS framework selects the transmission scenario which provides the best system performance.

Finally, I designed an ultra-low latency and low energy IoT network inspired by the emerging C-NOMA technique. The IoT network model consists of a source at the center of the network, a near device inside the network, and a far device outside the network. I deployed the near device as a relay to assist the far device. The near device is assumed to be a low energy node. As a result, the near device cannot forward signals to the far device through its own power. I therefore design the IoT network to apply the simultaneous wireless information and power transfer (SWIPT) technique so that the near device can harvest energy and use it to forward signals. Two cooperative IoT network scenarios are examined: (i) HD and (ii) FD relaying, each with and without eavesdroppers. The designed power splitting (PS) framework exploits PS factors for fairness in the quality of service (QoS) for the devices. Novel analysis expressions were obtained for accurate and approximate closed-forms of OP, secrecy OP (SOP), system throughput and Jain's fairness index.