Investigation Of Non-orthogonal Multiple Access And Related Techniques For The 5th Generation Mobile Networks

With the development of Internet of Things and mobile Internet, which brings lots of challenging requirements to fifth generation(5G) networks, such as high throughput, low latency, and much higher connectivity density. The power-domain non-orthogonal multiple access (PD-NOMA) and code-domain sparse code multiple access (SCMA) have been considered as two key and promising multiple access candidates for 5G wireless communication systems. In this thesis, some important analytical closed-form expressions and good approximated expressions of outage probability and average rate are obtained for PD-NOMA and SCMA, which will provide important insights for the design of PD-NOMA and SCMA and optimize the system parameters.Firstly, a novel dynamic power allocation scheme for PD-NOMA is proposed to im-prove users' fairness, which can more flexibly meet various quality of service requirements. The exact expressions for the outage probability and the average rate, as well as their high signal-to-noise ratio approximations, are established. Compared to the existing work-s, such as PD-NOMA with fixed power allocation and cognitive radio inspired PD-NOMA, the proposed scheme can strictly guarantee a performance gain over conventional orthogo-nal multiple access (OMA), and offer a high flexibility to realize different tradeoffs between the user fairness and system throughput.Secondly, a cooperative PD-NOMA network is considered, where a source commu-nicates with two users through an energy harvesting relay. The impact of two types of PD-NOMA power allocation policies, namely PD-NOMA with fixed power allocation (F-NOMA) and cognitive radio inspired PD-NOMA (CR-NOMA), on the considered co-operative simultaneous wireless information and power transfer (SWIPT) system, is in-vestigated. Particularly, closed-form expressions for the outage probability and their high signal-to-noise ratio (SNR) approximations are derived to characterize the performance of SWIPT-F-NOMA and SWIPT-CR-NOMA. These developed analytical results demon-strate that the two power allocation policies realize different tradeoffs between the recep-tion reliability, user fairness and system complexity. Compared to conventional SWIPT relaying networks with OMA, the proposed PD-NOMA schemes can effectively reduce the outage probability, although all of them realize the same diversity gain.Thirdly, a downlink single-cell PD-NOMA network with uniformly deployed users is considered and an analytical framework to evaluate its performance is developed. Partic-ularly, the performance of PD-NOMA is studied by assuming two types of partial channel state information (CSI). For the first one, which is based on imperfect CSI, we present a simple closed-form approximation for the outage probability and the average sum rate, as well as their high SNR expressions. For the second type of CSI, which is based on the second order statistics (SOS), we derive a closed-form expression for the outage probabil- ity and an approximate expression for the average sum rate for the special case two users. For the addressed scenario with the two types of partial CSI, the results demonstrate that PD-NOMA can achieve superior performance compared to the traditional OMA. More-over, SOS-based PD-NOMA always achieves better performance than that with imperfect CSI, while it can achieve similar performance to the PD-NOMA with perfect CSI at the low SNR region.Fourthly, we analyse the average sum rate of uplink sparse code multiple access (SC-MA) in a regular hexagon cell with uniformly distributed users. The developed analytical results show that SCMA can achieve higher average sum rate than orthogonal frequen-cy division multiple access systems. Next, assume that the distances between mobile users and base station are fixed but not necessarily identical, and investigate the relation-ship between graph matrix and the ergodic sum rate for SCMA systems. The developed analytical results show that assigning orthogonal resources to the adjacent users can op-timize the sum rate of SCMA systems. Moreover, we propose a low complexity iterative algorithm to facilitate the design of the optimal graph matrix.Finally, we consider a cloud radio access networks (C-RAN) system in which base stations are uniformly distributed inside a disk. The outage probability and the ergodic rate achieved by this C-RAN system are analysed. Compared to the existing studies, more accurate analytical results are developed by applying the Gaussian-Chebyshev in-tegration. Besides, we also consider an underlay cognitive radio (CR) networks with one primary receiver, one cognitive transmitter-receiver pair, and one energy harvesting re-lay. The relay transmission is powered by the energy harvested from the radio frequency observations at the relay. For the considered CR networks with SWIPT, we derive ana-lytical expressions for the outage probability, as well as their high SNR approximations in closed-form. The developed analytical results demonstrate that the use of SWIPT can achieve the same diversity gain as a conventional CR network.