Full duplex-transceivers : architectures and performance analysis

PhD ThesisThe revolution of the 5G communication systems will result in 10,000 times increase in the total mobile broadband traffic in the 2020s, which will increase the demand on the limited wireless spectrum. This has highlighted the need for an efficient frequency-reuse technique that can meet the ever-increasing demand on the available frequency resources. In-band full-duplex (FD) wireless technology that enables the transceiver nodes to transmit and receive simultaneously over the same frequency band, has gained tremendous attention as a promising technology to double the spectral efficiency of the traditional half-duplex (HD) systems. However, this technology faces a formidable challenge, that is the large power difference between the self-interference (SI) signal and the signal of interest from a remote transceiver node. In this thesis, we focus on the architecture of the FD transceivers and investigate their ability to approximately double the throughput and the spectral efficiency of the conventional HD systems. Moreover, this thesis is concerned with the design of efficient self-interference cancellation schemes that can be combined with the architecture of the FD transceiver nodes in order to effectively suppress the SI signal and enable the FD mode. In particular, an orthogonal frequency-division multiplexing (OFDM) based amplify-and-forward (AF) FD physical-layer network coding (PLNC) system is proposed. To enable the FD mode in the proposed system, a hybrid SIC scheme that is a combination of passive SIC mechanism and active SIC technique is exploited at each transceiver node of that system. Next, we propose an adaptive SIC scheme, which utilizes the normalized least-mean-square (NLMS) algorithm to effectively suppress the SI signal to the level of the noise floor. The proposed adaptive SIC is then utilized in a denoise-and-forward (DNF) FD-PLNC system to enable the FD mode. Finally, we introduce a novel overthe- air SIC scheme that can effectively mitigate the SI signal before it arrives the local analog-to-digital converter (ADC) of the FD transceiver nodes. Furthermore, the impact of the hardware impairments on the performance of the introduced SIC scheme is examined and characterized.Iraq, and the Ministry of Higher Education and Scientific Research (MOHSR

A Tutorial on Nonorthogonal Multiple Access for 5G and Beyond

Today's wireless networks allocate radio resources to users based on the orthogonal multiple access (OMA) principle. However, as the number of users increases, OMA based approaches may not meet the stringent emerging requirements including very high spectral efficiency, very low latency, and massive device connectivity. Nonorthogonal multiple access (NOMA) principle emerges as a solution to improve the spectral efficiency while allowing some degree of multiple access interference at receivers. In this tutorial style paper, we target providing a unified model for NOMA, including uplink and downlink transmissions, along with the extensions tomultiple inputmultiple output and cooperative communication scenarios. Through numerical examples, we compare the performances of OMA and NOMA networks. Implementation aspects and open issues are also detailed.Comment: 25 pages, 10 figure

Efficient Power Allocation Schemes for Hybrid Decode-Amplify-Forward Relay Based Wireless Cooperative Network

Cooperative communication in various wireless domains, such as cellular networks, sensor networks and wireless ad hoc networks, has gained significant interest recently. In cooperative network, relays between the source and the destination, form a virtual MIMO that creates spatial diversity at the destination, which overcomes the fading effect of wireless channels. Such relay assisted schemes have potential to increase the channel capacity and network coverage. Most current research on cooperative communication are focused broadly on efficient protocol design and analysis, resource allocation, relay selection and cross layer optimization. The first part of this research aims at introducing hybrid decode-amplify-forward (HDAF) relaying in a distributed Alamouti coded cooperative network. Performance of such adaptive relaying scheme in terms of symbol error rate (SER), outage probability and average channel capacity is derived theoretically and verified through simulation based study. This work is further extended to a generalized multi HDAF relaying cooperative frame work. Various efficient power allocation schemes such as maximized channel capacity based, minimized SER based and total power minimization based are proposed and their superiority in performance over the existing equal power allocation scheme is demonstrated in the simulation results. Due to the broadcast nature of wireless transmission, information privacy in wireless networks becomes a critical issue. In the context of physical layer security, the role of multi HDAF relaying based cooperative model with control jamming and multiple eavesdroppers is explored in the second part of the research. Performance evaluation parameters such as secrecy rate, secrecy outage and intercept probability are derived theoretically. Further the importance of the proposed power allocation schemes in enhancing the secrecy performance of the network in the presence of multiple eavesdroppers is studied in detail through simulation based study and analysis. For all the proposed power allocation schemes in this research, the optimization problems are defined under total power constraint and are solved using Lagrange multiplier method and also evolutionary algorithms such as Differential evolution and Invasive Weed Optimization are employed. Monte Carlo simulation based study is adopted throughout the research. It is concluded that HDAF relaying based wireless cooperative network with optimal power allocation schemes offers improved and reliable performance compared to conventional amplify forward and decode forward relaying schemes. Above research contributions will be applicable for future generation wireless cooperative networks

Multiple antenna communication over fading channels : Performance limits and cooperative transmission strategies

Ph.DDOCTOR OF PHILOSOPH