In this paper, we present a few novel simultaneous wireless information and power transfer (SWIPT) schemes that can be effectively used in various 5G wireless network implementations. First, we study the possibility of integrating distributed energy beamforming with the data rate fairness beamforming in a cooperative communication system with multiple cooperative relays and multiple destination users communicating simultaneously. We show that the system exploits significant performance gain using such a joint energy and data rate fairness beamforming scheme. Further, we propose an enhanced version of the SWIPT scheme, the energy-efficient modulation-based non-orthogonal multiple access (M-NOMA) SWIPT scheme, and observe its system efficiency in terms of more harvested energy. Finally, we consider an energy-harvesting SWIPT scheme where the channel response is estimated using the energy-harvesting signal as pilots superimposed on the information signal. For such a scheme, we compute the optimum transmit power ratio between the pilot and information signals under varying SNR conditions and improve the accuracy of the decoding process at the reception.

Fiber nonlinearity is the bottleneck of optical communication systems and is commonly addressed by applying various nonlinearity mitigation and compensation techniques. In general, nonlinearity mitigation techniques offer modest improvements with minimal computational complexity, while nonlinearity compensation techniques provide significant performance gains at the expense of higher computational complexity. This motivates us to propose a joint nonlinearity mitigation and compensation approach in which the nonlinear effects during signal propagation are reduced to compensate for the residual nonlinearity at a lower complexity. Specifically, in this paper, we study the combination of symbol rate optimization (SRO) and perturbation-based nonlinearity compensation (PB-NLC) for a pre-chromatic dispersion compensated (pre-CDC) transmission of polarization multiplexing, digital sub-carrier multiplexing, and wavelength division multiplexing (PM-DSCM-WDM) optical communication system. We highlight the interplay between SRO and PB-NLC and demonstrate that joint SRO and PB-NLC provides considerable performance gain, significant complexity reduction, and an additional degree of freedom to balance performance-complexity trade-offs when compared to applying only PB-NLC in a conventional PM-WDM system. We observe that the pre-CDC transmission manifests a unique property that enables the distribution of PB-NLC computational complexity between transmitter and receiver. Leveraging the distinctive property, we propose a split PB-NLC technique for the PM-DSCM-WDM system. This technique combines the benefits of both pre-PB-NLC and post-PB-NLC, resulting in a modest performance improvement while maintaining the same computational complexity as post-PB-NLC.

This paper considers a wireless power transfer enabled cooperative communication system where the end-users (EUs) make use of WPT to send energy to intermediate RUs to receive information. In traditional cooperative communications systems, service provider provides the energy for cooperation and the networks are optimized from the service providers’ perspectives. In the this system, EUs compensate for the energy requirements of RUs, and EUs should get a fair service back from RUs. To administrate EUs WPT and ensure the fair service policy, this proposes a novel beamforming technique named Pay-As-You-Go beamforming. This adapts data rates proportional to the amount of energy received from each EUs while optimizing the energy per bit cost of the overall system. Then formulated as an non convex optimization problem and solved with the semi-definite programming relaxation techniques.

Nonlinear phase noise in a fiber optical communication system with 16 Quadrature Amplitude Modulation (16-QAM) has been analyzed in this work. Three new constellation schemes are compared with the post compensation using mean shift rotation method. The new constellations focus on optimizing the ratio between the amplitudes in the 16-QAM and placing the points of 16-QAM in different patterns to minimize the effect of the nonlinear phase noise. In previous works, the best performance was achieved with circular constellation without any additional compensation techniques. The performance is improved by improved circular constellation with optimized radii, five shells circular constellation and improved five-shell circular constellation in this work. The improved five-shell circular constellation diagram improves the bit error rate performance by one order of magnitude from the existing circular constellation at the transmission distance of 3000 km. This result is due to the fact that moderate amplitude signals are more tolerance to nonlinear phase noise.

Asymmetry in average channel conditions is a challenging factor in two-way relay communication (TWRC) system in order to obtain a balanced performance at two end nodes. In this paper, for a coded TWRC system, we consider hierarchical modulation and network coding assisted bit interleaved coded modulation (HMNC-BICM) based system. The performance of the considered HMNC-BICM based system is compared with the bidirectional network coding assisted traditional bit-interleaved coded modulation (BNC-BICM) based system that uses regular signal constellations and a single interleaver. The presented simulation results show that the HMNC-BICM system not only provides the flexibility of having same reliability at both end nodes but also it has a superior performance in terms of average BER in an asymmetric TWRC system.

In this paper, we develop a data rate fairness optimal cooperative beamforming technique for a cognitive radio system with multiple secondary receivers (SRs) and multiple primary receivers (PRs) in the presence of asynchronous interferences. In particular, the data rate fairness beamforming design is formulated as an optimization problem to maximize the minimum data rate of the SRs subject to transmission power constraints at the secondary cooperative transmitters (SCTs) and asynchronous interference power constraints at the PRs. The optimal beamforming design is a quadratically constrained quadratic program max-min optimization problem, which is non-convex and non-linear. Therefore, we reformulate the optimal beamforming design as a quasi-convex problem using the semidefinite program (SDP) relaxation, which can be solved using the SDP solvers and bisection method. The complexity of the optimal beamforming scheme stands against its practical implementation. So, we study important properties of the optimization problem. By exploiting these properties, we also propose low complexity suboptimal beamforming techniques. Furthermore, we extend the beamforming techniques to incorporate the uncertainties in channel and propagation delay estimation between SCTs and PRs.