Joint Transceiver Design For Muti-user SWIPT Systems

Green radio has been an important research topic under the pressure of energy crisis and environmental pollution. Besides energy saving, efficient utilization of new energy sources is also an important way to realize green radio. As a potential green energy source, radio signal can be used to simultaneously transmit information and power. Therefore, it is of great importance to investigate the communication system with the capability of simultaneous wireless information and power transfer(named SWIPT system) and its efficient transmission technology. This dissertation considers a power splitting(PS)-based multi-user multiple-input-single-output(MISO) downlink system with simultaneous wireless information and power transfer, where each single antenna receiver splits the received signal into two streams of different power for decoding information and harvesting energy separately. By using some advanced mathematical optimization tools, this thesis investigates joint transmit beamforming and power splitting(JBPS) schemes for the considered multi-user SWIPT systems, including:(1) Low Complexity JBPS for Achieving Transmission power minimization: this thesis first investigates JBPS to minimize the transmission power at base station while satisfying both signal-to-interference-plus-noise ratio(SINR) constraints and energy harvesting constraints.Considering the existing SDR-based approach has high complexity, this thesis proposes a weighted MRC-ZF based low complexity transceiver design. The simulation results verify that the proposed low complexity design method could achieve nearly optimum performance.(2) JBPS for Achieving Harvested Power Maximization: As compared to the traditional communication systems, one of design goals for SWIPT system is to achieve harvested power maximization. To this end, this thesis studies harvested power maximization while satisfying the SINR constraints. Considering the high nonlinearity of the SINR and energy harvesting functions, the harvested power maximization problem is transformed to a series of convex problems based on the idea of constraint concave-convex procedure, which is iteratively solved.Meanwhile, this thesis also proposes zero-forcing based low complexity harvested power maximization scheme with a numerical comparison with the CCCP-based scheme.(3) JBPS for Achieving Energy Efficiency Maximization. As a green measure of communication systems, energy efficiency is also important for the SWIPT systems. The energy efficiency optimization problem is highly nonconvex. To solve this problem, this thesis proposes using CCCP to deal with the nonconvexity of both the SINR and EH functions and the coupling of the PS ratios. For general MISO SWIPT systems, this thesis develops a WMMSE and CCCP based iterative JBPS algorithm. Meanwhile, a ZF-based energy efficiencyoptimization problem is considered with a simple solution using Lagrange relaxation. In addition, this thesis proposes a low complexity transceiver design approach by adopting proportional power allocation scheme. Numerical results illustrates the energy efficiency of the proposed algorithms.