Beam forming for energy harvesting and multi-user communications

Demir, Özlem Tuğfe
In this thesis, several optimization problems are considered related to beamforming for energy harvesting and multi-user communications. In multi-user communications scenarios, physical layer multi-group multicasting systems are considered where there are multiple groups of users who are interested in common information signals. In energy harvesting related scenarios, different protocols are investigated, namely power splitting and self-energy recycling, respectively. In power splitting mode, the mobile device has a power splitting device and some portion of the received radio frequency power is used for energy harvesting while the remaining part is used for information decoding. In self-energy recycling protocol, a separate receive antenna on the relay uses the transmitted signal as an energy source. The contributions of this thesis can be outlined as follows. First, efficient algorithms are proposed for antenna selection and hybrid beamforming in multi-group multicasting systems. The users have a power splitting device and the joint optimization of transmit beamformers and power splitting ratios is considered. Multi-group multicasting is also used for OFDM systems where users harvest energy from some portion of the received signal. The difficult combinatorial problem for the joint optimization of resource allocation and power splitting ratios is solved effectively. In addition, several fast algorithms are proposed for full digital beamforming and two different hybrid beamforming structures with per-antenna power constraints. Apart from multi-group multicasting, relay assisted single user communications is also studied in this thesis. Several scenarios are investigated for energy harvesting relays which use power splitting and self-energy recycling protocols. Both amplify-and-forward and decode-and-forward relaying protocols are considered. For most of the problems, optimum solutions are obtained while for the others, efficient near-optimum solutions are presented.


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Citation Formats
Ö. T. Demir, “Beam forming for energy harvesting and multi-user communications,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.