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Efficient Cooperative Power and Data Transmission in Wireless Communication Networks

Haghifam, Mahdi | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49025 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Nasiri Kenari, Masoumeh; Ashtiani, Farid
  7. Abstract:
  8. Relay-assisted communication is one of the promising techniques that have been proposed for wireless networks. The main idea of a relay network is to improve data transmission efficiency by using intermediate relay nodes which support data transmission from a source to a destination. From another perspective, energy consumption has recently become an important consideration for design of wireless communication networks. The shrinking size and increasing density of next-generation wireless devices imply reduced battery capacities, indicating that designing energy efficient networks is of paramount importance. In this regard, recent emphasis on green communications has generated great interest in the energy harvesting communications and networking. It has been recently proposed to use radio-frequency (RF) signals as a means of wireless energy transfer. Significant advances in the circuit design for RF energy transfer make the usage of energy transfer as a viable and practical solution for future wireless networks. In the first part of this thesis, we investigate the outage probability and the throughput of relay networks with wireless information and energy transfer where the relays harvest energy from the transmitted radio-frequency signal of the source. Considering a practical power consumption model, we derive the outage probability for both adaptive and non-adaptive power allocations at the relay. With a total energy consumption constraint at the source, we provide closed-form expressions for the optimal time sharing and power allocation between the source energy and information transfer signals as well as the optimal relay positioning such that the outage probability is minimized. Finally, we extend our analysis to multi-relay networks. We show that with perfect channel state information (CSI) available at the relays and N relays the opportunistic relaying scheme achieves diversity order of N+1 2 . Also, we analyze the outage probability and diversity order of the opportunistic relaying with partial CSI where either the source-relay or the relay-destination CSI is provided at its corresponding transmit terminal. In the second part, we study the throughput optimization problem in a relay network composed of a source, a relay, and a destination where the relay harvests energy from the transmitted radio-frequency signal of the source. In the literature, the main focus has been on analyzing the system performance in the slot-oriented manner, in which all the harvested energy is used in the same slot in which it is harvested. Nonetheless, our results indicate that this approach is strongly suboptimal because it does not exploit the possibility to store the energy and use it efficiently at a later time. Thus, instead of considering the slot-oriented case, we analyze the system performance in a long-term approach with a battery with storage capacity. In this fashion, the throughput optimization is cast in the form of Markov decision process problems. Our objective is to address the best relay policy. Also, our analysis is based on some recent results on the achievable rates of finite-length codes. As demonstrated, employing the optimal policy by the relay significantly enhances the throughput. Moreover, using short-length packets result in better throughput performance
  9. Keywords:
  10. Cooperative Network ; Optimal Policy ; Wireless Networks ; Simultaneous Power and Data Transfer

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