Design and performance analysis of energy harvesting communications systems
Creators: name: Siddiqui, Arooj Mubashara
Publisher: name: Lancaster University
Year: 2017

description: The continuous growth of high data rates with huge increase in the number
      of mobile devices and communication infrastructure have led to greenhouse
      gas emission, higher pollution and higher energy costs. After the
      deployment of 4G and immense data rate and QoS requirements for 5G, there
      is an urgent need to design future wireless systems that aim to improve
      energy efficiency (EE) and spectral efficiency (SE). One of the possible
      solutions is to use energy harvesting (EH), which promises to reduce
      energy consumption issues in information and communication technology
      sector. In order to tackle these challenges, this thesis is focused on the
      design and performance analysis of EH systems. EH has emerged as a
      potential candidate for green wireless communication which not only
      provides solution to the energy limitation problem but also prolongs the
      lifetime of batteries.
      
      First, the performance evaluation of an EH-equipped dual-hop relaying
      system is proposed to improve the system throughput and the end-to-end
      signal-to-noise ratio (SNR). We derive novel closed-form expressions for
      cumulative distribution function of individual link's SNR and of the
      end-to-end SNR. In addition, the proposed model analyses the ergodic
      capacity which is an important performance metric for delay-sensitive
      services. Further, these closed-form expressions reduce the computational
      complexity of the receiver architecture for practical systems. An insight
      through system parameters provide significant improvement in end-to-end
      SNR especially when both transmitter and relay nodes are equipped with
      harvesting sources.
      
      Second, performance analysis and optimal transmission power allocation
      techniques for EH-equipped system are studied. Our proposed model
      investigates and provides the conditions under which the harvesting can
      improve the system performance. In this work, novel closed-form
      expressions are calculated for the maximum achievable EE, SE and EH
      beneficialness condition. We studied two cases such as power is adapted to
      variations in the channel and when transmit power is fixed. We proved that
      EE-optimum input power decreases with EH power level. Also, system
      parameters demonstrate the conditions under which EH improves overall
      system performance.
      
      Finally, a multi-objective optimization problem is formulated that jointly
      maximizes EE and SE for point-to-point EH-equipped system. We introduce
      new importance weight which set the priority levels of EE versus SE of the
      system. The formulated problem is solved by using convex optimization
      method to achieve optimal solution. The proposed system model provides
      freedom to choose any value for importance weight to satisfy quality of
      service (QoS) requirements and the flexibility of balancing between EE and
      SE performance metrics.