Design and performance analysis of energy harvesting communications systems

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

Energy efficiency optimization with energy harvesting using harvest-use approach

Energy harvesting is emerging as a promising approach to improve the energy efficiency (EE) and to extend the life of wireless networks. This paper focuses on energy-efficient transmission power allocation techniques for a point-to-point communication channel, equipped with a fixed-power battery, as well as a harvest-use battery. Using the fact that the harvested energy does not consume from the fixed battery, EE is formulated as the ratio of Shannon limit (as a function of the sum of the power consumed from the fixed battery and the harvest-use battery) to the sum of the circuit power and power consumed from the fixed battery. For the considered energy harvest-use technique, a time switching approach is used that in each frame, the node harvests energy for a percentage of frame time and transmits data for the rest of the frame time. Using the fact that the formulated EE is a quasi-concave function in transmission power, we use fractional programming to obtain the optimal power level, Pu, and in-turn, the maximum achievable EE. Analytical derivations show that the maximum achievable EE monotonically increases with harvested power, whereas, Pu monotonically decreases with it. Simulation results show the effects of harvested energy, fixed-battery power limit, and time switching rate on the maximum achievable EE

Performance Analysis of Relaying Systems with Fixed and Energy Harvesting Batteries

This paper focuses on the performance evaluation of an energy harvesting (EH) equipped dual-hop relaying system for which the end-to-end signal-to-noise ratio (SNR) and the overall system throughput are analysed. The transmitter and the relay nodes are equipped with both fixed and EH batteries. The source for harvesting at the transmitter is the solar energy, and at the relay node, the interference energy in the radio frequency is the harvesting source. Time switching scheme is used at the relay to switch between EH and decoding information. Harvest-use approach is implemented, and we investigate the effects of the harvesting energy in enhancing the performance of the relaying system by deriving estimated closed-form expressions for the cumulative distribution function of each link’s individual SNR and of the end-to-end SNR. The analytical expression for the ergodic capacity is also derived. These expressions are validated through Monte-Carlo simulations. It is also shown that with the additional EH at the transmitter (source and relay), a significant improvement in the system throughput can be achieved when fixed batteries are running on low powers

Capacity Enhancement of High Throughput Low Earth Orbit Satellites in a constellation (HTS-LEO) in a 5G network

The global telecommunication market aims to fulfil future ubiquitous coverage and rate requirements by integrating terrestrial communications with multiple spot beam high throughput satellites (HTS). In this paper a new scheme is proposed to connect multiple Low Earth Orbit (LEO) satellites in a constellation to a single gateway to support integrated-satellite-terrestrial networks. A single gateway with multiple steerable antenna arrays is proposed for reduction in gateway numbers and cost. Using a power allocation strategy, the target is to maximize the gateway link capacity of the HTS-LEO satellites for operation including feasible used cases studies of 3GPP for necessary adaptations in a 5G system. Firstly, an objective function is established to find the optimal power levels required. Secondly the interference from neighbouring satellite beams is considered to achieve maximum capacity. Mathematical formulations are developed for this non-convex problem. Simulation results show that the proposed system architecture improves capacity and meets the dynamic demand better than traditional methods

Capacity Enhancement of High Throughput Low Earth Orbit Satellites in a constellation (HTS-LEO) in a 5G network

The global telecommunication market aims to fulfil future ubiquitous coverage and rate requirements by integrating terrestrial communications with multiple spot beam high throughput satellites (HTS). In this paper a new scheme is proposed to connect multiple Low Earth Orbit (LEO) satellites in a constellation to a single gateway to support integrated-satellite-terrestrial networks. A single gateway with multiple steerable antenna arrays is proposed for reduction in gateway numbers and cost. Using a power allocation strategy, the target is to maximize the gateway link capacity of the HTS-LEO satellites for operation including feasible used cases studies of 3GPP for necessary adaptations in a 5G system. Firstly, an objective function is established to find the optimal power levels required. Secondly the interference from neighbouring satellite beams is considered to achieve maximum capacity. Mathematical formulations are developed for this non-convex problem. Simulation results show that the proposed system architecture improves capacity and meets the dynamic demand better than traditional methods