Joint Transmission and Energy Transfer Policies for Energy Harvesting Devices with Finite Batteries

One of the main concerns in traditional Wireless Sensor Networks (WSNs) is energy efficiency. In this work, we analyze two techniques that can extend network lifetime. The first is Ambient \emph{Energy Harvesting} (EH), i.e., the capability of the devices to gather energy from the environment, whereas the second is Wireless \emph{Energy Transfer} (ET), that can be used to exchange energy among devices. We study the combination of these techniques, showing that they can be used jointly to improve the system performance. We consider a transmitter-receiver pair, showing how the ET improvement depends upon the statistics of the energy arrivals and the energy consumption of the devices. With the aim of maximizing a reward function, e.g., the average transmission rate, we find performance upper bounds with and without ET, define both online and offline optimization problems, and present results based on realistic energy arrivals in indoor and outdoor environments. We show that ET can significantly improve the system performance even when a sizable fraction of the transmitted energy is wasted and that, in some scenarios, the online approach can obtain close to optimal performance.Comment: 16 pages, 12 figure

Energy Harvesting Wireless Communications: A Review of Recent Advances

This article summarizes recent contributions in the broad area of energy harvesting wireless communications. In particular, we provide the current state of the art for wireless networks composed of energy harvesting nodes, starting from the information-theoretic performance limits to transmission scheduling policies and resource allocation, medium access and networking issues. The emerging related area of energy transfer for self-sustaining energy harvesting wireless networks is considered in detail covering both energy cooperation aspects and simultaneous energy and information transfer. Various potential models with energy harvesting nodes at different network scales are reviewed as well as models for energy consumption at the nodes.Comment: To appear in the IEEE Journal of Selected Areas in Communications (Special Issue: Wireless Communications Powered by Energy Harvesting and Wireless Energy Transfer

Optimal Sensing and Transmission in Energy Harvesting Sensor Networks

Sensor networks equipped with energy harvesting (EH) devices have attracted great attentions recently. Compared with conventional sensor networks powered by batteries, the energy harvesting abilities of the sensor nodes make sustainable and environment-friendly sensor networks possible. However, the random, scarce and non-uniform energy supply features also necessitate a completely different approach to energy management. A typical EH wireless sensor node consists of an EH module that converts ambient energy to electrical energy, which is stored in a rechargeable battery, and will be used to power the sensing and transmission operations of the sensor. Therefore, both sensing and transmission are subject to the stochastic energy constraint imposed by the EH process. In this dissertation, we investigate optimal sensing and transmission policies for EH sensor networks under such constraints. For EH sensing, our objective is to understand how the temporal and spatial variabilities of the EH processes would affect the sensing performance of the network, and how sensor nodes should coordinate their data collection procedures with each other to cope with the random and non-uniform energy supply and provide reliable sensing performance with analytically provable guarantees. Specifically, we investigate optimal sensing policies for a single sensor node with infinite and finite battery sizes in Chapter 2, status updating/transmission strategy of an EH Source in Chapter 3, and a collaborative sensing policy for a multi-node EH sensor network in Chapter 4. For EH communication, our objective is to evaluate the impacts of stochastic variability of the EH process and practical battery usage constraint on the EH systems, and develop optimal transmission policies by taking such impacts into consideration. Specifically, we consider throughput optimization in an EH system under battery usage constraint in Chapter 5

Enerji hasadı yapan kablosuz ağlarda kullanıcı işbirliği ve kaynak tahsisi

Yeni nesil haberleşme sistemlerinde, pillere ya da şehir elektriğine bağımlı olarak çalışan klasik haberleşme bileşenlerinin yerlerini, enerjilerini çevreden hasat eden, çevreye duyarlı ve uzun kullanım ömrüne sahip bileşenlere bırakacağı öngörülmektedir. Bu nedenle, bilinen haberleşme protokollerinin, enerjinin aralıklı olarak geldiği, ve gönderilerin anlık enerji kısıtlarına tabi olduğu durumlara uygun olarak baştan ele alınması, ve enerji hasadı koşulları altında kuramsal performans üst limitlerinin baştan belirlenmesi gerekmektedir. Bu projede, tüm enerjilerini doğadan hasat eden işbirlikli haberleşme ağlarında, kaynakları etkin kullanarak ağ performansını artıran ve ömrünü uzatan gönderim protokolleri tasarlanmıştır. Böylece, işbirlikli kablosuz ağlarda basit çoklu erişim ya da aktarım kanal modellerinin ötesine geçilmiş; farklı kullanıcılarda anlık olarak farklı miktarlarda biriktirilen enerjinin beraberinde getirdiği enerji çeşitleme kazancı ile işbirliği kazancından bir arada faydalanılması sağlanmıştır. Düğümlerin kendi enerjilerini iletim sırasında çevrelerinden temin ettikleri, ve biribirleri ile gerek veri, gerekse enerji aktarımı ile yardımlaşabildikleri durumlar için, • Bilgi kuramsal bir yaklaşım kullanılarak, gerek gecikme kısıtlı, gerekse gecikmeye toleranslı durumlar için, blok Markov kodlama ve geriye doğru kodçözme tabanlı yeni işbirlikli kodlama teknikleri geliştirilmiş, ve karşılık gelen erişilebilir veri hızları elde edilmiş, • Toplam veri hızı veya veri gönderim bölgelerini enbüyükleyen kaynak tahsisi algoritmaları geliştirilmiş, • Hasat edilen enerji ve kanal durumlarının gönderim, aktarım, ya da enerjinin depolanması kararlarını nasıl etkilediği incelenmiş, temel bazı ödünleşimler belirlenmiş, • Verinin ve hasat edilen enerjinin gönderi devam ederken aralıklı geldiği durumda en iyi veri hızı ve güç çizelgelemesi bulunmuş, • İşbirlikli haberleşme için kritik olan, hem alıcı hem de verici olarak davranan düğümlerdeki kodçözme maliyeti kısıtları dikkate alınarak işbirliğinden net kazancı eniyileyen politikalar geliştirilmiş, • Düğümlerin biribirlerine enerji de gönderebildikleri durumda, işbirlikli veri iletişimi ile enerji transferi yoluyla işbirliği senaryoları birlikte incelenip, en iyi kaynak tahsisi stratejisi belirlenmiş, • Hasat edilen kaydedildiği bataryaların sınırlı kapasitesi olması durumunda gelen enerjinin ziyan edilmemesini garanti eden en iyi kaynak yönetimi algoritmaları önerilmiştir. Elde edilen sonuçlar, gerek veri, gerekse enerji işbirliğinin, enerji hasat eden sistemlerde, özellikle enerji çeşitlemesinden kazanç sağlamak için çok faydalı yaklaşımlar olduğuna işaret etmektedir.In new generation wireless systems, traditional communication components which rely on batteries or the electrical grid are expected to ve replaced by more environment-conscious, energy harvesting components with longer lifetime. Therefore, known communication protocols need to be reconsidered from scratch to adapt to situations where the transmissions are subject to instantaneous energy constraints caused by intermittent energy arrivals, and their theoretical performance upper bounds need to be re-derived under energy harvesting constraints. In this project, we design transmission protocols that maximize the network performance and lifetime by efficiently allocating resources, for communication networks that rely only on energy harvested from their surroundings. We go beyond simple multiple access or relay models, and jointly take advantage of the energy diversity provided by the variable nature of the energy arrivals at different users, and cooperative diversity. For scenarios where the nodes harvest their own enery during transmission, and are able to cooperate both at data and battery level, • we approach the system from an information theoretic perspective and develop new encoding and decoding techniques, based on block Markov coding and backward decoding, that can be used in delay constrained and delay tolerant communication; and characterize their achievable rates, • we develop resource allocation algorithms that maximize the total rate or departure region, • we investigate the effect of energy arrival profiles and channel qualities on transmission, bi-directional relaying and energy saving decisions, and determine some fundamental tradeoffs, • we find the optimal power and rate scheduling policy when data, as well as energy arrives intermittently during transmission, • we obtain the optimal policies that maximize the net gain from cooperation, taking into account the decoding costs at the transceiver nodes, • we develop jointly optimal energy and data cooperation strategies, when energy can be exchanged wirelessly • we propose scheduling optimization algorithms that guarantee that energy is not wasted, taking into account practical battery limitations at the energy harvesting nodes. The results obtained point to the conclusion that data and energy cooperation are significantly useful approaches that take advantage of the inherent energy diversity provided by the energy harvesting communication systems.TÜBİTA

Resource Allocation in Energy Cooperation Enabled 5G Cellular Networks

PhD thesisIn fifth generation (5G) networks, more base stations (BSs) and antennas have been deployed to meet the high data rate and spectrum efficiency requirements. Heterogeneous and ultra dense networks not only pose substantial challenges to the resource allocation design, but also lead to unprecedented surge in energy consumption. Supplying BSs with renewable energy by utilising energy harvesting technology has became a favourable solution for cellular network operators to reduce the grid energy consumption. However, the harvested renewable energy is fluctuating in both time and space domains. The available energy for a particular BS at a particular time might be insufficient to meet the traffic demand which will lead to renewable energy waste or increased outage probability. To solve this problem, the concept of energy cooperation was introduced by Sennur Ulukus in 2012 as a means for transferring and sharing energy between the transmitter and the receiver. Nevertheless, resource allocation in energy cooperation enabled cellular networks is not fully investigated. This thesis investigates resource allocation schemes and resource allocation optimisation in energy cooperation enabled cellular networks that employed advanced 5G techniques, aiming at maximising the energy efficiency of the cellular network while ensuring the network performance. First, a power control algorithm is proposed for energy cooperation enabled millimetre wave (mmWave) HetNets. The aim is to maximise the time average network data rate while keeping the network stable such that the network backlog is bounded and the required battery capacity is finite. Simulation results show that the proposed power control scheme can reduce the required battery capacity and improve the network throughput. Second, resource allocation in energy cooperation enabled heterogeneous networks (Het- Nets) is investigated. User association and power control schemes are proposed to maximise the energy efficiency of the whole network respectively. The simulation results reveal that the implementation of energy cooperation in HetNets can improve the energy efficiency and the improvement is apparent when the energy transfer efficiency is high. Following on that, a novel resource allocation for energy cooperation enabled nonorthogonal multiple access (NOMA) HetNets is presented. Two user association schemes which have different complexities and performances are proposed and compared. Following on that, a joint user association and power control algorithm is proposed to maximise the energy efficiency of the network. It is confirmed from the simulation results that the proposed resource allocation schemes efficiently coordinate the intra-cell and inter-cell interference in NOMA HetNets with energy cooperation while exploiting the multiuser diversity and BS densification. Last but not least, a joint user association and power control scheme that considers the different content requirements of users is proposed for energy cooperation enabled caching HetNets. It shows that the proposed scheme significantly enhances the energy efficiency performance of caching HetNets

Stochastic Optimization of Energy Harvesting Wireless Communication Networks

Energy harvesting from environmental energy sources (e.g., sunlight) or from man-made sources (e.g., RF energy) has been a game-changing paradigm, which enabled the possibility of making the devices in the Internet of Things or wireless sensor networks operate autonomously and with high performance for years or even decades without human intervention. However, an energy harvesting system must be correctly designed to achieve such a goal and therefore the energy management problem has arisen and become a critical aspect to consider in modern wireless networks. In particular, in addition to the hardware (e.g., in terms of circuitry design) and application point of views (e.g., sensor deployment), also the communication protocol perspective must be explicitly taken into account; indeed, the use of the wireless communication interface may play a dominant role in the energy consumption of the devices, and thus must be correctly designed and optimized. This analysis represents the focus of this thesis. Energy harvesting for wireless system has been a very active research topic in the past decade. However, there are still many aspects that have been neglected or not completely analyzed in the literature so far. Our goal is to address and solve some of these new problems using a common stochastic optimization setup based on dynamic programming. In particular, we formulate both the centralized and decentralized optimization problems in an energy harvesting network with multiple devices, and discuss the interrelations between these two schemes; we study the combination of environmental energy harvesting and wireless energy transfer to improve the transmission rate of the network and achieve a balanced situation; we investigate the long-term optimization problem in wireless powered communication networks, in which the receiver supplies wireless energy to the terminal nodes; we deal with the energy storage inefficiencies of the energy harvesting devices, and show that traditional policies may be strongly suboptimal in this context; finally, we investigate how it is possible to increase secrecy in a wireless link where a third malicious party eavesdrops the information transmitted by an energy harvesting node