Hybrid Time-Power Switching Protocol of Energy Harvesting Bidirectional Relaying Network: Throughput and Ergodic Capacity Analysis

In this paper, we investigate system performance in term of throughput and ergodic capacity of the hybrid time-power switching protocol of energy harvesting bidirectional relaying network. In the first stage, the analytical expression of the system throughput and ergodic capacity of the model system is proposed and derived. In this analysis, both delay-limited and delay-tolerant transmission modes are presented and considered. After that, the effect of various system parameters on the proposed system is investigated and demonstrated by Monte-Carlo simulation. Finally, the results show that the analytical mathematical and simulated results match for all possible parameter values for both schemes

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

Annual Report, 2013-2014

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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

Energy Cooperation in Energy Harvesting Two-Way Communications

Abstract—In this paper, we investigate a two-way communication channel where users can harvest energy from nature and energy can be transferred in one-way from one of the users to the other. Energy required for data transmission is randomly harvested by the users throughout the communication duration and users have unlimited batteries to store energy for future use. In addition, there is a separate wireless energy transfer unit that facilitates energy transfer only in one-way and with efficiency α. We study the energy cooperation made possible by wireless energy transfer in the two-way channel. Assuming that both users know the energy arrivals in advance, we find jointly optimal offline energy management policies that maximize the sum throughput of the users. We show that this problem is a convex optimization problem, and find the solution by a generalized two-dimensional directional water-filling algorithm which transfers energy from one user to another while maintaining that the energy is allocated in the time dimension optimally. Optimal solution equalizes the energy levels as much as possible both among users and among slots, permitted by causality constraints of the energy arrivals and one-way energy transfer. I