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In a Wireless Local Area Network (WLAN), devices have limited battery capacity. To improve the energy efficiency, we propose a new Medium Access Control (MAC) protocol to perform selective energy transfer request based on the amount of residual energy of a device in a WLAN with IEEE 802.11 Distributed Coordination Function (DCF). By supplying the energy only to the device requiring energy harvesting, the deterioration in network throughput during energy harvesting in a wireless network is minimized. We present a new energy Markov chain model to analyze the throughput and the energy efficiency of the proposed method. We confirm that the throughput and the energy efficiency of the proposed method is improved. [ABSTRACT FROM AUTHOR]

In this review work, energy harvesting methods for waste heat with small temperature differences between heat source and sink are discussed. At present, many methods are tried and employed to utilize this type of waste heat. A typical example is found in a conventional power generation system. By utilizing this type of waste heat, additional energy can be produced in regular power generation systems. Up to this point, two energy harvesting methods have been introduced and applied for the use with this type of waste heat. One is a method using an organic Rankine cycle (ORC) while the other is a method using a thermoelectric generation (TEG). An ORC is a Rankine cycle that can be applied to this type of waste heat using organic fluids such as refrigerants as working fluids instead of water used in a typical Ranking cycle. On the other hand, a TEG utilizes Peltier, Seebeck, and Thomson effects caused by the temperature difference between the heat source and sink for energy harvesting. In this work, various aspects associated with the use ORC and TEG for waste heat harvesting with small temperature differences between the heat source and sink. [ABSTRACT FROM AUTHOR]

The energy harvesting technology enables nodes to gather energy from a surrounding environment, and store excessive energy for later use. With the energy harvesting technology, the MAC protocol design paradigm shifts from “how to reduce energy consumption” to “how to optimize performance with harvested energy.” Legacy MAC protocols such as Framed Slotted Aloha (FSA) and Dynamic FSA (DFSA) does not consider energy harvesting and therefore may not work optimally in a network with energy harvesting nodes. In this paper, we propose a novel All You can Send (ALLYS) protocol for an energy harvesting network. ALLYS uses fixed frame size, but the slot transmission probability is adjusted by a sink node to control the channel access of contending nodes. A sink node broadcasts not only the frame size but also the transmission probability, so that a node can transmit more than once in an opportunistic manner fully utilizing the harvested energy. At the end of a frame, a sink node estimates the number of nodes accessing the channel and provides an appropriate transmission probability so as to reduce the collision probability preventing from the excessive contention among the nodes. We have evaluated the throughput, delay, and energy efficiency of the proposed ALLYS through analysis and simulations, and it is shown that ALLYS can greatly improve the throughput, delay, and energy efficiency in a wide range of operating conditions for wireless networks or Internet of Things (IoT). [ABSTRACT FROM PUBLISHER]

Power Beacons (PBs) can transfer energy wirelessly to devices in a wireless powered communication network. When PBs are deployed in an IEEE 802.11 Wireless LAN (WLAN), the energy transfer of PBs may interfere with the Wi-Fi stations if Wi-Fi stations and PBs share the same frequency band. In this letter, to resolve this interference problem, we propose a new Medium Access Control (MAC) protocol for IEEE 802.11 Wi-Fi stations to efficiently coexist with PBs. PBs contend just as Wi-Fi stations to gain opportunity for transferring energy and determine its operation based on the average energy level of stations. It is demonstrated that the throughput of the proposed MAC protocol is superior to that of IEEE 802.11 WLAN without interference control. [ABSTRACT FROM PUBLISHER]

We investigate self-energy recycling (S-ER)-based RF powered multi-antenna relay channels (RCs) for the coverage extension in sensor networks or small cells. In the S-ER-based RF powered RC, the power used at the relay station for data transmission depends only on the energy from the access point and the recycled energy from its own transmission. We propose an optimal beamforming scheme with associated protocols and study their behaviors for both cases of downlink only and joint up–down link. Strategies for the power allocation between data transmission and RF powering are provided and a comparison with the conventional RF powered RC is made. For the proposed power allocation strategies, the performance of the conventional RC is achieved by the proposed RF powered RC only when infinite RF power is available. A high value of S-ER helps the proposed systems to reach the performance of conventional relay systems. In the joint up–down link protocol, we show that the up–down rate region can simply be constructed with easy power allocation strategy. [ABSTRACT FROM PUBLISHER]

The near field communication (NFC) is a short-range wireless communication technology operating at 13.56 MHz. A pair of NFC devices may operate in the peer-to-peer (P2P) mode to exchange data securely. Since the frequency of both the existing radio frequency identification (RFID) systems and NFC devices is 13.56 MHz, a collision may occur in an environment where pairs of NFC devices coexist within the identification range of an RFID system. In this letter, we propose an anti-collision protocol in the coexistence environment where the NFC device in the P2P communication mode is interfered by an RFID system. In the proposed protocol, if the channel is already occupied or a collision is detected, an NFC initiator device switches its operating mode to the card emulation mode. Since the card emulation mode is compatible with the existing RFID standard, an RFID reader can recognize the presence of the NFC initiator device and allocates a slot for the P2P communications of the pairs of NFC devices. Performance analysis and simulation results show that the proposed protocol experiences less NFC delay than the legacy protocol. [ABSTRACT FROM PUBLISHER]

In a cognitive radio network with energy-harvesting secondary nodes, the energy states of nodes may be different depending on the time-varying amount of harvesting and consuming energy. The contention strategy needs to take the effect into consideration to save energy and increase the lifetime of secondary nodes. In this paper, an efficient sensing mechanism and a contention algorithm for a cognitive radio network with energy-harvesting nodes is presented. In order to prevent imminent outage of low energy nodes, higher priorities are given to low energy nodes during contention, which gives more transmission opportunities to low energy nodes before they go into the sleep mode. We propose to use differentiated access probabilities and contention windows for different energy levels. By utilizing the access probabilities of secondary nodes, the number of the contending nodes and the energy consumption decrease. The differentiated contention windows ensure the transmission priority of low energy nodes. The proposed MAC protocol is shown to enhance throughput and energy efficiency. The throughput and energy efficiency of the proposed MAC are investigated via analysis by a Markov chain and simulations. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks (VANETs) provide information and entertainment to drivers for safe and enjoyable driving. Wireless Access in Vehicular Environments (WAVE) is designed for VANETs to provide services efficiently. Since the control messages transmitted in WAVE are broadcast, the probability of collision increases by increasing the number of vehicle nodes. In this paper, we propose a coordinated multichannel medium access control (C-MAC) protocol for VANETs. The proposed C-MAC protocol provides contention-free broadcasting for safety messages by the coordination of roadside units (RSUs). An RSU schedules the broadcasting order of transmissions for safety messages. Contention-free broadcasting lowers the probability of collision and reduces the required time for transmissions of safety messages. An RSU may play the role of harvesting energy wirelessly to coordinated VANET terminals, which are gateways for Internet-of-things devices in the car. The contention interval for service channels is optimized to provide maximum throughput. The proposed C-MAC protocol is shown to enhance throughput and delay via analysis and simulation. [ABSTRACT FROM AUTHOR]

Forward error correction (FEC) enables the receiver to detect and correct error in a packet. The fountain code, which is a subclass of FEC, is a linear code to have high scalability and low complexities, and the Luby transform (LT) code is the first practical fountain code. In this letter, we propose a new broadcast method to increase the reliability of broadcast data transfer using the LT code. The proposed method enhances the reliability of the broadcast using the LT code by adjusting the number of output packets depending on a target probability. We develop a new analytic model to derive the data restoration probability with given configuration of encoding and decoding process. [ABSTRACT FROM PUBLISHER]

Summary: In a wireless powered communication network (WPCN), sensor nodes harvest energy to transmit information. By a harvest‐then‐transmit (HT) protocol, nodes can be classified into either energy receiving (ER) or data transmitting (DT) nodes depending on the current level of the harvested energy. Since nodes may join or leave a network any time and energy levels vary, the distribution of ER and DT nodes changes over time. As the number of contending DT nodes is highly dynamic, a quick learning mechanism is required for an access point (AP). We propose a learning AP that learns from experience and adapts the frame size according to the changes in the number of DT nodes. The proposed learning AP is also shown to learn well and react to the situation. We compare the performances of the proposed learning mechanism with a WPCN and conventional HT FSA schemes. The proposed RL scheme outperforms the comparative schemes in terms of success rate and delay. [ABSTRACT FROM AUTHOR]