Cooperative Wireless Power Transfer for Lifetime Maximization in Wireless Multihop Networks
Abstract : To extend the lifetime of wireless multihop networks suffering from energy scarcity of constituent nodes, we apply a wireless power transfer (WPT) technology to multihop transmission and allow the nodes with substantial energy to perform WPT to energy-deprived nodes in a cooperative way. We construct a system model for this cooperative WPT (CoWPT)-based multihop transmission and formulate an optimization problem to determine the optimal WPT time of each node for maximizing the lifetime of the multihop network. We first verify that the lifetimes of multihop nodes have the solidarity property, and that the network lifetime is maximized by equalizing their respective lifetimes. Then we convert the considered optimization problem into a tractable linear programming (LP) problem and solve it. Intensive simulations show that the optimal CoWPT solution significantly increases the network lifetime compared with the typical WPT method in both wireless sensor network (WSN) and mobile ad hoc network (MANET) environments. Moreover, it is revealed that the network lifetime is further improved in MANET relative to in WSN because more ambient RF signals are available for energy harvesting in the MANET topology.
? The work in considered provisioning additional energy on existing nodes and deploying relays to extend the network lifetime.
? The research works in have proved significant potential of using cooperative diversity in wireless networks. However, most of the existing works focus on improving physical layer performance or minimizing energy consumption.
? We assume that each signal transmission is constrained to halfduplex mode, the system is uncoded, and the source and the relay transmit signals through orthogonal channels by using existing TDMA, FDMA, or CDMA schemes.
? The basic idea of cooperative diversity is to allow distributed users in the network help relay information of each other so as to explore inherent spatial diversity which is available in the relay channels.
? A similar study was performed in , formulating the network lifetime maximization problem as a joint power, rate and scheduling problem subjected to rate distortion constraints, capacity constraints of the links, energy constraint of the sensor batteries and delay constraint of the encoded data arriving at the sink node.
? These three components were formulated as a linear programming problem for maximizing the NL.
? A beneficial method of circumventing this problem is to rely on a technique referred to as controlled mobility, which relies on mobile sensors or mobile sinks, where each mobile sensor cooperatively decides its direction of movement in order to prevent an uneven traffic burden distribution.
• The performance of the proposed strategies that utilize only local CSI and REI is shown to be comparable to that of the optimal strategy that demands global CSI and REI.
• Many cooperation strategies have been proposed with different relaying techniques , such as amplify-and-forward (AF) and decode-and-forward.
• Several power allocation strategies have been proposed to minimize the average transmission power for different cooperation schemes, system objectives and network topologies.
• The MRE and MEI strategies studied in this work was proposed and analyzed in for data gathering applications in sensor networks.
? Moreover, the NL is a crucial metric in terms of providing the system designer with well-informed decisions for the sake of maintaining the desired network performance and the QoS in WSNs, where the sensor nodes usually rely on a limited battery capacity, unless they have direct mains supply.
? Another cross-layer optimization technique was employed in for illustrating the trade-off between NL maximization and application performance.
? Network coding has been shown to be able to enhance the energy-efficiency of wireless networks, hence improving their NL, as discussed in .
? However, considering the relatively low efficiency of energy harvesters, the NL maximization and power allocation mechanisms still play a significant role in keeping the network functional for an extended duration.
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