دانلود رایگان مقاله انتقال انرژی بی سیم در شبکه حسگر با شارژر موبایل متعدد

Abstract

Wireless energy transfer is used to fundamentally address energy management problems in Wireless Rechargeable Sensor Networks (WRSNs). In such networks mobile entities traverse the network and wirelessly replenish the energy of sensor nodes. In recent research on collaborative wireless charging, the mobile entities are also allowed to charge each other. In this work, we enhance the collaborative feature by forming a hierarchical charging structure. We distinguish the Chargers in two groups, the hierarchically lower Mobile Chargers which charge sensor nodes and the hierarchically higher Special Chargers which charge Mobile Chargers. We define the Coordination Decision Problem and prove that it is NP-complete. Also, we propose a new protocol for 1-D networks which we compare with a state of the art protocol. Motivated by the improvement in 1-D networks, we propose and implement four new collaborative charging protocols for 2-D networks, in order to achieve efficient charging and improve important network properties. Our protocols are either centralized or distributed, and assume different levels of network knowledge. Extensive simulation findings demonstrate significant performance gains, with respect to non-collaborative state of the art charging methods. In particular, our protocols improve several network properties and metrics, such as the network lifetime, routing robustness, coverage and connectivity. A useful feature of our methods is that they can be suitably added on top of non-collaborative protocols to further enhance their performance.

7. Conclusion and future work

In this work we study the problem of efficient collabo- rative wireless charging in Wireless Sensor Networks. We propose a new design approach, according to which, the set of chargers is partitioned into two groups, one hier- archically higher, called Special Chargers and one hierar- chically lower, called Mobile Chargers. The Mobile Charg- ers are responsible for charging the sensor nodes whereas the Special Chargers charge Mobile Chargers. This hierar- chical structure provides a more controllable and balanced energy replenishment of the network. We investigate what are good trajectories that Special Chargers should follow to charge Mobile Chargers, how much energy they should give and what are good coordination procedures to per- form. Moreover we provide a useful hierarchical add-on that can be added on top of non-collaborative protocols in order to enhance their performance. For future research, we plan to address non-uniform cases of the network deployment, since in many scenar- ios the network deployments are limited by the underlying terrain. We also plan to investigate which is the optimal number of Chargers and what is the best partition of them into Special Chargers and Mobile Chargers. Another future research direction is the case where a Charger can deliver energy simultaneously to more than one devices with high efficiency using the technology developed e.g. in [20].