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This paper pursues RFID support for localization, aiming to pinpoint an object in 3D space. Given a set of RFID tags and/or readers deployed as reference points at known locations in a hexahedron (like shipping container or storage room), a passive and an active localization schemes are considered in this paper. Being the very first range-free 3D localization, our schemes depend solely on RFID tags and readers without other devices or sensors, and it avoids the need of distance estimation according to received wireless signal strength or phase difference. Our passive scheme locates an RFID tag attached to the target object, with both tags and readers as reference points. The active scheme locates an RFID reader, by iteratively determining a 3D sphere best covering the activated reference tags, referred to as the decision boundary optimization scheme (DeB). Results by simulations and testbed experiments using Alien RFID kits have been obtained, and they reveal that DeB outperforms its passive counterpart and achieves the localization error of 0.07 ft. Additionally, DeB yields better location accuracy and yet is much faster than a previous counterpart. With enhanced DeB (EDeB), accuracy of an object located near a hexahedron side or corner is improved considerably. [ABSTRACT FROM PUBLISHER]

This paper deals with decentralized, QoS-aware middleware for checkpointing arrangement in Mobile Grid (MoG) computing systems. Checkpointing is more crucial in MoG systems than in their conventional wired counterparts due to host mobility, dynamicity, less reliable wireless links, frequent disconnections, and variations in mobile systems. We've determined the globally optimal checkpoint arrangement to be NP-complete and so consider Reliability Driven (ReD) middleware, employing decentralized QoS-aware heuristics, to construct superior checkpointing arrangements efficiently. With ReD, an MH (mobile host) simply sends its checkpointed data to one selected neighboring MH, and also serves as a stable point of storage for checkpointed data received from a single approved neighboring MH. ReD works to maximize the probability of checkpointed data recovery during job execution, increasing the likelihood that a distributed application, executed on the MoG, completes without sustaining an unrecoverable failure. It allows collaborative services to be offered practically and autonomously by the MoG. Simulations and actual testbed implementation show ReD's favorable recovery probabilities with respect to Random Checkpointing Arrangement (RCA) middleware, a QoS-blind comparison protocol producing random arbitrary checkpointing arrangements. [ABSTRACT FROM AUTHOR]