Firmware Over-the-Air (FOTA) update technology is required to keep the software of the massively deployed Wireless Sensor Network (WSN) devices up to date. However, when there are many nodes in a WSN and the cellular network connects the server and the WSN, the traditional method of transferring data directly from the server to the end node can be costly. We propose a Two-Phase FOTA Dissemination Scheme to address the communication cost problem by reducing traffic between WSN and external networks. This demonstration shows that the two-phase update reduces traffic between the external network and the WSN.

More and more applications are being discovered for scalable video coding (SVC) in network-adaptive video streaming and storage systems. In the SVC encoder, an exhaustive search technique is employed to select the best coding mode for each macro block. This technique achieves the highest possible coding efficiency, but it results in extremely large encoding time. In this paper, we propose an adaptive fast mode decision algorithm for inter layer coding for spatial scalability and coarse grain quality scalability (CGS). In the proposed method, we select candidate modes adaptively for estimation in enhancement layer using the information of base layer and rate distortion (RD) cost of base layer skip mode. RD cost of base layer skip mode gives the correlation information of enhancement layer with base layer and base layer mode is used to reduce the number of candidate modes. We verify that the overall encoding time can be reduced up to 63 % through the analysis of experimental results.

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Along with energy conservation, it has been a critical issue to maintain a desired degree of coverage in wireless sensor networks (WSNs), especially in a mobile environment. By enhancing a variant of random waypoint (RWP) model, we propose mobility resilient coverage control (MRCC) to assure if-coverage in the presence of mobility. Our basic goals are (1) to elaborate the probability of breaking if-coverage with moving-in and moving-out probabilities, and (2) to issue wake-up calls to sleeping sensors to meet user requirement of if-coverage even in the presence of mobility. Furthermore, by separating the mobility behavior into average and individual, the probability of breaking if-coverage can be precisely calculated, hence reducing the number of sensors to be awakened. Our experiments with NS2 show that MRCC with the individual probability achieves better coverage by 1.4% with 22% fewer numbers of active sensors than that of existing coverage configuration protocol (CCP).

In recent years, time synchronization in wireless sensor networks (WSN) is important for accurate time stamping of events and fine-tuned coordination of duty cycles to minimize power consumption. This paper presents an on-demand hierarchical mesh-based time synchronization (OHMTS) that is flexible, multi-hop based and high-precise in WSN. OHMTS adopts hierarchical and multi-hop mesh-based network architecture with supporting energy-saving problem for WSN. For the purpose of performance evaluation, we first study the error sources of OHMTS and then we evaluate the performance of OHMTS with respect to synchronization delay error using network simulator (NS-2). The simulation results show that OHMTS provides fine-tuned clock offset mechanism and can be easily applied to real WSN platform

Time synchronization for embedded sensor networks (ESN) is important for accurate time stamping of events and fine-tuned coordination of duty cycles to minimize power consumption. This paper presents a novel chained-ripple time synchronization (CRIT) protocol that is fast, flexible, and high-precise in ESN. CRIT adopts hierarchical and multi-hop time synchronization architecture with supporting energy-saving problem in ESN. The algorithm works in two phases. In the first phase, a horizontal structure between missionary nodes (MN) is established in the network by piggy-back neighbor time synchronization (PBNT) algorithm. In the second phase, a vertical structure between a MN and sensor nodes (SN) is set up in each sensor group (SG) by distributed depth first search (DDFS) algorithm. By applying these two phases repeatedly, all nodes in ESN efficiently synchronize to each other. For the purpose of performance evaluation, we first study the error sources of CRIT. In addition, we simulate CRIT in terms of synchronization errors of two phases and clock offset using network simulator (NS-2). The simulation results show that CRIT provides very accurate time synchronization and it can be easily expanded to real ESN

Software reengineering for object-oriented rearchitecturing offers an exciting opportunity in migrating old legacy systems to evolvable systems in a disciplined manner. In the twofold-strategy software reengineering for object-oriented rearchitecturing, one of the problems to be solved is to derive a proper object-oriented model from the output of reverse engineering and the output of forward engineering. In general, the outputs of forward and reverse engineering can be inconsistent in their abstract levels, the amount of design information, naming conventions, and structures. In this paper we present an Object-oriented model Refinement Technique (ORT) to build a final object model in the twofold-strategy software reengineering. We first organize the information gained from reverse engineering into specification information tree, and then compare the entities in the specification information tree with the information from forward engineering using tree-structured data dictionary to produce the final model. We demonstrate the usability of ORT by an example.