Barrier coverage is an appropriate coverage model for intrusion detection by constructing sensor barriers in wireless sensor networks. In this paper, we focus on the problem how to relocate mobile sensors to construct k sensor barriers with minimum energy consumption. We first analyze this problem, give its Integer Linear Programming(ILP) model and prove it to be NP-hard. Then we devise an approximation algorithm AHGB to construct one sensor barrier energy-efficiently, simulations show that the solution of AHGB is close to the optimal solution. Based on AHGB, a Divide-and-Conquer algorithm is proposed to achieve k-barrier coverage for large sensor networks. Simulations demonstrate the effectiveness of the Divide-and-Conquer algorithm.
Barrier coverage is known to be an appropriate model of coverage for movement detection and boundary guard, which is achieved by barriers of sensors. This paper is focused on how to achieve strong k-barrier coverage with mobile sensors energy-efficiently. We first design an approximation algorithm CBGB to achieve strong 1-barrier coverage energyefficiently, and the performance of CBGB is close to the optimal solution. Then, we propose a Divide-and-Conquer algorithm to achieve strong k-barrier coverage for large sensor networks. Simulations demonstrate the effectiveness of the proposed algorithm for achieving k-barrier coverage.
Due to the 60Hz or higher LCD refresh operations, display controller (DC) reads the pixels out from frame buffer at fixed rate. Accessing frame buffer consumes not only memory bandwidth, but power as well. Thus frame buffer compression (FBC) can contribute to alleviating both bandwidth and power consumption. A conceptual frame buffer compression model is proposed, and to the best of our knowledge, an arithmetic expression concerning the compression ratio and the read/update ratio of frame buffer is firstly presented, which reveals the correlation between frame buffer compression and target applications. Moreover, considering the linear access feature of frame buffer, we investigate a frame buffer compression without color information loss, named LFBC (Lossless Frame-Buffer Compression). LFBC defines new frame buffer compression data format, and employs run-length encoding (RLE) to implement the compression. For the applications suitable for frame buffer compression, LFBC reduces 50%-90% bandwidth consumption and memory accesses caused by LCD refresh operations.
To achieve scalability, a few resource-rich heterogeneous nodes are scattered in a wireless sensor network consisting of a large number of energy-constrained sensor nodes. Heterogeneous nodes are equipped with powerful radio transceiver and their main task is to organize a backbone communication network and to relay data to the sink. For the scenario, this paper proposes a coverage problem which maintaining relay connectivity at the same time in heterogeneous wireless sensor networks. The goal is to find a minimum relay connected set cover (MRCSC) which satisfies (1) active nodes in set cover fully sense the whole task area. Motivated by triangular lattice with asymptotic optimality, we address a rule for restricting irregularity spread to form an approximate nice triangular lattice, (2) active nodes are relay connected which means any active node connects to at least one heterogeneous node with a given success data forwarding rate. Simulations show that the coverage of MRCSC nearly reaches that of OGCD, but relay connectivity of active nodes is strongly reinforced with limited count of additional nodes.
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