9587091
Topology control for delay-constraint data collection in wireless sensor networks
Data collection is one of the most important operations in wireless sensor networks. Many practical applications require the real-time data transmission, such as monitoring, tracking, etc. In this paper, we import and define the topology control problem for delay-constraint data collection (TDDC), and then formalize this problem into an integer programming problem. As NP-Hardness of this problem, we present a load-aware power-increased topology control algorithm (namely LPTC) to heuristically solve the problem. The theoretical analysis shows that this algorithm can reach O(1)-approximation ratio for the linear networks. And we also analyze the impact of the delay-constraint on the worst-case for the planar networks. Moreover, this paper designs two localized algorithms, called as SDEL and DDEL, based on the area division for TDDC problem. The experimental results show that LPTC algorithm can save at least 17% power consumptions compared with HBH algorithm in many situations.
5825556
Coverage and Exposure Paths in Wireless Sensor Networks
Wireless sensor networks have posed a number of challenging problems such as localization, deployment and tracking, etc. One of the interesting problems is the calculation of the coverage and exposure paths for the sensor networks. This paper presents a fully localized algorithm to solve the worst coverage problem first introduced by Meguerdichian et al. The nodes of the sensor network cooperate to construct the worst coverage path only by the one-hop neighbor’s information, thus avoiding the massive communication and conserving the energy. The correctness of the proposed algorithm is proved formally under the sensing diminishing model. Moreover, this algorithm can be easily extended to solve the minimal exposure problem with local information as well.
12687767
Comments on "Estimation of frequencies and damping factors by two-dimensional ESPRIT type methods"
For original paper, see Rouquette and Najim (IEEE Trans. Signal Process., vol.49, no.1, p.237-45, 2001).The original authors present two high-resolution approaches to estimate two-dimensional (2-D) signal parameters. The first approach decomposes the 2-D estimation problem into two one-dimensional (1-D) ones, estimates the 1-D frequencies with the MEMP method, and then forms correct pairs using a new pairing scheme introduced in Vanpoucke et al. (1994). The second method (the 2-D ESPRIT method) directly estimates the 2-D frequencies. It is shown that both methods are more accurate than the related methods. The present authors note that the original paper appears to have a key error in the permutation matrix specification of the first method. In this comment, they derive the correct one with the performance simulations.
19569321
An Efficient Data Exchange Protocol Using Improved Star Trees in Wireless Sensor Networks
In wireless sensor networks, it is necessary and important to send information to all nodes. In some situation, every node has its own data to send to all the other nodes. The communication patterns are all-to-all broadcasting, which is called data exchange problem. In this paper, we present an efficient data exchange protocol using improved star trees. We divide the sensor area into four equal grids and each sensor node associates itself with a virtual grid based on its location information. These grids can be divided again if necessary. In each grid, we calculate the position of root node with location information of sensor nodes. Then, an efficient data exchange Star-Tree was constructed and used to achieve the exchange behavior in the grid. The fused data of each grid was sent to the center node. Simulations show that our protocol can prolong the lifetime about 69% to the multiple-chain protocols, and the delay can be reduced at least 35%.
11462203
Wireless fire monitoring system for ancient buildings
With the development of micro-processor and wireless communication, wireless sensor networks have becomes reality in some applications. In this paper, we mainly introduce the development of the fire monitoring system for ancient buildings based on wireless sensor networks. To satisfy the requirements of the application, lifetime and latency, etc, we design some key technologies in the different layers of the sensor nodes, such as data link layer, network layer and application layer. Finally, we realize the system based on MicaZ node and MTS300CB sensor broad, made by XBow Co.
18971548
Coverage-preserving Data Gathering in Wireless Sensor Networks
The power is the most significant resource in wireless sensor nodes, so energy conservation is the most important factor in designing the protocol for sensor networks. In this paper, we study the problem of energy-efficient collection of the physical information from the target area. The coverage-preserving data gathering (CPDG) problem is to build up a tree, which minimizes the total energy consumption, and preserves the original coverage to ensure the result correctness. This problem can be formalized as 0-1 integer linear programming, and solved by an efficient heuristic algorithm. Furthermore, an improved algorithm is also proposed to balance the energy consumption among all the sensor nodes. The experimental results show that CPDG algorithm can conserve the energy about 30% of PEDAP protocol, which is regarded as one of the most efficient data gathering protocols as we know.
21906808
The Theory and Application of Rough Integration in Rough Function Model
The definition of the rough integral Pawlak proposed is improved. New notions are proposed, which are respectively the rough integral on a constant interval and the roughly integral upper limit function, and so on. By comparing with the definite integral of real functions, the properties of rough integrals are analyzed. Giving the concept of mean value of discrete functions, the mean value method for rough integration is derived. At the same time, the intermediate value theorem of rough integration is proposed and its geometric significance is analyzed, which provides a dependable theoretical tool for rough integral operation, etc.. Conclusions including the existence theorem of rough primitives and the fundamental formula of rough calculus are proposed. By the representative of discrete functions, the method of computing a primitive is given, by which basic formulas for rough integration in common use are derived, and the method of rough direct integration is obtained. There is also the method of rough integration by parts for rough integrals which is like that of definite integrals. Thus the recurrence formula for rough integration is deduced, in which the integrand of the rough integral is in the shape of the product of a rough power function and a rough exponential function. It is pointed out that integration by substitution is not applicable for rough integral operation.
20747570
An Energy-efficient Disjoint Path Routing Approach for Wireless Ad-hoc Networks
Apparatus and method are provided for assessing the direction of fixation of an eye by detecting polarization-related changes in light retroreflected from the fundus of the eye. Nerve fibers in the retina of the eye are birefringent and alter the polarization state of light traversing them as a function of their orientation. The nerve fibers are arrayed in a characteristic pattern in the retina, specifically radiating outward from the fovea and converging to the optic nerve head. By assessment of polarization-related changes in rctroreflected light from multiple retinal areas either sequentially or simultaneously, characteristic birefringence signatures of portions of the retina can be identified which are used to assess the direction of fixation of the eye. In addition, interference from the corneal birefringence is reduced by using incident light having a polarization state that is substantially independent of meridional direction. Circularly polarized light or non-polarized light is used for the assessment. Interference from the corneal birefringence is reduced still further by detecting polarization-related changes that are substantially independent of the meridional direction of the corneal birefringence. This is accomplished by detecting changes in ellipticity by measuring solely the Stokes parameter S3 or by measuring any two Stokes parameters. An alternative is measuring the overall intensity of the retroreflected light when the dichroism of the lutein pigment particles in the vicinity of the fovea is used for the assessment.
6287453
A dynamic assignment problem in a mobile system with limited bandwidth
The assignment problem originally arising from parallel and distributed computing has been investigated intensively since the 70's when Harold Stone proposed a method to solve it with the aid of network flow algorithms. In this paper, we discuss this problem under a mobile environment with limited capacity of wireless links. The assignment problem is to schedule a group of related objects from a resource-constrained mobile device to its powerful proxy machine so that program activity migrates among processors as execution proceeds, and hence the overall performance will improve. First, we reduce this optimization problem to the 0/1 knapsack problem, and therefore show that it is NP-hard. Second, two heuristic algorithms are proposed. One is an adaptive heuristic algorithm with complexity O(NE), here, N and E represent the number of nodes and edges in the object graph abstracted from the mobile application. The other is a non-adaptive heuristic algorithm with complexity O(E), i.e, N times faster than the adaptive counterpart. Finally, we provide a simple distributed algorithm based on Raymond's tree-based distributed mutual exclusion algorithm for solving this problem with message complexity O(N/sup 2/ log N).
16750916
Mobile Robot Path Planning in Dynamic Environments
This paper introduces a genetic algorithm (GA) planner that is able to rapidly determine optimal or near-optimal solutions for mobile robot path planning problems in environments containing moving obstacles. The method restricts the search space to the vertices of the obstacles, obviating the need to search the entire environment as in earlier GA-based approaches. The new approach is able to produce an off-line plan through an environment containing dynamic obstacles, and can also re-calculate the plan on-line to deal with any motion changes encountered. A particularly novel aspect of the work is the incorporation of the selection of robot speed into the GA genes. The results from a number of realistic environments demonstrate that planning changes in robot speed significantly improves the efficiency of movement through the static and moving obstacles.
18897982
An Efficient SAN-Level Caching Method Based on Chunk-Aging
SAN-level caching can manage caching within a global view so that global hot data can be identified and cached. However, two problems may be encountered in the existing SAN-level caching methods: first, too many migrations from disks to cache resulting from cache thrashing; second, too few cache hits resulting from insufficient caching. This paper proposes a SAN-level caching method employing chunk-aging to control the migrations of chunks of data from disks to cache, which takes the temporal distribution of chunk accesses into account and solves the two problems above. Then by employing two LRU lists to manage the cache replacement, this method separates and manages two types of hot data chunks, one of which have burst accesses and the other have long-term frequent accesses, thus preventing them from interfering with each other in cache. The simulation results demonstrate that our method can achieve a high hit ratio while maintaining a relatively low migration rate.