Browsing by Author "Su, Chao-Min"

Now showing 1 - 4 of 4

G-Constellations: G-Sensor Motion Tracking Systems
(2010)
Yi, Chih-Wei
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Su, Chao-Min
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Chai, Wen-Tien
;
Huang, Jiun-Long
;
Chiang, Tsun-Chieh
In most inertial motion tracking systems, motion directions are detected and measured by direction sensors such as magnetometers and gyroscopes. In this paper, we propose a motion tracking system, called g-sensor constellations, in which only g-sensors but no direction sensors are used. The g-sensor constellation is a loose coupling g-sensor system with rigid geometric topology. As few as three g-sensors are needed for motion tracking, including direction detection. The system is easy to be installed. No complicated calibrations are needed and the necessary information is the distances between sensors. The proposed framework can improve the accuracy of dead reckoning systems and help in the analyzing of traffic accidents and developing new human-computer interfaces. In our experiments, a g-sensor constellation composed of three g-sensors, which are located at the vertices of an equilateral triangle with edges of 0.3m and communicate with the processing unit via Bluetooth links, is built to verify the proposed technique.
Sharp Thresholds for Relative Neighborhood Graphs in Wireless Ad Hoc Networks
(2010-02-01)
Yi, Chih-Wei
;
Wan, Peng-Jun
;
Wang, Lixin
;
Su, Chao-Min
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資訊工程學系
In wireless ad hoc networks, relative neighborhood graphs (RNGs) are widely used for topology control. If every node has the same transmission radius, then an RNG can be locally constructed by using only one hop information if the transmission radius is set no less than the largest edge length of the RNG. The largest RNG edge length is called the critical transmission radius for the RNG. In this paper, we consider the RNG over a Poisson point process with mean density n in a unit-area disk. Let. beta(0) = root 1/(2/3 - root 3/2 pi) approximate to 1.6. We show that the largest RNG edge length is asymptotically almost surely at most beta root ln n/pi n for any fixed beta > beta(0) and at least beta root ln n/pi n for any fixed beta > beta(0). This implies that the threshold width of the critical transmission radius is o(root ln n/n). In addition, we also prove that for any constant xi, the expected number of RNG edges whose lengths are not less than beta(0)root ln n+xi/pi n is asymptotically equal to beta(2)(0)/2 e(-xi).
The Critical Grid Size and Transmission Radius for Local-Minimum-Free Grid Routing in Wireless Ad Hoc and Sensor Networks
(2010-12-01)
Yi, Chih-Wei
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Wan, Peng-Jun
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Su, Chao-Min
;
Huang, Chen-Wei
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資訊工程學系
In grid routing, the plane is tessellated into equal-sized square cells. Two cells are called neighbor cells if they share a common edge, and two nodes are called routing neighbors if they are in neighbor cells and within each other's transmission range. If communication parties are in the same cell, packets can be transmitted directly; otherwise, packets are forwarded to routing neighbors that are in cells closer to destination cells. As a greedy strategy, grid routing suffers the existence of local minima at which no neighbor nodes exist for relaying packets. To guarantee deliverability, in this paper, we investigate two vital parameters of grid routing, called the grid size and the transmission radius. Assume that nodes are represented by a Poisson point process with rate n over a unit-area square, and let l denote the grid size and r the transmission radius. First, we show that if l = root beta ln n/n for some constant beta and r = root 5l, then beta = 1 is the threshold for deliverability. In other words, there almost surely do not exist local minima if beta > 1 and there almost surely exist local minima if beta < 1. Next, for any given beta > 1, we give sufficient and necessary conditions to determine the critical transmission radius (CTR) for deliverability. Then, we show that as beta congruent to 1.092, the CTR r congruent to 2.09 root ln n/nis the minimum over all beta > 1. Simulation results are given to validate this theoretical work.
The Number of Isolated Nodes in a Wireless Network with a Generic Probabilistic Channel Model
(2013-02-01)
Su, Chao-Min
;
Yi, Chih-Wei
;
Wan, Peng-Jun
;
資訊工程學系
;
Department of Computer Science
A wireless node is called isolated if it has no links to other nodes. The number of isolated nodes in a wireless network is an important connectivity index. However, most previous works on analytically determining the number of isolated nodes were not based on practical channel models. In this work, we study this problem using a generic probabilistic channel model that can capture the behaviors of the most widely used channel models, including the disk graph model, the Bernoulli link model, the Gaussian white noise model, the Rayleigh fading model, and the Nakagami fading model. We derive the expected number of isolated nodes and further prove that their distribution asymptotically follows a Poisson distribution. We also conjecture that the nonexistence of isolated nodes asymptotically implies the connectivity of the network, and that the probability of connectivity follows the Gumbel function.