Zimu Yuan

History-Aware Adaptive Backoff for Neighbor Discovery in Wireless Networks

The ability of discovering neighboring nodes, namely neighbor discovery, is essential for the self-organization of wireless ad hoc networks. In this paper, we propose a history-aware adaptive back off algorithm for neighbor discovery assuming collision detection and feedback mechanisms. Given successful discovery feedback, undiscovered nodes can adjust their contention window. With collision feedback and historical information, only transmission nodes enter the re-contention process, and decrease their contention window to accelerate neighbor discovery process after collision. Then, we give theoretical analysis of our algorithm on the discovery time and energy consumption, and derive the optimal size of contention windows by two rounds of optimization. Finally, we validate our theoretical analysis by simulations, and show the performance improvement over existing algorithms.

A cost-efficiency method on beacon nodes placement for wireless localization

Beacon node placement is the prerequisite for wireless localization, and the quality of placement scheme significantly affects localization accuracy. For a localization system, sufficient coverage and optimal beacon node distribution are required to provide satisfactory localization accuracy in a target area. Since the deployment cost grows with the number of beacon nodes, it is desirable to keep the number low. In this paper, we propose a cost-effective method for beacon node placement in arbitrarily shaped areas. The proposed method can guarantee satisfactory localization accuracy with a reasonable number of beacon nodes. It has polynomial time complexity and meets the beacon node distribution requirement. We theoretically analyze the lower and upper bounds of the number of beacon nodes, and use numerical analysis to verify its efficiency. Finally, we compare our approach to the existing placement methods in different scenarios. The comparison shows that our method can use fewer beacon nodes to obtain higher localization accuracy.

Performance Comparison of Positioning Algorithms for Complex GPS Systems

In this paper, we first present a classification for existing GPS positioning algorithms based on their features of mathematical operations in the calculating process and the accuracy of the solutions solved. Then we systematically evaluate and compare the performance of GPS algorithms for practical environments. Performance metrics include normalized execution time and the absolute error. We examine the performance of traditional Newton-Raphson algorithm as well as those newly proposed ones. We find that while the traditional Newton-Raphson algorithm does deliver a reasonable performance, others may over-perform it by a good margin.

An Improved TPSN Algorithm for Time Synchronization in Wireless Sensor Network

Time synchronization is important for many applications running in wireless sensor network. A classical algorithm, Timing-Sync Protocol for Sensor Networks (TPSN), has been widely adopted, which can achieve of the goal of high accuracy and energy-efficiency. However, the accuracy of TPSN algorithm will decrease in practical environments since communication conflicts occur in an ad-hoc wireless environment. We propose an improved algorithm that can resolve conflicts in the process of synchronization. Both theoretical analysis and simulations show that our method achieves better accuracy and uses less energy consumption when node density of network increases.

CIUV: Collaborating information against unreliable views

In many real world applications, the information of an object can be obtained from multiple sources. The sources may provide different point of views based on their own origin. As a consequence, conflicting pieces of information are inevitable, which gives rise to a crucial problem: how to find the truth from these conflicts. Many truth-finding methods have been proposed to resolve conflicts based on information trustworthy (i.e. more appearance means more trustworthy) as well as source reliability. However, the factor of mens involvement, i.e., information may be falsified by men with malicious intension, is more or less ignored in existing methods. Collaborating the possible relationship between informations origins and mens participation are still not studied in research. To deal with this challenge, we propose a method - Collaborating Information against Unreliable Views (CIUV) - in dealing with mens involvement for finding the truth. CIUV contains 3 stages for interactively mitigating the impact of unreliable views, and calculate the truth by weighting possible biases between sources. We theoretically analyze the error bound of CIUV, and conduct intensive experiments on real dataset for evaluation. The experimental results show that CIUV is feasible and has the smallest error compared with other methods.

SeaBase: An Implementation of Cloud Database

Cloud database usually refers to a database based on the cloud computing technology. However, as far as we know, pre-existing solutions of cloud database cannot integrate the data from multi-sourced heterogeneous databases, only supplying an isolated homogeneous database cluster. This paper presents a new implementation approach for cloud database: Sea Base, which integrates various data types into a unified one, based on the CCEVP(Cloud Computing-based Effective-Virtual-Physical) model. The results of our experiments show that Sea Base is feasible and practical.

A New Routing Scheme Based on Adaptive Selection of Geographic Directions

Geographic routing is recognized as an appealing approach to achieve efficient communications with low computational complexity and space cost. In order to apply this technology in Cyber-Physical Systems (CPSs), a comprehensive consideration must be given to performance issues such as throughput, delay, and load balance. In this paper, we provide a new routing scheme based on forwarding packets to multiple geographic directions. The proposed routing protocols are studied and analyzed theoretically. Theoretical bounds of throughput, delays and space cost are presented. Simulations show that our method performs more efficiently than traditional geographic routing schemes in terms of throughput, delay, and load balance with acceptable space cost. Our experiments also verify the tradeoff between performance metrics.

A two-tier positioning algorithm for wireless networks with diverse measurement types

A variety of measurement methods have been developed to obtain positions of nodes in wireless networks. However, most of existing positioning methods can only use limited types of measurement. These algorithms fail to exploit arbitrary measurement methods to improve the accuracy of positioning. In this paper, we propose a high-accuracy positioning algorithm which can utilize unlimited types of measurement. Our algorithm first selects a set of nodes equipped with more accurate measurement mechanisms to locate nodes whose positions are unknown. By this selection, a system of heterogenous equations is built. Then, our algorithm uses the classical genetic method to solve equations which commonly are hard to solve. The comprehensive simulation shows that our algorithm significantly improves the accuracy of positioning compared with existing methods.

A new routing scheme based on adaptive selection of geographic directions

Geographic routing is recognized as an appealing approach to achieve efficient communications with low computational complexity and space cost. In order to apply this technology in Cyber-Physical Systems (CPSs), a comprehensive consideration must be given to performance issues such as throughput, delay, and load balance. In this paper, we provide a new routing scheme based on forwarding packets to multiple geographic directions. The proposed routing protocols are studied and analyzed theoretically. Theoretical bounds of throughput, delays and space cost are presented. Simulations show that our method performs more efficiently than traditional geographic routing schemes in terms of throughput, delay, and load balance with acceptable space cost. Our experiments also verify the tradeoff between performance metrics.