Xin Zhang

Georgia Institute of Technology, Atlanta, GA, United States

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Publications (7)4.35 Total impact

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    ABSTRACT: The Intel Mote is a new sensor node platform with improved radio bandwidth and reliability due to the usage of Bluetooth radio. The connection-oriented nature of Bluetooth raises the issues of effective multi-hop network (scatternet) formation and maintenance that network and routing layer must address on top of the TinyOS abstractions. The hop distance and wireless link quality pose major challenges to multi-hop network performance, especially the connection-oriented networks such as Bluetooth scatternet. In this paper, we present a metric-based scatternet formation algorithm for the Intel Mote, which can optimize the Bluetooth network formation from the hop distance and link quality perspectives. In addition, a smart repair mechanism is proposed to deal with link/node failure and recover the network connectivity promptly with low overhead. The experiments with the Intel Mote platform demonstrate the effectiveness of the optimizations, which make the platform more powerful
    Mobile and Ubiquitous Systems - Workshops, 2006. 3rd Annual International Conference on; 08/2006
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    Xin Zhang, G.F. Riley
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    ABSTRACT: As a promising short-range wireless communication technology with the characteristics of interference resilience and power efficiency, Bluetooth is a ubiquitous candidate for wireless sensor network. The device discovery time of Bluetooth is the key for fast connection establishment, and hence successful scatternet formation and maintenance, which are required for wireless sensor networks. The frequency hopping technique used in Bluetooth and the asymmetric device discovery in Inquiry procedure result in undiscovered devices even within radio range. In this paper, we address the problem of device discovery in the context of scatternet formation. We evaluate the factors that affect device discovery process when multiple Bluetooth devices exist within radio range and wish to form a scatternet. Then we introduce a modified inquiry scheme using extended ID packet to accelerate the device discovery process. Simulation results show that our scheme leads to better performance for Bluetooth device discovery.
    Radio and Wireless Symposium, 2006 IEEE; 02/2006
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    Xin Zhang, George F. Riley
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    ABSTRACT: This article focuses on the performance and scalability study of very large-scale wireless ad hoc networks. As wireless devices become more and more popular, ad hoc networks grow in the number of nodes as well as the complexity of communication among the large number of nodes. However, due to the limitation of simulation technologies, it is either impossible or very hard to investigate the scalability of ad hoc routing protocols in very large-scale wireless networks. In this article, a comprehensive simulation study is conducted of the performance of an on-demand routing protocol on a very large scale, with as many as 50,000 nodes in the network. The authors address the scalability analysis based on various network sizes, node density, traffic load, and mobility. The reasons for packet loss are analyzed and categorized at each network layer. Based on the observations, the authors optimize the parameter selection and try to exhaust the scalability boundary of the on-demand routing protocol for wireless ad hoc networks.
    SIMULATION: Transactions of The Society for Modeling and Simulation International 01/2006; 82:131-142. · 0.69 Impact Factor
  • Xin Zhang, G.F. Riley
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    ABSTRACT: Bluetooth is a promising short-range wireless communication technology with the characteristics of interference resilience and power efficiency, both desirable for wireless sensor networks. The new Intel Mote sensor devices have Bluetooth technology incorporated as the standard wireless communications interface. When using Bluetooth in applications where multihop routing is required, groups of Bluetooth piconets combine together to form a scatternet. However, most of the existing scatternet formation protocols are designed to facilitate communications between any two pairs of devices, regardless of the actual traffic demand pattern. For wireless sensor network applications with low-duty-cycle traffic patterns, an on-demand scatternet formation protocol can achieve significant power saving by avoiding unnecessary network connectivity. To that end, we introduce an on-demand scatternet and route formation protocol designed specifically for Bluetooth-based wireless sensor networks. Our protocol builds a scatternet on demand, and is able to cope with multiple sources initiating traffic simultaneously. In addition, our energy-aware forwarding nodes selection scheme is based on local information only, and results in more uniform network resource utilization and improved network lifetime. Simulation results show that our protocol can provide scatternet formation with reasonable delay and good load balance, which results in prolonged network lifetime for Bluetooth-based wireless sensor networks.
    IEEE Communications Magazine 08/2005; · 3.66 Impact Factor
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    Xin Zhang, G.R. Riley
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    ABSTRACT: Bluetooth is a promising short-range wireless communication technology with the characteristics of interference resilience and power efficiency which are required by wireless sensor networks. As an enhanced sensor node platform, the Intel Mote uses Bluetoth as its radio scheme and MAC protocol. However, most of the existing scatternet formation protocols intend to connect all the nodes within the networks regardless of traffic pattern. For wireless sensor network applications with traffic of low duty cycle, on-demand scatternet formation and routing achieve significant power saving by avoiding to maintain the entire network connectivity. We propose in this paper an on-demand scatternet and route formation protocol for Bluetooth-based wireless sensor networks. It is able to cope with multiple sources initiating traffic simultaneously in densely deployed wireless sensor networks. We also introduce a modified inquiry scheme using extended ID packet for power efficient propagation of route request messages. Furthermore, we propose a mechanism employing POLL packets in Page processes to transfer scatternet formation and route reply information without extra overhead. Simulation results show that our on-demand scatternet formation and routing protocol can provide multihop channels with reasonable delay for Bluetooth-base wireless sensor networks.
    Software Engineering, Artificial Intelligence, Networking and Parallel/Distributed Computing, 2005 and First ACIS International Workshop on Self-Assembling Wireless Networks. SNPD/SAWN 2005. Sixth International Conference on; 06/2005
  • Xin Zhang, George F. Riley
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    ABSTRACT: ©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. Presented at the 13th IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems, 2005 As wireless devices become more and more popular, ad hoc networks grow in the number of nodes as well as the complexity of communication among the large number of nodes. However, due to the limitation of simulation technologies, it is either impossible or very hard to investigate the scalability of ad hoc routing protocols in very large– scale wireless networks. In this paper, a comprehensive simulation study is conducted of the performance of an on– demand routing protocol on a very large–scale, with as many as 50,000 nodes in the network. We address the scalability analysis based on various network sizes, traffic load, and mobility. The reasons for packet loss are analyzed and categorized at each layer. Based on the observations, we optimize the parameter selection and try to exhaust the scalability boundary of the on–demand routing protocol for wireless ad hoc networks.
    01/2005;
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    Xin Zhang, G.F. Riley
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    ABSTRACT: We introduce a simulation environment for wireless sensor networks using the Bluetooth wireless protocol in our Georgia Tech Network Simulator (GTNetS). Our goal is to explore the applicability of the Bluetooth protocol for wireless sensor networks. Our Bluetooth simulator implements detailed behavior of lower layers of the Bluetooth protocol stack, including baseband, LMP, L2CAP, and BNEP, with the emphasis on interference resilient and power efficient characteristics. The implementation is based on the design of GTNetS and will allow our Bluetooth simulator to be used for large-scale network simulations once an effective scatternet protocol implementation is completed. Further, our Bluetooth simulator is designed by using a strict layered model, which makes it easy to extend in order to accommodate modifications to the Bluetooth protocol or new MAC protocols for sensor networks. We present some simulation results with a simple network configuration to measure the performance of Bluetooth networks in terms of power consumption.
    Modeling, Analysis, and Simulation of Computer and Telecommunications Systems, 2004. (MASCOTS 2004). Proceedings. The IEEE Computer Society's 12th Annual International Symposium on; 11/2004