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On the Multihop Performance of Synchronization Mechanisms in High Propagation Delay Networks

IEEE TRANSACTIONS ON COMPUTERS 2009年第5期58卷 577-590页

作者： Huang, Pai-Han Desai, Maulik Qiu, Xiaofan Krishnamachari, Bhaskar Univ So Calif Dept Elect Engn Syst Viterbi Sch Engn Los Angeles CA 90089 USA Columbia Univ Dept Elect Engn New York NY 10562 USA Texas Instruments Inc Dallas TX 75206 USA

We analyze the single and multihop performance of time synchronization mechanisms for challenging environments characterized by high propagation delays, low duty-cycle operation, and imprecise clocks, such as underwater acoustic sensor networks. We find that receiver-receiver-based schemes are unsuitable for such environments, and therefore focus primarily on sender-receiver schemes. According to our analysis, a one-way dissemination approach provides good clock skew estimation but poor offset estimation while a two-way exchange approach provides accurate offset estimation but imprecise clock skew estimation. In average, using one-way scheme can result in significant cumulative propagation error over multiple hops, and using two-way can lead to high variance of propagation error. We develop and analyze a hybrid one-way dissemination/two-way exchange technique, and verify the performance of our hybrid scheme through trace-based experiments. The results suggest that this hybrid approach can provide bounded average error propagation in multihop settings and significantly lower variance of propagation error.

关键词： Wireless communications formal models data communications protocol verification sensor networks algorithm/protocol design and analysis

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SELECT: Self-learning collision avoidance for wireless networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2008年第3期7卷 305-321页

作者： Chen, Chun-Cheng Seo, Eunsoo Kim, Hwangnam Luo, Haiyun Univ Illinois Dept Comp Sci Urbana IL 61801 USA Korea Univ Sch Elect Engn Seoul 136713 South Korea

The limited number of orthogonal channels and autonomous installations of hot spots and home wireless networks often leave neighboring 802.11 basic service sets (BSSs) operating on the same or overlapping channels, therefore interfering with each other. However, the 802.11 medium access control (MAC) does not work well in resolving inter-BSS interference due to the well-known hidden/exposed-receiver problem, which has been haunting the research community for more than a decade. In this paper, we propose SELECT, an effective and efficient self-learning collision avoidance strategy to address the hidden/exposed-receiver problem in 802.11 wireless networks. SELECT is based on the observation that carrier sense with received signal strength (RSS) measurements at the sender and the receiver can be strongly correlated. A SELECT-enabled sender exploits such correlation using an automated online learning algorithm and makes an informed judgment of the channel availability at the intended receiver. SELECT achieves collision avoidance at packet-level time granularity, involves zero communication overhead, and easily integrates with the 802.11 Distributed Coordination Function (DCF). Our evaluation in analysis, simulations, and prototype experiments show that SELECT addresses the hidden/exposed-receiver problem well. In typical hidden/exposed-receiver scenarios, SELECT improves the throughput by up to 140 percent and the channel access success ratio by up to 302 percent while almost completely eliminating contention-induced data packet drops.

关键词： wireless communication access schemes algorithm/protocol design and analysis

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A mobile-directory approach to service discovery in wireless ad hoc networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2008年第10期7卷 1242-1256页

作者： Gonzalez-Valenzuela, Sergio Vuong, Son T. Leung, Victor C. M. Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada Chinese Univ Hong Kong Dept Elect Hong Kong Hong Kong Peoples R China Jilin Univ Changchun Peoples R China

We present the Service Directory Placement algorithm (SDPA), a directory-placement scheme that leverages the performance of existing service discovery protocols over wireless ad hoc networks. SDPA promotes the deployment of a nomadic service directory, whose current location in the network varies according to the dynamics of service-discovery queries driven by the users' applications and partial knowledge of the network's topology. SDPA is based on a heuristic approach, whose performance is optimized by formulating the directory-placement problem as a Semi-Markov Decision Process (SMDP) solved by the means of a reinforcement-learning technique known as Q-Learning. Performance evaluations obtained through computer simulations of networks with up to 45 hosts moving at pedestrian speeds reveal average bandwidth savings close to 50 percent over a default broadcast/multicast approach for service discovery once an efficient directory-placement policy is obtained.

关键词： service data communications algorithm/protocol design and analysis ubiquitous computing machine learning

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Distributed algorithm for efficient construction and maintenance of connected k-hop dominating sets in mobile ad hoc networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2008年第4期7卷 444-457页

作者： Yang, Hong-Yen Lin, Chia-Hung Tsai, Ming-Jer Natl Tsing Hua Univ Dept Comp Sci Hsinchu 300 Taiwan

A k-hop dominating set is a subset of nodes such that each node that is not in the set can be reached within k hops from at least one node in the set. A connected k-hop dominating set can be used for disseminating topology update packets or route request packets, in which the flooding search space is reduced to the set, resulting in significant flooding overhead reduction in broadcast-related applications. In mobile ad hoc networks, a connected k-hop dominating set may become disconnected due to node mobility or switch-off, which necessitates the reformation of the k-hop dominating set. In this paper, we identify a sufficient condition that guarantees the connectivity of the virtual backbone. The condition can be verified in a distributed manner by the node only having the link information of its neighbors. (Unless specified otherwise, the term "neighbor" denotes a "1-hop neighbor." The link information of neighbors can be obtained by 2-hop neighbor information or 1-hop neighbor positions [ 4], [ 16].) With the help of this condition, we propose a distributed algorithm for efficiently constructing and maintaining connected k-hop dominating sets in mobile ad hoc networks. Simulations show that our connected k-hop dominating set is small and stable and needs little maintenance overhead in the Random-Walk Mobility and Gauss-Markov Mobility Models.

关键词： algorithm/protocol design and analysis mobile ad hoc network network topology localized communication routing protocols

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Benefit-based data caching in ad hoc networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2008年第3期7卷 289-304页

作者： Tang, Bin Gupta, Himanshu Das, Samir R. Wichita State Univ Dept Comp Sci Wichita KS 67260 USA SUNY Stony Brook Dept Comp Sci Stony Brook NY 11794 USA

Data caching can significantly improve the efficiency of information access in a wireless ad hoc network by reducing the access latency and bandwidth usage. However, designing efficient distributed caching algorithms is nontrivial when network nodes have limited memory. In this article, we consider the cache placement problem of minimizing total data access cost in ad hoc networks with multiple data items and nodes with limited memory capacity. The above optimization problem is known to be NP-hard. Defining benefit as the reduction in total access cost, we present a polynomial-time centralized approximation algorithm that provably delivers a solution whose benefit is at least 1/4 (1/2 for uniform-size data items) of the optimal benefit. The approximation algorithm is amenable to localized distributed implementation, which is shown via simulations to perform close to the approximation algorithm. Our distributed algorithm naturally extends to networks with mobile nodes. We simulate our distributed algorithm using a network simulator (ns2) and demonstrate that it significantly outperforms another existing caching technique (by Yin and Cao [ 33]) in all important performance metrics. The performance differential is particularly large in more challenging scenarios such as higher access frequency and smaller memory.

关键词： caching placement policy ad hoc networks algorithm/protocol design and analysis simulations

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Security and QoS self-optimization in mobile ad hoc networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2008年第9期7卷 1138-1151页

作者： Shen, ZhengMing Thomas, Johnson P. Oklahoma State Univ Dept Comp Sci Tulsa OK 74106 USA Univ Reading Reading RG6 2AH Berks England Pace Univ New York NY USA

Network quality of service (QoS) and network security have been considered as separate entities and research in these areas have largely proceeded independently. However, security impacts overall QoS and it is therefore essential to consider both security and QoS together when designing protocols for ad hoc environments as one impacts the other. In this paper, we propose a mechanism for a distributed dynamic management system which aims to maximize QoS and/or security while maintaining a minimum user acceptable level of QoS and/or security even as network resource availability changes. In order to achieve this objective, we propose three basic frameworks: a policy-based plug-in security framework, multilayer QoS guided routing, and a proportional, integral, derivative (PID) controller. Simulation results indicate the proposed PID optimized security and the QoS algorithm produces similar performance to nonsecure QoS routing protocols under various traffic loads.

关键词： mobile computing algorithm/protocol design and analysis network-level security and protection

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Bandwidth-constrained routing problem in wireless ad hoc networks

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2008年第1期19卷 4-14页

作者： Chiu, Chun-Yuan Kuo, Yu-Liang Wu, Eric Hsiao-Kuang Chen, Gen-Huey Natl Taiwan Univ Dept Comp Sci & Informat Engn Taipei 10764 Taiwan Natl Cent Univ Dept Comp Sci & Informat Engn Chungli 320 Taiwan

The bandwidth-constrained routing problem (BCRP) asks for a route that has sufficient bandwidth for data transmission. When BCRP is defined for wired networks, it can be solved in polynomial time. On the other hand, when it is defined for wireless ad hoc networks, it is NP-complete if the underlying MAC protocol is TDMA-based or CDMA-over-TDMA-based. In this paper, we show that BCRP is still NP-complete, even if CSMA-based or contention-based CDMA MAC protocols are used. Besides, we show that BCRP is polynomial-time solvable if the channel model is collision-free and the scheduling policy is FIFO. In wireless ad hoc networks, no MAC protocol was designed before, which would lead to a polynomial-time solution to BCRP. The results of this paper suggest a design principle for MAC protocols that can support QoS routing well.

关键词： algorithm/protocol design and analysis mobile communication systems reducibility and completeness routing protocols

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Overlay networks with linear capacity constraints

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2008年第2期19卷 159-173页

作者： Zhu, Ying Li, Baochun UOIT Fac Business & Informat Technol Oshawa ON L1H 7K4 Canada UOIT Fac Engn & Appl Sci Oshawa ON L1H 7K4 Canada Univ Toronto Dept Elect & Comp Engn Toronto ON M5S 3G4 Canada

Overlay networks are virtual networks residing over the IP network;consequently, overlay links may share hidden lower level bottlenecks. Previous work has assumed an independent overlay model: a graph with independent link capacities. We introduce a model of overlays that incorporates correlated link capacities and linear capacity constraints (LCC) to formulate hidden shared bottlenecks;we refer to these as LCC-overlays. We define metrics to qualitatively measure overlay quality in terms of its accuracy ( in representing the true network topology) and efficiency ( that is, performance). Through analysis and simulations, we show that LCC-overlay is perfectly accurate and, hence, enjoys much higher efficiency than the inaccurate independent overlay. We discover that even a highly restricted LCC class-node- based LCC-yields near-optimal accuracy and significantly higher efficiency. We study two network flow problems in the context of LCC-graphs: widest path and maximum flow. We prove that Widest Path with LCC is NP-complete. We formulate Maximum Flow with LCC as a linear program and propose an efficient distributed algorithm to solve it. Based on the LCC model, we further study the problem of optimizing delay while still maintaining optimal or near-optimal bandwidth. We also outline a distributed algorithm to efficiently construct an overlay with node-based LCC.

关键词： overlay networks network protocols algorithm/protocol design and analysis network topology

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Comments on "Optimal Resource Allocation in Overlay Multicast"

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2008年第4期19卷 572-573页

作者： Yan, Jinyao May, Martin Plattner, Bernhard ETH Swiss Fed Inst Technol Comp Engn & Networks Lab CH-8092 Zurich Switzerland Commun Univ China Comp & Network Ctr Beijing 100024 Peoples R China

In this comments paper, we revisit the network model introduced in [1]. We discuss the inaccuracy of the model and, to correct the network model, we propose to apply directed capacity constraints for directed flows. Based on a comparison of numerical results, we show that the corrected model leads to better accuracy than the original model.

关键词： multicast algorithm/protocol design and analysis nonlinear programming

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The RNA Metaprotocol

The RNA Metaprotocol

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17th International Conference on Computer Communications and Networks

作者： Touch, Joseph D. Pingali, Venkata K. USC Inst Informat Sci Marina Del Rey CA 90292 USA

ISBN: (纸本)9781424423897

The Recursive Network Architecture (RNA) explores the relationship of layering to protocol and network architecture. RNA examines the implications of using a single, tunable protocol, called a metaprotocol, for different layers of the protocol stack, reusing basic protocol operations across different protocol layers to avoid reimplementation. Its primary goal is to encourage cleaner cross-layer interaction, to support dynamic service composition, and to gain an understanding of how layering affects architecture. This paper provides a description of RNA and a recently completed initial prototype. The prototype extends the Click modular router with control capabilities including dynamic composition and discovery. These capabilities are used to demonstrate simple but flexible stacks of instances of a metaprotocol that are customizable at runtime.

关键词： algorithm/protocol design and analysis Internet Network Architecture and design protocols

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