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Bluetooth inquiry time characterization and selection

IEEE TRANSACTIONS ON MOBILE COMPUTING 2006年第9期5卷 1173-1187页

作者： Peterson, Brian S. Baldwin, Rusty O. Kharoufeh, Jeffrey P. USAF Inst Technol AFIT ENG Dept Elect & Comp Engn Wright Patterson AFB OH 45433 USA

The Bluetooth discovery process requires use of the inquiry substate which not only consumes significant power, but prevents normal data traffic flow and simultaneously acts as a potential noise source for neighboring networks. Therefore, the inquiry substate dwell time should be limited to discovering an acceptable number of neighboring devices. Although an estimate of the probability density function of the time to discover scanning devices is straightforward, the complex temporal and spectral interactions between two devices make precise inquiry time characterization difficult. We characterize these interactions and derive detailed analytical expressions for the probability distribution of the inquiry time for a Bluetooth-enabled device that follows v1.1 of the Bluetooth specification and uses the default 11.25 ms inquiry scan window that opens every 1.28 s. Subsequently, we show a single inquirer will locate 99 percent of all scanning devices within transmission range in 5.12 seconds rather than the 10.24 s recommended in the specification. Using specification v1.2, we show that the inquiry time can be reduced to 3.84 seconds and 1.28 seconds using the standard and interlaced inquiry scan modes, respectively. Substantial inquiry time reduction results in reduced power requirements and increased throughput by increasing data traffic and reducing interference with neighboring piconets. Our results are validated via comparison with existing simulation models and measurement studies. The models used to derive the distribution also lend themselves to characterizing the discovery time with variations in the discovery process.

关键词： mobile computing algorithm/protocol design and analysis mobile communication systems (Bluetooth inquiry probability distribution)

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Reliable packet transmissions in multipath routed wireless networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2006年第5期5卷 548-559页

作者： Djukic, P Valaee, S Univ Toronto Dept Elect & Comp Engn Toronto ON Canada

We study the problem of using path diversification to provide low probability of packet loss (PPL) in wireless networks. Path diversification uses erasure codes and multiple paths in the network to transmit packets. The source uses Forward Error Correction (FEC) to encode each packet into multiple fragments and transmits the fragments to the destination using multiple disjoint paths. The source uses a load balancing algorithm to determine how many fragments should be transmitted on each path. The destination can reconstruct the packet if it receives a number of fragments equal to or higher than the number of fragments in the original packet. We study the load balancing algorithm in two general cases. In the first case, we assume that no knowledge of the performance along the paths is available at the source. In such a case, the source decomposes traffic uniformly among the paths;we call this case blind load balancing. We show that for low PPL, blind load balancing outperforms single-path transmission. In the second case, we assume that a feedback mechanism periodically provides the source with information about the performance along each path. With that information, the source can optimally distribute the fragments. We show how to distribute the fragments for minimized PPL, and maximized efficiency given a bound on PPL. We evaluate the performance of the scheme through numerical simulations.

关键词： wireless communication fault tolerance network monitoring algorithm/protocol design and analysis linear programming

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Energy efficiency and error resilience in coordinated and non-coordinated medium access control protocols

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COMPUTER COMMUNICATIONS 2006年第17期29卷 3493-3506页

作者： Numanoglu, Tolga Tavli, Bulent Heinzelman, Wendi Univ Rochester Dept Elect & Comp Engn Rochester NY 14627 USA

Energy efficiency of a MAC protocol is one of the most important performance metrics, especially in mobile ad hoc networks, where the energy sources are limited. Two key factors in achieving energy efficiency for a MAC protocol are coordination among the nodes and schedule-based channel access. In order to achieve a sufficient level of coordination among the nodes, and hence to achieve energy efficiency, the exchange of control information via control packets is vital. As such, coordinated MAC protocols, which regulate channel access through scheduling, have been shown to achieve very high energy efficiencies when compared to non-coordinated MAC protocols, which do not employ scheduling. However, due to their increased vulnerability to channel errors, the performance of coordinated MAC protocols is affected more by the channel bit error rate (BER) than non-coordinated MAC protocols, which lack such control packets. In this paper, we investigate the energy efficiency and resilience against channel errors for coordinated and non-coordinated MAC protocols. Our results reveal that it is possible to achieve better system performance with coordinated MAC protocols even in lossy channels, provided that the BER level is not extremely high. (c) 2006 Elsevier B.V. All rights reserved.

关键词： energy-aware systems distributed networks wireless communication network protocols error resilience protocol verification algorithm/protocol design and analysis mobile communication systems access schemes

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An efficient and scalable loss-recovery scheme for video multicast

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IEEE TRANSACTIONS ON MULTIMEDIA 2005年第2期7卷 356-365页

作者： Peng, J Sikdar, B Rensselaer Polytech Inst Dept Elect Comp & Syst Engn Troy NY 12180 USA

With the increased popularity of multimedia services on the Internet, efficient video multicast strategies that can scale easily are of critical importance. This paper addresses the issue of video multicast loss recovery and presents an efficient and scalable scheme: Active Injection Recovery (AIR). The proposed scheme has three distinguishing features: active injection of repair packets into loss regions, on-demand construction of loss-recovery structures, and unique rate control over repair traffic. All of these features can save considerable network resources in a large-scale video multicast session. In addition, the proposed scheme simultaneously meets the three well-known requirements for efficiency and scalability in multicast loss recovery: request suppression, local recovery, and retransmission scoping. Another important feature of the proposed scheme is its low recovery latency, which is essential for video multicast. Our results show that the proposed scheme achieves significantly better overall performance as compared to existing multicast loss recovery schemes.

关键词： algorithm/protocol design and analysis error control loss recovery multicast

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Improving source routing reliability in mobile ad hoc networks

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2005年第4期16卷 362-373页

作者： Guo, S Yang, O Shu, Y Univ Ottawa Ottawa ON K1N 6N5 Canada Tianjin Univ Tianjin 300073 Peoples R China

In this paper, we propose a novel on-demand routing protocol called Backup Source Routing (BSR) to establish and maintain backup routes that can be utilized after the primary path breaks. The key advantage of BSR is the reduction of the frequency of route discovery flooding, which is recognized as a major overhead in on-demand protocols. We define a new routing metric, called the route reliability, and use it to provide the basis for the backup path selection. We use a heuristic cost function to develop an analytical model and an approximation method to measure this metric. Various algorithms for our BSR protocol in the route discovery phase and route maintenance phase have been designed based on this cost function. Extensive simulations demonstrated that our routing strategy has two interesting features: 1) In less stressful situations of lower mobility, BSR has similar performance to DSR. 2) In more challenging situations of high mobility, BSR can improve the performance significantly.

关键词： mobile communication system wireless communication routing protocol algorithm/protocol design and analysis multihop ad hoc network

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Maximizing network lifetime of broadcasting over wireless stationary ad hoc networks

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MOBILE NETWORKS & APPLICATIONS 2005年第6期10卷 879-896页

作者： Kang, I Poovendran, R Univ Washington Dept Elect Engn Seattle WA 98195 USA

We investigate the problem of extending the network lifetime of a single broadcast session over wireless stationary ad hoc networks where the hosts are not mobile. We define the network lifetime as the time from network initialization to the first node failure due to battery depletion. We provide through graph theoretic approaches a polynomial-time globally optimal solution, a variant of the minimum spanning tree (MST), to the problem of maximizing the static network lifetime. We make use of this solution to develop a periodic tree update strategy for effective load balancing and show that a significant gain in network lifetime over the optimal static network lifetime can be achieved. We provide extensive comparative simulation studies on parameters such as update interval and control overhead and investigate their impact on the network lifetime. The simulation results are also compared with an upper bound to the network lifetime.

关键词： broadcast energy efficient routing protocols ad hoc network network topology graphs and networks algorithm/protocol design and analysis

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Performance study of link layer and MAC layer protocols to support TCP in 3G CDMA systems

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2005年第5期4卷 489-501页

作者： Lin, HT Das, SK Univ Texas Dept Comp Sci & Engn Ctr Res Wireless Mobil & Networking Arlington TX 76019 USA

Providing support for TCP with good quality link connection is a key issue for future wireless networks in which Internet access is going to be one of the most important data services. A number of schemes have been proposed in literature to improve the TCP performance over wireless links. In this paper, we study the performance of a particular combination of link layer protocol (e.g., Radio Link protocol or RLP) and MAC retransmissions to support the TCP connections over third generation (3G) wireless CDMA networks. We specifically investigate two metrics - the packet error rate and the delay provided by RLP and MAC retransmissions - both of which are important for TCP performance. For independent and identically distributed (i.i.d) error channels, we propose an analytical model for RLP performance with MAC retransmission. The segmentation of TCP/IP packets into smaller RLP frames, as well as the RLP buffering process, are modeled using a Markov chain. For correlated fading channels, we introduce an analytical metric called RLP retransmission efficiency. We show that: 1) the RLP frame size has significant impact on the overall 3G system performance, 2) MAC layer retransmissions significantly improve the TCP performance, and 3) the RLP retransmission scheme (1,1,1,1,1,1) performs better in highly correlated channels, while scheme (1,2,3) performs better in low correlated channels. Simulation results also confirm these conclusions.

关键词： wireless communication network protocols protocol architecture algorithm/protocol design and analysis modeling techniques

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Improving protocol robustness in ad hoc networks through cooperative packet caching and shortest multipath routing

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2005年第5期4卷 443-457页

作者： Valera, AC Seah, WKG Rao, SV Inst Infocomm Res Commun & Devices Div Singapore 117674 Singapore

A mobile ad hoc network is an autonomous system of infrastructure-less, multihop, wireless mobile nodes. Reactive routing protocols perform well in this environment due to their ability to cope quickly against topological changes. This paper proposes a new routing protocol named CHAMP (CacHing And Multiple Path) routing protocol. CHAMP uses cooperative packet caching and shortest multipath routing to reduce packet loss due to frequent route failures. We show through extensive simulation results that these two techniques yield significant improvement in terms of packet delivery, end-to-end delay and routing overhead. We also show that existing protocol optimizations employed to reduce packet loss due to frequent route failures, namely local repair in AODV and packet salvaging in DSR, are not effective at high mobility rates and high network traffic.

关键词： routing protocols algorithm/protocol design and analysis

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The effects of channel errors on coordinated and non-coordinated medium access control protocols

The effects of channel errors on coordinated and non-coordin...

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IEEE International Conference on Wireless and Mobile Computing, Networking and Communications

作者： Numanoglu, T Tavli, B Heinzelman, W Univ Rochester Dept Elect & Comp Engn Rochester NY 14627 USA

ISBN: (纸本)0780391810

In this paper, we investigate the effects of channel noise on the performance of coordinated and non-coordinated MAC protocols. Comparative evaluations of these protocols under a perfect channel assumption have shown that coordinated MAC protocols, which regulate channel access locally, outperform non-coordinated channel access schemes in terms of energy efficiency and throughput. However, coordinated MAC protocols are more vulnerable than non-coordinated MAC protocols to channel noise due to their dependence on the robustness of the control traffic. In order to observe the degradation in performance of a coordinated MAC protocol (MH-TRACE), we investigate the impact of losing control packets. Furthermore, the performance in terms of throughput, delay, and energy efficiency of both coordinated (MH-TRACE) and non-coordinated (IEEE 802.11) MAC protocols is explored using a general error model that takes into account the length of the packets. Our results show that despite its higher level of vulnerability, the coordinated MAC protocol's performance is superior to the performance of the non-coordinated MAC protocol even when error rates are high.

关键词： energy-aware systems distributed networks wireless communication network protocols protocol verification algorithm/protocol design and analysis mobile communication systems access schemes

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Multiple access protocol for power-controlled wireless Access Nets

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2004年第4期3卷 307-316页

作者： Behzad, A Rubin, Z Univ Calif Los Angeles Dept Elect Engn Los Angeles CA 90095 USA

We consider ad hoc wireless networks that are configured as Mobile Backbone Networks. A hierarchical network architecture is synthesized, consisting of Access Nets (ANets) and Backbone Nets (BNets). Each ANet is managed by a (dynamically elected) Backbone Node (BN) that is equipped with higher capability (transmission and processing) modules. The BNs are chosen from currently active mobile backbone-capable nodes or are represented by (ground and/or airborne) unmanned vehicles (UVs) that are guided into selected positions. In this paper, we develop and investigate a new joint power controlled medium access control (MAC) algorithm for wireless access nets (ANets). Under our new protocol, the net backbone node instructs the ANet nodes to make power control adjustments while simultaneously allocating to them slots for the requested transmissions of their packets. This algorithm, in contrast to other employed conventional graph-based scheduling algorithms, satisfies the requirement that a minimum signal-to-interference and noise ratio (SINR) is met at all intended receivers. We show our algorithm to lead to a significant increase in the net throughput level by attaining high spatial reuse.

关键词： wireless communication graph algorithms network communications mobile communiction systems algorithm/protocol design and analysis access schemes

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