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Int. J. Communication Systems. 01/2011; 24:1015-1032.
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International Journal of Communication Systems 03/2010; 23(12):1632 - 1650. · 0.41 Impact Factor
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2010 IEEE Wireless Communications and Networking Conference, WCNC 2010, Proceedings, Sydney, Australia, 18-21 April 2010; 01/2010
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Int. J. Communication Systems. 01/2010; 23:1632-1650.
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Annales des Télécommunications. 01/2009; 64:325-338.
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ABSTRACT: The IEEE 802.11 DCF protocol used in multihop networks with chain topologies does not provide fair throughput to each node due to the hidden/exposed terminal problem and edge node effect. Eliminating the contention from hidden nodes is the key to providing high performance in the mesh network. We propose a token-based distributed scheduling scheme that not only guarantees throughput fairness among nodes but also allows allocation of proportional throughput among nodes.
Advanced Information Networking and Applications, 2006. AINA 2006. 20th International Conference on; 05/2006
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ABSTRACT: There has been a growing interest in multihop wireless ad hoc networks in recent years. Previous studies have shown that, when using the IEEE 802.11 DCF protocol in a wireless ad hoc network, the maximum end-to-end good put is achieved when all nodes are within transmission range of each other. The main reason is that the channel spatial reuse factor gained from the multihop network does not match the increase in additional transmission hops that a packet needs to travel in a multihop network. For a multihop network, its MAC frame delivery capacity is approximately fixed at a value dependent on its spatial reuse factor. If the offered load increases, less capacity will be spent on delivering packets that eventually reach their destinations and hence resulting in lower end-to-end goodput. The throughput and the mean frame delay will be varied for different RTS/CTS threshold values and the numbers of station. We will show that the system throughput of the multihop network is in general lower than that of a single-hop network whether the RTS/CTS mechanism is used or not.
Systems, Man and Cybernetics, 2005 IEEE International Conference on; 11/2005
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ABSTRACT: In MANETs querying routes by blind flooding often incurs redundancy, contention, and collision. These phenomena are known as the broadcast storm problem, which will degrade the network performance. To alleviate the broadcast storm problem, we propose a controlled flooding mechanism, called zone-based controlled flooding (ZCF), to improve the efficiency of rebroadcast in the route discovery phase. To quickly repair a broken link close to the destination node without enlisting the service of the source node, we also propose a one-hop broadcast recovery mechanism to locally repair the broken route, thereby minimizing the routing overhead and reducing the delay time. We employ the GloMoSim network simulator to evaluate the performance of our proposals, used in conjunction with the AODV routing protocol, which we call M-AODV, and compare it with AODV. Results show that M-AODV achieves significant performance improvement over AODV.
Wireless Networks, Communications and Mobile Computing, 2005 International Conference on; 07/2005
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ABSTRACT: A good channel assignment scheme in a multihop ad hoc network should not only guarantee successful data transmissions without collisions, but also enhance the channel spatial reuse to maximize the system throughput. It becomes very inefficient to use fixed channel assignment when the network size grows. Therefore, spatial reuse of channels becomes more important in a large multihop ad hoc network. We consider an ad hoc network with an overlaid CDMA/TDMA structure. We divide each code into time slots to form the channels. Two dynamic channel assignment (DCA) strategies, called greedy-based DCA (GB-DCA) and channel segregation DCA (CS-DCA) are proposed in a clustered wireless multihop ad hoc network. These DCA strategies are designed to make better use of available channels by taking advantage of the spatial reuse concept. We show that the bandwidth saving due to channel spatial reuse is higher than the additional bandwidth spent on the control overhead.
Personal, Indoor and Mobile Radio Communications, 2004. PIMRC 2004. 15th IEEE International Symposium on; 10/2004
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Proceedings of the International Conference on Wireless Networks, ICWN '04, June 21-24, 2004, Las Vegas, Nevada, USA, Volume 1; 01/2004
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ABSTRACT: In this paper, we analyze the throughput of the IEEE 802.11 DCF scheme using the RTS/CTS access mechanism in multi-hop ad hoc networks. The mathematical analysis is much more involved than that in a single-hop network due to the hidden node problem. A more realistic carrier sense range is considered in this paper. The impact of parameters, such as the number of stations, the packet size, and the carrier sense range, is also considered. Simulation results show good agreement with the analytical results.
Vehicular Technology Conference, 2003. VTC 2003-Fall. 2003 IEEE 58th; 11/2003
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ABSTRACT: Available bit rate (ABR) service is a service that has been developed specifically to support data traffic over the ATM network. The source of an ABR connection transmits its data according to the rate informed by the ATM network to fairly utilize available bandwidth and minimize cell loss at the ATM layer. However, most data traffic today is connected to ATM networks via Ethernet. Earlier study showed that as TCP traffic is carried over a path with concatenated EthernetATM/ABR links, the packet queues are formed at the edge device interconnecting the Ethernet and the ATM network, instead of inside the ATM network. We propose the BDP-Aware mechanism to improve the TCP performance in such an environment. It reduces the buffer requirement and improves the TCP performance without changing the TCP protocol at the hosts.
Advanced Information Networking and Applications, 2003. AINA 2003. 17th International Conference on; 04/2003
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Proceedings of the International Conference on Wireless Networks, ICWN '03, June 23 - 26, 2003, Las Vegas, Nevada, USA; 01/2003
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ABSTRACT: IP caching has been time-proven to be capable of offloading routing-lookup modules. However, in evaluating the performance of IP caching, the cache size is a dominant factor. In this paper, we propose a caching scheme, named aligned-prefix caching (APC). APC takes advantage of prefix caching to reduce the cache size requirement. However, APC requires a routing-lookup module that can indicate whether an aligned prefix is cacheable or not. Thus, we propose a marking scheme, named aligned-ancestor poisoning, for tree-based routing tables. Our trace-driven simulations show that aligned-24 prefix caching can reduce the cache size requirement by about 50%, compared with the conventional destination caching scheme.
Global Telecommunications Conference, 2002. GLOBECOM '02. IEEE; 12/2002
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ABSTRACT: Recent research on router architectures focuses on speeding up the time-consuming routing-lookup procedure by elaborate algorithms and data structures to match the ever-increasing wire-speed of fiber links. However, we observed strong temporal locality in the traffic traces collected from two TANet backbone routers. Thus, a routing cache, which is used to reuse previous routing-lookup results, can significantly offload the routing-lookup module. In this paper, we first introduce our temporal locality analysis. Then we investigate the efficiency of several routing cache replacement algorithms, which includes FIFO, LRU, random and our proposed LFU implementation alternative. The simulation results show that our proposed exponentially decayed LFU scheme provides better performance than the other algorithms, especially under small-size caches.
Communications, 2002. ICC 2002. IEEE International Conference on; 02/2002
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Journal of Systems and Software. 01/2002; 62:97-109.
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ABSTRACT: The ad hoc network is a temporary wireless system without a fixed
(wired or wireless) infrastructure. Many clustering algorithms have been
proposed to partition mobile users into clusters to support routing and
network management. Most previous studies, however, focus on algorithm
design, lacking an overall evaluation of clustering overheads. We design
a multiple access scheme for the broadcast of control messages, and
propose a new access-based clustering protocol (ABCP) whose cluster
formation is heavily influenced by the outcome of the multiple access.
By taking into account many delicate aspects in the clustering process,
the ABCP provides a generic, flexible, rapidly deployed and stable
cluster architecture for the upper layer protocols. Simulation is used
to compare ABCP with the other clustering strategy in terms of cluster
stability and overheads. Since ABCP makes clustering decision directly
based on the result of channel access, it requires fewer control
overheads and has shorter convergence time than the other clustering
criteria. We also demonstrate that the resulting cluster structure by
ABCP behaves stable in face of topology changes
IEEE Journal on Selected Areas in Communications 08/2001; · 3.41 Impact Factor
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ABSTRACT: To evaluate the behavior of TCP on a path with a wireless link, we
build a wireline-wireless network model, and assume the wireless link is
the bottleneck which causes packets to be buffered at the
wireline-wireless interface buffer. A reliable link layer protocol is
assumed on the wireless link which hides the fluctuations of the
wireless medium from TCP. We first build the link layer model and the
wireless channel Markov chain model, and use the matrix geometric method
to evaluate the packet loss probability. We then analyze the long-term
steady-state send rate and throughput of a TCP connection
Communications, 2001. ICC 2001. IEEE International Conference on; 02/2001
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IEEE Journal on Selected Areas in Communications. 01/2001; 19:1201-1210.
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ABSTRACT: This paper describes the field trial experience on the control and
coordination of an interactive videoconferencing system. The system
employs ATM and Internet networks to realize the continuous presence and
the conference control and management, respectively. Four control and
management functions are designed to closely emulate interactive
videoconferences. Unlike middleware approaches, we developed a
service-specific, programmable control and management platform for
multimedia applications. Based on the platform, a centralized
architecture is employed to realize the conference control and
management in a prototype system. Running the prototype system in Taiwan
ATM/Internet networks, we observed diverse aspects of the system
behavior. The control and coordination behavior naturally depends on the
specified service and designated architecture and noticeably reveals the
characteristics of the underlying Internet/ATM networks
Communications, 2000. ICC 2000. 2000 IEEE International Conference on; 02/2000
