Measurement-driven admission control on wireless backhaul networks
People
Irfan Sheriff
Prashanth Acharya
Elizabeth M. Belding
IEEE 802.11 wireless networks perform poorly in the presence of large traffic volumes. Measurements have shown that packet collisions and interference can lead to degraded performance to the extent that users experience unacceptably low throughput, which can ultimately lead to complete network breakdown. An admission control framework that limits network flows can prevent network breakdown and improve the performance of throughput and delay-sensitive multimedia applications. In this work, we present a measurement-driven admission control scheme that leverages wireless characteristics for intelligent flow control in a static wireless network. Experiments on the 25 node UCSB MeshNet show that the proposed admission control scheme can enhance network performance such that the QoS requirements of real time applications, such as VoIP, can be met.
- Irfan Sheriff, Prashanth Acharya, Elizabeth Belding "Measurement Driven Admission Control on Wireless Backhaul Networks" To Appear in Elsevier's Computer Communications Journal, Special Issue on Wireless Mesh Networks 2008[pdf]
- Irfan Sheriff, Prashanth Acharya, Elizabeth M. Belding "Resource Estimation in Wireless Backhaul Networks" Paper, Texus, Wicon 2007 (early version) [pdf]
Multi-radio Wireless Mesh Architecture
People
Krishna Ramachandran
Irfan Sheriff
Elizabeth Belding-Royer
Kevin Almeroth
Wireless mesh routers equipped with multiple radios can alleviate capacity problems in 802.11 wireless networks. However, a practical, complete system architecture that can
realize the benefits of multiple radios does not exist. The focus of this work is to offer such an architecture. Our architecture provides solutions to challenges in three key areas. The first
is the construction of a wireless router that alleviates the interference that can occur between commodity radios within a single piece of hardware. The second is the design
of a topology controller responsible for collecting information about internal and surrounding interference; executing a channel selection algorithm; and disseminating channel assignments to
mesh routers. And the third is the design and implementation of several communication protocols, protocols that are necessary to make our architecture operational. The system that we then
implement is deployed, tested, and finally, evaluated on a 20-node multi-radio 802.11a/b wireless testbed. Our evaluation focused on multiple aspects of our architecture, such as its ability to
adapt to varying external interference levels; the performance gains offered in the presence of different traffic patterns; and the impact of changes in wireless link characteristics on system
operation.
References
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Krishna Ramachandran, Irfan Sheriff, Elizabeth Belding and Kevin Almeroth "A Multi-Radio 802.11 Mesh Network Architecture" To Appear in Mobile Networks and Applications Journal, Special Issue on Wireless Mesh Networks 2008 [pdf]
Routing Stability in Wireless Networks
People
Krishna Ramachandran
Irfan Sheriff
Elizabeth Belding-Royer
Kevin Almeroth
An understanding of the stability of routes in mesh networks is important for the design of routing protocols, and in network planning and management. We conduct two case studies, on UCSB MeshNet and MIT Roofnet, using the link quality information collected over several days. Our key findings include: wireless routes are weakly dominated by a single route; dominant routes are extremely short-lived due to route flapping; simple stabilization techniques, such as hysterisis thresholds, can provide significant improvement in route persistence.
- Krishna Ramachandran, Irfan Sheriff, Kevin Almeroth and Elizabeth Belding-Royer "Routing Stability in Static Wireless Mesh Networks" Paper, Belgium, PAM 2007. [pdf]
Data Location in Multihop Networks
People
Irfan Sheriff
Prashanth Acharya
Ashwin Sampath
Elizabeth Belding-Royer
Ben Zhao
Multihop wireless networks are ideal as infrastructures for location-aware network applications, particularly for disaster recovery operations. However, one missing component
is an efficient and scalable distributed data location service. Existing approaches impose significant communication overhead on the underlying wireless layer and generally limit the total
number of locatable objects in a network. To address this problem, we present the Integrated Data Location Protocol (IDLP), which provides scalable location of a large number of
objects by integrating compressed summaries of object signatures into the routing layer. We evaluate our approach using extensive simulations in Qualnet, as well as detailed measurements from a
deployed AODV-implementation on the UCSB MeshNet testbed. Results show that IDLP maintains low communication overhead while efficiently locating up to a hundred objects per node.
References
- Irfan Sheriff, Prashanth Acharya, Ashwin Sampath, Elizabeth Belding-Royer and Ben Zhao "Holmes: Probabilistic object location in MANETs" Poster, Boston, NSDI 2005. [pdf]
- Irfan Sheriff, Prashanth Aravinda Kumar, Ashwin Sampath, Ben Zhao and Elizabeth Belding-Royer "Integrated Data Location in Multihop Networks" Paper, Bangalore, COMSWARE 2007. [pdf]
Multimedia analysis on MeshNet
People
Irfan Sheriff
Yuan Sun
Elizabeth Belding-Royer
Kevin Almeroth
Performance evaluation and analysis of wireless networks is essential because testbed experiments facilitate a better understanding of network and application characteristics. This understanding
of performance, in turn, results in robust protocol design. In this work, we do an experimental study of multimedia traffic performance in mesh networks. We evaluate the performance of video and voice traffic through multi-hop wireless paths and study the capacity of the mesh network. We also investigate the impact of different traffic and ne
twork characteristics on application performance. The impact of different wireless network interface card configurations is examined.
References
- Yuan Sun, Irfan Sheriff, Elizabeth Belding-Royer and Kevin Almeroth "An Experimental Study of Multimedia Traffic Performance in Mesh Networks" Paper, Seattle, WitMeMo 2005. [pdf]
- Henrik Lundgren, Irfan Sheriff, Prashanth Aravinda Kumar, Anderson Lam, Joshua Miller, Kimaya Sanzgiri and Elizabeth Belding-Royer "Video Performance Analysis in the UCSB MeshNet Testbed" Demo, Santa Clara, SECON 2005 [ppt]
Multipath in Multi-radio Networks
People
Irfan Sheriff
Elizabeth Belding-Royer
Research has shown that multi-radio multi-channel mesh networks provide significant capacity gains over singleradio mesh networks. Traditional single path routing can lead to poor utilization of the available channels in these networks. Opportunistic multipath routing can better exploit the available channel diversity in a multi-radio network. The goal
of this project is to select multiple paths that, when used concurrently, provide high end-to-end throughput. To this end, we present a metric for multipath selection in multi-radio networks. We evaluate the metric through simulations in Qualnet and show that intelligent multipath routing significantly outperforms single path routing in multi-radio mesh networks.
References
- Irfan Sheriff and Elizabeth Belding-Royer "Multipath Selection in Multi-radio Mesh Networks" Paper, San Jose, Broadnets 2006 [pdf]
Effect of Payload Length Variation and Retransmissions on Multimedia in WLANs
People
Sayantan Choudhary
Irfan Sheriff
Jerry Gibson
Elizabeth Belding-Royer
Multimedia transmission over wireless local area
networks (WLANs) is a challenging task due to the varying
nature of the wireless channel as well as the inherent difference
between multimedia traffic and data traffic. In the MAC layer,
a single bit error in the packet can lead to the entire packet
being discarded. This results in a higher packet error rate for
higher payload sizes. Retransmission due to packet errors causes
the contention window to double, and this leads to a decrease
in throughput if the wireless channel does not improve for the
retransmitted packets. Hence, throughput is a function of packet
payload length as well as the maximum number of allowable
retransmissions. In this work, we investigate the effect of payload
length adaptation and retransmissions on the throughput and
capacity of multimedia users. Numerical results and simulations
reveal that careful payload adaptation significantly improves the
throughput performance at low signal to noise ratios (SNRs).
It is also observed that excessive retransmissions can reduce the
effective throughput, thereby reducing the capacity of multimedia
users in the presence of data users. Since multimedia traffic
is more latency constrained and less error constrained, this
suggests that by carefully selecting the payload length and
maximum number of allowable retransmissions based on the
channel conditions, a higher number of multimedia users can
be supported.
References
- Sayantan Choudhury, Irfan Sheriff, Jerry Gibson and Elizabeth Belding-Royer "Effect of Payload Length Variation and Retransmissions on Multimedia in WLANs" Paper, Vancouver, Canada, IWCMC 2006.[pdf]
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