Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item Modeling the Impact of Protocols on Traffic Burstiness At Large Timescales in Wireless Multi-Hop Networks(2013-04) Jain, Kaustubh; Baras, John S.We investigate the impact of the protocol stack on traffic burstiness at large time-scales in wireless multi-hop network traffic. Origins of traffic burstiness at large scales (like its LRD nature) have been mostly attributed to the heavy-tails in traffic sources. In wired networks, protocol dynamics have little impact on large time-scale dynamics. However, given the nature of wireless networks, the MAC and routing layers together can lead to route flapping or oscillations even in a static network. Hence, we explore whether these dynamics can lead to traffic burstiness and LRD. Using network simulations, we analyze traffic for two MANET routing protocols - OLSR and AODV. By varying the routing protocol parameters, we analyze their role in inducing or preventing route oscillations, and study their impact on traffic LRD. We find that, losses in OLSR control packets, due to congestion at the MAC, can lead to route oscillations and traffic burstiness at large timescales. By tuning the parameters, route oscillations and traffic LRD can be avoided. AODV dynamics show little evidence for traffic LRD, even though we cannot rule out this possibility. We also show that the route oscillations can have heavier body and tail than exponential distribution, and that the Markovian framework for route oscillations is inadequate to explain the observed traffic scaling. Lastly, we give a model that captures the MAC and OLSR routing protocol interactions and depending upon chosen protocol parameters and input load, correctly predicts the presence of traffic LRD. Thus, we use this model to design appropriate choice of protocol parameters to mitigate traffic burstiness at large-timescales.Item Studying Real-time Traffic in Multi-hop Networks Using the EMANE Emulator: Capabilities and Limitations(2011) Jain, Kaustubh; Roy-Choudhary, Ayan; Somasundaram, Kiran K.; Wang, Baobing; Baras, John S.In this paper, we study the fidelity of an open-source software emulator to provide reliable estimation of performance for real-time traffic in mobile ad-hoc networks. We emulate the IEEE 802.11 MAC/PHY (DCF) using the EMANE software emulator deployed on a cluster and run experiments for different multi-hop wireless scenarios with the Optimized Link State Routing (OLSR) protocol. As an instance of real-world usage scenario, we study the performance of real-time streaming media over a mesh network supported by OLSR. In particular, we study the effect of mobility and background traffic on carried load, delay and jitter. As another application, we analyze the impact of the wireless network on the self-similarity of aggregate traffic. Using traffic source models with high variability, we show that the aggregate traffic in the wireless network is self-similar and hence preserves its burstiness at larger time scales. The results are consistent with those obtained from high-fidelity simulation within some limitations of the emulator.Item Study of OLSR for Real-time Media Streaming over 802.11 Wireless Network in Software Emulation Environment(2010-07) Jain, Kaustubh; Somasundaram, Kiran; Wang, Brian; Baras, John; Roy-Chowdhury, AyanIn this paper we present a setup to study the real-time traffic carrying performance of optimized Link State Routing (OLSR) protocol using software emulation. We emulate the IEEE 802.11 MAC/PHY using the EMANE software emulator, on a cluster of machines, for different multi-hop wireless scenarios. As an instance of real-world usage scenario, we study the performance of real-time streaming media over a mesh network supported by OLSR. In particular, we study the effect of mobility and background traffic on carried load and jitter. We propose to extend this emulation setup to test the real-time performance of prototype routing protocols such as Stable Path Topology Control (SPTC) and other real-time applications.Item Distributed Topology Control for Stable Path Routing in Multi-hop Wireless Networks(2010-03) Somasundaram, Kiran; Baras, John; Jain, Kaustubh; Tabatabaee, VahidIn this paper, we introduce the stable path topology control problem for routing in mobile multi-hop networks. We formulate the topology control problem of selective link-state broadcast as a graph pruning problem with restricted local neighborhood information. We develop a multi-agent optimiza- tion framework where the decision policies of each agent are restricted to local policies on incident edges and independent of the policies of the other agents. We show that under a condition called the positivity condition, these independent local policies preserve the stable routing paths globally. We then provide an efficient algorithm to compute an optimal local policy that yields a minimal pruned graph, which we call the Stable Path Topology Control (SPTC) algorithm. Using simulations, we demonstrate that this algorithm, when used with the popular ETX metric, outperforms topology control mechanisms commonly used for Mobile Ad Hoc Networks.Item Distributed Topology Control for Stable Path Routing in Mobile Ad Hoc Networks(2009-11-25) Somasundaram, Kiran; Jain, Kaustubh; Tabatabaee, Vahid; Baras, JohnItem Distributed Topology Control for Stable Path Routing in Mobile Ad Hoc Networks(2009-12-09) Somasundaram, Kiran K.; Jain, Kaustubh; Tabatabaee, Vahid; Baras, John S.In this paper, we introduce the stable path topology control problem for routing in Mobile Ad Hoc Networks (MANETs). We formulate the problem as a constrained multiagent optimization problem with only local neighborhood information. We develop and prove local pruning strategies that solve this problem. We also introduce the notion of distorted pruning, which offers a systematic method to trade path stability off against the hop count metric. Finally, we quantify the performance of our pruning algorithms using several simulation scenarios.