@conference {
	title = {A Model Based Platform for Design and Optimization of Multi-hop 802.11 Wireless Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Jain, Kaustubh.},
	year = {2011},
	month = {10/2011},
	abstract = {We develop a loss model for multi-hop wireless networks based on IEEE 802.11 MAC. Given a multi-hop network topology, connection demands and routes, we model the working of 802.11 MAC in DCF mode to find good approximations to average MAC layer losses, service times and carried load. The model is defined as an implicit function amongst the variables in the model and solved using a fixed point approach. Further, using Automatic Differentiation (AD) on the implicit function , we perform sensitivity analysis and use it in an optimization framework. As an illustration of how this model can help in design and optimization of wireless networks, we optimize the network throughput by appropriate load splitting along multiple paths. We validate our models using network simulations.},
	address = {Miami Beach, Florida},
	booktitle = {8th ACM International Symposium on Performance Evaluation of Wireless Ad Hoc, Sensor and Ubiquitous Networks (PE-WANSUN 201},
	pages = {pp. 17-24}
}
@conference {
	title = {Distributed Topology Control for Stable Path Routing in Multi-hop Wireless Networks},
	author = {Somasundaram, Kiran K., Baras, John S., Jain, Kaustubh., Tabatabaee, Vahid.},
	year = {2010},
	month = {12/2010},
	abstract = {In 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 linkstate broadcast as a graph pruning problem with restricted local neighborhood information. We develop a multi-agent optimization 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.},
	address = {Atlanta, Georgia},
	booktitle = {49th IEEE Conference on Decision and Control (CDC 2010)},
	pages = {pp.  2342-2347}
}
@conference {
	title = {Modeling TDMA-Based USAP in JTRS MDL for Multicast and Unicast Traffic},
	author = {Perumal, Senni., Tabatabaee, Vahid., Baras, John S., Graff, Charles J., Yee, David G.},
	year = {2010},
	month = {10/2010},
	abstract = {In this paper, we develop loss network models for the hard scheduling mode (virtual circuit mode) of the reservation based USAP scheduling protocol as used in the Mobile Data Link (MDL) of the Joint Tactical Radio System (JTRS). These models are used to find performance metric estimates for both multicast and unicast traffic. USAP (Unifying Slot Assignment Protocol) is a dynamic distributed resource allocation protocol for mobile multihop wireless networks where the channel is partitioned in time and frequency. MDL creates a backbone sub-network and routes all traffic through this sub-network. For the backbone sub-network, we consider algorithms that form Connected Dominating Sets. We use loss network models that couple the physical, MAC, and routing layers effects. The effect of the MAC layer is modeled by approximating available capacity at a node. The available capacity to transmit is computed based on the USAP reservation rules and the node{\textquoteright}s 2-hop neighborhood traffic. For a given time varying scenario, we compute the performance metrics of blocking probability and throughput for both multicast and unicast traffic as a function of time. We compare the results of our model against simulation.},
	address = {San Jose, CA},
	booktitle = {2010 Military Communications Conference (MILCOM 2010)},
	pages = {pp. 1464-1469}
}
@conference {
	title = {Systems Engineering Challenges for Design and Realtime Management of Component-Enabled Wireless Ad-hoc Networks},
	author = {Austin, Mark A., Tabatabaee, Vahid., Baras, John S.},
	year = {2010},
	month = {03/2010},
	abstract = {This paper describes systems engineering challenges for the systematic design and realtime management of component-enabled wireless ad-hoc networks. At the front end of development, emphasis is placed on the use of goals and scenarios, and visual modelling abstractions for elicitation of models for required functionality. We assume that network nodes will be implemented as hierarchies of interconnected sub-components. To maximise system reliability and simplify technology upgrades we advocate the use of formal approaches to component interface definition, and to validation of component and system-level functionalities.},
	address = {Hoboken, NJ},
	booktitle = {Proceedings of the 8th Conference on Systems Engineering Research (CSER 2010)},
	pages = {pp. 1-10}
}
@conference {
	title = {Modeling and Sensitivity Analysis of Reservation Based USAP Unicast Traffic in MANETs},
	author = {Perumal, Senni., Tabatabaee, Vahid., Baras, John S., Graff, Charles J., Yee, David G.},
	year = {2009},
	month = {10/2009},
	abstract = {In this paper, we develop and evaluate models to estimate and optimize various performance metrics for unicast traffic using the hard scheduling (virtual circuit connection oriented) mode of the reservation-based protocol USAP in mobile ad-hoc wireless networks (MANETs). USAP (Unifying Slot Assignment Protocol) is a dynamic distributed resource allocation protocol for MANETs. We model USAP hard scheduling mode using loss network models along with reduced link capacity that couple physical, MAC and routing layers effects. The key effect of multiuser interference on a link is modeled via reduced link capacity where the effects of transmissions and receptions in the link neighborhood are modeled using USAP reservation rules. We compare our results with simulation and obtain good results using our loss network models but with reduced link capacity distribution obtained by simulation. We also compute the throughput sensitivities with respect to network parameters and use these sensitivities to improve network performance.},
	address = {Boston, Massachusetts},
	booktitle = {MILCOM 2009 "The Challenge of Convergence"},
	pages = {pp.1-7}
}
@conference {
	title = {Component Based Modeling for Cross-layer Analysis of 802.11 MAC and OLSR Routing Protocols in Ad-hoc Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Jain, Kaustubh.},
	year = {2009},
	month = {10/2009},
	abstract = {We present a complete scenario driven component based analytic model of 802.11 MAC and OLSR routing protocols in MANETs. We use this model to provide a systematic approach to study the network performance and cross-layer analysis and design of routing, scheduling, MAC, and PHY layer protocols. The routing protocol is divided into multiple components. Componentization is a standard methodology for analysis and synthesis of complex systems. To provide a component based design methodology, we have to develop a component based model of the wireless network that considers cross-layer dependency of performance. The component based model enables us to study the effect of each component on the overall performance of the wireless network and to design each component separately. For the MAC layer, we use a fixed point loss model of 802.11 protocol that considers effects of hidden nodes and finite retransmission attempts. We have also considered simple models for PHY and scheduling. The main focus of this paper is on the integration of these models to obtain a complete model for wireless networks. In several scenario driven studies, with user-specified topologies and traffic demands, we study the performance metrics - throughput and delay. By analyzing the performances under varying network scenarios, we are able to identify a few sources of performance degradation. We also study the effect of certain design parameters on the network performance. Thus, demonstrating the ability of the model to quickly identify problem components and try alternative design parameters},
	address = {Boston, Massachusetts},
	booktitle = {MILCOM 2009 \&quot;The Challenge of Convergence\&quot;},
	pages = {pp. 1-7}
}
@conference {
	title = {Component Based Performance Modeling of Wireless Routing Protocols},
	author = {Baras, John S., Tabatabaee, Vahid., Purkayastha, Punyaslok., Somasundaram, Kiran K.},
	year = {2009},
	month = {06/2009},
	abstract = {We propose a component-based methodology for modelling and design of wireless routing protocols. Componentization is a standard methodology for analysis and synthesis of complex systems, or software. The feasibility of the component based design relies heavily on the compositionality property (i.e. system-level properties can be computed from properties of components). To provide a component based design methodology and to test compositionality for routing protocols, we have to develop a component-based model of the wireless network. We present the main components of the routing protocol that should be modelled and focus on three main components: neighborhood discovery, selector of topology information to disseminate, and the path selection components. For each component, we identify the inputs, outputs, and a generic methodology for modelling. Throughout the paper, we use the Optimized Link State Routing (OLSR) protocol as a case study to demonstrate the effectiveness of our approach. Using the neighborhood discovery component, we present our design methodology and design a modified enhanced version of this component, and compare its performance to the original OLSR design.},
	address = {Dresden, Germany},
	booktitle = {IEEE ICC 2009 Ad Hoc and Sensor Networking Symposium},
	pages = {pp.1-6}
}
@conference {
	title = {Performance Metric Sensitivity Computation for Optimization and Trade-off Analysis in Wireless Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas.},
	year = {2008},
	month = {11/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics for multihop wireless networks, including MANETs. We introduce an approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model takes into account effects of the hidden nodes, scheduling algorithms, IEEE 802.11 MAC and PHY layer transmission failures and finite packet transmission retries at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models, and develop a methodology for sensitivity analysis, parameter optimization and trade-off analysis for key wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {Loss Network Models and Multiple Metric Performance Sensitivity Analysis for Mobile Wireless Multi-Hop Networks},
	author = {Baras, John S., Perumal, Senni., Tabatabaee, Vahid., Somasundaram, Kiran K., Purkayastha, Punyaslok.},
	year = {2008},
	month = {11/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics of mobile wireless multi-hop networks, including MANETs. The method utilizes approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model considers effects of the hidden nodes, node scheduling algorithms, MAC and PHY layer failures and unsuccessful packet transmission attempts at the MAC layer in~arbitrary time-varying network topologies where multiple paths share nodes. The method then applies Automatic Di{\textregistered}erentiation (AD) to these implicit performance models, to compute sensitivities of various performance metrics with respect to net- work parameters. We demonstrate the method by applying it to time-varying mobile network topologies, including reduced connectivity instances, with both random access MAC (contention mode of the 802.11) as well as reservation-based MAC (USAP TDMA based protocol). We analyze throughput, delay and packet loss as metrics and investigate metric optimization and tradeoff analysis. Finally, we provide numerical results for realistic mobile networks with time-varying topologies.},
	address = {Maui, Hawaii},
	booktitle = {Fourth International Wireless Internet Conference (WICON 2008)}
}
@conference {
	title = {Performance Modeling of Hybrid Satellite/Wireless Networks Using Fixed Point Approximation and Sensitivity Analysis of the Performance Models for Network Design},
	author = {Roy-Chowdhury, Ayan., Tabatabaee, Vahid., Baras, John S.},
	year = {2008},
	month = {09/2008},
	abstract = {In this work, we propose a new analytical method for modeling and estimating the performance of hybrid networks that are comprised of terrestrial wireless networks interconnected by a satellite overlay. We take advantage of the natural hierarchy present in the hybrid architecture to split the network into multiple levels based on the node and link characteristics. For the lower level of terrestrial wireless nodes, we use a simple approximate (throughput) loss model that couples the physical, MAC and routing layers. The model provides quantitative statistical relations between the loss parameters used to characterize multiuser interference and physical path conditions on the one hand and traffic rates between origin-destination pairs on the other. For the higher layer consisting of the terrestrial gateway nodes interconnected by the satellite overlay, we use a simple satellite channel bit error loss model coupled with a channel access protocol, to derive a similar relationship between traffic arrival rate and the link loss. We use the technique of hierarchical~reduced loss network model, adapted for packet-switched networks, to create a reduced load network model for the hybrid network that connects the packet arrival rates in the different levels with the associated physical and link loss rates. We then apply a fixed point approximation approach for this set of relations to derive a solution that converges to a fixed point for the given set of parameters, while satisfying all the equations in the set. The result is an implicit model of the selected performance metric parameterized by the design variables. We apply the technique of Automatic Differentiation to the performance models obtained through the fixed point approximation and analyze the sensitivity of the performance metrics to variations in the selected network parameter. We thus develop a methodology for parameter optimization and sensitivity analysis of protocols to aid in the design of hybrid networks. We demonstrate the effectiveness of our approach through simulation results, compared with results from discrete event simulations on identical network topology.},
	address = {Matera, Italy},
	booktitle = {Ka and Broadband Communications Conference},
	pages = {pp. 245-253}
}
@conference {
	title = {Modelling and Optimization for Multi-hop Wireless Networks Using Fixed Point and Automatic Differentiation},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas.},
	year = {2008},
	month = {03/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics of multi-hop wireless networks, including MANETs. We introduce a simple approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model considers effects of the hidden nodes, node scheduling algorithms, MAC and PHY layer failures and unsuccessful packet transmission attempts at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models~and develop a methodology for sensitivity analysis and parameter optimization for wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.},
	address = {Berlin, Germany},
	booktitle = {6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt{\textquoteright}08)},
	pages = {pp.  295 -300}
}
@conference {
	title = {Loss Model Approximations and Sensitivity Computations for Multi-Hop Wireless Network Design},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas., Shang, Yadong.},
	year = {2007},
	month = {10/2007},
	abstract = {We develop and evaluate a new method for estimating various performance metrics of multi-hop wireless networks, including MANETs. The estimates depend implicitly on network design parameters, and therefore the method can form the basis for designing such networks so as to achieve predictable performance bounds. Explicit simulation models for large wireless networks are too complex and can not be used for analysis and design of wireless networks in realistic settings. We introduce a simple approximate (throughput) loss model that couples the physical, MAC and routing layers. The model provides quantitative statistical relations between the loss parameters used to characterize multiuser interference and physical path conditions on the one hand and traffic rates between origin-destination pairs on the other. We use a fixed point approach together with recently proposed models for the MAC layer to find a consistent solution satisfying all equations in the set. The result is an implicit model of performance metrics, such as throughput, packet loss, delay, parameterized by design variables, such as path routing probabilities, power levels, noise levels. We next apply Automatic Differentiation (AD) to these implicit performance models and develop a methodology for design and parameter selection/tuning of wireless protocols.},
	address = {Orlando, FL},
	booktitle = {2007 Military Communication Conference},
	pages = {pp. 1-7}
}
@techreport {
	title = {Distributed Topology Control for Stable Path Routing in Multi-hop Wireless Networks},
	author = {Somasundaram, Kiran K., Baras, John S., Jain, Kaustubh., Tabatabaee, Vahid.},
	year = {2010},
	month = {07/2010},
	abstract = {In this paper, we introduce the topology control problem for stable path routing in mobile multi-hop networks. We formulate the topology control problem of selective linkstate broadcast as a graph pruning problem with restricted local neighborhood information. We develop a multi-agent optimization 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, has lesser control overhead and the resulting pruned routing paths carry more upper layer traffic when compared with other topology control mechanisms commonly used for Mobile Ad Hoc Networks.}
}
@techreport {
	title = {Distributed Topology Control for Stable Path Routing in Mobile Ad Hoc Networks},
	author = {Somasundaram, Kiran K., Jain, Kaustubh., Tabatabaee, Vahid., Baras, John S.},
	year = {2010},
	month = {03/2010},
	abstract = {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.}
}
