@conference {
	title = {Fixed Point Approximation for Multirate Multihop Loss Networks with State-Dependent Routing},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2004},
	month = {04/2004},
	abstract = {In this paper we consider a class of loss networks that have arbitrary topologies and routes of arbitrary length. Multiple traffic classes are present, each with different bandwidth requirement, and each routed according to a state-dependent routing scheme. In particular, we consider the least loaded routing method generalized to routes of arbitrary number of hops. The connection level performance metric of interest is the end-to-end blocking probability. We are interested in developing fast evaluation methods to provide reasonably accurate estimates of the blocking probability, especially under heavy traffic load. Our algorithms are based on the fixed-point method framework, also known as the reduced load approximation. In addition to what commonly examined by previous work, two more factors contribute to the complexity of the computation in the scenario under consideration in this paper. One is the state-dependent nature of the routing mechanism, the other is the possible overlapping between routes due to the general multihop topology of the network. We present two fast approximation algorithms to evaluate the blocking probability with state-dependent routing by simplifying the route overlapping computation. We discuss the computational complexity of our algorithms as well as sources of approximation error. We then compare the numerical results with that of simulation and show that our algorithms provide fairly accurate blocking probability estimates especially under heavy traffic load.},
	booktitle = {IEEE/ACM Transactions on Networking},
	pages = {pp.361 - 374}
}
@conference {
	title = {Network Design Using Hierarchical Performance Models and Multi-Criteria Optimization},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2001},
	month = {03/2001},
	abstract = {Network design and dimensioning often involve trade-offs between different objectives that sometimes may have opposing effects on design. At the same time, some objectives are mandatory while others are optional. In this paper we use the multi-objective optimization package CONSOL-OPTCAD for the design trunk reservation parameters. We also study link capacity design by using CFSQP along with our model and its sensitivities generated by Automatic Differentiation (AD). Using AD for sensitivity analysis of our reduced load approximation is a novel approach. Using AD for computing derivatives of the fixed point along with the calculation of the fixed point itself is both accurate and efficient. Putting together these techniques we present a systematic way of network design, regardless of the details of the underlying performance evaluation model.},
	address = {College Park, Maryland},
	booktitle = {5th ARL Federated Laboratory Symposium},
	pages = {pp. 1-6},
	organization = {University of Maryland}
}
@conference {
	title = {Performance Analysis Using a Hierarchical Loss Network Model},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2000},
	month = {11/2000},
	abstract = {In this paper we present a hierarchical loss network model for estimating the end-to-end blocking probabilities of large networks. As networks grow in size, nodes tend to form clusters geographically and hierarchical routing schemes are more commonly used. Loss network and reduced load models are often used to approximate end-to-end call blocking probabilities and hence throughput. However so far all work being done in this area is for flat networks with flat routing schemes. We aim at developing a more efficient approximation method for networks that have a natural hierarchy and/or when some form of hierarchical routing policy is used. We present two hierarchical models in detail for fixed hierarchical routing and dynamic hierarchical routing policies, respectively, via the notion of network abstraction, route segmentation, traffic segregation and aggregation. Computation is done separately within each cluster (local) and among clusters (global), and the fixed point is obtained by iteration between local and global computations. We present results from both numerical experiments and discrete event simulations.},
	address = {San Fransisco, CA},
	booktitle = {IEEE Globecom 2000,Comunications: The Global Bridge},
	pages = {pp. 1793-1797}
}
@conference {
	title = {A Hierarchical Loss Network Model For Performance Evaluation},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2000},
	month = {03/2000},
	abstract = {In this paper we present a hierarchical loss network model for estimating the end to end blocking probabilties for large networks .As network grows in size,nodes tend to form clusters geographically and hierarchical routing schemes are more commonly used. Loss networks are reduced load models are often used to approximate end to end call blocking probabilities and hence throughput.},
	address = {College Park, Maryland},
	booktitle = {ATIRP 4th Annual Conference},
	organization = {University of Maryland}
}
@conference {
	title = {Caching and Multicasting in DBS systems},
	author = {Liu, Mingyan., Karir, Manish., Baras, John S.},
	year = {1999},
	month = {09/1999},
	abstract = {The use of caching and multicasting has been studied extensively in the context of terrestrial networks. However, the use of these technologies in a Direct Broadcast Satellite (DBS) system remains unclear. In this paper, we discuss possible choices of caching and multicasting schemes, motivated by current applications in the terrestrial Internet, that could be considered for a DBS system. We examine their advantages and disadvantages as well as the tradeoffs involved in combinations of different approaches. We also propose some uses of these technologies and describe an architecture that enhances the performance and efficiency of a DBS system.},
	address = {Aizu, Japan},
	booktitle = {1999 International Workshop on Group Communications},
	pages = {pp. 56-61}
}
@conference {
	title = {Hybrid Internet Simulation Testbed},
	author = {Liu, Mingyan., Karir, Manish., Raissi-Dekhordi, Majid., Baras, John S.},
	year = {1999},
	month = {08/1999},
	abstract = {Internet technology as a widely accepted modern telecommunication standard has been widely extended to combine with numerous other technologies, e.g..,satellite, ATM, wireless. This is what we term as Hybrid Internet. Along with this technology emerging, various enhancements and alterations of standard TCP/IP for different purposes have been proposed and studied in-tensively. More and more frequently we are facing the question of how to choose from these different schemes to design a system for a particular purpose, which would inevitably involve the interaction and trade-of study. We believe that simulation is a powerful tool for this type of work. In this paper, we describe our implementation of a Hybrid Internet testbed which includes a series of traffic models and TCP/IP enhancements. The goal of our work is to make a set of reusable modules upon which we can build complex systems to study the standard protocols and their variations. We also present application examples using these module components.},
	address = {Washington DC},
	booktitle = {Proceedings of the 1999 OPNET Annual Technology Conference (OPNETWORK)},
	pages = {pp. 1-6}
}
@conference {
	title = {A Simulation Study of Enhanced TCP/IP Gateways for Broadband Internet over satellite},
	author = {Karir, Manish., Liu, Mingyan., Barrett, Bradley A., Baras, John S.},
	year = {1999},
	month = {08/1999},
	abstract = {The demand for Internet bandwidth has been growing rapidly over the years and the use of high bandwidth satellites has been proposed as one possible solution to meet the increasing demand. However, there are certain performance problems with providing Internet over satellite due to the nature of TCP/IP protocol suite and the satellite link characteristics. In this paper we describe a simulation study of architecture for improving the performance of TCP/IP over satellite links. On each end of satellite link, there are gateways that split the TCP ~connection so that the satellite link is transparent to the end hosts. The split TCP connection over the satellite segment is then optimized. TCP connection control is maintained on each segment of the split connection. We simulated such an architecture in OPNET and present results showing improved throughput over the satellite link.~},
	address = {Washington DC},
	booktitle = {OPNETWORK \&rsquo;99},
	pages = {pp. 1-6}
}
@conference {
	title = {Modeling and Simulation of Large Hybrid Networks},
	author = {Liu, Mingyan., Baras, John S., Payne, Stephen Marshall., Harrelson, Hal.},
	year = {1999},
	month = {02/1999},
	abstract = {This paper describes a modeling and simulation framework for large Hybrid networks that includes satellites framework for large hybrid networks that include satellites, terrestrial wireless and mobile and ad hoc networks. The purpose of simulation framework is to parallel the actual implementation of a testbed network currently being constructed at ARL. The modelling framework uses the performance measures generated by simulation to analytically study larger scaled versions of the testbed networks. The combination of two methodologies allows the feasibility of the testbed architecture{\textquoteright}s widespread implementation to be studied without the associated costs of performing such experiments with actual equipment. Additionally, technological tradeoffs and interoperability issues can be studied so that informed decisions can be made about the implementation of future military communication networks.

~

~

~

,terrestrial wireless and mobile Ad Hoc networks.The purpose of simulation framework is to parallel the actual implementation of the test bed network currently being constructed at ARL.},
	address = {College Park, Maryland},
	booktitle = {3rd Annual Conference on Advanced Telecommunications and Information Distribution Research Program(ATIRP)},
	pages = {pp. 201-206},
	organization = {University of Maryland}
}
@conference {
	title = {Performance Evaluation in Multi-Rate, Multi-Hop Communication Networks with Adaptive Routing},
	author = {Liu, Mingyan., Baras, John S., Misra, Archan.},
	year = {1998},
	month = {02/1998},
	abstract = {Accurate performance evaluation has always been an important issue in network design and analysis. Discrete event simulation has been known to be accurate but very time consuming. Thus analytical methods/approximation is necessary for real time estimation, large scale network optimization and sensitivity analysis. In a circuit-switched loss network, a~particular performance metric of interest is the end-to-end blocking probability. Various analytical approaches and approximation schemes have been suggested for this problem and among them, the fixed-point method, or reduced load method, has ~received~much attention. However, most of these schemes either consider only single traffic rate situations or multi-rate traffic under fixed routing. We develop an approximation scheme to estimate end-to-end blocking probability in a multi-rate multi-hop network with an adaptive routing scheme. The approximation results are compared with that of discrete event simulation. An example of application is also provided in which the proposed scheme is linked to the optimization tool CONSOL-OPTCAD to get network design trade-offs. The method described here is readily applicable to accurate performance evaluation of military networks which are often large and hybrid.},
	address = {College Park, Maryland},
	booktitle = {ARL Federated Laboratory 2nd Annual Conference},
	pages = {pp. 136-140},
	organization = {University of Maryland}
}
@conference {
	title = {Hierarchical, Layered Modeling and Performance Evaluation of Hybrid Communication Networks},
	author = {Baras, John S., Corson, Scott M., Jang, Kap D., Liu, Mingyan., Misra, Archan., Xie, Hui.},
	year = {1997},
	month = {11/1997},
	abstract = {Commercial and military networks are rapidly becoming hybrid networks;~that is interconnected wireless terrestrial, wireline terrestrial and satellite networks. There is a great need for software tools to design, model and also do performance analysis efficiently for such large heterogeneous networks. This is the topic addressed in this paper. The hybrid network modeling and performance evaluation tool is currently under development at the University of Maryland. The tool consists of an algorithmic structure and a software architecture. The algorithm is hierarchical in form, deriving its structure from that of the network which follows the network{\textquoteright}s routing hierarchy. At each level, a node represents a set of nodes at a lower level. The boundary of a node is characterized by a set of statistical models. The statistics and their parametric representations for the models of the level 1 nodes are obtained from the OPNET simulations which are run offline. The model defines procedures that convey modeling, simulation and performance data up and down the hierarchy of models. We consider the following performance metrics only: end-to-end delay, throughput, blocking probabilities, cell or packet loss rate. We describe algorithms based on loss network approximations and fast progressive solutions of resulting fixed point equations.},
	address = {Monterey, CA},
	booktitle = {MILCOM \&rsquo;97},
	pages = {1-5}
}
@conference {
	title = {Tactical and Strategic Communication Network Simulation and Performance Analysis},
	author = {Baras, John S., Corson, Scott M., Doan, Khoa., Jang, Kap D., Liu, Mingyan., Misra, Archan., Xie, Hui.},
	year = {1997},
	month = {01/1997},
	abstract = {We describe a framework for the efficient modeling and performance evaluation of large networks consisting of a mixture of strategic and tactical components. The method emphasizes hierarchical, layered techniques that are fed parametric models at the lower level. In addition to the algorithmic structure, and some initial algorithms we describe an object-oriented software architecture that is under development to support these algorithmic methods in a distributed environment.},
	address = {College Park, MD},
	booktitle = {First ATIRP Annual Conference: Advanced Telecommunications/Information Distribution Research Program},
	pages = {pp. 343-347},
	organization = {University of Maryland}
}
@article {
	title = {Fixed Point Approximation for Multirate Multihop Loss Networks With State-Dependent Routing},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2004},
	month = {04/2004},
	abstract = {In this paper, we consider a class of loss networks that have arbitrary topologies and routes of arbitrary length. Multiple traffic classes are present, each with different bandwidth requirement, and each routed according to a state-dependent routing scheme. In particular, we consider the least loaded routing method generalized to routes of an arbitrary number of hops. The connection level performance metric of interest is the end-to-end blocking probability. We are interested in developing fast evaluation methods to provide reasonably accurate estimates of the blocking probability, especially under heavy traffic load. Our algorithms are based on the fixed-point method framework, also known as the reduced load approximation. In addition to what commonly examined by previous work, two more factors contribute to the complexity of the computation in the scenario under consideration in this paper. One is the state-dependent nature of the routing mechanism, the other is the possible overlapping between routes due to the general multihop topology of the network. We present two fast approximation algorithms to evaluate the blocking probability with state-dependent routing by simplifying the route overlapping computation. We discuss the computational complexity of our algorithms as well as sources of approximation error.We then compare the numerical results with that of simulation and show that our algorithms provide fairly accurate blocking probability estimates especially under heavy traffic load.},
	pages = {pp. 361- 374},
	volume = {Vol. 12},
	number = {No. 2},
	journal = {IEEE/ACM Transactions on Networking}
}
@techreport {
	title = {Hierarchical Modeling for Network Performance Evaluation},
	author = {Liu, Mingyan.},
	year = {2000},
	month = {01/2000},
	abstract = {As networks grow in size, nodes tendto form clusters geographically and hierarchical routing schemes are morecommonly used, and it is important that network modeling methods havescale-up capabilities. Loss networks and reduced load/fixed point modelsare often used toapproximate call blocking probabilities and hence throughput in a circuitswitched network. We use the same idea for estimating connection blockingin a data network with certain QoS routing schemes. However so far most workbeing done in this area is for flat networks with flat routing schemes.},
	number = {Number: CSHCN TR 2000-8}
}
@techreport {
	title = {Hierarchical Loss Network Model for Performance Evaluation},
	author = {Liu, Mingyan.},
	year = {2000},
	month = {01/2000},
	abstract = {As networks grow in size, nodes tendto form clusters geographically and hierarchical routing schemes are morecommonly used. Loss network and reduced load models are often used toapproximate end-to-endcall blocking probabilities, and hence, throughput. However so far all workbeing done in this area is for flat networks with flat routing schemes.},
	number = {Number: CSHCN TR 2000-1}
}
