Liu Baohong

Design of a robust active queue management algorithm based on feedback compensation

Active Queue Management (AQM) is a very active research area in networking. The main objective of an AQM mechanism is to provide low delay and low loss service in best-effort service networks. In this paper we propose a new AQM algorithm based on the feedback compensation technique in control theory. The algorithm is called Proportional Integral based series compensation, and Position feedback compensation (PIP). By choosing the appropriate feedback compensation element and its parameters, the properties of the corrected system become dependent, to a great extent, on the series and feedback compensatory elements. Thus, PIP can eliminate the error incurred by the inaccuracy in the linear system model as well as eliminate the sensitivity to the changes in system parameters like load level, propagation delay, etc. The performance of PIP is compared to PI using ns simulations. From the experiments and analysis we conclude that PIP is more responsive to and robust under time-varying network conditions than PI.Active Queue Management (AQM) is a very active research area in networking. The main objective of an AQM mechanism is to provide low delay and low loss service in best-effort service networks. In this paper we propose a new AQM algorithm based on the feedback compensation technique in control theory. The algorithm is called Proportional Integral based series compensation, and Position feedback compensation (PIP). By choosing the appropriate feedback compensation element and its parameters, the properties of the corrected system become dependent, to a great extent, on the series and feedback compensatory elements. Thus, PIP can eliminate the error incurred by the inaccuracy in the linear system model as well as eliminate the sensitivity to the changes in system parameters like load level, propagation delay, etc. The performance of PIP is compared to PI using ns simulations. From the experiments and analysis we conclude that PIP is more responsive to and robust under time-varying network conditions than PI.

A Formal Description Specification for Multi-Resolution Modeling Based on DEVS Formalism and its Applications

Multi-Resolution Modeling (MRM) is a relatively new research area. With the development of distributed interactive simulation, especially as the emergence of HLA (High Level Architecture), multi-resolution modeling becomes one of the key technologies for advanced modeling and simulation. But there is little research in the area of the theory of multi-resolution modeling, especially the formal description of MRM. In this paper, a new concept for the description of multi-resolution modeling, named Multi-resolution model Family (MF) is presented. A multi-resolution model family is defined as the set of different resolution models of the same entity. The description of MF includes two parts: models of different resolution and their relations. Based on this new concept and DEVS (Discrete Event Specification) formalism, a new multi-resolution model system specification, named MRMS (Multi-Resolution Model system Specification) is proposed. Some important properties of MRMS, especially the closure of MRMS under coupling operation are given and proved. MRMS provides a foundation and a powerful description tool for the research of MRM. An example to illustrate how to describe a multi-resolution model using our specification is given. Using this description, the theory and implementation of MRM can be further studied.

A formal description specification for multi-resolution modeling (MRM) based on DEVS formalism

Multi-Resolution Modeling (MRM) is a relatively new research area. With the development of distributed interactive simulation, especially as the emergence of HLA, multi-resolution modeling becomes one of the key technologies for advanced modeling and simulation. There is little research in the area of the theory of multi-resolution modeling, especially the formal description of MRM. In this paper, we present a new concept for the description of multi-resolution modeling, named multi-resolution model family (MF). A multi-resolution model family is defined as the set of different resolution models of the same entity. The description of MF includes two parts: models of different resolution and their relations. Based on this new concept and DEVS formalism, we present a new multi-resolution model system specification, named MRMS (Multi-Resolution Model system Specification). And we present and prove some important properties of MRMS, especially the closure of MRMS under coupling operation. MRMS provides a foundation and a powerful description tool for the research of MRM. Using this description, we can further study the theory and implementation of MRM.

Introduction to the Design and Implementation of a Web-Based Meta-Synthetic System (WebSMS )

What we are proposing in this paper is the object, architecture, design and implementation of a Web-Based Simulation Meta-Synthesis, named WebSMS. The motivation of the WebSMS system is to provide services for distributed and secure sharing and reuse of resource, distributed collaboration, and distributed execution and observation of simulation. In this paper, the foundational idea of meta-synthetic is introduced firstly. Then, the architecture of the meta-synthetic framework is given and the design of the main function and its key technologies are proposed.