Raja Harinath

Revenue-based call admission control for wireless cellular networks

Call admission control (CAC) schemes in wireless cellular networks attempt to reduce call dropping probability possibly at the expense of increased call blocking probability. We propose using channel reassignments in a controlled manner to minimize call dropping while maintaining high spectrum utilization. Guard channels are used to control the number of reassignments. The number of guard channels is dynamically determined using reassignment frequency as feedback. A simple scheme that attempts to maintain the number of reassignments under a specified target is described. A revenue-based CAC scheme is then presented which attempts to maximize income by balancing the penalty for reassignments against the reward for serviced calls. Simulation results confirm and validate the ideas discussed.

Coverage-aware proxy placement for dynamic content management over the Internet

In an effort to differentiate service quality, service providers have resorted to employing Content Distribution Networks (CDNs) over the Internet CDNs deploy geographically distributed proxy servers which manage content on behalf of the service providers servers for better performance and enhanced availability. In this paper we explore the proxy placement problem for content distribution over the Internet. Its goal is to strategically place a number of proxies in the network to optimize certain criteria which improve performance of proxies. We motivate the various necessary factors and constraints that need to be taken into account for a good placement of proxies over the Internet which reflect real world scenario more accurately and which we claim hitherto has not been completely addressed. We introduce a novel concept of host coverage characterizing every Autonomous Systems (AS) and use this stable, coarse grained measure as a long-term estimate of the load being serviced by the proxy system. We then pose an optimal formulation of the proxy placement problem taking into consideration all the relevant factors. We propose a couple of proxy placement algorithms that solve the above problem and analyze their behavior. Finally we present the performance of those algorithms against the optimal solution and other schemes proposed in literature. We also study the stability of the proposed algorithms through a variety of experiments.

Experiences with an object oriented framework for distributed control applications

This paper describes our experiences with the design and implementation an object-oriented framework for distributed control applications. The salient features of our framework are briefly explained. Next, the paper explores the challenges faced in integrating commercial off-the-shelf (COTS) object-oriented products into the framework, and how it affected the design and implementation.

A multimedia programming toolkit/environment

This paper provides details and implementation experiences of a multimedia programming language and associated toolkits. The language, a data-flow paradigm for multimedia streams, consists of blocks of code that can be connected through their data ports. Continuous media flows through these ports into and out of blocks. The blocks are responsible for the processing of continuous media data. Examples of such processing include capturing, displaying, storing, retrieving and analyzing their contents. The blocks also have parameter ports that specify other pertinent parameters, such as location, and display characteristics such as geometry, etc. The connection topology of blocks is specified using a graphical editor called the Program Development Tool (PDT) and the geometric parameters are specified by using another graphical editor called the User Interface Development Tool (UIDT). Experience with modeling multimedia presentations in our environment and the enhancements provided by the two graphical editors are discussed in detail.

Elastic flows with deadlines: a QoS abstraction for middleware

Media flows have been classified into streaming flows and elastic flows. Traditionally, admission control schemes, in middleware systems and otherwise, have dealt with streaming flows. In the Internet context, elastic TCP flows have been considered for admission control more recently -- the aim being to ensure that they actually complete. In this paper, we present a simple reservation-based abstraction for middleware systems: an elastic flow with deadlines, that includes streaming flows as a special case. We use this specification in a simple model of a link. We then present a novel way to view the problem, as a maximum network flow problem. We show that this formulation also provides an admissible schedule for the flows. We then study the incremental version of the admission control problem, and present some heuristics. We finally briefly explore potential applications of this abstraction.