this paper analyzes an m/m/2 queueing system with two heterogeneous servers. both servers goes on vacation when there is no customers waiting for service after this server 1 is always available but the other goes on vacation whenever server 2 is idle. the vacationing server however, returns to serve at a low rate as an arrival finds the other server busy. the system is analyzed in the steady st...

Service providers within an enterprise network are often governed by client service contracts (CSC) that specify, among other constraints, the rate at which a particular service instance may be accessed. The service can be accessed via multiple points in a proxy tier configuration. The CSC and thus the rate specified have to be collectively respected by all the middleware appliances. The applia...

The rate constraint of transmitting multiple priority classes over a time-varying service-rate channel is studied in this work. This constraint specifies the maximum data rate that can be transmitted reliably with QoS (quality of service) guarantee. In our framework, the time-varying service channel is modeled by an N-state discrete Markov process, where each Markov state is associated with a c...

The optimal tradeoff between average service cost rate, average utility rate, and averagedelay is addressed for a state dependent M/M/1 queueing model, with controllable queue lengthdependent service rates and arrival rates. For a model with a constant arrival rate λ for all queuelengths, we obtain an asymptotic characterization of the minimum average delay, when theaverage serv...

A rate-based congestion control algorithm is a feedback-based flow control mechanism for ABR (Available Bit Rate) service class. When the operation of the rate-based congestion control algorithm becomes unstable, it would cause several problems; fairness among connections is deteriorated, and QoS (Quality of Service) of ABR service class becomes unpredictable. In this paper, we analyze the dyna...

We consider combined rate and power adaptations in direct-sequence code-division multiple-access communications, where the transmission power and the data rate are adapted relative to channel variations. We discuss the power gain that the combined adaptations provide over power adaptation. Then, we consider an integrated voice and data transmission system that offers a constant bit rate voice s...

Background: The National Health Accounts keep track of all healthcare related activities from the beginning (i.e. resource provision), to the end (i.e. service provision). This study was conducted to address following questions: How is the Iranian health system funded? Who distribute the funds? For what services are the funds spent on?, What service providers receive the funds? Methods: The...

The Available Bit Rate (ABR) service class has been de ned by the ATM Forum. Closed-loop ratebased congestion control has been adopted by the ATM Forum as the standard approach for supporting ABR service in ATM networks. This paper examines congestion control mechanisms for ABR service and presents fundamental performance results for rate-based tra c management schemes under varying available b...

This paper addresses a shortcoming of the widely used Generalized Processor Sharing (GPS) scheduling a1 U rithm which can have significant impact on the pmviied service, however; which has been given little attention. Since, with GPS, the service rate received by a session is proportional to the number of backlogged sessions in the system, the service rate of a session may change abruptly if so...

This paper presents a novel technique to derive asymptotic expressions for rare event probabilities for random walks in the quarter plane. For concreteness, we study a tandem queue with Poisson arrivals, exponential service times and coupled processors. The service rate for one queue is only a fraction of the global service rate when the other queue is non empty; when one queue is empty, the ot...