This tutorial presents recent developments in the management of communications services and applies broadly to services involving the leasing of shared resources. These problems are more realistically modeled by queues with time-varying rates or more simply, dynamic rate queues. We first provide a review and summary of relevant results for various fundamental dynamic rate queues. The focus here is on approximations of these queueing models by low-dimensional dynamical systems. The dynamic optimization of constrained dynamical systems is based on the calculus of variations and its various incarnations over the past three centuries. We discuss these methods in the context of Lagrangians, Hamiltonians, and Bellman value functions. Finally, we provide examples where we apply these optimization techniques to dynamic rate queues motivated by communications decision problems.Keywords Bellman value function; calculus of variations; conservation principles; differential equations; dynamical systems; Hamiltonian; Lagrangian; Lagrange multipliers; Legendre transforms; opportunity costs; optimal control; Poisson brackets
The Operations of Communication Systems and Services
Four Canonical IssuesWe begin by discussing the operational issues motivated by the communications industry. This is the business sector that created the telephone network in the beginning of the 20th century and gave birth to the mathematical field of queueing theory. Around the middle of the 20th century, or the 1960s, queueing theory was found to have applications to the communication of computer systems. The mathematics of queueing has taken on a life of its own since then and has applications to all services involving the leasing of shared resources. A manager of a communications business has a continual interest in offering various services as efficiently as possible in terms of the company resources. We can express these concerns in terms of four canonical issues: performance, pricing, provisioning, and prioritization. The first one is that of service performance. These are metrics that predict the availability of resources needed for service to the typical, newly arriving customer. This is expressed in terms of the past demand and usage of these resources by previous customers.The second issue is service pricing. If the price is too high, then no one may use the service. If the price is too low, then the cost of the resources used by the business providing the service may exceed the revenue obtained. A decision must be made as to what is the most strategic price in terms of optimizing revenue without compromising some target level of service performance. If the general strategy for a decision can be expressed in terms of a finite set of simple steps, then we call this a policy. Since the larger goal of operations 208