We consider the centralized adaptive isarithmic flow control scheme proposed by Mason and Gu (1985) and studied further by Coderre (1989). These previous studies addressed "traditional" packet switched networks (low speeds). In this paper, the flow control technique is studied in the context of fast packet switching networks. The high transmission rates involved in such networks make it necessary to specifically consider propagation delays. Propagation delay is modeled by M/D//spl infin/ queues on all trunks. The previous studies presented heuristic adaptive algorithms for the controller that attempted to maximize a performance criteria: the product of powers. We present an adaptive algorithm for the controller which is a very good approximation to the optimal operation in a fast packet switching network under heavy traffic. The claim is supported by analytic results (expected operation of system) and Monte Carlo simulation results. While the control architecture has broader applicability, our frame of analysis is product form networks.>

Consideration is given to the problem of optimal flow control in a multiclass telecommunications environment where each user (or class) desires to optimize its performance while being fair to the other users (classes). The Nash (1950) arbitration scheme from game theory is shown to be a suitable candidate for a fair, optimal operation point in the sense that it satisfies certain axioms of fairness and is pareto optimal. This strategy can be realized by defining the product of individuals user performance objectives as the network optimization criterion. This provides the rationale for considering the product of user powers, as has been suggested in the literature. For delay constrained traffic, the constrained optimization problem of maximizing the product of user throughputs subject to the constraints leads to a Nash arbitration point. It is shown that these points are unique in throughput space, and the authors also obtain some convexity properties for power and delays with respect to throughputs in a Jackson network.>

A multiserver queueing system with two classes of customers is considered: a type-1 (narrowband, NB) customer requires a single server, while each type-2 (wideband, WB) customer requests n of the m servers (n is not random). Severs allocated to a type-2 customer are seized and released simultaneously. Service times are exponentially distributed with mean 1//sub mu i/ for type i customers (i=1, 2). Blocked type-1 customers are cleared while blocked type-2 customers may be delayed in an infinite waiting room. A type-1 customer enters service immediately upon arrival if at least one server is free, irrespective of the status of the type-2 queue. WB customers have restricted access to the service facility; a cutoff parameter specifies the maximum number of type-2 customers that can be in service at the same time. Two approaches, moment-generating functions and matrix-geometric techniques, are considered for the computation of the system performance, that is, the mean waiting time in queue and the probability of delay (i.e. nonzero waiting time) for type-2 customers, as well as the probability of blocking for type-1 customers.>

This paper introduces a new class of network design problems implementing an integrated teleconferencing environment consisting of a video space showing images of the participants, an audio space providing their voices, and a graphics space providing reference and discussion material for the conference. These various spaces provide services of differing quality and type. The problem posed is to design topologically optimal networks that are least costly and that will have the flexibility to carry conferences of differing service quality and type. The actual networks studied in this paper consist of the design of a private network for a single conference amongNidentical, but arbitrarily located, sites. Network designs will be minimum link-cost or constrained minimum link-cost optimal, where the first is minimal over all possible network topologies and the second is constrained to consider only those topologies that have the minimum number of links. For terrestrial systems, one of the interesting results is that classical network topologies such as rings and minimum spanning trees are optimal for some conference types. However, no topology is optimal for all types, and some topologies use their capacity very poorly when used for a type for which they were not optimized. Unlike terrestrial networks, satellite networks may be easily configured to have all of their capacity available for all conference types.

A linear programming model has been formulated and implemented for modernization problems with constraints. The complexity of the model is studied analytically and empirically as a function of problem size. A heuristic has been specified and implemented for solving the same problem. The solutions obtained by the linear program and the heuristic are compared for a modernization problem of current interest. The comparison is made on the basis of net present value of the policies selected and the time required to perform the calculations.

This paper considers a problem of telecommunications network modernization. The model presented provides the cost criterion corresponding to a general network evolution strategy which may consist of a combination of three basic policies: expansion of existing facilities; overlay of existing facilities with modern equipment to serve the growth; or replacement of existing facilities with modern equipment. The cost criterion is basically defined as the cumulated sum of all inflated discounted cash flows. Two major problems are discussed: 1) the single location or local facility evolution problem applicable to single transmission links or switching nodes and 2) the multilocation problem involving several nodes. An application of the second problem described here concerns the selection of switching equipment types for a telephony network (including remote concentrators). For both problems, simple necessary and sufficient conditions are derived for pure strategies to be optimal. Pure strategies involve events occurring at the beginning and/or end of the study horizon.

This paper considers the problem of the optimal introduction of digital switching equipment into an existing analog local telephone network. The criterion used is the present worth of annual charges. Using certain plausible assumptions, this multilocation dynamic problem is shown to reduce to an equivalent static problem. The latter can be expressed as a classical plant location problem for which several solution techniques are available in the operations research literature.

Application of learning automata theory to telephone traffic routing and control is described. Improved network performance is demonstrated through the comparative simulation of learning automata routing and the existing fixed rule alternate routing in simple telephone networks. Learning automata routing results in significantly lower blocking probability when selected overload conditions prevail and additional capacity exists elsewhere in the network.