Selective Trunk with Multiserver Reservation

We consider a queueing model that is primarily applicable to traffic control in communication networks that use the Selective Trunk Reservation technique. Specifically, consider two traffic streams competing for service at an n-server queueing system. Jobs from the protected stream, stream 1, are blocked only if all n servers are busy. Jobs from the best effort stream, stream 2, are blocked if n-r,  r≥1, servers are busy. Blocked jobs are diverted to a secondary group of c-n servers with, possibly, a different service rate. We extend the literature that studied this system for the special case of r=1 and present an explicit computational scheme to calculate the joint probabilities of the number of primary and secondary busy servers and related performance measures. We also argue that the model can be useful for bed allocation in a hospital

Communication Network Design and Evaluation Using Shadow Prices.

We use shadow prices to measure the rate of change of performance functions of a communications network with respect to incremental changes in one or more of the design parameters such as capacity, anticipated demand, reservation levels, routing proportions, etc. The ability to evaluate such shadow prices allows us to introduce designs that optimize network performance according to network-wide criteria. We present models for the evaluation of shadow prices for different cases of networks: single-rate circuit-switched networks, wireless networks, multi-rate circuit-switched networks. For these cases, we demonstrate the wide applicability of shadow price methods. We formulate the new and very useful notion of sum capacity that can be used to compare different adaptive routing schemes, we can determine the actual pricing of calls to reflect their effect on the entire network, we trade off new call blocking with the forced termination of calls due to handoff drops in wireless networks, we dimension networks to achieve a prescribed set of new call and handoff blocking probabilities, we determine the tradeoffs between calls of different rates in multi-rate networks. We also point out problems of current interest which can be addressed by the shadow price framework and outline a brief methodology

Optimal admission policies for small star networks

In this thesis admission stationary policies for small Symmetric Star telecommunication networks in which there are two types of calls requesting access are considered. Arrivals form independent Poisson streams on each route. We consider the routing to be fixed. The holding times of the calls are exponentially distributed periods of time. Rewards are earned for carrying calls and future returns are discounted at a fixed rate. The operation of the network is viewed as a Markov Decision Process and we solve the optimality equation for this network model numerically for a range of small examples by using the policy improvement algorithm of Dynamic Programming. The optimal policies we study involve acceptance or rejection of traffic requests in order to maximise the Total Expected Discounted Reward. Our Star networks are in some respect the simplest networks more complex than single links in isolation but even so only very small examples can be treated numerically. From those examples we find evidence that suggests that despite their complexity, optimal policies have some interesting properties. Admission Price policies are also investigated in this thesis. These policies are not optimal but they are believed to be asymptotically optimal for large networks. In this thesis we investigate if such policies are any good for small networks; we suggest that they are. A reduced state-space model is also considered in which a call on a 2-link route, once accepted, is split into two independent calls on the links involved. This greatly reduces the size of the state-space. We present properties of the optimal policies and the Admission Price policies and conclude that they are very good for the examples considered. Finally we look at Asymmetric Star networks with different number of circuits per link and different exponential holding times. Properties of the optimal policies as well as Admission Price policies are investigated for such networks

Fast parallel solution of fixed point equations for the performance evaluation of circuit-switched networks

Massively parallel algorithms are presented for solving systems of fixed point equations, modeling state-dependent routing in large asymmetric circuit-switched networks. Our focus is on the Aggregated Least Busy Alternative (ALBA) routing policy of Mitra, Gibbens and Huang. On a 16384 processor MasPar parallel computer, about a minute is required to compute estimates of the call blocking probabilities for every node-pair, for realistic networks of over 100 nodes. A few hours are required on a high speed workstation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31594/1/0000523.pd

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression