Giulio Barberis

Analysis and Optimal Design of a Packet-Voice Receiver

The analysis problems arising from a digital packet switched speech network are outlined in a wide statistical environment. The statistical models assumed are discussed with respect to practical applications. Particular attention is devoted to a formal description of the influence of the packet voice receiver on the system behavior in terms of the delay pdf. The optimization of the system performance, in order to obtain the best voice quality, is stated as an optimal control problem, and the analysis results play a central role in the construction of the objective functions. The problem is solved in a particular analytical environment. The outlined analytical results are supported by critical comments on their comparison with practical implementations, allowing the designer a better capability in handling any problems.

Buffer Sizing of a Packet-Voice Receiver

Some analytical results have been developed for the analysis and design of a packet-voice receiver in previous work [1], namely, the delay suffered by packets because of the reassembly mechanism is described in terms of the overall delay probability density function (pdf) w(t) . This basic analytical result is used here in order to obtain the pdf b(t) of the time spent by packets in the receiver buffer. In this way, the previous work [1] is extended to analysis of the delay distribution of the receiver buffer where arriving talkspurts are delayed to compensate for the variable network delay of all packets within a talkspurt. The tools developed here facilitate a choice of the buffer size at the prescribed level of packet-loss probability.

Capacity Allocation in a DAMA Satellite System

Some analysis and design results for a circuit-switched multiaccess satellite system are presented. The use of a demand assignment multiple access (DAMA) circuit-switched service in satellite communications gives rise to many problems, recently emphasized in the literature. They recall those of an open network of queues with population size constraints. The main results are the extension of computation algorithms developed in the area of queueing networks. The analytical tools make feasible a full analysis of an important class of access disciplines in terms of blocking probability (BP). The optimal access strategy is obtained directly by analysis. Different optimization criteria are proposed and numerical examples are presented.

A Useful Tool in the Theory of Priority Queueing

A double input channel priority network, consisting of a low-priority queue with general interarrival distribution and Markovian service time and a high priority completely Markovian queue, is considered. A simple and handy estimate of the mean queue length for the two flows is presented together with its relative effectiveness. The analysis results show that the channel utilization can be improved by introducing a deterministic traffic flow without significant degradation of the high-priority queue performance. These results can be used in designing a communication network, where many packetized traffic flows with different input statistics and delay threshold requirements (packetized voice, video, and data) have to be served by the same switching and transmission facilities.