On the efficiency of PGPS-based packet and cell switching technologies for traffic with guaranteed delay

Circuit switching, suited to providing real-time services due to the low and fixed switching delay, is not cost effective for building integrated services networks because is based on static allocation of resources which is not efficient with bursty data traffic. Moreover it cannot handle flow that are not integer multiple of 64 Kb/s, preventing the usage of low bit rate codecs. This work explores the most suitable alternatives to the circuit switching technology (i.e. packet/cell switching) from the efficiency point of view, assuming that a PGPS scheduler is deployed in the network nodes. The paper defines an index to measure the efficiency of packet telephony, i.e. the volume of real-time traffic with deterministically guaranteed quality plus the amount of data carried related to the amount of network resources used. Furthermore it determines the maximum efficiency obtainable by packet networks, it compares different network technologies and it explores the problems of the deploying of low bit-rate codecs.