Achievable multiplexing gains for wireless PCS with packetized speech

Abstract

While there have been various proposals to approach the statistical multiplexing limit of 2.35 for packetized speech, the system capacity of wireless PCS under the constraints of maximum packet delay and loss probability has not been determined. The TDMA system is modeled as a ./D/1/K queue where the input process is an superposition of on-off sources. We then describe an imbedded Markov chain approximation and demonstrate its accuracy by simulation. The effects of allowable packet delay and TDMA frame size on system capacity are studied. We show, for example, that for 1% loss probability and maximum delay of two TDMA frame periods, the achievable multiplexing gain is only 2.05 for a 20-slot system. The bounds are useful for establishing limits on any multiple access schemes for different combinations of packet delay and loss constraints.