Performance of access strategies for D-TASI over mobile radio fading channels

Demand Time Assigned Speech Interpolation (D-TASI) has been proposed as a means of more efficiently using the radio spectrum allocated to mobile radio systems. In the D-TASI system, the delay experienced in accessing the message channel in order to transmit a voice packet is a major obstacle to the practical implementation of the system. Access schemes for D-TASI are the subject of this paper. Three access schemes have been proposed and their theoretical models developed; computer software packages have also been developed to simulate the three proposed schemes¿Aloha, Polling, and Table-driven. The probability of call blocking as a function of user population, voice channel traffic intensity and time-slot duration has been studied. It has been found that under fading conditions the Polling access scheme performs the best, closely followed by Slotted Aloha, The performance of the Table-driven scheme falls some way short of that of the other two schemes.