Analysis of an access control mechanism for data traffic in an integrated voice/data wireless CDMA system

Mandayam and Boltzman (see MILCOM'95, San Diego, California, 1995) studied an access protocol for short data messages in an integrated voice/data CDMA system. It was assumed that voice traffic had priority and was less tolerant to delay than data traffic. Hence, the transmission of data traffic could be controlled to guarantee acceptable quality of service for voice. The data messages were of short duration and as a result, closed loop power control for them was not possible. The access protocol considered was an extension of a proposal by Viterbi (see Communications & Cryptography, p.42, 1994), which was for data-only systems. A slotted system was considered for data. At the end of every slot, the base station would control the transmission of data users by increasing/decreasing data permission probability. Measured QoS for voice was the criterion. An approximate model wherein a one-dimensional Markov chain of just the persistence state was considered and solved explicitly. Imperfect power control for voice was accounted for. In this work, the protocol is studied in greater detail. Stability of the protocol is investigated and critical data load values developed. The results also show that at high data loads additional admission control such as limited retries will be necessary to maintain stability. Simulation results show good agreement with the analysis, in the desirable operating regions.