Adjusting the Ratio of the Clock Rates in a PDA System to Reduce the Jitter through Wireless VoIP

Y.-W. Bai and Y.-D. Cheng (Taiwan)


VoIP (voice over internet protocol), Jitter, PDA, Clock rate


In this paper we propose a setting method to adjust the ratio of the CPU, RAM and BUS clock speeds of a PDA to balance the processing time and reduce the jitter of the arrival voice packets. To maintain the balance and fluency among compression, encoder-decoder, memory access and processing for voice packets, we shall lessen the clock delay to thus reduce jitter and reach the QoS of VoIP through the wireless PDA telephone. We use a queueing model to represent the service pattern of the CPU, RAM and BUS of the PDA system. The ratio of the service rates becomes one of the critical factors in reducing the jitter of the VoIP based on a systematic adjusting method. We also use a queueing equivalent model to represent the processing performance, carry out physical measurement and compare model and measurement. From a comparison of all combinations of the clock ratio, we see an improvement and matching of the processing performance of a PDA which can reduce delay and jitter and which also improves the QoS of the network telephone.

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