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UBC Theses and Dissertations

Channel usage statistics and cellular digital packet data : channel selection strategies in cellular telephony systems Jedrzycki, Christopher Mark


In order to prevent high rates of blocking, channel utilization in analog cellular mobile radio networks is significantly lower than 100%. The idle channels can be used to extend various information services to mobile users by overlaying a secondary packet-switched data service over the conventional circuit-switched voice service. This task is currently performed by the Cellular Digital Packet Data (CDPD) service. The throughput and utilization of the CDPD service depends to a large extent on the Advanced Mobile Phone System (AMPS) traffic statistics. These statistics have only been approximated and have never been verified with real data in current open literature. This thesis presents traffic data obtained from BC Tel Mobility, a cellular service provider, and describes the AMPS channel holding time and call inter arrival time distributions. The channel holding time is not best approximated by the negative exponential distribution as usually stated in literature. The lognormal distribution proves to be a much closer fit. Several spikes have to be added to this distribution to account for immediate handoff candidacy. The AMPS traffic statistics are then used to study the channel holding time of the CDPD service. The channel assignment strategy used for assigning channels to new calls in the AMPS and CDPD services is studied and a recommendation as to which is the optimal combination is made. The optimal channel assignment strategy results in the CDPD service being interrupted only when the new AMPS call finds no other idle channels in the cell site than the CDPD channel. The study considers factors which affect the CDPD channel holding times such as AMPS traffic levels, number of channels in the cell site and number of CDPD streams at the cell site. The study concludes with the effect of all these factors on the utilization of the CDPD service.

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