The idea of background data service (BDS) is to use the idle times between voice calls in a cellular system for data transmission by conventional cellular transceivers with attached modems with no requirement for media-access contention protocols in the mobiles. When studied from this viewpoint, there appears to be useful capacity available for exploitation without impact on the foreground voice telephony system. Strategies for data session displacement and assignment can shape the distributions of active and inactive durations to suit the applications to a certain degree. The most promising approach seems to be time-sharing among sessions and the use of priorities to create permanent data sessions with a range of availabilities. Using enforced time-sharing with /spl Delta/T = 5 s, it is possible to obtain an average active time of 5.77 s after an average of only 6.77 s of inactivity for 8 equal-priority sessions in a 15 channel system loaded to 10% blocking, i.e., overloaded with voice traffic.
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