Performance of a mobile data communication system

Evaluating the performance of a mobile data communication system by calculating the system response time as a function of the system load is considered. When the system load is raised, the response time increases. When the system load reaches a certain level (the maximum throughput), the response time approaches infinity. Consequently, throughput comes as a byproduct of the response time calculations. The system response time is the total time a transaction spends in the system. An iterative method is used to calculate the time a transaction spends on the radio channel. The elapsed time of the transaction at other system components is calculated using either M/M/1 queueing or nonpreemptive priority queueing formulas. A specific system is used to demonstrate the calculations. Contention, received signal level, short-term fading, power-up time, unequal message lengths, multisite receivers, and service area are included in the radio channel calculations. Results indicate that multiple sites improve the RF channel performance in that fewer retries are needed for each message transmission.<
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