- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
The usage of the radio spectrum for wireless communication is considered to be inefficient. Therefore, through cognitive radio, unlicensed users can occupy idle spectrum bands without interference with the primary user. Generally, when the arrival rate of licensed users is high, secondary users may starve. In this paper, we propose two models to improve the average total waiting time for the secondary user. They are the M/D/1 model of a primary user delay system with non-pre-emptive priority and pre-emptive priority. They are compared to an M/D/1 model with primary user delay. Numerical analysis and Monte Carlo simulation are performed for all results. Improvements in the average total waiting time of 13%-18% for primary user and 24%-32% for secondary user in the non-pre-emptive priority scheme are obtained. In the pre-emptive priority scheme, 19%-22% and 5%-7% improvement are obtained for the primary and secondary user respectively. Furthermore, same models, but with finite buffer capacity for both users are investigated to model a real-time system. In these schemes, the system improves the average total waiting time by 20%-42% for the primary user and 34%-42% for the cognitive radio with non-pre-emptive priority. Similarly, the pre-emptive model shows 25%-44% and 6%-24% reduction in the primary and secondary user waiting times respectively.