یک رشته هیبریدی جدید برای کاربردهای ثانویه چند طبقه در شبکه های رادیویی شناختی

Recently, service differentiation in cognitive radio networks is an important issue. Delay-sensitive traffic such as VoIP transmission is given a higher priority over delay-insensitive traffic such as data transmission. Modeling such situation using classical preemption or non-preemption priority service disciplines may result in a severe degradation of the QoS for a particular class. To address this problem, we propose a hybrid service discipline at which low priority secondary users are no longer preempted by high priority secondary users when their number of interruptions reaches a certain threshold value. We carefully design this novel service discipline taking into account that the arrival of a primary user always preempts any secondary user ongoing transmission. Analytical formulas are derived for the extended data delivery time, the overall system time and the dropping probability for each class. Based on a set of numerical results presented for a 2-class network, it is shown that adjusting the threshold value according to the performance metric of interest provides a promising performance.