Performance of a cognitive radio network with tolerable service degradation

Abstract

Abstract-We analyze the performance of a cognitive radio wireless network, where secondary users opportunistically share the radio spectrum with primary users through spectrum sensing and may cause service degradation to the primary users due to unreliable spectrum sensing. When a secondary user occupying a channel detects the presence of a primary call arriving to the channel, it switches from its current channel to another channel, if one is available, to continue its service; however, if the secondary user fails to detect the presence of the primary call, it remains on the channel and both calls will receive degraded service. Based on a queueing network model, we derive closedform solutions for the equilibrium system state in terms of generating functions, and derive several performance metrics of interest. In particular, we introduce the system supportability metric to evaluate the extent to which the system can support secondary users and the interference factor to evaluate the degree of service degradation imposed on primary users by the secondary users. Numerical results are presented to show the impact of system parameters on the derived performance metrics.

Channel Assembling with Priority-Based Queues in Cognitive Radio Networks: Strategies and Performance Evaluation

“…However, the spectrum scheduling scheme in [10] provides less spectrum adaptation flexibility compared with the channel access strategy proposed in this paper. In [11], a CRN was modeled using a queuing model to evaluate service degradation experienced by PUs due to SUs' incorrect spectrum sensing. A notable feature of the model presented in [11] is that each channel in the system is considered as a single server queuing system and the preempted SU services will not be dropped, instead they will enter a queue associated with another channel.…”

“…In [11], a CRN was modeled using a queuing model to evaluate service degradation experienced by PUs due to SUs' incorrect spectrum sensing. A notable feature of the model presented in [11] is that each channel in the system is considered as a single server queuing system and the preempted SU services will not be dropped, instead they will enter a queue associated with another channel. In the CRN context, a preempted SU service is an SU service which is forcibly terminated due to the arrival of a PU service.…”

“…In the CRN context, a preempted SU service is an SU service which is forcibly terminated due to the arrival of a PU service. Obviously, the network model in [11] is not suitable for delay-critical applications due to long waiting times. In our work, this particular problem is avoided by introducing multiple queues which have different priority levels and finite buffer sizes.…”

On spectrum allocation strategies in Cognitive Radio Networks

“…A queuing network model for spectrum sharing between PUs and SUs was introduced in [51], where a closed form solution for equilibrium system state was derived in the form of a generating function. The model studies PUs QoS degradation due to unreliable SUs spectrum sensing where an SU keeps on using the channel, although a PU has arrived to the same channel.…”

“…Besides, an SU moves from its channel to another only when it is interrupted by a PU arrival. Channels are assumed symmetric in terms of service rate for PUs and SUs in [50,51].…”