Erlang capacity in coordinated cognitive radio networks with stringent-delay applications

Due to the unpredictable nature of channel availability, supporting the quality of service (QoS) of stringent delay sensitive traffic in cognitive radio networks (CRNs) is very challenging. Stringent delay sensitive calls in CRNs are susceptible to forced termination due to the preemptive resource occupancy priority of primary users. To enable more efficient usage of the spectrum while improving the QoS experienced by secondary users (SUs), dynamic spectrum leasing (and coordinated cognitive radio) of resources has been previously proposed in the literature. In this paper, the Erlang capacity in coordinated cognitive radio networks with real-time hard delay constraint traffic as function of the rented resources is analytically calculated. For the adequate and fair performance comparison, call admission with fractional channel reservation to prioritize ongoing secondary calls over new ones is considered. From numerical results, it is observed that in CRNs exists a critical utilization factor of the primary resources from which it is not longer possible to guarantee the required QoS of SUs and, therefore, delay sensitive services cannot be even supported in cognitive radio networks. Thus, spectrum leasing can be essential for CRN operators to provide the QoS demanded by delay sensitive services. Then, the cost per capacity Erlang as function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.