Cooperative Spectrum Access for Cognitive Radio Network Employing Rateless Code

In cognitive networks, since the secondary users are not licensed owners of the spectrum, they can only access the spectrum opportunistically and cooperatively to exploit the best effort throughput for themselves while guaranteeing that their transmissions would not break the QoS performance of the primary communications. In this paper, we consider the cognitive network in which the primary users have delay sensitive services, e.g., voice or video services, and we take the average delay constraint as primary users' QoS requirement. Three cooperative spectrum access schemes for secondary users under such constraint are proposed, based on the assumption that both the primary and secondary transmitter employ rateless coding. The average throughput of the secondary user for each scheme is calculated and compared both analytically and numerically. The impacts of system parameters and network topology on these schemes are also illustrated via numerical simulations.