In multi-channel multi-user cognitive radio systems, there are two main challenges to support traffic with delaysensitive QoS requirements, namely, the coordination among the secondary users (SUs) and the long channel occupancy time of the primary users (PUs). In this paper, we propose a hopping-based channel access scheme for SUs to improve their performance. Each SU chooses one of the channels allocated to PUs in a hopping-based manner in each time slot to opportunistically sense and transmit. This scheme not only avoids collisions among SUs, but also reduces the effect of the long channel occupancy time of PUs on the QoS performance of the SUs' delay-sensitive applications. We analyze the effective capacity of SU's service process with our proposed scheme. Numerical results show that our proposed scheme can achieve a higher effective capacity compared to random or fixed channel allocation.
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