Spectrum utilization efficiency in CRNs with hybrid spectrum access and channel reservation: A comprehensive analysis under prioritized traffic

The enhancement of spectrum utilization efficiency (SUE) is a critical objective in fifth generation networks-enabled Internet of Things (5G-IoT) for providing communication opportunities to plethora of 5G-IoT devices within the already scarce spectrum. Cognitive radio networks (CRNs) with interweave and underlay modes are foreseen to achieve this objective. The interweave mode is adequate for legacy CRNs, while the underlay mode is fitting for resource-constrained CRNs. As 5G-IoT is rapidly evolving into heterogeneous networks, CRNs enabled by hybrid underlay-interweave mode (H-mode) emerge to be the best option for SUE enhancement in 5G-IoT. In this paper, we comprehensively analyze the performance of H-mode enabled CRNs containing heterogeneous users by proposing two H-mode schemes, namely, primary user full priority (FP) and primary user partial priority (PP). The schemes consider secondary users (SUs) with high and low priorities. In FP, primary users (PUs) have absolute priority in channel access while in PP, SUs with certain attributes are immune from interruptions. Additionally, to accommodate interrupted users, a simple yet efficient channel reservation algorithm is proposed, which divides the given channels into reserved and unreserved bands. Using Markov chain modeling, expressions are derived for core SUE related performance metrics including service completion rate (SCR), blocking probability (BP), network serveability (NS), successful service completion probability (SSCP), handoff probability, and throughput, independently for PUs and all types of SUs. Performance of the proposed schemes is analyzed under varying channel failure rates and network traffic loads. Efficacy of the proposed schemes is shown through analytical and simulation results against state-of-the-art. Improvements of up to 67% in BP and 83% in cost efficiency are recorded as compared to the state-of-the-art. Likewise, up to 10% and 84% difference in PUs’ and SUs’ SSCP, respectively, and up to 17% and 93% difference in PUs’ and SUs’ SCR, respectively, are noted. Similarly, up to 85% performance difference in NS is recorded. Moreover, up to 35% improvement in throughput in H-mode is witnessed. Lastly, handoff probability is found to be increased by 5%.