Blocking of new arriving services and dropping of ongoing services are inherent problems in Cognitive Radio Networks (CRNs), which need to be addressed to enhance spectrum efficiency. In particular, Secondary Users (SUs) undergo service degradation in the face of Primary Users (PUs)’ arrivals. In this paper, we present a scheme called Efficient Spectrum Utilization (ESU) that reduces the dropping and blocking probabilities of existing and new services, respectively, to make efficient use of the available spectrum. The scheme divides the available spectrum into reserved and non-reserved bands. The reserved band is dynamically allocated a number of channels from the non-reserved band in order to accommodate those services which face interruptions while operating in the non-reserved band. The scheme renders dynamic access to the available spectrum and facilitates priority-based channel allocation and termination. SUs are divided into low and high priority levels depending on their Quality of Service (QoS) requirements. SUs with low priority level are granted direct access to both the bands to enhance channel utilization. SUs operating in the reserved band with high priority levels are granted uninterruptible status to ensure a certain level of service provisioning to SUs. The proposed ESU scheme is modeled using Continuous Time Markov Chain (CTMC) and mathematical expressions are derived for several QoS parameters. Performance of the proposed scheme is evaluated under various network conditions. Results demonstrate that ESU reasonably improves spectrum efficiency under channel failure in CRNs.

阻塞新到达的服务和丢弃正在进行的服务是认知无线电网络（CRN）固有的问题，需要解决这些问题以提高频谱效率。特别是，面对主要用户（PU）的到达，次要用户（SU）的服务质量下降。在本文中，我们提出了一种称为有效频谱利用（ESU）的方案，该方案分别降低了现有服务和新服务的掉落和阻塞概率，以有效利用可用频谱。该方案将可用频谱分为保留和非保留频段。为了适应那些在非预留频带中工作时面临中断的业务，预留频带被动态分配了来自非预留频带的多个信道。该方案提供了对可用频谱的动态访问，并促进了基于优先级的信道分配和终止。SU根据服务质量（QoS）要求分为高优先级和低优先级。低优先级的SU可以直接访问两个频段，以提高信道利用率。在具有高优先级的保留频段中运行的SU被授予不间断状态，以确保向SU提供一定级别的服务。使用连续时间马尔可夫链（CTMC）对提出的ESU方案进行建模，并为几个QoS参数导出数学表达式。在各种网络条件下评估该方案的性能。结果表明，在CRN的信道故障下，ESU可以合理地提高频谱效率。