Abstract
The enormous developments in the field of wireless communication technologies have made the unlicensed spectrum bands crowded, resulting uncontrolled interference to the traditional wireless network applications. On the other hand, licensed spectrum bands are almost completely allocated to the licensed users also known as Primary users (PUs). This dilemma became a blackhole for the upcoming innovative wireless network applications. To mitigate this problem, the cognitive radio (CR) concept emerges as a promising solution for reducing the spectrum scarcity issue. The CR network is a low cost solution for efficient utilization of the spectrum by allowing secondary users (SUs) to exploit the unoccupied licensed spectrum. In this paper, we model the PU’s utilization activity by a two-state Discrete-Time-Markov Chain (DTMC) (i.e., Free and busy states), for identifying the temporarily unoccupied spectrum bands,. Furthermore, we propose a Cognitive Radio Sense-and-Wait assisted HARQ scheme, which enables the Cluster Head (CH) to perform sensing operation for the sake of determining the PU’s activity. Once the channel is found in free state, the CH advertise control signals to the member nodes for data transmission relying on Stop-and-Wait Hybrid- Automatic Repeat-Request (SW-HARQ). By contrast, when the channel is occupied by the PU, the CH waits and start sensing again. Additionally, the proposed CRSW assisted HARQ scheme is analytical modeled, based on which the closed-form expressions are derived both for average block delay and throughput. Finally, the correctness of the closed-form expressions are confirmed by the simulation results. It is also clear from the performance results that the level of PU utilization and the reliability of the PU channel have great influence on the delay and throughput of CRSW assisted HARQ model.
Highlights
The 21st century has witnessed exponential growth in innovative wireless applications
This technique leads to the emergence of cognitive radio (CR) concept, which is widely accepted for solving spectrum scarcity problems
In our previous studies [25,26,27,28,29], we have modelled the activities of Primary users (PUs) over the channel using discrete-time-Markov chain (DTMC), in which each state represents the status of a channel
Summary
The 21st century has witnessed exponential growth in innovative wireless applications. The studies of [2,3,4,5] have demonstrated that 15-85% of the licensed spectrum are underutilized due to the current static spectrum allocation policy, resulting in spectrum scarcity To overcome this dilemma, the concept of dynamic spectrum allocation (DSA) has been proposed which allows the unlicensed users to find the free spectrum, access it and use for data transmission without influencing the legal rights of PUs [2, 8,9,10]. The concept of dynamic spectrum allocation (DSA) has been proposed which allows the unlicensed users to find the free spectrum, access it and use for data transmission without influencing the legal rights of PUs [2, 8,9,10] This technique leads to the emergence of cognitive radio (CR) concept, which is widely accepted for solving spectrum scarcity problems. We consider step-by-step description of the system model and assumptions
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