Performance Investigation of SR-HARQ transmission scheme in realistic Cognitive Radio System
Madeeha Ishtiaq, Ateeq Ur Rehman, Fazlullah Khan, Abdus Salam, Shahzad · 2019
The cognitive radio (CR) paradigm has been accepted as an optimal solution for overcoming the spectrum shortage as well as maximizing the utilisation of the earmarked available spectrum. The CR systems have been widely explored in terms of its principles, dynamic architecture, operating principles etc, however, very little research is so far dedicated to reliable data transmission. Therefore, in this paper, the classic Selective-Repeat Hybrid Automatic-Repeat-Request (SR-HARQ) has been invoked for error-free communication in a realistic imperfect sensing environment of CR system. Specifically, the cognitive-aided SR-HARQ first senses the licensed primary user (PU) channel and transmits its data packets only when the channel is deemed to be idle from the PU. Otherwise, it will wait until the detection of the idle channel. To model the idle and busy activities of PU over the channel a two-state Markov chain (MC), while the cases of wrong sensing results have been modelled using four-state MC. Using this modelling, the performance in terms of throughput and average delay have been studied. The performance results show that the sensing results have significant effects on the throughput, average delay and end-to-end delay of system. Because, due to false-alarm, CU has to wait longer while the mis-detection case increases the collision and hence causing more retransmissions of packets.