QoS Analysis of Cognitive Radios Employing HARQ

TL;DR

This paper analyzes the performance of cognitive radio systems using HARQ protocols under QoS constraints, considering imperfect sensing and hybrid spectrum access strategies, providing analytical models and numerical validation.

Contribution

It introduces a novel analytical framework for modeling cognitive radios with HARQ under QoS, incorporating imperfect sensing and hybrid spectrum access techniques.

Findings

Derived state-transition probabilities for the system

Calculated packet-loss rates under various conditions

Validated analytical results with numerical simulations

Abstract

Recently, the demand for faster and more reliable data transmission has brought up complex communications systems. As a result, it has become more difficult to carry out closed-form solutions that can provide insight about performance levels. In this paper, different from the existing research, we study a cognitive radio system that employs hybrid-automatic-repeat-request (HARQ) protocols under quality-of-service (QoS) constraints. We assume that the secondary users access the spectrum by utilizing a strategy that is a combination of underlay and interweave access techniques. Considering that the secondary users imperfectly perform channel sensing in order to detect the active primary users and that there is a transmission deadline for each data packet at the secondary transmitter buffer, we formulate the state-transition model of the system. Then, we obtain the state-transition probabilities when HARQ-chase combining is adopted. Subsequently, we provide the packet-loss rate in the channel and achieve the effective capacity. Finally, we substantiate our analytical derivations with numerical results.