Age of information-oriented comparative evaluation of channel access mechanisms in multi-rate wireless lans

Abstract

Delay-sensitive applications have recently garnered significant attention because of the increasing demand for real-time data and time-critical information. In delay-sensitive systems, the timeliness of the delivered information is crucial to guarantee a reliable operation. A performance metric called Age of Information (AoI) is introduced in the literature to measure the freshness of information. In this study, various channel access methods are comparatively evaluated for stations transmitting age-sensitive status update packets over a multi-rate IEEE 802.11 WLAN. For wireless networks carrying conventional data traffic, the legacy channel access mechanism imposed by the Distributed Coordination Function (DCF) allows sources to access the channel equally. This mechanism results in a throughput-fair bandwidth allocation which is also known as a performance anomaly in the literature. Airtime-fair channel access methods have been proposed in the literature for multirate wireless LANs to mitigate this anomaly. Recently, there has been a surge of interest in status update systems with the emergence of performance criteria called age of information. Age-based performance metrics (AoI, peak AoI) are more effective to satisfy the requirements of the carried age-sensitive traffic as opposed to using conventional performance metrics (throughput, delay, or loss). In this study, we propose a novel channel access mechanism for age-sensitive traffic which is devised to lessen the mean Peak AoI (PAoI) averaged over all the sources in the network, which is termed as the system PAoI. The proposed channel access mechanism effectively reduces the system PAoI compared to LCA and PFCA. Although system PAoI performance improvement depends on the system configuration, i.e. packet size, the multi-rate mixture of the network etc., system PAoI can be reduced up to 12.04% and 27.44% compared to the legacy channel access and airtime-fair channel access, respectively, for the considered system configurations in this study. Although the proposed channel access mechanism outperforms legacy and airtime-fair channel access mechanisms in terms of system PAoI, it may lead to a reduction in the overall throughput of the system compared to airtime-fair channel access.