Performance analysis of priority queueing systems in discrete time

The integration of different types of traffic in packet-based networks spawns the need for traffic differentiation. In this tutorial paper, we present some analytical techniques to tackle discrete-time queueing systems with priority scheduling. We investigate both preemptive (resume and repeat) and non-preemptive priority scheduling disciplines. Two classes of traffic are considered, high-priority and low-priority traffic, which both generate variable-length packets. A probability generating functions approach leads to performance measures such as moments of system contents and packet delays of both classes

Enhancement of the TXOP Sharing designed for DL-MU-MIMO IEEE 802.11ac WLANs

International audienc

Performance Analysis of the TXOP Sharing Mechanism in the VHT IEEE 802.11ac WLANs

International audienceThe 802.11ac amendment of the IEEE 802.11 standard, known as a very high-throughput wireless local area network (WLAN), has attracted extensive attention for achieving a maximum transmission rate up to 7 Gb/s. This is mainly possible by adopting the DownLink MultiUser Multiple-Input-Multiple-Output (DL MU-MIMO) technology, which allows multiple frames to be simultaneously transmitted from the access point (AP) to different receivers via multiple spatial streams. To support the DL MU-MIMO technology at medium access control level, a technique called transmission opportunity (TXOP) sharing has been proposed to extend the mandatory TXOP of the WLAN standard. In this letter, we propose an analytical model based on Markov chains to evaluate the performance of an IEEE 802.11ac AP enabling the TXOP sharing mechanism. Based on this model, we are able to derive the achievable throughput of a given access category (AC), namely, voice (VO), video (VI), best effort (BE), and background (BK). The ultimate goal of this letter is to analyze how the TXOP sharing mechanism could improve the utilization of the scarce wireless bandwidth while achieving channel access fairness among the different ACs. Note that the obtained theoretical results are also validated by computer simulatio