TDMA on commercial of-the-shelf hardware: Fact and fiction revealed

The proliferation of multimedia applications making use of 802.11n networks, and therefore requiring the accompanying QoS, has made it imperative to improve the QoS guarantees. A well-known method is to employ a TDMA access scheme instead of the standard CSMA access scheme on commodity hardware. A considerable number of related works have focused on this issue; however, many assume the manipulation of commodity hardware to be limited to QoS parameters and none of them did a thorough analysis of one of the most crucial elements to make such a system work, that is, the timer source. The goal of this article is twofold; first we discuss a detailed performance analysis of possible timer sources in different environments and stressed by several methods. Second, we discuss the issues that developers face when using commodity hardware in a TDMA access scheme. As a result we present a successful slotted transmission scheme on commodity hardware where less than 0.1% of the received packets exhibit a jitter larger than 10 μs, while transmitting a packet every 256 μs.