Medium Access Control in IEEE 802.11s Wireless Mesh Networks

Standard 802.11 of the Institute of Electrical and Electronics Engineers (IEEE) has become the dominating solution for Wireless Local Area Networks
(WLANs). Its simple and robust medium access protocol has paved the way for a mass market that is expected to ship one billion IEEE 802.11
devices in 2011. From the beginning of its standardization in 1990 until September 2011 twenty amendments have extended IEEE 802.11 for various
applications. Examples are support for Quality of Service (QoS) that enables Voice over IP (VoIP) over WLAN and Consumer Electronic (CE)
related applications, an extension for car to car communication that helps to enable new safety features, and intelligent radio resource management
that targets new spectrum. These amendments make IEEE 802.11 a truly ubiquitous solution that is used in industrial machinery, point-to-point
links, CE devices, computers, cars, mobile phones and many more products. Until the introduction of its latest amendment—IEEE 802.11s—WLANs
are typically used to extend wired networks. In this case, the WLAN forms the last hop of a wired backhaul and the latter is needed to interconnect the
central entities that bridge thewired to thewireless network. These entities, denoted as Access Point (AP), allow only for single-hop communication on
theWirelessMedium (WM). To bring wireless network access to unserved areas requires the provisioning of wired backhaul, therefore. IEEE 802.11s
fills this gap. It introduces mesh networking that brings wireless multihop communication. With IEEE 802.11s the infrastructure dependency
of WLAN is cut and self-contained Wireless Mesh Networks (WMNs) of arbitrary topology can be formed. Furthermore, these IEEE 802.11sWMNs
may serve as transparent backhaul for other, external networks. A data frame’s source and destination may be in- or outside of theWMN. Medium
Access Control (MAC) layer based routing delivers the frame over multiple hops. The current medium access protocols of IEEE 802.11 have not been
designed for this multi-hop communication, however. The thesis describes the new medium access protocol that IEEE 802.11s
introduces. The protocol is based on distributed reservations that allow for scheduled access to the WM. It is derived from an invention that is
used in standards for Wireless Personal Area Networks (WPANs). The thesis outlines the author’s inventions and the standards that apply it. The
publicly available, event-driven protocol simulatorWireless Access Radio Protocol 2 (WARP2) is used to evaluate the performance of the invention
and the new medium access protocol of IEEE 802.11s.