An IEEE 802.21-based Approach to Integrate Unidirectional Wireless Technologies into QoS-constrained Broadband Wireless Mesh Access Networks Mathias Kretschmer Fraunhofer FOKUS Sankt Augustin, Germany Gheorghita Ghinea Brunel University London, United Kingdom Abstract Wireless Mesh Networks (WMNs) research has ma- tured in recent years and implementations are being tested around the world. In a WMN, participating nodes are auto- matically configured allowing them to communicate among their peers via multiple hops when no direct physical con- nectivity exists. This allows community networks such as Freifunk[5] to provide affordable Internet access to their communities by sharing a few gateway nodes. Increas- ing demand for multi-media content poses a challenge for the typical WMN routing protocols such as Optimised Link State Routing (OLSR) which lack Quality of Service (QoS) support. Although, numerous solutions have been proposed to introduce QoS awareness, those WMNs fail to meet com- mercial operator requirements in term of reliability and QoS guarantees. In this paper we propose a novel IEEE 802.21-based approach seamlessly integrating broadcast technologies such as Digital Video Broadcast (DVB) into a heterogeneous multi-radio WMN architecture in order to provide support for high-bandwidth multi-media services. Keywords Heterogeneous technologies, QoS, IEEE 802.21, Wireless Mesh Network, MPLS, undirectional links 1 Introduction The visibility of successful WMN deployments has raised interest regarding a commercial exploitation of this technology. Compared to traditional operator access net- works, WMNs potentially offer easier deployment and flex- ible self-configuration at lower costs. For a WMN-type ar- chitecture to be considered as an alternative for an opera- tor access network, it must meet similar requirements such as guaranteed QoS and high availability. QoS support for WMNs has received a lot of attention from the research community [10][1][19], but has yet to show its applicability in real world deployments. Compared to the Freifunk-approach which relies on cheap off-the-shelf hardware, a Carrier-grade Wireless Mesh Access Network (CG-WMAN) may assume more re- liable and higher performing multi-radio hardware yielding more stable and potentially orthogonal links. Thus, CG- WMANs can be compared to a typical operator access net- work with two major limiting factors: the severe capacity constraints due to scarce wireless spectrum resources and temporarily varying link conditions. A modern operator access network needs to support triple-play services (web, video, voice) which emphases the need to support QoS guarantees and efficient resource utilization in a capacity- constrained network. Wireless cell resource utilization can be optimized by using the most suitable technology for a given payload. For example, the delivery of live multime- dia content is facilitated by only one transmitter, hence the overhead of Media Access Control (MAC) protocols can be avoided. Unidirectional technologies such as Digital Video Broadcast - Terrestrial (DVB-T) offer a very efficient dis- tribution medium for 1-to-N traffic and usually span across multiple mesh hops. Typically, WMNs rely on the bi-directionality of links and can therefore not utilize Unidirectional Links (UDLs). For example, Ad hoc On-Demand Distance Vector Routing Protocol (AODV)[15] black-lists UDLs since they break the distance vector algorithm. What’s more, most Mobile Ad- hoc Network (MANET) and WMN protocols can not dif- ferentiate between a faulty 802.11 link and an inherently unidirectional link provided by a unidirectional technology. In this paper we propose an Institute of Electrical and Elec- tronics Engineers (IEEE) 802.21-based approach to seam- lessly integrate UDLs into a heterogeneous CG-WMANs so that higher layer services can transparently utilize them when beneficial for a given payload or receiver distribution. This paper is structured as follows. In the next section we discuss work related to our CG-WMAN architecture fo- cusing on the support for UDLs. In the following section we compare two approaches to seamlessly integrate UDLs into the CG-WMAN and identify which protocols or com- International Journal for Infonomics (IJI), Volume 3, Issue 2, June 2010 Copyright © 2010, Infonomics Society 259