Quality of Service Differentiation in WiMAX Networks 753 Quality of Service Differentiation in WiMAX Networks

Broadband Wireless Access (BWA) based on the IEEE 802.16 standards [IEEE 802.16, 2004] [IEEE 802.16, 2005], also known as Worldwide Interoperability for Microwave Access (WiMAX), is gaining momentum as more and more field trials are transformed in commercial roll-outs. Very much likely, this is certainly a merit of the combined effort of the IEEE 802.16 standardization community, the WiMAX Forum [WiMAX Forum a, 2008] [WiMAX Forum b, 2008] and the research community. As of today, standards have matured, the WiMAX Forum has setup its certification program in order to foster interoperability, and the research community went through technological details up to an extent, such that many operators consider the risks associated with commercial deployment predictable. Yet, WiMAX is still not deemed as globally established. This technology is very new and a competing system, namely Long-Term Evolution (LTE) [3GPP, 2009], is progressing in a similar pace. Which technology will finally make it through in the market, or will we have even several co-existing ones, is, among others, influenced by the research community. The better a technology is understood, the more likely it will be adopted by manufacturers, vendors and operators. Key to scientific consideration is the availability of reliable simulation tools. This applies equally to WiMAX and any other technology and is embodied by an emerging business of commercial simulators like OPNET [OPNET] and Qualcomm [Qualcomm]. Unfortunately, these simulators are fairly expensive and/or their use is strictly licensed. As monetary considerations and openness frequently prevail, in particular in academia, NS-2 [NS-2], as open-source alternative, still retains its position. Naturally, open-source software rarely approaches commercial standards, especially in terms of completeness and documentation. This is, for example, the case for the public available WiMAX module for NS-2. This module supports several WiMAX features but lacks a very essential one, Quality of Service (QoS) support. The lack of this feature 34