Susana Sargento

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

Multimedia Services over Wireless Metropolitan Area Networks

Abstract The IEEE 802.16 family of wireless local and metropolitan area network (LAN/MAN) standards has received plenty of attention in recent years due to its potential to change the field of telecommunications operations. WiMAX, which is based on IEEE 802.16 and a network reference architecture defined by the WiMAX Forum, emerges as a potent proposal for building next-generation broadband wireless networks. This chapter is a comprehensive review of wireless MANs using WiMAX technologies, focusing in particular on multimedia service delivery over such networks. We start by summarizing recent trends in Internet traffic, which demonstrate the proliferation of multimedia services alongside the strong need for cost-efficient broadband access solutions, such as WiMAX. We then provide an overview of both fixed and mobile WiMAX, which includes a short introduction to the physical (PHY) and medium access control (MAC) layers of the IEEE 802.16 standard. We focus on the key architectural elements, including Quality of Service (QoS) support, and relate them with multimedia service delivery. To better illustrate the opportunities emerging in the broadband wireless access telecommunications segment, we also describe a set of reference WiMAX deployment scenarios. We then switch gears and present the advances in voice over Internet Protocol (VoIP) technology presenting ITU-T standard codecs such as G.711, G.723.1, and G.729.1, open-source codecs such as Speex, as well as codecs employed in popular VoIP applications. Finally, this chapter presents a thorough empirical evaluation of multimedia service delivery over WiMAX. We measure multimedia service delivery performance over standards-conforming WiMAX testbeds in Finland and Portugal, and evaluate the benefits of voice sample aggregation and robust header compression (ROHC) in practice.