Multimedia services over wireless metropolitan area networks

The IEEE 802.16 family of wireless local and metropolitan area network (LAN/MAN) standards has received plenty of attention in recent years due toits potential to change the field of telecommunications operations. WiMAX,which is based on IEEE 802.16 and a network reference architecture defined bythe WiMAX Forum, emerges as a potent proposal for building next-generationbroadband wireless networks. This chapter is a comprehensive review ofwireless MANs using WiMAX technologies, focusing in particular on multimedia service delivery over such netwroks. We start by summarizing recent trends in Internet traffic, which demonstrate the proliferation of multime-dia services alongside the strong need for cost-efficient broadband access solu-tions, such as WiMAX. We then provide an overview of both fixed and mobileWiMAX, which includes a short introduction to the physical (PHY) and mediumaccess control (MAC) layers of the IEEE 802.16 standard. We focus on the keyarchitectural elements, including Quality of Service (QoS) support, and relatethem with multimedia service delivery. To better illustrate the opportunitiesemerging in the broadband wireless access telecommunications segment, wealso describe a set of reference WiMAX deployment scenarios. We then switchgears and present the advances in voice over Internet Protocol (VoIP) technol-ogy 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 VoIPapplications. Finally, this chapter presents a thorough empirical evaluation ofmultimedia service delivery over WiMAX. We measure multimedia servicedelivery performance over standards-conforming WiMAX testbeds in Finlandand Portugal, and evaluate the benefits of voice sample aggregation and robustheader compression (ROHC) in practice.