ttp://grouper.ieee.org/groups/802/15/> [29] IEEE 802.16 Broadband Wireless Access Standards. <http://grouper.ieee.org/groups/802/16/>. [30] IEEE 802.20 Mobile Broadband Wireless Access. <http://www.ieee802.org/20/>. [31] Bridging and Virtual Bridged LANs IEEE 802.1. <http://grouper.ieee.org/groups/802/1/> [32] IEEE Standards Association. <http://standards.ieee.org/> [33] WiMAX Forum Mobile System Profile Specification Release 1.5, February 2009. <http://www. wimaxforum.org/resources/documents/technical/release>. [34] WiMAX Forum, Requirements for WiMAX Air Interface System Profile Release 2.0, March 2009. <http://www.wimaxforum.org/resources>. [35] K. Vijay Garg, E. Joseph, Wilkes, Principles and Applications of GSM, Prentice Hall, 1999. [36] 3rd Generation Partnership Project Agreement, <http://www.3gpp.org/>. [37] 3GPP TR 23.882, 3GPP System Architecture Evolution: Report on Technical Options and Conclusions, September 2008. (ftp://ftp.3gpp.org/specs/). This page intentionally left blank CHAPTER WiMAX Network Architecture INTRODUCTION The IEEE 802.16-2009 standard only defines physical and medium access control layer protocols. This approach might have worked well for technologies such as Ethernet and Wi-Fi, relying on other bodies such as the Internet Engineering Task Force (IETF)¹ to set the standards for higher layer protocols such as TCP/IP [1], SIP [2], and Ipsec [3], it cannot be generalized to cellular standards. Standard developing organizations such as 3GPP and 3GPP2 specify end-to-end wireless access systems including a wide range of interfaces and network protocols because practical systems require not only the air link interoperability but also inter-vendor and inter-network interoperability for roaming, multi-vendor access networks, and inter-operator billing. WiMAX vendors and operators have recognized this issue and have established additional industry groups to develop standard network reference models for open network interfaces. Examples of these groups include WiMAX Forum's Network Working Gr