king specifications for Fixed and Mobile WiMAX systems while Service Provider Working Group helps write requirements and prioritize them to help drive the work of the former group. The NWG also specifies detailed protocols and procedures beyond the air interface standards covered by IEEE. The Mobile WiMAX (802.16e) end-to-end network architecture is based on an all-IP platform, all packet technology with no legacy circuit telephony. The use of all-IP means that a common network core can be used, without the need to maintain both packet and circuit core networks, with all the overhead that goes with it. A further benefit of all-IP is that it places the network on the performance growth curve of general purpose processors and computing devices, often termed "Moore's Law." The WiMAX Forum has identified a WiMAX Network Reference Model (NRM), which is a logical representation of the network architecture. The NRM identifies functional entities and reference points over which interoperability is achieved between functional entities. The architecture has been developed to support fixed, nomadic, portable, simple and full mobility [3,4]. E2E Network Architecture and Mobility Management Base Station Wireless Internet Access Controller Switch/Aggregator IP backbone Firewall Base Station Network Management System Base Station Figure 11.2 Fixed WiMAX architecture 11.3.1 Fixed WiMAX Network Architecture Figure 11.2 illustrates a standalone WiMAX system which is well suited for DSL-replacement strategies and works as an ISP (Internet Service Provider). The depicted picture is based on IEEE 802.16e standard by removing only components that are responsible for mobility. The predecessor IEEE 802. 16d (Fixed WiMAX) has been abandoned by all the major operators and vendors in favor of 802.16e which is more robust and feature rich. Although 802.10 is designed to support mobility it can also be used in fixed and nomadic environments. The Fixed WiMAX network in addition to the base stations also includes a Wireless Access Controllers 