Wireless Broadband Technologies: Wimax Architecture/Network Model
The WiMAX framework is based on several core principles:
- Support for different RAN topologies
- Well-defined interfaces to enable 802.16 RAN architecture independence while enabling seamless integration and interworking with Wi-Fi, 3GPP3 and 3GPP2 networks.
- Leverage and open, IETF-defined IP technologies to build scalable all-IP 802.16 access networks using common off the shelf (COTS) equipment.
- Support for Ipv4 and Ipv6 clients and application servers, recommending use of Ipv6 in the infrastructure.
- Functional extensibility to support future migration to full mobility and delivery of rich broadband multimedia.
WiMAX has defined two MAC system profiles the basic ATM and the basic IP. They have also defined two primary PHY system profiles, the 25 MHz-wide channel for use in (US deployments) the 10.66 GHz range, and the 28 MHz wide channel for use in (European deployments) the 10.66 GHz range.
The WiMAX technical working group is defining MAC and PHY system profiles for IEEE 802.16a and HiperMan standards. The MAC profile includes an IP-based version for both wireless MAN (licensed) and wireless HUMAN (licence-exempt).
IEEE Standard 802.16 was designed to evolve as a set of air interfaces standards for WMAN based on a common MAC protocol but with physical layer specifications dependent on the spectrum of use and the associated regulations.
a. WiMAX Architecture/Network model
The IEEE 802.16e-2005 standard provides the air interface for WiMAX but does not define the full end-to-end WiMAX network. The WiMAX Forum's Network Working Group (NWG) is responsible for developing the end-to-end network requirements, architecture, and protocols for WiMAX, using IEEE 802.16e-2005 as the air interface.
The WiMAX NWG has developed a network reference model to serve as an architecture framework for WiMAX deployments and to ensure interoperability among various WiMAX equipment and operators.
The network reference model developed by the WiMAX Forum NWG defines a number of functional entities and interfaces between those entities. Fig below shows some of the more important functional entities.
- Mobile Stations (MS): Is used by the end user to access the network.
- Base station (BS): The BS is responsible for providing the air interface to the MS. Additional functions are:
- Micro mobility management functions, such as handoff triggering and tunnel establishment, radio resource management
- QoS policy enforcement
- Traffic classification
- DHCP (Dynamic Host Control Protocol) proxy
- Key management
- Session management
- Multicast group management.
- Access service network gateway (ASN-GW): The ASN gateway typically acts as a layer 2 traffic aggregation points within an ASN. Additional functions that may be part of the ASN gateway are:
- Intra-ASN location management and paging
- Radio resource management and admission control
- Caching of subscriber profiles and encryption keys
- AAA client functionality
- Establishment and management of mobility tunnel with base stations
- QoS and policy enforcement
- Foreign agent functionality for mobile IP
- Routing to the selected CSN.