WiMAX Reference Network Model - WiMAX

What is the WiMAX Reference Network Model?

IEEE 802.16e-2005 standard offers air interface for WiMAX, but it will not define the full end-to-end WiMAX network. WiMAX Forum's Network Working Group (NWG) will be liable to develop the end-to-end network requirements, architecture and protocols for WiMAX, using IEEE 802.16e-2005 as the air interface.

WiMAX NWG have developed a network reference model which serves as an architecture framework for WiMAX deployments and ensures the interoperability between various WiMAX equipment and operators.

The network reference model imagines a combined network architecture to support fixed, nomadic and mobile deployments and is based on an IP service model. Below is a basic explanation of an IP-based WiMAX network architecture. Overall network can be logically divided into three parts

  • Mobile Stations (MS) used by the end user to access the network.
  • The access service network (ASN), which comprises one or more base stations and one or more ASN gateways that form the radio access network at the edge.
  • Connectivity service network (CSN) which provides IP connectivity and all the IP core network functions.

Network reference model which was developed by WiMAX Forum NWG, defines many functional entities and interfaces between those entities. Below image shows some of the most important functional entities.

wimax_reference_network.gif

  • Base station (BS) − BS is responsible for providing air interface to MS. Additional functions which are a part of BS 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, and multicast group management.
  • Access service network gateway (ASN-GW) − ASN gateway typically acts as a layer 2 traffic aggregation point within an ASN. Additional functions which are a part of the ASN gateway which include 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, and routing to the selected CSN.
  • Connectivity service network (CSN) − CSN will provide connectivity to the Internet, ASP, other public networks, and corporate networks. CSN is owned by NSP and it includes AAA servers which supports authentication for devices, users, and specific services. CSN also offers per user policy management of QoS and security. CSN is also responsible for IP address management, support for roaming between different NSPs, location management between ASNs, and mobility and roaming between ASNs.

WiMAX architecture framework will allow flexible decomposition and/or combination of functional entities when building the physical entities. For example, ASN may be decomposed into base station transceivers (BST), base station controllers (BSC), and an ASNGW analogous to the GSM model of BTS, BSC, and Serving GPRS Support Node (SGSN).

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