Worldwide Interoperability for Microwave Access (WiMAX)

WiMAX, the Worldwide Interoperability for Microwave Access, is a standard based technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is based on the IEEE 802.16 standard, which is also called WirelessMAN. The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to promote conformance and interoperability of the standard. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL". The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Standard 802.16e approved in December 2005. It is a supplement to the IEEE Std 802.16-2004.

Spectrum
There is no uniform global licensed spectrum for WiMAX, although the WiMAX Forum has published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and 3.5 GHz.

Speed
WiMAX can operate at the maximum range of 50 km increases bit error rate and thus results in a much lower bitrate and Speed can be up to 70 megabits per second but both not simultaneously. Its tradeoff in between range & bit rate. In practice, in a line-of-sight environment with a portable Mobile WiMAX device, speeds of 10 Mbit/s at 10 km could be delivered. However, in urban environments they may not have line-of-sight and therefore users may only receive 10 Mbit/s over 2 km. Users can expect to have broadband access speeds ranging from 1-5 Mbps depending on the service provider offering.

WiMAX Architecture

The WiMAX architecture consists of 3 major components Mobile station i.e MSS, Access Service Network i.e ASN and Connectivity Service Network i.e CSN.

ASN includes Base station, and  the ASN Gateway where as CSN consists of  Home Agent and AAA. NAP stands for Network Access Provider and NSP stands for Network Service Provider which are self explanatory.

Several ASNs might be connected to a single CSN and  vice-versa. For ASN-CSN connections , ASN and CSN may  not be  owned by same operator.

WiMAX Node Functions
Wi-MAX Base Station incorporates full instance of WiMAX MAC and PHY in compliance with IEEE802.16 suite. A BS  instance represents one sector with one frequency assignment. A single BS can be connected to more than one ASN-GW for load balancing /Redundancy options.

Access Service Network provides complete set of network functions. ASN Provides Radio Access to WiMAX subscriber and may be realized in a single physical device or may be distributed over multiple physical devices.

ASN Gateway provide a number of functions including Service Flow Authorization, Authentication and key distribution, Session/Context maintenance, Handover co-ordination & Mobility management, Paging control and Accounting client.

CSN provides a set of network functions that provide IP connectivity services to Wi-MAX subscriber. CSN may be realized in a single physical device or may be distributed over multiple physical devices. CSN may comprise of routers, AAA servers, user database, inter working gateway devices.

NAP provides WiMAX radio access to one or more WiMAX NSPs and consists of one or more ASNs

NSPs provides WiMAX services to the WiMAX subscribers. NSP can be either a Home Network Service Provider (H-NSP)  or Visited Network Service Provider(V-NSP) for a subscriber.

H-NSP is an operator/business entity that has SLA with Wi-MAX subscriber. It authorizes subscriber sessions and services the subscriber’s account (charging  and billing)

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