WiMAX stands for Worldwide Interoperability for Microwave Access. It is an open, worldwide broadband telecommunications standard for both fixed and mobile deployments. Its purpose is to ensure the delivery of wireless data at multi-megabit rates over long distances in multiple ways.
WiMAX allows connecting to internet without using physical elements such as router, hub, or switch. It operates at higher speeds, over greater distances, and for a greater number of people compared to the services of WiFi.
The WiMAX Forum, formed in 2001 to promote WiMAX defines WiMAX as “a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL.”
A WiMAX system has two units. They are WiMAX Transmitter Tower and WiMAX Receiver. A Base Station with WiMAX transmitter responsible for communicating on a point to multi-point basis with subscriber stations is mounted on a building. Its tower can cover up to 3,000 Sq. miles and connect to Internet. A second Tower or Backhaul can also be connected using a line of sight, microwave link. The Receiver and antenna can be built into Laptop for wireless access.
For a non Line of Sight transmission, WiMAX uses a low frequency range from 2 GHz to 11 GHz with an ability to bend around obstacles. For a Line of Sight transmission, it uses a high frequency range up to 66 GHz With stronger and more stable signals.
WiMAX is based on interoperable implementations of IEEE 802.16 wireless networks standard. Latest Mobile WiMAX is based on IEEE 802.16e-2005 which is an amendment of IEEE 802.16-2004. IEEE Std 802.16-2004 which replaced IEEE Standards 802.16-2001, 802.16-2002, and 802.16-2003 addressed only fixed systems. But each of these updates added various functionalities and expanded the reach of the standard.
- IEEE 802.16 (First Version) addressed the line of sight (LOS) access in spectrum ranges between 10 GHz and 66 GHz.
- IEEE 802.16a specification covered bands in the ranges between 2GHz and 10 GHz.
- IEEE 802.16c added support for spectrum ranges both licensed and unlicensed from 2 GHz to 10 GHz. Improved Quality of Service (QOS) and support for HiperMAN European standard are the highlights of this specification.
- IEEE 802.16d supported OFDM version with 256 sub-carriers.
- IEEE 802.16e-2005 used Scalable Orthogonal Frequency-Division Multiple Access (SOFDMA). It also used Multiple Input Multiple Output Communications (MIMO) to support multiple antennas.
- Provides connections not only to WiFi hotspots but also to other parts of Internet.
- Avoids the hassle of using expensive cables and saves cost
- Offers high band width that supports hundreds of businesses at once with T1 type connectivity
- Provides two forms of wireless alternative to cable and DSL for last mile (last km) broadband access.
- Offers long communication range of up to 30 miles.
- Uses licensed or unlicensed spectrum.
- Offers consistent throughput both in upstream and downstream.
- Provides high speed streaming video, wireless, high speed gaming, and personal video conferencing services.
Wimax and IPv6
IPv6 has been built with a focus on the needs of the next generation internet. With mobile support features and security, IPv6 has better compatibility with WiMAX.
WiMAX architecture designed by WiMAX Forum shows the WiMAX network connectivity with other networks.
The Access Service Network (ASN) consists of Base Station (BS) and IPv6 Access Router (AR). It has a complete set of functions such as AAA, Mobile IP Foreign agent, Paging controller, and Location Register to provide radio access to a WiMAX Subscriber. The Connectivity Service Network (CSN) offers connectivity to the internet. The Mobile Station (MS) at the IPv6 layer is associated with AR in ASN. Both are connected in two ways.
1. Transport connection that is identified by a Connection Identifier (CID) over air interface
2. GRE tunnel between BS and AR to transport IPv6 packets
Protocol stack in WiMAX for IPv6 is given below.
When MS performs initial network entry, the ASN Gateway/AR triggers the establishment of the Initial Service Flow (ISF) for IPv6 towards MS through GRE tunnel. BS requests MS to establish a transport connection over the air interface. This results in having a transport connection over the air interface for carrying IPv6 packets and a GRE tunnel between BS and AR for relaying IPv6 packets.
As IPv6 is compatible with WiMAX, many organizations have initiated work to build a system that focuses on linking the Layer 3 technology of IPv6 with the Layer 2 technology of IEEE 802.16.
- The IETF has initiated Working Group on “IPv6 over IEEE 802.16(e) Networks” to maintain IP connectivity over Mobile WiMAX networks.
- The WiMAX Forum has formed an IPv6 Sub team to work on mobile support such as Cellular Mobile IPv6 (CMIPv6).
- The Ipv6 Forum together with the WiMAX Forum published a paper Vision 2010 focusing on IPv6 over WiMAX.