Latest update on Thursday 16 October 2008 à 09:43 by Jean-François Pillou.
What is WiMAX ?
WiMAX is short for Worldwide Interoperability for Microwave Access. It is a metropolitan wireless standard created by the companies Intel and Alvarion in 2002 and ratified by the IEEE (Institute of Electrical and Electronics Engineers) under the name IEEE-802.16. More precisely, WiMAX is the commercial designation that the WiMAX Forum gives to devices which conform to the IEEE 802.16 standard, in order to ensure a high level of interoperability among them. Devices certified by the WiMAX Forum can carry the following logo:
Goals of WiMAX
The goal of WiMAX is to provide high-speed Internet access in a coverage range several kilometres in radius. In theory, WiMAX provides for speeds around 70 Mbps with a range of 50 kilometres. The WiMAX standard has the advantage of allowing wireless connections between a base transceiver station (BTS) and thousands of subscribers without requiring that they be in a direct line of sight (LOS) with that station. This technology is called NLOS for non-line-of-sight. In reality, WiMAX can only bypass small obstructions like trees or a house and cannot cross hills or large buildings. When obstructions are present, actual throughput might be under 20 Mbps.
Operating principle of WiMAX
At the heart of WiMAX technology is the base transceiver station, a central antenna which communicates with subscribers' antennas. The term point-multipoint link is used for WiMAX's method of communication.
Fixed WiMAX and WiMAX portable
The revisions of the IEEE 802.16 standard fall into two categories:
Fixed WiMAX, also called IEEE 802.16-2004, provides for a fixed-line connection with an antenna mounted on a rooftop, like a TV antenna. Fixed WiMAX operates in the 2.5 GHz and 3.5 GHz frequency bands, which require a licence, as well as the licence-free 5.8 GHz band.
Mobile WiMAX, also called IEEE 802.16e, allows mobile client machines to be connected to the Internet. Mobile WiMAX opens the doors to mobile phone use over IP, and even high-speed mobile services.
Standard
Frequency
Speed
Range
Fixed WiMAX (802.16-2004)
2-11 GHz (3.5 GHz in Europe)
75 Mbps
10 km
Mobile WiMAX (802.16e)
2-6 GHz
30 Mbps
3.5 km
Applications of WiMAX
One of WiMAX's potential uses is to cover the so-called "last mile" (or "last kilometre) area, meaning providing high-speed Internet access to areas which normal wired technolgies do not cover (such as DSL, cable, or dedicated T1 lines).
Another possibility involves using WiMAX as a backhaul between two local wireless networks, such as those using the WiFi standard. WiMAX will ultimately enable two different hotspots to be linked to create a mesh network.
WiMAX and Quality of Service
The WiMAX standard natively supports Quality of Service (often called QoS for short), the ability to ensure that a service works when used. In practice, WiMAX lets bandwidth be reserved for a given purpose. Some applications cannot work properly when bottlenecks occur. This is the case for Voice Over IP (VOIP), as spoken communication is ineffective when gaps a second long are introduced.
WiMAX Standards
Standard
Frequency
Status
Range
IEEE std 802.16
Defines wireless metropolitan area networks (WMANs) on frequency bands higher than 10 GHz.
October 2002
Obsolete
IEEE std 802.16a
Defines wireless metropolitan area networks on frequency bands from 2 to 11 GHz inclusive.
October 9, 2003
Obsolete
IEEE 802.16b
Defines wireless metropolitan area networks on frequency bands from 10 to 60 GHz inclusive.
Merged with 802.16a (Obsolete)
IEEE std 802.16c
Defines options (profiles) for wireless metropolitan area networks in unlicensed frequency bands.
July 2003
IEEE 802.16d (IEEE std 802.16-2004)
Revision incorporating the 802.16, 802.16a, and 802.16c standards.
October 1st, 2004
Active
IEEE std 802.16e
Allows wireless metropolitan area networks to be used by mobile clients.
