WIMAX
IEEE 802.16 is working group number 16 of IEEE 802, specializing in point-to-multipoint broadband wireless access. It also is known as WiMAX, an acronym that stands for Worldwide Interoperability for Microwave Access.
WiMax can be used for wireless networking like the popular Wi-Fi. WiMax, a third generation protocol, allows higher data rates over longer distances, efficient use of bandwidth, and avoids interference almost to a minimum.
There are at least four 802.16 standards: 802.16, 802.16a, 802.16-2004 (802.16), and 802.16e.
Based on services provided by WiMAX there are three types usage Models. They are Fixed WiMAX, portable WiMAX, and Mobile WiMAX.Services Provided by WiMAX are Line-Of-Sight (LOS), Nonline-Of-Sight (NLOS).
. An important aspect of the IEEE 802.16 is that it defines a MAC layer that supports multiple physical layer (PHY) specifications. It will not entirely replace incumbent broadband technologies; it will serve as a viable complement to them.
Introduction
WiMax (Worldwide Interoperability for Microwave Access) is a wireless broadband technology, which supports point to multi-point (PMP) broadband wireless access.
WiMAX is an Institute of Electrical and Electronics Engineers standard designated 802.16-2004 (fixed wireless applications) and 802.16e-2005 (mobile wire-less).
WiMAX has the potential to replace a number of existing telecommunications infrastructures.
This extension provides for non-line of sight access in low frequency bands like 2 - 11 GHz. These bands are sometimes unlicensed. This also boosts the maximum distance from 31 to 50 miles and supports PMP (point to multipoint) and mesh technologies.
WiMax can be used for wireless networking like the popular Wi-Fi. WiMax, a third generation protocol, allows higher data rates over longer distances, efficient use of bandwidth, and avoids interference almost to a minimum
Usage Models of WiMAX
Based on the two services from a base station to a subscriber station, also known as customer premise equipment (CPE) Provided by WiMAX.
• Fixed WIMAX
• Portable WiMAX
• Mobile WiMAX
Fixed WiMAX:
Some goals for WiMAX include a radius of service coverage of 6 miles from a WiMAX base station for point-to-multipoint, non-line-of-sight service. This service should deliver approximately 40 megabits per second (Mbps) for fixed and portable access applications.
Mobile WiMAX:
Mobile WiMAX or portable WiMAX takes the fixed wireless application a step further and enables cell phone-like applications on a much larger scale. For example,
mobile WiMAX enables streaming video to be broadcast from a speeding police or other emergency vehicle at over 70 MPH.
Services provided by WiMAX
• Line-of-sight service
o Line-of-sight between transmitter & receiver
o 11 GHz to 66 GHz frequency range
o At Higher frequencies, there is less interference and lots more bandwidth
• Non-line-of-sight
o Line-of-sight is not required in between a small antenna on CPE and receiver.
o 2 GHz to 11 GHz frequency range.
o Longer-wavelength transmissions are not as easily disrupted by physical obstructions – they are better able to diffract, or bend, around obstacles.
WiMAX Standards
There are Four 802.16 standards:
• 802.16
• 802.16a/REVd/2004
• 802.16e
WiMAX Forum
The WiMAX Forum is a non-proft trade organization formed to promote the IEEE 802.16a wireless MAN standard, and to certify 802.16a equipment as interoperable. Like "Wi-Fi", the WiMAX Forum seeks tomake "WiMAX" a popular brand name for guaranteed interoperable wireless networking.But, while Wi-Fi focuses on wireless LAN, WiMAX will focus on using the 802.16a standard to provide wireless broadband access to businesses and consumers
The Problems WiMAX Solves
• Cellular Backhaul Problem : transport voice and data traffic from outlying cell sites to the operator's core network
• How to keep wireless notebooks and other mobile devices connected between 802.11 hotspots.
• Hotspot Backhaul Problem: Linking Wi-Fi hot spots to the Internet.
• Last Mile Problem: DSL can only reach about 18,000 feet (3 miles) from the central office switch—many urban, suburban and rural locations may not be served.
Advantages
• A single WiMAX main station can serve hundreds of users.
• Endpoints install within days instead of the weeks required for wired connections.
• Data rates as high as 280Mbps and distances of 30 miles are possible.
• Users can operate mobile within 3-5 miles of a base station at data rates up to 75Mbps.
• No FCC radio licensing is required.
Disadvantages
• Line-of-sight (LOS) is required for long distance (5-30 mile) connections
• Heavy rains can disrupt the service.
• Other wireless electronics in the vicinity can interfere with the WiMAX connection and
cause a reduction in data throughput or even a total disconnect.
