Spectrum and Services
The electromagnetic radio spectrum is governed in most countries around the world in a manner known as radio frequency allocation.
Governments from all over the world formed an association of committees which have decided on a standardization of the RF bands and their usage, as a result of the propagation of radio wave signals which must be globally respected.
These committees have designated 3 classes of frequency bands throughout the radio spectrum which include; government restricted frequencies, unlicensed amateur bands, and licensed bands, which is where the WiMAX spectrum operates.
The WiMAX spectrum currently holds territory in several licensed bands operating within the 2GHz - 6GHz range, and we're going to be taking a closer look at these RF allocations and describe how signals are affected by frequency and interferences.
Wireless Services
What this points out is that WiMAX actually can provide two forms of wireless service:
- There is the non-line-of-sight, WiFi sort of service, where a small antenna on subscriber computer connects to the tower. In this m ode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi). Lower-wavelength transmissions are not as easily disrupted by physical obstructions -- they are better able to diffract, or bend, around obstacles.
- There is line-of-sight service, where a fixe d dish antenna points straight at the WiMAX tower from a rooftop or pole. Th e line-of-sight connection is stronger and more stable, so it's able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less interference and lots more bandwidth.
WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles or 65 square km of coverage, which is similar in range to a cell-phone zone). Thr ough the stronger line-of-sight antennas, the WiMAX transmitting station would send data to WiMAX-enabled computers or routers set up within the transmitter's 30-mile radius (2,800 square miles or 9,300 square km of coverage). This is what allows WiMAX to achieve its maximum range.
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