Wireless Broadband Technologies: What
Is Wimax, Wimax Features
1.What is WiMAX
WiMAX is an IP based, wireless broadband access technology
that provides performance similar to 802.11/Wi-Fi networks
with the coverage and QOS (quality of service) of cellular
networks. WiMAX is also an acronym meaning "Worldwide
Interoperability for Microwave Access" (WiMAX).
WiMAX is a wireless digital communications system, also
known as IEEE 802.16 that is intended for wireless "metropolitan
area networks". WiMAX can provide broadband wireless access
(BWA) up to 30 miles (50 km) for fixed stations, and 3 -
10 miles (5 - 15 km) for mobile stations. In contrast, the
WiFi/802.11 wireless local area network standard is limited
in most cases to only 100 - 300 feet (30 - 100m).
The most recent versions of both WiMAX standards in 802.16
cover spectrum ranges from at least the 2 GHz range through
the 66 GHz range.
a. WiMAX Features
WiMAX is a wireless broadband solution that offers a
rich set of features with a lot of flexibility in terms
of deployment options and potential service offerings. Some
of the more salient features that deserve highlighting are
- Two Types of Services: WiMAX can provide two forms
of wireless service:
- Non-line-of-sight: service is a Wi-Fi sort of
service. Here a small antenna on your computer connects
to the WiMAX tower. In this mode, WiMAX uses a lower
frequency range- 2 GHz to 11 GHz (similar to Wi-Fi).
- Line-of-sight: service, where a fixed dish antenna
points straight at the WiMAX tower from a rooftop
or pole. The 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
- OFDM-based physical layer: The WiMAX physical layer
(PHY) is based on orthogonal frequency division multiplexing,
a scheme that offers good resistance to multipath, and
allows WiMAX to operate in NLOS conditions.
- Very high peak data rates: WiMAX is capable of supporting
very high peak data rates. In fact, the peak PHY data
rate can be as high as 74Mbps when operating using a
20MHz wide spectrum. More typically, using a 10MHz spectrum
operating using TDD scheme with a 3:1 downlink-to-uplink
ratio, the peak PHY data rate is about 25Mbps and 6.7Mbps
for the downlink and the uplink, respectively.
- Scalable bandwidth and data rate support: WiMAX
has a scalable physical-layer architecture that allows
for the data rate to scale easily with available channel
bandwidth. For example, a WiMAX system may use 128,
512, or 1,048-bit FFTs (fast Fourier transforms) based
on whether the channel bandwidth is 1.25MHz, 5MHz, or
10MHz, respectively. This scaling may be done dynamically
to support user roaming across different networks that
may have different bandwidth allocations.