A comparison of wi-fi and wimax with case studies - Florida State ...

speed fixed wireless broadband service for this band. These first-generation broadband systems
used towers which were several hundred feet tall and had LOS coverage up to 35 miles with high
power transmitters. The users had to install outdoor antennas high enough to receive a signal
and pointed toward the tower for the clear LOS path. This LOS equipment was soon considered
an impediment. And because towers were difficult to set up, the service was quite limited.
[50][91][92]
Second-generation non-line-of-sight broadband systems
The second-generation broadband systems had potential to solve the LOS problem and had
the ability to provide more capacity and higher speed. This was because they used cellular
architecture and advanced-signal processing technology. With these methods, the link and
system performance was improved under multipath conditions. These new second-generation
systems also perform well in NOLS (Non-Line of Sight) environment by using OFDM, CDMA
and multiantenna processing. Some of them can even be operated without setting an antenna
outside. [50]
Standards-based broadband wireless systems.
IEEE 802.16 standard was approved officially on December 2001 and the formal name was
wireless metropolitan area network (WMAN). This first standard only focused on the10 GHz –
66 GHz band and can only do LOS transmission. In PHY-layer, it used single-carrier modulation
and in the MAC-layer, it had time division multiplexing (TDM) structure which supported FDD
(Frequency Division Duplexing) and TDD (Time Division Duplexing). [50]
In order to maintain a competitive advantage, the IEEE 802.16 standard group developed a
series of extended standards to improve WMAN performance. The IEEE 802.16 family members
include IEEE 802.16, IEEE 802.16a, IEEE 802.16c, IEEE 802.16-2004, IEEE 802.16e-2005,
IEEE 802.16f, IEEE 802.16g and IEEE 802.16h. [60]
WiMax Forum
This is a Non-Profit Organization formed in April 2001. The initial members included Intel,
Fujistu, and Nokia among others. The major mission of this forum is to assure the unity and
compatibility of BWA products produced by any manufacturer. In the beginning, the
certification was only between IEEE 802.16 standard and ETSI HiperMAN standard (European
Telecommunications Standards Institute, High Performance Metropolitan Area Network). As the
technologies of the 802.16 become more mature, many industries started to pay attention to it.
Therefore, more companies around the world joined and established several working groups to
promote the standard. Because of this forum, WiMax (World Interoperability for Microwave
Access) became the second name of IEEE 802.16. [59]
38