Specifications

2.1 IEEE 802.16 Standard: The IEEE 802.16 standard is designed as the air interface for
wireless metropolitan area networks (MANs). A wireless MAN provides a radio connection
between an exterior mounted antenna on a building and a central base station. The MAN is used
as a replacement for a wired access network such as cable, DSL, or fiber optic cable. The ability
to connect sites with out an expensive infrastructure between them can provide economic
advantages as well as advantages in ease of deployment. Although proprietary systems have
been deployed before, a standard has never before existed that would allow for product
interoperability and consequently the price drop that is associated with widespread competition
and deployment.
The 802.16 standard does not specify a frequency that must be used, but instead breaks the
spectrum into two separate sections: 2-11GHz and 11-66GHz. This paper will only deal with the
2-11 GHz portion of the spectrum, as that is the frequency set in which most of the equipment is
available. At higher frequencies it becomes more difficult to get very long-range links, as the
path loss is frequency dependent. IEEE 802.16 can be implemented in both licensed and
unlicensed bands. The use of unlicensed spectrum is appealing since it saves the cost of getting a
license and allows for deployment in a wide geographic range with out the need for licensing.
The IEEE 802.16 medium access control (MAC) was designed with very high bit rates in mind,
in both the uplink and down link directions. Access and bandwidth allocation must be able to
handle multiple different data streams as well as different quality of service (QoS) requirements.
Quality of service requirements may be such that one link has priority over another link when
there is bandwidth contention. Quality of service also dictates what the maximum throughput of
a link is limited to. This is useful for fixed broadband wireless providers to have a flexible way
to serve different types of customers. The 802.16 MAC provides a wide range of service types
analogous to ATM systems.
Each user is given a burst profile that specifies the modulation and coding format to be used for
that user. By adjusting the burst profile the MAC can make use of high data rate and highly
spectrally efficient modulation schemes and still have the ability to scale back to a lower bit rate
and more robust modulation format so that the link can sustain very high availability, with out
5