In urban environments
of developing nations, even though sufficient economic conditions exist to
demand broadband services, the cost of building wired infrastructure is prohibitive.
In urban areas of the world where wired infrastructure can provide broadband services,
the choice of service providers is limited to one or two at the most. Such infrastructures
are also limited in their ability to provide the type of services that are
demanded by sophisticated urban users.
The wired infrastructures have another fundamental limitation: they cannot provide
nomadic or mobile broadband services. As small devices like cameras, PDAs, and laptops
become ubiquitous, the need to provide mobile or seamless nomadic services becomes
more important. Although such mobile broadband services are already provided
by some wireless operators, the bandwidth provided is fairly limited.
WiMAX based on OFDM-PHY and OFDMA-PHY are well positioned to serve the
needs of urban stationary as well as mobile users. In a dense urban environment,
such as the one shown in Figure 15.4, where LOS operation is impractical, the NLOS
Figure 15.4 Urban broadband services with WiMAX
Wired backhaul
WiMAX BS
(OFDM)
Base station coverage area
MDU tenants
with WiMAX SS
Homes with
WiMAX SS
Delivery van
nomadic user of
WiMAX
WiMAX 491
capability of OFDM is highly desirable.
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