Not only can a system do this on a per-endstation basis but also
on a per-service basis. For example, a BS can use higher throughput coding and
modulation to communicate with an SS located at 1 km but use higher robustness
(but lower throughput) modulation to communicate with an SS located at 10 km.
Alternately, even for an SS located at 1 km, it may use higher robustness modulation
for services that require more protection than throughput, like MAC management
traffic.
?– Flexible use of the RF medium The MAC protocol of WiMAX is independent of
the PHY protocol. The higher layer MAC protocol does not make much assumption
about the nature of the PHY protocols. This allows for development of newer PHY
protocol to fit new applications as well as to take advantage of newer technologies.
We have already seen the benefit of this with the development of OFDM and
OFDMA standards. In addition, the MAC also allows support for TDD, FDD, and
half-duplex operation. This facilitates flexible use of the PHY standard without
any restriction from the higher layer protocol. The outcome of this flexibility is
wider adaptation of the technology for larger sets of applications.
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