1 Supported Cryptographic Suites
WiMAX 479
higher frequency range have much poorer penetrating properties than lower frequency
RF signals. Finally, Doppler shift encountered due to mobility complicates the design
of higher frequency systems. In order to address the NLOS applications, and subsequently
to support mobility, PHY protocols operating below 11 GHz using multi-carrier
modulation were subsequently developed.
Single-Carrier Modulation The single-carrier PHY standard (SC-PHY) was the first
PHY standard developed by IEEE 802.16, which referred to it as WirelessMAN-SC.
It was designed to operate at frequencies between 10 GHz and 66 GHz. (Another
single-carrier PHY standard, referred to as WirelessMAC-SCa, was subsequently
developed to operate below 11 GHz but does not appear to have found much support
in the industry.)
SC-PHY supports both Time-Division Duplexing (TDD) and Frequency-Division
Duplexing (FDD) operations in order to accommodate a diverse set of worldwide spectrum
regulation. In FDD, DL and UL communications use two different non-overlapping
bands of spectrum, enabling them to take place simultaneously. In TDD, both DL and
UL communications use the same band of spectrum and the transmission time is divided
into timeframes, one for uplink and another for downlink.
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