802.11 Protocol Architecture
FIGURE 2.15
Protection Mechanisms
For example, when the access point allows a NonERP station to
associate, it immediately tells all ERP stations in the BSS to use
“protection.” ERP stations must then use DSSS-modulated RTS/CTS
and/or CTS-to-Self protection mechanisms. ERP stations must
transmit the protection mechanism frames using a modulation
understandable by all stations in the BSS, typically either BPSK or
QPSK. The duration field value in the MAC frame header must be set
to an appropriate value to reserve the medium for a period of time long
enough for the entire transmission (when fragmentation is not in use). ¹
1
IEEE 802.11g - 2003 – Section 7.3.2.13
