These coded bits are mapped to 48 subcarriers plus 4 pilot subcarriers, providing a
total of 52 subcarriers. The pilot bits are BPSK modulated.
WIRELESS TOPICS 25
The possible system data rates along with their modulation and coding parameters are given in
Table 1.9. The PPDU frame format is given in Fig. 1.33.
The bit fields have the following description:
PLCP preamble can be used for the following signal processing functions: AGC convergence,
diversity selection, time and frequency acquisition, channel estimation, and so forth.
The preamble consists of 10 repetitions of a short training sequence followed by 2 repetitions
of a long training sequence, where a short symbol consists of 12 subcarriers and a long symbol
consists of 53 subcarriers. The PLCP preamble is BPSK OFDM modulated at 6 Mbps and
of length 16 sec.
Rate 4 bits used to indicate the data rate shown in Table 1.9.
Length12 bits indicating the number of octets in the PSDU that the MAC (medium access control)
is currently requesting to transmit.
This system operates in a 5-MHz channel spacing, with a transmit frequency tolerance of less than
20 ppm.
IEEE802.11g. Thus, WLAN system provides further data rate extensions into the 2.4-GHz frequency
band.
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