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19.2.3.9 Short PLCP SFD field (shortSFD)
The shortSFD shall be a 16-bit field and be the time reverse of the field of the SFD in the long PLCP preamble
(19.2.3.2). The field is the bit pattern 0000 0101 1100 1111. The right end bit shall be transmitted first in time. A
receiver not configured to use the short header option will not detect this SFD.
19.2.3.10 Short PLCP SIGNAL field (shortSIGNAL)
The 8-bit SIGNAL field of the short header indicates to the PHY the data rate that shall be used for transmission
(and reception) of the PSDU. A PHY operating with the ER/OFDM/short option supports mandatory rates given by
the following 8-bit words, where the lsb shall be transmitted first in time and the number represents the rate in units
of 100 kBit/s:
a) X’14’ (msb to lsb) for 2 Mbit/s;
b) X’37’ (msb to lsb) for 5.5 Mbit/s;
c) X’6E’ (msb to lsb) for 11 Mbit/s;
d) X’14’ (msb to lsb) for all ER/OFDM modes
19.2.3.11 Short PLCP SERVICE field (shortSERVICE)
The SERVICE field in the short header shall be the same as the SERVICE field described in 19.2.3.4.
19.2.3.12 Short PLCP LENGTH field (shortLENGTH)
The LENGTH field in the short header shall be the same as the LENGTH field described in 19.2.3.5
19.2.3.13 Short CCITT CRC-16 field (shortCRC)
The CRC in the short header shall be the same as the CRC field defined in 19.2.3.6. The CRC-16 is calculated over
the shortSIGNAL, shortSERVICE, and shortLENGTH fields.
19.2.3.14 Short PLCP data modulation and modulation rate change
The short PLCP preamble shall be transmitted using the 1 Mbit/s DBPSK modulation. The short PLCP header shall
be transmitted using the 2 Mbit/s modulation. The SIGNAL and SERVICE fields combined shall indicate the
modulation and data rate that shall be used to transmit the PSDU. The transmitter and receiver shall initiate the
PSDU modulation and rate indicated by the SIGNAL and SERVICE fields, starting immediately after the last
symbol of the PLCP Header. The PSDU transmission rate shall be set by the DATARATE parameter in the
TXVECTOR, issued with the PHY-TXSTART.request primitive described in 19.4.4.2.
19.2.4 PLCP/Extended Rate PHY data scrambler and descrambler
The polynomial G(z) = z
-7
+ z
-4
+ 1 shall be used to scramble all bits transmitted. The feedthrough configuration of
the scrambler and descrambler is self-synchronizing, which requires no prior knowledge of the transmitter
initialization of the scrambler for receive processing. Figure *** and Figure *** show typical implementations of
the data scrambler and descrambler, but other implementations are possible.
The scrambler shall be initialized as specified in 19.2.3.8 for the short PLCP and 19.2.3.1 for the long PLCP. For a
Long Preamble, this shall result in the scrambler registers Z
1
through Z
7
in Figure *** having the data pattern
[1101100] (i.e., Z
1
= 1... Z
7
= 0) when the scrambler is first started. The scrambler shall be initialized with the
reverse pattern [0011011] when transmitting the optional Short Preamble.