Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
SOT
Synchronization
symbol
Channel reference
symbol
maximum 243 symbols
Figure 4 PPDU
Control and data
symbols
The maximum duration of a PPDU is 243 symbols (counting from the synchronization symbol to the last
symbol of the frame). A receiver shall be able to handle a maximum duration PPDU.
The gap between the last non-zero sample of the SOT and the first non-zero sample of the synchronization
symbol shall be 2.75 ± 0.25 µs.
The time between two consecutive PPDUs is fixed and known by all modems as the INTER PPDU SPACE 1
(see 3.11 and 4.6). Only when scheduling the token by means of a Distributor Frame, the time can be reduced
and is called INTER PPDU SPACE 2 (see 3.11 and 4.6).
3.3 FORWARD ERROR CORRECTION
3.3.1 Delimiters
There are several types of delimiters that will be explained in 4.4 and 5.2. Delimiters are mapped to one OFDM
symbol, so they will always have the same size.
Three main calculations will be made over a delimiter as is shown in Figure 5.
3.3.1.1 CRC-CCITT
176 bits 192 bits 288 bits Frame 288 bits
RS (12,8)
CRC-16
control
Encoder
Interleaver
Figure 5 Delimiter encoding
A CRC-CCITT is applied to the incoming 176 bits length delimiter applying the polynomial generator:
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