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

4-June-07 P1901_PRO_016_r0
When the data payload length is not an integer number of Reed-Solomon codewords, the last Reed Solomon
codeword will have a special coding given by the formula:
[ ( 4*
APL)
mod( k + 2*
t)
] − 2t
klastcw =
i
Equation 11
Where APL is the data payload length in number of 32-bit words including RS coding parity bits.
For the last codeword, no minimum value in k is applied.
The incoming data payload shall be grouped in L groups of ki bytes, where ki has been taken from the “FEC
payload” field in burst header, and a last group of klastcw bytes, calculated from Equation 11, as can be seen in
the following figure:
L Blocks
I L*ki+klastcw-1 I L*ki+klastcw-2 I (L-1)*ki+klastcw RS1 2*t-1 RS1 0
I (L-1)*ki+klastcw-1 I (L-1)*ki+klastcw-2 I (L-2)*ki+klastcw RS2 2*t-1 RS2 0
I ki+klastcw-1 I ki+klastcw-2 I klastcw RSL 2*t-1 RSL 0
I klastcw-1 I klastcw-2 I 0 RS(L+1) 2*t-1 RS(L+1) 0
klastcw bytes
k i bytes
Figure 10 Reed Solomon byte grouping
Submission page 44 UPA-OPERA
2*t bytes
2*t bytes