|--- SCHC ACK Header ----|--- Bitmap --|
         |-- T --|-M-| 1 |6 5 4 3 2 1 0| (tile #)
+--------+-------+---+---+-------------+
| RuleID |  DTag | W |C=0|1 1 1 1 1 1 1|  with uncompressed Bitmap
+--------+-------+---+---+-------------+
   next L2 Word boundary ->|

+-- ... -+- ... -+---+---+-+
| RuleID |  DTag | W |C=0|1|                  transmitted SCHC ACK
+-- ... -+- ... -+---+---+-+
   next L2 Word boundary ->|