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

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