If there is no substantial transmission data to be transported by {HEAD ~ the feedback frame} on {TAIL ~ the reception side}, then the feedback frame is arranged such that data unrelated to feedback information including at least the transmission data length, the transmission data and the data frame number within the feedback frame, is substituted with a predetermined fixed pattern, and thereafter an error detecting code for all the data is added thereto 
on
If there is no substantial transmission data to be transported by { HEAD ~ the feedback frame } on { TAIL ~ the reception side } , then the feedback frame is arranged such that data unrelated to feedback information including at least the transmission data length , the transmission data and the data frame number within the feedback frame , is substituted with a predetermined fixed pattern , and thereafter an error detecting code for all the data is added thereto
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH