determining means for determining {TAIL ~ whether a first portion} of said feedback frame that is redundant to said {HEAD ~ data frame} consists of a first predetermined bit stream 
determining means for determining { TAIL ~ whether a first portion } of said feedback frame that is redundant to said { HEAD ~ data frame } consists of a first predetermined bit stream
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH