Then, {TAIL ~ the feedback frame} is transmitted from {HEAD ~ the reception side} to the transmission side 
Then , { TAIL ~ the feedback frame } is transmitted from { HEAD ~ the reception side } to the transmission side
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH