For {HEAD ~ the coded data} that was transmitted via {TAIL ~ a communication channel}, a known code portion thereof that is a code portion corresponding to known data is detected 
transmitted via
For { HEAD ~ the coded data } that was transmitted via { TAIL ~ a communication channel } , a known code portion thereof that is a code portion corresponding to known data is detected
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL 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