Real world effects such as filtering, multipath time spread, and time base error destroy orthogonality and introduce a degree of {HEAD ~ cross coupling} between {TAIL ~ supposedly orthogonal channels} 
between
Real world effects such as filtering , multipath time spread , and time base error destroy orthogonality and introduce a degree of { HEAD ~ cross coupling } between { TAIL ~ supposedly orthogonal channels }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL