The additional read operation permits interleaving to continue without waiting for {HEAD ~ a next frame} of data to arrive at {TAIL ~ the interleaver} 
The additional read operation permits interleaving to continue without waiting for { HEAD ~ a next frame } of data to arrive at { TAIL ~ the interleaver }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL