{HEAD ~ The base station} 20, wherein each of the plurality of {TAIL ~ mobile stations} has a corresponding reference signal 
{ HEAD ~ The base station } 20 , wherein each of the plurality of { TAIL ~ mobile stations } has a corresponding reference signal
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH