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