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