The method 2, wherein performing {HEAD ~ the MIMO mode switching} for {TAIL ~ the cell} comprises: 
for
The method 2 , wherein performing { HEAD ~ the MIMO mode switching } for { TAIL ~ the cell } comprises :
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH