1)  Try to have better Clutter thought.

2)  Check Antenna sort, i.e. 

A) Electrical Tilt Antenna sort; (The tilt meter in the radio wire must be on completely opened mode)
B) Dual boycott X Polarized Antenna: (Feeder must be joined with the Operating band of GSM in the Circle)
C) Single Band X Polarized Antenna.
D) High Gain Antenna

3)  Check Mechanical Tilt, Antenna must be in Straight or down tilt Position.

4)  Check the Antenna position on the off chance that it is in up tilted mode than down tilt it.

5)  Check the Feeder link for Sector Swap.

6)  Check the Feeder Connector at Antenna Port for any relaxed p
7)  Check Alarm in BTS end.

8)  Get Confirmed for any Alarm at BTS from O & M: Alarms Like,
A) RX Diversity lost
B) RBS Fault
C) VSWR points of confinement surpassed
D) RX & TX Path lopsidedness

9)  Check the Cell Performance, as
A) TCH Drop
B) SD Drop
C) TCH Traffic
D) TCH Availability
G) RX Quality
H) Neighb

Now If every thing found OK Start the Drive test.