handover failure

we are facing a unique problem of handover failure from one sector to another sector in same site in more number of sites. Nortel and ******** systems.
The statistics shows good number of success against attempts from one sector to another sector but in the reverse success is in less numbers against attempts. Any suggestions pl.

:):)

There is no interference on the cell that failure is high

we are not able to fox this problem with drive. With atol it seems to good . The statistics showing this figures.