It is a very typical problem, that is encountered for most micro cells in many cities. Many solutions can be used, depending on your mobile network architecture :
multiband ? (upper band, lower band, indoor band ?)
mono band ?
what kind of handovers do you perform to enter your micro, and to exit your micro ?
in alcatel, there is a special type of handovers that exist, for all cells which are defined as “MICRO” type. This handovers will provide a quick exit from micro cells to neighbours cells, as soon as the Rxlev is below a certain threshold (whether or not power control is applied), or as soon as the number of “bad decoded SACCH frames” exceed a certain amount.
Do you have such emergency HO for micro cells ?
otherwise, you can reduce HO_MARGIN and reduce the POWER BUDGET averaging window between micro cells.
And finally, you can also decrease the “emergency HO due to low signal strength in DL” threshold to exit a micro cell (for instance -85dBm instead -92 dBm)
Hope it helps,