abdel,
Don’t worry, you can trust me about this, i really know what i’m talking about . I hope i’m not sounding too pretentious but that’s my job to know about this 🙂 anyway if i don’t know something then i would not pretend i do..
the gain and aperture of an antenna are fixed characteristics.
between your two solutions, i’d choose none of them ! i’d rather find another microcell site.
but if there is no other possibility, i’d say choice 2 is better. Choose an antenna with around 9° vertical aperture and maximum amount of fixed electrical tilt (12° or 14°). This kind of antenna gives you a gain of about 15dBi and a size of about 1.0/1.5m.
Install the antenna.
Next step : measure the coverage. If the cell range is very much too large, then increase the downtilt by 2°.
If the cell range is a little bit too large, then decrease the power.
If the cell range is too short, decrease the downtilt by 2°.
When you decrease the power of the cell, do NOT change the HO MARGIN, the power budget, or any other parameter : every radio algorithm uses a compensation in order to take into account the attenuation of the BTS TX POWER.
no need to change any parameter if you put attenuation.
if you don’t mind telling me, which country are you working in ?
-pix