The issue you have to be concerned with is the client side transmission back to your AP. Most people go and boost the AP signal with an amp with no consideration of the client. Normally what you find is the client is the side needing the help. Way you can judge this is to look at both signal strength on the AP and the client. 9 out of 10 times, its the client's signal which is too weak to extend the coverage. YOu would need to do soemthing special (directional antenna?) on the client end to boost your range. With "long range" client installs, we have acheived distnaces of up to 3 miles without a amp on the AP.
i m also getting the same problem, i have to use 1200 access point with 12 dbi within 2 km distance. If you have found the solution of your query then plz let me know. I will really appreciate on your reply
the problem is described already in the post the client needs the power to cover the same distance as the AP iwth its high Gain Omni of 12dBi. Booth sides sender and receiver need to have the same output poqwer to hear each other.
It could be compared like if someone stand on the pole with an megaphone shouting to a individaul without at megaphone standing 500m meters away. the individual with the magephone will beheared by the other but his voice is not loud ebough to be heard by the individual with the megaphone