There are two parts to a radio link .. the transmitter and the reciever
so if you create a strong transmit signal at your end but cannot modify the other end to give higher output power .. where's the gain ??
Try placing your aerial higher and somewhere where there is little chance of environmental signal disruption .. place the aerial on a vertical wall that has no iron reinforcement in it .. place it closer to the transmitting source and where there are the least number off walls for the signal to travel through.
You could try using an access point as a repeater somewhere between the two points you want to be in communication
trying to improve only one side of the circuit though seems a little bit unbalanced
and as johnwill asked .. describe your surroundings and your setup .. only he said it with fewer words ..
how far between the two wireless points ..
what's in between? walls, partitions, garden, forest
what environment are we talking about .. open office .. home .. apartment block
What electrical devices are operating in the in-between area .. microwave, PC's, Mobile phone aerials, other wifi equipment
and anything else that you might consider relevant to describing the surroundings