Good info so far. 150 ft...with walls...is unlikely to be good performance from any uni-directional AP.
Besides the things you can see and measure (distance, number of walls, etc), there are things you can't see that will affect range:
Wall construction
Unseen things in walls (plumbing, ductwork, etc,)
Other devices on network
Other networks or other noise/interference
So, to recap:
Get an AP much closer ( via: ethernet, powerline, mesh)
Get a directional and/or high gain antenne pointed to the spot you need it
I installed a Unifi Mesh AP on the outside back wall of my house to cover the back yard (two other APs inside). The coverage is good in the unobstructed yard. Inside a garage about 50 feet away, the signal is weak through a stucco wall. I could likely boost it a bit with a directional antenna, at a cost of less wide-angle coverage of the entire yard.