What is the best position and direction for an antenna to get best wi-fi signal in a room about 15 meter away and a door and a wall from the router

Most routers have a vertical antenna system

In simple terms the typical radiation pattern of a Wi-Fi router is like a large doughnut, sitting over the router. Angling the antenna will make very little difference but may make some due to the reflections etc. This will be only discovered by trial and error.

Thus in an open space signal direction all round is good, but not above or below the device.

This is then of course modified by surroundings.

Block walls, windows and metal objects will all defelect or reflect the signal.

What effect the surroundig will have on any signal is hard to say without eiother a map or a site survey.

To increase the signal in any direction you need to focus it just as you would focus the light from a spot lamp

If you will search the internet you will find various ways of of focusing your Wi-Fi signal to get better performance in one direction (at the loss of performance in another direction. Some off these ways are free, cheap and easy others are not.

I hope the above helps if not actually giving you the simple answer you were looking for

Not sure if this will help in any way , may be it can be modified in some way

http://www.freeanten...ects/template2/

It's actually amazing, everybody boost or enhance the antennas on the router side. - but givenall please stop double postings. same topic here