There are online calculators http://www.radiolabs.com/stations/wifi_calc.html http://www.radiolabs.com/stations/wifi_calc.html note that the cable loss mention

There are online calculators http://www.radiolabs.com/stations/wifi_calc.html http://www.radiolabs.com/stations/wifi_calc.html note that the cable loss mentioned is the antenna feeder cable And Cisco Press do some good books on the basics of WiFi network design.