thank you for your reply.. they have a way have many WIFI access point but only 1(one) SSID? how can i do that? what the best step i can make?
In this sort of situation what I usually do for my clients is install a good router/AP centrally located (as previously suggested), but I will then install additional bridged AP's on each floor so that everybody gets a good connection - make sure that each AP uses a different channel so you get best throughput. Each AP then is a bridge to the main (central) AP/router. Using 802.11n with maximum range, and (if possible) high-gain antennas, is also recommended.