Network Management

My company runs a Wireless network of internet acess to about 60 subscribers located in a town of about 10kilometers radius.With 6 base stations cnfigured with a router.My problem is that these subscribers complain of intermitant break in their reception of signals,how do I slove this problem?
(2)How do I get these subscribers under one authentication(ie giving or removing access to the network form a single base station).