For many middle and large sized companies wireless connectivity has become an adopted technology. No longer are the requirements of a hard line connection or worries of connection breaches. Encryption has taken care of that. Here are a few tips to improve your wifi network.
Upgrade. Dump those old b routers and go with the latest and greatest wireless n technology. If you can't, then try for g routers. Even investing in a high gain antenna is a good solution. Check for the latest firmware for your model. Sometimes those frequent drops can be fixed with a little software upgrade.
Placement. If you don't want to spend any money do a bit of rearrangement of your routers. In the center of the office and not in the corner without obstructing furniture near it. Treat it like a satellite where people should be able to have line of site to the access point.
Security. Ensure that all of your routers have changed from the default admin factory password. As well be sure to check that a uniform encryption protocol is being used by all of your wireless network. Passwords should be a minimum of 8 characters involving letters and numbers (upper and lowercase if you want to get fancy).