The past two decades have seen a revolution in telephony, infusing new meaning into the concept "any time, anywhere" connectivity. Businesses know they can increase productivity and improve customer service with mobile voice communications within their facilities, and most companies have long used cellular phones to deliver this capability. As WLANs have solved most of their security and QoS problems and begun to take hold in the corporate sector, enterprises have started to explore VoWLAN as an alternative to cellular telephone coverage. The thinking is that an in-house mobile wireless infrastructure gives enterprises more control over their own destiny, integrates wired and wireless telephony in the same IP infrastructure, reduces calling charges and also addresses the problem of highly variable cell phone coverage inside some buildings. So should enterprises replace their cellular telephony contracts and move wholesale to IP telephony? Not so fast. Analysis