4:15 PM -- Actually, I have always assumed that fixed WiMax would be a great success in the access market, and in emerging economies and rural areas. But the availability of mobile WiMax raises the question: Why go fixed when you can have mobile? One of the really big trends in networking overall today, enabled by cost-effective mobile broadband, is the replacement of fixed services by mobile. It’s already happening, big time, with voice services. But with the increasing availability of mobile broadband services along with those voice offerings, mobile access to the Web could become the norm as well. And, yes, we can build small mobile communicators with decent screens more that suitable for the application. Have a look at the Nokia 770 if you don’t believe me.

I had assumed -- until the Sprint Corp. (NYSE: S) announcement -- that the winning combination would be broadband cellular (3G/3.5G/3.75G/whatever) coupled with WiFi. So along comes Sprint with what we can all agree is a 4G mobile-WiMax rollout, and, OK, we won’t see it until the end of next year, but, wow, I mean, this is Sprint! Yes, the big cellular carrier! We’d all assumed they would deploy WiMax in their 2.5 GHz. spectrum, but the announcement could be read that this isn’t just a data service or adjunct offering; it is instead the future of Sprint and perhaps mobile communications overall.

Sprint still has some splainin’ to do, though. OK, I’m an IT manager for a big company. Do I continue that planned rollout of EV-DO to my 30,000 people in the field, or do I wait for WiMax and 4G? And will WiMax have enough bandwidth to realize the 4G dream on its own, or are we now talking a converged WiMax/WiFi offering? And what will Sprint’s competitors -- particularly Cingular Wireless and Verizon Wireless -- do? This is going to get, um, interesting -- and quickly.

— Craig Mathias is Principal Analyst at the Farpoint Group , an advisory firm specializing in wireless communications and mobile computing. Special to Unstrung