Is a flip to LTE really that easy for Clearwire?

It's no secret Clearwire has been posturing toward LTE for some time. The firm's first-quarter conference call was another strong indication that LTE is on the road map. But timing is the critical question, and at what cost?

During its conference call with analysts yesterday, Clearwire announced it changed the terms of an agreement it has with Intel that allow either party to exit the deal with 30 days notice. The previous agreement had forced Clearwire to use WiMAX through Nov. 28, 2011.

The move is part of a series of comments and actions on behalf of Clearwire since CEO Bill Morrow declared on stage at the CTIA Wireless trade show in March that he advocates one all-IP 4G standard and that Clearwire could add LTE once it reaches the equivalency to WiMAX's capabilities. Shortly after that, Clearwire, along with vendors, asked the 3GPP to develop specs that would enable TD-LTE's entrance into the 2.6 GHz band.  

Yesterday, in response to questions from analysts, Clearwire CFO Erik Pursch said the ecosystem for WiMAX and LTE was converging so much and that the underlying technologies of LTE and WiMAX were close enough that Clearwire could make the transition rather inexpensively when it comes to network costs. Handsets might be the sticking point, however, if Clearwire makes a change to its radio network.

At this point, engineers haven't figured out how to flip from WiMAX to LTE without making fundamental changes to the radio network, Dan Warren, GSMA's technical director, told me in a recent interview. "It's got to be something done as a business decision to retask TDD spectrum, and that becomes tough because you run the risk of potentially running two technologies," Warren said. "It's technically challenging to retask spectrum. The two (LTE and WiMAX) are OFDMA but what you do above that is the question. There are different frame structures and different ways to carve up spectrum."

So it's difficult to believe that Clearwire could flip to LTE before Nov. 28, 2011. But maybe Clearwire's engineers have something up their sleeves the rest of us don't know about. Maybe some vendor has promised an easy solution. Maybe software-defined radio (SDR) will be able to make the flip rather painlessly. But then, just as Clearwire indicated, you have an embedded base of WiMAX device users who would need new devices. It's just may not be as rosy as it sounds.--Lynnette