Wang of NSN makes the same point. "We want to protect our customer investment. In the BTS side, many components that can be used for Wimax and LTE, so it's an upgrade path. The whole TD-LTE ecosystem will be ready by 2011 or 2012, so you customers can roll out Wimax now and have an upgrade path to TD-LTE once that ecosystem is ready."
Put another way, today's Wimax networks are - potentially - tomorrow's TD-LTE networks, which in turn strengthens the case for deploying Wimax today, says Richard Ye, brand director of product R+D system and wireless product operation at ZTE.
"If operators see a solution that can run both Wimax and TD-LTE, for sure they will launch Wimax first, because they can make money now, and use a small investment to reconstruct for TD-LTE," Ye says. "You get to keep the subscribers you built up with 16e, and then if you upgrade to 16m or TD-LTE, it's a software decision. You can even run both, if you want to do so and have enough spectrum."
Khattab of wi-tribe adds that the amount of extra investment needed to make such a transition isn't all that high. "When you look at all the costs involved in building a Wimax network - the core, the backhaul, site rental, human resources, utility costs, the whole thing - the actual Wimax part is just the base stations and the CPE, which only accounts for around 12% of your investment," he says. "That's all you really have to change to migrate to LTE, so from an investment point of view, that's relatively painless."
Not so simple
To be sure, Wimax-to-TD-LTE migration is not endorsed by either the GSM Association or the Wimax Forum, both of which are trying to build scalable ecosystems and massive subscriber bases for their own technology. But, says Wang of NSN, "When you talk to individual operators, they are highly interested in TD-LTE, because it gives them a mainstream evolution path. And if you ask Wimax operators in particular where they want to go two or three years down the road, they all say ultimately LTE."
On the other hand, GSMA and Wimax Forum officials aren't the only ones skeptical of the viability of a Wimax/TD-LTE evolution plan.
For a start, says Fabricio Martinez, group services product director at network planning consultants Aircom International, the 12% investment figure from wi-tribe is far too low.
"Even in the most optimistic of scenarios we see around 18% to 20% as the lowest possible loss, and with detrimental effect on the quality of the network being offered," Martinez says.