Sprint puts off WiMax data cap

Its 3G monthly cap jolted some users, so Sprint has no plans to limit 4G use for now

Sprint Nextel saw subscriber behavior change after it introduced a 5GB monthly cap on its 3G data plans, and that's part of the reason the carrier is wary about capping data consumption on its 4G WiMax service, a company executive said Tuesday at the MobileBeat conference in San Francisco.

Some consumers became worried about using data after the cap was imposed several years ago, said Todd Rowley, vice president of 4G (fourth-generation) at Sprint. That's the last thing the carrier wants to happen with WiMax, which it is investing heavily in building and promoting alongside partner company Clearwire. The WiMax network can accommodate more data use than 3G can, and Sprint today is more interested in encouraging use than in reining it in, Rowley said.

The WiMax network is designed to offer an average of between 3M bps (bits per second) and 6M bps, far higher than the average for its EV-DO (Evolution-Data Optimized) network of about 600K bps to 1M bps. It is also designed to be a more efficient network, allowing the carrier to deliver each bit at lower cost.

Consumers seem to be embracing the freedom of the completely unlimited service. Clearwire has said users of its WiMax service, which runs on the same network, are downloading an average of 7GB per month. Rowley noted that the average Sprint WiMax subscriber downloads less than that, because most are mobile or nomadic rather than fixed-location users.

At some point in the future, if average data use goes much higher -- Rowley quoted an arbitrary figure of 20GB per month -- Sprint might cap users' monthly downloads, he said. All of Sprint's WiMax plans also include 3G service and are subject to the usual 5GB cap for use of that network. Sprint has no current plans to remove the 3G cap, Rowley said.

Sprint and Clearwire, which formed their joint venture in 2008, are sitting on a huge amount of radio spectrum that they are not even close to exhausting, according to figures Rowley shared. The deal pooled significant holdings in the 2.5GHz band, adding up to between 120MHz and 150MHz per market, he said. Today, they are using no more than 30MHz of that spectrum in most markets, Rowley said. They could utilize another 30MHz in those markets to boost their capacity and still have room to deploy another network technology on the remaining frequencies, he said.

Sprint is still considering its options with regard to LTE (Long-Term Evolution), the 4G technology that most carriers around the world plan to deploy. Depending on which of their spectrum bands they used, Sprint and Clearwire could adopt either the TD (time-division) or the FD (frequency-division) variants of LTE, Rowley said.

TD-LTE uses the same frequencies for both upstream and downstream traffic. This is similar to almost all deployments of mobile WiMax, including Sprint's, according to analyst Monica Paolini of Senza Fili Consulting. FD-LTE divides the spectrum into frequencies for upstream and for downstream traffic. This is the way most traditional mobile networks are set up, so most established carriers adopting LTE are using FD-LTE, Paolini said. However, partly because of the rules applied to spectrum bands, TD-LTE is being adopted by some large service providers in Asia.

Choosing TD-LTE would give Sprint an easier transition from its WiMax network, while FD-LTE would probably give Sprint subscribers access to a wider variety of handsets, especially ones that would allow roaming to other domestic and international LTE networks, Paolini said.

It's unlikely Sprint will make any decision about a possible move to LTE for another year at least, Paolini believes. But the move would make sense if the alternative is to be the only major mobile operator using WiMax in the U.S., she said. "Roaming is really important," she said.

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