The CTIA telecom trade group has now joined Sprint Nextel and T-Mobile in calling for FCC licensing around "white space" spectrum, against the wishes of major device makers to open up the spectrum for unlicensed wireless access.

The wireless telecom trade group CTIA has chimed in on the growing debate over the use of unused "white space" in already licensed spectrum, siding -- for the most part -- with Sprint Nextel and T-Mobile. Essentially, the group views possible device interference in the unlicensed white spectrum as a threat to operators' investments in future 4G broadband networks.

But in a compromise measure, more details of which were learned yesterday, the CTIA's new FCC proposal would also leave a small portion of the white space spectrum open for the continued study of unlicensed devices .

Meanwhile, the National Association of Broadcasters is continuing to oppose the existence of any signals in the white space whatsoever -- either licensed or unlicensed -- claiming that the operation of devices in this spectrum would get in the way of TV broadcasting.

A long and complicated battle over this issue started boiling over in January, when the NAB released a letter sent to the FCC responding to accusations by yet another industry group, the Wireless Industry Association, that the NAB had engineered a "misinformation campaign" about introduction of devices in an unlicensed white space spectrum.

The FCC had been testing the use of devices in this spectrum to see whether unlicensed access to the spectrum makes sense.

"In July [2007], a report by the FCC concluded that sample prototype 'white space' devices did not accurately detect broadcast signals and caused interference to TV broadcasting and wireless microphones," according to the letter from NAB President Kenneth K. Rehr.

Also in January, Sprint-Nextel and T-Mobile filed their own petition with the FCC, urging it to open up the spectrum but only on a licensed basis, for use with wireless backhaul services.

"Because backhaul comprises a significant cost for wireless carriers, and incumbent local exchange carriers' special-access charges are exorbitant, Sprint Nextel and T-Mobile must find more affordable alternatives to the ILECS's special-access offerings," reads their January filing.

In February, Microsoft -- one of Google's allies in the WIA and its sister group, the White Space Coalition -- released a letter sent to the FCC admitting that one of two devices designed and made by Microsoft's partner Metric Systems Corp. for use in unlicensed white spaces had "experienced an apparent power issue."

Google stepped into the FCC filings near the end of March, with a letter proposing its open source Android -- a competitor to Microsoft's Windows Mobile -- as a platform for use in unlicensed white space.

Aside from Sprint Nextel and T-Mobile, other large players in the CTIA include Verizon Wireless and AT&T, two US carriers that are now reaching the concrete planning stages for 4G networks, set to launch either next year or in 2010.

Sprint Nextel and T-Mobile are also members of the Open Handset Alliance, a trade group launched by Google last year in support of Android. But neither Verizon Wireless nor AT&T belong to Google's OHA.

In addition to Google and Microsoft, other major vendors within the 24-member WIA include Hewlett-Packard and Dell. The eight members of the White Spaces Coalition, on the other hand, include Google, Microsoft, HP, Dell, Intel, Philips, Earthlink, and Samsung.