D Block spectrum in the 700 MHz band should be reallocated to public safety and proper network-management strategies will be needed to support video from the scene of incidents, according to a report released today regarding tests on an LTE pilot network in the San Francisco Bay Area.

Currently, public safety has been allocated 10 MHz (5x5 MHz) of broadband spectrum in the 700 MHz band. First-responder organizations have expressed support for legislation that would reallocate the 10 MHz D Block — slated for commercial auction under existing law — to public safety to provide a 20 MHz spectral foundation for a proposed nationwide, interoperable LTE network for first responders.

In April, the first public-safety LTE pilot network in the San Francisco Bay Area was tested by mobile wireless consultant Andrew Seybold. In his report, Seybold notes that 10 MHz of spectrum will not be enough to support real-time video — arguably the most-anticipated application for public safety — from a hostage or bomb-threat incident, unless the event occurs within a half mile from the cell site.

“5x5 isn’t going to hack it, and 20 MHz will, except at cell edges,” Seybold said.

Indeed, video communications from the edge of the LTE coverage cell — about 4 miles, in this test case — would not be possible with 10 MHz of spectrum or 20 MHz of spectrum, according to the report. However, video from the middle of the LTE coverage cell — 1.5 miles — would be possible with 20 MHz of spectrum, but it would not be supported with just 10 MHz of spectrum, according to the report.

Another key note in the report is that, when the capacity limit of the LTE sector was reached and another video stream was attempted within the sector, all video streams from the cell sector became unusable, Seybold said.

SIDEBAR: Preliminary results from Bay Area tests

“We were not running priority, and we were not running quality of service, but when you push an LTE network over the brink, it collapses,” Seybold said. “That’s the bad news for everybody. If you’ve got four videos up and running, and everybody’s looking at them in real time and you try to shove a fifth one down the pipe, you’ll lose the other four — it puts everybody out of business.

“Now, with quality of service and priority, that can probably be avoided, but I don’t have any verification of that yet. … There is no doubt in my mind that there will be people who are managing the network, and they’re going to change the resolution on the videos [to optimize network usage].”

The tests were commissioned by the East Bay Communications System Authority, which oversaw the buildout of the pilot LTE network.

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