In April, the first public-safety LTE pilot network in the San Francisco Bay Area was tested by mobile wireless consultant Andrew Seybold (report and pdf).
The demonstration network includes an LTE core, 10 sites and 330 Motorola public-safety LTE user modems for first responders. The BayWEB network is a mobile broadband data network that will serve the 10-county Bay Area, which spans 7,368 square miles and covers a population of approximately 7 million people living in more than 100 cities and towns. The system will eventually support nearly 200 unique radio sites across the Bay Area
Seybold says that 10 MHz of spectrum will not be enough to support real-time video unless the event requiring live video occurs within a half mile from the cell site.
“5×5 isn’t going to hack it, and 20 MHz will, except at cell edges,” Seybold said.
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.
At 3.8 miles, the communications capacity of each LTE sector is maxed out when only one video is streamed up to the tower. It’s a sobering assessment.
Cellular LTE networks use similar gear but are more dense and have more spectrum. Verizon, for example, uses paired 10 MHz channels for LTE. As a consequence, commercial networks have more capacity per square mile.
Land Mobile Radio (FCC Bureau) generally utilizes handsets with ten times the power (2 watts instead of 200mW), but connect to radio towers that are spaced much further apart (15 miles instead of 1.5 miles). First responders get hit two ways; more people share a tower and modulation becomes less efficient (using more spectrum) at cell edges.
The network was funded with $6 million from a FEMA Urban Areas Security Initiative grant, and other federal grants. Motorola applied for $50 million in federal broadband funds (pdf) to build and operate the Bay Area Wireless Enhanced Broadband network (pdf). The cost of the demonstation project was $72,483,637, says Motorola pdf.
The other half of the 700 MHz public service band is currently reserved for narrow band voice communications. It’s interoperable (using Project 25 radios), so different agencies can talk to each other.
The “D” block is the contested 6 MHz spectrum pair (12 MHz total). Some in Congress want to auction the “D block” off to commercial LTE providers for shared public/private use. Others want to make the “D block” exclusively dedicated for first responders, in conjunction with their current 12 MHz of broadband spectrum.
Smartphones are changing how departments can respond to emergencies. Powerful apps are moving to smartphones everywhere. That won’t stop – and neither will Voice over LTE.
Mission-critical, voice-over-LTE is possible, but it’s not available today. Some industry pundits say mission-critical voice over broadband could be available within a few years, while others project it will not happen during the next decade.
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