A recent report on tests conducted on a pilot LTE public-safety network in the San Francisco Bay Area concluded that running real-time video over just the 10 MHz of broadband spectrum available to public safety today won’t be adequate.
Wireless consultant Andrew Seybold tested the pilot network and concluded that the additional 10 MHz of spectrum from the D Block in the 700 MHz band will be required, in addition to proper network management strategies that will need to be put in place.
Seybold concluded that video communications from the edge of thecoverage cell — about 4 miles in this test case — would not be possible with 10 MHz of spectrum, or even 20 MHz of spectrum. 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, he reported.
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.
While it’s an unfortunate situation for public safety to be in — since the reallocation of D Block spectrum to first responders is no sure thing — some commercial operators are in the same boat. Indeed, one of the hottest topics in the commercial mobile industry is the notion of network optimization — using tools to ensure that traffic is prioritized and capacity is offloaded or loaded more efficiently. And video is at the center of it.
Nokia Siemens Networks this week announced its concept of a software-driven mobile network called Liquid Net that is capable of self-adapting to network loads. The idea is to create software-defined applications that run on multipurpose hardware rather than conventional networks with dedicated software and hardware stacks. Liquid Net software runs on processes, which enables the use of multipurpose, shared hardware. That means processing capacity can be pooled and reallocated based on the application and location.
MetroPCS is an interesting example. It is using just 5 MHz of spectrum in the Advanced Wireless Services (AWS) band to offer LTE services. While its data speeds aren’t as fast as speeds seen on Verizon Wireless’ network, which uses 20 MHz, it is relying on network engineering techniques and Wi-Fi offloading to manage the data influx.
LightSquared, which is proposing to build a wholesale nationwide LTE network in the L-band satellite spectrum, has proposed to use just a 10-MHz swath of its spectrum to avoid interference with GPS signals. It claims that will be sufficient for a few years, despite the fact that it plans to carry a load of traffic from its wholesale partners.
In the end, physics can’t be defied. Network operators only can cram a certain number of bits into each hertz. As Seybold concluded, public safety needs another 10 MHz of broadband spectrum. But in the meantime, there are many lessons and tricks to be learned from the commercial operators that are out in the trenches and grappling with the surging amount of data traffic on their networks.
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