White Space Broadband Where Broadcasting Began


Was it fate or just a coincidence that one of the first tests of white space broadband would also be at the location where regularly scheduled radio broadcasting began? That Charles D. Herrold opened the Herrold College of Wireless and Engineering and later began broadcasting at 50 West San Fernando in San José was a surprise to Adaptrum’s Darrin Mylet. Herrold’s launch of his radio station in 1909 was a precursor to an explosion in radio transmitters, which led to interference and, eventually, government rules for allocating and the use of spectrum.

To see a video from one of the earliest tests of TV White Spaces (TVWS), click here. Additionally, this article provides more detail of the technology behind TVWS and some of the early trials.
Fast-forward 100 years to a new approach by Adaptrum and others, where radios dynamically manage allocation of spectrum, instead of government agencies. The key to this automation is the use of cognitive radios. These radios sense when spectrum is being used and shift to different frequencies, as needed. Further, the use of the so-called TV white spaces (TVWS – using unused TV broadcast channels for broadband connectivity), allows the use of fallow spectrum. These relatively low, sub-1 GHz frequencies allow for propagation through trees and buildings, as we found in our testing around downtown San José last week.

With power levels of 100 milliWatts, which is the specification for personal, portable devices (4 Watts EIRP for fixed devices), we were able to achieve multi-megabit connections over distances of several blocks, as seen in the above video. Set-up was straight-forward; easier than aligning a point-to-point WiFi link. We were able to set up point-to-point connections in four different locations in about two hours with Adaptrum’s commercially available equipment.

To be clear, white spaces and the associated technology is another tool that, as Adaptrum’s Darrin Mylet says, can be used to ensure that the Internet gets to all the nooks and crannies. Whether it is crossing a river, penetrating through building in urban areas or connecting libraries, TVWS provides a fast way (no FCC licensing, easy equipment set-up) to connect Internet to locations where it otherwise might not be practical.

As Mylet alludes to in the above interview, what may be the most exciting thing about the TVWS approach is the idea of the localized use of spectrum. TVWS could represent the next generation of citizen broadcast, such as was seen in the 1970s with voice radios and, more recently, with data transmission via WiFi. Time will tell whether the above demonstration points to something as revolutionary as what Herrold started 100+ years ago.