Canada proposes spectrum sharing for broadcasters and public safety operators

Broadcasters and public safety mobile operators could be heading for a showdown if Industry Canada follows through on a proposal to allow the two groups to share the same spectrum. Usable spectrum for the mobile industry below 1 GHz is rapidly running out, giving public safety operators reason to covet the 746-806 MHz band, currently used for over-the air TV channels 60-69. Broadcasters are expected to eventually vacate those frequencies once they migrate to digital television (DTV), but public safety operators are growing impatient. Until then, it’s uncertain whether the band can be shared by two such dissimilar services. In its Gazette Notice DGTP-004-01, Industry Canada hasn’t offered any technical evidence that sharing the bandwidth on a co-primary basis is feasible. Canadians have a high expectation that their TV signals will come in without interference, while public safety operators such as police and ambulance services are clearly afraid of interference from the other side. Consulting engineer Wayne Stacey says working out the details of spectrum sharing will be a technical challenge. "The Americans, for a while, have tried to use the land-mobile in the lower UHF channels, from 14-20… But, they’ve been stymied because when they actually came down to make the sharing work, they found that it didn’t work very well in a lot of places," he explains. He notes that, due to the nature of the services proposed for the band, that technical criteria will have to tend toward the cautious. "Yes, there’s one transmitter there occupying 6 MHz of spectrum. But that’s not one user. It’s that one user plus 2.5 million viewers who watch that television that are the true users of that spectrum," he says. "That’s what the department has to contend with. It’s one thing for the broadcaster to find some impact on their business. It’s quite another for the government to be faced with complaints from many, many, many people who would suffer interference." The U.S. has much firmer plans for clearing the spectrum. The government has given broadcasters until 2006 to vacate the space, raising serious cross-border interference issues if Canada doesn’t move to harmonize its usage by then. But Stacey isn’t convinced that the looming American date will hold firm. Under the U.S. timetable, Stacey notes that 85 per cent of people in a television service area have to be capable of receiving the digital service before the analog transmitters are required to discontinue – or 2006, whichever comes later. "You can imagine how challenging it is to get DTV receivers in many millions of homes in that short a time. Certainly, the American broadcasters are looking at this as something that will probably take a considerable more amount of time to achieve." Still, potential public safety mobile operators are eyeing the band greedily as a potential solution to their scarcity woes. DTV is far more spectrum-efficient than analog, with as many as six to nine DTV signals fitting into a 6 MHz channel. As older analog transmitters are shuttered in favour of digital, the government would like to put the excess spectrum in the hands of mobile operators. But Stacey says surplus will be preceded by the need for more broadcast spectrum during a transition period when both digital and analog transmissions share the airways. Industry Canada has told the CRTC that it won’t issue broadcast certificates for low-power television stations in channels 60-69, partly to accommodate the need for mobile spectrum at 700 MHz. The Canadian Wireless Telecommunications Association’s VP of regulatory affairs, David Farnes, says his organization will likely support freeing the spectrum for mobile uses. The Radio Advisory Board of Canada has already put out a call for a joint committee of mobile operators and broadcasters to work on the problem. Comments on the matter are due Sept. 24.

Canada proposes spectrum sharing for broadcasters and public safety operators

News | July 9, 2001

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