The TV white spaces (TVWS) spectrum was once proclaimed as a resource that would transform the wireless industry, from supporting low cost broadband access to supporting low power IoT networks.
In fact, other IoT technologies such as LoRa, in 868/900 MHz spectrum, left the TVWS initiatives behind, and the spectrum has proved too limited in capacity to add significantly to the WiFi landscape. But Microsoft and Google, in particular, have continued to push this source of unlicensed spectrum, in broadband projects in emerging economies, and in the USA. Microsoft set up the AirBand Alliance in 2017 to promote TVWS solutions, mainly for rural fixed wireless, both for consumer broadband and IoT.
Several recent, if belated, developments seem to be improving the outlook, despite persistent concerns about interference, notably with hospital networks. And now, a new cooperation with the IEEE could see new momentum behind TVWS, in some IoT applications as well as its heartland use case in rural broadband.
The TVWS can certainly be credited with being a precursor of the CBRS spectrum sharing system, and doubtless others to come round the world. A lot of the hard work on creating spectrum access systems (SAS) to protect incumbent users – the broadcasters in TVWS – from interference from other devices, was first done in these frequencies, and then repurposed for the higher capacity, more robust CBRS band.
Nevertheless, Microsoft and the WhiteSpace Alliance (WSA) still believe there is a strong case for using TVWS spectrum in the USA to reach rural and remote users, in what the Windows giant now labels ‘Frugal 5G’; and to make some machine-to-machine applications more affordable to deploy. They particularly see potential in services, such as smart grid, that require coverage even in very remote areas, especially as there are generally more available channels in these sparsely populated places where broadcasters are not very active.
The WSA has signed an agreement with the IEEE Standards Association, which could help to build confidence, and a broad ecosystem, around TVWS – something it has always lacked, partly because, in the peak of enthusiasm for the spectrum, there were several competing technologies aiming to use the frequencies. That meant it did not achieve the united stakeholder front that has largely formed in CBRS.
Now the two organizations say they will cooperate to accelerate uptake, especially for broadband services in underserved areas, but M2M services. They cite smart grid and healthcare among the target applications, along with rural broadband.
“TV White Space holds particular promise for connecting currently underserved consumers at price points appropriate for large rural and remote populations, a solution sometimes referred to as ‘Frugal 5G’,” the two groups said in a statement. “WSA and IEEE-SA are currently defining several activities with relevant stakeholders from developing countries on projects that will involve spectrum sharing for applications such as rural broadband, e-commerce, e-health, smart cities and smart grid.”
In another positive development, the FCC last week issued new draft rules for TVWS operations, aiming to address some technical concerns, particularly related to identifying the location of devices.
This followed a tentative pact between Microsoft and the National Association of Broadcasters (NAB) about “potential modifications to the Commission’s TVWS rules to facilitate operations in rural areas while ensuring that licensed operations are protected”, as the NAB put it in a filing with the FCC. “NAB agrees that the Commission should pursue certain, but not all, changes Microsoft is seeking, as long as the Commission takes important steps to protect licensed users.”
The NAB has always opposed unlicensed operations in the TVWS but seems to have largely accepted proposals which Microsoft put to the FCC in October. If the FCC ratifies the compromise, it will remove a significant barrier to chip companies supporting the TVWS in their products – essential if affordable devices are to become available, and if Microsoft is to hit its target of seeing 2m rural citizens connected via TVWS links by 2022.
Rise Broadband, the largest privately owned fixed wireless operator in the USA with about 150,000 subscribers, has lent its weight to Microsoft’s project, announcing that it is launching its first TVWS services this year.
“Thanks to Microsoft for injecting some life into the TV White Space equipment ecosystem,” said Rise Broadband’s Jeff Kohler. “All of the testing that we’ve done in the field and that we’ve done in the lab shows that we’re going to be able to deliver well in excess of the FCC-mandated broadband speed of 25Mbps/3Mbps. We’ll be able to do it at good distances and with much better propagation than any other spectrum tool that we have in the bag right now being installed in low band.”
He said that, previously, Rise had not adopted TVWS solutions because they were too expensive, and the technology was out of date and data rates too slow. Kohler added: “It looks like we’re seeing a lot of advancement in that space right now. That’s a new tool in the bag for us when we really need a sub-1 GHz solution for line-of-sight reasons and terrain reasons and foliage reasons.”
However, there are still concerns about interference. The New America Association recently warned that there are risks to wireless medical telemetry services in hospitals which use Channel 37 of the TVWS band.