TV white spaces fixed wireless broadband technology could benefit from small cell deployments, according to Microsoft. The technology giant has been conducting a trial tapping the two technologies in Cambridge, U.K. in a deployment dubbed Microsoft Project Belgrade and has been encouraged by the results.

“The project has successfully proven that cellular network deployment for TVWS is a highly feasible alternative to Wi-Fi,” said a press release from ip.access about the project. Ip.access provided the small cells used in the trial.

“Thanks to the affordability of small cells, the findings open up a whole host of use cases,” the press release continued. Use cases could include improved connectivity for unconnected people, ip.access said.

Microsoft Project Belgrade
TV white spaces spectrum is comprised of vacant TV channels, which in the U.K., as in the U.S., are available for unlicensed use. A major breakthrough occurred several years ago when database technology was developed to track where the spectrum is in use and assign TVWS radios to only use frequencies that are vacant in a specific geographic area.

Microsoft is a certified TVWS database administrator in the U.S. and its technology is in use in multiple countries.

Unlike other unlicensed spectrum, TV white spaces supports wireless transmission over substantial distances. According to a Microsoft web page about Project Belgrade, the bandwidth of one or more TV channels is enough to support speeds of tens of megabits per second.

In the U.S., TVWS equipment has been deployed by wireless internet service providers (WISPs) to deliver broadband to remote rural areas where traditional landline internet connectivity is not available or is only available at low speeds.

Microsoft Project Belgrade is not a rural deployment, however. Instead, Microsoft built what it called a “sizeable” cellular network testbed in the city of Cambridge.  The company worked with a local housing association to identify residents of five testbed locations who did not have home broadband. Each customer has a MiFi device, to which the customer connects laptops, tablets or smartphones.

Microsoft Project Belgrade Source: Microsoft

The project provides connectivity to more than 30 residents and according to Microsoft, some of these end users found jobs using the internet connectivity, reconnected to friends and relatives across the world, and started using online services.

The maximum indoor range was around 700 meters (approx 2300 feet). In outdoor tests that increased to 1.5 kilometers (just under 1 mile). The maximum link throughput observed was 60 Gbps (with 2×2 MIMO on a 5 MHz duplex link) and all clients got at least 4 Mbps.

Key lessons learned, according to Microsoft, include:

  • Some LTE bands, most notably the 600 MHz and 700 MHz bands, overlap with the TVWS spectrum and compatible hardware can be used as TVWS equipment.
  • Since some LTE devices can operate on TVWS frequencies with no modifications, they can be sourced for less than $100.

To date, cost concerns have driven U.S. WISPs to reserve TVWS technology primarily for areas where a clear line of site is not available between the end user and the base station. But Microsoft’s research suggests TVWS could be considerably more versatile as small cell technology is more widely deployed.