Anyone considering deploying a TV White Space network will have a problem in mind which they hope TVWS will be able to solve. We have been helping a variety of companies use TVWS to solve such problems, and would like to share some of our experience. This post covers some high-level considerations about whether TVWS is a good fit for your problem; Part 2 covers one of these considerations in greater detail.
What is TV White Space?
TV White Space is dynamic use of prime radio spectrum freed up by the UK’s Digital Television switchover. Unlike licensed spectrum (e.g. 4G auctions), TVWS does not require the operator to pay Ofcom for a licence and can be used on an ad-hoc basis by anyone with the right equipment. Its range, penetration, and bandwidth characteristics compare very favourably to other unlicensed bands, making it an attractive option for a variety of use-cases:
1. Rural Broadband
TVWS is excellent for reaching areas which are hard to reach with fibre. While the bandwidth can’t match fibre, it is still attractive to fill gaps in fibre coverage as part of a hybrid solution. A Master TVWS radio will have a backhaul connection (fibre, microwave, etc.) which it will ‘share’ over TVWS to Slave devices at the customer locations.
2. High-Throughput IoT Sensor Networks and Intranets
Most IoT radio solutions have tight constraints on data payload size and duty cycle. TVWS is well suited to wide-area sensor networks with high data requirements – including live video feeds. This is true of networks which upload data to the internet as well as networks which only share data between themselves (e.g. local video uplink).
We operate our own TVWS network supporting the Oxford Flood Network IoT project.
3. Super Wi-fi
TVWS devices are moving towards being consumer-grade; much like Wi-fi in the early 2000s there are now USB dongles available. Ordinary (2.4GHz & 5GHz) Wi-fi has a maximum range of 100m; with TVWS this is more like 1km.
TVWS has a maximum power of 36dBm/8MHz in the range 470MHz-790MHz. This translates to a usable coverage range up to 25km, or 4km at rooftop heights, giving tens of Mbps (up to 100Mbps by bonding multiple channels).
What Do You Need?
- Internet connectivity. Aside from the obvious need for backhaul for e.g. Rural Broadband networks, TVWS Master devices must periodically contact a White Space Database (WSDB) such as Nominet’s to request spectrum. Networks which don’t have backhaul can potentially use 2G for this low-throughput task.
- TV White Space Devices. We can put you in touch with several manufacturers of TVWS radio devices. To operate in the UK these must be ETSI certified; for customer deployments other certification such as CE marks may also be needed.
- TV White Space Database. Nominet operate an Ofcom-qualified WSDB which can grant your radios permission to transmit; contact us to arrange WSDB access.
- RF Planning. All the usual considerations apply when planning the locations of your devices (radio propagation modelling, terrain, antenna directionality, receiver sensitivity etc.) – along with additional constraints imposed by TVWS availability. Different channels are available at different maximum powers at different locations. As an R&D group we can provide you with free custom reports taking all these factors into account, or we can provide TVWS channel/power availability data to plug into your own planning tools. Part 2 goes into detail on the TVWS availability.