Not so long ago Ofcom approved plans for Whitespace Devices to share spectrum with digital TV and wireless microphones. As a relatively new development in the ongoing debate about the future of spectrum, Whitespace Devices are often overlooked or misunderstood. In this week's whiteboard session, we cover what whitespace devices are, why and where they operate, and how they cause some concern for wireless microphone users.

Over the past few weeks, we've explained through various videos how regulators continue to reallocate RF spectrum for use by next generation 4G mobile data services. Whitespace Devices are yet another layer of pressure for the PMSE sector that professional operators need to understand. But first, we must define what exactly white space is from an RF standpoint.

The term white space is used within the context of RF to describe portions of spectrum that are not in use. As wireless microphone operators, we share portions of UHF spectrum with digital TV; the sections in between these TV channels are referred to as white space (demonstrated in the chart below). For many years, users of wireless microphone systems and in-ear monitors have made excellent use of this so-called white space, and we've always operated at a tier below broadcasters.

In the eyes of regulators, these white spaces could be used more efficiently. Let me explain:

If we were to take a snapshot of how much white space is used in London by the PMSE sector at say 5 in the morning, there would likely be little activity. As the day goes on, however, the usage by PMSE goes up as events and broadcasts happen throughout the day. Peak usage is likely between 6 - 10pm as West End shows and concerts take place across the capital. During these peak operation times, white space spectrum is heavily populated with wireless mics and in-ear systems, but at other times of the day these areas are clear for operation. In a nutshell, TV broadcast stays consistent while PMSE usage fluctuates — creating downtime.

To make more efficient use of this so-called white space during periods of downtime, regulators have conducted research into further usage of white space, and this is where Whitespace Devices come in.

What are Whitespace Devices?

There is no concise answer to this question, as there are currently multiple uses for Whitespace Devices. One example is so-called 'super WiFi,' which essentially works in the same way WiFi does today only over much greater distances. Another use of Whitespace devices ties in with a term we increasingly hear called 'The Internet of Things'. This term essentially describes how all the devices we use on a day-to-day basis, from the electricity in our homes to common traffic management systems — and everything in-between — could be interconnected for efficiency and more. Put another way, this is sometimes referred to as machine-to-machine communications, and it will work by using the same white space as wireless microphone and in-ear monitor systems.

In theory, you can see how this seems like a great concept. But hopefully, you can also see how this news is of concern to the PMSE industry. Following the recent news of clearance from 694MHz and up (likely starting from 2019), we've already been left with significantly less space to operate than in previous years. Whitespace Devices are yet another service sharing the remaining UHF spectrum, and given the mission-critical nature of many wireless microphone applications, this development is of great concern.

Here's how it'll work:

Earlier, we briefly touched on the hierarchy or tiers applied to UHF white space, which looks a little something like this:

Tier 1) DTV

Tier 2) PMSE

Tier 3) Whitespace Devices

DTV will continue to have priority over PMSE while Whitespace Devices will operate at a tier below PMSE, which is good news for us. Put simply, Whitespace Devices are not permitted to operate in a clear portion of UHF spectrum if it causes harm to PMSE transmissions.

This three tier system will be managed using a geolocation database. This cloud database will host the licence information of PMSE, and if a Whitespace Device wishes to operate at a given UHF frequency, it must first check the database. If the database can prove that wireless microphones or in-ear monitors are operational, Whitespace Devices will not be permitted to operate. Protection is there, but the key is to licence your systems.

Details on wireless system licencing is a topic for another day. The short answer, however, is that to properly protect yourself from Whitespace Devices, you need to obtain a licence and put yourself on the map.