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White space devices go-ahead raises PMSE doubts

Ofcom’s recent decision to green-light the use of WSDs should be treated with caution, BEIRG’s Tuomo Tolonen tells Kevin Hilton

The UK broadcasting and production sector knew it was coming but there was still some annoyance at Ofcom approving plans for white space devices to share radio spectrum with digital terrestrial television (DTT) and wireless microphone users.

In its announcement of 12 February the regulator views this as “offering new wireless applications to benefit consumers and businesses” and follows what it calls a series of successful industry trials.

Provision for white space devices (WSD) was proposed in the Digital Dividend consultation of 2006, which led to the 800MHz band being cleared and the auction of analogue TV spectrum for 4G and other mobile telecom use. As a result PMSE (Programme Makers and Special Events) users were moved to new frequencies, with the nationwide channel 69 being replaced by channel 38. Industry bodies lobbied successfully for Ofcom to recognise the need to provide enough spectrum for wireless microphones, in-ear monitors (IEMs) and general communications but there is still the concern that there are now not enough frequencies to cover large productions.

The thought of possible interference from unlicensed devices operating in close proximity has added to these concerns. In the document Implementing TV White Spaces, Ofcom makes a point of responding to comments received from the PMSE and broadcast sectors during the consulation period by incorporating stricter operational guideslines to prevent the new technology interfering with transmissions or productions.

Ofcom says giving the go-ahead for WSD is a response to the increasing number of wireless devices being used, which has placed greater demand on radio spectrum. Because of this the decision was taken to give access to unused portions of spectrum in the 470–790MHz range – those not being used by either DTT or PMSE – through “dynamic sharing controlled by a spectrum database”. These TV white spaces (TVWS) will be available without the need for a licence to devices that meet a minimum technical specification. Part of this includes the ability for units to recognise where they are. This capability will be used in conjunction with a database to identify existing services, thereby ensuring different devices can run simultaneously.

Tests of WSDs began in June 2014 and were completed in November, with coexistence testing from January to December that year. Among the applications are internet connectivity for ships in the Orkney Islands, streamed video coverage of meerkats and otters at London Zoo and a ‘machine-to-machine’ flood defence network in Oxfordshire.

The white spaces are in the UHF TV band and are made possible by gaps between DTT multiplexes to prevent close proximity of high power transmissions. Ofcom says the rules for coexistence are “sufficiently conservative” to make for a low probablity of disruptive interference but that “tools and processes” are available to deal with problems; furthermore, “a number of coincidences” would have to occur for PSME users of channel 38 to experience a siutation similar to its “stress tests”.

The regulator has been seen as in favour of rolling out WSD and its acting chief executive, Steve Unger, commented on giving the go-ahead, “This decision helps ensure the UK takes a leading role in the development of innovative new wireless technology. It is also an important step in helping the UK’s wireless infrastructure evolve effectively and efficiently.”

The PMSE community is less enthusiastic. Tuomo Tolonen, manager of the pro-audio group at Shure Distribution UK (pictured at ISE 2015) and a member of the steering committee of lobby organisation BEIRG (British Entertainment Industry Radio Group), says although the move was expected it is still not welcome. “It highlights the importance of the UHF band but the negative is that RF is already congested since we lost 800MHz,” he comments. “On the plus side the position of PMSE was recognised but even with the database there is the potential for devices to be hacked, so you won’t know where they are. The thought of unlicensed systems leaves me feeling a little uncomfortable.”

At the ISE show last month, Tolonen spearheaded Shure Distribution UK’s Losing Your Voice campaign, which aims to better inform both professional and semi-professional users of RF technology about the challenges to the unhindered use of wireless microphone systems as a result of continued UHF spectrum allocation to the mobile communications and data industries.