Ofcom publishes regulations for 'TV whitespace' tech

Ofcom, the Super Regulator, (in December) published the new regulations for TV Whitespace technology which came into force on the 31st December 2015 allowing equipment that meets the regulations to operate on a license exempt basis.

In the new digital era of terrestrial TV, there are digital multiplexes across the UK, these multiplexes use different channels, so neighbouring transmitters don't interfere with each other, which means there is a lot of potentially unused spectrum in a particular area. Multiplex sit in the UHF band which covers 470 - 790 MHz.

In order to avoid interference with existing (licensed) spectrum users, devices will need to communicate with databases which apply rules, set by Ofcom, to put limits on the power levels and frequencies at which devices can operate. There is also a 'kill switch' function whereby the database can tell a device to stop operating completely if interference is found to be occurring.

The UHF TV band is currently allocated for use by Digital Terrestrial Television (DTT) broadcasting and Programme Making and Special Events (PMSE). Currently, Freeview TV channels are broadcast using up to ten multiplexes. Each multiplex requires an 8 MHz channel. Multiplexes are transmitted at different frequency channels across the country in the frequency range 470 to 790MHz.

Whilst a total of 32 channels each 8 MHz wide are reserved for DTT in the UK, normally only one channel per multiplex is used at any given location. In other words, the majority of channels are unused for DTT transmission at any given location. This is required because high-power TV broadcasts using the same frequency need geographic separation between their coverage areas to avoid interference.

The channels that are not used by DTT at any given location can be used by lower- power devices on an opportunistic basis. This opportunistic access to interleaved spectrum is not new. Programme making and special events (PMSE) equipment such as radio microphones and audio devices have been exploiting the interleaved spectrum for a number of years, and Ofcom issues more than 50,000 assignments annually for this type of use.

Ofcom refer to the spectrum that is left over by DTT (including local TV) and PMSE use as TV White Spaces (TVWS). By this we mean the combination of locations and frequencies in the UHF TV band that can be used by new users, operating in accordance with technical parameters that ensure that there is a low probability of harmful interference to DTT reception, PMSE usage or services above and below the band.

The following organisations have signed contracts and completed qualification to run the white space databases (WSDB): -

• Fairspectrum Oy
• Nominet UK
• Sony Europe Limited
• Spectrum Bridge Incorporated

The 'master' devices that talk to the databases should report their height, if they don't the database will use a use conservative default values for the purpose of calculation of operational parameters i.e. it will use height values that would result in operational parameters that are equal or more restrictive than they would be had the device reported its height.

Though the regulations do not specify an update time (for master devices to communicate to the databases), Ofcom has stated a maximum time of 15 minutes which strikes an appropriate balance between the need to be able to act quickly in the event of interference and limiting the practical burden on databases of maintaining frequent communications with potentially large numbers of devices. This may be revised if found to be unsuitable.

The WSD Regulations apply to the United Kingdom and the Isle of Man. They do not extend to the Channel Islands.

A master device is a device which is capable of communicating with and obtaining operational parameters from a database for the purpose of transmitting within the frequency band 470 MHz to 790 MHz.

A slave device is a device which is capable of transmitting within the frequency band 470 MHz to 790 MHz after receiving slave operational parameters from a master device.

Type A equipment as equipment which has an integral antenna, a dedicated antenna or an external antenna11 and is intended for fixed location use only.

Type B equipment as equipment which has a dedicated antenna or an integral antenna and is not intended for fixed location use.

WSDs must not be used airborne.

WSDs must be configured in such a way that a user is unable to input, reconfigure or alter any technical or operational settings or features of a device in a way which (i) would alter the technical characteristics of the device which are communicated to a database (this includes the master and slave device characteristics), or (ii) would cause the device to operate other than in accordance with master operational parameters or slave operational parameters, as applicable. An example of (ii) would be the antenna gain. If this parameter is set to be smaller than the actual gain of the antenna, then the device could radiate at a higher level than the limit communicated by the WSDB.

A master device:

• must be able to determine its location
• must provide device parameters (defined now as its ‘master device characteristics’) to a database, in order to obtain operational parameters from the database. The device parameters include the location and the technical characteristics of the device listed below. The operational parameters indicate to the device the channels and power levels that it can use, together with other constraints.
• must only transmit in the UHF TV band after requesting and receiving operational parameters from, and in accordance with, operational parameters provided by a database
• must apply the simultaneous operation power restriction (described at paragraph 3.23 above), if it operates on more than one DTT channel simultaneously and the master operational parameters indicate that this restriction applies
• must report back to the database the channels and powers that the WSD intends to use – the channel usage parameters – and operate within those channels and powers.

In addition, where its operational parameters stop being valid, a master device must tell slave devices that are connected to it to stop transmitting and must stop transmitting itself. The operational parameters stop being valid if:

• a database instructs the master device that the parameters are not valid
• a master device cannot verify, according to the update procedure, that the operational parameters are valid.

In order to support more WSDBs Ofcom also intend to publish on our website a machine-readable version of that list on a website hosted by Ofcom so that it can be selected by a WSD through a process known as “database discovery”. Ofcom would expect that list to include those database operators which have informed Ofcom that they are ready to start providing services to white space devices.

It is interesting that Sony is moving into this space, which probably means they will start producing equipment that uses white space technology for short range communication, such as say a PS4 to its peripherals.

Europa publish Radio Spectrum report on 700MHz spectrum

Pascal Lamy has presented his report to the European Commission on the future of the UKF (700MHz spectrum).

In summary the report proposes: -

The 700 MHz band (694-790 MHz) is currently used for Digital Terrestrial Television broadcasts and Wireless microphones, this spectrum to be re-alloacted to wireless broadband by 2020 (with a +/- 2 year variance).

The spectrum below 700MHz (470-694 MHz) should be maintained for DTT broadcasts and should be given regulatory stability.

The Program Making and Special Events (PMSE) spectrum should be moved to the 800MHz band (823-832 MHz) and 1.8 GHz (1785-1805 MHz).

This will mean TV sets/etc will need a major retune in around 2018 to ensure reception and also new broadcast technologies (MPEG-4 and DVB-T2 - which is used by Freeview HD, but not all current sets/etc will support it).

It's likely PMSE will require new equipment (especially for radio microphones), but at least manufacturers have about 6 years to do this.

Ofcom consults on whitespace co-existance

Ofcom, the Super regulator that handles radio spectrum as part of its remit, is holding a consultation on the coexistence of whitespace devices.

Whitespace is the spectrum that is unused in certain areas due to geographic transmission systems that can not overlap and in this case relates to the UHF TV channels (470 MHz to 790 MHz). As there are multiple transmitters across the UK, adjacent transmitters can not operate in the same frequency bands (especially for digital TV) or the transmitters would interfere with each other.

This leads to large chunks of the UHF spectrum not being used in a particular geographic zone, which could be used for other purposes (as long as it was low power and didn't reach neighbouring areas).

Current plans are that whitespace devices will monitor what bands are in use (by listening to those frequencies) and thus not use them, in the UK they must also contact a central database, report their location and the database will specify what frequencies are available and what power they can transmit at.

There are other services that can also be interfered with such as program making and special events (PMSE) - things like outside broadcast units which can use some of the spectrum for remote TV cameras and such like, which also have to be catered for.

Ofcom have already said they will allow whitespace use on a license exempt basis, but they also must ensure that there will be no harmful interference to digital terrestrial television (DTT) and PMSE.

Whitespace technology is new and thus there is some uncertainty on how whitespace devices may interfere with DTT or PMSE services. However Ofcom doesn't want to overly constrain whitespace use such that large amounts of spectrum go unused, or that power levels/etc are so restrictive that reaching any sizeable population is unrealistic.

Ofcom will currently err on the side of caution and setting parameters that can be relaxed in future. Later this year there will be a set of pilot trials across the UK with a number of service providers where the increased power levels can be used for limited periods of time to ensure interference doesn't occur. The trials (and stakeholder consultations) will continue until Summer 2014 and will help Ofcom set the parameters for future national whitespace roll-outs starting in Q3 2014.

Ofcom has set the parameters and algorithms for use in trials to minimise the effects on

• Digital Terrestrial Television services
• licensed users of equipment for Programme Making and Special Events
• services above and below the UHF TV band.

Ofcom have also noted that whitespace availability will vary in areas across the UK i.e. London has relatively low DTT issues with whitespace use while Glasgow has much less spectrum available, however Glasgow has very little PMSE use while in central London (and areas like Wembley Stadium) there is a large amount of use.

Though it is yet early days, whitespace spectrum should allow high bandwidth services with good propagation characteristics (coverage) which could be used to provide mobile network operator capacity off-loading, broadband and machine-to-machine (M2M) services.

Companies such as Neul (a CSR - now Samsung spin-off) are betting their futures on whitespace.

The consultation closes on 15 November 2013 and stakeholders can respond on-line.

Neul introduce witespace single chip solution

Neul, the spin off from Cambridge Silicon Radio (CSR), today announced a single chip solution for whitespace use based on their weightless standard.

The ASIC known as Iceni works across the whole UHF band (470 – 790MHz) and is easy to interface to micro-controllers and CPUs such as the ARM M3 making it ideal for M2M solutions. The chip is also small, low power and low temperature.

It can operate using both 6 or 8 MHz channels and uses daptive digital modulation schemes and error correction methods can be selected according to the trade-off between data rate and range required for a given application as well as supporting over-the-air encryption. The chip also supports programmable IO allowing it to control external parts of the solution including the RF stage and thus the transmit power (which is essential to meet any local regulations).

Neul currently dominate the whitespace arena and the technology is well suited to M2M applications - probably more sure than cellular based systems using 2G or 3G. The Neul solution can support thousands (if not more) end points and support large distances between devices (the greater the distance, the lower the bandwidth, but this generally isn't an issue for M2M installations).

Neul are conducting trials in the UK as well as other countries, however although Ofcom has made whitespace devices license exempt, it mandates a central database that contains geo-information about locations, frequencies supported and power levels. Unfortunately Ofcom have not yet implemented the central database solution.

Ofcom consults on whitespace use

Ofcom the Super regulator has published a consultation on the use of whitespace frequencies.

Whitespace is radio spectrum (generally in the Digital Terrestrial Television [DTT] and Program Making and Special Events [PMSE] bands) in the UHF TV bands (470MHz to 790MHz) that isn't used in a particular area. This is because adjacent TV transmitters cant use the same radio frequencies, so there are geographic areas where certain spectrum is available, but those frequencies will be used elsewhere in the UK.

As certain frequencies are available in certain areas, these could be used (in lower power) by other devices such that they wont interfere with their use in neighbouring areas. In order for that to work, the devices (or central transmitter) will have to know where it is and how much power it can transmit and on what frequencies such that interference wont occur.

There are various uses for whitespace spectrum such as rural broadband or hotspot connectivity. Here the central transmitter would have to query the central database and CPE equipment would get transmit power and frequency use from the central transmitter.

Whitespace could also be used for in-home or M2M applications and in this case the central router (which would be connected to the Internet) would make the database queries and the rest of the in-home/M2M equipment would get the power/frequency information from the central router.

Ofcom is proposing making whitespace devices license except, though they will have to contact a central database and pass back their location and thus be given allowable frequencies and their power constraints.

As part of the consultation Ofcom has specified the types of queries and responses, but not how they're implemented as this would be down to the market to implement.

The full statement (PDF) is available on-line and the stakeholders can also respond on-line. The consultation closes on the 10 January 2013.