OFCOM: Wi-FI anche nell'FM con la radio cognitiva

Mi era sfuggita, due settimane fa, la dichiarazione con cui Ed Richards, chief executive del regolatore britannico OFCOM, ha per la prima volta accennato alla possibilità di utilizzare le tecnologie della radio cognitiva dei cosiddetti "whitespaces" (i buchi frequenziali non altrimenti impegnati) anche nella banda FM lasciata parzialmente libera da un eventuale processo di spegnimento delle stazioni analogiche. E' una dichiarazione molto importante perché finora non era mai successo che un "politico" del radiospettro ipotizzasse uno scenario di assegnamento di frequenze comprese tra gli 88 e i 108 MHz per servizi come la connettività a Internet senza fili. Gli attuali sistemi di comunicazione interattiva digitale occupano porzioni di spettro piuttosto larghe, che trasportate nella piccola finestra di 20 MHz dell'attuale FM si mangerebbero il grosso dello spazio disponibile.

Notabene, Richards non ha affatto voluto dire che a partire da una certa data le frequenze FM verranno assegnate agli operatori di telecomunicazioni per erogare servizi non broadcast (oltretutto saranno frequenze molto pregiate perché a 100 MHz i segnali radio si ricevono meglio all'interno delle case e potrebbero aiutarci a rimediare a molte situazioni di digital divide di zone rurali e montagnose). La radio cognitiva consentirebbe piuttosto di impegnare queste risorse in modo intelligente, occupando solo gli spazi lasciati effettivamente liberi dalle stazioni broadcast a carattere locale che sopravviveranno allo switch-over (peraltro non ancora ufficialmente deciso). Secondo Richards sarebbe addirittura un buon modo per evitare che gli stessi spazi bianchi finessero per essere illegalmente occupati da pirati e hacker. Sarebbe però un precedente importante, perché fino a oggi siamo stati abituati a pensare allo spettro delle radiofrequenze come a un insieme di slot rigidamente assegnati a determinati servizi, con precise regole anti-interferenziali. La radio cognitiva cambierebbe radicalmente questo scenario e il risultato è che comunque l'FM così come la conosciamo attualmente perde molta della sua sacralità. Un fatto su cui editori radiofonici e ascoltatori dovranno cominciare prima o poi a ragionare seriamente.

Ofcom considers future of FM radio band

July 6, 2011

Ofcom today proposed an innovative new use for the airwaves that will be freed up following the UK’s switch from analogue to digital radio.

Speaking at the Radio Centre members’ conference today, Ofcom Chief Executive, Ed Richards, identified White Space Devices as potential new users of the freed up FM radio airwaves. These devices could use these frequencies to deliver innovative applications such as mobile broadband in very sparsely populated areas.

The technology works by identifying unoccupied radio waves called “white spaces” to transmit and receive wireless signals.

Compared with other forms of wireless technology, such as Bluetooth and Wi-Fi, White Space Devices are being designed to use a much wider range of frequencies, including the lower frequencies that have traditionally been reserved for TV and radio.

Ofcom has been leading the way in Europe to develop a system that would allow these devices to work without interfering with other users of spectrum. To date, this has focused on using the white spaces between digital TV channels. However, in practice this technology could also work in the FM radio band.

Signals at these frequencies travel further and more easily through walls.

Ed Richards said: “We believe that any release of new spectrum has great potential to enable innovation and growth in new applications and services.”

“Spectrum is a resource that is in huge demand, fuelled by the recent explosion in smart phones and other wireless technologies. However there is only a limited amount of it to go around, which means we need to start thinking more creatively about how it is used. White Space Devices could offer an effective solution.”

Digital radio switchover

It is anticipated that all large scale radio stations will migrate to digital and eventually cease to broadcast on analogue FM radio. Smaller stations are expected to remain on FM.

This is expected to free up as much as 50% of the capacity currently used to deliver FM radio services and has raised questions as to what this capacity will be used for.

“Our first principle has to be that any future use of the FM band is an efficient use of radio spectrum,” said Ed Richards.

“There must be certainty for smaller and community stations, that do not move across to DAB. These will continue to play their important role, and FM is an appropriate technology for the scale at which they operate.”

Protecting the radio industry

Ed Richards explained that White Space Devices offered a solution that could safeguard the interests of the radio industry by making it less likely that it was backfilled with new commercial and pirate radio stations.

“White Space Devices offer a creative solution that would not only use spectrum to its full capacity, but would also work along side existing smaller FM radio stations. This could be done without causing interference and without any commercial conflict.”

“This approach not only would spur on technological innovation but it could also further restrict the opportunity for pirates to fill in the gaps caused by careful spectrum planning.”

White space technology

On 9 November 2010, Ofcom launched a consultation on the processes needed to successfully launch the technology and how new devices will be made available to consumers without the need for a licence. This was based on using white spaces between digital TV channels, however it could also be extended to use white spaces in the FM radio band. Ofcom expects to publish a statement concluding its thinking in the area of digital TV white spaces shortly.

White space database

It is important that white space devices do not interfere with other wireless technologies that share these frequencies. The solution is for devices to do this by consulting a “geolocation database” that contains live information about which frequencies are free to use at their current location.

Ofcom expects to make it possible for interested companies to host such databases.

How the technology will work

Some white space applications will work in a similar way to Wi-Fi, which uses a wireless router to send and receive information to other wireless devices. A key difference is that the white space router or base station will first need to consult a list of databases hosted online. It will describe its location and device characteristics to one of these databases on a regular basis. The database will then return details of the frequencies and power levels the router is allowed to use so that it does not interfere with other devices operating in its vicinity.