Friday, September 02, 2011

TV white space databases: A bad idea for developing countries

Now that TV white space rulemakings are in the can in the US and UK, proponents will be pitching the technology to any government that’ll listen, e.g. at the Internet Governance Forum meeting to be held in Nairobi on 27-30 September.

It’s understandable: the more widespread white space database rules, the larger device volumes will be, and thus the lower the equipment cost, leading to wider adoption – a positive feedback loop. However, white space database technology is unnecessary in many countries, particularly developing ones.

Yet it verges on dodgy ethics for companies to hype this technology to countries that don’t need it, particularly since there’s a better solution: dedicating part of the TV frequencies that are freed as a result of the transition to digital TV (the “Digital Dividend”) to unlicensed operation, without the white space bells and whistles.

White space operation is only necessary where the TV frequency bands are filled with many TV stations with many gaps between them. In many countries there are relatively few terrestrial broadcast stations, because there isn’t the capacity to generate many channels of content, and/or because large geographies are more efficiently covered by satellite transmission than a network ground-based towers. Countries that have waited to make the transition to digital TV can also easily opt for technology also allows a TV transmission to use the same frequency on all towers (Single Frequency Networks), allowing the same number of TV programs to be broadcast using fewer channels. Ensuring that all transmitters in an area use the same tower, and other techniques being discussed as part of, would allow broadcasts to be arranged with fewer white spaces, leading to an even larger digital dividend of freed up TV frequencies that can be used for data networks.

It’s worth remembering that the database approach was adopted only as Plan C, after Plan A (a single, contiguous band dedicated unlicensed) and Plan B (each device using its own sensors to determine vacant channels) had failed. Implementing a database solution requires not only collecting and managing data about TV (and other primary) transmitters in a central location, but also managing the on-line service itself. That’s a heavy overhead in places where limited institutional capacity could be better used in other ways. White space databases are also more liable to be used for extortion and excessive social control than a conventional unlicensed band.

The Better Alternative

Places with few broadcast TV channels should forget about white spaces, particularly the database flavor, [1] and simply divide their Digital Dividend into three chunks: one third for licensed, one third for unlicensed, and one third held in reserve for later use (e.g. licensed or unlicensed, depending on which one turned out to be more useful in a particular country).

Countries like South Africa are in the midst of deciding what to do with their Digital Dividend; the cellular companies are hungry, and unlicensed isn’t discussed much if at all. Decisions made now will have long-lasting consequences.

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[1]   If a country has remaining white spaces where it would like to authorize unlicensed use, a country should consider using spectrum sensing techniques. A database is, in a way, just a way to sense spectrum, i.e. for a device to know which channels are not being used for TV. Device-based spectrum sensing proved less accurate than databases in FCC testing, but other countries might consider this an acceptable price to pay in their circumstances.

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