Addressing the Spectrum Crunch

February 6, 2014 | 23:01
Addressing the Spectrum Crunch
Addressing the Spectrum Crunch
The rise of wireless technologies calls for a transformation of spectrum exploitation. A new publication TV White Spaces, A Pragmatic Approach explores technological solutions and policy alternatives.

The explosion of wireless communication technologies generates an increasing need for spectrum access. Without changes to current spectrum management schemes and radio technologies enabling dynamic spectrum access we're inevitably heading toward a shortage of available bands.

In a recent publication TV White Spaces, A Pragmatic Approach [free download] editors Ermanno Pietrosemoli and Marco Zennaro collected 14 articles, each addressing the spectrum crunch from a different angle. Combined the articles make a strong case for exploiting TV white spaces to alleviate the shortage in the near future and dynamic spectrum access as the long term solution.

In the Preface professor Eric Brewer of the University of California at Berkeley explains the limitations of the status quo. Governments claim authority over the radio spectrum and auction off portions for astronomical sums. Big companies who can afford these licenses leave much of it unused, especially in rural areas where investing in coverage isn't profitable. These same areas are underserved with regards to Internet access because a wired infrastructure is, again, too expensive. Wireless Internet is much cheaper to deploy but for that spectrum access is needed.

Technological advances like cognitive radio and smart antenna's will make it possible to use the spectrum without interfering with the incumbent license holder. Experiments to that effect are undertaken in TV White Spaces. These are portions of the spectrum deliberately left unoccupied to prevent interference between TV channels. 'And', Brewer writes, 'as technology continues its inevitable rise, our ability to aggressively share spectrum will only improve'.

In the first chapter Robert Horvitz of the Open Spectrum Foundation covers the history of spectrum management and warns against a proposed future alternative: geo-database management.

The radio spectrum is the most strictly regulated of all communication media: 'everything is forbidden which is not explicitly authorized by your country's government', writes Horvitz. The origin of this dubious honor can be traced back to three factors shaping the emergent technology in the early twentieth century.

First of all, radio communications were considered a matter of national security. It enabled governments for the first time to communicate with navy vessels at sea. Regulation was a means to prevent eaves dropping and interference. Secondly, the fear for interference was justified to a certain extend. The immaturity of the technology meant that improper use by an operator could create chaos on the air. And lastly, radio pioneer Guglielmo Marconi claimed world wide patents which entitled him to a monopoly on the use of spectrum. Not at all happy with that idea governments 'pushed back with a treaty establishing national sovereignty over the radio spectrum, declaring that only governments had the right to regulate and authorize spectrum use', says Horvitz.

Strict regulation is detriment to innovation, argues Horvitz. As soon as government takes a step back new technologies flourish. In 1938 the American Federal Communications Commission (FCC) exempted certain short range communication devices from licensing. In itself a revolutionary step that led to novel devices like baby monitors and wireless speakers. However, the limiting factor was that manufacturers had to apply for license exemption for each new type of device. In 1989 the process of individual approval was dropped and replaced by a general compliance to a broad set of technical specifications. The result was a boom in radio-enabled technologies of which WiFi and RFID are the best known.

Horvitz is a proponent of the open spectrum approach: the move toward a license-free operation of radio waves. To get there a more dynamic use of the spectrum is needed. Two different schemes are currently being explored to enable spectrum sharing: geo-database management and spectrum monitoring. The first involves a geographic database which tells radio's which frequencies they can use, the second relies on smart radio's which scan for free channels.

Horvitz warns that a government managed database lookup will leave us with a spectrum even more regulated than currently is the case. Devices have to seek reauthorization at regular intervals in order to continue to operate. Horvitz points to the state-ordered Internet blackouts in Egypt and Syria to illustrate the danger of such a set up. Smart radio's on the other hand will give rise to a true open spectrum. They can operate entirely on their own merits without external control.

There are many more interesting articles in the free publication. Kiely Cronin of Carlson Wireless Technologies describes the weightless standard. A protocol specifically designed for machine-to-machine communication within white spaces. The 1.0 version of the standard was completed in April 2013.

Marco Zennaro and Andrés Arcia-Moret present a manual on how to make low cost portable spectrum analyzers to locate white spaces. Offering two different devices one based on the Raspberry Pi the other on an Arduino, the authors hope to contribute to a wider analyses of spectrum occupancy. Especially in less wealthy locations where the cost of professional equipment can be too high.

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