Saturday, March 06, 2010

Obviating mandatory receiver standards

Two remarks I heard at a meeting of a DC spectrum advisory committee helped me understand that endless debates about radio receiver standards are the result of old fashioned wireless rights definitions. The new generation of rights definitions could render the entire receiver standards topic moot.

First, a mobile phone executive explained to me that his company was forced to develop and install filters in the receiver cabinets used by broadcasters for electronic newsgathering because it had a “statutory obligation to protect” these services, even though they operated in different frequency ranges.

Second, during the meeting the hoary topic of receiver standards was raised again; it’s long-rehearsed problem that shows no sign of being solved. It’s a perennial topic because wireless interference depends as much on the quality of the receiver as the characteristics of the transmitted signal. A transmission that would be ignored by a well-designed receiver could cause severe degradation in a poor (read: cheap) receiver. Transmitters are thus at the mercy of the worst receiver they need to protect.

A statutory obligation to protect effectively gives the protectee a blank check; for example, the protectee can change to a lousy receiver, and force the transmitting licensee to pay for changes (in either their transmitters or the protectee’s receivers) to prevent interference. This is an open-ended transfer of costs from the protectee to the protector.

The protectors thus dream of limiting their downside by having the regulator impose receiver standards on the protectee. If the receiver’s performance can be no worse than some lower limit, there is a limit on the degree of protection the transmitter has to provide.

The problem with mandatory receiver standards is that it gets the regulator into the game of specifying equipment. This is a bad idea, since any choice of parameters (let alone parameter values) enshrines a set of assumptions about receiver design, locks in specific solutions, and obviates innovation that might solve the problem in new ways. Manufacturers have always successfully blocked the introduction of mandatory standards on the basis that they constrain innovation and commercial choice.

An open-ended statutory obligation to protect therefore necessarily leads to futile calls for receiver standards.

One could moot receiver standards by changing how wireless rights are defined. Rather than bearing an open-ended obligation to protect, the transmitter should have an obligation to operate within specific limits on energy delivered into frequencies other than their own. These transmission limits could be chosen to ensure that adjacent receivers are no worse off than they were under an “open-ended obligation to protect” regime. (The “victim” licensee will, though, lose the option value of being able to change their system specification at will.)

The main benefit is certainty: the recipient of a license will know at the time of issue what kind of protection they’ll have to provide. The cellular company mentioned above didn’t find out until after the auction how much work they would have to do to protect broadcasters since nobody (including the FCC) understood how lousy the broadcasters’ receivers were.

The regulatory mechanisms for doing this are well known, and have been implemented; they include the “space-centric” licensing approach used in Australia (PDF), and Spectrum Usage Rights (SURs) in the UK.

Moving to new rights regimes is a challenging; Ofcom’s progress has been slow. One of the main difficulties is that licensees for new allocations prefer to do things the old, known, way. One of the supposed drawbacks of SURs is that the benefits of certainty seem to accrue a licensee’s neighbor, rather than the new licensee themselves. However, removing the unlimited downside in an open-ended obligation to protect adjacent operations should prove attractive. The whining will now come from the neighbors who will lose their blank check; careful definition of the licensee’s cross-channel interference limits to maintain the status quo should take the sting out of the transition.

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