Technology Neutral Spectrum Assignment – a nice concept but is it realistic ?

We learn from Economics theory that if you want to trade goods effectively, these shall be as general as possible, usable by anyone an preferably for many purposes. In this way we attract a large crowd of willing buyers and the market becomes an effective instrument to share these goods.  However, if the goods are very specific (like left lady’s high-heels shoes in pink, size 49) the demand is very limited and few buyers will show up to facilitate effective trading.

This exactly the concept behind technology neutral spectrum licensing .. instead of prescribing in detail when, where and how to use the spectrum, the new policy (e.g. “WAPECS“) is to provide a “block edge mask”,  restricting what emission are allowed outside the allocated band. Any system conformant with these rules will be allowed and the market for licenses is now large.

What’s the catch ? Well, its what in the business is called “Legacy Equipment”, i.e. anything that is out there before these new regulations are put into place. We have already numerous examples of interference problems. Air-port radars, GSM-R (railway) systems, TV-receivers are facing interference from new LTE/UMTS systems that are put into operation in neighboring bands. Is something wrong with these systems ? No. Are they violating the spectrum mask rules ? Not likely. Would the problems go away with perfect new equipment? Unfortunately not.

You see, most of this equipments was not designed to have a LTE or UMTS base station next door.  The were designed with the implicit assumption that the neighboring band was empty or used in a very specific way. In this way receiver designers could cut some corners and save a few bucks in production cost. So it’s clear where to put the blame. But will the airport-radar uses, the television set manufacturers or railways modify their systems ?  Not likely. There seems to be “squatters rights” in the spectrum domain – the guys that where there first (and have significant investments made) are protected and the new users have to modify their equipment, restrict their use or even pay for the modification of legacy equipment. In Sweden a recent study show that using UMTS in the 900 MHz band is OK as long a you stay a kilometer away from the nearest railroad (i.e. where the highest population density are likely to be).  If a different system is used LTE, GSM there may be different restrictions.  Instead of having a technology neutral spectrum, specific rules apply for each technology and exact how close to the band edge the spectrum chunk is located. Will the bidders in a spectrum auction need to take this into account – yes of course, with a significantly lower valuation as consequence.

So Tech Neutrality is a nice concept but difficult in practice. It again exposes the shortcomings of our current paradigm of transmitter licensing. Here (and in many similar cases)  its the receivers that cause the problems.  The concept of Spectrum Usage Rights is a step in the right direction, but not a solution to these problems.

Jens Zander

About Jens Zander

Professor Jens Zander is professor in Radio Communication Systems at the Royal Institute of Technology, Stockholm, Sweden. He has been among the few in Swedens Ny Teknik magazine's annual list of influential people in ICT that have been given the epithet “Mobile Guru”. He is one of the leading researchers in mobile communication and is the Scientific director of the industry/academia collaboration center Wireless@KTH. His research group focuses on three main areas – the efficient and scalable use of the radio frequency spectrum, economic aspects of mobile systems and application and energy efficiency in future wireless infrastructures.
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