How small are “small” cells?

This is a first “live” report from Globecom 2012 in Anaheim, CA. Todays topic at the Broadband Wireless Access Workshop was small cells. Sampath Rangarajan from NEC (USA) gave an interesting presentation regarding the need for “small cells”. Based on (optimistic) assumptions availability of spectrum and advances in the PHY-layer domain, and the assumption that there cannot be significantly larger numbers of macro base stations, he calculated that up 84% of the traffic projected by Cisco has to be “offloaded”. I had no problem to agreeing with that, however I was somewhat surprised that the solution was outdoor micro/pico, beefed up with centralized RRM and 60 GHz backhaul – a solution that is not entirely new (discussed already in the 90’s , e.g. EU FP4 FRAMES) . Since the majority of the traffic is likely to be generated indoor I wonder if this really is good solution. There are several reasons for my doubt- the energy and cost parameters point the wrong way: Outdoor micro/pico have to “blast through the wall” to provide decent data rates indoor, putting them at severe disadvantage to the indoor solutions. Outdoor micro/pico solutions in a sense combine the disadvantages of macro deployment – outdoor rugged equipment and careful planning is needed and backhaul is a significant problem. Since micro/pico access would need high power at low antenna elevations for indoor coverage, we would experience, not only high power consumption but also potentially get health hazard problems. Indoor systems have neither of these problems (“existing” indoor backhaul, consumer grade equipment, low power) and if the efficiency is not high enough, throw additional Access Point. From a cost perspective in many cases the macro-cell + indoor macro is likely to be the best solution. One barrier is certainly that indoor systems are not necessarily deployed by (public) operators so the incentive of the latter to drive low cost indoor solutions is (understandably) limited. Let’s hope that this can be resolved .. otherwise there will certainly be a cap on the exponential growth of traffic very soon – the customers will simply not be able to afford more data.

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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