Summary
The deployment of femtocells is one among several techniques now becoming available and/or in various stages of R&D to enhance the capacity which users can exploit over wireless access networks when they demand and need it.
Analysis
Femtocells are a promising technique to reduce the costs and enhance the effective capacity which mobile operators can deliver to their customers based on a combination of very small cells and the use of connections to their core networks via fixed broadband links serving the premises in which the femtocells are installed. Other techniques are also entering service and/or being developed to make as much capacity available as possible to users precisely when they demand or need it (in addition of course to deploying networks in additional or new spectrum), including: Smart antenna techniques such as MIMO and beamforming; steerable antennas so that in some environments if usage is temporarily concentrated in some parts of a cell the radio signals can be directed preferentially to those parts; and long term the "Holy Grail" of cognitive radio, which is based on the ability of a network or a wireless node to change its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users. In this ideal cognitive world, users would theoretically be able to make use of whatever frequencies might be available or unused in their locations at any time (subject to safeguards for public safety agencies to commandeer them instantly at times of emergency), thereby greatly reducing the likelihood that at times of peak demand congestion problems would arise. Shannon's Law itself, like the 2nd Law of Thermodynamics, seems to establish an absolute limit within the current state of our scientific knowledge, and indeed one that is to all intents and purposes closely approached by current air interface technologies in terms of spectral efficiency (bits/sec per Hz). As with ideas for perpetual motion machines investors should check that very ambitious revolutionary claims about the performance of new wireless systems do not violate the laws of physics. But the close approach to Shannon's Law does not mean that the performance or capacity available to users is close to its limits, thanks to the kinds of techniques of which examples have just been outlined. The implementation of these techniques, as for femtocells poses major new challenges and questions to network designers and in the case of cognitive radio if that becomes commercially practical, eventually to regulators and policy makers responsible for spectrum management
