llular phones know how hard it is to deliver efficient RF power amplifiers at lower frequencies over extended operational bandwidths. Getting an RF power amplifier to work efficiently across 40 MHz at 800 MHz is challenging, let alone 100 MHz or more at 600 MHz. As a comparison, the widest cellular bandwidth as a percentage of centre frequency is presently GSM 1800. 75 MHz at a centre frequency of 1747 MHz is equivalent to 4.3%. The 80-MHz ISM band at 2.4 GHz is 3.3%. White-space devices could be of the order of thirty to 40% - an order of magnitude greater. 15.11 Scale Economy Efficiency One solution would be for white-space devices to be market specific that would mean white- space devices for the US market (Region 2) and rebanded devices for Region 1 (Europe) and Region 3 (Asia). However, this would make it impossible to achieve sufficient scale economy. This would be particularly true if only deployed in the US. By 2014 the US will constitute less than 10% of the global market for cellular devices. RF development today is typically amortised over hundreds of millions of devices. Such volumes would be inconceivable from the US white-space market alone. 15.12 Signalling Efficiency White-space devices will have to measure and continuously remeasure bandwidth occupancy and share these measurements with other devices or access points in the network. The IEEE presently has a working group specifying these protocols but essentially this is a complex measurement process. Making Telecoms Work This means that the devices will not be spectrally efficient and more important from a users perspective will not be power efficient irrespective of the network topology adopted. The use of mesh-network topologies for example would result in particularly poor spectral and power efficiency. White-space devices would therefore be likely to have much poorer duty cycles than equivalent cellular devices. 15.13 Power Efficiency Loss as a Result of a Need for Wide Dynamic Range The need for a wide dynamic range in the receiver front end