w reliably the pilot tone in an ATSC signal can be detected at a range of flux densities. Companies such as Adaptrum, 15 founded by Robert Broderson the cofounder of Atheros, claim that time-domain matched filter techniques working across the whole of the 6 MHz ATSC channel provide robust signal sensing techniques. Motorola have added in geolocation to provide additional protection. Broadcasters, however, remain sceptical. Even if sensing an ATSC signal can be achieved consistently down to low flux densities it is still feasible for devices to be in areas shadowed by buildings or hills - the hidden node effect. If the devices need to work in countries with 15 http://www.adaptrum.com/ Terrestrial Broadcast/Cellular Network Integration DVB TV (with 7 or 8 MHz channel spacing) they need to detect a signal with a much more complex (and by implication hard to detect) pilot symbol structure. Wireless microphones are different - these devices use FM modulation and are inherently low power. The requirement to detect two different types of signals has to be realised in the presence of relatively high incident received energy from other adjacent channels. These signals potentially desensitise the receiver front end, thus potentially compromising the sensing function of the device. 15.10 Transmission Efficiency To date, most technical work has focused on receiver performance parameters but white- space devices are supposed to deliver two-way wireless connectivity. The difficulty here is the bandwidth over which the devices will need to operate. In the US this would be somewhere or anywhere between channels 21 and 51 (512 to 698 MHz) or potentially from channel 2 upwards (54 MHz). The maximum power of these devices is relatively modest, of the order of 100 milliwatts, but difficult to deliver efficiently across these operational bandwidths. Producing a device that would work in other markets, for example Europe, would mean devices would need to work somewhere or anywhere in UHF band 4 extending up to 790 MHz. Designers of ce