 in system for Scandinavian airlines, a mental-health facility application and a smart-city system. 11 The smart-city application is based on a sensor board that measures noise pollution (real-time noise maps), dust quantities, (real-time dust maps) the structural health of buildings, bridges and road, garbage levels (only empty bins when they are full), gas monitoring, environmental monitoring (CO2 and NO2) radiation detection and smart parking. The sensor nodes communicate with the network using ZigBee 12 radio links mainly ensure that sensor devices have a sufficiently low energy requirement to be able to be powered from solar power or a battery lasting several years or more. And actually this is quite a nice example of radio hardware being developed with an application appropriate protocol stack with a radio range up to 12 kilometres using ZigBee, 10 http://www.rfidjournal.com/article/articleview/8553 11 http://www.libelium.com/ 12 http://www.ZigBee.org/. Making Telecoms Work albeit at a low data rate or Bluetooth or GPRS with some extended hibernation capabilities that reduce power drain to the sort of levels needed. Note that the ZigBee standards process is reasonably closely linked with the Home Plug Alliance (see previous chapter) and the WiFi alliance. The ZigBee physical layer consists of two different options in three license-free frequency bands with sixteen channels at 2.4 GHz (the same as Bluetooth and WiFi) with a maximum data rate of 250 kbps, ten channels at 902 to 928 MHz (The US) with a maximum data rate of 40 kbps and one channel at 868 to 870 MHz with a maximum data rate of 20 kbps (Europe, Australia and New Zealand). Both physical layers use direct sequence spread spectrum (DSSS) modulated O-QPSK with a 32 PN-code length and an RF bandwidth of 2 MHz in the 2.4-GHz band and BPSK modulation with a 15 PN-code length and an RF bandwidth of 600 kHz in Europe and 1200 kHz in North America. And in the consumer space we may now finally be on the cusp of seeing broader market adoption. On 16 June 201