 factors. However, there was a massive standards battle combined with a failure to establish a consistent spectral policy interregionally, SO UWB never made it to the market. There does now seem to be a regulatory consensus that there should be three internationally agreed universal allocations for device-to-device communication, a low-frequency allocation at 125 kHz, the NFC allocation at 13.56 MHz and the 2.45 GHz allocation. These devices need to coexist with the other radio systems within the phone including wide-area cellular and local area (Bluetooth and WiFi) and receive only functions such as GPS. 19.8 Multiple Protocol Stacks Standardised radio protocol stacks include Bluetooth7 (optimised for throughput) and ZigBee8 (optimised for low power consumption), both of which have well-developed vendor support. There are additionally operating systems optimised for low power consumption such as Tiny OS9 and a range of specialised proprietary offerings. 19.9 Adoption Time Scales - Bar Codes as an Example Contactless smart cards and each of the microdevice options referenced in this chapter (HP Memory Spot, smart dust motes and micro-RFID) all offer or offered intriguing and potentially compelling cellular phone device and system-level integration opportunities. They are, or were, technically feasible and supported by radio standards and protocol stacks that are relatively mature. The devices do not necessarily need to reduce in size but will increase in functionality and reduce in cost, thus broadening their application profile. However, business 7 http://www.bluetooth.com/Pages/Bluetooth-Home.aspx. 8 http://www.ZigBee.org/. 9 http://www.tinyos.net/. Network Software - Microdevices and Microdevice Networks - The Software of the Very Small models may take longer to evolve than might be expected. Traditional bar codes provide an example. The beginning of bar codes as we know them today can be traced back to a patent for 'a Classifying Apparatus and Method' filed in 1949 by Bernard Silver and Norman Woodland. Silve