s in terms of upload/download time. Continued Chapter Eleven Table 11-2: PAN Technical Attributes - cont'd Requirement type Considerations Quality of service If the usage model includes applications that require isochronous data transmission, then guaranteed quality of service will be an important attribute to ensure performance expectations are met. Interference and If the PAN will have to operate in an environment with other coexistence wireless networks (e.g. an IEEE 802.11 WLAN) then coexistence will need to be a consideration. Power consumption Using PAN features on a mobile device may significantly increase power consumption, and detract from the overall performance of the device by reducing battery life. Network features, such as actively searching for other devices, should be easy to deactivate when not required in order to maximise battery life, for example on a Bluetooth enabled PDA. Operating system Operating system compatibility will be an issue when and other software applications attempt to compatibly inter-operate over the compatibility PAN link. Additional software components may be required, for example to exchange data between a mobile phone and PDA. Technology maturity Considerations will vary with the stage of maturity; before standards have been agreed, early products have an interoperability risk; a fully mature technology may have limited scope for future development and risk early obsolescence as new usage models arise. Operating range This is less important for a PAN, since by definition only a limited operating range is required - the personal operating space. However, PAN technologies vary widely in their achievable range - from 0.1m for NFC to over 100m for ZigBee. With an increasing range of capabilities coming to market in the next few years, significant price differentiation between PAN technologies can be expected. If options like ZigBee and NFC meet the user requirements they will be considerably cheaper than Bluetooth or the UWB alternatives. Implementing Wireless PANs requiremen