nsmitted power or propagation pattern to minimise co-channel interference for other users, maximise effective range or utilise spatial diversity to increase throughput? Modulation How is encoded data carried on the physical medium, for example by modulating one or more carriers in phase and/or amplitude, or by modulating pulses in amplitude and/or position? Data encoding How are the raw bits of a data frame coded into symbols for transmission? What functions do these coding mechanisms serve, for example increasing robustness to noise or increasing the efficient use of available bandwidth? Media access How is access to the transmission medium controlled to ensure that the bandwidth available for data transmission is maximised and that contention between users is efficiently resolved? What mechanisms are available to differentiate media access for users with differing service requirements? and inter-connection with networks running other operating systems, as well as support for network administration tasks such as enforcing common settings for groups of users. The choice of a network operating system will not be covered in detail here, but should be based on a similar process to that described in Parts III and IV for selecting WLAN and WPAN technologies. Start by determining networking service requirements such as security, file sharing, printing and messaging. The two main network operating systems are the Microsoft Windows and Novell NetWare suites of products. A key differentiator between these two products may be a requirement for interoperability support in networks that include other operating systems such as UNIX or Linux. NetWare is often the preferred NOS in mixed Chapter Two operating-system networks, while simplicity of installation and administration makes Windows the preferred product suite in small networks where technical support may be limited. Summary The OSI network model provides the conceptual framework to describe the logical operation of all types of networks, from a wireless PAN link between