Information Technology Reference
In-Depth Information
Chapter 5
Abstract
Ubiquitous computing and pervasive systems are strongly based on the
communication between people and surrounding environment, better if in
mobility. Wireless technologies make the needed mobile communication
possible by freeing people and devices to be wired. Wireless communications
had a fast development during past years, thus leading to the current low-cost
devices that are more and more embedded in everyday items, such as cellular
phones and other personal mobile devices. Owing to their key role in
pervasive systems, this chapter presents some of the most used wireless
technologies, giving some useful detail about them.
1
Wireless data transmission
Wireless technologies are rapidly evolving, and the enthusiasm of designers
and users in using them is growing up consequently. Nevertheless, there are
several problems due to the nature of the physical media used in wireless
communications. In fact, it is hard to set up a comprehensive model of the
media taking into account all possible interferences that lower the signal
quality. The main goal of ongoing studies and researches on wireless
technologies is a better knowledge of the radio spectrum. This will allow for
the setup of rules for channel access and connection establishment, with the
lowest interference level and with the minimum power requirements.
Wireless communications for data exchange take place mainly within the
industrial scientific medical (ISM) band which is centred on 2.45 GHz, where
