Indoor Optical Wireless Communication Systems - Part I: Review

The emergence of portable computing devices such as laptops, palmtops and personal digital assistants (PDAs) has fuelled the demand for mobile connectivity and hence, led to the development of wireless local area networks (LANs). Wireless LANs offer users increased mobility and flexibility compared with traditional wired networks, and may be classified as either infrastructure wireless or ad hoc wireless networks [1]. Untethered from conventional network connections, infrastructure wireless LANs allow users to maintain network connectivity whilst roaming anywhere within the coverage area of the network. This configuration requires the use of access points, or base stations, which are connected to the wired LAN and act as interfaces to the wireless devices. Each access point may accommodate multiple clients. Examples of practical applications for wireless infrastructure LANs which are often cited include medical professionals accessing patient records, real-time vital signs and other reference data at the patient bedside, and factory floor workers accessing part specifications and process information as and when required. In contrast, ad hoc wireless LANs are simple peer-to-peer networks in which each client only has access to the resources of the other clients on the network and not a central server. Ad hoc wireless LANs require no administration or pre-configuration, and are created on demand only for as long as the network is needed. Examples of practical applications for wireless ad hoc LANs include employees sharing information during a meeting, and colleagues electronically swapping business cards.