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Examples of Existing Networks
Some of the prominently used networks in today’s world are −
- Internet
- IEEE 802.11 for Wireless LAN
- RFID and Sensor Networks
Internet
Internet is a global collection of vast number of dissimilar networks that are interconnected together. Internet uses the TCP/IP protocol and provides varied services. The networks forming the Internet may be private, public, academic, commercial or government, but Internet as a whole is not controlled by any one organization. Internet uses a wide range of networking technologies which are being continually upgraded.
The traditional services provided by the Internet were electronic mail, file sharing, and hyperlinked documents. The passage of time has been witnessing more and more services like telephony, online music, and videos, online business, digital newspapers, instant messaging, social networking, online forums, online storage and computing, online financial service and shopping, etc.
IEEE 802.11 for Wireless LAN
Wireless LAN is a local area network that does not use any cables for connecting the networked devices. The standard for WLANs is IEEE 802.11. It is a set of Media Access Control (MAC) and Physical layer standards that operate in bands 902–928 MHz, 2.4–2.5 GHz and 5.725–5.825 GHz. 802.11 networks comprise infrastructure called Access Points (APs) or base stations and clients which are wireless devices like laptops, mobile phones etc.
802.11 has revolutionized wireless networking. It is being prolifically used in buildings, trains, planes, ships etc. and allows people to use the Internet in rooms as well as transits.
The main standards under 802.11 are −
- 802.11a and 802.11g: Uses OFDM (Orthogonal Frequency Division Multiplexing). It divides the wide spectrum into slices over which parallel transmission occurs and has bit rates up to 54 Mbps.
- 802.11b: Uses DSSS (Direct Sequence Spread Spectrum) and provides bit rates of 11Mbps.
- 802.11e: Adds QoS (Quality of Service) and multimedia support to WLANs.
- 802.11n: Adds multiple inputs multiple outputs (MUMO). This permits additional antennas and transmitters and spatial multiplexing. The bit rate is 100Mbps.
RFID and Wireless Sensor Networks
RFID stands for Radio Frequency Identification. It uses radio waves to identify and track tags affixed on objects. RFID readers are installed at tracking points and can read information from tags when they come into range, which can be of several feet radius. They are used to check identities and track inventory, assets, and people.
WSN stands for Wireless Sensor Networks. It comprises a collection of spatially distributed sensor devices that monitor and record environmental conditions. The information from the sensors is collected by a central computer or gateway and processed. They have a wide range of applicability like earth sensing, pollution monitoring, forest fire detection, military tracking, health & home applications, and industrial & commercial applications.
The integration of RFID and WSN extends the application of RFID to larger areas of 100–200 meters. It comprises an RFID reader, a Radio-Frequency transceiver, and a micro-controller. Tags integrated with WSNs can communicate with other tags, thus forming a multi-hop network, spanning a wider area.
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