BTEC National Unit 25 Data communications and networks
Infrared connection Infrared refers to light waves of a lower frequency than human eyes can receive and interpret Your mobile phone may have an infrared connection; this can also be found on PDAs, laptop computers and printers. Infrared is a short-range lineof-sight communication technology where you have to point your transceiver (transmitter/receiver) at the opposite transceiver. Infrared can manage a bandwidth of up to 4 megabits per second.
Use of infrared Infrared is used in most television remote control systems, and with a standard called IrDA (Infrared Data Association) it's used to connect some computers with peripheral devices File transfer between laptop computers Printing from your laptop, PDA or sent to your wireless application protocol enable mobile phones Mobile phone to PDA data transfer.
Problems First, infrared is a "line of sight" technology. For instance, you have to point the remote control at the television or DVD player to make things happen. Second, infrared is almost always a "one to one" technology. You can send data between your desktop computer and your laptop computer, but not your laptop computer and your PDA at the same time.
Advantages Because infrared transmitters and receivers have to be lined up with each other, interference between devices is uncommon. Because infrared is one-to-one technology, you can be sure that a message goes only to the intended recipient.
Wireless network card Wireless network cards and access points are devices that use the IEEE standard, which is closely associated with Ethernet LAN technology.
standards is a set of four specifications in the family: , a, b, and g. and each operates at a different frequency and speed: and a operate at speeds up to 6 megabits per second. b is the version commonly used for wireless networking at home, school, college or in small enterprises. This can operate at up to 11 megabits per second. g operates in the 2.4GHz range like Bluetooth, but with greater power can offer up to 54 megabits per second.
Transmission techniques Spread-spectrum will use a range of frequencies and techniques. Narrowband will send a signal over a limited frequency range.
Narrowband Narrowband refers to a signal which occupies only a small amount of space on the radio spectrum -- the opposite of broadband or wideband.
Wireless coverage
Wireless network structure A wireless adapter (a network card). Instead of connecting to UTP, it will send a radio transmission. Computers with wireless adapters can communicate directly with each other on a peer basis. A wireless access point (WAP) is a network hub and will connect by a UTP or fibre cable to the main network. The purpose of a wireless access point is to share and distribute network communication.
Microwave and laser technologies They are used by large organisations for high-speed communication between different offices. Microwave is defined as a high-frequency radio signal above 1GHz. This means that wireless networks, mobile phones and Bluetooth operate as microwave devices. A full-power microwave transmitter will send a radio transmission at a high bandwidth up to 50 km using a narrow- beam transmitter.
Exercise Your centre has recently installed an internet café in an outbuilding that is not connected to the LAN. 1.Visit various networking retailers on the Internet and produce a spreadsheet for 20 computers to be connected to a wireless access point 2.Look up the term ‘war-driving’ on the Internet and create an action plan to prevent this happening at your centre.