Electromagnetic Radiation and Human Health
In the case of wireless networks, the medium for communications is the EM field, the region of space that is influenced by the electromagnetic radiation. (Unlike audio waves, radio waves do not require a medium such as air or water to propagate.) As with wired networks, amplitude decreases with distance, resulting in the degradation of signal strength and the ability to communicate. However, the EM field is also dispersed according to the properties of the transmitting antenna, not tightly bound, as is the case with communication on a wire. The area over which the radio waves propagate from an electromagnetic source is known as the Fresnel zone. To mitigate the effects of interference from these devices and other sources of electromagnetic interference, RF-based wireless networks employ spread-spectrum technologies. Spread-spectrum provides a way to share bandwidth with other devices that are operating in the same frequency range. Rather than operating on a single, dedicated...
Correct Fiber-optic cable is completely resistant to electromagnetic interference because it uses light pulses instead of electrical charges for signaling. C. Incorrect IEEE 802.11b is a wireless networking protocol, but it is still affected by electromagnetic interference, whether it uses the ad hoc topology or the infra structure topology. D. Incorrect IEEE 802.11b is a wireless networking protocol, but it is still affected by electromagnetic interference, whether it uses the ad hoc topology or the infra structure topology.
A wireless network uses technology that enables two or more devices to communicate through standard network protocols and electromagnetic waves not network cabling to carry signals over part or all of the communication path. This module describes how to plan and implement security for wireless networks.
Creating the cabling diagram requires more than a simple floor plan of the site. To route the cables properly, the network designers must be aware of any obstacles that can interfere with the cable's installation or performance, and these obstacles often do not appear on standard floor plans. For example, when using copper-based cable such as UTP, you must know the locations of fluorescent light fixtures and other possible sources of electromagnetic interference so that the installer knows to route the cables around them. You should also document the locations of heating and air conditioning ducts, plenums, firewalls, and other obstacles that the installer might have to route cables around or through. In most cases, this requires the network designer to carefully examine the site.
A Fast Ethernet LAN connecting 50 workstations in a factory environment with large amounts of electromagnetic interference. 100Base-FX, because only a fiber-optic network is resistant to electromagnetic interference. Advantages Fiber-optic cables are immune to electromagnetic interference, can span longer distances, and are inherently more secure than copper cables. Disadvantages Fiber-optic cables are more expensive than copper, more difficult to install, and require specialized tools. For a network that uses copper-based cables, fluorescent light fixtures can be a significant source of electromagnetic interference. A network blueprint should contain the locations of these fixtures so that the network designer can route cables around them.
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