WLAN (Wireless Local Area Network) is a technology to build wireless data networks with satisfactory parameters and very large ranges operation at a relatively low cost. Additional advantage of this technology is little time needed for implementation.
Potential of WLANs
* The local wireless network at home, office, business, etc.
* Wireless access to the Internet in public spaces, for example, in airports, train stations, bars, etc. (hot-spot)
* Point to point wireless links (LAN networking, telemetry, remote control, remote control)
* The wireless Internet access (both in cities and country)
* Emergency Communications Link (the doubling of network cable)
WLAN Standards
I will describe some of the solutions meet the following three rules:
* 802.11a – in the band 5 GHz: 5.150 to 5.350 GHz and 5.470 to 5.725 GHz, transfer rate up to 54 Mbps;
802.11b – In the 2.4 GHz band: 2.4 to 2.483 GHz transfer rate up to 11 Mbps;
* 802.11g – in the 2.4 GHz band: 2.4 to 2.483 GHz, transfer rate up to 54 Mbps;
However, there also used other standards
* 802.11f – IAPP – Inter Access Point Protocol – for cooperation between access points;
* 802.11 – Standard defining new security methods in wireless networks;
* 802.11n – standard for transmitting multimedia in homes using technology MIMO, up to 300 Mbps;
* 802.11e – QoS standard definition – support the high quality of services;
* 802.16 – standard for WiMax networks high-capacity trunk
Range wireless network
It should be noted that the range of a wireless network depends on many factors, we can have an influence on some of them and the rest is unknown. The range of your wireless network depends on:
1. Factors related to the devices used:
* Output power (which is decided by the manufacturer),
* Mitigation of cable (depending on cable length)
* Gain antennas (given by the manufacturer),
* Sensitivity of the devices (given by the manufacturer).
2. External factors
* Attenuation between the antennas (can be estimated based on the FSL model);
* Interference from other devices (not predictable – some additional safety margin must be provided to compensate for these interferences),
* Influence of physical obstacles (walls, floors, trees, etc.)
Thus Therefore, if we want to know what the effective reach of our network, we have to collect the above information and take simple calculations shown in the back This self-help book.
Propagation of radio waves
Fresnel Zone
Fresnel zone is one of the concepts stakes related to the propagation of electromagnetic waves, which is essential for assessing the parameters of wireless connection. Is the area that actively involved in the transmission of radio signal power. Shape of this area is an ellipse in longitudinal section, and the circle in cross section. Radius of the circle is a function of the ratio of the distances between the antennas – has the maximum value at the center of the link. The importance of the first Fresnel zone comes from the fact that almost all the energy of the signal is transmitted through this space.
The shape of the Fresnel zone. R1 is the radius of Zone I.
[m], where:
* DKM = d1km + d2km is the distance between antennas in km
* D1km – distance of the first antenna in km
* D2km – distance from the second antenna in km
Mistakenly did the installation. The installation program does not guarantee mutual visibility of the antennas. The radio link is not working.
Another example of the installation done improperly. Presence of barriers in the first Fresnel zone causes radio link still not working properly.
… is just the beginning … full version of this text that can be found in DIPOL library Web site (for free, no login required).
About the Author:
Text by IT and network specialist. All rights are reserved.
Article Source: ArticlesBase.com – Self-help Book for Wlan Installers/providers
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