A Wireless LAN is a Wireless local country web which is used to link two or more computing machines without wires. This is an extension of wired LAN which reduces the demand of wires and gives mobility within the local country and still be connected to a peculiar web. Using radio frequence ( RF ) engineering they transmit and receive informations over the air to acquire the web entree without utilizing wires. This gives easiness to the people who use hand-held devices like cell phones, notebook computing machines etc. For place user and concern radio LAN became popular as people do non necessitate to remain at a topographic point to entree the cyberspace. Spread spectrum engineering is used for radio LAN to link devices to the web.
Why radio ( wireless vs. wired webs ) :
Both wired and wireless webs have advantages over each other. Few differences are below:
Installation: Installation wired web is a spot hard undertaking as we need to draw wires link them and give connexions, but when compared to wireless it consumes less clip as wireless webs take clip for configuring the router and connecting to the peculiar web. In the instance of extra users wireless web is best as no excess work is needed, but in wired once more the procedure should be done.
Mobility: Wired webs are immobile as the user should be at a stationary point to utilize the web, but in wireless webs users can travel about in the web entree country.
Cost: Wired webs are expensive covering big countries while radio webs do n’t affect this cost.
Speed: Wired web is faster than radio and ne’er face public presentation job.
Security: Wireless web is non unafraid as unauthorised users can entree web which causes many jobs like crashing webs, illegal use of the informations etc. Whereas in wired webs unless the user connects through the plug-in point they can non entree.
Dependability: When put ining or traveling wired webs batch of attention should be taken to look into the overseas telegram connexions. Loose connexions lead to failure of wired web no such job in radio webs.
Working of WLAN:
Wireless LANs use electromagnetic wireless or infrared moving ridges to pass on from one point to another point without depending on any physical connexion. Radio moving ridges are besides called as wireless bearers as they deliver energy to a distant receiving system. The familial information is modulated on to the wireless bearer. If the wireless moving ridges are transmitted decently on different frequences, multiple bearers do non interfere even if they are in same infinite and at the same clip. If the wireless receiving system has to pull out informations it tunes to one frequence and culls all other frequences. In a radio constellation a device called as entree point is used. This is used to have, buffer and to convey informations between the wired web and radio web substructure. Access point can work within a little scope of country less than 100 pess to several hundred pess, which supports merely a little group of users. Wireless LAN is accessed by terminal users through radio LAN arrangers.
Configuration of Wireless LAN:
Wireless web can run in two manners:
Ad-hoc manner web:
Wireless web interface cards should be placed in Personal computers to put in an ad-hoc web in little countries like place or little offices. Personal computer cards are besides available for notebook computing machines and laptops.
Ad-hoc manner is wholly wire-less. Ad-hoc webs are easy to repair and are low-cost. Peer-to-peer footing is used to link workstations with each other. If a radio broadband router is added to ad-hoc web, computing machines can be given internet entree to that specific web.
Figures: Ad-hoc radio web
Infrastructure- manner web:
For a larger web installing in substructure manner, both NICs and entree points must be installed and configured. Access points should be configured carefully depending up on the signal strength and quality. After the installing, NIC s and entree points should be configured. In this web entree points are used to link workstations. Workstations communicate entree point without pass oning workstations straight. For little and average sized webs substructure is best.
Figure: Infrastructure radio web
Wireless LAN Technologies:
Spread Spectrum Technology:
Spread spectrum engineering was originally developed for the military which uses more bandwidth than narrowband engineering. Spread spectrum is more dependable, secure than narrowband. This is possible because the spread spectrum allows for more bandwidth as it continuously changes the frequence of the familial signal. High spectrum use and opposition to multipath are the chief advantages which made spread spectrum engineering so interesting. In satellite communicating, telemetry systems spread spectrum engineering is in usage. Transmission capableness of the wireless channel can be maximized in spread spectrum. In this technique the information rate can be modified or changed harmonizing to the demand which maintains the nexus during inauspicious conditions. Spread spectrum is classified into two types:
Direct Sequence Spread Spectrum ( DSSS ) :
DSSS generates excess spot pattern for each transmitted spot which is known as come offing codification. Length of the bit codification and transmittal of informations are straight related like if the bit codification is long, transmittal of the informations will be decently received but uses more bandwidth. Because of the splintering codification, harm of spots and retransmitted informations can be recovered.
One information spot
Zero informations spot
Word for every
One information spot
Same bit codification word but
Inverted for zero informations spot
Figure: Direct Sequence Spread Spectrum engineering
Frequency Hoping Spread Spectrum:
In frequence skiping dispersed spectrum informations which is modulated with narrowband bearer signal hops from frequence to frequence as a map of clip.
Figure: Frequency Hoping Spread Spectrum Technology
This is done by distributing the signal in clip sphere whereas DSSS is done by chopping each spot in frequence sphere. If the sender and receiver travel at same clip and same frequence a individual logical can be maintained.
Narrowband system uses a specific wireless frequence to convey and have informations. It uses a narrow wireless signal frequence for go throughing the information. By organizing different channel frequences for different users this technique avoids unwanted XT between communicating channels. One drawback is that terminal user must obtain FCC licence for each site.
Types of Wireless local area network:
Peer to Peer web:
In a basic radio web, sing two computing machines with wireless arranger cards can reassign files, emails etc to each other straight in that web. Each computing machine acts as a transmitter and receiving system depending up on the demand. Peer to Peer web is best manner for interchanging little sum of informations and is besides less expensive. This is non efficient for big informations exchange.
Client and Access point:
Ad-hoc web scope can be increased by put ining entree points. Each client should hold entree to server resources and to other clients as the entree point is connected to the wired web. Number of clients each entree point can suit depends on the nature of the transmittal involved.
Multiple entree point and extension point:
Access points can function merely little parts, if we have to utilize for big country like college many entree points should be used. Access pints should be topographic points in such an order that whole college can be connected to the web without any job.
Directional Antenna Network:
This is the last point in radio LAN web. Suppose radio LAN should be extended from one edifice to another with certain distance, directional aerials are used. These are placed on the edifices confronting each other. Antenna on one edifice is connected to the wired web via entree point of that edifice and another edifice aerial is connected to that peculiar wired web with the aid of entree point because of which connexion is enabled.
Advantages of Wireless LAN:
Convenience: Wireless LAN is convenient to utilize as there is no demand to happen a stopper in point for the web entree and to be in a peculiar topographic point. Because of this engineering usage of laptops, cell phones and many hand-held devices increased.
Mobility: This engineering gives users the mobility to travel about within the limited country of the web to entree the web. This became helpful for concern people where they can utilize cyberspace in java stores, shopping promenades etc.
Installation Speed: It is really easy to put in as there is no demand to draw wires and connect.
Installation flexibleness: It is flexible to put in web even in topographic points where wired entree can non be given.
Cost: First clip installing cost is more than wired, but overall cost is low. Benefits are greater during frequent altering or traveling.
Expandability: This can back up the addition of the client as this does n’t necessitate any wiring for increased users.
Disadvantages of Wireless LAN:
Security: Unauthorized users can entree radio LAN. Such users can capture informations and do jobs like crashing a web, etc. This is a ambitious undertaking for concern people and professionals to protect their informations from such illegal users.
Signal intervention: Walls, edifices and physical constructions can cut down the strength of the signal, which consequences in restricting radio LAN scope and connexion quality. Other radio engineerings utilizing same web can besides impact the signal strength.
Speed: The velocity of radio LAN is less compared to wire LAN. Performance issues are besides caused by TCP and its constitutional congestion turning away.
Energy: Power ingestion is high, battery life is low and heat is besides jobs for radio LAN.
Applications of Wireless LAN:
In infirmaries to direct patients inside informations from point to indicate ( physician to nurse or sophisticate to physician ) .
It is helpful for members who are in run intoing so that they can do a determination based upon other squad member ‘s sentiment and besides by seeing few practical things from the Internet.
It is a good application for developing in companies, schools, and universities etc, where exchange of informations can be done with the aid of web entree.