Wireless Lans And WI FI Computer Science Essay

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This paper is discuss about the familiar topic about traditional wired networks and wish to get familiar with wireless networks and some of the consequences in their development. Now a days wireless network are becoming growth in the form of IEEE 802.11b wireless LANs, by this users can use the network throughout the building with the Wi-Fi enabled accessories linked with the network.depection of Wi-Fi as how the 802.11b is acquiring the provide higher data rates and better quality of service.

Wireless LANs and Wi-Fi:

Benefits of Wireless LANs:

The cost of wireless LAN is also less while compared to wired version, Not only in the cost of wireless components but in the installation procedure of the wireless components aswell.The modifying of the wired networks and installation of the wired networks are more expensive to execute the network and power cables, all in conformity of the building codes. For this cause a wireless LANs are being implemented in the network. Some of the extra applications of wireless LANs that ensues cost savings are:-

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Execution of temporary networks

Easily moves and changes the network within the organization.

Implement in hard to wired locations.

Omission of costly rented lines.

When the users are connected to internet and connected to the network they are freely roam one network to another network and also wireless LANs gives the enterprise mobility and flexibility for the users. It increase the efficiency by accessing the data and also very simple to install. Wireless LANS are very easy to understand and implement the network.Functionning of wireless LANS are same as Wired Ethernet networks, but they are less cost to implement the network and free to roam everywhere in the same network.

802.11 basics

Wireless LAN product Certification

802.11 products are certified by a Wireless Ethernet Compatibility Alliance organization to meet the standard specifications. The first categories of the products are certified by WECA which is based on the 802.11b standards. All the WI-FI devices are certified and Wi-Fi logos are on those devices that initiated by approved by the certification of the wireless device.

Network Topology:

The basic requirement to initialize the wireless LANs requires radio transceiver and antenna. Components parts are either access points or stations. These are inbuilt in wireless LAN card installed in the desktop or either USB adapter or PC card. Access points are bridged between wireless LANs and wired LANs. The configuration of the network can be handled in two basic ways:

Peer -to- peer network: In this network two stations are communicated with each other without access point, it's similar to the wired network. When two or more stations organize a peer to peer network it's concerned as an independent basic service set.

Client/Server mode: - In this network multiple stations are linked with access points, which pretend a bridge to a wired network. In this configuration BSS is concern in infrastructure mode.

The Evolving 802.11 Standard:

The IEEE:

The IEEE 802 standards committee raises series of standards related to 802.x series, encounter as LANs and MANs and also PAN such like Bluetooth. The committee is divided into different sub divided working groups are numbered 802.1 to 802.17. Each group conduct on different issues and formulating the same number as the working group. The standards of security and logic link control employ to wired and wireless LANs.

RF Fundamentals for WLANs

Though wireless LANs are easy to spread, the network management will useful to propagate the radio wave signals. Although we can use infrared technology also but it takes line of sight between the transceiver of the network in this journal it deals only radio frequency wireless networks, assumes the industry standards of wireless LANs.

The reason behind using the RF is , the signal can penetrated through solid objects like building walls.neverthless,radio waves cannot travel a long distances without weakening or being pretended by physical barriers. Before the wireless networks can be planned the users have the basic knowledge of propagation characteristics and data rates.

Propagation Characteristics Must is Considered:-

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Reflection - Radio waves are reflected by some materials. This development is frequently used in microwave signals among stations but is not for line of sight signal propagation and in an office environment it can make a multiple path.

Absorption - Radio wave signals are absorbed by many objects like carpet, water, plastic and rock.

Geometric Spreading loss - Radio waves are similar to the light waves the signal will become weaker as they elaborate outbound away from their source. This loss arises as square of the distance, means that if the device is motivate two times far away the power of the signal is reduced by one fourth of the original one.

Path loss - The over developments lead to the path loss or weakening of the signal when it spreads outward, it's depend on the motion and position of employees in the office and office environment and arrangement of furniture and walls will leads to the path loss.

Multipath - The incurred signal which is of radio waves receiving from the continuous signal which is linked up from various paths i.e. few of the real energy has been reflected in the way between it reach the receiver which gives the effects of multipath occurs. Ghosting is regularly observed in antennas which has a linking up to television. Coming to the network users the face these situations in digital counterpart familiarly know as intersymbol interference. This situation occurs due to delay spread for similar signals and radio waves combined which is sufficient for symbol overlap for the digital data. Likewise the data transmission in case of time for both the received data bits is more faster it can even detect the intersymbol interference which concludes that multipath occupies a higher limit in speed for the data transmission..

Propagation characteristics are frequency dependent:

For lower frequency, less radio frequency energy is absorbed by objects when signal is propagate through solid objects. For higher frequencies little antennas can be used.if antennas are scaled down proportionately with wavelength, the received signal power will be reduced as function of frequency squared, for this less energy being stopped by the smaller antenna we can overcome by using the high gain antennas.

Data Rate and Range are related:

In the signal to noise ratio (S/N ratio or SNR) is explained in consideration with noise range regularly with the signal strength. The connection together for SNR of received signal along with the data sent upon the channel is explained as information theory. The outcome for the client will be as per the issued SNR the BER will be higher while data rate will be higher.

Hence a compromise is involved between data rate and range while the rest are similar. While wireless network executed top most information computing process it leads to massive decrease. Equally when a wireless network runs at higher range the information of computing seemed to be decreased to reach minimum BER.When FCC places a upper limit on this account of power levels then it is not needed to reduce the data rate to improve the power range.

Specially for huge corporate LANs the wireless network set up is not so hard to access its performance When we handle a Rf survey which shows the multipath as well as path loss hence with information theory and range

Regulations

Sharing the Airwaves:

In the wired networks it sends the traffic over a dedicated line segment, while in Wireless LANs it sends the traffic over a shared space. It gets a new challenges in the form of interference from other shared space and its require for additional security.

Allocated Spectrum:

The Federal Communications commission has 15 rules, Wireless Lans and Bluetooth both these are operating under this commission. Globally they allocate the shared portion of the spectrum for Industrial, Scientific, and Medical(ISM) bands in the 2.4 GHz region, but in the case of 802.11a WLANs unlicensed National Information Infrastructure band is used in the 5GHz region. For the individual user does not require a license to access the spectrum, for this reason a portion of the spectrum is kept aside for unregulated use. Those wireless devices are utilizing ISM bands for laptops, microwave ovens and portable phones, for door openings, security devices etc.In between the ISM bands, all users share the spectrum and must endure the interference from each other.

Mandated Use of Spread Spectrum Techniques:

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Radio broadcast for data depending on the topic for injecting data into else adapting a carrier wave. Historically a small range of band in radio transmitting centers with a particular frequency. When the transmitted active substance at particular frequency is surrounded.

A high range of frequency bands of signals are sticky and scattered in various direction is FCC this condition is applied for multiple number of clients.

To reduce the interference crossing a limit of energy range of 0dBm need to follow frequency hopping else go with direct sequence spread spectrum methodology .FCC is accepts Orthogonal Frequency Division Multiplexing (OFDM). These are used to resolve the same criterion usage of distributing the signal energy upon the spacious range of frequencies which simultaneously decrease mean of energy density at specific frequency which in case reduces interference for other signals of similar kind.

Some of the signal-spreading techniques as follow:

Frequency Hopping Spread Spectrum:

Frequency Hopping Spread Spectrum (FHSS) has been delivered as a source to encrypt the broadcasting from unwanted listener. These days we are using for other usagelike reducing the interference. Frequency hopping eliminates by broadcasting the signal carrier for less span of time on slender band, and hopping for alternative and so on. For a certain period of span, the sum of signals transmitted energy is hence scattered for huge band of set of frequencies. The frequency hopping resembles alternatively for everyone who has no knowledge of programmed hop model. Before half a century ago there is no chance of tuning a broadcasted signal. Carries are never similar in their bandwidth when they are transmitted frequency. The LANs as well as PANs integrated FHSS on the suspected hoping sequence to regain the available signals. FHSS is entirely dependent on wireless LANS as well as PANS it does not supply any kind of support or protection even though it is mainly designed to compress interference transmitting and receiving data from other devices.

http://1010.co.uk/images/fsk.png

Fig: Frequency shift keying

(http://en.wikipedia.org/wiki/Frequency-shift_keying)

Direct Sequence Spread Spectrum:

Direct Sequence Spread Spectrum (DSSS) can be considered as complicated method which scatters the signal energy over a spacious bandwidth along with the scattering of the carrier for its reflexive meanwhile FHSS is surrounded by itself. Pseudo-random noise specifications are taken to consideration which straight away alters the carrier signals with a highly accelerated encrypted sequence. For greater extent bandwidth the carrier is altering the carriers directly. The scattering order is provided by altering the data stream using the PN spreading code hence its output is directed to be a means of communication with heavier bandwidth when compared with data bandwidth uniquely. Here bit rate is more when compared with data rate while the bandwidth is efficient

http://www.globalspec.com/RefArticleImages/1002E2581441ED3C3C876BC8F6D930F7_6_CH06_33.gif

Fig: Direct Sequence spread spectrum

(http://www.globalspec.com/RefArticleImages/1002E2581441ED3C3C876BC8F6D930F7_6_CH06_33.gif)

Orthogonal Frequency Division Multiplexing: - OFDM uses multiple subcarriers is technically not a spread out spectrum technique as the carriers are fixed not distribute, but it does the same function of spreading the signal power over a large band. It acts as a dividing the same signal into different parts and transmit each signal by using different subcarriers at different center frequency. The same data of different fast data transmission is sent over an as many small transmissions at the same time, for different frequencies. To avoid intersymbol interference higher data rates are needed that broken the signal into different parts and transmit over a subcarriers, each part has transmit over a slow enough rates. For practice bandwidth is useable for additional subcarrier is determined by FCC.To carry the information over the carrier has to use different techniques for spreading the signal carrier and to use different digital modulation techniques to define the different wireless technologies and standards, also placing a view on interference issues between Bluetooth and 802.11 LANs networks.

subcarriers in Orthogonal Frequency Division Multiplexing (OFDM)

Fig: Orthogonally frequency division multiplexing

(http://www.conniq.com/WiMAX/fdm-ofdm-ofdma-sofdma-01.html)

Advantages of WIFI:

1.WIFI has tremendous usages of several approaches and network interfaces encode to guard the traffic capturing.

2. Feisable cost ranges are available as debt among the marketing server's increases.

3. WiFi consists of group of global standards not as similar as telecom carriers, These Wi-Fi servers can serve thought out the world at any cost and span.

4. Roaming of system is feasible in these networking formats which can be used even if away from access point.

5. Wifi uses uninhibited radio spectrum and hence acceptance of every users.

6. The LANs are assisted with cabling. The related prices are according to network connectivity and widening the cables where it can't be used to access.

7. Markets produce these Wi-Fi items which access the network user's interfaces. These are also capable to correlate a very primary service as well.

Disadvantages of Wi-Fi

1.The no restricted access points are deliberately harmful to unknown to begin the attack with is highly harder to trace the access point.

2. Entry point can be edited to encode individual and secret data to be sent from Wi-Fi consumers.

3.The unlicensed 2.4 GHz spectrum , is usually busy traffic and used by different kinds of devices such as Bluetooth, microwave ovens, cordless phones and many different items.

4. A very less range is present in Wi-Fi network.

5. No matter how the configuration is constructed, the familiarly used Wireless encryption standard which has been wired shows breakages.

WI-FI LIMITATIONS:

Wireless technology endures two types "infrastructure" mode and "Adhoc" mode in ad hoc wifi networks are established without any access point. Adhoc networks have some issues that configure the network over nominal security intruders and also the network hackers have also easily to dominate the Ad hoc network.

Security concerns:

Installation of WIFI network is very simple but it's difficult to secure the network. Not possible to spread the encryption methods at access points. For hackers it's easily hacked the Wi-Fi network to steal the information. The users can easily use the network and minimize the performance that is not potentially affected.

Interference from other devices:

The transmission of wifi data transmission is 2.4 GHZ causing susceptible to interference of Bluetooth enabled devices, Microwaves,mobilephones and other communication devices nearer the interfering devices are the poor communication and vice versa.

Conclusion:

WI-FI is a technology that is going through a rapid development in standards, and their applications and devices. According to the market requirements and technology devices WI-FI alliance certification programs are to develop. This technology is enhancing rapidly and embedded in all portable devices like mobile phones and PDAs and the various consumer electronics devices like cameras and game consoles that build real time applications like VOIP. In the coming future WI-FI alliance requires introduce new certification programs driven by application and device necessities also by the development of the IEEE 802.11 standards.