Technical Aspects And Data Encoding Computer Science

Nowadays wireless hotspots are famous. They are available at homes, cafeterias, universities, colleges, airports, railway stations etc., Many people in the world are easily able to browse the internet using their laptops, palmtops, smart phones and desktops and all the other related devices at hotspot at these places as well as entire cities.

Wireless uses radio frequency waves to communicate from one end to the other. A computer's wireless adaptor converts data from binary form to a radio signal and then it is transmitted to the aerial on a router that decodes the signal waves again into binary format and sends it via a physical line to a modem for modulation and demodulation. The reverse process occurs in the backward process. Information is passed to the modem and it is demodulated to send via a physical cable or line to the router or adaptor. Again in the router it is converted to a radio signal and transmitted to a receiver on the wireless adaptor. The adaptor again interprets the information into binary form.

Wireless communication began in the latter 19th century and in the beginning of 20th century when Guglielmo Marconi created the wireless telegraph and signal company in 1896. Finally in the latter 1990s, a standard was developed for the use of Wi-Fi: 802.11

The 802.11 standard was developed in 1997 by the IEEE. 802.11 have the ability to transfer data on an average rate of 1Mb/sec while the maximum gatherable information/data transfer rate is 2Mb/sec.

Differences between 802.11g and 802.11n

802.11n is the latest standard of WiFi technology. It is the alternative standard of 802.11a, 802.11b, and 802.11g. The standard is said as IEEE 802.11n because its protocol was discovered by the institute called Institute of Electrical and Electronics Engineers.

High level of interference is in 802.11n and low level of interference is in 802.11g.

The standard 802.11n, transfers the data much faster than other standards. The speed of 802.11n is 22Mbit/sec- 24Mbit/sec and the speed of 802.11g is 100Mbit/sec-140Mbit/sec.

Standard 802.11n also functions on the 2.4GHz band, similar to 802.11b and 802.11g. It is also active on the 2.4 GHz band, similar to 802.11b and 802.11g. This frequency does not need line of sight accessibility like 802.11a which functions in the adjusted 5GHz band.

The maximum throughput of 802.11g is 25-54mbps whereas the maximum throughput of 802.11n is 74Mbit/sec

Cost of 802.11g is expensive than 802.11b and less expensive than 802.11n. Cost of 802.11n is the most expensive standards among them.

The maximum area covered by the 802.11n is 50feet whereas 802.11g covers 100feet.

MIMO technology is used in 802.11n whereas in 802.11g does not have that technology.

Technical Aspects

The 802.11n allows smooth transition of data with the ability of backward compatibility built into new tool, letting customers/users and business dealers to promote network tools slowly but steadily. The rapid speed lets many robust applications to be successfully run over public hotspots and private LANs and wider area is also projected

802.11n is also like other earlier standards that contains multiple receivers and transmitters. This technology is called as MIMO, the expansion is multiple input multiple output. This technology lets simultaneous and parallel data transmission or spatial multiplexing. This standard also integrates OFDM, the expansion is Orthogonal Frequency Division Multiplexing. This acts as a splitter to split signal frequencies into modulated channels all the way through. Also 802.11n supports an array of electronic devices including handheld equipments.

Multiple Input and Multiple Output SDM boosts data throughput with the spatial data streams increment. Every spatial stream needs a separate antenna at the transmitter and receiver. Additionally, MIMO technology needs detach radio frequency chain and analogue to digital converter at each antenna which converts higher implementation cost compared to non MIMO technology.

40MHz channel is one of the remarkable features integrated into 802.11n which doubles the channel width from 20 MHz in 802.11PHY to transmit data from one end to another. This helps to double the PHY data transfer speed over a single 20 MHz channel.

It stimulates the 5GHz in previous mode or within the 2.4 GHz.

Coupling MIMO architecture with broader bandwidth channels gives increased physical transfer rate over 802.11a and 802.11g.

Data Encoding

Transmitter and receiver of 802.11n use pre-coding and post coding techniques in order to reach the capacity of MIMO link. Pre-coding consists of spatial beam forming and spatial coding. And spatial beam forming improves the received signal quality at the decoding stage. Spatial coding amplifies data throughput through spatial multiplexing and amplify range by developing the spatial diversity, via techniques such as space-time block coding.

Figure: Authentication ProcessAmount of antennas needed

The number of synchronized data streams is restricted by the least amount of antennas in use on both sides of the connection. The individual radios mostly restrict the number of spatial streams that may take only one of its kinds of data. The symbol aÃ-b:c assists to recognise what a given radio signal is capable of. The first symbol "a" is the maximum number of transmit antennas or radio frequency chains which is used by the radio. The second symbol "b" is the highest number of receive antennas or radio frequency chains that is used by the radio. The third symbol is "c" and it is the highest number of data spatial streams the radio receives.

The 802.11n lets up to 4Ã-4:4. Usual configurations of standard 802.11n devices are 2Ã-2:2, 2Ã-3:2 and 3Ã-3:2. All these compositions have the same utmost throughputs and features and differ only in the amount of diversity the antenna systems provide. Although another configuration known as 3Ã-3:3 is becoming common, which has a higher throughput, due to the additional data stream.

Cost and Reliability

Cost is an important factor which most of the industries concern. Analysis report shows that 802.11n devices are used in wide range than 802.11g. Moreover, deployment of dual-band wireless connections shows compatibility with 802.11n and 802.11g. Customers deploys multimode WLANs for the equal cost of an "a", "b", "g" and "n" capabilities need a dual band radio/transmitters on each for the 2.4GHz and 5.2GHz.

Advantages and DisadvantagesAdvantages

Standard 802.11n is almost platform independent and supports almost all the platforms including Windows and Macintosh.

Greater reliability and advanced compatibility with previous standards.

High speed data transmission

Provides two methods of operations infrastructure and adhoc

Adopts to MIMO technology

Automatically avoids channel conflict

Simple configuration and monitoring

Covers wide area of hotspot

Uses the benefits of OFDM (Orthogonal Frequency Division Multiplexing) which is efficient way of handling multipath.

Supports better security features such as WiFi Protected Access (WAP) and WAP2 authentication with pre shared key or Radius Server

Disadvantages

More expensive

Needs MIMO Adaptor for full performance

Firmware is buggy

The use of multiple signals may highly interfere with close by 802.11g or 802.11b based network

More resistant to signal interference from outside sources

Though the OFDM helps in efficient multipath, it suffers from almost relatively large peak to average power ratio reducing the efficiency of the Radio Frequency power Amplifier.

802.11n uses MIMO technology which is very sensitive to channel conditioning and computational complexity.

Summery - 01

No wonder why 802.11n captured today's market as it has high reliability, high speed data transmission and covers wide range of hotspot. But still, it is difficult to buy final guaranteed versions in the market. Though it is platform independent, the standard is not yet finalized.

Large amount of features are available in this standard, such as Channel width, Radio Frequency Band, less number of antennas, and modulation. It is also firmware upgradable.

The 802.11n spectrum is very complex and contains a vast amount of possible variants and options.

The 802.11n standard covers a wide range of hotspot, better compatibility with most of the operating systems including open source such as LINUX and UNIX, higher throughput and best quality.

802.11n has the backward compatibility with 802.11a and 802.11g; therefore it has high demand among customers.

The 802.11g applies 2.4GHz band and it suffers from the interference of microwave, cordless devices like telephones and Bluetooth devices using this band. 802.11n standard uses MIMO technology which avoids the interference of other waves. But in the case of 802.11n, it is assembled to overcome previous standards by adding MIMO technology. MIMO applies multiple transmitters and receivers to let high amount of information throughput through spatial multiplexing.

802.11n uses multipath signals are upgraded by the MIMO technology and with MIMO, the multipath signals are settled or solved and thereby deliver the information as expected.

This MIMO helps 802.11n in sending and receiving information quickly, at a high speed and to a maximum distance than the other standards.

Also it takes the advantages of Orthogonal Frequency Division Multiplexing to create a resistance against multipath signals and thereby giving a best signal to the Client. Moreover, OFDM was applied in the previous standards but the greater effectiveness is seen in 802.11n.

The wireless hotspots also face other kind of challenges, in an unknown node problem; a hotspot is visible to an access point, but not visible to other hotspots. This causes problems in media access control.

Summery - 02

Because it supports all platforms, the standard 801.11n is more reliable than any other standards. Its reliability is versatile because it has higher throughput, faster speed and high compatibility towards new electronic devices including hand held devices, streaming videos, HDTV and personal computers. The 802.11n uses the technology called MIMO and uses several antennas to transmit multiple data concurrently than a single antenna. This technology lets the data to transfer concurrently while increasing the transfer rate. It shows the backward compatibility with other previous wireless standards.

There is no security maintenance available because they are not required, the WPA2 encryption technology is used by the available network hardware is considered by most to be highly secure.

It is significance examining the box of any network tool the customer has bought in the previous years as the customer may find it is compatible with 802.11n and requires to install correctly.

Currently 802.11n hardware is very expensive than 802.11g. 802.11n wireless router is mostly used by the fast broadband connections or those that regularly copy huge number of information or data through a wireless network.

The Enhanced Wireless Consortium was founded to speed up the IEEE 802.11n development process and support a technology specification for the interoperability of the next generation wireless local area network products.

Because of backward compatibility, 802.11n standard has the flexibility to be applied alongside and combine with existing wireless network. This is more suitable for colleges and business environment where large file transferring occurs. Thereby this standard allows large file transfer to become more reliable and faster.

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