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An Analysis Of Wireless Wimax Technology Computer Science Essay

WiMax is a telecommunication technology and is based on IEEE 802.16 standards and also provides different solutions to cable broadband and also helps in providing last mile wireless broadband [2]. WiMax stands for Worldwide Interoperability for Microwave Access [1]. The name WiMax was formed on June 2001 by Wimax forum. The main aim of the Wimax forum was to certify the wireless products which comply with the IEEE 802.16 standards [8].

Following are some characteristics of Wimax [10] [7]:

1. All wireless products from Wimax should comply with IEEE 802.16 standards, and every product before be certified by Wimax.

2. A telecommunication based network based in IP which should cover global coverage for its users at any time and any place.

3. Able to configure Wi-Fi spots.

4. Supports both mobile and fixed applications on NLOS (Non line of Sight).

5. Ability to send wireless signals at a speed of 75Mbps within 30 miles.

6. Compatible with other wireless applications and equipments.

7. Supports OFDM (Orthogonal Frequency Division Multiplexing) transmission scheme.

8. Supports voice, data and other personal communication applications.

9. Less time taken compared to other wired networks.

Figure: 1- WiMax based Network (Source: http://www.gearfuse.com/wp-content/uploads/2008/05/wimax_wixd_101.gif)

DSL Broadband Background:

The process by which a signal covers a broad range of frequencies which is later converted to sub-frequencies and channels. More the bandwidth frequency more is the information carried through signals. For example; a broadband can transmit and receive several megabits without disturbing the telephone signals, a dialup can only transmit and receive of kilobytes and it do create some disturbance during phone conversations [30]. DSL Broadband is mainly famous for its high speed internet connection. According to standards of International Telecommunications Union, i.e. I.113 of ITU. It is considered that the transmission power of broadband is faster than ISDN.

Figure: 2 � Subscription growth between 1990-2006 [6] (Source: http://www.wimax.com/commentary/wimax_weekly/chapter-1-introduction-to-broadband-wireless)

The above clearly describes the subscription by the users to the broadband to internet subscription. The numbers of users which were in 100�s in 1990�s had a steep growth subscribing to broadband till 2006 where around 250 million users. According to the report published by Teleappliant, it has been estimated that there would be around 400 million users till the end of this year through world [5]. There is a lot of benefits which are gained by broadband users such has faster surfing, faster file download, playing music, videos and many other multimedia applications online as well as playing games [7].

Introduction to Wimax:

Wimax can be considered as a solution to all the wired technologies difficulties and concerns. Many companies and industries are trying to find out newer solutions for the wired networks. Over the years there have been many solutions provided by the company, solutions were different according to design of the networks, the bandwidth parameters, protocols, and the applications supporting the networks. That clearly states the difference in the maintaining the standards while finding solutions for the wired networks. Wimax introduces new set of standards which can help in maintaining the common standards by the companies in developing the solutions for wireless networks [10].

1. First Generation LOS Broadband (Line of Sight)

2. Second Generation NLOS broadband (Non line of Sight)

3. Narrow Band WLL (Wireless local loop)

4. Emergence IEEE 802.16 group.

First Generation LOS Broadband:

With the development of High speed broadband internet there were more emphasis made on Wireless Internet Service provider (WISL) in competition for wired internet connections. During the first generation technology, many systems with frequency from -3 GHz to 3 GHz started to evolve. During 1990�s technology named LDMS (Local multipoint distribution system) was used widely due to its unique feature of transmitting signals at 100 Mbps but due to its limited range it was overtaken by MMDS. During the same year, another development in regards to wireless service was launched named as MMDS (Multichannel multipoint distribution system) which used to operate in frequency of 2.5 GHz was useful in providing the wireless broadcast services in rural areas.

Figure: 3 � MMDS architecture (Source: http://www.iec.org/online/tutorials/wire_broad/topic03.asp )

The MMDS antennas were placed high enough to directly face the LOS path of the main transmitting antenna. Due to the distance factor and LOS factor the influence and the growth of the MMDS was slow.

Second Generation NLOS broadband:

The LOS factor which was a hurdle in the First generation due to Line of Sight was fixed and with that Non Line of Sight Transmission was developed. Advanced signal processing techniques for development and improvement of the transmission and receptions of signals, and with use of mobile network transmission techniques the performance of the system compare to range and capacity was also increased. The antennas can be installed under some roof and even able to transmit signals. Many companies find out solutions to solve NLOS factor with CDMA, OFDM, and multi-antenna processing techniques.

Figure: 4 � Non Line of Sight transmission (Source: http://www.save9.com/telecoms/wimax-wireless-metropolitan-networks/)

Narrow Band WLL:

Figure: 5- Typical WLL system (Source: http://www.nortelnetworks.com/products/01/fwa/index.html#)

Wireless local loop was the first wireless application introduced for personal communications. This application was first used in the countries such as India, Russia, China, Indonesia and many more which was successful and was mainly used for voice telephony services. This system is based on CDMA (Code Division Multiple Access) and DECT (Digital Enhanced Cordless Telephony) [10]. AT & T in February, 1997 had made some developments on fixed wireless technology code named Project Angel. The main benefit of the system was that it was able to transfer two voice signals with a frequency of 1900 MHz and data rate of 128 kbps mainly used for personal communications services. But after 4 years this project was stopped by AT & T due to some reasons [10].

Emergence IEEE 802.16 group:

Broadband Wireless Access (WBA) is a unique concept which provides an easy access to the internet data transfer, voice transfer, and video services. The implementation of the antennas on high towers has given a boost to this technology networks in a very short duration to gain high transmission powers [14]. To develop and meet the demands IEEE 802.16 was formed in 1998 to specify the standards for the air transmission signals. Main focus was on developing the LOS wireless transmission system for working in frequency of 10GHz � 66 GHz [14]. A report was published by IEEE in December 2001, regarding the standards with respect to WMAN based on single carrier physical (PHY) layer with burst time division multiplexed (TDM) MAC layer. Both Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD) were supported by MAC layer and also adopted some designing concepts and standards from Data over Cable Service Interface Specification (DOCSIS).

Figure: 6 � IEEE 802.16 standards (Source: [10])

The second 802.16a was developed with minimizing the errors and doing some modifications having fixed NLOS applications operating in a frequency of 2GHz � 11GHz using a transmission scheme of OFDM (Orthogonal Frequency Division Multiplexing) having MAC architecture as point to multipoint [14]. The modulation used is Quadrature phase-shift keying (QPSK). With further modifications and developments in 2004 a new standard was launched named as IEEE 802.16-2004. This solution is also known as Fixed WiMax. Further developments and modifications lead to develop new standards named IEEE 802.16e-2005 which rectified the lack of IEEE 802.16-2004 compatibility with roaming applications. It standard is also called as Mobile WiMax because of its adaptability with both mobile and other wireless applications.

WiMax Forum:

The above table describes the standards maintained by the IEEE for wireless networks which has specified pre defined standards for wireless applications universally. Due to the demand and needs of the industry IEEE 802.16 was created and it has a lot of options too. For use of IEEE 802.16 in different systems and applications some parameters should be compromised and should be tested for its working. The main job of IEEE was to specify standards and not to check the compatibility of the standards with the applications. To complete this purpose IEEE introduced WiMax Forum in June, 2001. The main aim of the WiMax Forum is to check the compatibility of the standard IEEE 802.16/ETSI HiperMAN with the other applications and systems [8]. There are lot members in WiMax Forum mainly from companies, manufactures, and service providers and also on other hand it also does marketing of its products. There are two such points which should be followed by any one in order to get certified by WiMax for the use of the system or application.

? System Profile: The main of this profile is to set standards from IEEE 802.16d-2004 or IEEE 802.16e-2005 regarding physical and MAC layer. For IEEE 802.16-2004 (OFDM PHY layer) Fixed system profile and for IEEE 802.16-2005 (OFDMA PHY layer) Mobile system profile [10].

? Certification Profile: The main of this profile is to deal with the main parameters such as frequency, bandwidth, on which duplexing mode the system or application will work.

The first certified product by WiMax was launched on January 2006 [16] [17]. If we compare the working of Wi-Fi Alliance and WiMax Forum both have received acknowledgements regarding their works and also systems and applications testing for Wi-Fi products. By use of the WiMax certified products there can be a change in evolution of the applications used in wireless technologies.

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