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5 wimax3424

  1. 1. manasa066@gmail.com BRAHMAIAH COLLEGE OF ENGINEERING A Paper presentation on… Wi-max By D.ANUSHA R.MANASA III B.Tech-II SEMISTER. ROLL: 092M1A0406 BCEN Engineering College NH-5,N.R. palem,SPSR NELLORE (Dist.). 524366 Mobile no:+91- 9989741124 III B.Tech-II SEMISTER. ROLL: 092M1A0424 BCEN Engineering College NH-5,N.R. palem,SPSR NELLORE (Dist.). 524366 Mobile no:+91-9440637769 e-mail : manasa066@gmail.com e-mail: anushadevireddyece@gmail.com, 1
  2. 2. “WiMAX” - Emerging wireless technology ABSTRACT New and increasingly advanced data services are driving up wireless traffic, which is being further boosted by growth in voice applications in advanced market segments as the migration from fixed to mobile voice continues. This is already putting pressure on some networks and may be leading to difficulties in maintaining acceptable levels of service to subscribers. For the past few decades the lower band width applications are growing but the growth of broad band additional features in physical layer data applications is slow. Hence we and MAC layer and the benefits of require technology which helps in the each feature. growth of the broad band data This paper focuses on applications. WiMAX is such a technology which helps in point-tomultipoint broadband wireless access with out the need of direct line of sight connectivity with base station. the major technical comparisons (like QOS and coverage) between WiMAX and other technologies. It also explains about the ability of the WiMAX to provide efficient service This paper explains about the WiMAX technology, its in multipath environment.
  3. 3. broadband connectivity without the need for Direct line-of-sight with a base station. III.What is wimax? WiMAX is an acronym that stands for “Worldwide II. Introduction: Interoperability group number 16 of IEEE 802, decades, low-bandwidth applications specializing such as downloading ring tones and email point-to-multipoint known as WiMAX. There are at least but the growth of broadband data as in broadband wireless access. It also is SMS are experiencing sharp growth, such Microwave Access”. IEEE 802.16 is working For the past couple applications for four 802.16 standards: 802.16, 802.16a, and 802.16-2004 (802.16), and 802.16e. downloading/ uploading files with a WiMAX laptop computer or PDA has been slow. The demand for broadband conflict access complements it. continues to escalate with WiFi does but not actually WiMAX is a worldwide and lower-bandwidth wire wireless metropolitan area network line methods have failed to satisfy the (MAN) technology that will connect need for higher bandwidth integrated IEEE 802.11 (WiFi) hotspots to the data and voice services. WiMAX is Internet radio technology that promises two- extension to cable and DSL for last way several km broadband access. IEEE 802.16 megabits per second with ranges of provides up to 50 km of linear several miles. It is believed that the service technology DSL connectivity without a direct line of (Digital Subscriber Line) and cable sight to a base station. The technology broadband services because it offers also provides shared data rates up to similar speeds but is less expensive to 70 Mbit/s. Internet access can at challenge set up. The intention for WiMAX is to Mobile provide a wireless area range and allows user’s The portable version of provide fixed, nomadic, portable and, eventually, and WiMAX, wireless 3 IEEE 802.16 utilizes
  4. 4. Orthogonal Frequency Division Multiplexing Access (OFDM/OFDMA) where the spectrum is divided into many subcarriers. Each sub-carrier then uses QPSK or QAM for modulation. WiMAX standard relies mainly on spectrum in the 2 to 11 GHz range. The WiMAX specification improves upon many of the limitations of the WiFi standard by providing increased bandwidth and stronger encryption In reviewing the standard, the technical details and For years, the wildly features that differentiate WiMAX successful 802.11 x or WiFi wireless certified equipment from WiFi or LAN technology has been used in other BWA applications. When the WLAN technologies can best be illustrated by focusing on the two technology was examined closely, it layers addressed in the standard, the was evident that the overall design physical (PHY) and the media access and feature set available was not well control (MAC) layer design. suited for outdoor Broadband wireless access (BWA) applications. WiMAX III. a) WIMAX PHY Layer: is suited for both indoor and outdoor BWA; hence it solves the major The first version of the problem. 802.16 standard released addressed Line-of-Sight (LOS) environments at high frequency bands operating in the 10-66 GHz range, whereas the recently adopted amendment, the 802.16a standard, is designed for systems operating in bands between 2 GHz and 11 GHz. The significant difference between these two frequency bands lies in the ability to 4
  5. 5. support Non-Line -of-Sight (NLOS) of the PHY layer features of the IEEE operation in the lower frequencies, 802.16a standard. something that is not possible in higher bands. Consequently, the 802.16a amendment to the standard opened up the opportunity for major changes to the PHY layer specifications specifically to address the needs of the 2-11 GHz bands. This is achieved through the introduction of three new PHY-layer specifications (a new Single Carrier PHY, a 256 point FFT OFDM PHY, and a 2048 point FFT OFDMA PHY); Some of the other PHY layer features of 802.16a that are instrumental in giving this technology the power to deliver robust performance in a broad range of channel environments are; flexible channel widths, adaptive burst profiles, forward error correction with concatenated Reed-Solomon and convolutional encoding, optional AAS (advanced antenna systems) improve range/capacity, to DFS (dynamic frequency selection)-which helps in minimizing interference, and STC (space-time coding) to enhance performance in fading environments through spatial diversity. Table 1 gives a high level overview of some 5
  6. 6. b) IEEE 802.16a MAC Layer:The 802.16a standard uses a slotted TDMA protocol scheduled by the base station to allocate capacity to subscribers in a point-to-multipoint network topology. By tarting with a TDMA approach with intelligent scheduling, WiMAX systems will be able to deliver not only high speed data with SLAs, but latency sensitive services such as voice and video or database access are also supported. The standard delivers QoS beyond mere prioritization, a technique that is very limited in effectiveness as traffic load and the number of subscriber’s increases. The MAC layer in 6
  7. 7. WiMAX certified systems has also been designed to address the harsh physical layer environment where interference, fast fading and other phenomena are prevalent in outdoor operation. 802.11 MAC was never designed for and is incapable of supporting. a) Coverage: IV.WiMAX Scalability: The BWA standard is At the PHY layer the designed for optimal performance in standard supports flexible RF channel bandwidths and reuse of all types of propagation environments, these including LOS, near LOS and NLOS channels (frequency reuse) as a way to environments, and delivers reliable increase cell capacity as the network robust performance even in cases grows. The standard also specifies where extreme link pathologies have support for automatic transmit power control and measurements layer tools channel been introduced. The robust OFDM quality waveform as additional PHY to support planning/deployment and spectrum cell efficient single STC, (mesh Advanced networks) and antenna diversity) can be employed to improve coverage even further. These advanced techniques can also be used to increase spectral CSMA/CA foundation of 802.11, efficiency, basically a wireless Ethernet protocol, capacity, reuse, and average and peak throughput per RF scales about as well as does Ethernet. channel. In addition, not all OFDM is That is to say - poorly. Just as in an the same. The OFDM designed for Ethernet LAN, more users results in a BWA has in it the ability to support geometric reduction of throughput, so MAC channel. antenna techniques (beam-forming, In the MAC layer, the CSMA/CA RF topologies through number of subscribers grows. the spectral kilometers with up to 70 Mbps in a sectorization and cell splitting as the does high efficiency over ranges from 2 to 40 spectrum use. Operators can reallocate supports longer range transmissions and the for multi-path or reflections encountered. WLANs. In contrast the MAC layer in In contrast, WLANs and 802.11 the 802.16 standard has been designed systems have at their core either a to scale from one up to 100's of users basic CDMA approach or use OFDM within one RF channel, a feat the with a much different design, and 7
  8. 8. have as a requirement low power implementation will never be able to consumption deliver the QoS of a BWA, 802.16 limiting the range. OFDM in the WLAN was created systems. with the vision of the systems covering tens and maybe a few V. ROLE OF ‘OFDMA’ IN hundreds of meters versus 802.16 which is designed for higher power MULTIPATH and an OFDM approach that supports ENIRONMENT: deployments in the tens of kilometers. b) Quality of service: The 802.16a MAC relies on a Grant/Request protocol for access to the medium and it supports differentiated service The protocol employs TDM data streams on the DL (downlink) and TDMA on the UL (uplink), with the hooks for a Technologies centralized scheduler to support delay- using sensitive services like voice and DSSS (802.11b, CDMA) and other video. By assuring collision-free data wide band technologies are very access to the channel, the 16a MAC susceptible to multipath fading, since improves total system throughput and the delay time can easily exceed the bandwidth efficiency, in comparison symbol duration, which causes the with access symbols to completely overlap (ISI). CSMA-CA The use of several parallel sub- protocol used in WLANs. The 16a carriers for OFDMA enables much MAC also assures bounded delay on longer symbol duration, which makes the data. The TDM/TDMA access the signal more robust to multipath technique also ensures easier support time dispersion contention-based techniques like the for multicast and broadcast services. a). Multipath: Frequency Selective With a CSMA/CA approach at its core, WLANs in their Fading current 8
  9. 9. This type of fading affects certain VI. frequencies Modulation and Coding (AMC): of a OFDMA with Adaptive transmission and can result in deep fading at certain frequencies. One reason this occurs is because of the wide band nature of the signals. When a signal is reflected off a surface, different frequencies will reflect in different ways. In Figure below, both CDMA (left) and OFDMA (right) experience selective fading near the center of the band. With optimal channel coding and interleaving, these errors can be corrected. CDMA tries to overcome this by spreading the signal out and then equalizing the whole signal. OFDMA is therefore much more resilient to frequency Both selective fading when compared to (HSDPA) and CDMA. Quadrature Phase W-CDMA OFDM utilize Shift Keying (QPSK) and Quadrature Amplitude Modulation (QAM). It should be noted here that for WCDMA, AMC is only used on the downlink, since the uplink still relies on WCDMA which uses QPSK but not QAM. Modulation and coding rates can be changed to achieve higher throughput, but higher order modulation will require better Signal to illustrates Noise Ratio. Figure how higher order modulations like QAM 64 are used closer to the base station, while lower 9
  10. 10. order modulations like QPSK are used In Figure below, you to extend the range of the base can see how sub-channels could be station results chosen depending on the received conducted for one of the 3GPP signal strength. The sub-channels on Working Groups [2], show that while which OFDM the significant fading are avoided and maximum throughput of 9.6 Mbps power is concentrated on channels (16QAM), WCDMA does not exceed with better channel conditions. The 3 Mbps. From these results, it appears signals on the top indicate the that even higher discrepancy may be received signal strength, while the found higher bottom part of the figure indicates modulation and code rates to yield which sub-carriers are then chosen for even higher throughput for OFDM. each signal. . is Performance able when to achieve utilizing the user Adaptive Modulation and Coding (AMC) With OFDMA, choose sub client give OFDMA channels based further advantages since the flexibility locations with to change the modulation for specific eliminating the impact of deep fades. sub-channels allows you to optimize CDMA-based technologies utilize the at same frequency band regardless of the frequency level. Another alternative would be to assign those could the multipath may device experiencing a environment in is where the user is. sub channels to a different user who may have better channel conditions for that particular sub-channel. This could allow users to concentrate transmit power on specific subchannels, resulting in improvements to the uplink budget and providing greater range. This technique is known as Space Division Multiple Access (SDMA). 10 on the geographical potential of
  11. 11. VII.ADVANCED TECHNIQUES: RADIO a) Transmit and receive diversity schemes: Transmit and Receive Diversity schemes are used to take advantage of multipath and reflected signals that occur in Adaptive NLOS antenna environments. By utilizing multiple systems (AAS) are an optional part of antennas (transmit and/or receive), the 802.16 standard. AAS equipped fading, interference and path loss can base stations can create beams that be reduced. The OFDMA transmit can be steered, focusing the transmit diversity option uses space time energy to achieve greater range as coding. diversity, shown in the figure. When receiving, techniques such as maximum ratio they can focus in the particular combining (MRC) take advantage of direction of the receiver. This helps two separate receive paths. eliminate unwanted interference from For receive other locations. VIII. Conclusion: Thus WiMAX systems for portable/nomadic use will have better performance, interference rejection, multipath tolerance, high data quality of service support (data oriented MAC, symmetric link) and lower future equipment costs i.e., low chipset complexity, high spectral efficiencies. And hence WiMAX can complement existing and emerging 3G mobile and wireline networks, and b) Smart Antenna Technology: play a significant role in helping 11
  12. 12. • service provides deliver converged service offerings V.Poornima, III/IV B-tech, E.C.E, IX. BIBLIOGRAPHY: L.B.R.College of Engineering , MYLAVARAM.  Understanding “WiMAX”- Joe E-MAIL ADDRESS: Laslo & Michael gartenberg v_poornima06@yahoo.co.in  www.intel.com/ebusiness/pdf/w ireless/intel Residential Address:  www.intel.com/netcomms/techn P.Tabitha Priyadarshini, ologies/wimax D/o P.Venkata Ratnam,  P. S. Henry, “Wi-Fi: What’s Door no- 21-171, next?” IEEE Communications Santhinagar, Main road, Magazine Tiruvuru. – 521235 (Krishna dst.)  WWW.WiMaxeed.COM.  WiMAX Handbook –Frank PHONE: 9848783201 ohrtman College Address: L.B.R College of Engineering , L.B.R.nagar, MYLAVAM. AUTHORS : • P.Tabitha Priyadarshini, III/IV B-tech, E.C.E, L.B.R. College of Engineering, MYLAVARAM. E-MAIL ADDRESS: p_tabitha86@yahoo.co.in 12 (Krishna dst. A.P)

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