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Wi-MAX | Wi Max | Internet Access

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WiMAX Author Balapure Bhushan R. Desle Vivek K. Gadhe Sandip D. Abstract – The IEEE 802.16 standard (now called WiMAX) has been proposed to provide last-mile connectivity to fixed locations by radio links. Despite this original objective, we study in this paper the functional parts of a WiMAX system and its basic operation and how WiMAX can use base stations to provide high speed data connections that can be used for voice, data and video services to distances of over 30 km. We find that seamle
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  WiMAX Author Balapure Bhushan R.Desle Vivek K.Gadhe Sandip D.   Abstract   – The IEEE 802.16 standard (now called WiMAX) hasbeen proposed to provide last-mile connectivity to fixed locationsby radio links. Despite this srcinal objective, we study in thispaper the functional parts of a WiMAX system and its basicoperation and how WiMAX can use base stations to provide highspeed data connections that can be used for voice, data and videoservices to distances of over 30 km. We find that seamlessconnection handoff can be achieved within the 802.16 standard byapplying some of the existing functionalities defined for theterminal initialization process. WiMAX protocols are designed toallow for point to point (PTP), point to multipoint (PMP) andmesh networks. In WiMAX expensive equipment are used asvarious versions of smart antennas, OFDM and sometimes meshto provide often effective alternatives to wired communications. I. I NTRODUCTION WiMAX is short for Worldwide Interoperability for Microwave Access, and it also goes by theIEEE name 802.16. WiMAX has the potential to do to broadband Internet accesswhat cell phones have done to phone access. In the same waythat many people have given up their land lines in favor of cell phones, WiMAX could replace cable and DSL services, providing universal Internet access just about anywhere yougo. WiMAX will also be as painless as Wi-Fi -- turning your computer on will automatically connect you to the closestavailable WiMAX antenna.The srcinal WiMAX system was designed to operate at 10-66 GHz and it had to change to offer broadband wireless access(BWA) in the 2-11 GHz frequency range. To do this, theWiMAX standard includes variants (profiles) that use differentcombinations of radio channel types (single carrier –vs-multicarrier), modulation types, channel coding types to provide fixed, nomadic or portable services.WiMAX can provide multiple types of services to the sameuser with different QoS ( Quality of Service) levels. For example, it is possible to install a single WiMAX transceiver inan office building and provide real time telephone services and best effort Internet browsing services on the same WiMAXconnection. To do this, WiMAX was designed to mixcontention based (competitive access) and contention free(polled access) to provide services which have different qualityof service (QoS) levels.  Goals of WiMAX  The goal of WiMAX is to provide high-speed Internet accessin a coverage range several kilometers in radius. In theory,WiMAX provides for speeds around 70 Mbps with a range of 50 kilometers. The WiMAX standard has the advantage of allowing wireless connections between a base transceiver station (BTS) and thousands of subscribers without requiringthat they be in a direct line of sight (LOS) with that station.This technology is called NLOS for non-line-of-sight. Inreality, WiMAX can only bypass small obstructions like treesor a house and cannot cross hills or large buildings. Whenobstructions are present, actual throughput might be under 20Mbps. Operating principle of WiMAX  At the heart of WiMAX technology is the base transceiver station, a central antenna which communicates withsubscribers' antennas. The term  point-multipoint link  is usedfor WiMAX's method of communication.The revisions of the IEEE 802.16 standard fall into twocategories:  Fixed WiMAX  , also called  IEEE 802.16-2004 , provides for afixed-line connection with an antenna mounted on a rooftop,like a TV antenna. Fixed WiMAX operates in the 2.5 GHz and3.5 GHz frequency bands, which require a license, as well asthe license-free 5.8 GHz band. Mobile WiMAX  , also called  IEEE 802.16e , allows mobileclient machines to be connected to the Internet. MobileWiMAX opens the doors to mobile phone use over IP, andeven high-speed mobile services. TABLE 1StandardFrequencySpeedRangeFixed WiMAX(802.16-2004)2-11 GHz (3.5GHz in Europe)75 Mbps10 kmMobileWiMAX (802.16e)2-6 GHz30 Mbps3.5 km II. H OW W IMAX W ORKS In practical terms, WiMAX would operate similar to Wi-Fi but at higher speeds, over greater distances and for a greater   number of users. WiMAX could potentially erase the suburbanand rural blackout areas that currently have no broadbandInternet access because phone andcablecompanies have not yet run the necessary wires to those remote locations.A WiMAX system consists of two parts:  A WiMAX tower, similar in concept to a cell-phone tower -A single WiMAX tower can provide coverage to a very largearea -- as big as 3,000 square miles (~8,000 square km).  A WiMAX receiver  - The receiver and antenna could be asmall box or  PCMCIA card   , or they could be built into a laptopthe way Wi-Fi access is today.A WiMAX tower station can connect directly to the Internetusing a high-bandwidth, wired connection (for example, a T3line). It can also connect to another WiMAX tower using aline-of-sight, microwave link. This connection to a secondtower (often referred to as a backhaul), along with the ability of a single tower to cover up to 3,000 square miles, is what allowsWiMAX to provide coverage to remote rural areas. Figure 2. How WiMAX Works What this points out is that WiMAX actually can providetwo forms of wireless service:There is the non-line-of-sight, Wi-Fi sort of service, where asmall antenna on your computer connects to the tower. In thismode, WiMAX uses a lower frequency range -- 2 GHz to 11GHz (similar to Wi-Fi). Lower-wavelength transmissions arenot as easily disrupted by physical obstructions -- they are better able to diffract, or bend, around obstacles.There is line-of-sight service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole.The line-of-sight connection is stronger and more stable, so it'sable to send a lot of data with fewer errors. Line-of-sighttransmissions use higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is lessinterference and lots more bandwidth.Wi-Fi-style access will be limited to a 4-to-6 mile radius(perhaps 25 square miles or 65 square km of coverage, whichis similar in range to a cell-phone zone). Through the stronger line-of-sight antennas, the WiMAX transmitting station wouldsend data to WiMAX-enabled computers or routersset upwithin the transmitter's 30-mile radius (2,800 square miles or 9,300 square km of coverage). This is what allows WiMAX toachieve its maximum range. III. P ROTOCOLS F OR  C ONNECTION H ANDOFF  Handoff Objective and Mobility Management:- As the quality of an established radio link between asubscriber station (SS) (or terminal) and its BS deteriorates dueto mobility, the objective of handing off the connection to aneighboring BS is to maintain the IP connectivity between theSS and the corresponding host. A major goal is to minimize packet loss and delay induced by the handoff process. Since the802.16d standard defines only the physical (PHY) and MAClayers, without loss of generality, suppose that the network under study employs the hierarchical mobile IP (HMIP)algorithm [GJP02] for micro-mobility management. (Similar observations apply to other mobility management algorithmssuch as [CGK02] and [RVS02].) Using the commonterminology for mobile networks, Figure 1 shows thearchitecture of the HMIP for the 802.16 network under consideration. Specifically, one router is designated thePrimary Foreign Agent (PFA) and serves as the “anchor point”for each SS (or connection). That is data from and to a givenSS always goes through the corresponding PFA. In addition,the PFA also keeps track of the operational parameters for the802.16d connections associated with the SS. As shown in thefigure, the communication path consists of multiple IP tunnelsand packets are forwarded by tunneling. Figure 6. Hierarchical Mobile IP for 802.16d Network  IV. W IMAX S  YSTEM  T  YPES  some of the different types of uses that WiMaxnetworks can provide. That is:1)Point to Point (PTP)2)Point to Multipoint (PTMP)This diagram shows that WiMax systems can beused for point-to-point links, residentialbroadband or high-speed business connections. This example shows that the point to point (PTP)connection may be independent from all othersystems or networks. The point to multipoint(PTMP) system allows a radio system to provideservices to multiple users. WiMax systems canalso be setup as mesh networks allowing theWiMax system to forward packets between basestations and subscribers without having to installcommunication lines between base stations. Figure 3. WiMAX system types V. W IMAX S  TANDARDS E VOLUTION 802.16 broadband wireless systems have evolved withdifferent standard over time.This diagram shows that the srcinal 802.16 specificationdefined fixed broadband wireless service that operates in the10-66 GHz frequency band. To provide wireless broadbandservice in lower frequency range, the 802.16A specificationwas created that operates in the 2-11 GHz frequency band. To provide both fixed and mobile service, the 802.16Especification was developed. Figure 4. WiMAX standards evolution WiMAX Standard Differences:- This figure shows a comparison between the srcinal FixedWiMAX standard and the WiMAX standard that can be usedfor fixed, mobile and portable. This table shows that thesrcinal 802.16 standard was released in 2004 and it was onlycapable of providing fixed wireless data services. It usedOFDM modulation and could be deployed in both TDD or FDD formats. The 802.16e standard was released in 2005 (nowmerged into the srcinal 802.16 standard) was designed for fixed, mobile and portable operation. It used OFDMAmodulation with TDD and optionally FDD duplexingcapability. Figure 5. WiMAX standards difference WiMAX Radio Channel Types :-This figure shows that WiMAX radio channels can be singlecarrier or multiple carriers. This diagram shows that the bandwidth of WiMAX radio channels can vary from 1.25 MHzto 28 MHz in steps of 1.75 MHz. This example also shows thata WiMAX system that is using multicarrier OFDMA and howsome of the subcarriers have been assigned to a specific user.  Figure 7. WiMAX  Radio Channel    Types VI. W iMAX O VER O  THER  T ECHNOLOGIES Wi-Fi:- The WiMAX Forum is keen to present 802.16 ascomplementary to the local area IEEE standard, 802.11 or Wi-Fi. In many ways, this is right—802.16a, as we have seen, provides a low cost way to backhaul Wi-Fi hotspots andWLAN points in businesses and homes, and as uptake of Wi-Fiincreases, the requirement for this backhaul will grow too.But there is conflict too. WiMAX makes redundant theefforts of Wi-Fi specialists to extend the reach of their favourite technology and also places 802.11 into a far smaller role than its supporters have, often unrealistically, carved outfor it. This is the opportunity for wireless technologies finallyto grow up and offer the speed, multimedia support andubiquity that Wi-Fi can never deliver.The newer standard holds all the real power. By providing a backbone for hotspots, based on standards rather than thevarious proprietary WLAN expansion technologies out there, itMakes the idea of a ubiquitous wireless network to rivalcellular far more realistic than it ever was with Wi-Fi alone,despite the claims of the enthusiasts. The equipment makersare eyeing it keenly – amid all the doubts about thesustainability of the hotspot boom, anything that offers them anew product line plus helps to preserve the interest in Wi-Fi isto be welcomed.802.16 is a highly complex standard which contains, fromday one, many of the features that are being retrofitted, withvarious degrees of clumsiness and baggage, into Wi-Fi, whichwas srcinally conceived to be very simple and is now takingon a burden of responsibility beyond its technological reach.WiMAX has the advantage of not being – at least until Intelhas a long distance Centrino – a consumer technology.Although this has kept its profile lower than Wi-Fi’s, it has notsuffered from the over-hype and its development is freer of vendor politics and posturing than its short distance cousin’s. Cellular Technologies:- WiMAX is a serious threat to 3G because of its broadbandcapabilities, distance capabilities and ability to support voiceeffectively with full QoS. This makes it an alternative tocellular in a way that Wi-Fi can never be, so that whileoperators are integrating Wi-Fi into their offerings with somealacrity, looking to control both the licensed spectrum and theunlicensed hotspots, they will have more problemsaccommodating WiMAX. But as with Wi-Fi, it will be better for them to cannibalize their own networks than letindependents do it for them, especially as economics and performance demands force them to incorporate IP into their systems. Handset makers such as Nokia will be banking on thisas they develop smart phones that support WiMAX as well as3G.  Relationship With Other Wireless Technologies:-  TABLE 2  BWA alternatives to WiMAX:-  Not everyone is taking the WiMAX pledge though. Flarionis the leader among OFDM-based vendors that are backing themetro area mobile wireless standard, 802.20 or Mobile-Fi,instead.IPWireless supports neither IEEE approach, but is still pushing its own mobile broadband technology, which is basedon an IP packet data implementation of the UMTS 3Gstandard, operating at over 2.5 miles in urban areas at 16Mbpsin 5MHz and 10GMz channels.This technology is less powerful or long distance thanWiMAX, though it does have the advantage, especially for second tier mobile operators, of being similar to cellular networks to implement and manage and providing goodinteroperability with the various flavours of 3G. Its naturalhome, then, is in extending the networks of the mobile carriersin outlying regions, but it is keen to attack the hotspot sector too, an ambition that will be hard to realize in the face of WiMAX.However, the case that the company’s chief executive, ChrisGilbert, makes for IPWireless over Wi-Fi hotspots is valid for all BWA technologies. He points out that users will not want tohave to hunt for hotspots, and that broadband alternatives canoffer not only longer distances from the base station, but alsomobility – as supported by IPWireless and by the mobileversion of WiMAX, 802.16e.Another backhaul option that has gained coverage recently isfree space optical, a technology that is primarily used to extendlocal fiber networks but can also be used for backhaul. Onesupplier specifically targeting this new direction is Omnilux.FSO is more expensive than wireless - $1,500 per node for  3GWi-Fi:802.11WiMAX802.16Mobile-Fi802.20:Maxspeed2Mbps54Mbps100Mbps16MbpsCoverageSeveralmiles300 feet50 milesSeveralmilesAirwaveLicensedUn-licensedEitherLicensedAdvantagesRange,mobilitySpeed, priceSpeed,rangeSpeed,mobilityDisadvantagesSlow,ExpensiveShortrangeInterference issues?High price
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