WiMAX (Worldwide Interoperability for Microwave Access) is the next step on the path to a wireless world, extending broadband wireless access to new areas and over farther distances, as well as considerably reducing the expenditure of deploying broadband to new locations. WiMAX is a wireless digital communications system, also known as IEEE 802.16 that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3- 10 miles (5 -15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 -300 feet (30 - 100m). WiMAX is the industry term for a long-range networking standard. WiMAX technology has potential to deliver the high-speed Internet access to rural areas and other locations not serviced by cable or DSL technology. WiMax offers an alternative to satellite Internet services.
Seminar Report On WiMAX Submitted by: SAVITHA K.S Reg. No. 56437 2005-2006
WiMAX (Worldwide Interoperability for Microwave Access) is the step on path to a wireless world, extending broadband wireless access to new areas and over farther distances, as as considerably reducing the expenditure of deploying broadband to new locations. WiMAX is a wireless digital communications system, also known as I 16 that is intended for "metropolitan area networks". WiMAX can provide broadband access (8WA) up to 30 miles (50 km) for fixed stations, and 3 10 miles -15 km) for mobile stations. In contrast, the WiFi/B02.11 wireless local area network standard is limited in most cases to only 100 -300 (30 100m). WiMAX is the industry term for a long-range networking standard. WiMAX technology has potential deliver the high-speed Internet access to rural areas and other locations not by or DSL technology. WiMax offers an alternative to satellite Internet services.
2. WIRELESS NETWORKING The term wireless networking refers to technology that enables two or more computers to communicate using standard network protocols but without network cabling. Strictly speaking, any technology that does this could be called wireless networking. The current buzzword however generally refers to wireless LANs.This technology, fuelled by the emergence of cross-vendo industry standards such as IEEE 802.11, has produced a number of affordable wireless solutions that are growing in popularity with business and schools as well as sophisticated applications where network wiring is impossible, such as in warehousing or point-of-sale handheld equipment. There are two kinds of wireless networks: <8 An ad-hoc or peer-to-peer wireless network consists of a number of computers each equipped with a wireless networking interface card. Each computer can communicate directly with all of the other wireless enabled computers. They can share files and printers this way, but may not able to access wired LAN resources unless one of the computers acts as bridge to the wired LAN using special software (this is called "bridging"). <8 A wireless network can also use an access point or base station. In this type of network the access point acts like a hub, connectivity for the wireless computers. It can connect or bridge the wireless LAN to a wired LAN allowing wireless computer access to LAN resources such as file servers or existing internet connectivity.
There are two types of access points: Â¢ Dedicated hardware access points such as Lucent's WaveLAN, Apple's Airport Base Station or Web Gear's Aviator PRO. Â¢ Software access points which run on a computer equipped with a wireless network interface path as used in adhoc or peer to peer wireless network.
IEEE WIRELESS COMMUNICATIONS STANDARDS 3.1 802.11
Working Group for Wireless Local Area Networks are standards 11 specify an the -year" interface a wireless client and a base station or access point, as well as among wireless clients. The 802.11 can be compared to 802.3 standard for Ethernet for wired LANs. The IEEE 802.11 specifications address both the Physical (PHY) and Medium Control (MAC) layers and between manufactures are tailored compatibility of 3.2 802.15 Working Group for wireless Personal Area Networks The 802.15 Working Group in the IEEE 802 family, for low complexity low power consumption wireless In March 1998, Wireless Personal Network (WPAN) study group was . In May 1998, Bluetooth Group (SIG) was formed, and in May 1999 the WPAN Study Group 802.15, the WPAN Working In July 1999, Bluetooth the Bluetooth Specification v1 3.3 802.16 Working Group for Broadband Wireless Access Standards 16 specifications support development of fixed broadband access systems to rapid world wide deployment of innovative, cost -effective interoperable multi-vendor broadband wireless access products.
3.4 P1451.5 Working Group for Wireless Sensor Standards Many companies are developing various wireless communication interfaces and protocols for sensors. An openly defined wireless transducer communication standard, that can accommodate various existing wireless technologies, will reduce risk for users, transducer manufacturers, and system integrators. It will enhance the acceptance of the wireless technology for transducers connectivity. The standard will define Transducer Electronic Data Sheets (TEDS) based on the IEEE 1451 concept, and the protocols to access TEDS and transducer data. It will adopt necessary wireless interfaces and protocols to facilitate the use of technically differentiated, existing wireless technology solutions. It will not specify transducer design signal conditioning, wireless system physical design or use, or use of TEDS. WiF" 801. Bluetooth 801 '
WiMAX 4. 802.16 STANDARD 4.1
THE 802.16 WORKING GROUP Development of IEEE standard 802.16 and the included wireless MAN air interface along with associated standards amendments,is the responsibility of IEEE Working group 802.16 on Broadband wireless access (BWA) standards. The working group's initial interest was the 10-66 GHz range. The 2-11 GHz amendment project that led to IEEE 802.16a was approved in march 2000. The 802.16a project primarily involves the development of new physical layer specification with supporting enhancements to the basic MAC. In addition the working group has completed IEEE standard 802.16.2 . ( " Recommended Practice for Coexistence of Fixed Broadband Wireless Access Systems") to address 1 0-66 GHz coexistence and, through the amendment project 802.16.2a is expanding its recommendations to include the licensed bands from 2 to 11 GHz. 4.2 LAYERS OF 802.16 MEDIUM ACCESS CONTROL The IEEE 802.16 protocol was designed for point to multipoint broadband wireless access applications. It addresses the need for very high bit rates,both the uplink (to the BS) and the downlink (from the BS). Access and bandwidth allocation algorithms must accommodate hundreds of terminals per channel, with terminals that may be shared with the multiple end users. The services required by these end users are varied in their nature and include legacy time division multiplexing (TOM) voice and data, Internet protocol (IP) connectivity, and packetized voice over IP (VoIP). To support this variety of services the 802.16 MAC must accommodate both the continuous and the bursty traffic. Additionally these services expect to be
WiMAX with traffic types.The 802.16 ,.,.,..,..",H.n assigned QoS in the wide analogous the asynchronous transfer (ATM) service categories as well as newer categories such as frame rate (GFR). The 802.16 MAC protocol must also support a variety of backhaul requirements including both asynchronous transfer (ATM) and packet based convergence sub layers are to map the transport layer traffic to a MAC that is flexible Through such enough to efficiently carry any as payload header packing and fragmentation, convergence sub layers and MAC work together to carry traffic in a form that is often more than the original tra mechanism. Along the fundamental task of allocating bandwidth transporting data, the MAC includes a privacy sub layer that provides the authentication network access and connection establishment to avoid theft of and it provides key and encryption for data privacy. To accommodate more demanding physical environment and different requirements of the frequencies 2 and 11 GHz, the 802.16a project upgrading the MAC to provide automatic request (ARQ) and support mesh, rather than the only point multipoint, network architectures.
WiMAX THE PHYSICAL LAYER 10-66 GHz-In the design of the PHY specification for 10-66 GHz, line-of-sight propagation was deemed a -practical necessity. With this condition assumed, single -carrier modulation was easily selected; the air interface is designated-ed "Wireless MAN-Sen. Many fundamental design challenges remained, however. Because of the point-multipoint architecture, the BS basically transmits a TOM signal with individual subscriber stations allocated time slots serially. Access in the uplink direction is by time-division multiple accesses (TOMA). Following extensive discussions regarding duplexing, a burst design was selected that allows both time-division duplexing(TOO) , in which the uplink and the downlink share a channel but it do not transmit simultaneously and the FOO in which the uplink and the downlink operate on separate channels, sometimes simultaneously. This burst design allows both TOO and FOO to be handled in a similar fashion. Support for half duplex FO subscriber stations, which may be less expensive since they does not simultaneously transmit and receive is added at the expense of some slight complexity. Both TOO and FDD alternatives support adaptive burst profiles in which modulation,coding options may be dynamically assigned on a burst by burst basis. 2-11 GHz: -the 2-11 GHz bands both licensed and license exempt are addressed in IEEE projectB02.16a.The standard is in ballot not yet complete. The draft currently specifies that compliant systems implement one of three air interfaced specifications, each of which provide for interoperabilityDesign of the 2-11 GHz physical layer is driven by the need for the non line of sight (NLOS) operation. Because residential applications are expected, roof tops may be too low for a clear sight line to a BS antenna, possibly due to the
WiMAX obstruction by trees. Therefore, significant multipath propagations must be expected. Furthermore, outdoor -mounted antennas are expensive due to both hardware and installation costs. The three 2-11 GHz air interface specifications in 802.16a are: -Wireless MAN SC-2: This uses a single carrier modulation format. -Wireless MAN-OFDM: This uses orthogonal frequency division multiplexing with a 256 point transform. Access is by TDMA.This air interface is mandatory for license exempt bands. -Wireless MAN-OFDMA: This uses orthogonal frequency division multiple access with 2048 point transform. In this system multiple access is provided by addressing a sub set of multiple carriers to individual receivers. Because of the propagation requirements, the use of advanced antenna systems is supported. 4.3.802.16: what features it supports WiMAX supports both time division duplex and frequency division duplex (FDD) modes of operation on air, along with a range of channel bandwidths. The OFDM PHY mode, which is also known Wireless MAN-OFDM, is specified for use between 2 and 11 GHz. The 802.16 MAC controls access of the BS and SSs to the air through a rich set of features. The on-air tuning is based on consecutive frames that are divided into slots. The size of frames and the size of individual slots within the frames can be varied on a frame-by-frame basis,under the control of a scheduler in the BS. This allows the effective allocation of on -air resources to meet the demands of the active connections with their granted QoS properties.
802.16 MAC provides a connection oriented to upper of the protocol Connections that are granted and by the MAC. connections can by the SS making to the to them while a connection is maintained. service in the 802.16 MAC takes one of four forms: bit rate grant,real polling,non real time polling and best effort-Media access control packet units (MPDUs) are transmitted on -PHY slots. MPDUs , the MAC service units (MSDUs) are MSDUs are packets the top of the MAC layer above . MPDUs are the transferred between the bottom of the MAC and the PHY layer below. . Within MPDUs MPDUs, MSDUs can be , MSDus can (aggregated) . of MSDUs can be packed within a single packed MPDU. Automatic retransmission request(ARQ) can be used to request retransmission of the unfragmented MSDUs and fragments of MSDUs. nOI"Tl"\rrnc authentication, key MAC a privacy sub that encryption of MPDUs. of the 802.16 protocoi is shown is Figure. Computerscience
MAC Convergence Sub layer (ATM Ethernet 802.1Q.IP) MAC MAC Privacy Sub layer Physical Layer ATM Ethernet 802.1 Q I nternet Protocol Packing Fragmentation ARQ OoS Authentication Key Exchange Privacy (encryption) OFDM, ranging, Power control, DFS Figure: Diagram illustrating the layers of 802.16 protocol
Through the use of flexible PHY modulation and coding options, flexible frame and slot allocations, flexible OoS mechanisms, packing, fragmentation and ARO, the 802.16 standard can be used to deliver broadband voice and data into cells that may have a wide range of properties. This includes a wide range of population densities, a wide range of cell radii and a wide range of propagations environments. Convergence sub layers at the top of the MAC enable Ethernet, ATM,TDM voice and IP(lnternet Protocol) services to be offered over 802.16.
5. CORE COMPONENTS OF WIMAX SYSTEM Designed from the Group Up for Metropolitan Area Networks: In January 2003 , the IEEE approved the 802.16 a standard which covers frequency bands between 2GHz and 11 GHz .This standard is an extension of the IEEE 802.16 standard for 10-66 GHz published in April 2002. These sub11 GHz frequency ranges enable non line-ofsight performance, making the IEEE802.16a standard the appropriate technology for last-mile applications where obstacles like trees and buildings are often present and where the base stations may need to be unobtrusively mounted on the roofs of homes or building rather than towers on mountains. The core components of WiMAX system are the subscriber station( SS) otherwise known as the CPE and the base station (BS ).A BS and one more SSs can form a cell with a point-to-multipoint (P2MP) structure. On air, the BS controls actively within the cell, including access to the medium by SSs, allocations to achieve the quality of service (OoS) and admission to the network based on network security mechanisms.
SYSTtM An 802.16-based system often uses fixed antenna at the subscriber station site. The antenna is mounted to the roof or an eave. Provisions such as adaptive antenna systems (AAS) and subchannelization are also supported optionally by the standard for enhanced link budget required for in-door installation. IEEE 802.16e sub-committee is currently working on extension power limited SS terminals. A BS typically uses either sectored/directional or omni~directional antennas. A fixed SS typically uses directional antenna while mobile or portable SS usually uses an omni-directional antenna. Multiple BSs can be configured to form a cellular wireless network. When the Orthogonal Frequency Division Multiplexing (OFDM) is used, the cell radius can ideally reach up to 30 miles, however this requires a favorable channel environment and only the lowest data rate can be achieved. Practical cell sizes usually have a small radius of around 5 miles or less. The 802.16 standard also can
be used in a point-to-point (P2P) or mesh topology, using pairs of directional antennas. WiMax base stations will have the ability to provide approximately 60 businesses with T1 access and hundreds of homes with DSLlCable speed access in theory. Engineers are stating that WiMax has the capability of reaching 30 Miles but real world testing has shown 4-8 mile working radius. WiMax line of sight antennas operate at a higher Frequency up to 66mhz. Distribution antennas do not have to be in the line of sight with their clients . Non line of sight towers operate on a range similar to Wi-Fi . WiMax can operate right next to cell phone towers with no interference. HOW WIMAX WORKS J
WiMAX With shared rates up to 75 Mbps ,a single "sector" of an 802.16a base station-where sector is defined as a single transmiUreceive radio pair at the base station-provides sufficient band width to simultaneously support more than 60 business with T1-level connectivity and hundreds of homes with the DSL rate connectivity, using 20 MHz of the channel bandwidth. To support a profitable business model, operators and service providers need to sustain a mix of high revenue business customers and the high volume residential subscribers. 802.16a helps meet this requirement by supporting the differentiated service levels, which can include guaranteed T1 level services for business, or best effort DSL-speed service for home consumers. The 802.16 specification also includes robust security features and the Quality of Service needed to support services that require low latency, such as voice and video. 802.16 voice service can either be the traditional Time Division Multiplexed (TOM) voice or Voice over IP (VoIP).
6, WiMAX FORUM WiMAX Forum may be as the exclusive organization dedicated to certifying the interoperability of BWA products, the WiMAX defines and conducts conformance and the interoperability ensure that different vendor systems work seamlessly with one another.The WiMax Forum to support wireless metropolitan-area networking products based on the 16, much as the Wi-Fi Alliance has done for LANs and 11. that pass conformance and interoperability achieve the "WiMAX Forum Certified" designation and display mark on products and the marketing materials. Vendors claiming their equipment is that 'WiMAX-ready," "WiMAX-compliant," "pre-WiMAX," are not WiMAX Forum Certified, according to the Forum. WiMAX is defined as Worldwide Interoperability for Microwave ''''''-',,,..::>..::> by the WiMAX Forum, April 2001 to promote conformance and interoperability of the standard 802.1 The Forum describes WiMAX as" a standards-based technology enabling the delivery of mile wireless broadband access as an alternative to and DSL." The WiMAX Forum ,working to facilitate the deployment of broadband wireless networks based on the I 802.16 standard by helping to ensure the compatibility and interoperability of broadband access equipment.The organization is a nonprofit association formed in June 2001 by equipment and component suppliers for promoting adoption of I 802.16 compliant equipment by operators of broadband wireless access systems.
Principles: WiMAX Forum is comprised of the industry leaders who are committed to the open interoperability of all products used for broadband wireless access. Â¢ Support IEEE 802.16 standard Â¢ Propose and promote access profiles for their IEEE 802.16 standard Â¢ Certify interoperability levels both in network and the cell Â¢ Achieve global acceptance Â¢ Promote IJse of broadband wireless access overall The WiMAX Forum is the only organization bringing compliance and interoperability to wireless broadband industry with testing and certification program, WiMAX Forum Certified. Why WiMAX Forum Certified? Today every solution is custom and not interoperable. Every piece of WiMAX Forum Certified equipment will be interoperable with the other WiMAX Forum Certified equipment. WiMAX Forum Certified means a service provider can buy equipment from more than one company and be confident that everything works together. WiMAX Forum Certified means a more competitive industry. WiMAX Forum Certified means lower costs. WiMAX Forum Certified means faster growth for broadband wireless -everywhere around the globe.
WiMAX Technology WiMAX is a standards-based technology enabling Â¢ the delivery of last mile wireless broadband access as an alternative to cable and DSL. WiMAX will provide fixed, nomadic, consistent, portable and eventually the mobile wireless broadband connectivity without the need for directs line-of-sight with a base station. In a typical cell radius deployment of three to ten kilometers, WiMAX Forum Certified systems can be expected to deliver capacity of up to 40 Mbps per channel, for the fixed and portable access applications. This is enough bandwidth to simultaneously support hundreds of business with T -1 speed connectivity and thousands of residences with DSL speed connectivity. Mobile network deployments are expected to provide up to 15 Mbps of capacity within a typical cell radius deployment of up to three kilometers. It is 'expected that WiMAX technology will be incorporated in notebook computers and PDAs by 2007, allowing for the urban areas and cities to become "metro zones" for portable outdoor broadband wireless access. WiMAX Forum Certified equipment is expected to provide up to 50-kilometers of range and allow users to receive broadband connectivity without requiring a direct line of sight with the base station. The equipment is also expected to provide shared data rate up to 70Mpbs, which is enough bandwidth to simultaneously support more than 60 businesses with T1 type connectivity and hundreds ot homes with DSL-type connectivity with a single base station.
7. WIMAX AND WIFI The IEEE 802.16 media access controller (MAC) is significantly different from that of IEEE 802.11 Wi-Fi MAC. In Wi-Fi, the MAC uses contention access all subscriber stations wishing to pass data through an access point are competing for the AP's attention on a random basis. This can cause distant nodes from the AP to be repeatedly interrupted by less sensitive, closer nodes, greatly reducing their throughput. And this makes services , such as VolP or IPTV which depend on a determined level of quality of service (OoS) difficult to maintain for large numbers of users. Â¢ WI-RNflWORkARCHITECTUREDIAGRAM A recent addition to the WiMAX standard is theunderway which will add full mesh networking capability by enabling WiMAX nodes to simultaneously operate in the "subscriber station" and "base station" mode. This will blur that initial distinction and allow for widespread adoption of WiMAX based mesh networks and promise widespread WiMAX adoption. WiMAX/802.16's use of OFDMA and scheduled
WiMAX .. Â¢ MAC allows wireless mesh networks to be much more robust and reliable. These differences between and the evolution of Wi-Fi and WiMAX mesh networks could serve as a separate Wikipedia topic. The original WiMAX standard,IEEE 802.16, specifies WiMAX in the 10 to 66GHz range. 802.16a ,updated in 2004 to 802.16-2004, added support for the 2 to11 GHz range, of which most parts are already unlicensed internationally and only very few still require domestic licenses. Most business interest will probably be in the 802.16-2004 standard , as opposed to the licensed frequencies. The WiMAX specification improves upon many of the limitations of the WiFi standard by providing increased bandwidth and stronger encryption. It also aims to provide connectivity between the network endpoints without direct line of sight in some circumstances. The details of performance under the non-line of sight (NLOS) circumstances are unclear as they have yet to be demonstrated. It is commonly considered that spectrum under 5-6 GHz is needed to provide reasonable NLOS performance and cost effectiveness for PtM (point to multi-point) deployments. WiMAX makes clever use of multi-path signals but does not define the laws of physics. WiMAX is a wireless digital communications system, also known as IEEE 802.16 that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 -10 miles (5 -15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 -300 feet (30 100m). With WiMAX and WiFi-like the data rates are easily supported, but the issue of interference is lessened. WiMAX operates on both
licensed and non-licensed frequencies, providing a regulated environment and viable economic model for wireless carriers. WiMAX can be used for wireless networking in much the same way as the more common WiFi protocol. WiMAX is a second-generation protocol that allows for more efficient bandwidth use , interference avoidance ,and is intended to allow higher data rates over longer distances. WiMax is not a replacement for Wi-Fi hotspot and home networking technologies primarily for cost reasons. WiMax (802.16e) is a newer standard of wireless networking designed to provide the last mile of high speed internet access to the end user. Some people would call WiMAX WiFi on steroids but this would be to broad of an assessment . Wi-Fi was and still will be used in LAN environments for the foreseeable future. WiMax was designed to provide (MAN) Metropolitan Area Access, to the homes and businesses. WiMax (MAN) deployments are similar to a Wi-Fi network. First the ISP would have their T3 or higher access. The ISP would then use line of sight antennas (Bridges) to connect to towers that would distribute the non line of sight signal to (MAN) residential/business clients. WiMax line of sight antennas operate at a higher Frequency up to 66mhz. The Distribution antennas do not have to be in the line of sight with their clients. Non line of sight towers operate on a range similar to Wi-Fi . WiMax can operate right next to cell phone towers with no interference. Wi Max networks are similar to the Wi-Fi in deployment. The WiMAX Base station or Tower will beam a signal to a WiMax
Receiver. Similar to a Wi-Fi access point sending a signal to a laptop. As far as I can tell laptops will be shipping with the WiMAX receivers in 2006. QOS (Quality of Service) is an major issue with WiMax because of the number of people accessing a tower at once. Some would think that a tower could be easily overloaded with a lot of people accessing it at once. Built into the WiMax standard is an algorithm that when the tower/base station is nearing capacity then it automatically will transfer the user to another WiMax tower or cell. Unlike a Wi-Fi clients who have to kind of fight to stay associated with a given access point; WiMax will only have to perform this hand shake at the MAC level the first time they access the network. WiMax is designed for building a network infrastructure when the environment or distance is not favorable to a wired network. WiMax is a cheaper and quicker alternative than having to lay wire. Third world country will greatly benefit from deploying WiMax networks . WiMax can handle virtually all the same protocols Wi-Fi can include the VOIP. African countries are now going to start deploying WiMax networks instead of cell phone networks. Disaster zones can also utilize WiMax giving them the ability to distribute crisis information quickly and cheaply. Militaries are already using wireless technology to connect remote sites. Logistics will be simplified with the ease of tracking with RF technologies. WiMax can also handle Webcams and streaming video which would give commanders eyes on target capability. Just imagine if planes were able to drop preconfigured self deploying WiMax antennas in strategic areas giving troops real time battlefield Intel. Armed with wireless cameras, drones and a GPS one soldier would truly be an Army of One.
As WiMax is deployed in more areas , theory life capabilities of WiMax will come to light. The WiMax and Wi-Fi are Think of a WiMax network as an with out with providing your internet access your businessl home. Wi-Fi will be used within in your LAN future.
8. DEPLOYMENT OF WiMAX Today, last mile connections are typically made through cable, DSL (Digital subscriber Line) ,fiber optic connections and even standard phone lines. The ability to provide these connections wirelessly ,without laying wire or cable in the ground, greatly lowers the cost to provide these services. Intel sees WiMAX deploying in three phases: the first phase of WiMAX technology (based on IEEE 802.16d) will provide fixed wireless connections via out door antennas in the first half of 2005. Outdoor fixed wireless can be used for high-throughput enterprise connections (T1/E1 class services), hotspot and cellular network backhaul, and premium residential services. In the second half of 2005, WiMAX wi". be available for indoor installation, with the smaller antennas similar to a Wi-Fi access pOint today. In this fixed indoor model, WiMAX will be available for use in wide consumer residential broadband deployments, as these devices become "user instal/able", lowering installation costs for carriers. By 2006, the technology wil/ be integrated into mobile computers to support roaming between WiMAX service areas.
9. APPLICATIONS The 802.16 standard will help the industry provide solutions across multiple broadband segments: 1. Cellular back-haul: -Internet backbone providers in the U.S. are requires leasing lines to third -party service providers, an arrangement that has tended to make wired backhaul relatively affordable. The result is that only about 20% of cellular towers are backhauled wirelessly in the U.S. In Europe, where it is less common for local exchange carriers to lease their lines to competitive thirdparties, service providers need affordable alternatives. Subsequently, wireless backhaul is used in approximately 80 percent of European cellular towers. With the potential removal of the leasing requirement by the FCC, U.S. cellular service providers ~ill also look to wireless backhaul as a more cost-effective alternative. The robust bandwidth of 802.16a technology makes it an excellent choice for back-haul for commercial enterprises such as hotspots as well as point-to-point back-haul applications. 2. Broadband on-demand: -Last-mile broadband wireless access can help to accelerate the deployment of 802.11 hotspots and home/small office wireless LANs, especially in those areas not served by cable or DSL or in areas where the local telephone company may have a long lead time for provisioning broadband service. Broadband Internet connectivity is mission critical for many businesses, to the extent that these organizations may actually relocate to areas where service is available. In today's market, local exchange carriers have been known to take three months or more to provision a T1 line for a business customer, if the service is not already available in the
building. Older buildings in metropolitan areas can present a tangle of wires that can make it difficult to deploy broadband connections to selected business tenants. 802.16a wireless technology enables a service provider to provision service with speed comparable to a wired solution in a matter of days, and at significantly reduced cost. 802.16a technology also enables the service provider to offer instantly configurable "on-demand" high-speed connectivity for temporary events including trade shows that can generate hundreds or thousands of users for 802.11 hotspots. In these applications, operators use 802.16a solutions for backhaul to the core network. Wireless technology makes it possible for the service provider to scale-up or scale-down service levels, literally within seconds of a customer request. "On-demand" connectivity also benefits businesses, such as construction sites, that have sporadic broadband connectivity requirements. Premiulll "on demand" last-mile broadband services represent a significant new profit opportunity for operators. 3. Residential broadband: -Filling gaps in cable and DSL coverage:-Practical limitations prevent cable and DSL technologies from reaching many potential broadband customers. Traditional DSL can only reach about 18000 feet (3 miles) from the central office switch, and this limitation means that many urban and suburban locations may not be served by DSL connections. Cable also has its limitations. Many older cable networks have not been equipped to provide a return channel, and converting these networks to support high-speed broadband can be expensive. The cost of deploying able is also significant, deterrent to the extension of wired broadband service in areas with low subscriber density. The current generation of proprietary wireless systems is relatively expensive for massive deployments because without a standard, few economies of state are possible. This cost inefficiency will all change with the launch of
WiMAX 28 standards based systems based on 802.16. in addition, the range of 802.16a solutions, the absence of line of sight requirement, high bandwidth, and the inherent flexibility and low cost helps to overcome the limitations of traditional wired and proprietary wireless technologies 4. Underserved areas: -Wireless internet technology based on IEEE 802.16 is also a natural choice for underserved rural and outlying areas with low population density. In such areas, local utilities and governments work together with a local wireless internet service provider (WISP) to deliver service. Recent statistics show that there are more than 2500 WISPs who take advantage of license exempt spectrum to serve over 6000 markets in the U.S. On an international basis, most deployments are in license spectrum and are deployed by local exchange carriers who require voice services in addition to high speed data. This is because in these areas the wired infrastructure either does not exist or does not offer the quality to support reliable voice, let alone high-speed data. The term wireless local loop is often used to describe such applications, since it is used as a substitute for traditional copper phone wire in the local loop. 5. Best connected wireless service: -As the number of IEEE 802.11 hotspots proliferates, users will naturally want to be wirelessly connected even when they are outside the range of nearest hotspots. The IEEE 801.16e extension to IEEE 802.16a introduces nomadic capabilities which will allow users to connect to a WISP even when they roam outside their home or business or go to another city that also has a WISP.
10. ADVANTAGES The principle advantage of systems based on 802.16 are multi fold : the ability quickly provision even in areas that are hard to avoidance of steep installation costs: and the ability overcome the physical limitations of traditional wired infrastructure. Providing a wired broadband connection to a currently underserved area through cable or can be a time consuming, expensive process, with the that a surprisingly number of areas in the US and throughput the world do not have access to band connectivity 802.16 technology provides a flexible, cost effective, standards based means of filling existing in broad band and creating new forms of broadband services envisioned in a "wired" world.
11. CONCLUSION The cost and complexity associated with traditional wired cable and telephone infrastructure have resulted in significant broadband coverage gaps in the U.S. and international geographies. Early attempts to use wireless technology to fill these coverage gaps have involved a number of proprietary solutions for wireless broad band access that have fragmented the market without providing significant economies of scale. High speed wireless broadcast technology based on the IEEE 802.16 standard promises to open new, economically viable market opportunities for operators, wireless internet service providers, and equipment manufacturers. The flexibility of wireless technology, combine ed with the high through put, scalability, long range and quality of service features of the IEEE 802.16 standard will help fill the broadband coverage gap and reach millions of new residential and business customers world wide . The WiMAX forum is an industry group focused on creating system.
12. BIBLIOGRAPHY Compnetworking.about.com Â¢ Â¢ Â¢ Â¢ http://www.pcworld.com