INTRODUCTION TO WIMAX
1.1 What is WiMAX?
WiMAX, an acronym that stands for Worldwide Interoperability for Microwave Access, is a form of broadband wireless access and based on the IEEE 802.16 standard for wireless metropolitan-area networks (MANs). This technology is an emerging technology, which has still not come into existence but has much more advantages then the other products till today and soon it will be in market. It is a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards. IEEE 802.16 is working group number 16 of IEEE 802, specialising in point-to-multipoint broadband wireless access. It is the next generation of WiFi, or Wireless networking technology that will connect the users to the Internet at faster speeds and from much longer ranges than current wireless technology allows. WiMAX is a standards-based wireless technology that provides high-throughput broadband connections over long distances. WiMAX can be used for a number of applications, including "last mile" broadband connections, hotspots and cellular backhaul, and high-speed enterprise connectivity for business.
WiMAX is an implementation of the emerging IEEE 802.16 standard that uses Orthogonal Frequency Division Multiplexing (OFDM) for optimization of wireless data services. OFDM technology uses "sub-carrier optimization," assigning small sub-carriers (kHz) to users based on radio frequency conditions. This enhanced spectral efficiency is a great benefit to OFDM networks and makes them very well suited to high-speed data connections for both fixed and mobile users. Systems based on the emerging IEEE 802.16 standards are the only standardized OFDM-based Wireless Wide Area Networks (WWAN) infrastructure platforms today.
Thus, WiMAX (Worldwide Interoperability for Microwave Access) is poised to become a key technical underpinning of fixed, portable and mobile data networks.
1.2 How WiMAX is emerging?
Early products are likely to be aimed at network service providers and businesses, not consumers. There arose a need among the users for a technology, which has broadband wireless networks and that too at larger distances and faster speeds. This was done by Wi-Max technology which has the potential to enable millions more to have wireless Internet connectivity, cheaply and easily. Wi-Max overcomes all the disadvantages of the Wi-Fi technology.
1.3 History of WiMAX
The first one to emerge was the mobile services. Although they came into existence from 1940, the real popularity and use with masses started by 1990. In 1990, mobile services based on Digital mobile technologies were being talked off. After this there was no looking back. 2G, then 2.5G and then 3G technologies were developed and the 4G is soon expected.
The LANs were out by 1980 and since the ratification of the IEEE 802.11b standard in 1999, wireless LANs have become more prevalent.
While MOBILE services were mainly used for voice communications and telephony purpose, WLANs were deployed in a distributed way to offer last-few hundred-feet connectivity to a wireline backbone corporate or campus network. Typically, they were implemented as part of a private network.
Although, the mobile services could provide connectivity to huge areas, they were far behind when the data rates were being talked about (max around 100 Kbps). The Wi-Fi technology also termed as the 802.11b by IEEE, could provide huge data rates (around 11Mbps) as compared to mobile techs but connectivity was limited to only few feet or meters.
WORKING OF WIMAX
2.1 WiMAX working
WiMAX may be used in a wireless metropolitan area network (MAN) technology to connect IEEE 802.11(Wi-Fi) hotspots to the Internet and provide a wireless extension to cable and DSL for last mile (last km) broadband access. IEEE 802.16 provides up to 50 km (31 miles) of linear service area range and allows users connectivity without a direct line of sight to a base station.
Fig. 2.1.1 Working Of WiMAX
As shown in the figure, the roaming users, LAN and MAN are connected together to the Base Station through the Air Interface standard 802.16. This Internet Backbone or Public Switched Telephone Network is then connected to Telco Core network or Private (Fiber) Network, which further connected to Line of Sight Backhaul 802.16, which is an Air Interface Standard and is used to connect the wireless networks.
802.16 supports point-to-multipoint architecture in the 10-66 GHz range, transmitting at data rates up to 120Mbps. At those frequencies, transmission requires line-of-site, and roofs of buildings provide the best mounting locations for base and subscriber stations. The base station connects to a wired backbone and can transmit wirelessly up to 30 miles to a large number of stationary subscriber stations, possibly hundreds.
To accommodate non-line-of-site access over lower frequencies, IEEE published 802.16a in January 2003, which includes support for mesh architecture. 802.16a operates in the licensed and unlicensed frequencies between 2GHz and 11GHz using orthogonal frequency division multiplexing (OFDM), which is similar to 802.11a and 802.11g.
Many companies are active in both the IEEE 802.16 standards development and the IEEE 802.11 efforts for Wireless LAN, and envision the combination of 802.16a and 802.11 creating a complete wireless solution for delivering high speed Internet access to businesses, homes, and Wi-Fi hot spots.
Mechanisms in the Wireless MAN MAC provide for differentiated QoS(Quality of Service) to support the different needs of different applications. For instance, voice and video require low latency but tolerate some error rate. By contrast, generic data applications cannot tolerate error, but latency is not critical. The standard accommodates voice, video, and other data transmissions by using appropriate features in the MAC layer, which is more efficient than doing so in layers of control overlaid on the MAC.
2.2 WiMAX Standards
The current 802.16 standard is IEEE Std 802.16-2004, approved in June 2004. It renders the previous (and 1st) version 802.16-2001 obsolete, along with its amendments 802.16a and 802.16c.
IEEE Std 802.16-2004 addresses only fixed systems. An amendment 802.16e is in the works which adds mobility components to the standard. This amendment is expected to be completed in mid 2005.
• 802.16-2004 IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems
• 802.16.2-2004 IEEE Recommended Practice for Local and metropolitan area networks -- Coexistence of Fixed Broadband Wireless Access Systems
• 802.16-2001 obsoleted by 802.16-2004
802.16a amendment, obsoleted by The current IEEE 802.16 standards can be freely downloaded from the "Get IEEE 802"(tm) page
Intel sees WiMAX deploying in three phases: the first phase of WiMAX technology (based on IEEE 802.16-2004) will provide fixed wireless connections via outdoor 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 will be available for indoor installation, with smaller antennas similar to 802.11-based WLAN access points today. In this fixed indoor model, WiMAX will be available for use in wide consumer residential broadband deployments, as these devices become "user installable," lowering installation costs for carriers.
By 2006, technology based on the IEEE 802.16e standards will be integrated into portable computers to support movement between WiMAX service areas. This allows for portable and mobile applications and services. In the future, WiMAX capabilities will even be integrated into mobile handsets.
2.4 Wi-Fi(802.11 LAN) versus WiMAX (802.16 WMAN)
Both are based on orthogonal frequency division multiplexing (OFDM), use multiple pilot tones, and support modulations ranging from BPSK to 64 QAM.
But there are some major differences as well. For instance, rather than a fixed 20-MHz bandwidth with 52 subcarriers as in 802.11, WiMAX systems can use variable bandwidths from 1 to 28 MHz with 256 subcarriers (192 data subcarriers) in either licensed or unlicensed spectrum. The first WiMAX rollouts are expected to use 3.5- and 7-MHz channel bandwidths.
WiMAX supports subchannelization, meaning that instead of transmitting on all 192 data subcarriers, you can transmit on just a subset. In this scenario, by using the same amount of power over fewer carriers, the system achieves greater range. As WiMAX CPE evolves into in-building devices, it'll be necessary to make up for the power loss incurred when transmitting the signal outside the building. Because CPE is typically limited in power, concentrating the power over fewer subcarriers in the uplink can balance the power in the uplink and downlink, and enable greater range.
While the larger number of subcarriers gives WiMAX an advantage over 802.11, the resulting challenge to the system design is that the subcarriers are spaced more closely together, so there are tighter requirements for phase noise and timing jitter. This translates to a need for higher-performance synthesizers.
WiMAX also uses a variable-length guard interval to improve performance in multi-path environments. The guard interval is a time delay at the beginning of the packet to compensate for multi-path interference. With a very clear channel, the guard interval can be shortened, increasing the throughput. With more subcarriers, and with a variable-length guard interval, a WiMAX system's overall spectral efficiency will be 15 to 40% higher than a WLAN system. For instance, WiMAX achieves a spectral efficiency ranging from 3.1 to 3.8 Mbits/s/MHz, compared to only 2.7 Mbits/s/MHz for 802.11a/b/g (see the table).
Fig. 2.4.2 Figure showing Wi-Fi and WiMAX technology difference
Error-vector magnitude (EVM) requirements for 802.11 are specified at -25 dB, which is required to achieve a 10% packet error rate. For 802.16, EVM is held to -31 dB, which is based on a 1% packet error rate. This lower error rate helps contribute to WiMAX's longer range. Also contributing to the longer range is the receiver noise figure, which is more stringent for 802.16. Specifically, 802.11's maximum noise figure is 10 dB, while 802.16 operates at 7 dB.
802.11 only supports time division duplexing (TDD), where transmit and receive (Tx/Rx) functions occur on the same channel, but at different times. In comparison, the 802.16 spec offers more flexibility, supporting TDD, frequency division duplexing (FDD), and half-duplex FDD (H-FDD). FDD uses simultaneous Tx/Rx on different frequencies; H-FDD transmits on different channels at different times. The approach that designers select affects cost, footprint, and design time. For example, an FDD system will cost more because simultaneous Tx/Rx requires two complete radios. However, FDD will allow greater throughput, as bandwidth is dedicated for receive and transmit, and this bandwidth is used simultaneously.
PRESENT AND FUTURE OF WIMAX
It is Wi-Max; the 802.16 standard developed by IEEE-SA (Institute of Electrical and Electronics Engineers Standards Association) in order to make Broadband Wireless Access more widely available. This standard was published on 8th April 2002.
It specifies the Wireless MAN Air Interface for wireless metropolitan area networks. IEEE 802.16 addresses the "first-mile/last-mile" connection in wireless metropolitan area networks. It focuses on the efficient use of bandwidth between 10 and 66 GHz (the 2 to 11 GHz region with PMP and optional Mesh topologies after 2002) and defines a medium access control (MAC) layer that supports multiple physical layer specifications customized for the frequency band of use.
The 10 to 66 GHz standard supports continuously varying traffic levels at many licensed frequencies (e.g., 10.5, 25, 26, 31, 38 and 39 GHz) for two-way communication. It enables interoperability among devices, so carriers can use products from multiple vendors and warrants the availability of lower cost equipment. The draft amendment for the 2 to 11 GHz region will support both unlicensed and licensed bands.
Broadband wireless will revolutionize people's lives by enabling a high-speed connection directly to the information they need, whenever and wherever they need it. Broadband data services, such as delivery of rich Internet Protocol and media content, are an increasingly important component of the services and revenue of network operators, who want to expand the reach of their broadband data networks without expensive construction and infrastructure costs. High-speed broadband wireless data overlays to voice network are just emerging, as service providers respond to these consumer and enterprise demands for rich media, mobile applications and services.
Service providers will operate WiMAX on licensed and unlicensed frequencies. The technology enables long distance wireless connections with speeds up to 75 megabits per second. (However, network planning assumes a WiMAX base station installation will cover the same area as cellular base stations do today.) Wireless WANs based on WiMAX technology cover a much greater distance than Wireless Local Area Networks (WLAN), connecting buildings to one another over a broad geographic area. WiMAX can be used for a number of applications, including "last mile" broadband connections, hotspot and cellular backhaul, and high-speed enterprise connectivity for businesses
Another application under consideration is gaming. Sony and Microsoft are closely considering the addition of WiMax as a standard feature in their next generation game console. This will allow gamers to create ad hoc networks with other players. This may prove to be one of the "killer apps" driving WiMax adoption: WiFi-like functionality with vastly improved range and greatly reduced network latency and the capability to create ad hoc mesh networks.
WiMax Promises...
• Up to a ten (10) mile range without wires
• Broadband speeds without cable or T1
• Handles "last mile" access in remote areas
• Licencing and equipment due in 2005
• Affordable technology
A recent addition to the WiMax standard is underway which will add full mesh networking capability by enabling WiMax nodes to simultaneously operate in "subscriber station" and "base station" mode. This will blur that initial distinction and allow for widespread adoption of WiMax based mesh networks. Intel is working with the wireless industry to drive deployment of WiMAX networks. For countries that have skipped wired infrastructure as a result of inhibitive costs and unsympathetic geography, WiMax can enhance wireless infrastructure in an inexpensive, deployment-friendly and effective manner.
WIMAX ADVANTAGES AND DISADV
4.1 WiMAX Technical Advantages:
Because IEEE 802.16 networks use the same Logical Link Controller (standardized by IEEE 802.2) as other LANs and WANs, it can be both bridged and routed to them.
WiMAX is a wireless metropolitan area network (MAN) technology that can connect IEEE 802.11(Wi-Fi) hotspots to the Internet and provide a wireless extension to cable and DSL for last mile (last km) broadband access. IEEE 802.16 provides up to 50 km (31 miles) of linear service area range and allows users connectivity without a direct line of sight to a base station. Note that this should not be taken to mean that users 50 km (31 miles) away without line of sight will have connectivity. The technology also provides shared data rates up to 70 Mbit/s, which, according to WiMAX proponents, is enough bandwidth to simultaneously support more than 60 businesses with T1-type connectivity and well over a thousand homes at 1Mbit/s DSL-level connectivity.
It is also anticipated that WiMax will allow interpenetration for broadband service provision of VoIP, video, and internet access - simultaneously. Most cable and traditional telephone companies are closely examining or actively trial-testing the potential of WiMax for "last mile" connectivity. This should result in better pricepoints for both home and business customers as competition results from the elimination of the "captive" customer bases both telephone and cable networks traditionally enjoyed. Even in areas without preexisting physical cable or telephone networks, WiMax could allow competitors joint access to any subscriber within range; home units the size of a paperback book that provide both phone and network connection points are already available - and advertised as "plug and play" easy to install. There is also interesting potential for interoperability of WiMax with cellular networks. WiMax antennas can "share" a cell tower without compromising the function of cellular arrays already in place. Companies that already lease cell sites in widespread service areas have a unique opportunity to diversify, and often already have the necessary spectrum available to them (i.e. they own the licenses for radio frequencies important to increased speed and/or range of a WiMax connection). WiMax antennae may be connected to a service provider's "head end" via either a light fiber optics cable or a directional microwave link. Some cellular companies are evaluating WiMax as a means of increasing bandwidth for a variety of data-intensive applications. In line with these possible applications is the technology's ability to serve as a "backhaul" for cellular and internet traffic from remote areas back to a physical data backbone. Although the cost-effectiveness of WiMax in a remote application will be higher, it is definitely not limited to such applications, and may in fact be an answer to expensive urban deployments of T1 backhauls as well. Given developing countries' (such as Africa) limited wired infrastructure, the costs to install a WiMax station in conjunction with an existing cellular tower or even as a solitary hub will be diminutive in comparison to developing a wired solution. The wide, flat expanses and low population density of such an area lends itself well to WiMax and its current diametrical range of 30 miles. For countries that have skipped wired infrastructure as a result of inhibitive costs and unsympathetic geography, WiMax can enhance wireless infrastructure in an inexpensive, deployment-friendly and effective manner.
Another application under consideration is gaming. Sony and Microsoft are closely considering the addition of WiMax as a standard feature in their next generation game console. This will allow gamers to create ad hoc networks with other players. This may prove to be one of the "killer apps" driving WiMax adoption: WiFi-like functionality with vastly improved range and greatly reduced network latency and the capability to create ad hoc mesh networks.
An important aspect of the IEEE 802.16 is that it defines a MAC layer that supports multiple physical layer (PHY) specifications. This is crucial to allow equipment makers to differentiate their offerings. This is also an important aspect of why WiMAX can be described as a 'framework for the evolution of wireless broadband' rather than a static implementation of wireless technologies. Enhancements to current and new technologies and potentially new basic technologies incorporated into the PHY (physical layer) can be used. A converging trend is the use of multi-mode and multi-radio SoCs and system designs that are harmonized through the use of common MAC, system management, roaming, IMS and other levels of the system. WiMAX may be described as a bold attempt at forging many technologies to serve many needs across many spectrums.
A recent addition to the WiMax standard is underway which will add full mesh networking capability by enabling WiMax nodes to simultaneously operate in "subscriber station" and "base station" mode. This will blur that initial distinction and allow for widespread adoption of WiMax based mesh networks
The two driving forces of modern Internet are broadband, and wireless. The WiMax standard combines the two, delivering high-speed broadband Internet access over a wireless connection. Because it can be used over relatively long distances, it is an effective “last mile” solution for delivering broadband to the home, and for creating wireless “hot spots” in places like airports, college campuses, and small communities.
Based on the IEEE 802.16 Air Interface Standard, WiMax delivers a point-to-multipoint architecture, making it an ideal method for carriers to deliver broadband to locations where wired connections would be difficult or costly. It may also provide a useful solution for delivering broadband to rural areas where high-speed lines have not yet become available. A WiMax connection can also be bridged or routed to a standard wired or wireless Local Area Network (LAN).
The so-called “last mile” of broadband is the most expensive and most difficult for broadband providers, and WiMax provides an easy solution. Although it is a wireless technology, unlike some other wireless technologies, it doesn't require a direct line of sight between the source and endpoint, and it has a service range of 50 kilometers. It provides a shared data rate of up to 70Mbps, which is enough to service up to a thousand homes with high-speed access.
4.2 WiMAX Disadvantages:
As WiMAX is an emerging technology, its particular disadvantages have not yet been found. But however the disadvantages can be seen when comparing with other wireless technology called TD-CDMA(Time Division CDMA). Now a question arises in our mind: WiMAX is hot but will it survive? Let us see how we get the answer to this question.
In today's complex broadband environment, demand is rising for ubiquitous wireless broadband coverage and for bigger and faster wide-area wireless pipes that can handle the bandwidth required for applications such as video broadcasting, Internet browsing, Voice over IP (VoIP), and more. Cellular operators and Internet Service Providers (ISPs) alike want a wireless connection solution that can also provide a migration path to full mobility similar to that offered by existing cellular systems. The availability of such a wireless broadband solution is especially important for operators that do not own cable or telephone access lines, since the solution will give them the opportunity to reach subscribers directly.
Two options supporting wireless broadband applications are time division-CDMA (TD-CDMA) and WiMAX. WiMAX has been hailed as the hot new metropolitan-area wireless standard, even though it is not yet complete and real products are still two to three years away. TD-CDMA complies with the 3G Partnership Project (3GPP) Universal Mobile Telecommunications Systems Time Division Duplexing (UMTS TDD) standard, and many operators have already deployed and are today generating revenue from TD-CDMA-based wireless networks. As part of 3GPP, TD-CDMA has the backing of a large international standards body and large number of operators and equipment vendors. WiMAX, on the other hand, is being developed by a small industry group.
Compared to WiMAX, TD-CDMA has a number of technical advantages that make it a strong contender in the wireless broadband market. Below, we'll show you five reasons why TD-CDMA may be a better option than WiMAX in broadband wireless designs.
1. Bigger Cells, Reduced Expenses
A wireless technology's cell coverage area is of key importance, since operators can reduce their initial capital expenditures if they can serve the same area with fewer base stations. TD-CDMA has a clear advantage here; cell coverage of up to several kilometers has been proven in major operator trials and commercial deployments. To achieve this coverage, TD-CDMA employs advanced power control mechanisms that allow the data throughput to gradually decrease as a terminal gets further and further away from the base station.
WiMAX calls for use of an orthogonal frequency-division multiplexing (OFDM)-based modulation technique, and coverage has not yet been proven in an actual network. Theoretical analysis shows that cell coverage is less than 280 meters outdoors using OFD multiple access (OFDMA), and less than 450 meters outdoors using OFDMA in the 2.6 GHz band.
2. Fixed Wireless Now, Mobile Later
The ability of a technology to support mobility -- even for operators that primarily wish to deploy a fixed wireless solution -- is important for two reasons. First, the ability to carry the PCMCIA modem anywhere is an important value-add differentiation and selling point for operators, even though most of the time the user is stationary. Second, a wireless broadband technology that supports mobility now, unlike one that supports only fixed applications, gives operators an easy migration path to mobile applications in the future.
Mobility and portability must be supported on the subscriber terminal, since traditionally fixed modems have a very different form factor than mobile devices. One approach to resolving this problem employs a detachable PCMCIA card that can be used with a range of fixed subscriber terminal boxes (CTEs). For stationary applications, the user can insert the PCMCIA card into a CTE, and for mobile applications, the user can remove the PCMCIA card from the CTE and insert it into a laptop computer. In the future, TD-CDMA and dual-mode handsets that take advantage of the mobile network will be available.
TD-CDMA subscriber terminals can support mobility by automatically detecting the signal strength of surrounding base station cells and informing the network of a better signal before the existing connection is broken. Automatic signal detection thus enables a transparent handoff as the user moves from the coverage area of one base station to another.
Mobility also requires the support of both the radio access network (RAN) and the core network and is much easier to achieve when the entire network is based on the same standard. TD-CDMA uses the same mature, core networks already widely deployed for UMTS/GSM, and handoff from one piece of equipment to another is handled by well-defined 3GPP standards and protocols.
The first release of WiMAX is defined only as a broadband RAN and does not support mobility. While it is claimed that later versions of WiMAX will support mobility, the lack of standardization makes it difficult to integrate WiMAX-based products from different vendors. Although some vendors say they are working on mobile WiMAX, industry observers are skeptical this will happen soon, if at all, especially as there is increasing recognition that UMTS-TDD already offers mobility as well as high speeds.
3. VoIP Support
Normal shared-channel implementation for packet data is great for achieving bandwidth efficiency but presents a big challenge for packetized voice traffic. TD-CDMA technology resolves this problem by supporting dedicated air interface channels for voice-over-IP (VoIP) traffic when a user voice session is set up, as well as by supporting end-to-end quality of service (QoS).
Dedicated bandwidth for voice packets over the air-interface is critical, as voice packets must be delivered with minimal latency to ensure sound quality. TD-CDMA, together with the 3GPP-defined core network QoS, ensures that neither the air-interface nor the core network becomes a bottleneck for voice traffic, traditionally a critical limitation for voice services over a shared packet data network. TD-CDMA VoIP is being demonstrated in live field deployments today.
WiMAX does not address VoIP yet, and QoS is an end-to-end effort that requires support from the subscriber modem to every piece of equipment in the network. Unlike 3GPP, WiMAX does not define the behavior of each piece of equipment in the network, making QoS a complex task.
4. Global Roaming
TD-CDMA supports global roaming, since the underlying 3GPP standards were developed for both cellular operators and traditional ISPs. Cellular operators' needs are addressed through support for Home Location Register (HLR) and Universal Subscriber Identify Module (USIM), which are defined for global roaming. ISP roaming needs are met via AAA RADIUS servers and HLR extension functions that can be built into TD-CDMA equipment.
WiMAX, however, does not address or define cellular operators' needs. Because it is being designed to meet the needs of ISPs, WiMAX supports roaming only via AAA RADIUS and does not have well-defined protocols for global roaming.
5. Frequency Band Flexibility
TD-CDMA has the edge over WiMAX in providing the operator with as much flexibility as possible in using available frequency band. TD-CDMA operates in 1.9 and 2 GHz UMTS-TDD band, as well as the 2.5 and 3.4 GHz bands. WiMAX, on the other hand, cannot operate in the UMTS band. Furthermore, European governments may restrict the 2.5 GHz band to UMTS-based technology only in the near future. Thus, TD-CDMA has a much bigger addressable market than WiMAX.
N=1 re-use is also a key part of frequency flexibility and a natural characteristic of all CDMA technologies. With N=1 re-use, operators need to support only one times the frequency spectrum required. WiMAX requires in-band subchannel re-use or frequency hopping if N=1 is used. Both techniques reduce network capacity. In most cases, N=3 reuse is necessary with WiMax and would require operators to purchase more spectrum.
Clear Advantage of TD-CDMA compared to Wi-MAX
While it is difficult to compare all aspects of TD-CDMA and WiMAX technologies in a brief article, even a bird's eye view of some of the issues reveals certain major differences.
The clear advantage goes to TD-CDMA, a proven technology that is available now for cellular operators and ISPs alike. Also, because TD-CDMA is part of the 3GPP umbrella, it is fully interoperable with existing UMTS-based networks and provides a migration path to mobile applications, enabling far more flexible use of available spectrum as well as the QoS required by voice applications. These advantages add up to a compelling brief for TD-CDMA as the technology best suited to implement wireless broadband solutions worldwide.
Telecommunications Choices...
Business-based telecommunications encompasses many options. Major businesses often access large-capacity, high-speed fiber optic networks for broadband, converged services. Fiber networks, however, serve less than five percent of commercial structures worldwide and extending these networks with cable is costly and time consuming.
CONCLUSION
Thus, WiMAX which stands for Worldwide Interoperability for Microwave Access. WiMAX may be used in a wireless metropolitan area network (MAN) technology to connect IEEE 802.11(Wi-Fi) hotspots to the Internet and provide a wireless extension to cable and DSL for last mile (last km) broadband access. WiMax is a new standard by IEEE that removes the shortcomings of both Mobile services and WiFi technology and has the advantages of both of them. WiMax will allow interpenetration for broadband service provision of VoIP, video, and internet access - simultaneously. It is more secure than its predecessor WiFi because of use of licensed frequencies.
Unlike Wi-Fi, which anyone can set up in their home or place of business, Wi-Max would be operated by large telecommunications companies and come, within the next couple of years, with the kind of security features wired technologies employ to encrypt and protect data.
Thus, WiMAX is going to become a key of fixed, portable and mobile data networks. WiMAX is an implementation of the emerging IEEE 802.16 standard that uses Orthogonal Frequency Division Multiplexing (OFDM) for optimization of wireless data services.
Thus, WiMAX is a wireless MAN technology that can connect IEEE 802.11(Wi-Fi) hotspots to the Internet and provide a wireless extension to cable for last mile (last km) broadband access.
