about wimax

8/14/2019 About Wimax

1/4

WiMax is more robust standard for high-speed broadband wireless delivery to laptops and desktops hasbeen launched.

"WiMAX" is an acronym that stands forWorldwide Interoperability forMicrowaveAccess.

It is a standards-based technology enabling the delivery of last mile wireless broadband access as an

alternative to cable and DSL. WiMAX will provide fixed , nomadic,portable and,eventually, mobile wireless broadband connectivity without the need for direct line-of-sight with a basestation.

In a typical cell radius deployment of three to ten kilometers, WiMAX Forum Certified systems can beexpected to deliver capacity of up to 40 Mbps per channel, for fixed and portable access applications.This is enough bandwidth to simultaneously support hundreds of businesses with T-1 speed connectivityand thousands of residences with DSL speed connectivity.

Mobile network deployments are expected to provide up to 15 Mbps of capacity within a typical cell radiusdeployment of up to three kilometers. It is expected that WiMAX technology will be incorporated innotebook computers and PDAs by 2007, allowing for urban areas and cities to become metro zones forportable outdoor broadband wireless access.

Since equipment being developed by WiMAX Forum members can operate in different configurations(e.g. TDD or FDD), have different channel bandwidths or operate in different spectrum bands, discussionare ongoing in CWG, as well as in other working groups, regarding profiles that the Forum would use forWiMAX Forum Certification. The main focus is on three bands 5.8GHz, 3.5GHz and 2.5GHz.

The first generation of WiMAX Forum Certified CPEs is expected to be outdoor-installable subscriberstations akin to a small satellite dish. These are expected to be available in late 2005/early 2006 andpriced around $350 in volume. The second generation of CPEs will be indoor self-installable modemssimilar to a cable or DSL modem and will be priced around $250 in volume and are expected to beavailable in 2006. Third-generation CPEs will be integrated into laptops and other portable devices, areexpected to initially cost approximately $100 and will be available in the 2006-2007 timeframe

One of the main objectives of the WiMAX Forum is to create a single interoperable standard from theIEEE 802.16 and ETSI HiperMAN standards. This is achieved by the creation of System Profiles. Basedupon what the WiMAX Forum sees in terms of service provider and vendor equipment plans, the WiMAXForum has decided to focus first on profiles for the 256 OFDM PHY mode of the 802.16-2004 standard,which was ratified by the IEEE in June 2004. This physical layer (PHY) will be combined with a singlemedia access controller (MAC), ensuring a uniform base for all WiMAX implementations.

Compliance with the 802.16 standard does not mean equipment is WiMAX Forum Certified or that it isinteroperable with other vendors equipment. However, if a piece of equipment has earned the WiMAXForum Certified designation, it is both compliant with the 802.16 standard and interoperable with othervendors equipment that is also WiMAX Forum Certified.

The position of the 802.16a standard today parallels that of WLAN technology in the late 1990 s, whenthe market finally grew as 802.11 price vs. performance gains converted WLAN from a niche to massmarket. In the very near future, 802.16a will also achieve important price and performance points.

The WiMAX Forum is working to facilitate the deployment of broadband wireless networks based on theIEEE 802.16 standard by helping to ensure the compatibility and inter-operability of broadband wirelessaccess equipment. The organization is a nonprofit association formed in June of 2001by equipment andcomponent suppliers to promote the adoption of IEEE 802.16 compliant equipment by operators ofbroadband wireless access systems.


2/4

The WiMAX Forum is comprised of industry leaders who are committed to the open interoperability of allproducts used for broadband wireless access.

Support IEEE 802.16 standard Propose and promote access profiles for their IEEE 802.16 standard Certify interoperability levels both in network and the cell

Achieve global acceptance Promote use of broadband wireless access overall

Under the current conditions, 802.16a could emulate 802.11 s rise several years from now.

Many chip and equipment vendors ignored the chance to get into the 802.11 market early and createmarket share due to market-size limitations created by high equipment costs, a much smaller potentialaudience and no need for all things Internet and Intranet yet. WiMAX offers these technology companiesa fresh start.

802.16a is considered the next step beyond WiFi because it is optimized for broadband operation, fixedand later mobile, in the wide area network. It already includes numerous advances that are slated for

introduction into the 802.11 standard, such as quality of service, enhanced security, higher data rates,and mesh and smart antenna technology allowing better utilization of the spectrum.

The study, 802.16/WiMAX Technologies: World Market Forecasts 2003-2008, finds WiMAX and WiFicomplementary as the two technologies address different segments of the market and are optimized fordifferent tasks; local vs. metropolitan area networking. Last mile access will be the first application for802.16a but mobility will follow via 802.16e.

WiMAX is considered a migration path to 4G, but more likely to be usedby holders of BWA spectrum rather than mobile carriers. 802.16a is also expected to play a role inoutdoor and private networks, the extensionof hot spots, and backhaul applications that lack line-of -sight.

The opportunity for 802.16a equipment is forecast to reach a value of approximately $1 billion in 2008, thestudy finds, with growth accelerating late in the period. The study provides global forecasts for802.16a/e equipment and chipset shipments and revenues as well as the technology s penetration in theoverall global BWA market.

Wimax Technical Specification:The IEEE 802.16 Air Interface Standard is truly a state-of-the-art specification for fixed broadbandwireless access systems employing a point-to-multipoint (PMP) architecture. The initial version wasdeveloped with the goal of meeting the requirements of a vast array of deployment scenarios for BWAsystems operating between 10 and 66 GHz. As a result, only a subset of the functionality is needed fortypical deployments directed at specific markets. A revision to the base IEEE 802.16 standard targetingsub 11 GHz is near completion with a publishing target date of July 2004. This revision will include theamendments from Task Group c, Task Group a, and Task Group d.

The IEEE process stops short of providing conformance standards and test specifications. In order toensure interoperability between vendors equipment, the WiMAX technical working groups havecompleted the work for 10 to 66 GHz and has started work for the sub 11 GHz part of the standard. Theworking groups develop a set of system profiles, Protocol Implementation Conformance StatementProforma, Test Suite Structure & Test Purposes, and Abstract Test Suite specifications for 10 to 66 GHzand sub 11 GHz, all according to the ISO/IEC 9464 series (equivalent to ITU-T x.290 series) ofconformance testing standards.


3/4

Overview of IEEE 802.16

The IEEE 802.16 Working Group has developed point-to-multipoint broadband wireless access standardfor systems in the frequency ranges 10-66 GHz and sub 11 GHz. The standard covers both the MediaAccess Control (MAC) and the physical (PHY) layers.

A number of PHY considerations were taken into account for the target environment. At higherfrequencies, line of sight is a must. This requirement eases the effect of multipath, allowing for widechannels, typically greater than 10 MHz in bandwidth. This gives IEEE 802.16 the ability to provide veryhigh capacity links on both the uplink and the downlink. For sub 11 GHz non line of sight capability is arequirement. The original IEEE 802.16 MAC was enhanced to accommodate different PHYs and services,which address the needs of different environments. The standard is designed to accommodate eitherTime Division Duplexing (TDD) or Frequency Division Duplexing (FDD) deployments, allowing for both fulland half-duplex terminals in the FDD case.

The MAC was designed specifically for the PMP wireless access environment. It supports higher layer ortransport protocols such as ATM, Ethernet or Internet Protocol (IP), and is designed to easilyaccommodate future protocols that have not yet been developed. The MAC is designed for very high bitrates (up to 268 mbps each way) of the truly broadband physical layer, while delivering ATM compatible

Quality of Service (QoS); UGS, rtPS, nrtPS, and Best Effort.

The frame structure allows terminals to be dynamically assigned uplink and downlink burst profilesaccording to their link conditions. This allows a trade-off between capacity and robustness in real-time,and provides roughly a two times increase in capacity on average when compared to non-adaptivesystems, while maintaining appropriate link availability.

The 802.16 MAC uses a variable length Protocol Data Unit (PDU) along with a number of other conceptsthat greatly increase the efficiency of the standard. Multiple MAC PDUs may be concatenated into asingle burst to save PHY overhead. Additionally, multiple Service Data Units (SDU) for the same servicemay be concatenated into a single MAC PDU, saving on MAC header overhead. Fragmentation allowsvery large SDUs to be sent across frame boundaries to guarantee the QoS of competing services. And,payload header suppression can be used to reduce the overhead caused by the redundant portions of

SDU headers.

The MAC uses a self-correcting bandwidth request/grant scheme that eliminates the overhead and delayof acknowledgements, while simultaneously allowing better QoS handling than traditional acknowledgedschemes. Terminals have a variety of options available to them for requesting bandwidth depending uponthe QoS and traffic parameters of their services. They can be polled individually or in groups. They cansteal bandwidth already allocated to make requests for more. They can signal the need to be polled, andthey can piggyback requests for bandwidth.

The Interoperability Challenge

Plethora of OptionsFrom the preceding overview, it is clear that the IEEE 802.16 Air Interface Specification is a very capable,while complex, specification. There are allowances for a number of physical layers for different frequencybands and region-by-region frequency regulatory rules. There are features that allow an IP centric systemor an ATM centric system depending upon the needs of customers. The specification is designed to coverapplication to diverse markets from very high bandwidth businesses to SOHO and residential users.

Because of the wealth of options available, an implementer currently faces a tough decision. To addressthis issue WiMAX undertaken the development of System Profiles.


4/4

The purpose of these system profiles is to specify which features are mandatory or optional for thevarious MAC or PHY scenarios that are most likely to arise in the deployment of real systems. This allowsvendors addressing the same market to build systems for that market that are interoperable while notrequiring the implementation of absolutely every feature.

No Test Specifications

Another issue facing IEEE 802.16 developers is an artifact of the IEEE standards process concentratingprimarily on requirements. The output of the IEEE 802.16 working group is a standard, that is to say, arequirement specification. The working group will continue to expand the standard to cover additionalmarkets, through amendments and revisions to the base standard. In the past, there was no work item inIEEE 802.16 to address the creation of test specifications. Test specifications are necessary to:

Ensure that equipment and systems claiming compliance to the standard or a profile have beensufficiently tested to demonstrate that compliance.

Guarantee that equipment from multiple vendors has been tested the same way, to the sameinterpretation of the standard, increasing the interoperability of the equipment.

Enable independent conformance testing, giving further credibility to the previous two items.

This test specification initiative is an area where ETSI has an official process and is typically more

complete than the IEEE process. ETSI follows the guidelines of the ISO/IEC 9646 series (ITU-T X.29xseries). The Test Suite Structure and Test Purposes (TSS&TP) document and the Abstract Test Suite(ATC) specification, both described in ISO/IEC 9646-2 (ITU-T X.291), suit the purpose particularly well.

No Conformance StatementsHaving profiles is only part of the interoperability challenge. There must be a standard method ofidentifying which profiles a device or system complies with and which optional features are implementedso that system integrators can make educated decisions about specific features to provide to customersand to aid in the selection of equipment.

To address the IEEE short-coming, WiMAX initiated the development of a set of conformance documents,in accordance with ISO/IEC recommendations, to be submitted to the IEEE 802.16 Working Group.These include Protocol Implementation Conformance Statement (PICS), TSS&TP, and ATS.

about wimax

Documents