How To Build A Wimax Network

Overview

The latest technology buzz isWiMAX wireless networks. We have heard many things about this wonderfulnew long haul wireless technology that it almost seems as though youare just a phone call away from having yours' designed and installed.Well before you start assuming things like we all do, we thought asengineers and network architects we would share personal experiencesand the experiences of colleagues from around the world, in a mannerthat is direct, helpful, educational, and certainly reality based. Thisis a backpocket Primer for anyone now dealing with the implementationof a WiMAX network.

First, there are several misconceptionssurrounding WiMAX that need to be cleared up so that the businessaspects and engineering basis have a common understanding.

Secondly,the people who make the various decisions within your organizationsneed to understand that there are differences between a private networkand an interoperable network strategy. This subtle difference doesexist and requires a plan which considers the final transition aspects,if considered now, to easily provide a lower cost upgrade to a trueinteroperable network, now incorporating diverse vendor equipment.

Finally,while WiMAX has been out internationally for several years, it is verynew to the United States, only a few months old, with very littletraining and education available to those who have the responsibilityto build these systems or those who will make the financial andtechnical decisions to have these systems built for them as part oftheir long haul wireless strategy.

Our experiences and theexperiences of our collegues are offered here as contributions as wellas tying these in to the standards and certification authorities allmeant to provide a reality based quick reference education for anyonein the throws of How to Build a WiMAX network.

Primer

WiMAXis a standard designed for fixed broadband wireless access featuring acontrolling base station, that connects subscriber stations not to eachother but to various public networks, such as the Internet, linked tothat base station. The acronym means “ worldwideinteroperability formicrowave access” or (WiMAX).

WiMAX, as a standards initiative,is based on a "set of profiles" supporting a wide range of frequencies(up to 66GHz)with channel sizes (1.25MHz to 20MHz) and applications(LOS and NLOS), and finally PTP and PTMP. The WiMAX profiles narrow thescope of 802.16 to focus on first service specific configurations. TheIEEE titled the specification 802.16 and released it December 2002. Theprofiles addressed in that “profiles release” are802.16-2004 (old d)and 802.16e as presented further down.

The WIMAX forum was formedeight months earlier in April 2002 to support, promote and certifycompatibility and interoperability of devices based on the 802.16specification, and to develop such devices for the marketplace.Founding Members of the organization include Airspan, Alvarion, AnalogDevices, Aperto Networks, Ensemble Communications, Fujitsu, Intel,Nokia, OFDM Forum, Proxim, and Wi-LAN.

WiMAX is the IEEE 802.16Point-to-Multipoint broadband wireless access standard for systems inthe stated frequency ranges. WiMAX will initially provide fixednomadic, portable and eventually, mobile wireless broadbandconnectivity. To that end there are two standards (802.16d (new -2004)and 802.16e respectively) although they will both perform similarfunctions because they must be interoperable. One clearly is a fixedsolution and the other a mobile solution that must still communicatewith a fixed solution. So one of the first considerations is whetheryou want to build out a mobile or fixed network. In many cases youwould have already considered your target market segments, spectrumavailability, regulatory constraints and your deployment need.

Which One do I Need?

Generallyspeaking, the current 802.16-2004 (originally 802.16d) fixed networkproducts are less complex than 802.16e mobile network systems because;they can be used in a wider range of unlicensed bands, they offer afaster time-to-market, and in many cases a higher throughput than802.16e equipment. On the other hand, there is better support formobility and a wider range of terminal form factors advantages of802.16e equipment.

It’s certainly a consideration but no matterwhat you chose the migration paths to move in either direction areeasily achieved through overlay networks, software upgradeable basestations, dual mode devices and dual mode base stations. Thisconsideration assures you are not stuck in one mode or the wrong modeand that your initial investment is protected. Makes the CTO and CEOhappy.

WiMAX base stations transmit up to 30 miles, but becauseit is a cell-based topology, would yield a more typical range of 3 to 5miles. WiMAX systems can deliver a capacity of up to 75 Mbps perchannel, for fixed and portable access applications. This is enoughbandwidth to simultaneously support hundreds of businesses with T-1speed connectivity and thousands of residences with DSL speedconnectivity as we have seen.

WiMAX technology will beincorporated in portable computers and PDAs expected in late 2006 andearly 2007, allowing for urban areas and cities to become“MetroZones”,the new buzz word, for portable outdoor broadband wireless access. Inaddition, Wireless service providers and telecommunication equipmentindustries are embracing WiMAX technology because of its tremendouscost advantages to provide that last-mile connectivity to large partsof the world that are too expensive to serve with wired technologiesrequiring all that trenching.

Security

Due to thesecurity issues with WEP in the 802.11 Wi-Fi arenas, the standardsbodies took no chances with WiMAX, and wisely prioritized security fromthe onset. Base station designers went to work to assure a dedicatedhigh performance security processor. The WiMAX security standardrequires that all traffic be encrypted with CCMP (which is Counter Modewith Cipher Block Chaining Message Authentication Code Protocol).

Accordingto the WiMAX forum, the group's aim is for end-to-end authentication.WiMAX uses PKM-EAP (Extensible Authentication Protocol), which relieson the TLS standard following public key cryptography. Having addressedthis level of security from the start provides an excellent referencepoint to add multi-level security options as well, if yourimplementation requires an MLS approach. Secure (blacker)implementations would require such an approach.

What is Released?

Thefirst certification release for 802.16-2004 fixed is out there alreadyand includes products from certified vendors with two profiles in the3.5GHz and the 5.8GHz bands supporting fixed and nomadic access. Theprofiles for 802.16e mobile are not available nor released as of thiswriting but are expected to be in the ranges of 2.3GHz to 2.5GHz whenofficially released. WiMAX profiles based on 802.16-2004 are bettersuited to fixed applications that use directional antennas because OFDMis inherently less complex than SOFDMA used in the mobile application.As a results, 802.16-2004 networks will be deployed much faster and ata lower cost. Our experiences are with these released systems in the USand around the world in ground applications, mobile military, publicsafety and maritime applications.

Planning for WIMAX

Companies,cities or projects in maritime or ground systems in the US that havedecided to or are considering building and operating a WiMAX networkwill have a few important issues to consider. The initial spectrum forWiMAX in the USA is unlicensed spectrum in the 5GHz range. Given thisspectrum is open it will have inherent interference issues and riskswhich will require attention. There are many ways of overcominginterference issues. The answers come from a proper site selection,following your RF survey training and from the actual selectedequipment. So, the planning and site survey results remain the key toyour confident success.

Summary

WiMAX providesoptimized solutions for fixed, nomadic, portable and mobile broadbandwireless access. There are two flavors in various release andimplementation modes. The first is 802.16-2004 WiMAX with two initialfrequency profiles – the 3.5GHz and the 5.8GHz bandssupporting fixedand nomadic access in LOS and NLOS environments now. The other flavoris 802.16e WiMAX with expected profiles in the 2.3GHz and 2.5GHz rangesoptimized for dynamic mobile radio channels supporting hands-ff androaming --arriving by 2007. Another exciting technology for all of us.Have fun! an extended version of this Primer is presented inour OnLine-CTO e-magazine. Contact Gina Smith atonlinecto@networkanatomy.com