White PapersDespite the power of the US regulator, the FCC, to shape wireless networking standards, there is in fact no worldwide source of rules for the use of radio technology.
This means that any European looking at a new wireless technology arriving from the US, faces up to several years of uncertainty. The technology works fine, and we see it demonstrated. But will we be legal if we use it here?
Will we infringe reserved bands of spectrum? Or will be break rules about broadcast power that differ from country to country?
The 802.11a fast wireless LAN standard has been subject to a lot of this kind of rumour. The standard already faced a hurdle to overcome - the fact that it was pipped to the market by 802.11g, a fast wireless LAN standard on the more familiar 2.4GHz band, as opposed to 802.11a's 5GHz.
Users in Europe have suffered fear that, in using 802.11a, they might infringe some arcane spectrum regulation. That fear has been irrelevant over the last couple of years, during whith time hardly anyone has used 802.11a, but now there are signs that the 5GHz WLAN spec may be rising. Vendors defend the standard, analysts see sales increase, and users speak about improved performance.
Europeans thinking about 802.11a might still be worried that the standard is not legal here. But they need not fear. In February last year, the UK regulator Ofcom, approved 802.11a.
To be pedantic, Europeans are supposed to use a harmonised version of 802.11a, which has been referred to as 802.11h. Anyone selling 802.11a kit in EMEA must adhere to 802.11h, whihc includes two features from the defunct European wireless LAN standard, HIPERLAN.
These features are:
- Transmit Power Control, which adjusts the power depending on the position of the client, in order to minimise interference with other networks
- Dynamic Frequency Selection which shuts down the AP if it detects a radar signal.
Most vendors' .11a kit can pass .11h certification by demonstrating that transmit power can be controlled manually.
For more detail, read the white paper from Trapeze.
802.11a in Europe: Harmonization of the 5-GHz Spectrum Ends Patchwork of Frequencies and Simpli es Deployment802.11a, with higher throughput and greater channel diversity than 802.11b, is regarded as the preferred radio standard in the United States for enterprises looking to improve WLAN performance. However, European businesses, or multinational business with operations in Europe, have not had a similarly favorable view of 802.11a, because in Europe its use has been far more restricted and its regulations have varied widely by country.Concerns about interference with airport radar, which in Europe operates in the 5 GHz band, led countries to tightly control or even forbid the use of 802.11a, since it uses the same frequency band. While the more powerful 802.11 outdoor systems, used for building-to-building connectivity, were more likely culprits for interference than lower-powered indoor WLAN systems, understandably no one wanted to be responsible for rerouting an Airbus 320 landing at Heathrow.So European businesses faced a dilemma either negotiate the complexity of the country-by-country standards of permissible channels and limited frequencies, with more variables than a Eurail schedule, or forego the advantages of 802.11a in favor of the simpler 802.11b radio standard.Fortunately, the considerable confusion is clearing. With the summer 2003 meeting of the FCC World Radiocommunications Conference (WRC-03), most European countries now permit 802.11a and have opened up the majority of the 5 GHz spectrum for commercial use (see http://www.telematica.com/blog/stories/2003/07/04/wrcProposalForCompromiseOn5ghz.htmlfor coverage of the WRC results). The countries have largely agreed to common rules for AP transmit power limits, which the United States is expected to follow as well.Agreement over the frequencies and power levels used, called harmonization of the spectrum, signi cantly simpli es deploying 802.11a across Europe. This harmonization makes higher-throughput 802.11a deployments a practical reality. With standards now common throughput multiple geographies in Europe, it s easier for businesses to comply with regulations governing the use of 802.11a. And as the European Union and other countries worldwide agree to the same frequencies, transmit power levels, and veri cation tests, global interoperability improves. Business users can now look to a single wireless card to stay wirelessly connected across Europe, and IT operations bene t from being able to use the same WLAN products in different countries.Executive SummaryHarmonization of the 5GHz spectrum is bringing much needed relief to the confusion that has stalled deployment of the higher-throughput 802.11a in Europe. By 2004, most countries will support the same spectrum, frequencies, and tests to minimize potential interference with other systems operating in the same frequency, paving the way for U.S. multinationals and European companies to con dently and easily roll out 802.11a WLAN deployments." What s all the fuss about harmonization of the spectrum?" What s the impact of transmit power control and dynamic frequency selection?" How should a WLAN system vendor support 802.11a for deployment in Europe?Untitled DocumentViva La 802.11a802.11a usually runs at 36 Mbps from a distance of 75 feet, with a top theoretical speed of 54 Mbps. 802.11 also offers a wider radio spectrum than 802.11b. In Europe, 802.11a provides a total of 19 non-overlapping channels. Channel diversity, or the ability to use different channels on radios deployed together, greatly reduces the risk of co-channel interference, which degrades wireless performance.802.11b, in comparison, provides a raw data rate of 11 Mbps and a range of roughly 100 feet at that data rate. It s widely supported by client devices, offering good backward-compatibility and making it practical for providing wireless access to guests visiting a facility. The 802.11b signal penetrates objects well, enabling better coverage in locations hampered by RF obstacles. But all this exibility comes at a price. The 802.11b spectrum, in the 2.4 GHz range, is crowded with many other devices, including microwave ovens and portable telephones. In addition, the data rate is limited to 11 Mbps, and the technology supports only three concurrent channels, giving IT organizations far less exibility in where to deploy 802.11b radios. The 802.11g radio speci cation, which boosts speeds to 802.11a s 54 Mbps data rate, offers backward compatibility with 802.11b (with reduced performance) but provides only three non-overlapping channels.While 802.11b/g may continue to be used where low system throughput can be tolerated, 802.11a generally offers better throughput than 802.11b at any coverage distance. Because of its higher channel count, 802.11a is best where more aggregate system capacity and bandwidth for applications are required, since many more radios can be deployed in a given area with no co-channel interference.Of course, multiple radio technologies can be deployed simultaneously for the best of both worlds. Proof of peaceful co-existence can be seen in the 802.11a/b/g network interface cards and access points that have rapidly come to market. Most likely, you ll end up using multi-mode radios using 802.11a for performance and 802.11b/g for legacy devices and WLANs and for guest access.Enabling Widespread Use of 802.11a in EuropeHarmonization of the spectrum revolves around two key issues common spectrum and the ability to sidestep potential interference with airport radar. Most countries in Europe have opened up 450 MHz of the 5 GHz spectrum, increasing interoperability throughout Europe and making it easier for business travelers to use the same WLAN adapter cards when traveling to multiple countries. No longer do you have to carry a stack of WLAN cards approved for each country or, worse yet, run the risk of violating the law. Interoperability simpli es WLAN deployment for IT organizations, enabling them to better leverage their WLAN designs and simplify purchasing and sparing of equipment.Core to reducing possible interference with European radar systems are two technologies Transmit Power Control (TPC) and Dynamic Frequency Selection (DFS). Transmit Power Control. TPC enables IT managers to control how far the AP can transmit, thus controlling the cell size. In Europe, APs cannot transmit higher than 50 milliWatts (mW) or 17 dBm, although many APs have the ability to transmit up to 100 mW (20 dBm). APs need to be turned down in Europe to reduce the chance of interference with a nearby airport. Of course, lowering a radio s transmit power means that the service area of that radio will decrease. In addition, the AP transmits additional power-related information elements (IE) in 802.11 control packets, such as beacons and probe responses. Client must use this information for TPC purposes.Dynamic Frequency Selection. With DFS, before an AP transmits on a channel, it listens to see if radar is in use nearby. If the AP detects radar, it shuts down and disassociates its clients, forcing them to be quiet for a brief time. By this year, 2004, DFS is required by all countries in the EU. Fortunately, detecting the presence of radar is based on a common test, European Telecommunications Standards Institute (ETSI) 301-893.Page 2Untitled Document802.11a At-A-GlanceSupport for 802.11a in Europe from Your WLAN VendorHarmonization of the spectrum has relieved users and IT managers from knowing which frequencies and transmit levels are allowed for each country in Europe. With the implementation of DFS and TPC, the WLAN system can handle the interference concerns raised in the past.Requirements are outlined in the 802.11h draft standard, which enhances the network management and control for spectrum and transmit power management in the 5 GHz band. While 802.11h has its origins in meeting European requirements, it is starting to be adopted by other countries, such as the U.S., as part of the global ITU Radio Regulations (see http://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-241220A1.pdf for an example of a US Federal Communications Commission ruling to better align spectrum allocation with results from the 2003 World Radio Conference).Look closely at how your WLAN system vendor supports 802.11a operation in Europe. If a user s 802.11 client card or chipset is up to date, it will support IEEE 802.11d, which de nes physical layer requirements that conform to regulatory requirements outside the U.S., Europe, and Japan. 802.11d enables the AP to transmit a country code when it powers up, telling the client card the country of operation. The client card should also support and understand the TPC function speci ed in 802.11h. TPC and DFS must be supported in the WLAN switch or AP as well. A WLAN system vendor should enable you to choose your country of operation as your rst choice, and then self-con gure to give you the maximum power and which frequencies it will use to choose channels for all three bands 802.11a/b/g. For instance, if you choose the Netherlands, all the rules from the Netherlands should be applied automatically.Some vendors do not have a database for country of operation but instead stock different actual products for each region, forcing the IT department of multinational companies to order and spare multiple product types. Having multiple products customized for each country doesn t help the WLAN vendor achieve the economies of scale of mass manufacturing, and surely the companies pass these costs on to you.An ideal WLAN system should enable the IT manager to set the transmit power by easily selecting the country of operation through software. Any other approach runs the risk that an IT manager will neglect to set the transmit power control because it s simply too dif cult, putting the company in violation of EU regulations.Page 35.15 GHz to 5.35 GHzBand8 channels (36, 40, 44, 48, 52, 56, 60, 64)5.47 GHz to 5.725 GHZ11 channels (100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140)ChannelsBand is common between Europe and the US. It s used in almost every European country.Band is available in some European countries now and is expected to be available in all European countries by late 2004. Made available in the U.S. in late 2003.5.725 GHz to 5.85 GHz5 channels (149, 153, 157, 161, 165)Band is available in U.S., Canada, and China but is not permitted in the EU.UseUntitled DocumentIn SummaryHarmonization of the spectrum is vastly simplifying the deployment of 802.11a, enabling companies operating in Europe to gain the bene ts of 802.11a s higher throughput and reduced co-channel interference. With the addition of TPC and DFS, the concerns about potential interference with radar are alleviated, thus paving the way for widespread use of the higher-throughput 802.11a in Europe. 5753 W. Las Positas Blvd., Pleasanton, CA 94588 Phone 925.474.2200 Fax 925.251.0642Trapeze Networks, the Trapeze Networks logo, the Trapeze Networks flyer icon, Mobility System, Mobility Exchange, MX, Mobility Point, MP, Mobility System Software, MSS, RingMaster, AAA Integration and RADIUS Scaling, AIRS, FastRoaming, Granular Transmit Power Setting, GTPS, Layer 3 Path Preservation, Location Policy Rule, LPR, Mobility Domain, Mobility Profile, MultibandSweep, Passport-Free Roaming, SentrySweep, Time-of-Day Access, TDA, TAPA, Trapeze Access Point Access Protocol, Virtual Private Groups, VPGs and Virtual Site Survey are trademarks of Trapeze Networks, Inc. Trapeze Networks SafetyNet is a service mark of Trapeze Networks, Inc. All other products and services are trademarks, registered trademarks, service marks or registered service marks of their respective owners. 2004 Trapeze Networks, Inc. All rights reserved. WP-80211aERP-402Recommended ReadingFor more information on enterprise WLANs, please read:" 802.11 Tutorialhttp://www.trapezenetworks.com/technology/market/tutorial.asp" Designing Enterprise WLANs for Capacity vs. Coveragehttp://www.trapezenetworks.com/technology/whitepapers/designingWLANs.asp
