Guide to Wireless LAN Technologies - Alachua Freenet

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Guide toWireless LAN Technologies

Guide to Wireless LAN Technologies2

Table of ContentsIntroduction ................................................................................................................................................... 2Wireless LAN Topologies .............................................................................................................................. 3Wireless LAN Technologies .......................................................................................................................... 4

Infrared (IR) .............................................................................................................................................. 5UHF (Narrowband) .................................................................................................................................. 5Unlicensed Radio Frequency Bands ........................................................................................................ 8

900 MHz ............................................................................................................................................... 82.4 GHz ................................................................................................................................................ 85.0 GHz ................................................................................................................................................ 9

Spread Spectrum Technologies................................................................................................................ 9Direct Sequence ................................................................................................................................... 9Frequency Hopping ........................................................................................................................... 10

Strengths and Weaknesses of DSSS and FHSS Radio Technologies .................................................... 10Wireless LAN Standards ......................................................................................................................... 12

Considerations for Selecting a Wireless LAN Solution .............................................................................. 13Business Considerations ......................................................................................................................... 13Technical Considerations ....................................................................................................................... 15

Wireless LAN Solutions from Intermec Technologies ............................................................................... 18

IntroductionCustomers are confronted today with a widevariety of wireless technologies, systems, andvendors to address needs for wireless data collec-tion. However, most customers will find that nosingle wireless solution is suitable for all applica-tions. For example, low-volume messaging can beserved by the many available options for two-waypaging and narrowband PCS (Personal Communi-cation System). For higher data volumes, WirelessLANs (WLANs) offer an excellent solution for alocal area. For wireless communications across acity, state, or country, wireless metropolitan orwide-area network options are possible solutions.Vendors such as Analog Cellular, Bell South (for-merly RAM), Ardis, GSM, GPRS, TETRA, DECT,Digital Cellular, or PCS may offer solutions forintegrated voice/data across a wide area. Finally,GEO (Geostationary Earth Orbit) and LEO (LowEarth Orbit) satellite solutions are increasinglyavailable on a global scale.

While customers may choose from manywireless data solutions, the majority of customersselect a WLAN system to meet data requirements.WLANs provide high-speed, reliable data commu-nications in a building or campus environment aswell as coverage in rural areas. Wireless LANs aresimple to install and do not incur monthly userfees or data transmission charges.

WLAN technologies emerged in the 1980s asa viable alternative to and extension of wiredLANs for various business applications. Some ofthe earliest uses were associated with bar codedata collection activity; Radio Frequency DataCollection (RFDC) has proliferated in warehous-ing and retail markets. More recently, manufactur-ers have deployed WLANs for process and qualitycontrol applications. Retail applications haveexpanded to include wireless Point of Sale (POS).Healthcare and education are also fast growingmarkets for WLANs.

Horizontal applications such as e-mail andscheduling, intranet and Internet access are alsoexpected to accelerate overall market growth. Inaddition, WLANs offer cost-effective networkingsolutions for hard-to-wire and historical buildings,outdoor events, and on-site training. Users ofWLAN systems often see paybacks in six to ninemonths and return on investments of 200 to 300percent.

This guide reviews and explains WLANtechnology alternatives, and provides guidanceon selecting a suitable WLAN system.

Guide to Wireless LAN Technologies 3

PEER TO PEER CONFIGURATION

WIRELESS CLIENTS

WIRELESS“CELL”

Wireless LAN TopologiesWireless LANs can be built with either of twotopologies: peer-to-peer or access point-based. Ina peer-to-peer topology, client devices within thewireless cell communicate directly to each otheras depicted in Figure 1.

An access point is a bridge that connects awireless client device to the wired network. Anaccess point-based topology uses access pointsto bridge traffic onto a wired (Ethernet or TokenRing) or wireless backbone as shown in Figure 2.The access point enables a wireless client deviceto communicate with any other wired or wirelessdevice on the network. The access point topologyis more commonly used, demonstrating thatWLANs do not replace wired LANs, they extendconnectivity to mobile devices.

Figure 2. In a topology based on access points, wireless

devices can connect to the wired LAN backbone for com-

munication with both wired and wireless nodes.

Figure 1. In a peer-to-peer topology, wireless devices create a LAN by

communicating directly with each other.

WIRELESS CLIENTS

ACCESS POINT CONFIGURATION

WIRELESS CLIENTS WIRELESS

CLIENTS

LAN BACKBONE

ACCESS POINT

ACCESS POINT

ACCESS POINTWIRELESS

“CELL”

WIRELESSREPEATER


Another popular wireless network topologyis the point-to-point or point-to-multipoint bridge.A bridge is defined as a node (or pair of nodes)with a transceiver client device that connects twonetworks using similar protocols. Wireless bridgesconnect a LAN in one building to a LAN in an-other, even if the buildings are many miles apart(see Figures 3 and 4). These connections requirea clear line-of-sight (i.e., no obstacles, such asbuildings, hills or trees) between the buildings.The line-of-sight range varies based on the typeof wireless bridge and antenna used as well asenvironmental conditions.

WLAN clients are available in a number ofform factors for use in any of these network to-pologies. Personal computers (PCs) can connectto a WLAN using ISA and PC adapter cards.Wireless modems can attach to parallel ports,RS232, 10BaseT, IRDA, or other popular physicalinterfaces on a PC or other device. In this con-figuration, the client device communicates via thephysical interface (e.g. ISA or PC Adapter, RS232,etc.) to the radio device, which in turn providesthe physical interface to the WLAN. For portableapplications, the most common configurations arePCMCIA adapter cards for laptop computers andintegrated LAN modules for application-specific,hand-held terminals.

Wireless LAN TechnologiesThe technologies available for use in WLANsinclude infrared, UHF (narrowband) radios, andspread spectrum radios. Two spread spectrumtechniques are currently prevalent: frequencyhopping and direct sequence. In the UnitedStates, the radio bandwidth used for spreadspectrum communications falls in three bands(900 MHz, 2.4 GHz, and 5.7 GHz), which theFederal Communications Commission (FCC)approved for local area commercial communica-tions in the late 1980s. In Europe, ETSI, theEuropean Telecommunications Standards Insti-tute, introduced regulations for 2.4 GHz in 1994,and Hiperlan is a family of standards in the5.15-5.7 GHz and 19.3 GHz frequency bands.

Figure 4. A wireless bridge connects the LAN backbones in separate buildings

or locations.

WIRELESS BRIDGING

BRIDGE

BRIDGE

LAN BACKBONE

LAN BACKBONE

POINT-TO-POINT WIRELESS BRIDGE

BUILDING #2

BUILDING #1

Figure 3. A point-to-multipoint bridge topology is useful for a campus or nearby

buildings.

POINT TO MULTIPOINT WIRELESS BRIDGE

RESEARCH CENTER

MANUFACTURING PLANT

HEADQUARTERS


Infrared (IR)Infrared is an invisible band of radiation thatexists at the lower end of the visible electromag-netic spectrum. This type of transmission is mosteffective when a clear line-of-sight exists betweenthe transmitter and the receiver.

Two types of infrared WLAN solutions areavailable: diffused-beam and direct-beam (orline-of-sight). Currently, direct-beam WLANs offera faster data rate than diffused-beam networks,but is more directional since diffused-beam tech-nology uses reflected rays to transmit/receive adata signal, it achieves lower data rates in the1-2 Mbps range.

Infrared optical signals are often used in re-mote control device applications. Users who canbenefit from infrared include professionals whocontinuously set up temporary offices, such asauditors, salespeople, consultants, and managerswho visit customers or branch offices. These us-ers connect to the local wired network via aninfrared device for retrieving information or usingfax and print functions on a server.

A group of users may also set up a peer-to-peer infrared network while on location to shareprinter, fax, or other server facilities within theirown LAN environment. The education and medi-cal industries commonly use this configuration toeasily move networks.

As noted in Table 1 below, infrared is a short-range technology. When used indoors, it can belimited by solid objects such as doors, walls,merchandise, or racking. In addition, the lightingenvironment can affect signal quality. For

example, loss of communications may occur be-cause of the large amount of sunlight or back-ground light in an environment. Fluorescent lightsalso may contain large amounts of infrared. Thisproblem may be solved by using high signalpower and an optical bandwidth filter, whichlessens the infrared signals coming from outsidesources. In an outdoor environment, snow, ice,and fog may affect the operation of an infrared-based system.

Because of its many limitations, infraredis not a very popular technology for WLANs.According to Frost & Sullivan, infrared has lessthan 14 percent of the in-building WLAN market,and this market share is expected to drop in thefuture.

UHF (Narrowband)UHF wireless data communication systems havebeen available since the early 1980s. Thesesystems normally transmit in the 430 to 470 MHzfrequency range, with rare systems using seg-ments of the 800 MHz range. The lower portionof this band 430-450 MHz is often referenced asunprotected (unlicensed) and 450-470 MHz isreferred to as the protected (licensed) band. Inthe unprotected band, RF licenses are not grantedfor specific frequencies and anyone is allowed touse any frequency in the band. In the protectedband, RF licenses are granted for specific frequen-cies, giving customers some assurance that theywill have complete use of that frequency.Other terms for UHF include narrowband and400 MHz RF.

Because independent narrowband RF systemscannot coexist on the same frequency, govern-ment agencies allocate specific radio frequenciesto users through RF site licenses. A limitedamount of unlicensed spectrum is also availablein some countries. In order to have many fre-quencies that can be allocated to users, the band-width given to a specific user is very small.

The term “narrowband” is used to describethis technology because the RF signal is sent in avery narrow bandwidth, typically 12.5 kHz or25 kHz. Power levels range from 1 to 2 watts fornarrowband RF data systems. This narrow band-width combined with high power results in larger

Table 1. Considerations for ChoosingInfrared Technology

Infrared

Advantages No government regulations controllinguse

Immunity to electro-magnetic (EMI)and RF interference

Disadvantages Generally a short-range technology(30-50 ft. radius under ideal conditions)

Signals cannot penetrate solid objects

Signal affected by light, snow, ice, fog.

Dirt can interfere with infrared


transmission distances than are available from900 MHz or 2.4 GHz spread spectrum systems,which have lower power levels and widerbandwidths.

According to Venture Development Corpora-tions (VDC) 1996 Report on the Data CollectionTerminal Market, UHF radio shipments in the ADC(Automated Data Collection) RF Portable DataCollection Market accounted for 23 percent ofwireless ADC device revenue and 28 percent ofwireless ADC device units in 1995. The growthrate for the UHF radio ADC devices was 9.1 per-cent (1994 to 1995), which compared to a 19.5percent growth in spread spectrum ADC devicesduring the same time period. VDC made noprojections regarding UHF sales into the future.

Bob Egon of the Gartner Group estimates that80 percent of new clients inquire about and selectspread spectrum-enabled devices for their wirelessdata collection needs. The other 20 percent selectUHF-enabled devices.

Synthesized Radio Technology

Many modern UHF systems use synthesizedradio technology, which refers to the waychannel frequencies are generated in the radio.The crystal-controlled products in legacy UHFproducts require factory installation of uniquecrystals for each possible channel frequency.Synthesized technology uses a single, standardcrystal frequency and derives the required channelfrequency by dividing the crystal frequency downto a small value, then multiplying it up to thedesired channel frequency. The division andmultiplication factors are unique for each desiredchannel frequency, and are programmed intodigital memory in the radio at the time ofmanufacture.

Synthesized UHF-based solutions provide theability to install equipment without the complex-ity of hardware crystals. Common equipment canbe purchased and the specific UHF frequencyused for each device can be tuned based uponspecific location requirements. Additionally, syn-thesized UHF radios do not exhibit the frequencydrift problem experienced in crystal-controlledUHF radios, a feature that eliminates tuning prob-lems after installations have been running for aperiod of time.

Multiple Frequency Operation

Modern UHF systems allow access points to beindividually configured for operation on one ofseveral pre-programmed frequencies. Terminalsare programmed with a list of all frequenciesused in the installed access points, allowing themto change frequencies when roaming. To increasethroughput, access points may be installed withoverlapping coverage but using differentfrequencies.

Table 2. Considerations for choosingUHF technology

UHF Radio

Advantages Longest Range

Low cost solution for large sites withlow to medium data throughputrequirements

Disadvantages Low throughput

No multi-vendor interoperability

Interference potential

RF Site License required for protectedbands

Large radio’s and antenna’s increasewireless client size

Table 3. Wireless Range Comparison by RF Technology: Typical Warehouse and Outdoors

Wireless Technologies Indoor Range Ratio* Outdoor Range

400 MHz UHF 300-400 Ft Range 300-500K Sq. Ft. 1 - 2 Miles

900 MHz Spread Spectrum 220-350 Ft Range 150-200K Sq. Ft. 2:1 3000-5000 Ft. Range

2.4 GHz Spread Spectrum 2.5 to 6:1

100 mW U.S. and Asia Pacific/Latin America 150-200 Ft Range 70-125K Sq. Ft. 4:1 1200 Ft. Range

500 mW U.S. and Asia Pacific/Latin America 200-250 Ft Range 125-200K Sq. Ft. 2.5:1 1800 Ft. Range

100 mW Europe 125-150 Ft Range 50-70K Sq. Ft. 6:1 600 Ft. Range

* Number of radios required to provide coverage equivalent to one UHF radio.


Narrowband Wireless Advantages

Table 2 lists the advantages and disadvantages ofUHF technologies. The chief advantage of UHF-based systems is range. These systems are opti-mum solutions for large sites with low-to-mediumdata throughput requirements. Table 3 summarizesthe wireless range for UHF compared to other RFtechnologies in a typical warehouse environmentand outdoors in open air.

Typically, two 900 MHz access points or moreare required to cover the same area as one UHFbased access point. With 2.4 GHz access points,the ratio of UHF access points is 2.5:1 or more inthe US and Asia Pacific/Latin America and 6:1 inEurope at a minimum. The higher ratio for Europeis caused by regulations on radiated output power,which limits spread spectrum radios to 100mWEquivalent Isotropic Radiated Power (EIRP).European regulations have effectively eliminatedany high gain antenna technologies that increasethe radiated power above the maximum limit of100mW EIRP. In addition, European companiescan not deploy 900 MHz radio systems becausethis spectrum is used in Global System for MobileCommunications (GSM) cellular telephonesystems. UHF systems offer lower infrastructurecosts because of their 6:1 radio ratio, a major fac-tor in the continued use of UHF radios in Europe.

Narrowband Wireless Disadvantages

Throughput

While UHF wireless systems can cover largerareas with each radio transmitter than 900 MHz or2.4 GHz spread spectrum systems, they also sup-port very low data rates. UHF systems offer dataspeeds ranging from 4,800 to 19,200 bits per sec-ond (bps); see Table 4 for a comparison to othertechnologies. The speed disadvantage of UHFsystems results in fewer transactions per secondor support for fewer overall devices.

When selecting a wireless system, customersshould consider future growth and support foradditional devices and applications. For manyUHF customers, future growth can only be sup-ported with a clear migration path to 2.4 GHz orwith hybrid systems. For new installations andto support future growth, customers will typicallychoose directly to install spread spectrum APs.

Interoperability

Because UHF systems are proprietary, they com-municate only with devices manufactured by thesystem vendor. This limitation does not give acustomer the freedom to choose devices frommultiple companies. 900 MHz wireless systemsalso have this disadvantage. If interoperability isrequired, open standard 2.4 GHz wireless LANsystems are the better choice. 2.4 GHz wirelessLAN standards available today include the WLIForum OpenAir Standard for 2.4 GHz frequencyhopping and the IEEE 802.11 Standards forintrared, 2.4 GHz frequency hopping, and2.4 GHz direct sequence.

Interference

Any interference from outside sources within acustomer’s bandwidth will disrupt wireless datacommunications. Interference in unprotected(unlicensed) bands can be caused by unintentionalradiators such as other industrial users, or anotherwireless system or radio using the same RF fre-quencies. But even in protected (licensed) bandsinterference can also be caused by unintentionalradiators such as factory equipment, welders, andforklifts. When a UHF system encounters interfer-ence, data communications are degraded, howevernarrowband equipment easily handles interferencethat is not on its operational channel.

RF Site License Required

Because the UHF radio spectrum is limited andindependent UHF systems operating on thesame frequency can not coexist in the same area,radio authorities in each country must regulateand license specific frequencies to customers.Obtaining RF site licenses is time consuming andpotentially costly. Additionally, many cities haverun out of available frequencies, which meansobtaining a license is very difficult or impossible.In comparison, spread spectrum systems communi-cate in the unlicensed ISM (Industrial, Scientific,and Medical) band. As those systems aredesigned to coexist with others, no license isrequired for installation or operation.

Table 4. Data Rates for WLAN Technologies

Wireless Technology Data Rates

400 MHz UHF 4.8 - 19.2 Kbps

900 MHz Spread Spectrum 100 - 400 Kbps

2.4 GHz Spread Spectrum 1 - 2 Mbps

2.4 GHz Future More than 10 Mbps

5.7 GHz Future More than 20 Mbps


Large Radios and Antennas

Because UHF radios are typically larger thanspread spectrum radios, UHF end devices arelarger than spread spectrum devices. In today’sdata collection environment, smaller devices havebetter market potential.

External UHF antennas are also longer, as theRF wavelengths for 450 MHz signals are longerthan those for 900 MHz or 2.4 GHz RF signals.Users of portable devices prefer integrated anten-nas that do not get in the way of the devicesoperation or the users activity.

Unlicensed Radio Frequency Bandsabove 900 MHzIn 1985, the FCC authorized the use of spreadspectrum radio technology in the 902-928 MHz,2.400-2.4835 GHz, and 5.725-5.850 GHz frequencybands. FCC Part 15 rules allow unlicensed use ofspread spectrum data communications in thesebands. Commonly referred to as 900 MHz,2.4 GHz, and 5.7 GHz, these frequencies are alsoknown as ISM bands. Tables 5 and 6 list theadvantages and disadvantages of 900 MHz and2.4 GHz technologies.

900 MHz

The 900 MHz band has been the most popular forearly WLAN applications, based on the availabilityof products introduced in the early 1990s. How-ever, the market has been slowly shifting to morerecently developed 2.4 GHz products. Very fewproducts use the 5.7 GHz band today, primarilybecause of its high cost, limited availability ofparts, and technical limitations.

In spite of these limitations, thousands of900 MHz WLANs have been implemented, sup-porting hundreds of thousands of devicessuccessfully for critical business applications.

2.4 GHz

The 2.4 GHz band is three times larger than the900 MHz band, making it feasible to support fasterdata rates and higher overall system capacities.This band, while more limited in range than900 MHz, has an advantage in aggregate speed.Transmission on the 2.4 GHz band is “cleaner,”because it carries less competing traffic. A2.4 GHz system is a better choice for marketsoutside the U.S., particularly Europe and Japan.In addition, the new Wireless LAN standards suchas IEEE 802.11 and WLIF OpenAir are based uponthe 2.4 GHz frequency band. Together these fac-

Table 5. Considerations for Choosing 900 MHzTechnology

900 MHz

Advantages Good balance of range and data rate

Data rates of 100,000 to 450,000 bps aresufficient for many WLAN applications

Typically larger coverage areas thansimilar 2.4 GHz systems

Disadvantages Not available for use in Europe or Asiabecause this band is reserved for GSMcellular telephone systems

Companies with sites around the globecannot standardize on 900 MHz basedsolutions for all locations

Only a few manufacturers offer900 MHz systems

No Interoperability; each vendor em-ploys proprietary radio protocols

900 MHz band is more crowded thanother frequency bands. In the U.S., thisband is used for cordless telephones,devices to extend in-home TV signals,vehicle locating systems, and othernon-spread spectrum applications.Internationally, the band is widely usedfor cellular or military communications

Table 6. Considerations for Choosing 2.4 GHzTechnology

2.4 GHz

Advantages Worldwide acceptance for installationand use in most countries

The industry is moving towards stan-dards-based systems, meaning multi-vendor support for common WLANinfrastructures

Data rates supported are 800,000 to2,000,000 bps with higher rates in thefuture

Disadvantages Limited range. Because the systemstransmit less power (typically 1/10thof a watt) and 2.4 GHz has poorerpropagation characteristics, the cover-age area for a given radio and accesspoints can be significantly less thanthat of 900 MHz or UHF systems

Decreased range can lead to significantincreases in system infrastructure costsfor large buildings, multi-story build-ings, or campus environments

Outdoor installations may be difficultor impossible to cover


DIRECT SEQUENCE SPREAD SPECTRUM

POWER

STARTFREQUENCY CHANNELS

STOPFREQUENCY

SIGNAL SYMBOL SPREAD WITH A SEQUENCE• EACH SYMBOL IS DIVIDED INTO 11 CHIPS. A SIMPLE MAJORITY NEEDS TO GET THROUGH

WIDER BANDWIDTH / LOW POWER DENSITY

tors have made 2.4 GHz the primary band ofchoice for customers today.

Microwave ovens represent the primary inter-ference in the 2.4 GHz band. However, spreadspectrum techniques and good installation prac-tices can minimize this interference.

New developments will overcome many ofthe current limitations of 2.4 GHz technology,such as increasing data rates to 10 Mbps orhigher. New radios will increase the range of2.4 GHz wireless LANs and reduce the cost differ-ential between 2.4 GHz and 900 MHz systems.Wireless access points can make outdoor installa-tions possible where no network cables are ac-cessible, when authorized for use.

5 GHz

Products based on the highest of the availableISM bands, 5 GHz, are still largely experimental.It will be the year 2000 or later before WLANproducts in this band become viable for commer-cial applications. In the U.S., development of5.7 GHz technology will be closely tied to theNational Information Infrastructure (NII), a federalprogram for new communications technologies.Although the 5.7 GHz frequency band willsupport higher data rates than current systems,it must overcome challenges for range and powerconsumption.

Spread Spectrum TechnologiesDuring World War II, the U.S. military developedspread spectrum techniques for secure voicecommunications. By operating across a broadrange of radio frequencies, a spread spectrumdevice could communicate clearly despite inter-ference from other devices using the same spec-trum in the same physical location. In additionto its relative immunity to interference, spreadspectrum makes eavesdropping and jamminginherently difficult. To decode the signal from aspread spectrum device, a receiver must knowthe specific spreading pattern of the transmitter.

In commercial applications, spread spectrumtechniques currently offer data rates up to2 Mbps. Because the FCC does not require sitelicensing for the bands used by spread spectrumsystems, this technology has become the standardfor high-speed RF data transmission.

Two modulation schemes are commonlyused to encode spread spectrum signals: directsequence and frequency hopping.

Direct Sequence

Direct Sequence Spread Spectrum (DSSS) systemimplementations can vary. To illustrate the basictechnology, this discussion presents the 2.4 GHzapproach defined by the IEEE 802.11 WirelessLAN standard (see Figure 5). Currently, DSSSprovides a 1 or 2 Mbps data rate over the air,with 11 Mbps and higher data rates coming inthe near future.

A DSSS system uses a relatively wide 22 MHzchannel. In the U.S. and much of Europe, threenon-overlapping and two overlapping channelsare available in the 2.4 GHz band. In Japan, onlyone 22 MHz band is available and regulations inother countries allow for 1, 2, or 3 channels.Typically, all access points in a given WLANnetwork are on the same 22 MHz channel. Ifone channel is subject to more interference,the system can move to another.

Direct sequence works by converting eachbit/symbol into an 11-bit “chip” sequence with alogic ‘0’ sequence being the compliment of a ‘1’sequence. The chip rate is eleven times the origi-nal bit / symbol rate. A correlator is used with thespreading code that determines how many of thereceived chips match the ‘1’ sequence and the ‘ø’sequence. The greater of the two matches deter-mines if the received data is a ‘1’ or a ‘0’.

Immunity to interference and system rangecan be improved by increasing the number ofchips per bit/symbol, although the data rate willdecrease if the bandwidth remains constant (orthe number of channels will decrease if the datarate is constant).

Figure 5.


Because DSSS radio designs are complexand the required components are more costly,DSSS technology is typically more costly thanfrequency hopping technology. However, totalsystem costs for DSSS may be less if fewer accesspoints are needed than would be required for acomparable implementation based on frequencyhopping technology.

Frequency Hopping

Although Frequency Hopping Spread Spectrum(FHSS) systems allow for a variety of implementa-tions, this discussion presents the IEEE 802.11implementation.

In frequency hopping, the signal hops amonga variety of frequencies, with the exact sequenceof changes (the hopping sequence) known onlyto the stations participating in the communication.At any instant in time, the signal is being broad-cast on only one frequency, and the transmissionremains on each frequency for only a short pe-riod of time (up to 0.4 second) before moving tothe next frequency. Thus, interference on a singlefrequency, or even several frequencies, is notsufficient to disrupt the communication.

A 2.4 GHz FHSS system uses 79 channels,each 1 MHz wide (most countries). The signal“hops” the entire band using a pseudo-randomsequence (see figure 6). All units in a given cellmust hop at the same time. Each device hopsusing the same pseudo-random sequence over

and over again, but the devices must be synchro-nized. This is accomplished by all units knowingthe pattern of hopping, the duration on each hop,and the current time of the hop sequence.

Because the signal moves around the bandrapidly, FHSS systems can avoid interferencemuch of the time. The FHSS system sends packetsof data, checks them for errors, and if an error ina packet occurs, retransmits the packet, often inanother hop. As interference increases, the FHSSsystem performance degrades gradually.

Up to 1 Mbps over-the-air data rates in FHSSsystems are possible using two-level FrequencyShift Keying (FSK) modulation in the 802.11 stan-dard. Higher rates are possible using multi-levelmodulation. For example, 2 Mbps data rates arepossible using four-level FSK as defined by the802.11 standard. However, the RF range is re-duced when multi-level modulation is used.Current four-level FSK radios will result in aboutone-half the range of two-level FSK. This means awell-designed WLAN device operating at 2 Mbpswill typically have half the range of 1 Mbpsoperation. A poorly designed system can havesubstantially less range at 2 Mbps.

Strengths and Weaknesses of DSSSand FHSS Radio TechnologiesWireless LAN vendors have debated the merits ofthe two spread spectrum techniques for a numberof years. Typically, the arguments have beenslanted to favor the technology each vendormanufactures. Table 7 summerizes key differ-ences from a customer’s perspective.

Most WLAN applications used today in ware-housing, retail, factory and healthcare applica-tions require substantially less than 1 Mbps data

High Performance

Table 7. Frequency Hopping versus DirectSequence Technologies

Technology Key Considerations

Frequency Hopping Lower cost radio’sEconomic Solutions

Provides a per-node bandwidthabout 50% of a DSSS system

Can scale above 10 Mbps byadding more access points

Direct Sequence Increased range: Best suited forlarge coverage areas

Higher data rates: Migration to11 Mbps solutions of the future

Fewer access points required:Lower total system costs

FREQUENCY HOPPING SPREAD SPECTRUM

CHANNELS

STARTFREQUENCY TIME

STOPFREQUENCY

HOPS FROM ONE FREQUENCY TO ANOTHER AT A SPECIFIC HOPPING RATE IN A SET SEQUENCE

• 79 — 1 MHz WIDE CHANNELS

• MULTI-USE OF BAND AND INTERFERENCE IMMUNITY BY CONSTANTLY MOVING AROUND FROM FREQUENCY TO FREQUENCY

Figure 6.


rates, making FHSS more cost-effective. As wire-less requirements for multimedia and other dataintensive applications emerge, DSSS technologyis likely to be favored for its higher bandwidth.

Data Rates

The “over-the-air” data rates quoted by wirelesssystem vendors are often deceiving because theydescribe potential speeds, not the actual perfor-mance a user will experience. A more relevantconsideration is throughput and response time.The system architecture of a WLAN has a muchmore significant impact on throughput and re-sponse time than the chosen radio technology.

The over-the-air data rate will favor DSSS bya factor of two-to-one at a given range and givensimilar implementations in terms of transmitpower, antenna system, and other radio para-meters of DSSS and FHSS systems. A 2 MbpsDSSS system offers comparable range to 1 MbpsFHSS technology. With DSSS, virtually all of theair time can be used for data throughput, whileFHSS systems cannot send data while units hopfrom one channel to another.

Range

The range of each spread spectrum technologydepends on a number of implementation details.These details include transmit power, antennasystem (including antenna gain, cable loss, andwhether diversity/multiple antennas are used)and radio sensitivity. Because DSSS processingassists range, this technology could theoreticallyhave a more consistent range than FHSS at agiven data rate in a multipath environment. Awell designed DSSS system will offer more rangethan a FHSS system, lowering wireless LAN infra-structure costs. However, a well-designed FHSSsystem will offer more range than a poorly imple-mented DSSS system.

Scalability

FHSS proponents claim that frequency hopping ismore scalable than DSSS. This claim is based onthe notion of using multiple access points in eachcell to increase the overall data capacity availableto users in any given cell. A DSSS system has anabsolute limit of three non-overlapping channels;by stacking three access points in a cell the totalcapacity available is limited to 6 Mbps. WithFHSS, the upper limit is much more difficult todetermine.

For FHSS, the IEEE 802.11 standard defines79 possible hopping sequences. Some vendorshave claimed that 25 Mbps of capacity is possiblethrough the co-location of many access points,but these claims are not based on sound engi-neering or analysis. The real answer to scalabilityrequires a thorough analysis of the impact of co-locating FHSS access points.

The IEEE 802.11 hopping sequences are de-signed so that if any two hopping sequences areused, a collision on the same channel will occuronly once during the time that two access pointswould hop through the entire sequence. In real-ity, collisions occur more frequently. Since theFHSS system is packing 1 Mbps of data in a1 MHz wide channel, the 802.11 specificationallows for a significant amount of the transmittedinterfering RF to spill over into adjacent channels(see Figure 7).

As shown in figure 7, on each hop the FHSSsystem occupies up to five channels. It may bepossible to limit the interference to the outerchannels, but the Intermec model indicates thatmost WLAN implementations will experiencethis type of interference. Where the hoppingsequences are designed to collide only once intheory during a run through of all hops, in prac-tice each hop of an access point will collide withfive out of the 79 available channels.

WIRELESS CAPACITY PER CELL

10

1

2

3

4

5

6

7

8

9

2 3 4 5 6 7 8

NUMBER OF ACCESS POINTS

9 10 11 12 13 14 15 16

1 Mbps FH vs. 2 Mbps DS

Mbp

s CAP

ACITY

FH

DS

Figure 7.


In a DSSS system, three access points reachthe capacity limit of 6 Mbps. With FHSS, up to16 access points can be added to achieve a littlemore than 8 Mbps of capacity. With more than16 access points, the cell capacity declines be-cause the additional access points add moreinterference than data capacity. As this analysisindicates, FHSS is more scalable, but at a signifi-cant cost in terms of the number of access pointsrequired to gain additional capacity (see Figure 8).

Cost

Today, DSSS technology is more costly than FHSStechnology. With all things equal in terms ofspecifications such as frequency band and trans-

Figure 9.Figure 8.

Table 8: Wireless LAN Standards

Standard Scope

WLI Forum OpenAir 2.4 GHz frequency hopping spread spectrum

IEEE 802.11 Defines wireless LAN interoperability amongmulti-vendor products, infrared, 2.4 GHz frequencyhopping, and 2.4 GHz direct sequence spreadspectrum. Future 2.4 GHz and 5 GHz highspeed standards

Home Radio Frequency Shared Wireless Access Protocol (SWAP) for wirelessWorking Group networking within a home‘HomeRF’

BlueTooth Consortium Short-range radio links using 2.4 GHz frequencyhopping spread spectrum

mit power, DSSS radios are typically more expen-sive than FHSS radios. For systems where a1 Mbps data rate is sufficient, FHSS is more cost-effective to deploy. When data rate requirementsexceed 1 Mbps, DSSS is more attractive from acost standpoint.

The reason for this cost difference is that toequal the capacity of DSSS at 2 Mbps, at least twoFHSS access points are required. Even a 2 MbpsFHSS wireless LAN requires twice the numberof access points over DSSS because the coverageof FHSS for 2 Mbps is about half that of DSSS at2 Mbps. DSSS systems typically support lower-cost wireless repeating with one radio; FHSSsystems typically require two radio access pointsto support repeating to reduce overhead anddelay latencies with one radio.

Wireless LAN StandardsSeveral current and emerging standards are im-portant to understand when considering wirelessLAN technology. Table 8 summarizes the keystandards and their scope. Figure 9 shows therelative state of each of the standards. For moreinformation on these standards, visit Intermec’sweb site at http://www.intermec.com.

COMPARISON OF CELL CAPACITY

USING MULTIPLE APs

3 APs = 6 Mpbs

DSSS FHSSFHSS

8 APs = 6 Mpbs 16 APs = 8 Mpbs

WIRELESS LAN STANDARD UNIVERSE

INTEROPERABILITY

METRICS AGREEDTEST LAB ESTABLISHED

PUBLISHED STANDARDSTANDARD-BODY FORMED

HiperLAN 1

802.11 5 GHz

802.11 HS

802.11 FH

802.11 DS

OpenAir

HomeRF

Bluetooth


Wireless Experience

The installation of WLAN systems is sometimesmore of an art than a science. The coverage pat-terns of WLAN radios inside buildings are affectedby walls, ceilings, racks, and merchandise—eventhe composition of the building’s construction.Installation must consider the multitude of an-tenna options including omnidirectional, flatpanel, directional, and yagi antennas. Splitters,couplers, and lightning arrestors are also com-monly used in WLAN installations.

Working with a vendor experienced in install-ing WLAN systems in comparable facilities canprovide a less costly, trouble-free installation. Anexperienced WLAN solution provider can com-plete an RF site survey, provide a detailed instal-lation plan, and complete the installation toprovide full wireless coverage where it is needed.

Full System and Solution Provider

Wireless LAN systems can become very complexas they grow with organizations. The system in-frastructure includes access points, PC Cards, ISAcards, wireless client devices, and WLAN enabledsoftware. While it is possible to purchase theseproducts from many companies, few are truly fullsystem and solution vendors. By working with afull system and solution provider, customers canselect and purchase most system componentsfrom a single vendor, including installation andwireless client devices. In the future, a singlevendor will protect mission-critical applicationsby providing a single point of contact for resolv-ing system problems.

Considerations for Selecting aWireless LAN SolutionThe choice of radio technology may be lessimportant than the wireless networking software,which can also have a substantial impact onsystem performance and throughput. In additionto these technical factors, business factors alsoshould be considered when selecting a WLANvendor (see Table 9).

Not all vendors in the industry today are ableto support all of the capabilities described in thisguide. To properly evaluate a WLAN vendor, it isimportant to make a weighted list of require-ments, including current and anticipated futureneeds. Matching these requirements against theofferings of each WLAN vendor will allow you toshorten the list of prospective WLAN solutionsconsiderably. It is possible that no single vendor’sofferings will match all of your current and futurerequirements. In this case, discuss future productplans with vendors to determine which offers thedevelopment and migration plans closest to yourneeds.

Business ConsiderationsCost

Calculating the total cost of a WLAN system in-volves several elements, including client devices,access points, and ongoing maintenance. The costof access points can vary depending on the rangeand throughput of the selected technology. Sup-port costs include equipment service, problemdiagnosis, and software upgrades. If a customerhas installed WLAN systems in multiple locations,the ability to remotely access those systems andupgrade the access point and client devices canoffer substantial savings for support costs.

Another cost consideration may be whether atechnology migration path will re-use the custom-ers existing equipment. As new capabilities suchas faster data rates are offered by the system ven-dor, they should be backward compatible witholder technologies. Other cost factors includeproduct quality, reliability, ease-of-use, and avail-ability. All of these factors must be compared todetermine the true cost of competitive productofferings.

Table 9. Business Factors for Selecting a WLAN Vendor

Factor Key Considerations

Cost Total system cost: equipment, support, futureupgrades

Wireless Experience Vendor experience in installing completeWLAN systems

Full Provider Vendor provides full system, installation, andsupport solution

Business Stability Company strength and commitment towireless market

Wireless Clients Wide selection of client devices

System Integration Software and support to integrate devices intoa complete system

Service and Support On-site service options

Global Presence Country approvals and local support programs


Business Stability of theWireless LAN Vendor

Selection of a WLAN vendor should consider thevendor’s strength for supporting future expansionand new capabilities in the system. The risks ofselecting a vendor that will not be around in afew years is significant. Many WLAN vendors aresmall, start-up companies without the criticalcustomer base that will sustain the continuedinvestment required to survive. The industry hasalready seen a number of pioneers retrench andbecome very specialized niche players, or go outof business entirely.

Even large companies with substantial finan-cial and technical resources may exit the businesswhen the WLAN segment fails to reach thecompany’s internal expectations. A good exampleis provided by Motorola, one of the WLAN indus-try pioneers, which withdrew from the businessin 1995.

Selecting a vendor that may not be around inthe future makes it likely that long-term systemcosts will increase. The best way to evaluate thestability of a vendor, large or small, is to assessthe company’s success in the WLAN market. Acompany with a substantial WLAN market shareand a long roster of major customers is morelikely to thrive and be a reliable supplier. Anothercriterion is whether WLAN products are a keybusiness segment for the vendor.

Wide Selection of Wireless Clients

No single client device meets the requirements ofall WLAN applications in use today. While PC andISA adapter cards can be installed standalone incomputing devices, most customers demandclient devices with integrated radios. Integrationprovide secure mounting of the radio for every-day use, tuned antennas for the wireless client,battery and power management, and softwaredriver support.

A vendor that provides a wide selection ofwireless client devices enables customers to selectthe most appropriate device for each application.WLAN client devices include hand-held, station-ary, vehicle mount, and pen-based terminals,wireless modems, and PC/ISA adapter cards.

System Integration

Wireless LAN systems include much more thanAPs and client devices. A complete system in-cludes software and services that integrate clientdevices with the host and the supporting softwarerequired for the application.

A vendor that offers system integration ser-vices enables successful installation of a WLANapplication. In turn, this application gives users atrouble-free solution that provides immediatebenefits from the use of wireless technologies.The installation should include the hardware andsoftware integration necessary to get the applica-tion running quickly.

Service and Support

Once a WLAN system is installed and operational,service and support become critical factors forthe continued success of the system. Changes insystem requirements, the physical environment,applications, and system components are besthandled by a vendor that provides on-site serviceand support.

Global Presence

Check with the vendor to ensure that equipmentis approved for use in all countries where aWLAN solution will be required today or in thefuture. In addition, verify that the vendors sup-port and service programs in each country areadequate for the needs of the local installations.

“WLAN selection should be based on

end-user bandwidth requirements and

system scalability. Who supplies the

solution is based upon assessments

of standards compatibility, integration

and manageability”

Gartner Group, 1998


Technical ConsiderationsThe technical considerations for selecting a WLANproduct should not be based on a theoreticalargument between one technology or another.Instead, the decision should be based on howthe product meets business needs for capabilities,features, and performance (see Table 10). Be-cause each customer’s needs will differ, the fac-tors discussed in this section should be weighedin their importance to these needs.

Seamless Integration into the CorporateNetwork

A critical aspect of a WLAN system is seamlessintegration into the corporate network. WLANsare not a replacement for, but instead are an ex-tension of the wired LAN. The WLAN shouldseamlessly integrate into the wired networkwhether based on Ethernet or Token Ring.

As the network topology changes, the WLANsystem should support new networking require-ments. The WLAN should also support a varietyof topologies from wired access points, wirelessaccess points (repeaters), and wireless bridging tooffer flexibility for implementation regardless ofthe physical requirements of the facility.

A WLAN system should support roamingacross the enterprise, regardless of where accesspoints are physically attached to the networkinfrastructure. When a wireless client user roamsfrom an access point attached to one subnet onthe network to an access point attached to an-other subnet, the WLAN system should allowseamless communications for the client device.The system should not produce a lost connectionor worse, a lost connection plus re-initializationof the router or intelligent bridge. By selecting aWLAN system that has built-in support for roam-ing across subnets, wireless applications workseamlessly wherever users roam in the facility.

Cost and Coverage

A number of factors will effect the range of aWLAN device, including receiver sensitivity, trans-mit power output, multipath immunity, and an-tenna system performance (including the properuse of antenna diversity). The greater the rangeof WLAN devices, the fewer number of accesspoints that will be required to cover a givenbuilding or installation. Device range may ulti-mately become the key factor in determining totalsystem cost.

Performance (Throughput)

WLAN products typically specify the “over-the-air”data rates provided (i.e., 1 or 2 Mbps). However,what matters most to the user is the actual through-put of the system in a specific application and envi-ronment. Performance tests can determine actualthroughput rates in differing conditions. Among thevariables to consider in a throughput test are therange of the device from the access point, the sys-tem load (number and data traffic of clients usingan access point), the typical packet size on the net-work, and the Network Operating System (NOS).Additionally, the networking software used in eachimplementation—including how that system sup-ports roaming, the use of dynamic load balancing,and a number of other factors—will affect the per-formance of that system. Each WLAN product willprovide substantially different results that mayhave little correlation with the over-the-air datarates specified by the product vendor.

Response Time and Delay

Another consideration for determining system per-formance is the response time of a wireless clienttransaction. Response time includes host and net-work delay when delivering individual packetsfor a given system.

Again, the wireless networking software willhave the most substantial impact on this perfor-mance attribute. Software factors which determinethis impact include the technique used to supportroaming, use of dynamic load balancing, and theaccess point forwarding of buffered packets duringroaming. Also important is the reliability of theWLAN device transmission at various ranges, whichdetermines the number of packet errors and retrans-mission required. Different WLAN products mayhave wide variations in their delay performance.

Table 10. Technical Factors for Selecting a WLAN Solution


Seamless Integration Integration with wired LANs; roaming support

Cost and Coverage Device range for total system cost

Performance Data rates in the target environment

Response Time Delay-management techniques in the WLAN software

Size and Convenience Use and placement of access points and client devices

Interfaces Availability of hardware and software options

Interoperability Communication with other WLAN systems andclient devices

Power Management Minimized battery changes for client devices

Security Encryption of data transmissions


Size and Convenience

The attributes of size and convenience are closelyrelated for determining user satisfaction with awireless system. Small access points that can bemounted in or on ceilings, attached to walls, andplaced on desks or cubicle walls are much moreconvenient to implement than access points withthe form factor of a desktop PC.

For client devices, a single-piece, PCMCIAType II card form factor will usually be moreconvenient than a PCMCIA interface card with aseparate, cable-attached radio. Additionally, forspecialized hand-held terminals or Personal Digi-tal Assistants (PDAs), a built-in WLAN device willusually be better than using a PCMCIA slot withan external wireless device.

With a true PCMCIA form factor, the potentialavailability of specialized hand-helds and otherwireless devices will be greatly increased. It islikely that once all WLAN client devices reach atrue PCMCIA Type II form factor and all accesspoints are small, consideration of equipment sizewill become less important for choosing a systemvendor.

Availability of Hardware and SoftwareInterfaces

A number of different hardware or software op-tions may or may not be supported by a WLANsystem. The importance of these options dependon a user’s short- and long-term requirements.Tables 11 and 12 describe the most importantoptions.

Interoperability

Until a few years ago, interoperability amongWLAN systems was not possible. A particularWLAN system could communicate only with theclient devices offered by the same vendor. Withthe introduction of the WLI Forum 2.4 GHzOpenAir Specification in 1995, customers gainedthe ability to purchase WLAN systems and clientdevices from a variety of vendors. In the future,the IEEE 802.11, Bluetooth, and HomeRFstandards and specifications will further inter-operability. For more information or these stan-dards, visit Intermec’s web site atwww.Intermec.com.

WLAN systems that support interoperabilitygive customers the freedom to choose equipmentfrom a variety of vendors. Interoperability in-creases competition, a result that historically hasyielded lower costs, increased features, and newproduct selections.

Table 11. Access Point Options


Topologies Supported Access Point, Wireless Access Point (Repeater),Wireless Bridge

Networks Supported Ethernet, Token Ring

Connections 10 BaseT, 10Base2, AUI

Wireless Technologies 900 MHz , 2.4 GHz OpenAir, IEEE 802.11Supported Frequency Hopping, IEEE 802.11 Direct Sequence,

future high-speed wireless technologies

Table 12. Access Point Capabilities


Basic Basic support for required IEEE 802.11 protocols

Access point filtering of packets (multicast, broadcast,etc.)

Access point filtering of traffic to wireless devices notassociated with an access point

Advanced Roaming across subnet boundaries

Forwarding of buffered packets between accesspoints when roaming

Dynamic load balancing of client devicesbetween access points

Fault-tolerant setup possible

Capability for self-configuration and firmwareupgrades via BOOTP does not support firmwareupgrades by itself

Remote diagnostics, configuration, software upgradesand management via Telnet, FTP and/or SNMP

WEP (Wired Equivalent Privacy) encryption support

Support for the optional IEEE 802.11 specified PCF(Point Coordination Function), which enables real-time multimedia

Environmental Heating, cooling, sealingConsiderations

Client Device PCMCIA card and socket services, ISA Cards,Connections RS232, 10BaseT, 10Base2, AUI, RS422, Parallel port

Client Device/ Drivers: NDIS2, NDIS3, NDIS4, ODI,Capabilities

Operating Systems: DOS, Windows,Windows 95, Windows NT, OS 2, MAC, Unix

Advanced: Advanced packet power management,serial communications support, software upgradablevia flash memory


Customers may assume that when a standardis in place and interoperability is supported, prod-ucts from different vendors will work and per-form identically. However, even with standards-compliant products, substantial performancedifferences may exist between products offeredby different vendors. The reason for such varia-tions is typically that although the communica-tions protocol is specified by the standard, thefunctionality of access points and client devicesis determined by each vendor.

Power Management

Most WLAN client devices are battery-operated,with a limited battery life. The use of radios forcommunications can significantly affect batterylife. Most users would not be satisfied if they hadto change batteries frequently. Wireless clientdevices should offer advanced power manage-ment support to maximize battery life and mini-mize battery changes (optimally once per workshift).

Security Considerations

Security has always been a concern for wirelesscommunications, as evidenced by the issuesaround interception of cellular telephone trans-missions. Radios utilizing a broadcast-modetransmission scheme allow the possibility ofinterception by unintended receivers.

Much of today’s technology for spread spec-trum radio was developed with exactly this prob-lem in mind. The unique spreading patterns inDSSS transmissions were meant to be difficult todecode for a receiver that didn’t know the spe-cific pattern. Similarly, the pseudo-random hop-

ping patterns of the frequency hopping techniquewere designed to avoid casual decoding. Spreadspectrum radio technologies offer a great deal ofprotection because of these techniques. However,because interoperable WLAN solutions use thesame spread spectrum patterns, this security pro-tection is diminished.

If a customer requires more security, the IEEE802.11 Wireless LAN standard specifies use ofWEP (Wired Equivalent Privacy) encryption. Thisspecification utilizes the RSA Data Security, Inc.RC4 encryption algorithm to encrypt over-the-airdata transmissions. Encryption operates on top ofthe security provided by spread spectrum tech-niques. With WEP encryption, a users wirelesstransmission is meant to be as secure as an en-crypted transmission over a wired LAN.

An important consideration is that the IEEE802.11 standard secures only over-the-air trans-missions. An access point will send informationover the Ethernet or Token Ring network withoutencryption. For higher-level security require-ments, customers can use an end-to-end encryp-tion technique such as that specified by the IEEE802.10 standard. With end-to-end encryption lay-ered on top of the security measures in the wire-less system, user data should be totally secure.The choice of security should be based on indi-vidual application requirements, and consider thetrade-off of cost, performance, and complexity.


INDUSTRY’S LARGEST SELECTION OF END DEVICES

ETHERNET

DATACOLLECTION

SERVER

TOKEN RINGACCESS POINT

IBM

DUAL RADIOACCESS POINT

NTUNIX

RADIOINDEPENDENT™

NETWORKINDEPENDENT™

Future

Wireless

Standards

IEEE802.11DirectSequence

IEEE802.11FrequencyHopping

UHF

900

MHz

Spread

Spectrum

WLIF

PEN-BASED STATIONARYVEHICLE-MOUNTHAND-HELD

TOKEN RING

INCAIntermec’s Network Communications Architecture

Wireless LAN Solutions fromIntermec TechnologiesIntermec’s INCA (Integrated Network Communi-cations Architecture) is the industry’s leadingarchitecture for wireless LANs. Based on theprinciples of openness and flexibility, INCA givesbusinesses freedom of choice for meeting theirnetworking needs today and in the future. The

INCA architecture blends network connectivityand wireless LANs into a complete, plug-and-playsystem. It even allows roaming across routerboundaries and the integration of different radiofrequencies into a single-system solution(see Figure 10).

Figure 10.


The INCA Radio Independent™ feature givescustomers freedom of choice for radio technolo-gies. This design supports systems based on400 MHz UHF, 900 MHz spread spectrum, 2.4GHz OpenAir, IEEE 802.11 Direct Sequence, IEEE802.11 Frequency Hopping, and future wirelessradio technologies. The dual-radio feature enablescustomers to mix different types of wirelessradios to meet different range and throughputrequirements within a single environment.

The INCA Network Independent design sup-ports 10BaseT and 100BaseT Ethernet, TokenRing, Coax, Twinax, and SDLC networks. Wirelessnetworks built upon the INCA foundation arecompliant with industry-standard networkingprotocols such as SNA, TCP/IP, and SPX/IPX. TheApplication Independent design of the INCA ar-chitecture seamlessly supports a wide rangeof current and future business applications.

Systems based on the INCA architecture havethe ability to migrate seamlessly from today’ssolution to tomorrow’s technology, keeping pacewith the needs of the enterprise. This migrationstrategy enables customers to enjoy all the keyINCA advantages in the future, including freedomof choice. The INCA architecture enables busi-nesses to easily adopt new RF technologies,create new applications, and expand networkcoverage. This migration path also ensures pro-tection of current investments in wireless systemsand network designs.

Intermec and Wireless NetworkingIntermec is a full system and solution provider forWLANs. Intermec’s wireless networking productsare based on more than 30 years of industryleadership in data collection and wireless tech-nologies. Intermec Technologies Corporationdeveloped the first wireless data collection net-work and has more than 250,000 wireless and500,000 wired terminals installed to date. Otherachievements include the first spread spectrumRF data collection technology approved for saleby the FCC, the first 2.4 GHz data collection tech-nology, and the first multi-radio access point.Intermec equipment is certified and approvedby more enterprise resource planning (ERP) andwarehouse management system (WMS) providersthan the products of any other data collectionvendor.

To Learn MoreFor more information on the INCA architectureand Intermec wireless LAN solutions, contactIntermec Technologies Corporation at1-800-347-2636 or visit Interme’s web siteat http://www.intermec.com.

WhereInformationGets DownTo Business™

North America • 6001 36th Avenue West • P.O. Box 4280 • Everett, Washington 98203-9280 • 1 (800) 347-2636 tel • 1 (319) 369-3324 fax • Norand MobileSystems Division • 550 2nd Street S.E. • Cedar Rapids, Iowa 52401 • 1 (800) 452-2757 tel • 1(319) 369-3453 fax • Amtech Systems Division • 19111 DallasParkway, Suite 300 • Dallas, Texas 75287-3106 • 1 (800) 923-4824 toll-free • 1 (972) 733-6600 tel • 1 (972) 733-6699 fax

Europe/Middle East/Africa • Sovereign House • Vastern Road • Reading, Berkshire, RG1 8BT • United Kingdom • +44 118 987 9400 tel • +44 118 987 9401 fax

Asia Pacific/Latin America • 6001 36th Avenue West • P.O. Box 4280 • Everett, Washington 98203-9280 • 1 (800) 347-2636 tel • 1 (319) 369-3324 fax

Label Products and Supplies - North America • 1 (513) 874-5882 tel • 1 (513) 874-8487 fax • or 1 (800) 227-9947 tel • 1 (800) 227-1707 fax • LatinAmerica/Asia Pacific • 1 (513) 870-7930 Int’l phone • 1 (513) 874-3613 Int’l fax • Europe/Middle East/Africa +31 24 372 3100 tel • +31 24 378 0070 fax

World-Wide Fax Document Retrieval Service • 1 (650) 556-8447 tel • 1 (800) 755-5505 (North America Only)

Internet • www.intermec.com E-mail • [email protected]

Copyright © 1998 Intermec Technologies Corporation. All rights reserved. All trademarks are the property of their respective owners. Contents subject to change. Printed in the U.S.A. #608582 10/98

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