What is a Wireless LAN?(continue)

How WLANs WorkA wireless LAN (WLAN) is a flexible data communication system implemented as an extension to, or as an alternative for, a wired LAN within a building or campus. Using electromagnetic waves, WLANs transmit and receive data over the air, minimizing the need for wired connections. Thus, WLANs combine data connectivity with user mobility, and, through simplified configuration, enable movable LANs. Over the last seven years, WLANs have gained strong popularity in a number of vertical markets, including the health-care, retail, manufacturing, warehousing, and academic arenas. These industries have profited from the productivity gains of using hand-held terminals and notebook computers to transmit real-time information to centralized hosts for processing. Today WLANs are becoming more widely recognized as a general-purpose connectivity alternative for a broad range of business customers. The U.S. wireless Lan market is rapidly approaching $1 billion in revenues

WLANs and other Wireless TechnologiesWireless LANs use electromagnetic airwaves (radio and infrared) to communicate information from one point to another without relying on any physical connection. Radio waves are often referred to as radio carriers because they simply perform the function of delivering energy to a remote receiver. The data being transmitted is superimposed on the radio carrier so that it can be accurately extracted at the receiving end. This is generally referred to as modulation of the carrier by the information being transmitted. Once data is superimposed (modulated) onto the radio carrier, the radio signal occupies more than a single frequency, since the frequency or bit rate of the modulating information adds to the carrier.

Multiple radio carriers can exist in the same space at the same time without interfering with each other if the radio waves are transmitted on different radio frequencies. To extract data, a radio receiver tunes in (or selects) one radio frequency while rejecting all other radio signals on different frequencies.

In a typical WLAN configuration, a transmitter/receiver (transceiver) device, called an access point, connects to the wired network from a fixed location using standard Ethernet cable. At a minimum, the access point receives, buffers, and transmits data between the WLAN and the wired network infrastructure. A single access point can support a small group of users and can function within a range of less than one hundred to several hundred feet. The access point (or the antenna attached to the access point) is usually mounted high but may be mounted essentially anywhere that is practical as long as the desired radio coverage is obtained.

End users access the WLAN through wireless LAN adapters, which are implemented as PC cards in notebook computers, or use ISA or PCI adapters in desktop computers, or fully integrated devices within hand-held computers. WLAN adapters provide an interface between the client network operating system (NOS) and the airwaves (via an antenna). The nature of the wireless connection is transparent to the NOS.

Bluetooth technology is a forthcoming wireless personal area networking (WPAN) technology that has gained significant industry support and will coexist with most wireless LAN solutions. The Bluetooth specification is for a 1 Mbps, small form-factor, low-cost radio solution that can provide links between mobile phones, mobile

computers and other portable handheld devices and connectivity to the internet. This technology, embedded in a wide range of devices to enable simple, spontaneous wireless connectivity is a complement to wireless LANs — which are designed to provide continuous connectivity via standard wired LAN features and functionality.

What frequency's does this all use?

The 802.11b standard uses frequency's in the 2.4Gig, called the ISM band.

This is a no-licence required free to use frequency range, setaside for this this of thing.

Australia's radio spectrum changes allow free unlicensed use by any person in the ISM frequency bands.

Frequency band and EIRP (transmit power)915 MHz - 928 MHz Not exceeding 1 W2400 MHz - 2463 MHz Not exceeding 4 W2463 MHz - 2483.5 MHz Not exceeding 200 mW5725 MHz - 5875 MHz Not exceeding 1 W

The 2.4Gig channel's are as follows:

channel 1 = 2411Mhz centre freq.channel 2 = 2416Mhz centre freq.channel 3 = 2421Mhz centre freq.channel 4 = 2426Mhz centre freq.channel 5 = 2431Mhz centre freq.channel 6 = 2436Mhz centre freq.channel 7 = 2441Mhz centre freq.channel 8 = 2446Mhz centre freq.channel 9 = 2451Mhz centre freq.channel 10 = 2456Mhz centre freq.channel 11 = 2461Mhz centre freq.channel 12 = 2466Mhz centre freq.channel 13 = 2471Mhz centre freq.

channel 14 = 2484Mhz centre freq.

each channel needs 11Mhz either side of centre freq.Back to Top

How long of a distance can 802.11b wireless links go?

Withenough power the only limit is the curve of the earth. Unfortunately, there are laws governing power output. Personally I've seen a guy doing 17km links, some perth guys did 25km, and 33km are theoretically possible without any kind of power amplification. Granted, all of these links had very good line of site to each other.

Wireless NetworkingWireless networking technologies take the concept of "no new wires" one step further. In a wireless network, all of the computers in your home broadcast their information to one another using radio signals. This can make networking extremely easy, especially if you have computers all over your house. It also makes it a whole lot simpler to move computers around. For example, a laptop with a wireless network card is completely portable throughout the house!

In How Power-line Networking Works, we discussed peer-to-peer and client/server networks. In wireless networking, a peer-to-peer (or point-to-point) wireless network means that each computer can communicate directly with every other computer on the network. But some wireless networks are client/server. They have an access point, which is a wired controller that receives and transmits data to the wireless adapters installed in each computer.

There are four types of wireless networks, ranging from slow and inexpensive to fast and expensive:

Bluetooth IrDA HomeRF (SWAP) WECA (Wi-Fi)

Bluetooth is not widely available yet and is not expected to replace the need for high-speed data networks between computers. You can read more about this cutting-edge technology in How Bluetooth Short Range Radio Systems Works.

IrDA (Infrared Data Association) is a standard for devices to communicate using infrared light pulses. This is how remote controls operate, and the fact that all remotes use this standard allows a remote from one manufacturer to control a device from another manufacturer. Since IrDA devices use infrared light, they depend on being in direct line of sight with each other. Although you can purchase and install an IrDA-based network capable of transmitting data at speeds up to 4 megabits per second (Mbps), the requirement for line of sight means that you would need an access point in each room, limiting the usefulness of an IrDA network in a typical home layout.

Before we talk about SWAP and Wi-Fi, we need to understand the original standard that both of these new specifications are based on. The original Institute of Electrical and Electronics Engineers wireless-Ethernet specification, known as IEEE 802.11, designated two ways of communicating between devices and allowed for speeds up to 2 Mbps. Both communication methods, direct-sequence spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS), use the frequency-shift keying (FSK) technology we discussed in power-line networking. Also, both are based on spread-spectrum radio waves in the 2.4-gigahertz (GHz) range.

Spread spectrum simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range. Devices using direct-sequence spread spectrum (DSSS) communicate by splitting each byte of data into several parts and sending them concurrently on different frequencies. DSSS uses a lot of the available bandwidth, about 22 megahertz (MHz). Devices using frequency-hopping spread spectrum (FHSS) send a short burst of data, shift frequencies (hop) and then send another short burst. Since the FHSS devices that are communicating agree on which frequencies to hop to, and use each frequency for a brief period of time (less than 400 milliseconds) before moving on, several independent FHSS networks can exist in the same physical area without interfering with each other. Also, due to FCC restrictions, as well as the fact that FHSS devices generally send data on just two to four frequencies simultaneously, they only use 1 MHz or less of the available bandwidth. Because they use any given frequency for such a short time, FHSS devices are less prone to interference than DSSS devices. But DSSS is capable of much greater speed than FHSS since these devices can send a lot more data at the same time. Currently, FHSS-based devices are easier and cheaper to produce, which has led the HomeRF group to adopt FHSS as the method of communication for their products.

HomeRF and SWAPHomeRF (RF stands for radio frequency) is an alliance of businesses that have

developed a standard called Shared Wireless Access Protocol (SWAP). A sort of hybrid standard, SWAP includes six voice channels based on the Digital Enhanced Cordless Telecommunications (DECT) standard and the 802.11 wireless-Ethernet specification for data. SWAP devices make 50 hops per second and transmit at 1 Mbps. Depending on the manufacturer, some of these can step up to 2 Mbps if there is very little interference in their operational area.

Here are the advantages of SWAP:

It's inexpensive ($70 to $200 per device). It's easy to install. It requires no additional wires. It has no access point. It uses six full-duplex voice channels and one data channel. It allows up to 127 devices per network. It allows multiple networks in the same location. You can use encryption to make your data secure.

Here are the disadvantages of SWAP: It's not very fast (normally 1 Mbps). It has a limited range (75 to 125 ft / 23 to 38 m). It's not compatible with FHSS devices. Physical obstructions (walls, large metal objects) can interfere with

communication. It's difficult to integrate into existing wired networks.

This wireless PCI card is inserted inside your computer to build a wireless network.

The actual wireless transceiver, with a small, integrated antenna, is built into an ISA, PCI or PCMCIA card. If you have a laptop computer, the PCMCIA card plugs directly into one of the PCMCIA slots. For desktop computers, you will either need a dedicated ISA or PCI HomeRF card, or a PCMCIA card with a special adapter. ISA and PCI adapters are inserted inside the computer and have a slot that is accessible from the back of your computer so you can plug in the PCMCIA card. USB adapters are external devices that you plug the PCMCIA card into and then connect to a USB port on the computer. Some of the HomeRF

manufacturers sell kits that include the appropriate adapter along with the PCMCIA cards and installation software. Currently, because of the need to use dedicated cards, only computers can participate in a SWAP network. Printers and other peripheral devices need to be physically connected to a computer and shared as a resource by that computer.

In most cases, SWAP-based networks are point-to-point. Some manufacturers do offer access points as an option to increase the effective range of the wireless network, but they are not required equipment. Mainly because of this lack of an access point, HomeRF networks are significantly cheaper than the other viable wireless network, WECA's Wi-Fi. But the tradeoffs for cost are speed and distance. If you can set up a wired network using HomePNA or traditional Ethernet, you will get 10 to 100 times the speed for the same amount of money or less. However, unless you plan to send large amounts of data (like video) back and forth, SWAP speed is probably adequate for most home use, and the freedom of no wires can be quite appealing. Just remember that this is still a developing technology.

WECA and Wi-FiThe Wireless Ethernet Compatibility Alliance (WECA) has gone in a completely different direction from HomeRF. Targeted more at office use than home networks, Wi-Fi (for "wireless fidelity", like Hi-Fi for "high fidelity" in audio equipment) is essentially a seal of approval that says the manufacturer's product is compliant with a variation of the IEEE 802.11 specification known as IEEE 802.11b. This specification drops FHSS and focuses on DSSS because of the higher data rate it can attain. Under 802.11b, devices communicate at a speed of 11 Mbps whenever possible. If signal strength or interference is disrupting data, the devices will drop back to 5.5 Mbps, then 2 Mbps and finally down to 1 Mbps. Though it may occasionally slow down, this keeps the network stable and very reliable.

Photo courtesy NexlandThe ISB Wavebase by Nexland allows you to connect wireless

devices to your fast Internet connection.

Here are the advantages of Wi-Fi:

It's fast (11 Mbps). It's reliable.

It has a long range (1,000 ft / 305 m in open areas, 250 to 400 ft / 76 to 122 m in closed areas)

It's easily integrated into existing wired-Ethernet networks. It's compatible with original 802.11 DSSS devices.

Here are the disadvantages: It's expensive. It can be difficult to set up. Speed can fluctuate significantly.

Wi-Fi offers Ethernet speeds without the wires, but you pay for it. There are Wi-Fi compatible PC cards that operate in peer-to-peer mode, but Wi-Fi usually requires access points, which range in cost from about $300 to $1,400. Most access points have an integrated Ethernet controller to connect to an existing wired-Ethernet network. It also has an omni-directional antenna to receive the data transmitted by the wireless transceivers. Apple sells an inexpensive ($299 list) and easy-to-configure access point called Airport. Airport has to be connected to an Apple computer (iMac, PowerMac, iBook), but it will accept signals from any 802.11b-compatible wireless-network card, whether it's PC or Mac-based.

Like HomeRF systems, the majority of Wi-Fi wireless transceivers available are in PCMCIA card form. But some manufacturers do offer PCI or ISA format cards, not just adapters. The cost per card ranges from $99 to more than $300. Because these products are not targeted at the home market, they are not typically sold in "do-it-yourself" kits. Instead, everything is a la carte, allowing customers to build a system that exactly meets their needs.

This is the base unit of a wireless system used to connect workers with laptops.

At the HowStuffWorks offices, we have installed the 3Com Airconnect wireless system with great results. Several of our staff members now freely roam about the workplace with their laptops constantly connected to the network. We invested about $1,400 for the access point and three PCMCIA cards. That's not a bad investment to foster a dynamic work environment, but is certainly on the expensive side for most home networks.

If you are a Mac owner, setting up a Wi-Fi-compatible network is easy, and reasonable in terms of cost. Otherwise, this is an expensive undertaking that requires careful consideration of your needs. In fact, you can buy an inexpensive Apple computer and an Airport access point for close to the amount of money you would invest in most other access points currently available.

There are two other networking technologies that we will discuss: phone-line and power-line networks. Click on the title to go to one of these articles for more information, or proceed to A Word About Macs or The Future of Home Networking.

Benefits of WLANThe widespread strategic reliance on networking among competitive businesses and the meteoric growth of the Internet and online services are strong testimonies to the benefits of shared data and shared resources. With wireless LANs, users can access shared information without looking for a place to plug in, and network managers can set up or augment networks without installing or moving wires. Wireless LANs offer the following productivity, service, convenience, and cost advantages over traditional wired networks:

Range/CoverageThe distance over which RF waves can communicate is a function of product design (including transmitted power and receiver design) and the propagation path, especially in indoor environments. Interactions with typical building objects, including walls, metal, and even people, can affect how energy propagates, and thus what range and coverage a particular system achieves. Most wireless LAN systems use RF because radio waves can penetrate many indoor walls and surfaces. The range (or radius of coverage) for typical WLAN systems varies from under 100 feet to more than 500 feet. Coverage can be extended, and true freedom of mobility via roaming, provided through microcells.

ThroughputAs with wired LAN systems, actual throughput in wireless LANs is dependent upon the product and how it is configured. Factors that affect throughput include airwave congestion (number of users), propagation factors such as range and multipath, the type of WLAN system used, as well as the latency and bottlenecks on the wired portions of the WLAN. Typical data rates range from 1 to 11 Mbps.

Mulitpath EffectsAs Figure 9 shows, a radio signal can take multiple paths from a transmitter to a receiver, an attribute called multipath. Reflections of the signals can cause them to become stronger or weaker, which can affect data throughput. Affects of multipath depend on the number of reflective surfaces in the environment, the distance from the transmitter to the receiver, the product design and the radio technology.

Figure 9. Radio Signals Traveling over Multiple Paths

IntegrityWireless data technologies have been proven through more than fifty years of wireless application in both commercial and military systems. While radio interference can cause degradation in throughput, such interference is rare in the workplace. Robust designs of proven WLAN technology and the limited distance over which signals travel result in connections that are far more robust than cellular phone connections and provide data integrity performance equal to or better than wired networking.

Interoperability with Wired InfrastructureMost wireless LAN systems provide industry standard interconnection with wired systems including Ethernet (802.3) and Token Ring (802.5). Standards based interoperability makes the wireless portion of the network completely transparent to the rest of the network. Wireless LAN nodes are supported by network operating systems(NOS) in the same way any other LAN node via network device drivers. Once installed, the NOS treats the wireless nodes like any other component of the network.

Interoperability with Wireless InfrastructureThere are several types of interoperability that are possible between wireless LANs. This will depend both on technology choice and on the specific vendor's implementation. Products from different vendors employing the same technology and the same implementation typically allow for the interchange of adapters and access points. An eventual goal of the IEEE 802.11 specification, currently being drafted by a committee of WLAN vendors and users, is to allow compliant products to interoperate without explicit collaboration between vendors.

Interference and CoexistenceThe unlicensed nature of radio-based wireless LANs means that other products that transmit energy in the same frequency spectrum can potentially provide some measure of interference to a WLAN system. Micro-wave ovens are a potential concern, but most WLAN manufacturers design their products to account for microwave interference. Another concern is the co-location of multiple WLAN systems. While co-located WLANs from different vendors may interfere with each other, others coexist without interference. This issue is best addressed directly with the appropriate vendors.

Simplicity/Ease of UseUsers need very little new information to take advantage of wireless LANs. Because the wireless nature of a WLAN is transparent to a user&#acirc;s NOS, applications work the same as they do on tethered LANs. WLAN products incorporate a variety of

diagnostic tools to address issues associated with the wireless elements of the system; however, products are designed so that most users rarely need these tools. WLANs simplify many of the installation and configuration issues that plague network managers. Since only the access points of WLANs require cabling, network managers are freed from pulling cables for WLAN end users. Lack of cabling also makes moves, adds, and changes trivial operations on WLANs. Finally, the portable nature of WLANs lets network managers pre-configure and troubleshoot entire networks before installing them at remote locations. Once configured, WLANs can be moved from place to place with little or no modification.

SecurityBecause wireless technology has roots in military applications, security has long been a design criterion for wireless devices. Security provisions are typically built into wireless LANs, making them more secure than most wired LANs. It is extremely difficult for unintended receivers (eavesdroppers) to listen in on wireless LAN traffic. Complex encryption techniques make it impossible for all but the most sophisticated to gain unauthorized access to network traffic. In general, individual nodes must be security-enabled before they are allowed to participate in network traffic.

CostA wireless LAN implementation includes both infrastructure costs for the wireless access points and user costs for the wireless LAN adapters. Infrastructure costs depend primarily on the number of access points deployed; access points range in price from $800.00 to $2,000.00. The number of access points typically depends on the required coverage region and/or the number and types of users to be serviced. The coverage area is proportional to the square of the product range. Wireless LAN adapters are required for standard computer platforms, and range in price from $200.00 to $700.00. The cost of installing and maintaining a wireless LAN is generally lower than the cost of installing and maintaining a wired LAN for two reasons. First, a WLAN eliminates the direct costs of cabling and the labor associated with installing and repairing it. Second, because WLANs simplify moves, adds, and changes, they reduce the indirect costs of user downtime and administrative overhead.

ScalabilityWireless networks can be designed to be extremely simple or quite complex. Wireless networks can support large numbers of nodes and/or large physical areas by adding access points to boost or extend coverage.

Battery Life for Mobile PlatformsEnd-user wireless products are capable of being completely untethered, and run off the battery power from their host notebook or hand-held computer. WLAN vendors typically employ special design techniques to maximize the host computer&#acirc;s energy usage and battery life.

SafetyThe output power of wireless LAN systems is very low, much less than that of a hand-held cellular phone. Since radio waves fade rapidly over distance, very little exposure to RF energy is provided to those in the area of a wireless LAN system. Wireless LANs must meet stringent government and industry regulations for safety. No adverse health affects have ever been attributed to wireless LANs.

Benefits of WLANsThe widespread strategic reliance on networking among competitive businesses and the meteoric growth of the Internet and online services are strong testimonies to the

benefits of shared data and shared resources. With wireless LANs, users can access shared information without looking for a place to plug in, and network managers can set up or augment networks without installing or moving wires. Wireless LANs offer the following productivity, service, convenience, and cost advantages over traditional wired networks:

Mobility-Wireless LAN systems can provide LAN users with access to real-time information anywhere in their organization. This mobility supports productivity and service opportunities not possible with wired networks.

Installation Speed and Simplicity-Installing a wireless LAN system can be fast and easy and can eliminate the need to pull cable through walls and ceilings.

Installation Flexibility-Wireless technology allows the network to go where wire cannot go.

Reduced Cost-of-Ownership-While the initial investment required for wireless LAN hardware can be higher than the cost of wired LAN hardware, overall installation expenses and life-cycle costs can be significantly lower. Long-term cost benefits are greatest in dynamic environments requiring frequent moves, adds, and changes.

Scalability-Wireless LAN systems can be configured in a variety of topologies to meet the needs of specific applications and installations. Configurations are easily changed and range from peer-to-peer networks suitable for a small number of users to full infrastructure networks of thousands of users that allows roaming over a broad area.

Wireless LAN Technology OptionsManufacturers of wireless LANs have a range of technologies to choose from when designing a wireless LAN solution. Each technology comes with its own set of advantages and limitations.

Spread SpectrumMost wireless LAN systems use spread-spectrum technology, a wideband radio frequency technique developed by the military for use in reliable, secure, mission-critical communications systems. Spread-spectrum is designed to trade off bandwidth efficiency for reliability, integrity, and security. In other words, more bandwidth is consumed than in the case of narrowband transmission, but the tradeoff produces a signal that is, in effect, louder and thus easier to detect, provided that the receiver knows the parameters of the spread-spectrum signal being broadcast. If a receiver is not tuned to the right frequency, a spread-spectrum signal looks like background noise. There are two types of spread spectrum radio: frequency hopping and direct sequence.

Narrowband TechnologyA narrowband radio system transmits and receives user information on a specific radio frequency. Narrowband radio keeps the radio signal frequency as narrow as possible just to pass the information. Undesirable crosstalk between communications channels is avoided by carefully coordinating different users on different channel frequencies.

A private telephone line is much like a radio frequency. When each home in a neighborhood has its own private telephone line, people in one home cannot listen to calls made to other homes. In a radio system, privacy and noninterference are accomplished by the use of separate radio frequencies. The radio receiver filters out all radio signals except the ones on its designated frequency.

Frequency-Hopping Spread Spectrum TechnologyFrequency-hopping spread-spectrum (FHSS) uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical channel. To an unintended receiver, FHSS appears to be short-duration impulse noise.

Figure 7. Frequency Hopping Spread Spectrum

Direct-Sequence Spread Spectrum TechnologyDirect-sequence spread-spectrum (DSSS) generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The longer the chip, the greater the probability that the original data can be recovered (and, of course, the more bandwidth required). Even if one or more bits in the chip are damaged during transmission, statistical techniques embedded in the radio can recover the original data without the need for retransmission. To an unintended receiver, DSSS appears as low-power wideband noise and is rejected (ignored) by most narrowband receivers.

Infrared TechnologyInfrared (IR) systems use very high frequencies, just below visible light in the electromagnetic spectrum, to carry data. Like light, IR cannot penetrate opaque

objects; it is either directed (line-of-sight) or diffuse technology. Inexpensive directed systems provide very limited range (3 ft) and typically are used for PANs but occasionally are used in specific WLAN applications. High performance directed IR is impractical for mobile users and is therefore used only to implement fixed subnetworks. Diffuse (or reflective) IR WLAN systems do not require line-of-sight, but cells are limited to individual rooms.

WLAN Configurations

Independent WLANsThe simplest WLAN configuration is an independent (or peer-to-peer) WLAN that connects a set of PCs with wireless adapters. Any time two or more wireless adapters are within range of each other, they can set up an independent network (Figure 3). These on-demand networks typically require no administration or preconfiguration.

Figure 3. Independent WLAN

Access points can extend the range of independent WLANs by acting as a repeater (see Figure 4), effectively doubling the distance between wireless PCs.

Figure 4. Extended-Range Independent WLAN Using Access Point as Repeater

Infrastructure WLANsIn infrastructure WLANs, multiple access points link the WLAN to the wired network and allow users to efficiently share network resources. The access points not only

provide communication with the wired network but also mediate wireless network traffic in the immediate neighborhood. Multiple access points can provide wireless coverage for an entire building or campus.

Figure 5. Infrastructure WLAN

Microcells and RoamingWireless communication is limited by how far signals carry for given power output. WLANs use cells, called microcells, similar to the cellular telephone system to extend the range of wireless connectivity. At any point in time, a mobile PC equipped with a WLAN adapter is associated with a single access point and its microcell, or area of coverage. Individual microcells overlap to allow continuous communication within wired network. They handle low-power signals and &#atilde;hand off&#atilde; users as they roam through a given geographic area.

Figure 6. Handing off the WLAN Connection Between Access Points

Do Wireless LANs Pose a Health Risk to the Consumer?IntroductionInfluence on the health is one of most discussed topics of radio LANs, since radio devices emit radio frequency electromagnetic energy. This document wants to clarify that radio devices are not bad for the health of people using Wireless LANs (WLANs). Also a list of frequently asked questions will be presented.

Safe, Low-Power RadiWireless LAN (WLAN) devices emit radio frequency electromagnetic energy. Because WLANs are designed to operate within the guidelines found in radio frequency safety standards and recommendations, WLANs are safe for use by consumers. These standards and recommendations reflect the consensus of the scientific community and result from deliberations of panels and committees of scientists who continually review and interpret the extensive research literature.

Radio Frequency Safety StandardsThe following organizations have independently issued similar recommendations for exposure to radio frequency electromagnetic energy. &#aacute; Standards Coordinating Committee 28 of the Institute of Electrical and Electronics Engineers (IEEE) &#aacute; National Council on Radiation Protection and Measurements (NCRP) &#aacute; National Radiological Protection Boards (NRPB) in the United Kingdom. &#aacute; International Radiation Protection Association's International Non-Ionizing Radiation Committee (IRPA/INIRC) (under World Health Organization sponsorship)

IEEE/ANSI Standard (ANSI/IEEE C95.1-1992)In September of 1992, the IEEE Standard Board approved the IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, IEEE C95.1-1991. This standard is a revision of the American National Standard Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 100GHz, ANSI C95.1-1982. The IEEE standard resulted from the deliberations of over 120 leading biologists, biophysicists, physiologists, physicists, physicians, engineers and members of other scientific disciplines representing academia, federal agencies with public responsibilities, industry and other interested groups and organizations. In November of 1992, the American National Standards Institute (ANSI) approved the IEEE C95.1-1991 standard. The following is stated in the IEEE standard: " No verified reports exist of injury to human beings who have been exposed to electromagnetic fields within the limits of frequency and [specific absorption rate] specified by previous ANSI standards, including ANSI C95.1-1982."IEEE USAB Entity Position Statement "Measurements have shown that routine exposure of users and other persons to low power portable and mobile transceivers and cellular telephones do not induce rates of [radio frequency] absorption that exceed any of the maximum permissible rates of energy absorption defined by these guidelines" [IEEE, ANSI]. Therefore, based on present knowledge, the exposures from low-power transceiver are considered to be without risk for the users and the public. (Quoted from the IEEE USAB Entity Position Statement Human Exposure to Radio frequency Fields from Portable and Mobile Telephones and other Communication Devices, December 2, 1992.)

ConclusionThe interpretation of over four decades of research in this area has led to a scientific consensus on the safety of exposure to radio frequency electromagnetic fields. This

consensus is reflected in the recommendations and standards developed by expert committees such as NCRP Scientific Committee 53, IEEE Standards Coordinating Committee 28, IRPA/INIRC and NRPB. Manufacturers of Wireless Networking products design their products to operate within the guidelines of these standards and recommendations and, therefore, are considered safe.

Questions and Answers

Can you absolutely assure customers that Wireless LAN products are safe?Extensive research on the safety of exposure to radio frequency electromagnetic energy has been carried out for more than four decades. This research is continually reviewed and interpreted by committees of scientists who develop safe limits for exposure. Manufacturers of wireless LANs monitor this research and participate in the consensus standards process and ensure that WLAN products operate within the guidelines of these standards. Consequently, manufacturers of WLAN products believe their products are safe.

What if the network has 100 nodes?Only one transmitter is active at any point in time, so the radiated power of a total network even when it has 100 nodes is actually equivalent to the radiated power of a single transmitter. WLAN transmitters operate at a power of 0.035 Watts (35 mW) in the 2.4 GHz band depending on the specific product in use and the local regulations.

How does WLAN technology differ from cellular technology?WLAN products use a "bursty" type of transmit/receive protocol, while Cellular transmits and receives constantly (connection oriented). As an example: If a user would transfer data on an average of 100 MB per day, the WLAN transmitter would be on the air for approximately 10 minutes. Moreover, a typical hand held-cell phone has a RF power output of 0.600 Watts (600 mW) or almost 20X more output power!

The number of supported computers per access point varies with the business applications and other system factors.

To ensure optimal wireless performance, consider these questions:

WLAN Benefits

You're in business. You know that it takes more than luck to keep pace in today's market. And, you know the decisions you make every day show up right on your bottom line. You require flexibility, agility, responsiveness-in short, the ability to move more quickly than your competitors and meet the needs of your customers. We think wireless networking could be a natural fit. Here's why.

It's flexible. With a wireless network you and your staff can work anywhere, anytime within your network.

It's fast. Intel wireless technologies offer high performance and bandwidth to keep all your

essential applications and transactions running.

It's responsive. As you change your business operations, your wireless network can change with you.

It's customized. Your wireless network can be configured the way you want it-even combined with your current wired network.

And it's cost effective. Wireless networks can be implemented gradually. Just install what you need, when you need it.

Whether your company is thinking of a wireless solution to network an entire campus or a select group of high-productivity workers within a wired organization, WLAN installations offers companies a way to improve their business operations and increase revenues. You can connect 802.11a and 802.11b products to the same wired network backbone. Since the two standards use different frequencies, you can put their access points near each other without interference.

When it's Time to Consider WLAN for Your Business The information and resources available here can help you learn more about WLAN solutions for your company, if you are:

Retrofitting an existing network Adding or expanding a secondary network Adding, moving, or changing employees to

new locations Increasing mobility of part or all of your

workforce Enhancing network performance Expanding business operations Upgrading or expanding current wireless

hardware and/or software Investing in a cost-effective network

When it's Time to Consider 802.11a WLAN

You should consider an 802.11a WLAN with Intel® PRO/Wireless 5000 LAN products when:

The savings you gain through higher system performance is more important than initial system cost

You need the bandwidth and speed to handle large graphics, audio, data, and video files

You need greater network capacity than an 802.11b WLAN can give you

You want your WLAN to match the speed of wired networks

You will have many users per access point You want to replace your wired network with

a wireless one

When it's Time to Consider 802.11b WLAN You should consider an 802.11b WLAN with Intel® PRO/Wireless 2011b LAN products when:

Initial system cost is your main concern Data rates up to 11 Mbps are sufficient Your goal is global implementation You want to expand an existing 802.11b

WLAN You need WLAN access for handheld PCs You will have a small number of users per

access point

You want to add limited pockets of WLAN to your existing wired LAN

A traditional, wired local area network (LAN) sends packages of data from one piece of equipment to another across cables or wires. A wireless local area network (WLAN) relies instead upon radio waves to transfer data. These radio signals are transferred between access points installed at key locations in the physical environment (such as on walls or ceilings) and wireless adapters attached to computing systems. A WLAN eliminates cables and wires and takes advantage of the fact that radio

waves can pass through environmental obstacles, such as ceilings and walls. Wireless networks offer unprecedented flexibility for computer users, along with remote management capabilities for business owners or system administrators.There are two primary components of a wireless network design: infrastructure and client adapters. Intel wireless infrastructure products consist of gateways and access points, which serve as data conduits and, where needed, provide a bridge between wireless and existing wired networks. Gateways are typically used for smaller businesses, while access points serve medium and enterprise businesses. Client adapters provide the links between computers and the network, as well as converting data into a format that the network can use. The adapter selected depends on the type of device being used. Adapters include WLAN PC cards, PCI cards, USB devices, and modules. Another important consideration in a WLAN is the antenna. Antennas serve to direct the radio waves into the desired area in a specific coverage pattern. For each key component of a WLAN, the particular equipment chosen depends on a particular site-with its unique usage patterns and environmental factors.

Accessories

Full breadth of products: 802.11a and 802.11b solutions for your home office, small and medium business, or large organization.

High performance: Up to 54 Mbps throughput and advanced roaming capabilities provide reliable access to e-mail, the Internet, file sharing and other network resources away from the desk.

Manageable: Intel® PROSet software allows for simple configuration of your wireless network.

Easy setup: Expand your network quickly and easily by adding wireless access points and adapters. Installs in minutes. Ideal when wiring is difficult or cumbersome.

Safe and reliable: Security features encrypt data to help ensure privacy, while restricting network access to authorized users.

Wireless Ethernet AdaptersIntel® PRO/Wireless 5000 LAN CardBus Adapter and Starter KitIntel® PRO/Wireless 5000 LAN PCI Adapter

Wireless Ethernet Dual Access PointsIntel® PRO/Wireless 5000 LAN Dual Access Point

Wireless Ethernet Access Points and Starter KitsIntel® PRO/Wireless 5000 LAN Access Point and Starter Kit

Wireless Ethernet AdaptersXircom® CreditCard™ Wireless Ethernet AdapterIntel® PRO/Wireless 2011B LAN PC CardIntel® PRO/Wireless 2011B LAN USB DeviceIntel® PRO/Wireless 2011B LAN PCI Adapter

Wireless Ethernet Dual Access PointsIntel® PRO/Wireless 5000 LAN Dual Access Point

Wireless Ethernet Access PointsIntel® PRO/Wireless 2011B LAN Access Point

Xircom® Wireless Ethernet Access Point

Intel® Wireless GatewayIntel® Wireless Gateway (Wi-Fi*/802.11b)

Wireless Ethernet Starter KitsXircom® Wireless Ethernet Starter Kit

Wireless Modules for HandheldsXircom® Springport™ Wireless Ethernet ModuleXircom® Wireless LAN Module for Palm* Handhelds

Wireless LAN AntennasIntel® 2.4 GHz Directional Yagi AntennaIntel® 2.4 GHz Omni-Directional Indoor/Outdoor Antenna Intel® 2.4 GHz Low Profile Directional Antenna Intel® 2.4 GHz Omni-Directional Ceiling Mount Antenna Wireless LAN Power InjectorsIntel® PRO/Wireless 2000 LAN Power Injector

Tropicana Hotel & Casino, Atlantic City,New JerseyIntel® PRO/Wireless LAN ProductsOptimize Network Traffic Within the Casino

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Tropicana Atlantic spans about four city blocks in Atlantic City. Greg Dyer, the PC network manager for Tropicana, oversees the IT staff and network system of approximately 1,200 users.

"We have currently a combo of about 13 fiber optic closets throughout the property and 12 NT* servers, POS (point of sales) systems, and slot rating

"...the experience working on the Intel® Wireless network has given us excellent results: flexibility, no more cabling issues, and it's opened up a whole new creative solution for our special events group."

Greg DyerPC Network Manager,

systems. These slot rating systems show how long a customer has been playing the slot machines and also profiles the customers. We have IBM* AS400 servers that run the hotel purchasing, marketing, financials and sales systems. On the client side, we have over 800 networked PCs and appliances."

"My job is to evaluate new technologies that will help the hotel and casino streamline efficiency. I chose the Intel® Wireless networking solution because it is a solid performing product."

Wireless Convenience in the CasinoTropicana decided to go wireless in the casino because it offers an alternative to traditional wiring.

There are six Intel® PRO/Wireless LAN Access Points in different strategic locations throughout the building: in the atrium, casino, reception and theatre areas. These areas represent the six special event locations. The casino marketing staff uses Intel® PRO/Wireless LAN PC cards in their laptops and utilizes the wireless LAN for marketing activities, special events and promos.

Just prior to implementing the wireless LAN, the marketing department was having an event in a room that they had spent time and money wiring a computer network. The Fire Department came in and shut down the event because the wires violated building code. Now, with wireless network, the hotel and casino promoters can set up an event, and even move it from one area of the hotel/casino to another

if a greater number of people arrive.

"We move around so much with special events and promotional giveaways. Although Tropicana is the biggest hotel in New Jersey, it's difficult to find areas to hold special events. If you are a customer who meets a certain profile, you'll receive certain prizes. We give away anything from t-shirts to fine china."

"Every time we've had an event within the hotel, we've had to cable or network that area of the hotel

Tropicana Hotels & Casinos

—whether it's on the casino floor, in the lounge, in the pool deck area. We don't want to pull people into a back hallway to give them their prize. Some of the large convention areas are sometimes the only areas available, but it's not necessarily the best area to hold these events. We want our customers to feel at ease, so now that we have the Intel® PRO/Wireless LAN network, we are not limited to a particular room. The staff uses their wireless networking laptops and they can easily monitor the prize giveaways and marketing event from their networked laptop."

"Sometimes we use the wireless network like a registration desk. At bingo, for example, the hotel staff uses their wireless networked laptops to register the clients."

Intel or Bust!Tropicana chose Intel® Wireless networking products to deploy throughout its hotel and casino.

Mr. Dyer states "there is a reliable name (Intel) behind the architecture. We had looked at a couple other brands that we felt weren't as strong, but we felt comfortable with the Intel® brand name. So far, the experience working on the Intel Wireless network has given us excellent results: flexibility, no more cabling issues, and it's opened up a whole new creative solution for our special events group. And, we can move wherever the fire department wants us to hold the event!"

Gambling on Wirele$$"We are considering opening up our conventions department to host computer/tech events where we can lease out wireless Internet access for our clients if they want to hold seminars or tradeshows," explains Mr. Dyer. "We are also exploring point-to-point bridging opportunities to link multiple hotel towers, thus keeping T-1 leased line costs down."

"We are also considering running Intel® PRO/Wireless LAN products on handhelds or PDAs on the casino floor. We'd like to be able to rate

players right at the tables instead of running back and forth to the casino pits."

Betting on the Future with Intel PRO/WirelessTropicana chose to implement a wireless solution because it offers them more flexibility. "We wanted to get our feet wet, and test wireless LANs. The next step is wireless point of sale systems and remote cashier stations in the parking lots or beach areas," says Mr. Dyer.

Intel® PRO/Wireless LAN products allow Tropicana to creatively manage their special events, stay in line with fire code, and offer new ways to monitor their casino floor.

High Tech High School, San Diego, CaliforniaMagnet Technology High School uses Intel® Wireless Products to Educate Students

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High Tech High is a public high school, founded in 2000. The school currently has approximately 200 students. The core curriculum focuses on science, math and technology.

Peter Estacio is Director of Information Technology at HTH, where approximately half of the teaching staff are using Intel® PRO/Wireless LAN products. "Our courses and classrooms are mobile."

High Tech Goes Wireless:Old Building Meets New TechnologyThe HTH building is very old. Mr. Estacio explains, "HTH is on the naval training center, which was built about 50 or 60 years ago. The building wasn't set up for a wired network. There were a lot of structural impediments that kept us from wiring every classroom. We did some great work to retrofit the building, but it's not ideal. Some areas, such as the labs, still need a network—that's why we installed a wireless LAN."

Intel helped HTH perform a site survey, a method to help determine where to install Access Points. Three Intel® PRO/Wireless LAN Access Points were

deployed throughout the building to ensure full coverage. Teachers utilize the wireless network as they roam from the teacher lounge to the classroom. Some students use the wireless network to access the Internet or transfer files.

Working Around Bunsen BurnersThe biotech lab at HTH has square tables where students perform lab experiments. The set-up of the lab makes it difficult to install computers: there are butane tanks, Bunsen burners and other flammable equipment that interferes with large, desktop computers.

Laptop computers, configured with Intel® PRO/Wireless LAN PC cards, allow the students to be more mobile as they move from one area of the lab to another. And, it allows the teacher to visit each table with his/her laptop to record the experiment.

Using Wireless networks to Build Yo-Yos"We have a few hands-on labs such as a biotech lab and the engineering manufacturing lab," explains Mr. Estacio. "Due to large equipment in the manufacturing lab (i.e. woodworking equipment), space is wasted by desktop computers. We are now switching to laptop computers so students can use server-based CAD/CAM (computer aided design/computer aided manufacturing) design techniques in this lab."

"For example, in the past, if a student designed a yo-yo, they would design it on the computer in a classroom and then go to the manufacturing lab with a printout of their design. Now, with their wireless-enabled laptops, they can take their laptops directly to the manufacturing area."

"They access the data over the network and use the Internet to tweak their design. We are teaching them to be proficient and efficient mechanical engineers."

Looking Through the Crystal Ball: The Future of Wireless at HTHHTH hopes to keep its students ahead of the technology curve. Mr. Estacio will soon begin teaching students the benefits of wireless networking. He will use Intel® PRO/Wireless LAN equipment and material from Intel's course Designing Flexible Wireless LAN Solutions to give the high school students exposure to wireless networking. The students will learn how to perform site surveys, and they will receive extensive hands-on experience in wireless LAN design, implementation, and management. Students who complete his course will have a solid understanding of the latest wireless networking technology, and will be well on their way towards a career in high tech, thanks to High Tech High.

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Summary:Sitting at their desks in an isolated and geographically dispersed community in central Oklahoma, students in the Wanette Public School District can go everywhere. Using an Intel® PRO/Wireless LAN to turn every classroom into a virtual, combined library-laboratory, the district enables teachers and students to experience a world-class education not otherwise possible in this rural farming community. Access to the Internet, for example, adds millions of virtual books and periodicals to the school’s small library. The district’s 802.11b Intel® PRO/Wireless LAN allowed school administrators to make quick and easy modifications to the learning environment without the need for costly building improvements or new classrooms. Examining the network in the Wanette Public School District in closer detail, this case study shows how wireless technology equalizes educational opportunities for students in a rural environment.

Profiled Organization:Wanette School District, Wanette Oklahoma, USA

The Challenge: Provide students and teachers in a small, rural school district with increased access to advanced, up-to-date resources, information and curriculum materials, without the need for costly building improvements or new construction.

The Solution: Add wireless networking technology to the existing wired network to optimize information access for the entire student population. The Wanette Public School District installed an Intel® PRO/Wireless LAN featuring 12 Intel® PRO/Wireless 2011 LAN Access Points and laptop PCs equipped with 32 Intel® PRO/Wireless 2011 Adapters. The district also has 250 networked PCs running Intel® Pentium® II, Pentium® III and Pentium® 4 processors located throughout the classrooms and the schools’ two dedicated computer labs.

Benefits: The addition of the wireless LAN has cost-effectively extended the availability of the district’s network to all teachers and students throughout the district’s two school buildings. Enhanced student and teacher productivity has been realized through increased access to educational material, integrated curriculum opportunities and anytime-anywhere networking experiences.

Indian Scenario:

Govt has deregularised the use of WLAN for indoor use recently (November 2002). ie. Licence for wlan use within indoors is not required.Present market of WLAN is 200 crores.Expected to go to 600 crores.One access point costes about 50,000/- Rs. Each client costs aprox. 10,000/- ie for 10 users the cost of Wlan setup can be 1.5 laks now.But rates may fall in near future.Expected speeds of WLAN to go up to 54mbps in next few months.