WIRELESS LAN

What is a Wireless LAN?

A wireless LAN is actually an extension of a LAN or even a WAN. At some point the information traveling through a WLAN is tied to a network that is wired. So a wireless network must be seen as an extension of some network that is wired. Wired networks have emerged into education because of their potential for becoming learning resources. As educational institutions install LANs, vendors provide information about the range of options that are available for consuming the products generated by the computer communication age. Or to quote a bit from Byte: "The wireless LAN marketplace is heating up." (May 1994)

From the educator's point of view, the wireless LAN explosion seems logical given the amount of LANs that are planned for Hawaii. (And supposedly by the year 2000, 10% of all LANs will be wireless.) However, the effect of information begins to form concepts of doubt concerning the desirability of wireless LANs. The doubt arises because the information about wireless LANs describes "wireless technology [as] a natural fit for today's horizontal corporations and mobile workforce." (Byte (May 1994:99)

Contrary to the new educational discourse concerning the flattening out of vertical administrative structures, and contrary to budgetary "mandates" which have flatlined a few wasteful spikes of sloth and favors (therefore rendering a hatcheted Republican vision in Democratic Party allegiance,) there is nothing horizontal about public education. And recurring murmurs about charging teachers parking fees for parking spaces at their schools of employment indicate that mobility is not planned for the teaching workforce. Educators are to commute and remain stationary in their classrooms where accountability is documented. So with horizontal and mobility factors aside, and suspending judgment on whether or not institutions of education are structured and operate as corporations do, what advantages do wireless LANs offer to educators?

There appears to be two answers to the question of wireless LAN advantages. By exercising our imaginations we can envision that there are some practical advantages for wireless connections at schools. And by researching the subject of wireless LANs, there is noticed an heuristic advantage of discussing wireless LANs.

The practical aspects of wireless LANs in elementary, intermediate and high school begin with issues of well being such as medical assistance from the health aide; enhanced security and communication in remote and portable areas of campus; the latest vegetable prices for the cafeteria manager; and potential hands-on projects for learners who are interested in understanding "remote" connections among people and commodities. And on the level of administration: access to students' records directly from athletic fields to determine eligibility; and while shielded by the privacy of a personal laptop computer, instantaneous administrative reports of successfully (or unsuccessfully) meeting stated outcomes .

More interesting than the practical uses of wireless connections are the heuristic aspects of remote connections. These heuristic aspects of researching wireless LANs are sociological and scientific. The sociological aspects of wireless LANs are discovered in "[t]he purpose of a standard 'to ensure that any wireless LAN equipment you purchase will be interoperable.'" (Byte May 1994:99) The scientific aspects of researching wireless LANs are discovered in the attempt to understand a wireless connection.

As a sociological phenomenon, wireless LANs reveal where wired connections have taken us: around the world. Since worldwide connections wire one corporation to and into another corporation, the connections require that each company have some common features in their hardware manufacturing and operation because they will in turn use their own hardware to connect themselves to somebody else's hardware. If the globally scaled connectivity giants didn't share more commonalties than differences, there would be no worldwide connection. (Now I know that you are thinking of how many commonalties there are in the DOE, and yet, as an institution locally connected it behaves as though neither head nor body were attached by even the tinniest conductor of an electron volt, a single brain cell. Therefore, why should we attempt to make more conduits for mindless connections? I can only ask us to remember what Dr. P.B. said: If teachers are wired--if we become connected--then the institution that devours our young will wither away. If teachers become an electronic entity, we will generate a force stronger than the mindless packets of budgetary directives and success compacts that are generated within the victorious sighs of newly elected governors.)

Just as the wired world has an authority of setting standards, so too does the wireless world. In fact, the "worldwide authority on standardization in wireless LANs" is the same for wired LANs: the Institute of Electrical and Electronic Engineers (IEEE). The wireless group for the IEEE is called "the Wireless Local-Area Networks Standard Working Group, IEEE Project 802.11. Since 1990, the Project 802.11 Committee has worked to establish a universal standard for the wireless marketplace." (Byte May 1994:99) The universal standard the committee selected was a "protocol proposal from AT&T Global Information Solutions/NCR Microelectronic Products Division's Wireless Communications and Networking Division, Symbol Technologies, and Xircom." (T3ers will rejoice to read that the universal standard for wireless connections--DFWMAC (distributed foundation wireless media access control)--contains CSMA/CA [carrier sense multiple access with collision avoidance], a function that appears similar to Ethernet's CSMA/CD [carrier sense multiple access with collision detection]. The similarity in the mechanisms that control information collisions through detection and avoidance indicate that wired and wireless networks share more similarities than differences.) With the Time-Warner buy out of Turner Broadcasting, the picture of the connectivity giants grows larger as unconnected surfaces of the planet grow smaller. And that is one of the main points this research into wireless LANs has exposed: the entire planet is wired; wireless connections are extensions of planetary connection, and the corporations doing the connecting are decreasing in number. As the IEEE continues to set standards for global enterprises, the actors in the global enterprise of communication are becoming fewer in number. Global communication must be making the world smaller because fewer agents are needed to run global communication. Never before (that we know of) have so many people been able to reach out and touch one another.

Although the image of billions of people chatting to one another "24/7" is indeed overwhelming to the imagination, the physical difference between a wired and wireless LAN contains heuristic lessons that are overwhelming too. This physical difference between wired and wireless emerges as a question? In a wireless LAN, what takes the place of a wire? Because I do not fully comprehend the electronic process of sending "bits instead of atoms" over or through a wire, the invisible connection that sends invisible bits seems all the more mysterious.

"There are several methods of establishing wireless links between two points, only two are capable of supporting the high-speed data transmission necessary" for WLANs. These two methods are called radio frequency transmission and infrared transmission. (Within the radio frequency or RF method is included the microwave frequency.) Radio frequency and infrared refer to energy wave lengths within the electromagnetic spectrum. The electromagnetic spectrum is the known range of wavelengths emitted by matter.

Here is a diagram showing the range of wavelengths. Radio waves are the largest wavelengths, measured in centimeters, gamma rays are the smallest wavelengths, measured in hundredths of nanometers. (There are wavelengths longer than radio waves--power and telephone waves--but they wouldn't fit within the ELMO dimensions. They are measured in megameters.) Wireless LAN wavelengths fall on the side of visible light that are in the longer wavelengths.

"The two most popular transmission modes for wireless local networks are spread-spectrum radio transmission and infrared transmission." Spread-spectrum radio transmission requires that three important problems be solved: frequency allocation, interferences, and security.

    1) Frequency allocation for RF WLANs presents a problem because "high speed data communication is a newcomer to the radio frequency spectrum market, so it has to use spectra that other, older applications are not using." (A. Santamaria and F.J. Lopez-Hernandaz, editors, "Wireless LANs: An Overview," Wireless Lan Systems [Boston: Artech House, 1994], 2-3.) Most spread-spectrum transmissions are in the frequency range set aside by the FCC for Industrial, Scientific and Medical (ISM) usage. Since the radio band is regulated by the FCC, computer companies such as apple are petitioning the commission to "allocate a band of frequencies to be used for Data Personal Communications Services (Data PCS)." (Melanie McMullen, "Unleash Your LAN," Macworld [September 1993]:211.) Although the RF spectrum market is flooded, "RF WLAN is a short-range application, so the same frequencies can be used by systems that are not too close to one another." (A. Santamaria and F.J. Lopez-Hernandaz, editors, "Wireless LANs: An Overview," Wireless Lan Systems [Boston: Artech House, 1994], 3-4.) And to make more efficient use of the bandwidth that does exist, users of ISM bands transmit using various techniques called direct sequence and frequency hopping.

    2) The second problem of RF WLANs is interference. "RF signals can penetrate walls; this property is good because a data cell is not restricted to a single room, but it is bad if neighboring offices have their own networks . . . with other services." If there are adjacent or nearly located WLANs, one system can interfere with another.

    3) A third problem for RF WLANs is security. "As RF signals propagate through the walls, data security is an important subject to be considered, so encryption is mandatory to avoid information leakage."

 Spread spectrum transmission of RF lends itself to security because both direct sequence and frequency hopping distribute the bits of information either as replicated bits at one frequency or replicated bits on "a specific sequence of frequencies, where each frequency is used only for a short duration." (McMullen:211)

Unlike radio waves, infrared wavelengths cannot penetrate walls. This characteristic has pluses and minuses. The advantage of infrared data transmission is that what is transmitted in a room remains in the room. Infrared transmission is secure transmission because "infrared light, falling between microwave and visible light in the electromagnetic spectrum, shares some properties of visible light: it reflects off, but can't penetrate, solid objects, such as walls. (Therefore infrared networks are best suited for factory floors, open meetings, or close range, device-to device transfers, such as a print request from a PowerBook to a desktop printer.")

"In addition to the security of infrared transmission, infrared is immune to electromagnetic and radio frequency interference, making it unlikely that someone could interrupt or intercept data."

On the minus side of infrared transmission is loss of signal due to its characteristic of bouncing off of desks, walls, and even people. This bouncing around results in a diminished range of reception. However, given the rapid pace of technological development, the efficacy of wireless transmission will undoubtedly unfold as the "unconnected" technology of the future. In the meantime our group will present the following aspects of wireless LANs:

When do You Need Wireless LAN technology?

When to Choose Infrared Transmission

When to Choose Spread-Spectrum Transmission

The Advantages of Wireless LAN

The Disadvantages of Wireless LAN

Disadvantage of Spread Spectrum

Current WirelessLAN Products and their Configurations

When do You Need Wireless LAN technology?

  1. If you plan to move or remodel soon, but need to install a Local Area Network, a wireless LAN would be good to look into. Also, if your network is only temporary you could set up a wireless LAN, and still frequently relocate.

  2. One example, is if a new school puts up portable buildings for temporary use, they can install a wireless LAN and when that portable is removed they could set it up in another building.

  3. You would also use a wireless LAN if you needed true mobility. If you have employees who use portables or if you have traveling workers, going wireless might be your answer.

    LetÍs say you are at a conference regarding one of your students and your meeting place on campus does not have access to a computer. If your school had a wireless LAN, it could be set up to access that studentÍ s file.

  4. Other times you may want a wireless LAN if you have physical limitations such as having to set up a network in two separate buildings or if there is a road that separates part of your campus. Two additonal physical limitations are when you are not allowed to run underground cabling or if conduits are not feasible.

  5. A wireless LAN is ideal when there are strict building codes that do not allow you to run cabling. You may also want to look into wireless If you are in a historical building.

  6. If your walls have asbestos or lead trapped inside, you would need to go with a wireless LAN.
  7. If you do not have the time to configure and maintain a wiring scheme, wireless LANs would be quick and easy to install.
  8. Lastly, you should consider a wireless LAN if running cable is simply too expensive.

When to Choose Infrared Transmission

  1. Choose infrared transmision if your building has lots of potential radio interference. Infrared transmission is not affected by radio frequency.
  2. Infrared is great for setting up a wireless network quickly. It also does not require FCC licensing.
  3. Another advantage of infrared transmission is high security. The signals do not leave your building because they do not penetrate walls. Infrared technology covers about 20 feet and costs less than radio-based devices.
  4. If you have an open office environment, line-of-sight infrared transmission gives great speed and reliability when there are no obstructions.
  5. Line-of-sight transmission just means that it needs to be in view, or in the same room. It is sometimes referred to as point to point. An example is if your principal does classroom observations for PATH, he/she will be able to take along their portable computer. When he/she returns to their office, they can print up their observations without having to plug it in to a printer. The portable and the printer will work together as long as it uses line - of - sight infrared transmission.

When to Choose Spread-Spectrum Transmission

  1. Spread spectrum transmission is great if you need a quick, mobile network that offers the benefits of a wired network. This type of transmission offers microwave speeds without forcing you to get an FCC license, which may take several years to obtain.
  2. Spread spectrum transmission is ideal if you need to penetrate walls. Unlike infrared, which only allowed you to remain in the same room. This is because spread spectrum transmission can travel several hundred feet.

    This could eliminate the wiring involved from your schoolÍs central hub to each individual building, the janitorÍs closet. Hickam Elementary School is an example, because we have a building that is separated from the main part of our campus by a service road. We also have seven portable buildings that are on the other side of that building. By going wireless, we wouldnÍt have to worry about running conduits to those classrooms.

  3. Look into spread spectrum transmission if you need to have several networks in the same space. There is a way to set up multiple networks in the same space so that the signal from one network is interpreted by another as random noise and ignored.

The Advantages of Wireless LAN

The advantages of wlan are its portability, ease of installation, and practicality. The most appealing aspect of wlan is its convenience, it allows flexibility and roaming. A user is not tied down to a lan and can move around with relative ease while staying connected. Wlan are also easy to install, an entire network can be put together in a matter of hours rather than days. Finally, wlan may be installed where rewiring is impractical. Wireless systems can be installed in different environments and users can communicate with the existing wired network through access points or wireless adapters.

The Disadvantages of Wireless LAN

The disadvantages common to all types of wlan are its cost, transmission speed, connection distance, and FCC regulations.

The biggest block to growth of wlan are its high cost. Cabling costs can be as high as 40% of the whole installation and the cost needed to move fixed cables is more or less the same as a new installation. Wireless costs more than twisted-pair or coax cable. The average cost per node for a Ethernet connection is $150 to $300 per node and the average cost per node for a wireless connection ranges from $500 to $1,000 depending on the wireless technology used. Most buildings are already wired for communications unless you plan on several moves and relocations. Access points cost around $1800 and adapters are around $600 with potential speeds of up to 2 megabits per second.

Speed is another disadvantage of wireless lan. Wireless devices are almost always slower than the same network using a wired configuration (about 4 to 6 megabits per second).

Wireless lans can transmit up to 1,00 feet without losing connection. The rule of wireless transmission, the higher the data rate, the shorter the range.

Fcc regulations only applies to radio frequencies since fcc does not regulate the infrared transmission. Radio-transmission uses spread sprectrum transmission distributes, or spreads, a radio signal over a broad frequency range. There are not too many frequencies free for developing radio frequency (RF) wlan. 902megahertz to 928 megahertz is the frequency set aside by the federal communication commiccion in 1985 for the ISM industrial, scientific, and medical band-frequency referred to as the garbage band because of all the spectrum hogging equipment that already uses it -example commercial radio, television, and cellular phones.

Disadvantage of Spread Spectrum

Spread spectrum spectrum radio based networks are flexible since they can penetrate walls. Spread spectrum transmission distrubutes, or spreads,a radio signal over a broad frequency range. Radio transmission is unreliable near heavy electromagnetic transmissions and requires one transmitter per linked PC.

Disadvantage of Infrared Transmission

Infrared transmission is not government regulated and can not penetrate solid objects making it highly secure. Infrared is immune to electromagnetic frequency interference. An example of this is the Brokerage firm Lehman Brothers in N.Y. that uses a wireless infrared on the trading floor. Infrared devices tend to be smaller than radio devices and are cheaper. Infrared devices on line-of-sight tramsmission may have a decent data rate of 2 Mbps but extend only a short distance around 20 to 80 feet. Remember the general rule the higher the data rate, the shorter the range.

Disadvantage of Microwave Transmission

Microwave transmission can penetrate walls and are able to reach distances of 100 yards. FCC licensing is required for microwaves, this is usually reflected in the purchase price. Microwaves have about a 5.7 Mbps data range. Tranceivers required for this frequency range but they are a lot larger than those needed for spread spectrum or infrared transmission.

Current WirelessLAN Products and their Configurations

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AIRLAN CAN -Wireless Campus Area Networking by Solectek








Configuration for AirLan may be restricted to one room or to two rooms.

AIRLAN highly rated in the PC Magazine, uses spread spectrum radio technology. AIRLan is the most complete line of product available. No other single manufacturer offers both wirelss bridging for building - building communications and wireless roaming for inbuilding mobile computing.

AIRLAN offers a data rate of 2 Mbps and is compatible with Ethernet standards and all major network operating systems. It is also compatible with Digital and AT&T products.

AIRLAN/Bridge Plus $3,499 This is multiport wireless bridge for linking LANs and separate buildings up to 3 miles apart and at a rate of 2 Mps.

AIRLAN/Bridge Ultra A long-range wireless bridge capable of transmitting data up to 25 miles in point to point configuration. So if a school need to expand there wireless to another side 25 miles away this equipment could be used.

AIRLAN/Access The AIRLAN is the access point that is connected to a wired LAN and send and receive data from the other wireless computers. The has a coverage of up to 800 feet or 50,000 sq. foot area of wireless connection.Which will facilitates roaming for wireless notebook or portable computers from one location to the next while maintaining a seamless connection to the network. AIRLAN Access can also use 10 Base-T and coaxial connectors therefore Macinthosh machines can use this equipment.

AIRLAN/Parallel - Is the first wireless adapter to feature the plug-and play ease of parallel port installation in either portable or desktop PCs.

AIRLAN/PCMCIA is a credit card sized wirelss Ethernet adapter designed to provide complete mobility among notebook computers users.

AIRLAN/Internal A wireless network interface card for desktop PCs. Supports all major network operating systems and uses spread spectrum radio signals to penetrate walls, ceilings and floors up to 800 feet from the server. This wireless NIC is especially helpful in offices where computers are constantly relocated or difficult to link.


WINDATA by FreePort


One of the main components of the WINDATA product is the wireless hub. The wireless hub provides central control and management for a group of Wireless Tranceivers. A Wireless Hub is also used for connectivity to a backbone wired system. Each FreePort Wireless Hub can control up to 62 Wireless Transceivers with a basic service are of up to 80 meters (263 feet) from the Hub. This hub also filters data received fromt he wired backbone and routes it to the wireless Tranceiver. It also provides access control security by allowing the network manager to register the serial numbers of the Wireless Transceivers that are permitted to communicate with it.

The FreePort Wirelss Ethernet Hub consist of two components: The main chassis and the antenna that provides a 360 degree coverage.The chassis can be desktop or rack mounted.

A Wireless Tranceiver is a small unit that connects to one or more PCs, terminal or workstations. The Wireless Tranceiver connects to any standard 802.3 Network interface.

The Tranceiver receives IEEE 802.3 data packets from the PC or workstations, translates them to wireless protocol, and sends them to the Wireless Hub at a 2.4 mps. The Wireless Tranceiver also receives packets from the Wireless Hub at 5.7 mps. and sends them out the Ethernet connectors.

The Wireless Transceivers installs in minutes and requires no special technical expertise. The Wireless Transceiver consists of 2 components: the Transceiver itself and the Interface unit. The Wireless Tranceiver is small, attractive unit which can be placed in a variety of locations. Whether you choose to place it on your desk, mount it on a wall or hang it from a modular wall.

FreePort Prices FreePort Wireless Ethernet LAN system FreePort Wireless Ethernet Hub $7,450 FreePort Wireless Ethernet Transceiver $1,030 Windata Multi-Port Interface Unit (8 10-Base T ports) $ 745 Windata Single-Port Interface Unit (1 10BaseT & AUI) $745

WaveLAN by AT& T

PC Magazine has rated WaveLan their top choice. AT&TÍs WaveLAN PCMCIA adapter with the WavePOINT bridge are together an excellent choice for wireless LAN connectivity. This solution offers excellent range, good throughput and strong management features. One of the few things missing is a software utility.

WaveLAN PCMCI, which uses spread spectrum (direct sequence) comes in two pieces: A Type II card, which slides into your notebookÍs PCMCIA slot, and a small antenna unit, which attaches to the back of your notebookÍs display via an adhesive-backed mounting bracket. A flexible 18 inch cable joins the two wireless components. The antenna unit is entirely enclosed and easily removes from its brackets so you can lighten the computer.

The leader of the pack in several tests, WaveLAN outdistanced the competition when we used the WavePOINT bridge as an access point to connect stationary wireless WaveLAN clients to wired LAN. WaveLANÍs throughput remained essentially constant from 100 to 1000 feet. Indoor you are able to connect through two walls and glass door with only a moderate signal degradation.

Conclusion

In closing, the price of installing wireless LANs are more expensive than actually using cabling. Mobility is the number one reason for choosing wireless LANs. Business and companies on the mainland are utilizing wireless LANs more than we are in Hawaii. We could not find anyone who has successfully set up a wireless LAN in Hawaii. On the mainland, it is more prevalent due to the high lease rents which force businesses and companies to continually relocate. The initial cost of purchasing wireless LANs are higher, but in the long run, with constant relocation, it will save money for these businesses ancompanies.

In general, as large corporations and businesses move toward a mobile work force, we will see a higher demand for wireless applications. In the years to come, such a demand will, hopefully, bring down the existing cost of going wireless, thereby making it more affordable to a larger audience.

Then, perhaps, we may see schools in Hawaii getting into the wireless LAN technology of the future.