Stretching the LAN Wireless computing is about much more than mobility. It's about improving corporate efficiency and productivity and increasing profits. Find out how a wireless LAN is helping one site save $100,000 a year By Ron Levine

August  1997

Wireless LANs extend computing where wired systems have never before tread. More and more sites with environments hostile to traditional networks are now enjoying the advantages of close-at-hand computing power thanks to the strides made in wireless technology. We tell you what they're doing and how they're doing it. (3,100 words, including two sidebars, "Wireless spread spectrum technology primer," and "FCC sets aside free radio wireless spectrum")

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ireless computing offers many benefits for sites attempting to extend their LANs' reach into environments previously untouched by automation. These advantages include mobility and quick installation vs. cabled-systems, and the ability to sidestep many physical facility limitations and safety issues. Add the relatively low cost of wireless node installation to these benefits, and it's no wonder that many users are looking at this technology as a viable alternative to traditional systems.

But the attractiveness of wireless computing doesn't stop there. Many early adopters of wireless LANs are pleasantly surprised to find that these expected savings and benefits are coupled with extra revenue resulting from computer power being directly delivered into the hands of more employees. For example, wireless LANs are adding to one hospital's bottom line and contributing to a brokerage firm's profits by increasing productivity.

Factory facilities have been particularly hard to reach with the office LAN. Until recently, it's been impractical to bring computing directly onto a large production-line floor because of traffic, floor size, safety concerns, physical obstacles, environmental conditions, and the cost of dealing with these problems. But wireless LANs are changing this and placing the power of the computer everywhere!

Progressive manufacturers are already reaping the benefits of wireless LANs. Before wireless LAN communications were installed, their production managers' days looked more like an aerobics marathon than a desk job: they had to call up job specifications on their networked PC. Run down to the production line to take measurements. Run them up to the office and enter it into the computer. Receive adjustment data. Run back down to the line to recalibrate, as needed. Check on the finished product.

And then repeat the process, over and over and over. The obvious solution -- extend the corporate LAN all the way to the manufacturing floor where the data is both utilized and gathered -- doesn't prove workable in the typical wide-open plant floor.

Heavy traffic, long distances, safety concerns, physical obstacles, and such environmental conditions as electrical noise and interference, dust, and temperature extremes make the use of traditional wired connections impractical or impossible. Enter wireless computing. Wireless remote units, communicating over airwaves with a facility's LAN server, allow their operators to freely roam the manufacturing area as they collect real-time process control data and provide instant feedback to the stationary LAN segments.

With wireless LAN communications, process control information is available immediately at the production line, ensuring specification tolerances are being met. By gathering statistical operational data, monitoring the manufacturing processes, and initiating machine adjustments on the spot, quality control inspectors can assure quality standards.

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In practice: the factory floor
Pacific Datacom Systems (PDS), a Los Angeles, CA-based reseller specializing in LAN/WAN interconnectivity, has installed a number of wireless systems into manufacturing facilities. "Wireless devices can operate in the most demanding quarters and can work where wired computers can't. With them we're able to extend the LAN's reach right into the hands of the people operating the production equipment," claims Gary Greening, vice president at Pacific Datacom.

PDS cites one of its Los Angeles-based customers -- a manufacturer of high-precision aluminum parts for government, military, and industry -- as a typical example of when and how to utilize a wireless LAN solution. "Using the wireless approach, this customer was able to bring the LAN down to the production lines, alleviating the continual running back and forth between the production floor and the supervisors' offices to check drawings, specs, and other job related data. With the LAN reaching to the factory floor, production line personnel are able to check on manufacturing specifications, enter calibration measurements, and view other job data without leaving the shop area," Greening says.

Greening points out that the production area is an open air type of warehouse about the size of six large barns, and it is "an unfriendly" plant environment for wired computing. The shop has extreme amounts of electrical noise, and it must contend with interference. There are also metal particles, high temperature molded metal, and other contaminants in the air; all PC stations and data jacks would have to be protected at considerable cost. Operators need to wander the manufacturing lines, checking on production specifications, tolerances, etc. This requires mobility. "By going the wireless LAN route, we were able to just bypass all of these obstacles," states Greening.

Datacom's solution was to install a wireless LAN segment utilizing 12 industrial notebook 486, 66-MHz computers, from GaugeTalker Corporation. Each has eight megabytes (MB) of RAM, 550 MB hard disk space, and a wireless LAN adapter card with a three-inch antenna on the unit. These notebook PCs communicate over-the-air with three access points around the facility (both inside and outside). Each notebook node is serviced by its closest access point, allowing complete roaming in and out of the building without losing the LAN connection.

The access points are hard wired (with standard Ethernet cables) to the server and create a local bridge between the mobile notebooks and the client/server Ethernet LAN. The LAN is a mixture of stationary PCs and wireless notebooks, all operating together.

The adapters and access points employ a spread spectrum radio design, operating within the 2.4 to 2.48345-GHZ band. (See sidebar, "Wireless spread spectrum technology primer.") These bridges have an operating range of up to 1000 feet in an open space environment and can accommodate up to 15 LANs within the same physical space. With a throughput rate of 1.6 megabits per second (Mbps) per channel and 10 Mbps at the Ethernet side, the wireless LAN can handle the data transfer needs of the application.

Factory floors aren't the only places that pose heretofore insurmountable obstacles for bringing the business benefits of network computing directly into the hands of those who need it the most. The physical layout, heavy foot traffic, and the need for mobility has kept traditional computing off of the actual trading floors of the major stock exchanges, even though real-time access to databases and market information would greatly enhance a trader's knowledge.

Faster floor trading = increased revenues
Expanding revenues by increasing employee productivity is another avenue for increasing profits. Brokerage firms know that providing their traders with immediate access to computer databases containing up-to-the minute market information greatly increases their efficiency. They can make more trades in less time with complete accuracy. But despite the benefits offered, computers had not made it to the exchange floors -- until now!

The major stock exchanges are busy places -- crowded and fast-paced; there's on-going heavy foot traffic, and traders require unlimited mobility to navigate around the exchange floor. A stock exchange's trading area is not a "friendly" place for systems needing miles of wires and cables. Of course, these obstacles could be addressed by "burying" the necessary wiring and placing individual PC nodes everywhere a trader might roam. Unfortunately, the associated costs and facility alterations involved with this solution has kept network computing at an arm's length from the actual trading floors on all the major exchanges.

Hull Trading, LLC, an international trading company headquartered in Chicago, IL, has embraced wireless computing technology to meet the challenge of putting a LAN node in the hands of its traders. Warren Langley, a principal at the firm, explains, "Wireless was the final link we needed between our computer system's servers and the individual trader on the floor. By connecting the wireless PCs carried by our traders to the LAN servers elsewhere in the exchange's building through strategically placed access points acting as a bridge between the wireless LAN and the wired network, we are able to provide the traders on the floor with real-time market data, and each trade is recorded accurately as it happens."

For more than two years, Hull Trading has been relying on Fujitsu Personal Systems Inc. hand-held PCs, equipped with wireless LAN adapters for linking their traders with their corporate wide-area network. (All Hull Trading's LANs (wired and wireless) are connected via a corporate WAN.)

Hull Trading operates on the New York Stock Exchange, American Stock Exchange, Chicago Board Options Exchange, Chicago Mercantile Exchange, and on the Chicago Board of Trade. "Before the introduction of the wireless PCs, on all of these exchange floors, we were able to get information near somebody, but not actually to them. Hull had to rely on color-coded screens, hand signals, and price sheets to communicate trade data to its on-floor personnel; it was slow and inefficient," Langley says.

The hand-held wireless PCs give Hull a leg up on competitors by enhancing their traders' skills and by reducing the amount of time it takes to deliver the information they need.

With hand-held wireless PCs, Hull traders can quickly get the information they need and reduce the time it takes to deliver that information. According to Mack Sullivan, director of marketing communications at Proxim Inc., manufacturer of the RangeLAN2 wireless LAN technology used in the Hull wireless LAN system, "We supply the majority of wireless LAN technology to trading companies on the exchange floors, and we continually hear that individual stock traders have increased their trade numbers fivefold since they've been equipped with the wireless, hand-held PCs. And the trades are completed with a higher degree of reliability."

Hospital saves more than $100,000 per year in lost billing
As health care professionals who constantly strive to beat the clock, respiratory therapists must be able to perform a wide range of tasks with as few obstacles as possible. In a hospital setting, this challenge is compounded by the fact that their patients may be quickly whisked from one room or unit to another. In this environment, therapists need the flexibility to visit patients in different areas of the hospital, unrestricted by network cables or difficult data entry procedures.

Wausau Hospital in Wausau, WI, is a 321-bed regional referral center. The hospital's Respiratory Care department has 35 therapists, who see more than 7,400 patients per year. The facility's horizontal design means therapists must often travel considerable distances to make their rounds. In addition, the respiratory therapists were once required to complete a considerable amount of paperwork each time they visited a patient. The department sought a more efficient method for charting and charging. The solution was real-time, point-of-care information processing.

Wausau's Respiratory Care and Information Systems groups researched a number of processing alternatives and determined that a wireless solution could best meet their objectives. Based on an applications software package called Manager's Assistant from MediServe (Tempe, AZ) and the use of wireless Ethernet network adapters, the hospital implemented a solution to support patient tracking, scheduling, and billing.

The MediServe application software resides on the facility's local area network, and the client portion runs on nine laptop computers equipped with PCMCIA radio frequency wireless LAN adapters. There are 10 access points located throughout the facility to create a "cellular-like" network that allows therapists to roam freely while staying connected to the network.

The access points employ a spread spectrum radio design (frequency hopping -- See sidebar, ""Wireless spread spectrum technology primer."). They are effective for communicating with a server up to 1000 feet away in an open space arrangement. This wireless technology can accommodate up to 15 LANs within the same physical space. The throughput rates of 1.6 Mbps per channel and 10 Mbps at the LAN side are ample to address the data transfer needs of most PC LAN applications.

The laptops are connected via the wireless system to the hospital's Ethernet network. Data is transmitted from the laptops (through the wireless access points) to the LAN server. The server is linked to the facility's mainframe, which maintains patient registration and billing data.

During a visit with the patient, the respiratory therapist enters information into the laptop right at the patient's bedside. Data on the patient's status, any treatments and/or medications that are being administered, and the patient's response is included. During this process, the billing information pertaining to these treatments and medications is automatically captured and transmitted to the LAN server.

"Therapists transmit data to the main system after every patient visit," says Gary Nikolai, lead therapist for the Respiratory Care department. "This keeps our information updated in real-time, so the latest information is immediately available. Individuals, such as the section head and the department director, can also access the real-time information from their offices."

Issues of illegible handwriting, incorrect abbreviations, and inaccurate billing information have been virtually eliminated, Nikolai says. "With the wireless nodes, it's easy to see how many treatments are being done and to track the length of treatments," he says. "Now, charges are batched with specific treatments and are automatically billed to the patient's account."

Pam Ebel, systems administrator in Wausau's Respiratory Care department, says that the ability to obtain accurate billing information has played a significant role in improving efficiency. According to an in-house survey, the wireless application has saved Wausau Hospital approximately $100,000 in lost billing per year.

Wireless LAN technology is quickly becoming a common alternative to traditional, "wired" LAN nodes for businesses looking to stretch their networks into new areas and to empower mobile employees with real-time information. Be it the manufacturing floor, trading floor, or hospital floor, wireless technology is proving to be the right investment at many sites. By incorporating wireless PCs and modems into existing wired networks, LANs can now reach everywhere.

Ron Levine is a freelance writer based in Carpinteria, CA. He specializes in networking, storage devices, and emerging technology issues. His most recent story for SunWorld was "Network backup: understanding your storage options" (April 1997).

Reach Ron at ron.levine@sunworld.com.

If you have technical problems with this magazine, contact webmaster@sunworld.com

URL: http://www.sunworld.com/swol-08-1997/swol-08-lans.html

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Wireless spread spectrum technology primer

DSSS avoids excessive power concentration by spreading the transmitted signal over a wider frequency band. Each bit of data is mapped into a pattern of "chips" by the transmitter. At the destination the chips are mapped back into a bit, recreating the original data. Transmitter and receiver must be synchronized to operate properly.

The ratio of chips per bit is called the "spreading ratio." A high-spreading ratio increases the resistance of the signal to interference. A low-spreading ratio increases the net bandwidth available to a user.

DSSS products allow users to deploy more than one channel in the same area. They accomplish this by separating the 2.4-GHz band into several sub-bands, each of which contains an independent DSSS network. Because DSSS truly spreads across the spectrum, the number of independent (non-overlapping) channels in the 2.4-GHZ ban is usually limited to three.

FHSS technology spreads the signal by transmitting a short burst on one frequency, "hopping" to another frequency for another short burst and so on. The source and destination of a transmission must be synchronized so they are on the same frequency at the same time.

The benefit gained by employing FHSS technology products is that if interference occurs on one frequency, then the data is retransmitted on a subsequent hop on another frequency. The hopping pattern (frequencies and order in which they are used) and dwell time (time at each frequency) are restricted by most regulatory agencies. For example, the FCC requires that 75 or more frequencies be used and a maximum dwell time of 400 milliseconds.

FHSS products allow users to deploy more than one channel in the same area. This is accomplished by implementing separate channels on different, orthogonal, hopping sequences. Because there are a large number of possible sequences in the 2.4-GHz band, FHSS allows many non-overlapping channels to be deployed.

The use of spread spectrum technology provides wireless LAN users with the following benefits:

• Immunity to interference from outside sources: FHSS networks can simply "hop around" outside interference. Noise on any given frequency will typically be absent after hopping to another frequency. DSSS spreads the signal across a wide spectrum, thus the receiver can operate with a low response in any part of the spectrum.

• Immunity from multipath interference: Multipath interference is caused by a signal bouncing off walls, doors or other objects, causing it to arrive at its destination at various times. This type of interference is avoided by either hopping (FHSS) to a different frequency which is not attenuated or spreading (DSSS) the signal over a larger bandwidth.

• Increased network capacity: In the 2.4-GHz band, the maximum number of non-overlapping DSSS channels is 3, and the number of possible FHSS channels is 15.

• Network scalability: If a particular part of an FHSS wireless network requires additional bandwidth, a second access point (AP) can be added, doubling available bandwidth. Users roaming into the area will be randomly assigned to one of the two APs.

• Mobility, power, and weight: For mobile applications, low power consumption (extending battery life) and light weight is critical. A typical FHSS device consumes only 300 to 340 milliamps (ma) during transmission, and approximately 150 ma during receive mode operations. This technology also allows significantly lighter products to be developed.

• Security: DSSS products use a spreading code that allows the transmission to be mapped back into the original data. To intercept a DSSS signal requires capturing the signal and translating it back to the original data using a well-defined algorithm. However, DSSS products can be supplemented with specialized encryption devices.

FHSS was originally deployed by the military because of the fact that it is difficult to intercept and jam. There are infinite combinations of dwell times and hopping sequences. Capturing an FHSS signal would require significant development time and concerted effort.

FCC sets aside free radio wireless spectrum

The proposed new radio spectrum will be reserved for a new class of PCs, laptops, and terminal devices appropriate for schools. The wireless units will be outfitted with radio receivers and transmitters for transporting data over short distances.

Resources

• Pacific Datacom Systems
  http://www.pacdatacom.com
• Proxim
  http://www.proxim.com

If you have technical problems with this magazine, contact webmaster@sunworld.com

URL: http://www.sunworld.com/swol-08-1997/swol-08-lans.html
Last modified:

Wireless spread spectrum technology primer

DSSS avoids excessive power concentration by spreading the transmitted signal over a wider frequency band. Each bit of data is mapped into a pattern of "chips" by the transmitter. At the destination the chips are mapped back into a bit, recreating the original data. Transmitter and receiver must be synchronized to operate properly.

The ratio of chips per bit is called the "spreading ratio." A high-spreading ratio increases the resistance of the signal to interference. A low-spreading ratio increases the net bandwidth available to a user.

DSSS products allow users to deploy more than one channel in the same area. They accomplish this by separating the 2.4-GHz band into several sub-bands, each of which contains an independent DSSS network. Because DSSS truly spreads across the spectrum, the number of independent (non-overlapping) channels in the 2.4-GHZ ban is usually limited to three.

FHSS technology spreads the signal by transmitting a short burst on one frequency, "hopping" to another frequency for another short burst and so on. The source and destination of a transmission must be synchronized so they are on the same frequency at the same time.

The benefit gained by employing FHSS technology products is that if interference occurs on one frequency, then the data is retransmitted on a subsequent hop on another frequency. The hopping pattern (frequencies and order in which they are used) and dwell time (time at each frequency) are restricted by most regulatory agencies. For example, the FCC requires that 75 or more frequencies be used and a maximum dwell time of 400 milliseconds.

FHSS products allow users to deploy more than one channel in the same area. This is accomplished by implementing separate channels on different, orthogonal, hopping sequences. Because there are a large number of possible sequences in the 2.4-GHz band, FHSS allows many non-overlapping channels to be deployed.

The use of spread spectrum technology provides wireless LAN users with the following benefits:

• Immunity to interference from outside sources: FHSS networks can simply "hop around" outside interference. Noise on any given frequency will typically be absent after hopping to another frequency. DSSS spreads the signal across a wide spectrum, thus the receiver can operate with a low response in any part of the spectrum.

• Immunity from multipath interference: Multipath interference is caused by a signal bouncing off walls, doors or other objects, causing it to arrive at its destination at various times. This type of interference is avoided by either hopping (FHSS) to a different frequency which is not attenuated or spreading (DSSS) the signal over a larger bandwidth.

• Increased network capacity: In the 2.4-GHz band, the maximum number of non-overlapping DSSS channels is 3, and the number of possible FHSS channels is 15.

• Network scalability: If a particular part of an FHSS wireless network requires additional bandwidth, a second access point (AP) can be added, doubling available bandwidth. Users roaming into the area will be randomly assigned to one of the two APs.

• Mobility, power, and weight: For mobile applications, low power consumption (extending battery life) and light weight is critical. A typical FHSS device consumes only 300 to 340 milliamps (ma) during transmission, and approximately 150 ma during receive mode operations. This technology also allows significantly lighter products to be developed.

• Security: DSSS products use a spreading code that allows the transmission to be mapped back into the original data. To intercept a DSSS signal requires capturing the signal and translating it back to the original data using a well-defined algorithm. However, DSSS products can be supplemented with specialized encryption devices.

FHSS was originally deployed by the military because of the fact that it is difficult to intercept and jam. There are infinite combinations of dwell times and hopping sequences. Capturing an FHSS signal would require significant development time and concerted effort.

FCC sets aside free radio wireless spectrum

The proposed new radio spectrum will be reserved for a new class of PCs, laptops, and terminal devices appropriate for schools. The wireless units will be outfitted with radio receivers and transmitters for transporting data over short distances.

About the author
Ron Levine is a freelance writer based in Carpinteria, CA. He specializes in networking, storage devices, and emerging technology issues. His most recent story for SunWorld was "Network backup: understanding your storage options" (April 1997). Reach Ron at ron.levine@sunworld.com.