Wireless IR network provides a combination of 10-Mbit/sec Ethernet and 100-Mbit/sec Fast Ethernet connectivity.
John Haystead
An invisible network lies beyond the loops of barbed wire and maximum security systems at Rikers Island Prison in New York. Carrying streams of medical records and data-intensive imagery of men and women for whom confinement is now a way of life, the network is based on optical wireless technology. Indeed, wireless infrared (IR) networks may be a bellwether for high-throughput, portable, high-bandwidth campus networks in years to come--and also a significant alternative to radio-frequency (RF) and standard microwave networks.
Rikers, in particular, is an example of how optical wireless can be used in "last mile" and closely guarded campus settings to solve seemingly intractable problems of network speed, multibuilding connectivity, and secure data transport. Pressure to move data--not prisoners--is paramount in any correctional facility. But when St. Barnabas Hospital (Bronx, NY) first won the contract to provide medical services to more than 18,000 Rikers inmates, hospital officials didn`t fully appreciate the challenges of transporting data, Magnetic Resonance Imaging (mri) scans, and other information in an environment specifically designed for isolation and confinement.
Because Rikers is responsible for the confinement of male, female, and juvenile as well as a variety of criminal "classes," the prison is actually subdivided into multiple, independent buildings, separated by 300 to 2200 feet. To minimize the movement and interaction of prisoners, separate medical stations are provided for each building, each with a minimum of one main clinic and pharmacy area. In addition, most buildings typically have a smaller remote annex clinic and satellite pharmacy or dispensing station.
A traditional wireline campus network based on T1 1.554-megabit-per-second technology could, in theory, be used for a new medical network. But Rikers was a special case. "Each [prison] site was actually a little island unto itself, surrounded by significant security systems," recalls Noah Caldwell, St. Barnabas Hospital vice president of information technology, who administers the project. "For obvious reasons, there was no interconnecting tunnel system between buildings, which meant a hard-wired system would be nearly impossible to implement," he says. Instead, Caldwell opted for a wireless infrared networking backbone provided by Eagle Optoelectronics (Boulder, CO).
The IR system consists of 24 LightStation link heads providing a combination of 10-Mbit/sec Ethernet and 100-Mbit/sec Fast Ethernet connectivity. This arrangement enables Rikers medical personnel to move data from the separate prison clinics to a centralized data center. Infrared networking, unlike wired systems, solves many of the infrastructure and security problems that burying cable in high-security facilities presents. In addition, the wireless IR systems offer specific advantages at Rikers over RF and microwave systems. (These other technologies were rejected due to special security, interference, and geographic considerations for the prison, including the island`s close proximity to New York`s La Guardia airport.)
Centralized connectivity
To handle the exchange of medical records and radiology images between all prison sites, St. Barnabas built a central data center on the island to which all the facilities connect via the Eagle Optoelectronics IR system. Using multibeam-multipath technology, Eagle`s LightStation systems are capable of data rates from 1 to 155 Mbits/sec and distances up to 2.5 miles. The LightStation MultiLink system also uses multiple transmit and receive optics, which allow for greater combined power output (while still operating below eye-damage threshold levels) as well as minimizing attenuation defects through the atmosphere. As a result, the system is more resistant to inclement weather such as fog and can carry signals over longer distances than many other optical systems.
A total of eight LightStation Monolink systems (600 meters) and four MultiLink systems are used at the site. The Monolink systems service the standard Ethernet connections while the MultiLink systems provide both the Fast Ethernet links at 100 Mbits/sec as well as the long-distance Ethernet connections. At Rikers, the longest link is about 2200 feet.
The medical data sent via the separate facilities are aggregated at the Rikers centralized data center. T1 lines link the Rikers data center to another Department of Corrections facility located in lower Manhattan as well as the St. Barnabas Hospital data center in the Bronx.
Two primary applications
At Rikers, the wireless local area network (lan) runs two primary medical applications. One is a traditional character-based hospital information system used for registration, laboratory, radiology, and pharmacy data. Provided by hbo & Co. (Atlanta, GA), the star 2000 management system software operates on a variety of hardware platforms, all sharing a single logical database to populate reports and transactions throughout the system.
The star software is actually hosted on a server at the St. Barnabas hospital data center on the mainland. According to Caldwell, this was done primarily to maximize synergies with the hospital`s operations staff. "Because the relative bandwidth requirements are minimal, [star] didn`t need to be physically located on the island," he said.
By contrast, Rikers`s other main healthcare application is extremely bandwidth-intensive. The hboc Pathways Image Manager is a medical-imaging archive and retrieval system that electronically captures, indexes, and stores all types of imagery related to a patient`s health chart. Multiple users access information and images simultaneously regardless of their location.
IR`s high bandwidth is critical for the Pathways application because 10 Mbits/sec is a minimum required to transfer large medical image files. For example, the minimum required resolution for X-ray imagery is around 2Kx2K, and even low-resolution images (800x600x24-bit) generate roughly 1.1 megabytes of data. Also, actual throughput requirements are considerably higher because system contention is always a factor. In addition, healthcare providers want virtually instantaneous data transmission and query response.
Currently, the St. Barnabas staff is populating the Pathways system with inmates` patient records as they are discharged from the prison medical facilities. The files are sent to a central scanning area where they are imaged by Kodak high-speed cameras, indexed using bar-code technology and stored on disks in a large optical-memory jukebox. The hospital has scanned all records of inmates discharged since January 1, 1998; Caldwell`s IT staff is now providing access to the system for individual users throughout the island and at the Manhattan location.
No picnic on Rikers
St. Barnabas first became involved with Rikers Island when it responded to nyc Health and Hospitals Corp. request for proposal last September. The contract called for taking over Rikers`s medical service while installing a new campuswide network on the island by early winter. This would be no simple task because Rikers had no existing network connectivity save for rudimentary dial-up connections. Without a campus lan/wide area network, though, "the hospital would lose money every day that the system wasn`t available and providing service," Caldwell says.
As Caldwell soon learned, however, time wasn`t the only problem. Before viewing the facilities at Rikers, he fully expected to install a campuswide T1 network. Caldwell then recognized the security problem. Tunneling for fiber installations was impractical. Even if the prison authorities approved (an unlikely scenario because this would require extensive excavation and large numbers of workers on the island), costs in time and money would be prohibitive.
Next, Caldwell considered RF and microwave solutions, but these also failed the test. "The Department of Corrections manages the assignment of RF frequencies on the island extremely closely. In fact, we had to get special approval just to use our two-way radios on the island during the installation process," says Caldwell. Because Rikers is located only 100 yards from La Guardia airport, Caldwell was also certain "there was no way the fcc was going to approve 10 microwave links."
Optical: the clear choice
Caldwell discovered Eagle Optoelectronics on the Internet (www.eagleopt.com), making his decision soon after contacting them. The immediate draw was high bandwidth, portability, consistently high throughput, and networking flexibility, suggests Perry Lewis, Eagle Optoelectronics`s director of sales and marketing. With the system, "Fast Ethernet links, for example, can also run E1/T1, Asynchronous Transfer Mode, Token Ring, Fiber Distributed Data Interface, etc., if plugged into this type of switch," Lewis says. Given the constraints on Rikers, optical was the only clear networking choice. "The uniqueness of the job drove me to the technology," Caldwell observes. "But in fact, it has proven to work very well."
Installation of the Eagle Optoelectronics IR system began and ultimately, 12 pairs of links (24 heads) in a mixed-bandwidth environment with redundant routing were installed. This provided an added measure of reliability. "We had our first four facilities up and operational by Christmas Eve and were completed by the end of January," Caldwell says. According to Heinz Willebrand, Eagle`s chief technology officer, "The installation could actually have been done quicker, but the in-building infrastructure also had to be brought up to speed. We spent time waiting for the installation of the in-building wired network."
The Eagle IR multipath technology gave Rikers another benefit: reducing the impact of weather conditions, particularly fog, which is clearly an important consideration for an island-based system. Initially, "the farthest location from the data center [Rose M. Singer facility] would go down in fog, but this turned out to be strictly a [transmitter] alignment issue. After the system was tuned up, everything was solid," Caldwell says.
Because the systems operate in harsh outdoor environments, Eagle Optoelectronics incorporated heaters and lens defrosters into the IR hardware--devices similar to rear-window defrosters. The lens heaters are set automatically to turn on when temperatures reach 37oF, ensuring performance regardless of cold weather.
Down to the wire
During network installation, the biggest challenge to IT was the age of Rikers`s buildings--and building-code requirements. In each facility, the main network electronics are installed in main distribution frames (mdfs) into which the LightStation units feed. Although the objective was to install the transmit and receive heads as close to the mdf as possible, line-of-sight restrictions sometimes required positioning up to 500 feet away. Because the LightStation units use inherently low-loss fiber-optic interfaces, this was not a problem for the data-handling portion of the system. Power, however, was another matter.
Code restrictions on running AC power outside the buildings (such as the mandated use of galvanized pipe) would have added substantial cost and time to the project. Instead, network installers decided to run DC power from the mdf to the heads, which if kept below 50 volts would not conflict with code requirements. This, however, posed a different problem because, although the LightStation units themselves only required 12V, the resistance in the wire over long distances would eventually drain the voltage below this level. Eventually, technicians installed a custom-developed, auto-sensing power supply, which determines the amount of DC voltage needed to push 12V to the system heads.
Remote monitoring
The Rikers contract included the installation of a complete simple network management protocol (snmp) environment to provide for remote wireless backbone monitoring. "[Monitoring] is particularly important at the Rikers facility, because I don`t have a direct presence and need to monitor network utilization and performance and have diagnostic tools available continuously," Caldwell says. "We can`t afford to waste resources."
Although all of the LightStation systems come standard with the company`s RS-232 Optical Management Interface for remote diagnostics, the Eagle snmp system allows remote monitoring of the entire wireless network from a single PC at the St. Barnabas data center. The system monitors both transmit and receive power levels.
Fiber-optic links run from each link head to the snmp box, which is plugged into the lan network via a regular IP address. At Rikers, the system links with Hewlett-Packard`s OpenView network management software, which monitors the entire network.
Caldwell sees the data-handling capabilities of the Rikers Island wireless network meeting his needs for the foreseeable future. But with imaging applications continuing to eat up bandwidth, overall network requirements will grow. "We already see a need for 100-Mbit/sec capability for several locations in the hospital itself," says Caldwell. One example is a planned teleradiology module that "will certainly demand 100 Mbits/sec to the desktop." Presumably, Fast Ethernet will be absorbed into the optical wireless fabric--even at desktop levels. Rikers may become a paradigm for wireless IR installations in high-security facilities of the future.
Depending on requirements such as speed and range, optical wireless systems transmit data signals using either high-power light-emitting diodes (LEDs) or high-power laser diodes (LDs). The operating wavelength is in the near infrared region of the electromagnetic spectrum at a wavelength around 800 nanometers.
The transmitter first writes the data signal onto a subcarrier, which is then used to modulate the beam of infrared light. A counterpart IR-light-sensitive receiving diode or photo detector then detects and decodes the infrared signal to retrieve the original data. To optimize sensitivity, the receiving diodes are fitted with a lens and filters to pass IR but attenuate visible light.
While conventional landline and other wireless technologies can still serve most users, an increasing number of high-bandwidth applications require optical wireless, especially for campus networks, says Heinz Willebrand, chief technology officer for Eagle Optoelectronics. "LAN network speeds and bandwidth requirements are increasing dramatically with more and more people migrating to 100-Mbit connectivity," he claims. "Many are already thinking about Gbps data rates."
"We`re definitely seeing more applications looking for higher speed and bandwidth," agrees Tom Baumgartner, VP of marketing for Proteon LAN Products (Westborough, MA). Driven by an overall desire to connect multiple buildings at full LAN speed, "our higher-speed products are today very close to half our total business," he says. Affirms Ken Ito, product manager for Canon USA`s Broadcast Equipment (Englewood Cliffs, NJ): "Just a few years ago there weren`t many ATM and FDDI applications in use. Now there are many more."
Government, healthcare and correctional facilities are becoming proving grounds for wireless IR. For example, the Washington State National Guard is using a JVC Professional Computer Products VIPS LAN-10 infrared wireless LAN to conduct training for guardsmen using mobile desktop units.
Cracking the bottleneck
While proprietary LANs may run efficiently at 100 megabits per second or faster within individual locations, users are often faced with a dramatic throughput bottleneck when they try to link multiple sites. Local telcos, for example, will usually suggest one or more T1 lines, which at 1.5Mbits/sec per line, will quickly run out of steam while costs soar. Similarly, RF spread-spectrum technologies can now provide up to 10Mbits/sec speeds, but can`t keep pace with faster LAN-speed connectivity needs.
T1 costs vary dramatically by location and distance, observes Perry Lewis, Eagle Optoelectronics director of sales and marketing. But the average cost to lease a single T1 line in NYC is $1000/month. To further illustrate, Lewis points to the example of one San Francisco company electing to use "dark fiber" OC-3 (155Mbits/sec) ATM connectivity to bridge between buildings on opposite sides of the street (approximately 100 yards.) The local telco provided the equipment at a setup cost of $27K which, together with a five-year leasing agreement at $4K/month, will cost the company $267K. By contrast, when the same company needed to increase its capacity, Eagle offered its 155-Mbits/sec IR-wireless system, installed behind glass windows, for $34K.
Cost analyses don`t always paint such clear advantages for optical systems, however. As Ito acknowledges, "Fiber is still more reliable than going over open air, and if you don`t have right-of-way issues and can bury fiber, this is generally a less expensive solution." Baumgartner agrees. "Over the long term, we feel our products offer a payback period over T1 costs, but we`re usually competing against very short lines, which are generally charged on a per-distance scale, so the payback period for IR systems may be a couple of years. "
Where hard-wiring isn`t an option, however, optical wireless systems offer clear advantages and often the only possible solution. Many business-critical systems also look to optical technology as a backup to their landline systems. "Microwave systems can also provide backup connectivity, but at a much slower data rate, whereas optical systems allow you to maintain your throughput," says Ito.
Portability is another factor. In many cases, users don`t own their buildings and may move to another location. With hard-wired systems, they will lose most of their investment, as opposed simply to taking their optical system with them.
Throughput is key
Wherever throughput speed and bandwidth are the principal criteria, however, optical wireless systems stand alone. "Higher speed is our biggest advantage over other technologies," Baumgartner says. Proteon offers optical wireless systems with up to 155Mbps ATM throughput, and "pricing is not a big problem," he claims.
Wireless optical systems such as Canon`s Canobeam II can deliver up to 155Mbit/s of bandwidth at distances up to 4 km with little or no impact from weather conditions. The Canobeam signal is concentrated into an extremely tight beam with an autotracking system to keep the beam on target. Says Ito: "Where cost will be a primary determining factor, we only target those applications where hard wire is not feasible or possible, but when bandwidth is critical, Canobeam can solve the problem."
As users expand beyond what has been considered the highest-end applications, so does the range of cost/performance options available in optical-wireless systems. For example, Canon`s high-performance product also comes with a relatively high price tag ($150-160K). However, "We`re high-end in both performance and cost," Ito says, "and although features such as autotracking add to cost, we`ve elected to emphasize sophistication and capability."
While there are still many applications requiring Canobeam II`s performance parameters, making it cost-competitive, Ito affirms there are also a growing number of applications that don`t require quite as much capability. "Based on market feedback, we have some lower-cost versions in R&D and expect to come out with lower-cost versions down the road."
Falling per-Mbps costs and rising bandwidth requirements may now drive the optical wireless market into high gear. So will customer recognition, Ito says. "More and more people are becoming aware that there is another solution out there that can meet their speed and bandwidth requirements."
Rikers Island Prison in New York uses optical wireless technology to solve problems of network speed, multibuilding connectivity, and secure data transport.
The art of alignment
Once the IR transmitter/receiver heads were in position and wired up, the rest of the Rikers installation proceeded smoothly, according to Eagle Optoelectronics`s (Boulder, CO) Perry Lewis, director of sales and marketing. "To align the transmitters and receivers, the systems are equipped with a built-in telescope and a signal-strength meter," he says. "The operator first looks through the telescope to the receive unit and aligns it in the crosshairs. Then both the transmit and receive units are put into test mode, which instructs the laser to send an alignment signal. This is measured by the signal-strength meter, thus fine tuning the connection."
By plugging in an external speaker or headset, the operator can also optimize the alignment; a higher pitch indicates tighter alignment. "After that, it`s simply a matter of securely tightening the mounting fixtures, although we usually go back several months later to check and fine-tune the alignments," Lewis says.
John Haystead is a technical writer from Surrey, ME. This article originally appeared in the July/August 1998 issue of Wireless Integration, another PennWell publication.