|Cutting the Wires|
|Written by Joe RudichHits : 535|
|Thursday, 31 December 1998 19:00|
Consider the bottom layer of the OSI Networking model that LAN administrators must inevitably memorize, the physical interface with a network. The point where the rubber meets the road is formally called network media, but we often refer to it by its more familiar name: cabling. After all, what other communication media is available besides fiber or metal wire? Of course, textbooks always point out that wireless media are potential optionsÑwith a strong emphasis on "potential." The most important form of wireless networking in current use arguably is the satellite transmission used to connect the distributed sites of multinational corporations and retail franchises. Those satellite dishes on the roofs of Burger King and Texaco were not installed to let the employees watch ESPN on their lunch breaks. Long before networks scale down to the LAN category, however, cable is king: It is inexpensive, robust, appropriate technology.
Wireless networking may be starting to move down from its meteoroidÕs-eye view of computers. A few companies are offering wireless network products that compete for medium-range backbone connections between buildings. One of these, RadioLAN Inc. (www.radiolan.com), sells a 10 Mbps, building-to-building unit called CampusLINK that can connect buildings up to 1,000 feet apart with line-of-sight antennae.
CampusLINK illustrates one of the problems of wireless networking: High-speed equipment is all proprietary, because the only defined standard, IEEE 802.11, does not exceed 2 Mbps. Legacy cabled networks are operating at 10 Mbps, many corporations already are implementing 100 Mbps Ethernet, and plans for 1 Gbps products are underway. Under these circumstances, the standard is woefully uncompetitive.
Cost has always been a concern with wireless technology, but spanning WAN distances may be more efficient without cable. CampusLINK costs $2,999 for each bridge and dish antenna unit, so a pair of buildings could be linked for about $6,000. In many circumstances, laying fiber or cable across a few hundred feet, and possibly negotiating right-of-way to do so, can be far costlier.
LAN administrators can attest that cabling often is the weak link in network chains. Not only can cable failures cause frequent network problems, they tend to shackle portable computers that are intended for true mobilityÑ-such as moving from cubicle to meeting within an office building without losing network connectivity. The only way to provide this type of access is through wireless networking.
Two technologies have been promoted as alternatives to cable in LAN arenas: infrared (IR) data transmission, the communication system of choice for both palm PCs and television remote controls, and radio-frequency (RF). Infrared has been used for some early wireless networking products, because it is less costly than RF, but is significantly limited by short range and "line of sight" requirements. Attempts at using IR for LANs are characterized by transceiver towers poking up from computers to "see" over cubicle walls, and by unexpected service interruptions when a tall person walks in front of a transceiver.
Radio-frequency LAN equipment recently has shown signs of dropping in price, however, and a handful of products might take wireless networking right to the desktop. The typical configuration for these systems includes transceivers for each PC, in either full-size expansion board, PC Card or external format; and regional access point stations. The access points cover an area up to 10,000 square feet.
In a small office or home, a single access point can take the place of a network hub. Several access points can be linked with common twisted-pair cabling to form a larger, more widespread wireless network, or access points can be plugged into regular Ethernet hubs to form a hybrid of wireless and wired connection capability within the same network.
These RF networking products can provide a wireless supplement to existing corporate networks, and are being used for highly mobile computers and areas that cannot be wired. The market at which most wireless networks are being aimed is small-office home-office buyers. Though this may come as a bit of a surprise, there are several compelling reasons.
Small officesÕ networks often are set up by owners themselves, and successfully installing LAN cabling can be an added challenge they would rather avoid. Also, the labor costs of hiring electricians to install cabling for three or four computers is far greater, on a per-system basis, than doing so with 30 or 40 computers. Finally, the 2 Mbps throughput of 802.11-compliant hardware is usually more than sufficient for a small number of networked computers.
Wireless LAN products
I tested several recently introduced RF networking packages in a home office setting, using one desktop PC and two notebook computers to create a small network. I linked these as a standalone network, not connected to a cabled LAN.
Lucent TechnologiesÕ (www.wavelan.com) WaveLAN wireless networking products are comparable in unit price ($500-$600 per PC) to infrared systems, and include PC cards, ISA cards, access points and range extender antennae. Each access point can cover a maximum area of about 1,200 feet in diameter, but the addition of a range extender antenna increases that to almost 1,500 feet.
When I tested WaveLAN equipment, the systems were linked by a single access point located on the upper level of a two-story house and the notebook computers were used throughout the building. I did not test WaveLANÕs range extender antenna.
Setting up the WaveLAN was surprisingly easy, considering the complexity of the technology. I inserted PC cards in each of the laptops and installed the card drivers provided with the WaveLAN kit. Installing the ISA card required some extra effort because the desktop system I used it in was running Windows NT Workstation, and Lucent did not include NT drivers. I was underway once I downloaded drivers from its Web site, however.
I found that the WaveLAN network operated very effectively, as the single access point picked up computers everywhere within the house but in the basement. The WaveLAN PC Card is sold for $495, the ISA Card is $545 and access points are $1,695 each.
An interesting third-party extension to the WaveLAN system is Netier TechnologiesÕ (www.netier.com) NetXpress SL 2000, a wireless workstation that runs Windows CE or lightweight versions of Windows 3.11 and Windows NT. The $799 system includes WaveLAN transceiver components, and can be upgraded to a full-fledged PC with the addition of a hard disk and a floppy and CD-ROM drive.
A very similar product line is AironetÕs (www.aironet.com) Series 4500, although it is designed exclusively for laptop PCs (it lacks a transceiver for desktop systems). AironetÕs PC card format transceiver, the PC4500, sells for $495, and its AP4500 access point is $1,795.
I tested two Aironet PC4500 cards in notebook computers running Windows 95, with a single AP4500 access point acting as a hub. I was able to move the two notebook computers throughout the house; in fact, the power of the Aironet equipment was quite impressive, as one notebook was able to copy files from a drive shared by the other as it was carried to the basement and then out on the porch.
The PC4500 initially could not be detected by AironetÕs installation process in one of my notebooks, but worked properly once a PC card modem was removed. That was my only installation problem, and otherwise the 4500s behaved just like a cabled network.
The least expensive of all products is offered by WebGear (http://www.webgear.com) in a $299 kit which outfits two PCs for networking without cables. The WebGear Aviator Wireless Network Kit is rated at only 500 Kbps, a speed nonetheless adequate for lightweight networking tasks. Unfortunately, the Aviator system is also considerably less robust than the WaveLAN or Aironet products, since it uses a 902 MHz to 928 MHz radio signal and no access point.
The Aviator modules plug into your PCÕs parallel port, so they are physically simple to install. Because these devices do not have a pass-through adapter, they cannot share the port with a printer (or any of the other devices crowding parallel interfaces). Ten- and 36-inch extension cables are included to let you position the modules away from the computer for better signaling.
Because the Aviator uses 902- to 928-MHz radio transmissions, some 900-MHz cellular phones and pagers could potentially interfere with the network connections. The range between Aviator modules is up to 75 feet in diameter, but testing showed that metal desks and file cabinets lessen the range considerably. The diagnostic softwareÕs graphical interface made it easier to position the modules optimally, though.
Although the Aviator drops the cost of wireless networking tremendously, it cannot really compete with the performance of higher-end products. WebGearÕs networking tool is a great improvement over built-in infrared links for occasional file transfer and synchronization, but itÕs not quite ready for prime-time LAN usage.
Wireless networking is becoming less of a Buck Rogers technology, as evinced by products that dare to introduce this cutting edge to the smallest of networks. Building a network with standard cabling and hubs still is less costly and complex than going wireless and will probably remain so for the near future. In many small offices, installing cabling is bothersome and the mobility of portable computers is a premium. Or sometimes, buildings simply cannot be wired. In either case, wireless products are now a decent alternative to wire, with relatively straightforward configuration and reasonable pricing. If wireless networking successfully penetrates smaller offices, it will inevitably find its way to larger networks when some of those startup companies grow into large enterprises.Executive Summary: The physical transmission of network communications has traditionally been limited to metal or fiber optic cabling, with its inherent limitations. To date, wireless networking has been too expensive and problematic to be a good alternative, but equipment conforming to a network standard is being embraced in small offices.