Does anybody know what ever happened to that bridge President Clinton was going to build? The one spanning to the 21st century? No? While this Daily Feature article isn’t going to talk about that particular bridge, it is going to describe a number of technology solutions that will allow communication networks to span great distances. Specifically, I will focus on the Wireless Local Area Network (WLAN) Bridge and some of the various technology alternatives that facilitate communication from building to building.
By now, I expect most everyone is familiar with dial-up modem communication. This technology transmits digital data across a conventional analog phone line. A significantly faster technology, Integrated Services Digital Network (ISDN) practically became obsolete before it gained widespread acceptance in the United States. This technology still exists; however, it provides a maximum speed of 128 Kbps. This isn’t significantly better than the 56 Kbps that can be achieved via dial-up modem connections. In most areas, phone companies priced ISDN too high for consumers. Meanwhile, alternative technologies like cable modems and Digital Subscriber Line (DSL) have emerged. These offer significantly higher bandwidths at a much more reasonable cost.
Businesses have had a larger number of point-to-point communication options. Frame relay, T1, T3, as well as all of the aforementioned technologies are available to connect one facility to another. Still more alternatives are also now possible, thanks to advancements in microwave and optical technology. These devices use either microwaves or light to transmit data across great distances at very high bandwidths. The only limitations are that the two locations must be connected via line-of-sight, and must be within communication range for the transceivers.
The term WLAN Bridge normally refers to a 2.4-GHz microwave transceiver that connects the LAN within one building to the LAN within another. These devices can transmit up to 25 miles at data rates as high as 11 Mbps. Typically, there is a tradeoff between distance and bandwidth. These devices also suffer from atmospheric interference, so don’t expect high reliability in heavy rain or snow. Since the only way to intercept the signal is to place a receiver somewhere within the signal path, these devices offer excellent security. You won’t have to worry about packet-sniffers out on the Internet watching your activity, and the signals can be encrypted for even greater security.
One big advantage to the WLAN Bridge is that the customer can own the link. This means the customer never needs to worry about a service provider or monthly service charges! This also increases the peace of mind factor for those who don’t want their data going through somebody else’s servers. All wireless systems offer extremely fast and easy installation. This is usually the biggest selling point for wireless products and services.
In many cases, wire or fiber is just logistically impossible or totally impractical.
A number of vendors sell WLAN Bridges
Aironet, a division of Cisco, offers products that communicate in the 2.4-GHz to 2.4835-GHz frequency range with effective bandwidths of 1, 2, 5.5, and 11 Mbps. These devices vary in range from 22 miles for the 1 Mbps to 8 miles for the 11 Mbps. These devices all use direct sequencing spread spectrum, and they can support up to 2,048 unique Ethernet addresses. Proxim offers a similar WLAN Bridge.
Lucent has an 11 Mbps bridge that has a range of up to 10 miles, and it also has a 5.5 Mbps product that has a 16-mile range.
BreezeCOM claims its 2.4-GHz WLAN Bridge can operate over up to 15-mile ranges, and it can handle 1,024 Ethernet addresses.
AirFiber, Inc. and Terabeam have developed a laser-based optical technology for connecting LANs from building to building. These devices can achieve speeds of 100 Mbps; however, they are more susceptible to weather interference. Like their microwave counterparts, they also require line-of-sight conditions. Heavy fog can incapacitate these devices, as will rain or snow. These companies have not published their range limitations.
A technology, known as Multichannel Multipoint Distribution Service (MMDS), enables one central transmitter to communicate with a great number of receivers. BellSouth uses this technology to offer a competitive alternative to cable television here in Orlando, FL. This technology offers incredible bandwidth since it operates in the 2.5-GHz to 2.686-GHz frequency range. Transmitter power as low as 350W can reach great distances and the receiver equipment is fairly inexpensive.
Loma Scientific International has a number of MMDS products available. BreezeCOM also claims to have an MMDS-based ISP offering.
Another technology, Local Multipoint Distribution Service (LMDS), operates in the 28-GHz to 31-GHz frequency band. The FCC auctions off this frequency range, so the rightful owners of the various frequencies in each geographic area enjoy exclusive use of these devices. This technology offers huge bandwidth, which is also perfect for video on-demand. This could also be used in conjunction with other technologies like DSL. A bandwidth provider might offer extremely high download bandwidth using the LMDS technology while allowing customers to upload via DSL, ISDN, or conventional analog modem. For more information on this technology, please see the government-run N-WEST site.
A number of companies have opted to provide high-bandwidth solutions. These companies sell bandwidth as a service, as opposed to selling the equipment directly. Buying bandwidth service allows the customer to benefit from technology advancements such as LMDS and MMDS. This alternative allows the customer to avoid the initial equipment costs, but instead obligates them to a service agreement. This might be an ideal solution for the business that wants to completely outsource their connectivity issues. In many ways, this is more of a philosophical decision rather than a cost-driven decision.
In the event that you wish to investigate a bandwidth service provider, I have identified a number of them. Seattle-based Burst Wireless offers a number of bandwidth-based services. Teligent (NASDAQ:TGNT), Winstar Communications (NASDAQ:WCII), Nextlink (NASDAQ:XOXO), AT&T (NYSE:T), Sprint (NYSE:FON), WorldCom (NASDAQ:WCOM), and Nokia (NYSE:NOK) all offer numerous bandwidth services and solutions. Many of these companies have multiple redundant networks to ensure reliability.