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Wireless LANs

 

Wireless LANs
An introduction to wireless networking hardware
October 30, 2001

 
Author:
 
Using the Internet Guide (Communication and Collaboration): Eric Leland



Wireless networking products have become more popular in the last few years due to an increase in competition among manufacturers and the emergence of a more dominant wireless technology standard. This report looks at the benefits and drawbacks of wireless networking and provides further resources for research into wireless products.

Definition: Wireless Networking

Wireless networking refers to hardware and software combinations that enable two or more appliances to share data with each other without direct cable connections. Thus, in its widest sense, wireless networking includes cell and satellite phones, pagers, two-way radios, wireless LANs and modems, and Global Positioning Systems (GPS).

Definition: Wireless LAN

Wireless LANs enable client computers and the server to communicate with one another without direct cable connections. Generally, a wireless LAN is connected to an existing wired LAN, although they can exist without a wired LAN (in this case, users will only be able to communicate with other users on the same subnet).

Components of a Wireless LAN

Necessary components include an Access Point, Client LAN adaptors and the wired LAN. The Access Point is a device that translates between the wired LAN and the wireless LAN. The Client LAN Adaptors are PC cards, PCI or ISA boards that plug into laptop or desktop computers equipped with radio transceivers to communicate with the Access point. Other components to a wireless LAN can include Extension Points and Directional Antennas. Extension Points are devices similar to the Access Point, but not connected to the wired LAN. Extension points serve to extend the range of the wireless network by relaying signals from client computers to the Access point. Directional Antennas serve to connect wireless networks located at a greater distance from one another. Each network would have an antenna targeted at each other (known as a "line of site" connection).

Technology Standards

Manufacturers have adopted many competing standards for implementing wireless communication. Interoperability between different communications standards is currently not available. It is important to evaluate, with any wireless LAN networking system, the technology it uses, the features it provides and the industry support it has. Below are common standards available:

 

Standard Coverage Speed Access Point Network Card
802.11b 150 feet 11Mbps $200 $100
802.11a 50 feet 50Mbps $300 $200
Bluetooth 30 feet 1Mbps N/A $50
UWB (no consumer products yet) 100 feet 40-1000Mbps $100 $100
HomeRF 150 feet 1.6-10Mbps $200 $100


 

  • IEEE 802.11b is sometimes referred to as "Wi-Fi". Currently this open standard, developed by the Wireless Local Area Networks Standards Working Group, is the most widely used wireless LAN system. Large technology companies such as Linksys, Apple, SMC, and 3Com have adopted it for their product lines. This technology uses radio waves in the 2.4-GHz frequency band (same as many other appliances such as cordless phones and microwaves) and has the potential for interference. Speed ranges from 1-11Mbps (newer products are most often specified at 11Mbps).
     
  • IEEE 802.11a is a standard that many believe will replace 802.11b in five years - vendors are scheduling its release in 2002, but widespread adoption will come some years later. Speed can reach 54 Mbps and travels on the less congested 5GHz band, reducing the potential for interference. Range is limited to 50 feet. More speed but likely more Access Points required. Some vendors are producing Access Points that will adapt to both the 11b and 11a standards as well as other standards (Enterasys Networks, Proxim and Agere are examples).
     
  • Bluetooth is an inexpensive, very low-powered and short-range frequency-hopping radio system that would link your pagers, personal access devices, cell phones, and laptops (designed for small, mobile devices). The potential for interference (shares 2.4 GHz frequency), particularly to the low-powered Bluetooth, remains an open problem. Range is only 30 feet but line of sight is not necessary - the distance limitation is a problem for serious LAN implementation, and not many Bluetooth LAN systems have been developed as a result. Named after the 10 centuryDanish King Harald, "Bluetooth" is the English translation of his last name "Blatand." King Harald was famous for uniting the kingdoms of Denmark and Norway and for his extensive travels; like King Harald, Bluetooth unites separate entities (peripherals, laptops, PDAs, Cellphones, cameras, etc).
     
  • Ultra Wide Bandwidth is an emerging technology that promises much higher bandwidth speeds at low costs. Inventor Larry Fullerton created UWB transmission as a radically different approach to data transmission. Instead of data being transferred within a given frequency (such as radio stations, who have one frequency on which to broadcast), UWB broadcasts its signal across the spectrum, using different patterns and combinations, avoiding the whole signal switching process that confines signals to certain frequencies. What about all those radio stations, will UWB interfere? Fortunately, the UWB signal is detected as noise by most radio receivers and is easily filtered out, although there is discussion among sectors that rely on low powered radio signals as to UWB's potential for interference.

    The speed of the transmission depends on the center of the spectrum on which the signal is transmitted. Plans are to initially roll out products at speeds of 40Mbps in 2002 (the PulseON chip developed by Time Domain of Alabama), then as the hardware size can be reduced in manufacturing, increasing this to 1GHz or more. Look for cheaper and faster wireless networking products over the next year!
     
  • HomeRF provides four high-quality voice transmission channels as well as a 1- to 5-Mbps data transmission channel. Designed more for the home network as it includes support for telephony together with data, lower costs and supports shorter range signals. Pushed by Intel but not an open standard, and speed is less than 802.11b (1.6 Mbps). Just released as of this writing is the new improved HomeRF that promises up to 10 Mbps. See http://www.homerf.org for more details.


How a Wireless LAN works

In a typical wireless LAN configuration, the Access Point connects to the wired network from a fixed location using standard cabling. The access point receives and transmits data between the wireless LAN and the wired network infrastructure. A single access point can support a small group of users and can function within a range of less than one hundred to several hundred feet. End users access the wireless LAN through the wireless-LAN adapters installed in their computers.

Benefits of Wireless LANs

Cost: Wireless LANs can cost less to implement than wired LANs, especially in situations where implementing a wired LAN requires extensive labor and materials to install the wiring and drops. For environments that are difficult to wire (such as schools or temporary spaces) a wireless network can be more cost-effective in the long run than a wired one.

Simple/flexible to Install: Wireless LANs eliminate the time needed with wired LANs for laying and pulling wires, and can reach places that cannot be reached by wires.

Portability: Wireless LAN systems can move physical locations much easier than wired LANs, reducing total cost of ownership for organizations that are on the move.

Mobility: Wireless LAN systems can provide LAN users with access to network information anywhere in their organization.

Scalability: Wireless LAN systems can be configured for small offices and large, with peer-to-peer systems or large established LANs, specific to the localized need of a workgroup or across the whole enterprise. Wireless LAN systems grow easily with the need by adding more access points, client LAN adaptors and extension points. Wireless can be a good solution if you need to connect several buildings without installing a wired connection. Wireless LAN bridges can extend LANs that are typically one to five miles apart. These wireless bridges span multiple-building LANs without incurring the monthly costs of a T1 or higher speed lines.

Drawbacks of Wireless LANs

Cost: In environments with installed wiring or less demanding wiring needs, the up front costs of adopting a wireless LAN system can be more expensive than with wired LANs.

Interoperability: There are several competing technologies used by wireless LAN vendors to communicate data between hardware, with no ability for communication directly between systems using these different standards.

Interference: Most of the wireless devices today operate on 2.4-GHz radio bands, which are also used by cordless phones and most microwave ovens. The potential for interference when used near other devices sharing the same frequency band.

Speed: Most commonly used wireless LAN products are rated for a maximum 11Mbps throughput, and in practice see speeds about 80% less than this - some wireless LAN products are rated for speeds much less than this (HomeRF systems for example). Still quite speedy for most network needs and for broadband Internet sharing, but for larger offices with high network traffic and demands for speed, this should be taken into consideration.

Wireless LAN Products

Simple wireless LAN systems provide an Access Point that is plug-and-play when connected to an existing wired network. They may or may not include client LAN adaptors. More advanced solutions function as stand-alone networking systems that often provide cable/dsl router, switch, DHCP and firewall technology together with an Access Point. As of this report, prices for Access Points range from $250 to $1500 each, and client LAN adaptors cost from $80-$200 each. When networking Macintosh systems, it is important to consider whether the product comes with macintosh drivers for the Access Point and the client LAN adaptors, and if there is a Macintosh version of the supporting administration software. If you've decided that a wireless LAN is the right networking solution for your organization, here are a few products that we recommend...

For the small office, D-link offers a wireless Access Point using the 802.11b specification plus two USB client LAN adaptors for $500 (kit with two PC cards for laptops costs $450). This unit has DHCP built in and can be used with or without an existing wired network. D-Link also offers an inexpensive stand alone Access Point (DI-713) for $200. PC only. See http://www.dlink.com for more details.

For larger systems, Orinoco AP-1000 offers a wireless Access Point with an array of features, including the ability to upgrade radio technology by swapping in new PC cards - thus if Orinoco decides to adopt a new radio standard, the Access Point can still be used. Also has load balancing, support for voice transmission, uses 802.11b standard, supports wired and fully wireless setups and more. Access Point costs around $900 and each client LAN adaptor costs around $150. Mac and PC. See http://wavelan.com/template.html?section=m58&page=103&envelope=94 for more details.

Apple Airport offers a wireless solution geared primarily toward Macintosh networks comparable to the D-link option ($300 for each access point, $100 for each LAN adaptor). One unique feature of the Airport is that HP makes a device capable of wirelessly sharing printers with the Airport Access Point ($300). Thus the printer does not have to be connected via wires to a server computer. Check out http://www.apple.com/airport/specs.html for information on the Airport.


Further Resources

Comparison of Several Wireless LAN Products (May 2001)
http://www.pcworld.com/reviews/article/0,aid,50415,pg,8,00.asp


Reviews of Wireless LAN products (Feb 2001)
http://www.zdnet.com/products/stories/reviews/0,4161,2685770,00.html


Apple Airport Access Point (popular Mac wireless networking product)
http://www.apple.com/airport/specs.html


TechRepublic: Wireless LAN Articles and discussion
http://www.techrepublic.com/article.jhtml?src=search&id=r00720010330bla01.htm


Good introduction on how wireless LANs function and their benefits
http://www.wirelesslan.com


Gartner Wireless LAN whitepaper (January 2001)
http://www.techrepublic.com/download_item.jhtml?id=dr00620000616ang13.htm


Gartner Bluetooth whitepaper (August 2000)
http://www.techrepublic.com/download_item.jhtml?src=search&id=dr00520000817ggr01.htm


HomeRF Standard Homepage
http://www.homerf.org/

Universal Client Wireless LAN Adaptors http://www.breakfree-technologies.com/images/aironet/uc4845.pdf

 

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