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General Information
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June 29, 2007
• Vol.29 Issue 26
Page(s) 5 in print issue
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Maximize Coverage For Your Wireless LAN
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The number of wireless LAN implementations is growing by leaps and bounds. In some cases, traditional wired networks are being replaced by wireless technology, and in new network rollouts, there is a temptation to use some form of WLAN. Another serious challenge facing IT personnel is how to effectively merge wired and wireless LAN technologies while increasing coverage at the same time. There are now several variants of the IEEE 802.11 specification out there on the market; the most common are versions a, b, and g. So what are some avenues for increasing WLAN coverage?
 Find A Company Offering A Complete Solution
It’s important that the personnel responsible for implementing your network have an intimate knowledge of more than just the products they are installing. Sometimes the difference between getting the most coverage from your WLAN is not even about the products you’ve ordered but where they’re placed, how to configure them for maximum efficiency, and other detail-oriented issues.
For instance, John Halderman, a systems engineer at Tech Data (www.techdata.com), says, “Personally, I try to gather as much information concerning the request [as possible]. I ask questions in reference to any equipment already in place, how many users are involved, indoor or outdoor or combination of operation areas, access point or bridge operation, distances involved, and what Wi-Fi operability standard is being requested—802.11a, 802.11b, 802.11g, or a combination of all three.”
Halderman continues, “I also ask about the operating environment, such as building construction type [and] areas of desired coverage, and [I] request follow-up information such as drawings, photos, or the results of any site survey testing done.”
Companies that can provide a complete solution of products and services for WLANs include IBM (www.ibm.com), Trapeze Networks (www.trapezenetworks.com), and Black Box Network Services (www.Processor.com/BlackBox).
Perform A Site Survey
Many factors affect the coverage and performance of a WLAN, and the best way to uncover these is to do a site survey. The best time to do it is before implementation, of course, but it can also be useful for revealing problems with a WLAN that is already in place or helping to find ways to effectively expand an existing WLAN. According to technical documentation entitled “Planning a Wireless Network” by HP (www.hp.com/rnd/library/tools.htm), “Your site survey should yield a network design document that describes the location of each access point, its coverage area, and the 802.11a, b, or g channel selections for the access point.”
Consider The Three “Cs” When Creating A Network Design
Motorola (www.motorola.com) has published a whitepaper titled “How to Make Your Wireless LAN Work” that goes into detail about the site survey and its relationship to WLAN coverage (www.motorola.com/Enterprise/us/en_us/solutiondoc.aspx?navigationpath=id_801i&document=learn+more%2fid_357i).
Motorola says WLAN planning must take into account the context of your wireless network location and the network’s required capacity based on the number of users and the types of apps they will be using, in addition to the coverage you need. Without taking this approach, the site survey itself can quickly become cost-prohibitive, limiting ROI, and users can be disappointed with the coverage of the network once it is in place.
Use The Right Products For Your Application—Products That Work Together
Cheryl Jameson, another systems engineer at Tech Data, says, “As we move closer to wireless controller appliances, adding different manufacturers will not be recommended. Wireless controllers are designed to communicate only with their own access points, which are written with their code. Adding a third-party device will typically be recognized only as a rogue access point and will be rejected by the controller.”
“However,” Jameson continues, “even for a controller-less network, depending on how large the network is, using multiple manufacturers can be a management and logistical nightmare. Being able to manage your access points is key for optimal uptime on your network. Imagine having 30-plus access points with a mix of different manufacturers. Each access point has its own configuration software and firmware upgrades. They all seem to work fine, and then one day an access point has failed.”
This can make a typical problem even more serious for the IT personnel responsible for maintaining the network. 
by David Gilbert
Bonus Tips
1. Avoid Traffic Jams By Implementing QoS
As WLANs begin to carry more diverse applications, contention for bandwidth and reduced coverage that comes from diminishing signal strength is becoming a problem. Implementing Quality of Service can keep voice traffic isolated from data traffic, which will reward users with increased signal and throughput.
2. Use A Wireless Controller
These devices have been around awhile, but now their cost is coming down. WAN controllers, such as the Cisco (www.Processor.com/CiscoSystems) 4400 series, help improve network performance by improving coverage and optimizing bandwidth by communicating with access points on the network and adjusting signal strength for better coverage in a certain area if there has been a hardware failure or if interference is dropping coverage. |
Best Tip: Maximize Your 802.11a Infrastructure
Casey Collins, a certified wireless network expert with C3-Wireless (www.c3-wireless.com), says, “Many people have the misconception that 802.11a is obsolete or dead, which is completely false. In fact, the exact opposite is true—that it is continuing to gain in importance. All enterprise-class APs now ship as 802.11a/b/g, and there are several reasons.”
“First, 802.11a operates in the 5GHz U-NII bands, which are much less ‘crowded’ and ‘noisy’ than the 2.4GHz ISM band, meaning that there is less chance of interference from non-Wi-Fi devices such as microwaves, baby monitors, cordless phones, etc.”
“Second, 802.11a offers eight indoor non-overlapping channels, compared to three non-overlapping channels available to 802.11b or 802.11g devices, meaning there is a much better chance to design a network without co-channel interference. Also, this allows for greater possible total throughput in a given area.”
“Many users currently have 802.11a/b/g devices but have ignored the 802.11a side. Taking advantage of 802.11a would be a great way for them to gain significant performance and reliability from their wireless network that doesn’t exist with 802.11b/g.”
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Easiest To Implement: Use The Right Antenna
Easiest To Implement: Use The Right Antenna
As mentioned in one of our other tips, sometimes consumers are left with the impression that old products and standards are obsolete. Global Knowledge Training (www.globalknowledge.com) disseminates accurate information and trains users on how to put it to use. Its whitepaper “Eleven Myths about 802.11 Wi-Fi Networks” sheds some light on one issue that impacts WLAN coverage but sometimes gets overlooked: antennas.
For instance, the company says if you are trying to maximize coverage on only one floor of a building (primarily horizontal coverage), a high-gain omnidirectional antenna would be a good choice. However, if you need to cover multiple floors (vertical coverage and horizontal coverage), you will need to dig a little deeper into a specification called “beam width.” Beam width comes in horizontal and vertical flavors, and the horizontal beam width on an omnidirectional antenna is 360 degrees, as all directions are covered in that plane. If you want to increase your coverage in the vertical plane, you need to look at the vertical beam width specification for the antenna you plan to use. The other important specification to look into is the “gain” of the antenna. This will also have an effect on your coverage, but keep in mind that the highest gain is not always the best for your application.
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