Top 10 Countdown: Getting Wireless Covered
A network manager who's seen it all debunks the myths of wireless network coverage.
Eric Crane is manager of Network Infrastructure, Security, and Servers at the UCLA Anderson School of Management in Los Angeles, CA. Crane manages the operation of Anderson's network infrastructure, including switches, routers, servers, and connection with the campus backbone. He is also responsible for development, implementation, and incident response for all security-related issues at the Anderson School, and serves on several university panels, including the Wireless Standards Committee. He was instrumental in implementing a wide-area network on the UCLA campus, during which time he and 5G Wireless (www.5gwireless.com) technology expert Carl Weisman identified some common misconceptions - 10 "urban legends" - Crane would like to see shattered.
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The cost of hardware will always drive total cost of ownership (TCO) higher because so many access points (APs) are needed.
- Not true. Instead, plan to deploy fewer, more effective APs.
- Less hardware means lower TCO.
You must have high data rates for your mobile users.
- Not likely. Mobile users commonly use less data-intensive apps such as e-mail.
- Typically, only 20 percent of the users are on the network at any given time, a factor which curbs the load.
It's better to use omni-directional antennas with 360-degree coverage.
- Actually, omni-directional antennas tend to have relatively low gain, limiting the range and coverage of the access points.
- Well-placed, higher-gain base stations may have up to 25 times the range.
You must have indoor access points to get indoor coverage.
- Not true. You can cover both outdoor and indoor areas with wireless signals that penetrate into buildings.
- An "outdoor-in" deployment can reduce the number of APs required for indoor coverage.
You need multiple access points per floor for adequate indoor coverage.
- Some wireless APs can cover up to three floors.
- Do your homework to find out how many APs you really need.
Mesh is the best approach for campus deployments.
- Actually, mesh networks have critical disadvantages, such as susceptibility to co-channel interference and bandwidth choke points.
- Each access point in a mesh network must contain network-aware intelligence to create a distributed network.
802.11g is better than 802.11b for mainstream wireless deployments.
- 802.11g is a short-range solution ideally suited to small indoor networks of heavy data users.
- 802.11b base stations can cover areas 25 times greater than 802.11g.
- Beyond 500 feet, 802.11b delivers a higher data rate and greater coverage than 802.11g, and 802.11g-only stops working entirely at about 650 feet.
To address dead spots, just add more access points.
- Not so fast! Because of co-channel interference, the additional APs may actually lower the range and/or data rate of nearby APs, or even cause new dead spots!
- Before adding more APs, consider: 100 percent coverage may not, in fact, be your objective.
To get outdoor coverage, you'll need a ton of access points.
- Not true. Wi-Fi hardware can easily provide 802.11b data rates out to 1.25 miles, for an area of 7.5 square miles.
- You can achieve wide outdoor coverage using a base station with multiple radios and high gain, directional antennas.
100 percent coverage should always be your objective.
- There are always overlaps and gaps that change as the network evolves.
- In adjusting power levels, and moving or adding APs, you may end up fixing one problem, but seeing another appear.
- 90 percent coverage may be all you need to provide full service to your customers.