Five Things to Know About Wireless Networks


By Art Reisman
CTO, APconnections

overwhelmed

Over the last year or so, when the work day is done, I often find myself talking shop with several peers of mine who run wireless networking companies.  These are the guys in he trenches. They spend their days installing wireless infrastructure in apartment buildings , hotels, professional sports arenas to name just a few.  Below I share a few tidbits intended to provide a high level picture for anybody thinking about building their own wireless network.

There are no experts.

Why? The companies that make wireless equipment are sending out patches almost hourly.  Because they have no idea what works in the real world, every new release is an experiment.  Anybody that works in this industry is chasing this technology, it is not stable enough for a person to become an expert. Anybody that claims to be an expert is living an illusion at best, perhaps wireless historian would be a better term for this fast-moving technology. What you know today will likely be obsolete in 6 months.

The higher (faster) the frequency  the higher the cost of the network.

 Why ? As the industry moves to standards that transmit data at higher data rates, they must use higher frequencies to achieve the faster speeds.  It just so happens that these higher frequencies tend to be less effective at penetrating   through buildings , walls, and windows.   The increase in cost comes with the need to place more and more access points in a building to achieve coverage.

Putting more access points in your building does not always mean  better service. 

Why?  Computers have a bad habit of connecting to one access point and then not letting go, even when the signal gets weak.    For example when you connect up to a wireless network with your lap top in the lobby of a hotel, and then move across the room, you can end up in a bad spot with respect to original access point connection. In theory, the right thing to do would be to release your current connection and connect to a different access point. Problem is most of the installed base of wireless networks , do not have any intelligence built in  to get you routed to the best access point,hence even a building with plenty of coverage can have maddening service.

Electro Magnetic Radiation Cannot Be Seen

So What?  The issue here is that there are all kinds of scenarios where the wireless signals bouncing around the environment can destroy service. Think of a highway full of invisible cars traveling in any direction they wanted.  When a wireless network is installed the contractor in charge does what is called a site survey. This is involves special equipment that can measure the electro magnetic waves in an area, and helps them plan how many and where to install wireless access points ;  but once installed, anything can happen. Private personal hotspots , devices with electric motors, a change in metal furniture configuration are all things that  can destabilize  an area, and thus service can degrade for reasons that nobody can detect.

The more people Connected the Slower their Speed

Why?  Wireless  access points use  a technique called TDM ( Time Division Multiplexing) Basically available bandwidth is carved up into little time slots. When there is only one user connected to access point, that user gets all the bandwidth, when there are two users connected they each get half the time slots. So that access point that advertised 100 megabit speeds , can only deliver at best 10 megabits when 10 people are connected to it.

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One Response to “Five Things to Know About Wireless Networks”

  1. Ken Says:

    Yours is an interesting approach to the wireless realm. I’ve been in wireless engineering for the last 5 years and I by no means consider myself and expert. Infact I agree that their are none. But, as an industry their are solutions to the issues you mention. Primarily the issue with walls,windows, etc. and radiation.

    Providing you are building a enterpise level wireless infrastructure, a wireless survey of the area is a best practice to avoid those pitfalls. Produces like AirMagnet and Ekahau will map out the number of AP’s required and db loss per wall and window.

    Most Cisco AP’s can provide air monitoring that may help identify magnetic fields like x-ray machine in the area.
    Any Access Point from the last few years from the major players (Cisco, Aruba, Ruckus) have MIMO technology and multiple antennas due to wireless being unidirectional. Like any radio system, wireless radios can only broadcast 1 at a time.


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