By Art Reisman, CTO, APconnections, www.netequalizer.com
with help from Sam Beskur, CTO Global Gossip North America, http://hsia.globalgossip.com/
Over the past several years we have provided our Bandwidth Controllers as a key component in many wireless networks. Along the way we have seen many successes, and some not so successful deployments. What follows are some key learnings from our experiences with wireless deployment,
1) Commercial Grade Access Points versus Consumer Grade
Commercial grade access points use intelligent collision avoidance in densely packed areas. Basically, what this means is that they make sure that a user with access to multiple access points is only being serviced by one AP at a time. Without this intelligence, you get signal interference and confusion. An analogy would be if you asked a sales rep for help in a store, and two sales reps start talking back to you at the same time; it would be confusing as to which one to listen to. Commercial grade access points follow a courtesy protocol, so you do not get two responses, or possibly even 3, in a densely packed network.
Consumer grade access points are meant to service a single household. If there are two in close proximity to each other, they do not communicate. The end result is interference during busy times, as they will both respond at the same time to the same user without any awareness. Due to this, users will have trouble staying connected. Sometimes the performance problems show up long after the installation. When pricing out a solution for a building or hotel be sure and ask the contractor if they are bidding in commercial grade (intelligent) access points.
2) Antenna Quality
There are a limited number of frequencies (channels) open to public WiFi. If you can make sure the transmission is broadcast in a limited direction, this allows for more simultaneous conversations, and thus better quality. Higher quality access points can actually figure out the direction of the users connected to them, such that, when they broadcast they cancel out the signal going out in directions not intended for the end-user. In tight spaces with multiple access points, signal canceling antennas will greatly improve service for all users.
3) Installation Sophistication and Site Surveys
When installing a wireless network, there are many things a good installer must account for. For example, the attenuation between access points. In a perfect world you want your access points to be far enough apart so they are not getting blasted by their neighbor’s signal. It is okay to hear your neighbor in the background a little bit, you must have some overlap otherwise you would have gaps in coverage, but you do not want them competing with high energy signals close together. If you were installing your network in a giant farm field with no objects in between access points, you could just set them up in a grid with the prescribed distance between nodes. In the real world you have walls, trees, windows, and all sorts of objects in and around buildings. A good installer will actually go out and measure the signal loss from these objects in order to place the correct number of access points. This is not a trivial task, but without an extensive site survey the resultant network will have quality problems.
4) Know What is Possible
Despite all the advances in wireless networks, they still have density limitations. I am not quite sure how to quantify this statement other than to say that wireless does not do well in an extremely crowded space (stadium, concert venue, etc.) with many devices all trying to get access at the same time. It is a big jump from designing coverage for a hotel with 1,000 guests spread out over the hotel grounds, to a packed stadium of people sitting shoulder to shoulder. The other compounding issue with density is that it is almost impossible to simulate before building out the network and going live. I did find a reference to a company that claims to have done a successful build out in Gillette Stadium, home of the New England Patriots. It might be worth looking into this further for other large venues.
5) Old Devices
Old 802.11b devices on your network will actually cause your access points to back off to slower speeds. Most exclusively-b devices were discontinued in the mid 2000’s, but they are still around. The best practice here is to just block these devices, as they are rare and not worth bringing the speed of your overall network down.
We hope these five (5) practical tips help you to build out a solid commercial wireless network. If you have questions, feel free to contact APconnections or Global Gossip to discuss.
Related Article: Wireless Site Survey With Free tools