Wireless networking seems to be something of a mystery to a lot of organisations that we speak with, however more and more it’s becoming a critical part of their infrastructure. If you get it right, you’ll have a rock solid experience comparable to being physically cabled. Get it wrong, and you’ll be cursed to live a life of buffering videos and frustrated staff.
The topic is enormous, however to get started we’d like to cover off a few little tips and tricks that we’ve picked up working with schools on their wireless design.
◉ Think of wireless as a half-duplex medium. Technically researchers have found a way to achieve full duplex communication, however the wireless access point you’re using will not be. Only one device gets to speak at a time, and before the device talks it listens to see if anyone else is already talking. The more devices you have on a radio, the more chance you will try to talk at the same time as another device. If this happens, you’ll both wait for a random period of time and try again.Put simply, more clients per radio will have an exponentially more detrimental affect on your clients. In line with what we’ve seen at schools using multi-media in class, we suggest ensuring you allow 10-20 clients max per radio. In a school this probably means you’re going to be using an access point per classroom.
◉ Restrict the use of 2.4GHz wherever possible as it tends to be a more congested spectrum. Andrew at Revolution WiFi has an excellent perspective on the problem here however in short – you probably want to use 2.4GHz as little as possible – especially if you’re in a space where you have poor wifi neighbours. The use of software programmable radios is an excellent strategy and there are vendors today who allow you to be flexible with your approach to radios (for example use dual-5GHz radios on a single AP). The traditional “fixed 2.4/5Ghz” radio vendors can and do work, but you’re going to be doing an awful lot more tweaking and chances are you’re going to have some AP’s deployed with radios turned off.
◉ Consider cell-sizing as a critical part of your design. Some wireless clients are fairly bright about working out the best signal to use, and you can rely on them to select the radio you want them to. Others are not, and some will hang onto a signal for dear life (iPads are notorious for this) even when that is not what you want them to do. If you design your cell sizes appropriately, you can minimise the chances that the device connects to the “wrong” access point. Just throwing every radio onto max may end up harming your wireless experience more than you might expect.
◉ Reduce the number of SSID’s that you use. Seriously. If you have more than 2 SSID’s, you probably need to check whether you really really need them. Again I’ll point you in the direction of Andrew over at Revolution Wifi to take a look at the SSID overhead calculator. I recently paid a visit to a school that had 7 SSID’s actively broadcasting, and in many spaces around the school had a decent chunk of co-channel interference going on. In one space where they were having plenty of problems, I observed 3 different AP’s sharing the same 2.4GHz channel, with a signal strength that was fine for my device, and 7 SSID’s on each. Using Andrew’s maths, approximately 77% of all airtime was being consumed with beacon frames… No wonder they were having a pretty poor time there!
◉ Do you really need 802.11b? Chances are high that you don’t and so you should disable it. If you have an 802.11b client it’s like having a tractor on a single lane road. Yes it still needs to get from A to B, and it can do so – but everyone else is stuck behind it and gets frustrated at how slow the tractor is moving. You can pick up a USB wireless dongle for about $50 and turn that old device into an MX5.
We’ve seen a number of wireless environments dramatically improved by simply addressing the five points listed above. Of course this is by no means comprehensive and as with all wireless networks, proper design is absolutely crucial to delivering an excellent experience. We’d love to hear some “rules of thumb” or tips and tricks that you’ve employed to eke the best out of your wireless deployment.