Our experience for many competitions shows that networking issues are one of the most common for our system. This is impossible to resolve in software, so technically speaking "this is not our fault", however still can create poor experience of the system in general so we would like to give some tips to prevent the problems. 


Short summary:

  • Use multiple Wi-Fi access points instead of single router
  • Pay attention to the APs setup – channels, SSIDs, power level (see bellow)


What can cause the problems? 


We have noticed 2 most common problems:

  1. To many clients for the single router / access point
  2. Wi-Fi interference


1. To many clients for single Access Point / Router

First one is easy to explain: general "consumer" level routers as design to work with wireless 10-15 clients as maximum. High-level consumer may handle more, but this is really hard to predict. 



You can not estimate maximum number of clients by the maximum bandwidth. OVS clients are using really low bandwidth and most times works fine even with 54Mbps connection IF there is no interference and routers can handle given number of clients. You need to look/ask about the number of clients or just test it. Any way, connecting 50 clients to single access point (AP) might be a bad idea any way, so better solution is having more than 1 AP.


2. Wi-Fi interference


Wi-Fi is radio connection protocol, all Wi-Fi uses limited number of frequencies so other wi-fi networks in the same area may make your connection worse, even if your have password protected your network. For instance open public network at the same radio frequency may dramatically affect your connection quality (since your network and public network will share same frequency). 


Below are some tips to reduce interference.


2.1 Use multiple access points

  • Use several routers in access point mode (usually all consumer routers has this function) or use professional access point (for example Ubiquity is cheap and powerfull APs).
  • Place APs close to the clients (tablets/scoring panels), connect them with LAN wires to the router
  • Reduce APs signal strength. Higher signal strength means more interference with other networks. If we put AP at the judges panel we usually set up the strength somewhere between 10% and 50%
  • Use differen SSID (wi-fi name) for each AP. This will allow you to easily control to which AP you are connected to
  • If you AP/Router supports both 2.4GHz and 5GHz set different SSIDs for each band. This will allow you simple control over how specific device is connected to the network.

2.2 Connect OVS server with the LAN wire


This is quite obvious – every judge connects to the server, so having good connection between server and network is always good idea.


2.3 Select Wi-Fi channels manually and carefully. Speak to venue IT management to discuss possible solutions


Each wi-fi works at some "channel" (radio frequency inside of allowed frequency band). There are 2 types of frequency bands – 2.4GHz and 5GHz. Usually routers and APs marketing materials explains what bands are supported by the device. 


Inside each band there are several "channels" that can be used to setup wi-fi. 


Some of the channels are overlapping, here is the illustration:


You can setup your AP to work at less crowded and interfered channels. 


Here are simple plan:

1) Disable auto-channel selection at your routers and APs (they are usually bad at doing this)

2) Analyse wi-fi spectrum using one of the tools below or any similar

3) Speak to venue IT staff to free up one of the channels/disable open public wi-fi/find other solution

4) Setup your APs to use the best channels possible


There are several tools to analyze the wi-fi spectrum, i.e.:


Select the channel that have fewer overlaps with other networks, however we do not use "non standard" channels, if there is no strong reason for it. 

I.e. select between 1, 6, 11 for 2.4GHz band if all other APs are using same frequencies. 


If you would like to know more you can check this article for more detailed explanation: http://www.metageek.com/training/resources/why-channels-1-6-11.html and this CISCO test for deep technical details: http://web.archive.org/web/20150502223736/http://www.cisco.com/c/en/us/td/docs/wireless/technology/channel/deployment/guide/Channel.html.


For 5GHz band there are much more options (24): http://www.metageek.com/training/resources/design-dual-band-wifi.html so use 5GHz whenever possible.


2.4 Select narrow Wi-Fi channels (20GHz)


You do not need high bandwidth for using OVS. So to avoid interference setup your APs to use the lowest channel frequency as possible. Thinner channels usually means less interference. If you have 20/40 GHz option for channel width we recommend to disable 40/80/120 GHz options.


2.5 Disable support of old Wi-Fi standards if possible


Disable old protocols (b,g) if possible. For instance If all of your devices supports wi-fi N standard, switch the APs in n-only mode. 


2.6 Pay attention to points above and do not relay on tests without the spectators


Each one of the points above really helped us to resolve connection problems during the competitions. They called "tips", however we strongly recommend to implement each one of them beforehand. Wi-Fi reliability with and without spectators inside the Venue may be dramatically different, so if you are planning big event we really recommend to take all this points serious even if test in empty venue shows that you are good with single router.