With football season well underway — fantasy football leaguers are already in the play-off stages — and many college bowl games coming up, we wanted to discuss the planning around wireless at football stadiums.
Stadiums and other areas that receive a lot of temporary but high-volume traffic have WLANs that have to be formatted in a particular way and use technologies, like 802.11k, to provide reasonable performance. So, if you are ever curious about the inner workings that make up a stadium WLAN and how a network engineer handles all the users and applications during game time, below is a quick overview of how it works, and what it’s comprised of.
Before Kick-Off: Planning Your WLAN Stadium Style
When you look at the topology of a wireless network, you can express it as a hierarchical tree with the ESSs (Extended Service Sets – all APs connected to the same Distribution System (DS)) at the top, then individual BSSs (Basic Service Sets – individual APs and their clients), and then the individual client nodes or stations (STAs) themselves.
When planning wireless for a large venue, like a football game, there is a limit to the number of STAs that can connect to each AP. More APs are needed to provide service to a larger number of users, however there are a limited number of non-overlapping channels for use by the APs. Thus, you have to carefully plan where you place your APs because if they are on similar channels, their signals will cause interference with each other, and slow down the STA traffic on both APs.
In very dense user scenarios, like a stadium, the power for each AP can be turned down so that only those STAs very close to the AP will see it and be able to connect to it. This also helps reduce interference between neighboring APs. But it can lead to user frustration since the number of AP choices will be limited, and if the assumed load per AP is exceeded the STA will have little or no alternatives for finding better performance.
Some manufacturers provide APs that are specifically designed for large, outdoor venues like stadiums, and these devices are for sure your best alternative. These APs typically include many radios, with the signal for each radio tuned in a different location. This enables a single “AP” to handle many more users (each individual radio is a BSS), provide better range due to the directional nature of the RF signal, and reduce problems associated with co-channel and adjacent-channel interference.
New technology is also being introduced to better manage user connectivity that will be applicable both for enterprises and large public venues. 802.11k, which is beginning to show up in APs designed for such purposes, will allow for better user distribution within a wireless network. Under most conditions today, it’s the STA that decides which AP to connect to, and it mainly decides based solely on signal strength. So if a lot of users are sitting close to a single AP, the STAs will all see very good signal strength and connect to that AP, typically oversubscribing it and causing poor connectivity for all users. In a WLAN utilizing 802.11k, the AP is given more control, and if it has a maximum number of users already connected the ESS will direct the requesting STA to connect to an underutilized AP, even if the signal strength is lower. This technology will not solve all of the issues with connectivity in a stadium setting, but it will certainly help.
Avoiding Non-Rivalry Related Conflict: Connecting Users to the Internet
Once we have the WLAN coverage addressed we need to get all of the users connected to the Internet. At public venues, like professional football games, guest access is the primary connection mode. Managing user credentials and security keys is just not feasible yet for thousand of temporary users. This of course is in complete contrast to an enterprise network, where only authorized users are allowed to connect, and it is easy to implement the highest levels of 802.11 security. So the next time you’re at a sporting event and connecting to the Internet, assuming you have a decent connection, keep in mind that your activities are NOT secure. Updating your status on Facebook is OK, but don’t be tempted during a lull in the action to purchase that jersey you’ve been eyeing on Amazon with your credit card.
And let’s not forget your “corporate” users. Even though this is mainly a public venue, it’s quite likely you will have employees who also need WLAN access, including hospitality and security workers. These users require secure networks with guaranteed bandwidth. When someone pays $150 a piece for seats on the 50 yard line, they expect premium service, and they expect it to be fast. You don’t want your WLAN to be slowing it down. The best way to address this is to have an overlay network, using the same equipment, but with a separate ESS with WPA-2 security so your corporate users will have guaranteed bandwidth on a highly-secure network.
The Necessities: Hamburgers, Beer and Wi-Fi Applications
Football attendees will most likely be accessing many different applications, especially web-based social applications. Although not a football stadium, AT&T Park in San Francisco received the third-most “check-ins” on Facebook in 2012. When users can’t access these applications, they aren’t happy.
If a user cannot access an application, there are only two culprits: the network or the application itself. But at a large venue, like AT&T Park, users are going to blame the network, and they’re probably right. So even though it seems like a perk, if you’re offering a public wireless network you’d better keep it running smoothly.
With packet-based network analysis, you get a complete view of your network, both wired and wireless. A wireless network is only as good as the wired network it connects to, so having visibility on both sides of the AP is critical. With packet-based analysis you can see the signal strength of each packet, follow an STA authentication from beginning to end, and review application response times once a user is connected. You can even inspect individual conversations between a client and a poorly performing application to determine if the problem is with the network or application. If a user request is followed by a quick network acknowledgment (ACK), but a delayed data response, it indicates an application issue—if it is delayed or missing an ACK then it’s a network issue. Network issues are also shown through slow acknowledgements, TCP slow segment recovery, slow and frequent retransmissions, and low throughput. On the other hand, applications usually manifest themselves in slow HTTP response times, especially for web-based applications like social apps, as well as slow database response times and inefficient client errors. It’s unlikely you’ll be doing this level of analysis for users at game time, but if user surveys indicate dissatisfaction with your WLAN offering, you can capture wireless network data during a game for later forensics analysis to see exactly how both networks and applications were performing for your users during the game.
Now when you’re watching a football game or possibly at a large event, you’ll know some of the inner workings involved in keeping the wireless network up and running smoothly. Please be sure to let us know if you have any additional questions about planning a WLAN for a large venue. We always want to hear back from our readers.