Unbelievably it is still a frequent occurrence that arenas and stadiums provide poor WiFi experiences to it’s users.
For an end user, it is a common frustration that one of these problems occur: 1) the Wi-Fi network is accessible, but the connection fails. 2) captive portal authentication fails despite entering all required information, the user wonders whether this is her/his fault, 3) If the network connection has already succeeded, the connection may be pointless due to its slowness and intermittent outages.
This case study highlights how Ubiquiti Networks provided the FedExForum, a 18,000 seat multi-purpose arena in downtown Memphis, Tennessee, with a high quality WiFi experience. FedExForum is the home of the Memphis Grizzlies NBA basketball team and venue for several other sports events and concerts.
Arena Wi-Fi Needs Careful Planning
Making WiFi work effectively in large venues such as stadiums and arenas is challenging for numerous reasons:
1. Open Space
- NBA basketball court is 94 ft (28.7 m) long and 50 ft (15.2 m) wide. Overall length of the open area can be about 400 ft (120 m).
- Free space loss at 120 m distance is 88 dB. Phones have around +15 dBm transmit power, assuming no attenuation from hands and body. This means that the phone or AP at the other end of the arena in a direct line of sight will still receive the signal from the other phone or AP at -72 dBm level. This is well above the -82 dBm CCA frame detect threshold which keeps the channel occupied and no channel reuse is yet possible.
2. Human Bodies
- Up to 60% of a human body is water. Water, especially salty water like in the human body, efficiently absorbs RF.
- The arena’s propagation environment is different in a full arena. The network design needs to accommodate all conditions from an empty arena to a full arena.
- Body RF absorption is beneficial for the arena WiFi, since it helps to reduce reflections and increases RF isolation between access points and phones.
3. Limitations in AP Placement
- Access Points cannot limit visibility or distract guests.
- Common AP placements include catwalk, scoreboard, handrails, under the seat, and terrace or wall behind the seats. Directional antennas help to focus the RF energy.
- Different types of arena configurations (football, music concert) have an impact on the design. For example, basketball and concert configurations are different. In a busy arena, configurations change daily during the season.
4. High Peak Traffic
- Guest are using their phones the most before the event and during breaks. Traffic loads change quickly. For the best user experience, the network should handle all peaks with usable throughput.
5. Difficulties with Surveys
- Survey tools like Ekahau ESS measure WiFi coverage. The software runs on a laptop and the user moves in the measured space marking measurement spots to map with a mouse click.
- Full surveys are not possible during the games. Coverage survey is performed for an empty arena, but this fails to include the impact of human bodies.
- Surveying adapters have better antennas, and they display higher signal level than actual phones. In addition, there is significant variance between the phones, even within the same make and model.
Evolving Design
FedExForum offers three SSIDs: guest, staff, and press/media. The UniFi-Memphis SSID (for fans) does not use captive portal.
FedExForum offers the UniFi-Memphis SSID only at 5 GHz. The vast majority of phones already support the 5 GHz band. Models starting from iPhone 5 (launched in September 2013) provide 5 GHz Wi-Fi. Android devices also broadly support 5 GHz starting from Galaxy S III (November 2012) and HTC One X (February 2012). Most of the 2.4 GHz only devices are special use phones, not consumer devices. Low-cost entry-level laptops may also offer only 2.4 GHz, but fans do not use those at the arenas.
The Wi-Fi design at the FedExForum arena has evolved over time and continues to do so. The design used under-seat UAP-AC-M access points until early March 2018. Currently, the bowl design uses scoreboard- and catwalk-mounted BaseStation XGs (UWB-XG) and wall-integrated UAP-AC-IW-PROs at the Pinnacle level.
The UWB-XGs serve 14,250 seats in the lower and upper bowl areas. These high-density access points have three 5 GHz radios, each using a 10/15 dBi integrated directional panel antenna. All three radios have a different frequency range and include a band-pass filter to prevent adjacent radios from interfering with each other. Directional antennas help to focus RF energy and provide a significant increase in received signal level at the AP receiver. Better uplink SNR helps with air utilization since phones can use higher MCS and complete the transfer more quickly.
The RF design uses 20 MHz channels (VHT20) for maximizing channel reuse. Lower bowl and upper bowl use all 5 GHz channels, except 132-144. The Pinnacle-level APs use these channels. These APs use low RF power.
Use of scoreboard/catwalk-mounted multi 5 GHz radio APs is cost-efficient. Cabling and AP mounting can be a challenge, so minimizing the required work makes sense. Only 26 triple 5 GHz radio UWB XGs handle 14,250 seats. A quick calculation helps to check the feasibility. If 50% of the users would simultaneously use Wi-Fi, this would mean about 90 clients/5 GHz radio – which the radios can handle.
Performance Looks Superb
Arena capacity testing and performance data collection has included several phases and deserves a blog post of its own. One straightforward metric for performance is Speedtest.net collected throughput data. This data includes all tests performed by end users in the arena. Since raw data contains also wired tests, it makes sense to exclude all but iOS and Android data points for this purpose.
Performance looks great. Linear trend lines reach 50 Mbps for both uplink and downlink.
The lowest values are the most important. Over the whole period, only four samples are below 1 Mbps performance level. SLA calculated with 1 Mbps threshold gives 99.5% compliance for downlink and 98.5% compliance for uplink.
Performance remains excellent even during a game with 14,781 fans. Only two samples of 68 fall below 1 Mbps performance. This gives SLA 97% compliance.
On the average, FedExForum Wi-Fi offers 10-80 Mbps throughput during the games for each user.
UniFi SDN Controller Provides Insights into Network
The Ubiquiti SDN Controller provides insights into the network. These include DPI statistics, traffic volumes, and RF statistics like channel allocations, air utilisation, and frame retries. These help in tuning the network and troubleshooting issues.
The graph below shows a snapshot of client distributions at different channels. Channels 132-144 are less occupied since UWB XGs do not use them. UAP-IWs in the Pinnacle area use these channels. Those access points were installed after the game on 24/3/2018.
Arena Wi-Fi Redefined
UniFi BaseStation XGs have been designed for high-density environments and optimal performance without compromise. Integrated high gain antennas provide the reach to operate from the scoreboard or catwalk. Three 5 GHz radios in one AP means fewer APs, less mounting work, and faster deployment. The UniFi SDN Controller software provides an easy-to-use solution for deploying and managing the whole network. Combine all the previous with the Ubiquiti pricing model. UniFi arena Wi-Fi costs 15% of the solutions from competitors over a three-year period.
For the full blog, please visit https://blog.ubnt.com/