| technology | networking - Christian Scott
How to Connect Thousands of People to the Internet: Design Principles for an Arena
Wireless networks are everywhere. To the point that people expect to have free, high-speed wireless connectivity wherever they go. Large stadiums and arenas are no exception. Prior to COVID-19, thousands of people poured into such venues weekly for sports matchups, music concerts, and other events. As you might expect, providing WiFi for that many people over large spaces can be challenging. Let's look at the design principles that go into connecting thousands of people to the internet.
Why Provide WiFi in the First Place?
Yes, providing WiFi could take eyes off the main event, but venues still see tremendous value in providing wireless connectivity to spectators. Here are several key reasons why:
Event venues see tremendous value in providing wireless connectivity to attendees for several reasons:
- Through instant high-speed replays, social media engagement, and live statistics and scores, fans perceive the value of their entertainment experience to be higher, resulting in more frequent visits and returning customers. The result is increased revenue.
- Venue management can use wireless tracking data to provide customized advertisements to visiting fans, increasing the demand for concessions, merchandise, and membership services.
- Venue staff can process electronic payments using point-of-sale systems. Or even allow fans to pay for merchandise and concessions on their own mobile devices using wireless connectivity.
All of these benefits are great as long as the wireless networks supporting these features work efficiently. Designing wireless coverage systems for large entertainment spaces filled with thousands of wireless clients is challenging for several reasons. Some of the challenges associated with large, high-density spaces include free-space path loss, loud noise floor, and wireless access point load and coverage ability. Due to the revenue-impacting nature of wireless services within these spaces, a high-quality design and solution are critical.
As you study and prepare for the CWNA certification, you should understand the needs of stadium network users, the technologies available to create a successful coverage solution, and the proper process for designing, building, and testing high-density WLANs. Let’s start with the types of traffic and wireless clients you will find in stadium environments.
The Stadium Layout, Network-Wise
In general, you will find two types of wireless clients in stadium environments: staff and vendor network users. Or fans or guests who expect a high-speed internet connection. Staff and vendors might use wireless devices to support the events happening within the stadium. These could be point-of-sale devices, inventory tracking, communications systems, or video and security systems. Additionally, wireless networks could be used to understand where certain groups of fans are located to provide them with customized advertisements for services within the stadium or affiliated partners.
Fans and guests visiting stadiums usually expect a wireless connection to access stadium services and social media. Perhaps they want to see stats regarding the events happening in the venue. There are even applications that allow sports fans to see high-speed replays.
All of these services are important for a stadium to function as a business. Fans expect access to entertainment services. Employees need an internet connection to manage inventory, provide services, and process electronic payments to earn revenue to support the events. This is why physical design and environmental considerations are so critical.
In addition to the harsh physical environment stadiums inherently have, the large amount of space and sheer density of wireless users presents an additional challenge. To solve these problems, you will have to understand and work through a few critical components.
The first step you must take is to conduct a site survey. They can help you understand the coverage needs for a given area, the amount of noise present, and the approximate client densities you can expect. Some of the first questions you should ask your customer when conducting site surveys are “What applications will be used over this wireless network?” and “What types of devices will be used on the wireless network?”
Because we are talking about large entertainment spaces, you can generally assume that users will be using web traffic for payments and social media, video traffic for instant replays, and potentially voice traffic for keeping in touch with others. The types of devices in use on these networks are mobile devices such as cell phones, iPads, tablets, scanners, or other 802.11n or newer devices. The latter is an important consideration because you should make sure that your configuration limits connectivity to data rates supported by 802.11n devices or later. Older devices that support only older 802.11 specifications will operate at lower data rates, limiting the overall available throughput of the entire system.
The next key question you should answer is “Which areas of the space need to be covered?” This is important, as you could assume that the entirety of the space needs to be covered when in reality only the administrative offices and guest seating spaces need to be covered. The effect this has on your overall planning, bill of materials, and project costs are quite dramatic. Once you understand the area that must be covered, you should spend time identifying existing sources of interference, such as microwave links and other 2.4GHz traffic, existing wireless site survey data, and current issues with the wireless network your customer has noticed (including dead zones and problem areas).
Once you have all of these questions answered, you should request a blueprint of the space to layout access points on a visual map. You should document the current locations of wiring closets and other infrastructure devices, to ensure you can physically cable the access points, as well as power them via PoE or other means. Note that ethernet cabling suffers attenuation loss, making it unusable beyond distances of 150 meters or 300 feet. You should plan for this when designing your access point and wiring cabinet layouts.
Once your site survey and initial customer questions are answered, you can move onto the physical planning including your access point placement, access point models and antenna type, and coverage cells.
Physical Coverage Planning
One of the main problems you will encounter when planning for wireless coverage for large entertainment spaces is distance and line of sight. Radio waves travel much like sound waves; the further you are away from the source, the quieter or weaker the signal (sound) is. And if you are around the corner, behind a wall, or otherwise distantly removed from the source, you will suffer to receive adequate signal (or hear). These are two very important considerations in large outdoor spaces, as there are often physical obstacles such as large screens, speakers, rafters, rooftops, umbrellas, and other obstructions.
Lastly, the large amount of outdoor space between your wireless clients and wireless access points increases the impact of free space path loss — the signal loss experienced as radio waves spread out in free space. There are a few best practices you can implement in your designs to surmount these challenges.
- A balanced number of radios to wireless clients.
- An antenna type that meets your coverage requirements.
- Statically-defined power levels and channel assignments to avoid interference from neighboring access points and unnecessary roaming.
The best way to determine the number of clients that are supported per access point is to use a formula to estimate the amount of bandwidth being used per client in comparison to the total usage allotted on each of your access point radios. Many access points come with more than one radio, so the best material to reference on this topic would be the documentation from your hardware manufacturer.
In general, you can plan for an access point to be at max capacity when operating at 80% airtime consumption. This leaves room for bursts, new traffic, and management operations. The generic formula you can use for this is:
Number of client devices per radio = 80% airtime / device airtime usage = # of clients per radio.
To calculate device airtime usage if you are using 20 MHz channel widths, take the activity the device will be performing and divide that data rate by the device’s TCP throughput (which for 1:1 with no MIMO at 20 MHz is about 20-40 Mbps). HD Video, for example, is roughly 2-5 Mbps. So for one fan watching an HD instant replay, their device is consuming about 7.5% of the 20 MHz channel capacity (3 Mbps / 40 Mbps * 100 = 7.5%). This means that one channel at 20 MHz can support roughly ~10 of these HD video connections (80 / 7.5 = 10.6). If your access points have multiple radios, that would mean 10 of these connections per 20 MHz channel in use by that particular access point.
Based on this data, you can estimate how many radios you will need in your coverage area based on the estimated client density from your site survey. Next, you should consider the distribution and access methods you will use to connect your access points to the backbone network and subsequently, the internet. This is usually a combination of distribution and access layer switches that are installed in closets or racking throughout the facility. The switches at the distribution layer are typically responsible for backhaul connections back to your core switching or internet router. These are typically fiber and copper connections to core and access switches respectively. The access switches usually can provide power over ethernet (PoE) to devices. This is how your access points will be powered; power and data over one cable.
Once you have your access point layout decided, you can strategically place access switch cabinets in the vicinity of the access points to supply power and data. Next, you should consider the antenna type your deployment needs. For most implementations where overhead access points are mounted 35 feet or less from the clients they will be serving, stock omnidirectional antennas are great. In high-density deployments and deployments where access points will be mounted higher than 35 feet, you should consider using MIMO (multi-radio) patch or sector antennas, to increase your signal gain. This slings the signal closer to your clients while allowing you to reduce your radio power levels.
Lastly, you’ll need to statically set your wireless channels to alternate between access points, so that traffic is not overlapping. For access points that are right next to each other, you’ll need to reduce the transmit power significantly, while using patch or sector antennas to ensure there is no interference between your radios and client traffic. These channel selections and power levels should be defined beforehand and documented on your site plan so that you can easily reference the plan when configuring the radios on deployment day.
A few final things you should consider when working with your design are the reporting or integration requirements your customer has, the types of traffic and their priorities, wireless network names, and security methods. If your customer wants to use wireless network data to track clients moving throughout the space, you need to make sure the wireless networking equipment you are recommending supports this feature, and provides some sort of API or other integration for processing and using the data in a meaningful way.
You should also consider what networks the customer expects to be present after the final installation. You will likely end up with 2 to 3 networks. One for internal staff, one for vendors, and one for public guests. The former two networks are most commonly secured with WPA2 personal or enterprise authentication.
Personal authentication involves a shared secret that your customer can distribute for use. Enterprise authentication involves central authentication to an identity provider, allowing you to increase security with username and password combinations. Guest or public networks are typically not password protected, but often provide either splash page or text message authentication. These two features are often the data collection points that allow companies to track positioning within a physical space, so you should ask your customer which they prefer when configuring your SSIDs.
Lastly, for each SSID you configure, you should also set traffic priorities or QoS rules to ensure that critical internal and staff traffic takes priority over internet browsing and other tasks. This is because stadium vendors almost invariably prefer to process payments at concessions stands more quickly and effectively than accessing social media posts or instant replays. If you have designed your wireless coverage cells well, you should have plenty of throughput available for all of these tasks. QoS simply ensures the most important traffic gets through every time.
Designing a wireless network for large coverage areas and high-density environments can be very similar to designing for campuses and office environments. But throw in the added complications of free-space path loss and greater wireless demand from stakeholders. The best way to ensure success in a large stadium environment is to follow CWNA best practices, ask good questions, take your time in the design process, and understand the core principles at play in large-scale wireless deployments.
As you prepare for your CWNA exam, make sure you understand the types of wireless cases present in stadium environments, and some of the wireless deployment architectures and technologies you can use to support these dynamic cases.