Radio frequency planning and channel optimization

The frequency band utilized will directly affect the total system throughput (TST) based on the number of available channels in each country based on that country’s regulatory adoption of the band.

While the 2.4 GHz band has been approved for use in most countries, the number of non-overlapping channels in this band makes 2.4 GHz unusable for LPV deployments. 2.4 GHz is not taken into consideration for any LPV planning.

Most HPE Aruba Networking access points include a 2.4 GHz radio but this radio is recommended to be disabled for client usage in large public venue deployments due to insufficient non-overlapping channels for high-density environments. While the 2.4 GHz band may optionally be repurposed for specialized applications like IoT devices or handheld scanners in targeted areas, 2.4 GHz should remain disabled for general client access. Legacy 2.4 GHz-only clients should be decommissioned in favor of 5 GHz-capable devices.

Customers should look to leverage both the 5 GHz and 6 GHz bands to increase capacity. The 5 GHz band offers more non-overlapping channels than 2.4 GHz, and 6 GHz provides even more, reducing interference and allowing more simultaneous connections.

Today’s current state of technology is based on Wi-Fi 7. The latest 802.11be standard builds upon the previous standard of 802.11ax and can operate across the 2.4 GHz, 5 GHz, and 6 GHz frequency bands.

Using 5 GHz

Available since the release of 802.11a in 1999, 5 GHz became widely adopted around the world. This band can now provide up to 28 non-overlapping 20 MHz wide channels, when including U-NII-4.

Using 6 GHz

6 GHz capable access points provide significantly increased capacity and with the 6 GHz band can handle more devices simultaneously without sacrificing performance, making them perfect for very high-density environments like conference centers, stadiums, and other public venues.

Wi-Fi 6, Wi-Fi 6E, or Wi-Fi 7 access points benefit from higher data rates, improved efficiency, and reduced latency. Wi-Fi 6E extends these benefits into the 6 GHz spectrum, offering more channels and less congestion. Wi-Fi 7 can also leverage 6 GHz.

Previously unused, the 6 GHz frequency range offers a vast amount of clean, uncongested spectrum. This means more bandwidth, less interference, and lower latency leading to significantly faster speeds and more reliable connections.

6 GHz offers wider channels, up to 320 MHz are possible and can deliver multi-gigabit speeds in a single collision domain with no overlap from other Basic Service Sets. In the LPV setting, there will be many Basic Service Sets using the same collision domain preventing scaling out and deploying wider channel widths.

This means optimizing Wi-Fi performance for tens of thousands of users in a large public venue requires careful balancing of throughput, capacity, and interference when selecting channel widths from 20 MHz to 320 MHz.

Channel width

5 GHz

Channels can be bonded together to increase the channel bandwidth, but historically any LPV deployment should use 20 MHz channels. This includes any deployment with more than 14 access points in a single area. The primary goal is to provide clients with separate collision domains to improve performance and user experience in the LPV setting.

6 GHz

Channel width selection depends on multiple deployment specific factors requiring careful evaluation at each implementation. Use appropriate channel widths (20, 40, 80, 160 or 320 MHz) based on the specific use case, AP density, regulatory constraints, and available spectrum of the environment to balance increased throughput with potential interference.

Careful consideration of the expected use of the network will help influence this design decision. Some main points to consider are listed below.

Utilizing narrower channels can minimize interference from overlapping channels, thus enhancing overall network stability and performance. While having more channels helps with capacity, each individual channel provides lower throughput compared to wider options, which might not be ideal for high-bandwidth applications.

In general, bonded channels should not be used in high-density areas such as large public venues.

Take for example a large public venue with over 50,000 visitors, 20 MHz non-overlapping channels at 6 GHz are significantly better than 80 MHz bonded channels because.

• Capacity and density - the primary challenge in such a dense environment is user density, not necessarily raw speed for individual users. 20 MHz channels allow you to serve many more concurrent users. Think of this like lanes on a highway. More, narrower lanes (20 MHz) allow more cars (users) to travel simultaneously than fewer, wider lanes (80 MHz), even if the wider lanes technically allow for faster speeds. With 50,000+ users, maximizing the number of simultaneous connections is crucial.

• Interference mitigation - in a crowded 6 GHz spectrum, interference is a significant concern. 20 MHz channels are less susceptible to interference than 80 MHz channels. A narrower channel is less likely to be impacted by adjacent channel interference or other radio frequency noise. With 80 MHz channels, a single interfering signal can disrupt a much larger chunk of the spectrum, impacting more users.

• Reduced channel contention - with more, narrower channels, the likelihood of channel contention (multiple devices trying to use the same channel simultaneously) is reduced. This translates to a smoother, more reliable experience for users.

• Simplified network management - managing a network with numerous 20 MHz channels is generally easier than managing a smaller number of wider channels, especially in a dense environment. It provides more granular control and flexibility for network optimization.

• Lower latency - while 80 MHz could offer lower latency under ideal conditions, in a real-world, high-density scenario, the increased contention and interference are likely to result in higher latency for many users. 20 MHz channels, while not as fast individually, would likely provide a more consistent and lower latency experience for the majority of users due to less congestion.

40 MHz channels represent a middle ground between 20 MHz and 80 MHz, and while they might seem like a compromise, they are still less suitable than 20 MHz channels for a large public venue with 50,000+ simultaneous users.

Consider the following:

• Capacity still a concern - while using 40 MHz channels offers more capacity than 80 MHz, they still provide less capacity than 20 MHz channels. In a venue with such a high user density, maximizing the number of concurrent connections remains the top priority. 40 MHz channels simply don’t offer enough “lanes” on the Wi-Fi highway to handle that many users efficiently.

• Increased interference risk - 40 MHz channels are still more susceptible to interference than 20 MHz channels. In a crowded 6 GHz spectrum, this increased risk can lead to performance degradation and dropped connections for a significant number of users.

• Device compatibility - while more 6 GHz devices will likely support 40 MHz than 80 MHz, there might still be some devices that only support 20 MHz. Sticking with 20 MHz ensures the widest possible compatibility and allows the maximum number of users to connect.

• Diminishing returns - while 40 MHz offers a theoretical speed increase over 20 MHz, the real-world benefit in a dense environment is likely to be minimal. The increased contention and interference will likely negate any potential speed gains, and may even result in lower overall performance for many users.

• Network management complexity - managing a network with a mix of 20 MHz and 40 MHz channels can add complexity to network planning and optimization, especially in a large venue. Sticking with a consistent channel width (20 MHz) simplifies management and allows for more predictable performance.

Additional considerations:

• Increased reuse distance - Using 80 MHz or 40 MHz channels reduces the number of radio channels by bonding them together.

• Thermal noise floor increases by 3 dB with each doubling of channel width. This means higher SINRs - 20 MHz channels experience up to 6 dB more SINR than 80 MHz channels for the same data rate, and up to 3 dB more SINR than 40 MHz channels.

• Higher performance - distributing 25 users each across four different 20 MHz channels delivers better results than placing 100 users on a single 80 MHz channel.

In a large public venue with 50,000+ users, prioritizing capacity and reliability over raw speed is paramount. 20 MHz channels offer the best balance of these factors, ensuring a usable and consistent Wi-Fi experience for the vast majority of visitors. While 80 MHz might seem attractive on paper, this approach is simply not practical or scalable for such a dense user base.

40 MHz channels might seem like a good compromise, they ultimately fall short of meeting the demands of such a large public venue with 50,000+ users. Again, the priority in such an environment is maximizing capacity and ensuring reliable connectivity for the majority of users. 20 MHz channels remain the most effective solution for achieving this goal.

Spatial efficiency is critical. When large numbers of users are present, optimizing channel utilization and providing the most dense coverage as possible, requires the solution architect to consider small channel sizes.

HPE Aruba Networking recommends not to use bonded channels in high-density areas unless the anticipated network and channel reuse dictates use.

Recommendations

Given the scenario of a large public venue with 50,000 users, choosing the correct channel width depends on usage patterns and network goals:

• Opt for 40 MHz channels if the focus is on maximizing throughput for fewer but bandwidth-intensive applications. 40 MHz is ideal where high-speed internet access for streaming and media-rich applications is critical, and the network can be managed to limit interference. However, we cannot opt for 40 MHz because the capacity is too high for effective channel reuse at 40 MHz channel width. Careful consideration, at a smaller venue size than the scenario, could be performed to evaluate if 40 MHz channel width is feasible. Please contact your account team for a more in depth conversation about this topic.

• Opt for 20 MHz channels since the aim is to maximize user capacity and ensure robust connectivity across a highly dense user base, reducing interference and improving overall user density management. This setup can better handle a large number of devices performing less data-intensive activities, like browsing and social media usage.

A hybrid approach may be most effective, dynamically adjusting channel width based on coverage area type, user distribution, usage patterns, and real-time network conditions. However, the network design must maintain consistent channel widths across the ESS. Inconsistent channel widths cause clients to prefer BSSes with wider channels over those with better signal quality, as channel width ranks higher in BSS selection criteria than signal strength.

Different areas of a large public venue cam vary greatly in the coverage and capacity required. Ticketing areas, gates, concessions, concourses and bowl areas all have different requirements. Advanced network management tools and careful planning can optimize channel utilization effectively in such a large venue.

Channel plans

All channel plans can be categorized according to three criteria.

1. Dynamic vs. static

   • A dynamic channel plan is one that can change in response to external events, such as interference or system load.
   • In a static channel plan, the channel numbers are fixed and should not change.

2. Global vs. local

   • A global channel plan uses the same channel list for all APs that terminate on the system.
   • A local channel plan uses different channel lists for different groups of APs on the same system.

3. Repeating vs. non-repeating

   • A channel plan is repeating if the same channel number is used more than once in the same coverage area.
   • A channel plan is non-repeating if the same channel number cannot be reused in the same coverage area.

Most indoor WLANs are dynamic, global, and repeating.

Typical examples for high-density.

• Global and non-repeating

  • University building with multiple adjacent lecture halls, with all channels available but no individual lecture hall can use the same channel more than once. Could be static or dynamic depending on exact configuration method used.

• Local and repeating

  • Outdoor stadium with the bowl area using outdoor-only channels and the suites and concourses using indoor-only channels.

  • Large arena bowl area with fixed channel assignments that uses DFS channels for capacity, while only non-DFS channels are in use in other parts of the facility.

• Static, local, non-repeating

  • A concert hall with two dedicated ticketing APs at entry gates on channels 36 and 149. Every gate features an identical setup.

  • Stadium press box with four dedicated APs that are hard-coded to channels that cannot be used in the bowl seating area.

  • A convention center with a “house” channel dedicated to presenters that exists on one AP in the front of every individual meeting room (and nowhere else).

• Dynamic, global, non-repeating

  • A press area with six APs that can use any channel but no channel can be used more than once.

Coverage strategies

Additional assumptions will be made based on the coverage strategy used. As stated, this guide and the online LPV rough order of magnitude calculator tool only accounts for overhead or underseat deployments. However, due to the variations of large public venues, certain considerations must be made. Each area of the LPV must be assessed individually and only one coverage strategy per area is recommended.

There is adjacent channel interference (ACI) and co-channel interference (CCI) in virtually every high-density deployment. So long as minimum separation distances are observed, ACI can be safely ignored in most high-density areas of 10,000 seats or less.

Remember that AP to AP spacing when using directional antennas, the AP’s should be no closer than 2 meters or 6.5 feet. Access Points utilizing integrated antennas should be spaced never less than 5 meters or 16 feet apart.

Overhead coverage

Side coverage

Floor coverage

Additional coverage considerations

• Venue design - the physical layout and construction materials of the venue can influence which approach is more effective.

• User density and behavior - high user density can favor underseat installations due to their ability to minimize interference, whereas overhead APs might be superior in less dense scenarios.

• Cost and scalability - underseat solutions can be more costly due to the number of APs required and installation complexity but might provide superior service in capacity-demanding environments.

• Temporary deployments - underseat placement can be used more readily in temporary coverage areas versus mounting Access Points overhead.

• Future-proofing - overhead solutions might more easily accommodate the integration of future technology updates with less disruption.

In general, the decision between overhead and underseat APs should be tailored to the specific requirements and conditions of the venue. In many cases, a hybrid approach leveraging both methods in strategic locations can provide the most robust and comprehensive coverage, balancing coverage quality and capacity while considering installation and maintenance logistics.

Overhead coverage

• Overhead coverage is a good choice when uniform signal is desired everywhere in the area.

• APs with integrated antennas may be used when the area’s ceilings are less than 10 meters or 33 feet high. For open spaces with minimal signal attenuation, consider integrated directional antennas for better control of signal propagation.

• If the ceilings are higher than 15 meters/50 feet use of external antennas should be used. If questions persist, consult with your account team for further consultation.

• No RF spatial reuse is possible with overhead coverage because of the wide antenna pattern and multipath reflections.

• In multi-floor venues, stagger the Access Points in each room underneath and do not place access points directly above one another.

• Floors generally absorb more RF energy than walls (10-15 dB is a typical range).

Advantages:

• Line-of-sight coverage - overhead mounting typically ensures better line-of-sight to users, reducing signal obstructions such as furniture or people.

• Wider coverage area - generally provides a broader coverage area, making overhead coverage more effective for covering large open spaces.

• Reduced physical interference - less likely to be blocked by objects or people, which can be particularly advantageous when utilizing higher frequency bands like 5 GHz and 6 GHz.

• Reduced reflection - higher placement can help minimize signal reflection and refraction that are common when signals interact with fixtures, furniture, or people, which is a significant consideration at higher frequencies due to their limited penetration abilities.

• Easier maintenance access - easier to access for maintenance and upgrades without interfering with seating or crowd movement.

Disadvantages:

• Potential for higher contention - if not adequately planned, can lead to more overlapping coverage areas, which can increase contention and interference.

• Installation complexity - may require complex installations in venues with high ceilings or other architectural constraints.

Side coverage

• Wall, beam, and column installations with side-facing coverage are very common in high-density areas.

• To reduce both Adjacent Channel Interference (ACI) as well as Co-Channel Interference (CCI), mount all the AP’s on one wall facing the same direction.

• Signal bleed outside of the desired coverage area is wasted as compared to overhead coverage.

• When mounting back-to-back, ensure proper channel separation to avoid interference. For access points configured with 20 MHz channel width, maintain a minimum of 40 MHz separation between radio channels. For example, use channels 36 and 44 rather than 36 and 36 or 36 and 40.

• Signal levels will be lower in the center of the room than on the sides.

Underseat coverage

• Should be used high-density areas with more than 10,000 seats.

• Underseat places APs create Picocells and that allows for a much higher radio density compared to overhead or side coverage schemes.

• Picocell designs leverage the natural human body loss that occurs to RF signals as they pass through a crowd (also known as “crowd loss” or “crowd effect”).

• Significant increases in total system throughput are possible because of increased RF spatial reuse.

• Because higher AP densities can be achieved, cell sizes can be as small as between 60-75 seats. This guide and the online LPV rough order of magnitude calculator use a default of 60 seats for underseat designs.

• APs should be evenly distributed and spaced to provide more uniform signal coverage in the area. Strive to make AP-to-AP distances as equal as possible.

• Minimum AP-to-AP spacing should never be less than 2 m (6.5 ft) when using external directional antennas.

• Minimum AP-to-AP spacing should never be less than 5 m (16 ft) when using integrated antennas.

Advantages:

• Proximity to users - placement nearer to users can enhance the quality of the connection due to reduced signal path length and attenuation.

• Reduced Co-Channel interference (CCI) - signal is more contained and less likely to interfere with surrounding cells, effectively compartmentalizing coverage.

• Targeted coverage - ideal for environments where the seating arrangement is fixed and dense, allowing for precise coverage planning.

Disadvantages:

• Physical obstructions - signals can be impeded by human bodies, furnishings, and other physical barriers, especially detrimental for higher frequency bands.

• Maintenance Challenges - harder to access for repairs or upgrades, as these might disrupt seating arrangements or require special scheduling during unoccupied times.

• Smaller cell size - each AP typically covers a smaller area, requiring careful planning to ensure comprehensive coverage without gaps.