High Density Wi Fi Deployments Meraki From Cloudcontrolled

Summary

High Density Wi-Fi Deployments
High-density Wi-Fi is a design strategy for large deployments to provide pervasive connectivity to clients when a high
number of clients are expected to connect to Access Points within a small space. A location can be classified as high
density if more than 30 clients are connecting to an AP. To better support high-density wireless, Cisco Meraki access
points are built with a dedicated radio for RF spectrum monitoring allowing the MR to handle the high-density
environments. Unless additional sensors or air monitors are added, access points without this dedicated radio have to
use proprietary methods for opportunistic scans to better gauge the RF environment and may result in suboptimal
performance

Large campuses with multiple floors, distributed buildings, office spaces, and large event spaces are considered high
density due to the number of access points and devices connecting. More extreme examples of high-density
environments include sports stadiums, university auditoriums, casinos, event centers, and theaters

As Wi-Fi continues to become ubiquitous, there is an increasing number of devices consuming an increasing amount of
bandwidth. The increased need for pervasive connectivity can put additional strain on wireless deployments. Adapting to
these changing needs will not always require more access points to support greater client density. As the needs for
wireless connectivity have changed over time, the IEEE 802.11 wireless LAN standards have changed to adapt to
greater density, from the earliest 802.11a and 802.11b standards in 1999 to the most recent 802.11ac standard,
introduced in 2013 and the new 802.11ax standard currently being developed

Planning
In the recent past, the process to design a Wi-Fi network centered around a physical site survey to determine the fewest
number of access points that would provide sufficient coverage. By evaluating survey results against a predefined
minimum acceptable signal strength, the design would be considered a success. While this methodology works well to
design for coverage, it does not take into account requirements based on the number of clients, their capabilities, and
their applications' bandwidth needs

Understanding the requirements for the high density design is the first step and helps ensure a successful design. This
planning helps reduce the need for further site surveys after installation and for the need to deploy additional access
points over time. It is recommended to have the following details before moving onto the next steps in the design
process:
1
• Type of applications expected on the network
• Supported technologies (802.11 a/b/g/n/ac)
• Type of clients to be supported (Number of spatial streams, technologies, etc.)
• Areas to be covered
• Expected number of simultaneous devices in each area
• Aesthetic requirements (if any)
• Cabling constraints (if any)
• Power constraints (It’s best to have PoE+ capable infrastructure to support high performance APs)
Capacity Planning
Once the above mentioned details are available, capacity planning can then be broken down into the following phases:
• Estimate Aggregate Application Throughput
• Estimate Device Throughput
• Estimate Number of APs
Calculating the number of access points necessary to meet a site's bandwidth needs is the recommended way to start a
design for any high density wireless network

Estimate Aggregate Application Throughput
Usually there is a primary application that is driving the need for connectivity. Understanding the throughput
requirements for this application and any other activities on the network will provide will provide a per-user bandwidth
goal. This required per-user bandwidth will be used to drive further design decisions. Throughput requirements for some
popular applications is as given below:
Application Through
Web Browsing 500 kbps (k
VoIP 16 - 320 k
2
Video conferencing 1.5 Mbp
Streaming - Audio 128 - 320
Streaming - Video 768 kbp
Streaming - Video HD 768 kbps - 8
Streaming - 4K 8 mbps - 20
Note: In all cases, it is highly advisable to test the target application and validate its actual bandwidth
requirements. It is also important to validate applications on a representative sample of the devices that are to
be supported in the WLAN. Additionally, not all browsers and operating systems enjoy the same efficiencies,
and an application that runs fine in 100 kilobits per second (Kbps) on a Windows laptop with Microsoft Internet
Explorer or Firefox, may require more bandwidth when being viewed on a smartphone or tablet with an
embedded browser and operating system
Once the required bandwidth throughput per connection and application is known, this number can be used to determine
the aggregate bandwidth required in the WLAN coverage area. It is recommended to have an aggregate throughput for
different areas such as classrooms, lobby, auditorium, etc. as the requirements for these areas might be different

As an example, we will design a high-density Wi-Fi network to support HD video streaming that requires 3 Mbps of
throughput. Based on the capacity of the auditorium, there may be up to 600 users watching the HD video stream. The
aggregate application throughput can be calculated using the below given formula:
(Application Throughput) x (Number of concurrent Users) =
Aggregate Application Throughput
3 Mbps x 600 users = 1800 Mbps
Note that 1.8 Gbps exceeds the bandwidth offerings of almost all internet service providers. The total application
bandwidth we are estimating is a theoretical demand upper bound, which will be used in subsequent
calculations

3
Estimate Device Throughput
While Meraki APs support the latest technologies and can support maximum data rates defined as per the standards,
average device throughput available often dictated by the other factors such as client capabilities, simultaneous clients
per AP, technologies to be supported, bandwidth, etc

Client capabilities have a significant impact on throughput as a client supporting only legacy rates will have lower
throughput as compared to a client supporting newer technologies. Additionally, bands supported by the client may also
have some impact on the throughput. Meraki APs have band steering feature that can be enabled to steer dual band
clients to 5 GHz

Note: A client supporting only 2.4 GHz might have lower throughput as compared to a dual band client since
higher noise level is expected on the 2.4GHz as compared to 5 GHz and the client might negotiate lower data
rate on 2.4GHz

In certain cases, having dedicated SSID for each band is also recommended to better manage client distribution across
bands and also removes the possibility of any compatibility issues that may arise

Note: The option to have 2.4GHz only SSID is disabled by default. Please contact Meraki support to enable this
feature

To assess client throughput requirements, survey client devices and determine their wireless capabilities. It is important
to identify the supported wireless bands (2.4 GHz vs 5 GHz), supported wireless standards (802.11a/b/g/n/ac), and the
number of spatial streams each device supports. Since it isn’t always possible to find the supported data rates of a client
device through its documentation, the Client details page on Dashboard can be used as an easy way to determine
capabilities

4
Example Client details listing
Wi-Fi is based on CSMA/CA and is half-duplex. That means only one device can talk at a time while the other devices
connected to the same AP wait to for their turn to access the channel. Hence, simultaneous client count also has an
impact on AP throughput as the available spectrum is divided among all clients connected to the AP. While Meraki has
client balancing feature to ensure clients are evenly distributed across AP in an area an expected client count per AP
should be known for capacity planning

Note: In order to ensure quality of experience it is recommended to have around 25 clients per radio or 50 clients per AP
in high-density deployments

Starting 802.11n, channel bonding is available to increase throughput available to clients but as a result of channel
bonding the number of unique available channels for APs also reduces. Due to the reduced channel availability, co-
channel interference can increase for bigger deployments as channel reuse is impacted causing a negative impact on
overall throughput

Note:In a high-density environment, a channel width of 20 MHz is a common recommendation to reduce the
number of access points using the same channel

Client devices don’t always support the fastest data rates. Device vendors have different implementations of the
802.11ac standard. To increase battery life and reduce size, most smartphone and tablets are often designed with one
(most common) or two (most new devices) Wi-Fi antennas inside. This design has led to slower speeds on mobile
devices by limiting all of these devices to a lower stream than supported by the standard. In the chart below, you can
see the maximum data rates for single stream (433 Mbps), two stream (866 Mbps), and three stream (1300 Mbps). No
devices on the market today support 4 spatial streams or wider 160 MHz channels, but these are often advertised as
optional "Wave 2" features of the 802.11ac standard

5
Streams 20 MHz Channel Width 40 MHz Channel Width 80 MHz Channel Width
1 Stream 87 Mbps 200 Mbps 433 Mbps
2 Streams 173 Mbps 400Mbps 866 Mbps
3 Streams 289 Mbps 600 Mbps 1300 Mbps
The actual device throughput is what matters to the end user, and this differs from the data rates. Data rates represent
the rate at which data packets will be carried over the medium. Packets contain a certain amount of overhead that is
required to address and control the packets. The actual throughput is payload data without the overhead. Based on the
advertised data rate, next estimate the wireless throughput capability of the client devices. A common estimate of a
device's actual throughput is about half of the data rate as advertised by its manufacturer. As noted above, it is important
to also reduce this value to the data rate for a 20 MHz channel width. Below are the most common data rates and the
estimated device throughput (half of the advertised rate). Given the multiple factors affecting performance it is a good
practice to reduce the throughput further by 30%
Throughput
Protocol Data rate (Mbps) Estimated Throughput (1/2 advertised rate)
w/Overhead
802.11a or
54 Mbps 27 Mbps ~19 Mbps
802.11g
1 stream
72 Mbps 36 Mbps ~25 Mbps
802.11n
2 stream
144 Mbps 72 Mbps ~50 Mbps
802.11n
3 stream
216 Mbps 108 Mbps ~76 Mbps
802.11n
6
Throughput
Protocol Data rate (Mbps) Estimated Throughput (1/2 advertised rate)
w/Overhead
1 stream
87 Mbps 44 Mbps ~31 Mbps
802.11ac
2 stream
173 Mbps 87 Mbps ~61 Mbps
802.11ac
3 stream
289 Mbps 144 Mbps ~101 Mbps
802.11ac
Estimate the Number of APs
It's important to document and review the requirements and assumptions and confirm they are reasonable. Changing
one assumption will significantly impact the number of access points and the costs. If you assumed just 1.5 Mbps for HD
video chat (as recommended by Microsoft Skype and Cisco Spark) you would need half the number of access points. If
you assumed 5 Mbps was required for HD video streaming (as recommended by Netflix) you would need more access
points. If you were designing to support 600 1 stream devices instead of 600 3 stream laptops, you would need roughly
3 times the number of access points. For this example, we now have the following requirements and assumptions:
• Video streaming requires 3 Mbps for HD quality video
• There will be 600 concurrent users streaming video to their laptop
• Every user has an Apple MacBook Pro or similar
• All laptops support 802.11ac and are capable of 3 spatial streams
• The network will be configured to use 20 MHz channels
• Each access point can provide up to 101 Mbps of wireless throughput
We can now calculate roughly how many APs are needed to satisfy the application capacity. Round to the nearest whole
number

7
Number of Access Points based on throughput = (Aggregate Application
Throughput) / (Device Throughput)
Number of Access Points based on throughput = 1800 Mbps/101Mbps
= ~18 APs
In addition to the number of APs based on throughput, it is also important to calculate the number of APs based on
clients count. To determine number of APs, first step is to estimate the clients per band. With newer technologies, more
devices now support dual band operation and hence using proprietary implementation noted above devices can be
steered to 5 GHz

Note: A common design strategy is to do a 30/70 split between 2.4 GHz and 5 GHz
For this example, we now have the following requirements and assumptions:
• There will be 600 concurrent users streaming video to their laptop
• Concurrent 2.4 GHz clients = 600 * 0.3 = 180
• Concurrent 5 GHz clients = 600 * 0.7 = 420
We can now calculate roughly how many APs are needed to satisfy the client count. Round to the nearest whole
number

Number of Access Points based on client count = (Concurrent 5 GHz
clients) / 25
Number of Access Points based on client count = 420 / 25 = ~17 APs
Now the Number of APs required can be calculated by using the higher of the two AP counts

Number of Access Points = Max (Number of Access Points based on
throughput, Number of Access Points based on client count)
Number of Access Points = Max (18,17) = 18 APs
8
Site Survey and Design
Performing an active wireless site survey is a critical component of successfully deploying a high-density wireless
network and helps to evaluate the RF propagation in the actual physical environment. The active site survey also gives
you the ability to actively transmit data and get data rate coverage in addition to the range

In addition to verifying the RF propagation in the actual environment, it is also recommended to have a spectrum
analysis done as part of the site survey in order to locate any potential sources of RF interference and take steps to
remediate them. Site surveys and spectrum analysis are typically performed using professional grade toolkits such as
Ekahau Site Survey or Fluke Networks Airmagnet. Ensure a minimum of 25 dB SNR throughout the desired coverage
area. Remember to survey for adequate coverage on 5GHz channels, not just 2.4 GHz, to ensure there are no coverage
holes or gaps. Depending on how big the space is and the number of access points deployed, there may be a need to
selectively turn off some of the 2.4GHz radios on some of the access points to avoid excessive co-channel interference
between all the access points

Note: It is recommended to have complete coverage for both bands

Note: Read our guide on Conducting Site Surveys with MR Access Points for more help on conducting an RF
site survey

Mounting Access Points
The two main strategies for mounting Cisco Meraki access points are ceiling mounted and wall mounted. Each mounting
solution has advantages

9
Ceiling mounted MR, Cisco San Francisco
Ceiling mounted access points are placed on a ceiling tile, T-bar, roof, or conduit extending down from the roof. This
brings advantages such as a clear line-of-sight to the user devices below and flexibility in where to place the access
point. Access points can be easily placed with even spacing in a grid and at the intersection of hallways. The
disadvantage is the ceiling height and the height of the access point could negatively impact the coverage and capacity

• If access points have to be installed below 8 feet (~3 meters), indoor access points with integrated omni antennas
or external dipole/can omni antennas are recommended

• If access points have to be installed between 8 - 25 feet (3 - 8 meters), indoor access points with external downtilt
omni antennas are recommended

10
Wall mounted MRs, Cisco San Francisco
When ceiling heights are too high (25+ feet) or not feasible to mount access points (hard ceiling), a wall mounted design
is recommended. The access points are mounted on drywall, concrete or even metal on the exterior and interior walls of
the environment. Access points are typically deployed 10-15 feet (3-5 meters) above the floor facing away from the wall

Remember to install with the LED facing down to remain visible while standing on the floor. Designing a network with
wall mounted omnidirectional APs should be done carefully and should be done only if using directional antennas is not
an option

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Pole mounted MR66 with Sector antennas, Cisco San Francisco
Directional Antennas
If there is no mounting solution to install the access point below 26 feet (8 meters), or where ceilings are replaced by the
stars and the sky (outdoors), or if directional coverage is needed it is recommend to use directional antennas. When
selecting a directional antenna, you should compare the horizontal/vertical beam-width and gain of the antenna

When using directional antennas on a ceiling mounted access point, direct the antenna pointing straight down. When
using directional antennas on a wall mounted access point, tilt the antenna at an angle to the ground. Further tilting a
wall mounted antenna to pointing straight down will limit its range

Cisco Meraki offers 6 types of indoor-rated external antennas (available for MR42E and MR53E):
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Estimate Device Throughput While Meraki APs support the latest technologies and can support maximum data rates defined as per the standards, average device throughput available often …

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Frequently Asked Questions

What is a cisco meraki access point?

Cisco Meraki access points feature a third radio dedicated to continuously and automatically monitoring the surrounding RF environment to maximize Wi-Fi performance even in the highest density deployment.

What is the speed of a meraki ap?

Up to 1.9 Gbps. Cisco Meraki APs provide high capacity wireless in dense, demanding environments. Cisco Meraki APs are custom-designed for cloud management and are built with enhanced CPU and memory capabilities to enable rich services, including Layer 7 application traffic shaping at the network edge.

What is meraki rf optimization?

Cisco Meraki includes powerful, automated RF optimization system delivers high-performance wireless in high density environments and under challenging interference conditions.

What is client balancing in meraki mr?

Client balancing is recommended for high density applications as the feature tries to balance the number of users across APs. The feature is available starting MR25 firmware version and is enabled by default. Cisco Meraki MR access points support a wide array of fast roaming technologies.