How to Configure Miracast™ Wireless Display

How to Configure Miracast™ Wireless Display
techtip
How to
Configure Miracast
Wireless Display
Implementations
for Maximum
Performance
™
techtip
Are wireless interference and excessive channel use causing frustration
and down time for your wireless users? Do you struggle with Miracast
wireless display connections dropping?
In this white paper we illustrate best practices for troubleshooting
wireless environments and helping various technologies play together
correctly in the same frequencies. We explore the root causes of
these issues and how to solve them. For ScreenBeam wireless display
receivers, proper configuration is key to getting the most powerful and
reliable signal.
A Poor Wireless Environment: Three Common Causes
There are three common causes to the issues organizations experience with their
wireless environments.
Physical design,
improper planning
and excessive
power all can
contribute to a
poor wireless
environment.
1.Physical Design and Infrastructure: The organization’s physical design and
infrastructure may interfere with the wireless signal.
2.Adjacent Channel Interference: Improper channel planning, plus miscellaneous
Wi-Fi and non-Wi-Fi devices, may contribute to adjacent channel interference, also
known as overlapping channel.
3.Transmitting Power: Excessive transmission power may cause high channel
utilization and interfere other wireless connectivity using the same wireless channel.
1. Physical Design and Infrastructure
Understanding the Nature of Radio Frequency Waves
Issue
If an access point (AP) does not receive successful data transmission from a source
device because of distorted radio wave (also known as Network Packet Loss), it will
not respond to the source device. APs are half duplex, meaning they can only send or
receive at any given moment; they cannot do both at once. On a shared medium, multiple
sources all sense the medium for a clear channel, then contend for a period of time to
transmit their packets.
Network packet loss forces a re-transmission attempt from the source device, which
slows the network down.
Background
Radio waves may become distorted by coming in contact with the building’s physical
infrastructure. Some obstacles that radio waves must navigate cause them to lose
power or signal strength prior to arriving at the receiving device. Figure 1 illustrates an
environment in which radio waves may lose their strength.
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How to Configure Miracast Wireless Display Implementations for Maximum Performance
WALL
Reflected
Diffracted
Direct-attenuated
WALL
Figure 1: How radio waves may lose their strength
Radio waves may:
Attenuate: When wireless signals move through a medium such as walls, brick or
concrete, they gradually lose intensity.
Diffract: When a wave encounters an obstacle, it bends around the corner of the
obstacle or aperture, into the region of the obstacle’s geometrical shadow.
Reflect: Signal power may be reflected back to its origin, rather than being carried all
the way to its destination.
The placement of
the ScreenBeam
wireless display
receiver is critical to
its performance.
Scatter: Upon encountering a convex structure, such as a glass window, door or water
cooler, the waves shatter into little bits and scatter in various directions.
The placement of the ScreenBeam wireless display receiver is critical to its performance.
Take into consideration that radio frequency (RF) waves are omnidirectional, meaning
when radio waves leave the antenna, they travel in all different directions.
Figure 2 illustrates what an omnidirectional antenna looks like when radio waves leave an
antenna. Anything directly below the antenna is a dead zone, and anything below the “x”
area is reflected upwards. Placing a ScreenBeam receiver on a metal surface will cause
the radio waves to reflect off of the metal surface and propagate upwards, instead of in
their intended outward direction.
Figure 2: Omni-directional radio waves
Solution
Best practices to mitigate the attenuation, diffraction, reflection and scattering of radio
frequency waves and to return the strongest RF signal are to:
1.Establish a good line of sight from the client system transmitting to the ScreenBeam.
2.Conduct a site survey; examine each room for anything that may cause RF wave
deflection or damage.
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2. Adjacent Channel Interference
Improper Wireless Planning
Issue
The 2.4 GHz
wireless spectrum is
limited to only three
non-overlapping
20MHz channels.
Most enterprise-grade wireless APs are set to use dual-band with auto channel and/or
auto transmit, which gives client systems the opportunity to choose the best possible
Wi-Fi connection at any given time, anywhere in the building.
In the 5 GHz spectrum, there’s no 20 MHz channel partial overlap. The 2.4 GHz wireless
spectrum however, is limited to only three non-overlapping 20 MHz channels: 1, 6, and
11 (within the USA and the majority of the world).
Figure 3 below shows channels 1, 6, and 11 highlighted in green, non-overlapping
when set respectively. Channel 3, if enabled, can overlap with both channels 1 and 6,
which introduces adjacent channel interference.
1
2
3
4
5
6
7
8
9
10
11
Channel
Figure 3: 2.4 GHz channels
When communications signals are competing with each other, the transmissions
become garbled and severely interfere with Miracast wireless display connections. This
adjacent channel interference is the worst type of Wi-Fi interference.
If channel bonding is used in 2.4 GHz to increase the throughput, then it is highly
susceptible to adjacent channel interferences from other 2.4 GHz radios, as seen in
Figure 4.
40 MHz 802.11n Channel
1
2
3
4
5
6
7
8
9
2.402 GHz
Figure 4: Adjacent channel interferences in 40 MHz
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10
11
12
13
14 Channel
2.483 GHz
How to Configure Miracast Wireless Display Implementations for Maximum Performance
Solution
1.Our recommended best practice for constant and reliable connection in these
high-transient environments is for APs to maintain set channels. To achieve this, AP
channels should have good separation from neighboring APs. The Wi-Fi industry
standard recommendation for 2.4 GHz and 5 GHz is that no channels should be next
to each other.
2.Figure 5 illustrates 2.4 GHz channels set at 1, 6 and 11.
Adjacent channel
interference is the
worst type of Wi-Fi
interference
Figure 5: Proper configuration for 2.4 GHz to avoid adjacent channel interference.
Setting the APs to channels 1, 6 and 11 ensures that the channels will not overlap
with each other and cause adjacent interference.
3.Do not enable channel bonding in the 2.4 GHz band.
4.Disable or remove unnecessary third-party Wi-Fi and non-Wi-Fi 2.4 GHz radios (such
as a Bluetooth device) that may attribute to adjacent channel interference.
3. Transmitting Power
Configuring Access Points
Issue
When the radio frequency noise floor raises, it changes the signal-to-noise ratio (SNR),
causing the transmitting power to increase. The cells of the radio frequency footprint
get so large that they bleed into neighboring rooms. Since 2.4 GHz signals propagate
better than 5 GHz, a 2.4 GHz signal with the same amount of transmission power can be
received farther away. Thus, they often cause overlapping coverage cells when multiple
APs reuse the same channels 1, 6, and 11.
Overlapping coverage cells using the same channel can lead to high channel utilization.
When multiple client systems are connected to neighboring APs using similar channels,
two or more client systems transmitting at the same time can result in garbled
transmissions. If there are excessive signal collisions, data would never be transmitted
successfully, and the wireless network would be unusable. This can also severely affect
Miracast wireless display connection and streaming performance.
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Figure 6 below provides an example of potential high utilization for channel 11, indicated
by dark red areas.
Since 2.4 GHz
signals propagate
better than 5 GHz, a
2.4 GHz signal with
the same amount of
transmission power
can be received
farther away.
1
6
11
6
11
1
11
1
6
Figure 6: Overlapping coverage cells using the same channel can lead to high
channel utilization
Solutions
1.Manually set the transmit power for
the 2.4 GHz APs. In the AP’s WLAN
controller, pick a series of four rooms
and manipulate the power so the RF
footprints are not overlapping. Run
a quick site survey with an on-site
technician doing spectrum analysis.
Have the technician determine the
center of each room and take some
readings, then mimic that across the
entire campus.
1
6
11
6
11
1
11
1
6
Figure 7: Reducing transmitting power
mitigates high channel utilization
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2.The similar implementation using
5 GHz should see less of an issue,
since there are more channels
available, and the signal travels less
than 2.4 GHz signals.
36
40
44
48
149
151
153
157
36
Figure 8: 5 GHz implementation has
less channel utilization concern
How to Configure Miracast Wireless Display Implementations for Maximum Performance
Proper Configuration is the Cure
Fine tune your access points with these best practices that make ScreenBeam wireless
display experience more reliable.
Assigning Channel for Miracast session:
Reserve 5 GHz Channel
Per the Wi-Fi Alliance standard, all Miracast receivers—including ScreenBeam—are
designed to operate in Negotiated Group Owner (NGO) mode. In this mode, the client
system is the group owner, and the wireless channel used for Wi-Fi is also used for the
Miracast session. For example, when the client Wi-Fi connects to an AP using channel
6, the Miracast session also operates on channel 6.
This is fine if the wireless infrastructure is properly configured as recommended above.
Not all wireless infrastructures are deployed with proper configuration however, and
2.4 GHz implementation is still a preferred choice for broader coverage. Also, with
more third-party Wi-Fi and non-Wi-Fi host devices operating on 2.4 GHz and being
introduced to an already congested wireless environment, interferences are almost
unavoidable for Miracast sessions.
Actiontec’s latest products, ScreenBeam 750 and ScreenBeam 960, feature the ability
for an organization to designate wireless channel(s) specifically for Miracast sessions.
Instead of sharing the same wireless band and channel as the wireless infrastructure,
an organization with a congested wireless environment can enable ScreenBeam to be
the Wi-Fi-Direct group owner, commonly referred to as an Autonomous Group Owner
(AGO). Thus, the wireless network admin could reserve known-clear 5 GHz channel(s)
for ScreenBeam to operate on, to assure a smooth and reliable Miracast wireless display
experience for end users.
In this mode, the client system wireless adapter has strong Different Channel Mode (DCM)
support, to allow different communication paths on separate wireless channels. If AGO
is considered for your deployment, we recommend that client systems have wireless
adapters with known-good DCM support. To find out if your adapter has known-good
support, go to the ScreenBeam support site at https://actiontec.zendesk.com/hc/en-us/
and search for “DCM adapter”.
The good news is existing ScreenBeam Education 2 product can be updated to the
ScreenBeam 750 software, allowing it to take full advantage of the peer-to-peer (P2P)
channel selection feature.
With more thirdparty Wi-Fi and
non-Wi-Fi host
devices operating
on 2.4 GHz and
being introduced
to an already
congested wireless
environment,
interferences are
almost unavoidable
for Miracast
sessions.
Support
Contact
To continue this
conversation, have
your questions
answered, or discover
how ScreenBeam
can simplify your
conferencing and
presentations, we
want to hear from
you. Contact our tech
support team:
PHONE
1-888-436-0657
EMAIL
[email protected]
actiontec.zendesk.com
WEBSITE
https://actiontec.
zendesk.com/hc/
en-us/requests/new
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IndustryLeader
ScreenBeam wireless display is the only solution that truly enables
commercial deployment of secured and IT manageable wireless display.
ScreenBeam wireless display is the industry standard for benchmarking
and device interoperability, making it the most broadly compatible solution
available. ScreenBeam solutions are used as the validation platform for wireless
display functionality by companies like Microsoft, Intel, and leading PC OEM
and device companies.
Actiontec is Microsoft’s co-engineering partner for wireless display
technologies in Windows. Because of Actiontec’s status as the industry leader,
and our ongoing investment in supporting industry device manufacturers, you
can be assured that you’re deploying the most broadly compatible, feature-rich
wireless display platform.
© 2017 All rights reserved. Actiontec and the Actiontec logo are registered trademarks, and
ScreenBeam is a trademark of Actiontec Electronics, Inc. All other names are properties of
their respective owners. Specifications subject to change without notice. 032317
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