Top 10 Wi-Fi issues and challenges experienced in enterprises, hospitals, universities...This presentation developed by 7signal founder Veli-Pekka Ketonen, will help you look in the right places on your WLAN so that you can enhance Wi-Fi performance, which improves everyone's productivity. 7signal provides a Wi-Fi performance management system that proactively monitors and measures performance. It also provides analysis and Wi-Fi analytics as well as recommendations for improving the Wi-Fi experience for end users. You can read more about this at http://www.7signal.com/products/sapphire-platform-overview/

1. The key challenges with WLAN technology
Top Ten WLAN Challenges
Opportunities to Improve
Veli-Pekka Ketonen, CTO, 7signal
! Based on Veli-Pekka Ketonen’s presentation
! in May 2013 IEEE802.11HEW Study Group
Date: 2013-06-20

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The key challenges with WLAN technology
In Wi-Fi / WLAN deployments, the quality of the user
experience faces challenges
2 Veli-Pekka Ketonen
• Users are demanding better Wi-Fi
• Users want to Bring Their Own Device
• Mobile workers wants access anytime,
from any place, and with any device

3. 3
The key challenges with WLAN technology
Trying to achieve high maximum performance does
not always translate to a sufficient user experience*
• Capacity, range and end user experienced quality do not meet user needs
• EX: from University. Network configuration has greater impact than network vendor
• * = these are hourly average values from an area of multiple APs/SSID over a week time
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4. 4
The key challenges with WLAN technology
1. Too aggressive rate control, average retries often
exceed 50% (1/2)
• With 802.11n products, regularly
30-50% of packets require at least
one retry. Often even more.
Too high rate selected
A lot of retries,
multiplied by MIMO-X factor
High utilization
Lower SNR
More radio retries,
up to 7 times/packet
No air time & lost packets
Capacity and TCP throughput
collapse
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5. 5
The key challenges with WLAN technology
1. Too aggressive rate control, less aggressive has been proven
better (2/2)
• Individual network behavior also impacts
all other nearby networks
• 802.11ac has much more demanding
requirements than 802.11n
• Suggestions:
• Use less aggressive rate control
• Make rate control dynamic, adjusting
based on observed radio conditions (like
continuous Bluetooth)
• 802.11 to specify proper rate control
schemes, instead of leaving this to
vendors
RX-level during this part of the route: -70 – -88 dBm
Original link adaptation
Optimized link adaptation
-> Reason for improvement:
•Using more MCS-8 instead of MCS-9
RX-level
RX-level
Past findings from Nokia Networks
EDGE link adaptation (Public, Ref [1])
Throughput
Throughput
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6. 6
The key challenges with WLAN technology
2. Automated channel control algorithms
clearly need improvement
• Automated features, like
channel selection do not
work properly
• Continuous channel
hopping in the whole
network and no stable
state
• Impacts to surrounding
networks
• Suggestion:
• 802.11 to specify more in
more detail requirements
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7. 7
The key challenges with WLAN technology
3. Currently available radio settings are not
utilized since their impacts are not understood
• Radio should more accurately and
dynamically operate its settings, like
– Data rates; supported, default, control
– Management/control traffic data rates,
– Fragmentation process, MTU
– QoS
– Ack/block ack schemes usage
– Long/short pre-amble configuration
– RTS/CTS process
– Supported 802.11 standards
– Minimum limit for probe response
– Load balancing, etc
• Suggestions
– Performance management practices
– Automated operation
– 802.11 to specify in more detail
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8. 8
The key challenges with WLAN technology
4. Interference due to lack of channel coordination
and Bluetooth devices
• Channel plans are almost random in
public areas
– Resulting packet loss, jitter
• Proper radio operation in the mid-term
still requires significantly better channel
plans
• Suggestions
– Better, proven automated algorithms for
channel negotiation
– Cloud based control
– Regulation for allowed channels
– Better industry defaults
– Adhoc channel selection limited/guided
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9. 9
The key challenges with WLAN technology
5. Too dense beacon loads air unnecessarily
• In practice 100ms used globally with
1 Mbit/s as mandatory rate in
consumer grade APs. This congests
air significantly everywhere
• In 100ms, a person walking full
speed moves ~10 inches (~ 25cm).
Is this dense beaconing necessary?
• Suggestions
• Define default beacon intervals longer, ~300ms
• Dynamic/adaptive beaconing, beacon interval automatically dependent on the
observed time between roaming.
• Consider adding few % variance to beacon intervals to avoid continuously repeating
collisions (compare to spread spectrum CPU clocking for EMI reduction)
• Consider impact to power save functionality
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10. 10
The key challenges with WLAN technology
6. Mobile networks interfere 2.4 GHz band WLANs
through 3rd harmonic distortion
• When cellular network indoor antennas are near (30ft/10m) to WLAN APs and/or
clients, they may saturate the receiver with off band signals and receiver generates
distortion product that lands in the 2.4 GHz band
• Suggestion
– Add mandatory RF band-pass filtering to WLAN radios
– Receiver blocking test to FCC approval
2.4 GHz2.3 GHz2.2 GHz 2.5 GHz 2.6 GHz2.1 GHz2.0 GHz1.9 GHz1.8 GHz1.7 GHz
DCS-1800
(EUR, US)
PCS-1900 (EUR)
UMTS-1900 (US)
UMTS-2100 (EUR)
UMTS-1700 (US)
Distance appr. 300MHz
=> Harmonic distortion
lands at 300MHz
distance from source
WLAN
WLAN
signal
High power
mobile base
station signal
High power
mobile base
station signal
Ghost
signal
(noise)
=> Signal-to-noise ratio
degrades in WLAN receiver
and data transfer suffers
Verified to happen in
live network
conditions
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11. 11
The key challenges with WLAN technology
7. Support for legacy devices (802.11b/a)
seriously degrades benefits of new standards
• Protection mode is “contagious” and
highly inefficient
• Benefits of new standards are limited if
legacy devices are overprotected.
Important especially in consumer grade
equipment.
• Suggestions
– Better industry defaults
• 802.11b not supported
• 802.11a not supported
– Improvements to protection mode
– Prevent/limit protection mode spreading
with required minimum signal levels
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12. 12
The key challenges with WLAN technology
8. Lack of interoperability may take down entire
network performance
• Introduction of new radio devices
increases average retry rates to
about 70%. Max network capacity
came down at least 50%
• Suggestions
– More exact requirements needed
for client-AP interoperability
– Live network performance
management capabilities need to
improve. All scenarios cannot ever
be tested upfront.
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13. 13
The key challenges with WLAN technology
9. Modest access point antenna solutions
• Omni-antennas with significant vertical coverage are widely used
• RF energy goes where it should not go and antennas try to receive it
from directions where there are no clients
• Lacking antenna sophistication
– More gain towards users would benefit uplink quality
– Lack of antenna directivity creates more interference
• Suggestions
– Down-tilt beam patterns
• Fixed, “normal” antennas
• Electrically adjustable, like in mobile networks
– Wider use of beam steering
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14. 14
The key challenges with WLAN technology
10. Performance Management is completely missing
• With WLAN networks, commonly accepted fact is:
• “It is not necessary to continuously know what kind of service end users get from the network.
• If we manage to make it work once, there is no need continuously look at performance. It
• will take care of itself automatically. We will trouble shoot when end users complain.”
• This approach fundamentally prevents WLAN becoming a reliable media
• Mobile operators/telecom industry are used to manage networks based on
Meaningful Key Performance Indicators, KPIs, that accurately indicate and
predict User Experience (L1-L7) in the network. These are covered also in
standards. This is a good practice that should be brought to WLAN
• Beyond technology providing the required solutions, data and services,
even bigger change is required in attitudes.
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15. 15
The key challenges with WLAN technology
2-10x improvements can be achieved
Results: Controller Automation vs First Manual Optimization Round
• University campus, dense WLAN network
• 2.4 GHz downlink throughput improvement! ! ! Improvement
– Area 1 ! ! 7Mbit/s vrs. 25Mbit/s ! ! ! ! (+250%)
– Area 2 ! ! 5Mbit/s vrs. 15Mbit/s ! ! ! ! (+200%)
– Area 3 ! ! 8Mbit/s vrs. 16Mbit/s ! ! ! ! (+100%)
!
• 2.4 GHz uplink throughput improvement
– Area 1 ! ! 7Mbit/s vrs. 20Mbit/s ! ! ! ! (+180%)
– Area 2 ! ! 10Mbit/s vrs. 25Mbit/s ! ! ! (+150%)
– Area 3 ! ! 12Mbit/s vrs. 20Mbit/s ! ! ! (+65%)
• 2.4 GHz downlink Voice Quality (MOS grade, max 4.0) improvement
– Area 1 ! ! 2.6Mbit/s vrs. 3.5Mbit/s ! ! ! (+0.9 MOS)
– Area 2 ! ! 2.9Mbit/s vrs. 3.8Mbit/s ! ! ! (+0.9 MOS)
– Area 3 ! ! 2.5Mbit/s vrs. 3.5Mbit/s ! ! ! (+1.0 MOS)
• 2.4 GHz uplink Voice Quality (MOS grade, max 4.0) improvement
– Area 1 ! ! 3.5Mbit/s vrs. 3.8Mbit/s ! ! ! (+0.3 MOS)
– Area 2 ! ! 3.5Mbit/s vrs. 3.9Mbit/s ! ! ! (+0.4 MOS)
– Area 3 ! ! 2.5Mbit/s vrs. 3.5Mbit/s ! ! ! (+1.0 MOS)
• 2.4 GHz jitter daily averages before vrs. after
– Area 1! ! 9% vrs. 1% ! ! ! ! ! (- 89%)
– Area 2 ! ! 9% vrs. <<1%
! ! ! ! ! (> -90%)
– Area 3! ! 7% vrs. 1% ! ! ! ! ! (-85%)
• Hourly minimum measured downlink throughput values increase 10X
– Area1, Area 3! ! 0.2 Mbit/s vrs. 2.5 Mbit/s! (~1100%)
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16. Thank You For Watching
www.7signal.com
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