IBTUF VIII – AUSTIN, TX
Distributed Antenna Systems for Large Venues
Presented by:
Prabhu Maragathavannan
Principal Engineer- CAR/TN Region
January 15, 2014
PID#
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Agenda
• DAS Zones –Capacity Vs System Performance
 DAS Zones Vs Sectors
 User Throughput expectations
 3D Model and inclined surfaces
 Performance based capacity solution
• Case study : BOA Stadium
 Jumbled PN Issue
• Delay settings
 Significance of Delay settings
 Cause and Effects
 Parameters to be adjusted
• UL attenuation settings for different equipment
 Noise Figure Calculation
 UL attenuation settings examples
• Path imbalance
 Balancing Tool
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DAS Zones- Capacity Vs System Performance
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DAS Zones- Capacity Vs System Performance
Capacity planning based on market share, technology split, simultaneous
users, active connected users and target throughput etc
“X” Number of sectors requested
How do sectors
translate to System
Performance in
stadiums and
arenas?
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DAS Zones- Capacity Vs System Performance
Example: 4 sector configuration
Sector
Boundaries
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DAS Zones- Capacity Vs System Performance
• User experience in the bowl will be different based on where they are seated
Users in this area
get great
Throughput due to
higher modulation
More Sectors
create more
Boundaries with
poor SINR
User gets poor
Throughput in the
sector boundaries
due to bad SINR
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DAS Zones- Capacity Vs System Performance
• Two aspects of the design
 Capacity planning based on market share, technology split, simultaneous users, active
connected users and target throughput etc
 Performance based capacity planning using Target SINR and Noise Figure
calculations
Consider Noise rise due to loading which will affect SINR
 SINR of 10 dB in an empty stadium may be even 2 dB based on the amount of
loading. Need to include the “noise rise due to loading” into calculations
Number of remotes per sector to be considered for noise figure
Even if enough power is available, try to have additional remotes to create zones for
future. We cannot suddenly create additional sectors if we don’t have those in place
Both of these factors go hand in hand and there is a tradeoff between the
two at a point and might have to grow vertically at this point
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DAS Zones- Capacity Vs System Performance
If there are multiple levels, make sure inclination is defined properly and
all sectors are transmitting when generating SINR plots
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DAS Zones- Capacity Vs System Performance
We can see the different tiers of the stadium with the antenna locations
on the 3D view in this example clearly showing the slope and inclination
well defined for propagation modeling
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DAS Zones- Capacity Vs System Performance
The predictions should be based on the inclined surfaces also inside the
bowl. The more accurate the slope and the angle directions are, the
prediction results will be more close to actual scenario
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Case Study: BOA Stadium
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BOA Case study: Voice PN Dominance
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BOA Case Study: EVDO PN Dominance
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BOA Case Study: EVDO PN dominance after
delay compensation
This zone was
down during
testing
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Delay Settings
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Delay Settings
• The eNode B is responsible for maintaining the uplink timing synchronization
for the users.
• In LTE, timing adjustment is performed using the timing-advance(TA)
command, which is transmitted either as part of a random-access response
or as a MAC control element
 When the TA command is transmitted as part of the random access
response, a 11-bit TA command with possible values of
TA=0,1,2,…1282 is used which provides timing adjustment from 0 to
667 uS
 When the UE is already synchronized, only fine timing adjustment is
necessary and is done on MAC control message
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Delay Settings
• Delay compensation is an underrated concept and could cause performance issues
• DAS Systems have an inherent delay, especially the ones with long fiber runs
• They have to be balanced for the sectors and then compensated at the BTS/eNode
B
• Unbalanced delays = PN Offset for CDMA as BTS are time synchronized- will
cause JUMBLED PN issues (EVDO seems to be more sensitive than voice)
• Will affect LTE significantly as each TA granularity is around 0.52us
• New delay compensation parameter GPSAntDel for Motorola equipment (CDMA)
and has been successfully implemented at several venues
• Should be kept in mind while moving zones around and assigning to sectors with
different delays
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Delay settings
Fiber lengths for multiple
remotes to the same
sector should be
balanced for delay
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LTE Delay Compensation
• LTE (Ericsson example)
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Motorola Delay compensation
• Motorola parameter for delay compensation (4812)
Delay
compensation in
nano seconds
Please note this has to be set at a frame level unlike LTE
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Motorola Delay compensation
• Delay compensation for UBS frames
Delay
compensation in
nano seconds
Note the difference
for UBS frames
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UL attenuation settings for different equipment
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Why is Noise Figure important ?
• Where Fn and Gn are the noise factor and available power gain,
respectively, of the n-th stage. Note that both magnitudes are
expressed as ratios, not in decibels.
• The overall noise figure of a radio receiver is primarily established by
the noise figure of its first amplifying stage. Subsequent stages have
a diminishing effect on signal to noise ratio. For this reason, the first
stage amplifier in a receiver is often called the Low Noise
Amplifier(LNA).
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UL Attenuation Settings (Solid Equipment)
Attenuation
at the remote
should be 0
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UL Attenuation Settings (Solid Equipment)
Setting at the
conditioners
are ok
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UL Attenuation Settings (MA Equipment)
Setting at the
conditioners
are ok
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UL Attenuation
UL Attenuation
•
•
In neutral host systems try to keep UL
atten on the DIU trays to have control
Active trays like iPOI are great option but
make sure it is not locked by the other
carrier for neutral host scenarios
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Path Imbalance
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Path Imbalance
• An unbalanced path will allow individual UE’s to generate inter-cell interference at cell
edges which could cause higher receive noise floors.
• Rises in reverse link noise floors at eNodeB receivers will slow uplink throughput
considerably, well before the downlink is affected
• Tool to calculate required UL attenuation
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Thank You!
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