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Thomas Nitsche ★
Irene Tejado ★
Adrian Loch
Joerg Widmer
Institute IMDEA Networks
★University Carlos III, Madrid
{firstname.lastname}@imdea.org
Guillermo Bielsa ★
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• Highly directional antennas
Electronically steerable antennas
Allow nodes to focus energy in a certain direction
• Low interference
Neighboring nodes can transmit simultaneously
Very high spatial reuse
• Throughput rates up to roughly 7 gbps
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• Transmission Characteristics
High impact of blockage and free space propagation losses
Highly directional antennas
Communication via reflections to avoid obstacles
• Beam Steering
The ability to steer directional beams become essential
Antenna arrays become smaller the higher the frequency
• Work on Practical 60 GHz Networks
802.11ad Hardware is not available yet
WiGig and WiHD devices are based on very similar mechanism
Learn from first generation devices (black boxes)
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• Beam Pattern Measurement:
We find strong sidelobes as well as imperfect device discovery
techniques
• Frame Level Analysis:
We study frame aggregation as well as the exchange of Data-Ack
frames and frame bursts
• Impact of Reflections:
NLOS communications can achieve 60% throughput through reflections
compared to Line of Sight communications.
• Impact of Interference:
Throughput can decrease up to 75% due to interference impact
• Measurement Equipment:
Vubiq 60GHz Receiver
Agilent MSO-X Oscilloscope
25dBi Gain Horn Antenna
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• Devices Under Test:
Dell D5000 Wireless Dock
• WiGig Protocol
• Manufactured by Wilocity
• 2x8 Element Antenna Array
DVDO Air-3c Wireless HDMI
• WiHD Protocol
• 24 Element Irregular Antenna Array
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Device Discovery Beam Patterns:
Setup:
TX
RX
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Communication Beam Pattern: Communication Pattern: 70º Rotation
Antenna Patterns:
Significant side lobes due to its cost-effective design
Should implement multiple MAC behaviours and choose
the most suitable one
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WiGig Protocol
WiHD Protocol
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5 WiGig WiHD
Clear Data-Ack
Exchange
Yes No
Channel Sensing Yes No
Frame Bursts 2 ms Burst with
Beaconing
No, Periodic
Beacons
Range:
Varies significantly over time
even in the same setup
Should adjust transmit power
to control interference
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Data Aggregation
Aggregation translates into longer frames
Aggregation improves throughput but worsens delay
Multilpe users scenarios worsens delay even more
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Data Aggregation with TCP Iperf Traffic in WiGig Devices
80
60
40
20
100
Lo
ng
fra
me
s [%
]
0
9.7
kbps
40 kbp
s
171
mbp
s
183
mbp
s
372
mbp
s
601
mbp
s
806
mbp
s
831
mbp
s
930
mbp
s
934
mbp
s
TCP Throughput
Aggregation:
Provides much larger gains at
60GHz than at <6GHz
Should depend on how many
nodes share the medium
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Positive Reflection:
Received Power:
LaptopDock
Reflecting wall
2 m0.5 m
1 m
-8
-6
-4
-2
0
30
210
60
240
90
270
120
300
150
330
180 0
Received Signal Power [dB]
Laptop
Line-of-sightblockage
Energy arrives via reflection
Throughput still 60%
compared to direct path
Increase spatial reuse
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Negative Reflection:
Interference Results:
TC
P T
hro
ug
hp
ut
(mb
ps)
600
700
800
900
1000 20 40 60 80 120Time (s)
WiHD on WiHD off
1.5
m1.9 m
WiHDTX
WiHDRX
0.7
m
0.2
m
Blo
cka
ge
Dock
Laptop
ReflectorBlockage
Blockage
elements
prevent
direct in-
terference
from side
lobes of
the WiHD
transmitter
Should extend
geometrical approach
to include two signal
reflectors
Blockage elements
prevent direct
interference from
side lobes of the
WiHD transmitter
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• What have we done?
We have presented an in-depth analysis of consumer-grade off-the-shelf
60GHz systems
We have quantified the impact of their cost-effective designs
• Some common assumptions hold:
Data Aggregation
• Other assumptions become critical:
Beam Patterns
Reflections and Interference
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Contact info:
Guillermo Bielsa
IMDEA Networks Institute
Carlos III University, Madrid
