Wireless Testing with octoBox - octoScope · attenuator RF isolation box USB Feed- ... filter...
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Wireless Testing with octoBox By Fanny Mlinarsky President, octoScope September 2012
Transcript of Wireless Testing with octoBox - octoScope · attenuator RF isolation box USB Feed- ... filter...
Wireless Testing
with octoBox
By Fanny Mlinarsky
President, octoScope
September 2012
www.octoscope.com
Basic Radio Performance Tests
• RX sensitivity
• TX spectrum, EVM
• Range
• Adaptive Modulation
• Roaming behavior
• Performance in the
presence of noise and
interference
Noise/interference generator
DUT = device under test EVM = error vector magnitude
RF combiner
Variable RF attenuator
Master
DUT
Isolation box
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www.octoscope.com www.octoscope.com
Controlled Environment Test
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Ethernet
Programmable attenuator
RF isolation box
USB
Feed-through filters
Distance and motion emulated using a programmable attenuator to model path loss (flat fading) or a channel emulator to model multipath and Doppler fading
Signal coupled via cabling (conducted) or over the air (OTA)
Master and DUT are isolated from each other to achieve wide dynamic range of the measurement by eliminating crosstalk
octoBox-26L small anechoic chamber
www.octoscope.com
Controlled
Environment
Measurement
Example
Noise, interference and Master to DUT coupling must be well below intended signal level at DUT for metrics such as rate/MCS adaptation or roaming performance
Wi-Fi DUT’s data rate
adaptation behavior vs. RSSI
all the way down to the RSSI
level of -95 dBm.
Measured DUT RSSI is less
than
-95 dBm. This means
Master to DUT coupling of
less than -100 dBm.
802.11b (DSSS-CCK) – 1, 2, 5.5, 11 Mbps; 2.4 GHz 802.11a (OFDM) – 6, 9, 12, 18, 24, 36, 48, 54 Mbps; 5 GHz 802.11g – both 11b and 11a rates; 2.4 GHz 802.11n – up to 600 Mbps; 2.4 and 5 GHz
Data rate adaptation vs.
RSSI
MCS = modulation coding scheme DUT = device under test
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octoBox Roaming Test Configuration
USB
Controller or
Ethernet switch
Client/bridge
under test
Traffic
source/sink
1:4 RF combiner
octoBox-26L Stackable
Traffic
source/sink
AP2
AP1
octoBox-26L Stackable
RF combiner
and attenuators
Feed-through
Ethernet filters
RF port
ATTEN1
Eth
ern
et
Spare combiner ports for
connecting a sniffer
ATTEN2
www.octoscope.com
octoBox Roaming Test Script
• Test script running on the traffic source/sink PCs
• Configuration settings:
Distance or dB loss between AP1 and AP2
Emulated velocity of client
Number of roams
• Output:
Roaming time distribution plot
Summary report including the time of each roam, minimum and maximum time
• Functionality
Script controls RF attenuators ATTEN1 and ATTEN2 with configurable emulated
speed of motion of the client between AP1 and AP1
The client ‘motion’ is forced to happen back and forth between AP1 and AP2 for
a programmed number of times (e.g. 100 times)
Histogram of roaming times is plotted at the end of the test
Roaming time
# o
f o
ccu
rre
nce
s
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Roaming Test Results - Example
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3.16 sec
9.04 sec
6.63 sec
0
5
10
15
20
25
30
35
40
45
50
0 2 4 6 8 10 12 14
dB
ab
ove
no
ise
Seconds
RSSI 61:30
RSSI 5a:f0
ping requests
ping replies
deassociate
deauthenticate
authenticate
assoc req-resp
Last ping response: 3.16 sec
Association: 6.63 sec
First ping response: 9.04 sec
Wireshark
Sniffer
AirPcap Nx
USB dongles
www.octoscope.com
Wireless Mesh Testing
Wireless Mesh Metrics
• Self-healing, self-forming
• Throughput, QoS vs. hops
• Throughput, QoS vs. range
• Routing efficiency
• Dealing with interference
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Multi-radio mesh nodes can communicate on
different channels with multiple neighbors
simultaneously.
In a single-channel mesh throughput is cut in half
at each hop.
www.octoscope.com
Wireless Mesh Testing in a Controlled Environment
• octoBox technology provides industry-first controlled laboratory based
motion and channel impairment emulation to enable expedient development
and demonstration of mesh system capabilities.
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Maximize attenuators to force auto-re-
routing of traffic flow to test self-healing
Fixed attenuators to set traffic
flow via one branch or another
to test self configuration
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Nodes are in octoBox
isolation chambers
octoBox quadStack
isolation enclosures
with built-in RF
combiners and
attenuators
RF splitters used to direct
signal to multiple
neighboring devices
www.octoscope.com www.octoscope.com
Test Configuration 12
octoBox quadStack
Console
Ethernet
www.octoscope.com
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Bulkhead
SMA RF ports
Protective
shroud
Mounting for optional
RF combiner-
attenuator module
octoBox Stackable Platform
RF splitter Programmable
attenuators Fixed attenuators
www.octoscope.com
Wireless Mesh Testing - Example
RF Combiner RF Switch
RF Attenuator
Antenna
octoBox upper chamber
#1 octoBox lower chamber
#3
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bc:77:37:ab:33:5d
PC in open air
#2
bc:77:37:ab:33:5d
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octoBox
Console
US
B c
able
goi
ng th
roug
h da
ta fi
lter
to c
ontr
ol P
ingb
last
er r
unni
ng o
n #
3
Ping request -
response traffic
#2
#3
#1
#1
#2
#3
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Delay Through Mesh
~ 2 msec delay
One hop
Seconds
Ping round trip delay (ms)
~ 12 msec delay with
bursts of long delays
(>1 seconds)
Zero hops
bc:77:37:ab:33:5d
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bc:77:37:ab:33:5d
94:39:e5:01:3d:62 94:39:e5:01:68:ed
BATMAN = better approach to mobile
ad hoc networking
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Connected Car DSRC Test
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DSRC = direct short range communications
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Connected Car Testbed – Large Intersection
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Emulate groups of connected vehicles traveling over a busy highway interchange
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Group of Radios Inside Each octoBox …
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Ethernet hub
Absorptive foam to provide OTA
isolation, preventing from over-
driving the RX
Test antennas
Bulkhead
SMA RF port
…
8 SMA ports total (1 for local
RF combiner; up to 7
connections from other boxes)
Up to
24
DUTs
Ethernet filter
Eth
erne
t
OTA = over the air
www.octoscope.com www.octoscope.com
System Interconnects 19
Up to 24 radios
Up to 24 radios
Up to 24 radios
Up to 24 radios
Up to 24 radios
Up to 24 radios
Up to 24 radios
Up to 24 radios
Sta
ck 1
Sta
ck 2
…
…
2 or more stacks can be positioned to face each other
with cabling neatly connected in the middle
Ethernet
Distributed, expandable matrix of
programmable RF attenuators and combiners
DSRC testbed
emulates motion of
groups of cars with
respect to other groups
www.octoscope.com
Example: 3” x 5” x 1” DSRC DUT
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DUTs
Layers of absorptive foam (not shown) separating DUTs
horizontally and vertically providing 10 dB of isolation per layer
Ethernet hub Test antennas
DSRC = direct short range communications
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octoBox Internal Details
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Layers of absorptive foam Fan intake DUTs
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octoBox Internal Details
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8 SMA barrel connectors feed the antennas Fan outflow
Patch antennas
Radios under test
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Wireless Channel Emulator
Controlled
programmable
channel conditions
Multipath
Doppler
Noise
Channel Emulator Used to emulate multipath and Doppler fading in order to test radio performance and adaptive behavior
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www.octoscope.com
Wireless Channel
Per path angular spread
Composite angular spread
Composite angular spread
Multipath clusters
Multipath and Doppler fading in the channel
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Wireless Channel
• Frequency and time variable
wireless channel
• Multipath creates a sum of multiple
versions of the TX signal at the RX
Ch
an
nel
Qu
ality
Frequency-variable channel appears flat over the narrow band of an OFDM subcarrier.
Frequency
… …
OFDM = orthogonal frequency division multiplexing
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MIMO Systems
MIMO systems are typically described as NxM, where N is the
number of transmitters and M is the number of receivers.
TX
RX
TX
RX
2x2 MIMO radio
channel
TX
RX
TX
RX
2x2 radio 2x2 radio
MIMO = multiple input multiple output
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www.octoscope.com
octoBox Stackable – Ease of Interconnections
• Left and right hinging
units help make RF
interconnections neat
and orderly
octoBox-L has its door
hinge on the left
octoBox-R has its door
hinge on the right
• Optional mountable RF
modules (attenuators,
combiners, etc.) create
solid and well-
constructed RF
testbeds
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octoBox-26L
quadStack
octoBox-26R
quadStack
www.octoscope.com
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Bulkhead
SMA RF ports
Protective
shroud
Studs provided on
each box for
mounting an optional
RF combiner-
attenuator module
Features
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Features
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Mounting
rail system and
DUT shelf
Inside
surfaces
covered with
absorber
Dual latching
mechanism for
uniform door seal
Feed-through
filtered high speed
data connectors
Fan
Test antenna
Dual gasketing for
complete isolation
www.octoscope.com
Conducted vs. OTA
Conducted OTA
Antennas are included in the test and
small devices with printed antennas can
be measured through antennas, but the
test set up requires controlled conditions
to support 3D OTA metrics. Signal
power and integrity at test antennas
varies with DUT orientation, reflections
and interference.
Antenna field
All energy
couples into
the coax C
oaxi
al c
ablin
g
OTA = over the air DUT = device under test
To antenna port
Repeatable measurements, but antennas are not
included in the test; impractical to disconnect
antennas for measurement in devices like
smartphones and consumer electronics
Energy
propagates in
3 dimensions
OTA = over the air DUT = device under test
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www.octoscope.com
RF Anechoic Chamber for OTA
coupling
• Isolation
Prevents errors caused by noise and by crosstalk
between Master and DUT
• Absorption
Eliminates standing waves that cause nulls in the
signal
Nulls result in high power gradients vs. antenna
position
Absorptive foam with layers of gradient
impedance dampens signal fluctuations
by attenuating standing waves
Standing waves create fluctuations in the signal
Cross-section
view of
octoBox
Stackable
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www.octoscope.com
High Speed Data Filter
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Flexible filter architecture allows
any combination of feed-through
Ethernet, USB or DC power
filters to be configured
Outside-facing connectors Inside-facing
connectors
New patent-pending
magnetic feed-through
filter design
AC power
connection
Fan
Quad high
speed data
filter module
www.octoscope.com
Isolation and Filtering
• Creating controlled RF conditions with
good isolation is challenging,
particularly for large-scale RF test
setups, such as mesh configurations.
Short wavelength high frequency signals
couple via many paths, including copper
cabling, poor/aging gasketing, ground loops,
etc. Sources of interference may be difficult
to locate in a multi-box setup.
• Isolation considerations
Isolation should be measured and specified
with a fully cabled test setup.
All copper cabling, including Ethernet and
power cabling, will act as antennas
contributing to RF coupling among enclosures
and thus limiting attenuation range setting.
Upfront investment into high grade
enclosures with good data and power feed-
through filtering and absorptive foam can
save 1-2 months of chasing uncontrolled
paths of interference in the test setup.
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www.octoscope.com
Competitive Analysis
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octoBox-L/R Ramsey STE4450
Ethernet filter performance (see next slide) >80 dB rejection up to 6 GHz Likely < 40 dB rejection *
Plating for improved seals and E&M immunity Y
Dual latch for even door seal Y
Dual door gasketing for better isolation at high frequencies Y
Gasketing for connector panel Y
Plastic mounting rails for mounting modules , shelves, etc. Y
Extensible to MIMO configurations Y
Gradient absorber supporting over-the-air signal coupling Y
Absorber damping >20 dB Only 4 dB **
Stackable; no rack required Y
Casters for easy moving Y
* Specs for filtered connectors similar to the ones used in Ramsey enclosures are available online. These show <40 dB
of attenuation up to 1 GHz with no specs beyond 1 GHz. We need specs on isolation up to 6 GHz at Wi-Fi frequencies.
** Measurement data available upon request
www.octoscope.com
octoBox-26 Specifications Feature Specification Notes
AC power entry module IEC-320 C14 inlet connector
120/240VAC 50/60Hz
6A 5x20mm fuse
With built-in RF filter for isolation
Cooling 80mm square axial fan
4" honeycomb filters over inlet and
outlet for isolation
Honeycomb filters provide RF isolation
on fan inlet and outlet
Filtered high speed data connections gigEthernet (with PoE), USB or DC
power ports
Standard configuration: dual
Optional configuration: quad
RF ports 8 RF barrel connector ports Standard configuration: SMA
Optional configuration: N-connectors
Isolation >80 dB, fully cabled setup, up to 6 GHz
Absorption >20 dB absorption 1.3 GHz to 40 GHz
Outside dimensions (single box) 18”H x 26.35”W x 25.2”D
Inside dimensions (single box) 13.35”H x 19.35”W x 13.35”D
Outside dimensions (quadStack) 6’6”H x 26.36”W x 25.2”D
Base: 34”W x 28.5”D
Base is wider for stability of the stack
Box material 16 gauge (0.0598" thick) steel Supports up to 40 LBS load per box
Weight 80 LBS each box
95 LBS base
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PoE = Power over Ethernet
www.octoscope.com
octoBox Stackable – Feature Summary • Robust stackable design with support for over the air RF signal coupling
• Optional built-in RF combiner-attenuator module
Inside and outside mounting options
• Plastic (RF-transparent) mounting for test fixturing
e.g. shelves, RF combiners, RF attenuators, etc.
• Base with casters for easy moving – with locking breaks
• Cooling
• Power entry module with integrated filter, fuse and switch
• Filtered high-speed data ports
Ethernet or USB
Gigabit Ethernet and PoE support
• Standard configuration
Dual high speed data filter module
8 bulkhead SMA RF ports
• Options
Quad high speed data filter module
8 N-type RF ports
RF combiner-attenuator module
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www.octoscope.com
Contact
+1.978.222.3114
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