1. Monterey: Update of Proposed Over the Air Test Methodology
Jan 2005
doc.: IEEE /1622r0
Jan 2005
Monterey: Update of Proposed Over the Air Test Methodology
Date:
Authors:
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Kobayashi, Trachewsky, Victor, Broadcom Corp
Kobayashi, Trachewsky, Victor, Broadcom Corp

2. Jan 2005
doc.: IEEE /1622r0
Jan 2005
Abstract
An update on progress made in the area presented in /1476r0, “A Proposed Open Air Test Methodology”
Basic updates are:
Demonstration of repeatability in two different setups (one screenroom located on one floor to another located on a different floor
Show ability to run test in different frequency bands
Kobayashi, Trachewsky, Victor, Broadcom Corp
Kobayashi, Trachewsky, Victor, Broadcom Corp

3. Agenda Objective Background Goals Block Diagram of setup
Jan 2005
doc.: IEEE /1622r0
Jan 2005
Agenda
Objective
Background
Goals
Block Diagram of setup
Picture of setup
Methodology
Old and NEW Test results
Recommendations
Kobayashi, Trachewsky, Victor, Broadcom Corp
Kobayashi, Trachewsky, Victor, Broadcom Corp

4. Objective From PAR and 5 criteria:
Jan 2005
Objective
From PAR and 5 criteria:
Scope: The scope of T is to provide a set of performance metrics, measurement methodologies, and test conditions to enable measuring and predicting the performance of WLAN devices and networks at the component and application level. (emphasis added)
Purpose: The purpose of T is to enable testing, comparison, and deployment planning of WLAN devices based on a common and accepted set of performance metrics, measurement methodologies and test conditions.
Kobayashi, Trachewsky, Victor, Broadcom Corp

5. Jan 2005
Background
The objective of TGT is to come up with a repeatable measurement methodology and to provide
set of metrics
measurement methodologies
test conditions
to enable measuring and predicting
Kobayashi, Trachewsky, Victor, Broadcom Corp

6. Jan 2005
Goals
Propose a controlled open air environment to help achieve the goals and objective of TGT
Allows for complete system evaluation including antenna and effects of all components of DUT
Kobayashi, Trachewsky, Victor, Broadcom Corp

7. Controlled Open Air Test
Jan 2005
Controlled Open Air Test
REF
Open Air
Channel
DUT platform
channel
DUT
Open air channel can be broken into two components
The open air channel by itself
The DUT platform channel
Create an environment where open air channel is virtually flat
reduce multipath channel response
System Under Test (SUT) * =
REF
Open Air
Channel
DUT
DUT platform
channel
System Under Test (SUT) * =
Kobayashi, Trachewsky, Victor, Broadcom Corp

8. Jan 2005
Overview Methodology
Utilize setup that severely reduces any interference from outside sources
Screen room
Use a directional antenna and RF absorbent material to reduce multipath effects
Take a channel measurement of the Open Air with no device present but place antenna in same position as where receive antenna would be in free space
Utilize this measured free space channel loss to determine amount of received power as seen by the DUT
Measure transmitted power out to cabled portion add additional free space loss to determine rx channel power level
Place DUT in place such that rx antenna is exactly in the place that was expected by step above
Kobayashi, Trachewsky, Victor, Broadcom Corp

9. Block Diagram Open Air Calibration
Jan 2005
Block Diagram Open Air Calibration
RF shielded screenroom
Main beam pattern of tx antenna pointed toward open end of RF enclosure to minimize multi-path channel effects
Keeps channel frequency response flat
Directional antenna focuses the majority of energy in a particular direction
Rx antenna is in the far field of the tx antenna
Amplifier puts received signal within rx sensitivity of network analyzer
Collect channel response to determine calibration
Inner Walls lined with
RF absorbent material
calibrated antenna
directional antenna
AMP
Network
Analyzer
Kobayashi, Trachewsky, Victor, Broadcom Corp

10. Block Diagram Open Air Test
Jan 2005
Block Diagram Open Air Test
RF shielded screenroom
Use power meter to measure tx power
Variable attenuator creates additional path loss for determining path loss sensitivity
Inner Walls lined with
RF absorbent material
DUT
directional antenna
REF
Variable
Attenuator
Power meter
directional coupler
Kobayashi, Trachewsky, Victor, Broadcom Corp

11. Jan 2005
Picture of setup
Picture shows main components of items inside of the RF shielded enclosure
Items outside of enclosure are not shown
RF shielded screenroom
Inner Walls lined with
RF absorbent material
DUT
directional antenna
Kobayashi, Trachewsky, Victor, Broadcom Corp

12. Jan 2005
Precision
Open air calibration measurements, requires precise placement (x,y,z) of the calibrated antenna and the actual DUT antenna.
Location of the RX calibrated antenna is key to a good measurement
Note the RX calibrated antenna can be a simple dipole. There is no need for a high-gain antenna like that used in the TX reference
Items utilized during all measurements need to be placed precisely in the same locations in all measurements
TX directional antenna needs to be in same location
Kobayashi, Trachewsky, Victor, Broadcom Corp

13. Jan 2005
Results
First results are provided as a reference to results from previous presentation
First plot in this series shows conducted results
Second plot shows initial measurements made over the air
Second set of results shows
Result of moving from one screenroom on one floor to another
Similar results were achieved as compared to runs shown in previous presentation
Repeatability of this methodology is shown
Third set of results show initial work in the 5.7Ghz band
Second plot shows some initial measurements made over the air
Kobayashi, Trachewsky, Victor, Broadcom Corp

14. Product 2 PER Channel 1-13 conducted
Jan 2005
Product 2 PER Channel 1-13 conducted
Controlled experiment running conducted
Kobayashi, Trachewsky, Victor, Broadcom Corp

15. PER Channel 13 DUT channel with open air losses calibrated out
Jan 2005
PER Channel 13 DUT channel with open air losses calibrated out
Note that after channel effects of air and DUT platform are calibrated out the curves line up similar to conducted results of previous slide
Kobayashi, Trachewsky, Victor, Broadcom Corp

16. PER Channel 1-9 DUT channel with open air losses calibrated out
Jan 2005
PER Channel 1-9 DUT channel with open air losses calibrated out
Note that these results line up closely with results shown in previous 2 slides
Same Product 2 was used in similar test platform in a different screenroom
Kobayashi, Trachewsky, Victor, Broadcom Corp

17. Conducted PER results on channel centered at 5765Mhz
Jan 2005
Conducted PER results on channel centered at 5765Mhz
Controlled experiment as basis
Kobayashi, Trachewsky, Victor, Broadcom Corp

18. Jan 2005
PER results on channel centered at 5765Mhz with open air losses calibrated out
Note that these results line up with results shown in previous slide
Kobayashi, Trachewsky, Victor, Broadcom Corp

19. Issues to be Considered
Jan 2005
doc.: IEEE /1622r0
Jan 2005
Issues to be Considered
Requires a very accurate positioner
Requires knowledge of the exact location of the antenna(s) in the DUT (sometimes enclosed in the chassis)
Do not currently have a good proposed technique for testing diversity systems (TBD)
Have not yet checked that the procedure works at all incident azimuth angles
Do not have solution to run the test easily over a variety of elevation angles
The resulting RF channel isn’t completely flat; so, while we are calibrating the rx power at a point in space, we really want to calibrate capacity (integral of the logarithm of SNR at high SNR)
Kobayashi, Trachewsky, Victor, Broadcom Corp
Kobayashi, Trachewsky, Victor, Broadcom Corp

20. Jan 2005
Recommendation
TGT should continue to explore this methodology (as alluded to in slide 7) for doing full system characterization via Open Air Testing
Kobayashi, Trachewsky, Victor, Broadcom Corp