Best Practices in Open Over The Air Testing Best Practices in Open Over The Air Testing 2007 Antenna Systems Conference Denver Colorado 2007 Antenna Systems Conference Denver Colorado Smart Antennas Smarter Connectivity Smart Antennas Smarter Connectivity Inconsistencies in Open over the Air Tests Obtaining Repeatable Consistent and Accurate results in open over the air throughput testing of wireless data connections is often impossible Changes in the environment and multipath fading cause large variations in any real life test Comparing devices that have different antenna systems is even more difficult since multipath affects them differently This presentation demonstrates how it is possible to use multiple tests and statistical methods to eliminate the inconsistencies that plaque Open Over The Air measurements even when comparing devices that have different antenna systems including comparison tests of MIMO devices The solution is based on statistical principles By making a large number of measurements in slightly different locations and orientations of the devices under test it is possible to collect enough data to eliminate the random variations Client Station WLCP Client Station WLCP Multiple throughput tests were performed in each location placing both the Device Under Test DUT and wireless counter part WLCP on a stop motion turntable Both tables turned a given amount 24 or 10 between each measurement and stopped for the duration of the throughput test The 15 or 36 stops cover the full circle on both turntables with tables turning in opposite directions Automatic collection of Data using Turntables Client Station WLCP Access Point DUT Test control system Traffic generation device Traffic analyzer Automatic control of stop motion turn tables Stop motion turntable with controller Stop motion turntable with controller The connection to one or the turntables was wireless but it was not operated during the throughput test Links measured Three AP devices were compared in an Open Over the Air test The throughput of each device was measured over six different links locations in a house where the two turntables were placed Tests at each link location included 15 throughput measurements for each Device Under Test DUT 5 6 41 23 3 Access Point Client Second Floor Access Point Client Second Floor Measured Throughputs in All Tests The only difference between the curves on the graph of each DUT is the precise location and orientation of the DUT and WLCP Results of all measurements The throughput of each device in all locations varies dramatically based on the precise location and orientation of the DUT and the WLCP Throughput Mbits s Throughput of DUT2 Link number Link number Throughput of DUT1 0 15 30 465123 Average of DUT 1 0 15 30 465123 Average of DUT 2 0 15 30 465123 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average of DUT 3 Client Location Throughput of DUT3 Link number 0 15 30 465123 0 15 30 465123 Comparison Results in Different Tests Here is a part of the same data measuring the same six links with exactly the same AP and Client Stations The only differences between the graphs are the precise location and the orientation of the AP and the Client station The results appear inconsistent Throughput Mbits s 0 15 30 465123 Throughputs in orientation 4Throughputs in orientation 4 0 15 30 465123 Throughputs in orientation 3 Throughputs in orientation 3 Link number Link number Link number Link number Link number Link number Throughput Mbits s Throughputs in orientation 5 Throughputs in orientation 5 0 15 30 465123 Throughputs in orientation 9 Throughputs in orientation 9 0 15 30 465123 Throughputs in orientation 10 Throughputs in orientation 1 Throughputs in orientation 10 Throughputs in orientation 1 DUTDUT1 1 DUTDUT2 2 A DUTDUT3 3 Averaging Results of Slightly Different Locations Fortunately we can eliminate the inconsistencies and achieve repeatable results by simply performing several measurements at slightly different locations and orientations of both the DUT and WLCP for each of the links distances and averaging the results for each link Averaging all 15 measurements for each of the six links shown on the previous slide provides more consistent results 0 15 30 465123 Average of DUT 1 Average of DUT 2 Average of DUT 3 Data Average Throughput of all 15 orientations Average Throughput of all 15 orientations Link numberLink number Throughput Mbits s MIMO Tests Links Measured The same MIMO device with two different antenna systems was compared in an Open Over the Air test The throughput of each device was measured over five different links Tests at each link included 36 measurements for each DUT 5 4 3 2 1 Client Station AP MIMO Units All Tests Here are the results of all measurements Again the only difference between the curves on the graph of each DUT is the precise location and orientation of the DUT and WLCP Throughput Mbits s Throughput of DUT2 Link numberLink numberLink numberLink number Throughput of DUT1 Step of