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Measurements of temporal occupancy and a comparison of indoor performance of OFDM vs CCK/DSSS

Measurements of temporal occupancy and a comparison of indoor performance of OFDM vs CCK/DSSS. Authors:. Date: 2016-07-11. Jim Lansford (Qualcomm/CU-Boulder). Abstract. As a class project, students made measurements of:

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Measurements of temporal occupancy and a comparison of indoor performance of OFDM vs CCK/DSSS

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  1. Measurements of temporal occupancy and a comparison of indoor performance of OFDM vs CCK/DSSS Authors: Date: 2016-07-11 Jim Lansford (Qualcomm/CU-Boulder)

  2. Abstract As a class project, students made measurements of: 1) Channel occupancy of WLAN traffic in different environments to assess how much time is spent in each of the data rates and overall protocol efficiency, and 2) Comparison of indoor performance of OFDM vs CCK/DSSS Jim Lansford (Qualcomm/CU-Boulder)

  3. 1) Channel occupancy - Problem Statement Use packet capture and analysis tools to analyze the temporal occupancy, packet type distribution, and data rate distribution of deployed 802.11 systems in the following environments: • High density, unmanaged public retail networks • Managed university network (campus-wide ESS) • Residential unmanaged networks Jim Lansford (Qualcomm/CU-Boulder)

  4. Methodology Most students used Microsoft Network Monitor to capture packets • Has a “monitor mode” to capture packets by scanning across channels (unassociated) • Some students used OmniPeek if they had access Save as a .cap file so Wireshark can analyze Students used Excel to create charts • Some wrote custom scripts to analyze packets Summarize results in reports • Most students only examined 2.4GHz networks, so that is all that will be summarized here Jim Lansford (Qualcomm/CU-Boulder)

  5. Data Capture #1 Microsoft Network Monitor (free) can be used to capture packets in any channel in unassociated mode - OmniPeek has the same capability, but isn’t free Jim Lansford (Qualcomm/CU-Boulder)

  6. Data capture #2 Wireshark used to sort and classify packet traffic Jim Lansford (Qualcomm/CU-Boulder)

  7. Locations for Measurements Pearl Street Mall Engineering - University of Colorado at Boulder Pearl Street Mall (dense retail shops) • Unmanaged networks University of Colorado Campus • Managed network – ESS Residential environment • Dorm, apartment, house Jim Lansford (Qualcomm/CU-Boulder)

  8. Results #1: Pearl Street (1/2) • Number of Packets Collected: • ~12,000 • Collection Date & Time: • 04/24/2017 @ 2:40pm • Collection Length: • 00:02:39 Jim Lansford (Qualcomm/CU-Boulder) Over 75% of packets transmitted at data rate of 1&2Mbps and almost 69% of time at 1Mbps

  9. Results #1: Pearl Street (2/2) Jim Lansford (Qualcomm/CU-Boulder)

  10. Results #2: CU-Boulder (1/2) • Number of Packets Collected: • ~12,000 • Collection Length: • 00:02:57 • Collection Date & Time: • 04/17/2017 @ 4:00pm Over 70% of the packets used data rate of 1&2Mbps with over 53% of time at 1Mbps. Jim Lansford (Qualcomm/CU-Boulder)

  11. Results #2: CU-Boulder (2/2) Jim Lansford (Qualcomm/CU-Boulder)

  12. Results #3: Residential (1/2) • Number of Packets Collected: • ~11,000 • Collection Date & Time: • 04/23/2017 @ 12:10am • Collection Length: • 00:02:12 • Although over 29% of packets used data rate of 1Mbps, the time spent at this data rate was ~15%. • Over 25% of packets used data rate of 54Mbps (59% of the time) and ~28% of packets used a rate of 24Mbps (3.1% of the time). Jim Lansford (Qualcomm/CU-Boulder)

  13. Results #3: Residential (2/2) Jim Lansford (Qualcomm/CU-Boulder)

  14. Additional results – Pearl Street Occupancy: 2.06/2.3 minutes Jim Lansford (Qualcomm/CU-Boulder)

  15. Additional results – Campus Occupancy: 0.66/0/92 minutes Jim Lansford (Qualcomm/CU-Boulder)

  16. Additional results – Residence Occupancy: 0.7/2.45 minutes Jim Lansford (Qualcomm/CU-Boulder)

  17. 2) Indoor OFDM vs DSSS/CCK - Problem Statement Use packet capture and analysis tools to compare the performance of OFDM preambles vs DSSS/CCK preambles: • Assess PER or throughput vs distance • Compare indoor and outdoor if possible • Ensure that captured packets are only coming from the target AP, which has been configured to run iPerf with the desired preamble type Jim Lansford (Qualcomm/CU-Boulder)

  18. Indoor measurements – Discovery Learning Center @ CU-Boulder • Cisco Aironet 2700 Dual Band Access Point and Iperf 3 • AP manually configured to send only 1Mbps for DSSS tests • AP manually configured for OFDM-only preambles and 7Mbps payload for OFDM tests Jim Lansford (Qualcomm/CU-Boulder)

  19. Indoor measurements – raw data - #1 Jim Lansford (Qualcomm/CU-Boulder)

  20. Indoor measurements – graph - #1 Jim Lansford (Qualcomm/CU-Boulder)

  21. Indoor measurements – raw data - #2 6Mbps OFDM DSSS Interference? Jim Lansford (Qualcomm/CU-Boulder)

  22. Indoor measurements – graph - #2 6Mbps OFDM DSSS 0.11 0.396 Jim Lansford (Qualcomm/CU-Boulder)

  23. Summary (2.4GHz) 1Mbps traffic predominates • Beacons • Probe request/response - In congested environment, many more probe responses than probe requests • RTS/CTS • Over 75% of packets were 1Mbps management frames in congested environments OFDM preambles performed better than DSSS indoors • Always delivered better throughput at the same range • Difficult to assess failed preambles, but throughput results were consistent All papers are available Jim Lansford (Qualcomm/CU-Boulder)

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