On the capabilities of 802.11n devices to deliver high quality video content

1. On the capabilities of 802.11n devices to deliver high quality video content Date: 2007-06-25 Authors: Michael Livshitz, Metalink

2. Abstract To assist VTS SG scope discussion. Relevant tests were run to investigate the capabilities of 802.11n devices to deliver video streaming. Michael Livshitz, Metalink

3. Testing video capabilities of 11n devices The measurements were taken at a typical two-story, 200-square-meter private house. The walls are constructed with stone, concrete and iron rods. While no specific arrangements were made, it was observed that there were no other interfering or overlapping networks found in 2.4GHz or 5GHz bands. The locations of the access point and stations are overlaid on the map, and marked by numbers. Location point 6 is at the roof-level attic. For every test point, we used access points and STA from the same vendor. All devices used out-of-the box settings. Note that all but one device used 40MHz in 2.4GHz band, and all devices used 40MHz wide transmissions in 5GHz bands. First Floor Second Floor Michael Livshitz, Metalink 3

4. Test Description and Results Chariot scripts (UDP/RTP/MPEG2) were used to measure throughput and PER. Chariot script was run downstream from AP to STA for 15min. When devices under test demonstrated no packet errors, the new chariot test with throughput increased by 5Mbps was run. We recorded the highest throughput the devices were able to achieve while maintaining 15min of error free transmissions. All devices here are of-the-shelf products. The devices are not the same in 5GHz and in 2.4GHz bands and the their indices are intentionally not consistent. Horizontal axis show distance in meters with number of walls in parenthesis; vertical axes are throughput numbers in Mbps. 1 2 3 4 1 3 5 6 Michael Livshitz, Metalink 4

5. Test Conclusions • The perception that Wi-Fi is the wrong media for video streaming has certain merits. We observed the devices having difficulties meeting 5/10/20 Mbps throughput with no errors during 15min streaming, especially when located in separate rooms. • All devices we tested were part of 11n plugfests and went through significant interoperability testing. However, we observed that 11n compliance does notautomatically guarantee video quality. • For example, the devices 2 and 3 in 5GHz failed to show any video-grade throughput with PER less then 0.01%. (Error every 6/12/24s for 20/10/5 Mbps, which we believe is intolerable at video marketplace). • We also observed that there are 11n devices that can show throughput and PER to meet video quality expectations. • For example, the device 1 in 5GHz, and devices 1 and 2 in 2.4GHz. Michael Livshitz, Metalink 5

6. VTS Study Group Scope • Improve user experience by promoting a set of existing and/or new features of 802.11 • Stimulate market awareness by demonstrating that technology is capable of delivering high demanding content • Importance of whole house coverage Michael Livshitz, Metalink