| 08/25/03 T&E Report Multi-Polarization Wireless Concept and Antenna Designs It has become clear that determining real-life performance of antennas in changing positions and obstructed environments requires more than (anechoic chamber) testing with equipment as a network analyzer. Simulated changes in the environment can be rather reflectively conclusive. In vivo real-life testing and evaluation requires many repeat trials in various scenarios and is laborious, but the (statistical) analysis is what determines the validity overall of new design concepts as it relates to actual (consumer) usage. For this T&E report, in that it had previously been clearly determined that circular polarization was significantly better than either vertical, horizontal, or a diversity combination of the two, testing was performed comparing the subject multi-polarized antennas with the circularly polarized antennas, in terms of SNR, packet loss, and the radio bit rate. Testing here was performed in the 2.4 GHz radio frequency band. ** Tests were done in which one end of the link had two of the multi-polarized omni antennas in a diversity configuration (the second antenna was receive-only). The other end of the link had either one or two of the 18" directional multi-polarized antennas.
The directional antenna was placed outside, and the omni end was moved within another building so that there were from 10 to 20 walls between the two endpoints. Signal and noise levels were recorded at both ends, as well as video packet loss, and the bit rate of the radio (the radio automatically switches between 11Mbps, 5Mbps, 2Mbps, and 1Mbps depending on the quality of the signal). The same test was run 3 to 5 times (each test lasted about a minute), with 3 different antenna configurations:
1) multi-polarized antennas (omni diversity at one end and a single directional antenna at the other end).
2) multi-polarized antennas (omni diversity at one end and directional diversity at the other end).
3) circular polarized antennas (omni diversity at one end and a single directional antenna at the other end).
The following table summarizes the results:
| | | Multi-Polarized With diversity at both endpoints | Multi-polarized with diversity only at the omni endpoint | Circular polarized with diversity only at the omni endpoint | | Omni endpoint | Average Signal | -65.0 dBi | -63.6 dBi | -70.0 dBi | | | Average Noise | -86.0 dBi | -87.2 dBi | -87.0 dBi | | | Average SNR | 20.8 dB | 21.6 dB | 16.7 dB | | | Average Radio Bit Rate* | 8.7 Mbps | 9.0 Mbps | 7.8 Mbps | | Directional endpoint | Average Signal | -64.0 dBi | -64.8 dBi | -74.0 dBi | | | Average Noise | -86.8 dBi | -88.6 dBi | -87.3 dBi | | | Average SNR | 22.0 dB | 23.4 dB | 13.0 dB | | | Average Radio Bit Rate* | 5.5 Mbps | 5.2 Mbps | 2.9 Mbps | | Video Packet Loss | Average % packet loss | 29% | 24% | 46% |
* The 802.11b radio switches automatically between 11,5,2, and 1Mbps, depending upon the signal quality. The Average Radio Bit Rate that was
measured is the average of the radio's reported bit rate setting sampled at 1 sec. intervals.
In summary, the multi-polarized antennas consistently performed better than the circular polarized antennas, in terms of SNR, packet loss, and the radio bit rate. Subjectively, the video quality was perceptibly improved with the multi-polarized antennas. With an application of streaming live video and audio at up to 4 Mbps, the multi-polarized antennas consistently performed better than horizontal, vertical, or circular polarization. In conclusion, the [WiFi-Plus'] multi-polarized antennas provided almost twice the performance overall of circular polarized antennas, previously the best antenna design for difficult multi-path environments. ** Similar results historically seen testing at other frequencies. |