Investigation into the Doppler Component of the IEEE 802.11n Channel Model

Simulations show that the Doppler component of the IEEE 802.11n channel model results in a dramatic decrease in transmit beamforming gain within only 20 ms delay, even though the model is intended for indoor WLAN environment with stationary devices. However, new measurements collected in an office environment show that degradation to transmit beamforming gain is much less sensitive to delay. With normal environmental conditions in the office environment, it was found that on average there was only a 22% decrease in transmit beamforming gain after 200 ms delay. Even with highly exaggerated motion, reasonable gain is maintained with over 100 ms of delay. Measurements with a moving device were also conducted with resulting sensitivity to delay similar to the 802.11n model. The measurements indicate that the Doppler component of the 802.11n channel model is more comparable to a moving device rather than a stationary device. The use of transmit beamforming in an indoor WLAN environment is more practical than simulations based on the IEEE 802.11n channel models would imply.