Bi-directional WLAN channel measurements in different mobility scenarios

The interest in the behaviour of the wireless channel increases as WLAN access points become more widespread. In order to enhance the performance of existing applications in wireless environments, especially when mobility is present, knowledge about channel behaviour is of great importance. Nevertheless, very few experimental results have been documented and evaluated. We designed and realised a measurement campaign to investigate channel characteristics in different mobility conditions and different environments. Special attention is paid to the correlation between both channel directions. This is particularly interesting for channel-adaptive mechanisms; the strength of this correlation is important for the use of such techniques without the need for additional signalling or feedback of channel state information. We present the results of this measurement campaign. We evaluate the channel behaviour in various scenarios typical for WLAN. The linear time dependences within the same direction and between the opposite directions are calculated and compared. Finally we studied the usefulness of the results for channel prediction.