WLAN DESIGNS FOR SUPPORTING AN OUTDOOR PROPAGATION CHANNEL

摘要

W-LAN evolutions to support outdoor scenarios are proposed. In such outdoor scenarios, the usual cyclic prefix length of 800 nano-seconds is not long enough to capture all multipath components. The present application proposes to use longer CP than the normal IEEE 802.11 CP and a negotiation protocol for selecting the CP length. A so-called cyclic prefix discovery frame is sent from the Access Point (AP) to the stations (STA) requesting measurement (ie of the time domain channel estimation) and feedback of the desired Guard Period length (1.6 up to 6.4 micro-seconds are also available). A special Non Data Packet Long Delay Spread (NDP-L) frame is sent from the AP to the STAs to help measuring the delay spread. Further ideas (not claimed) comprise channel shortening using beamforming (after of before the IFFT) to reduce the delay spread of outdoor W-LAN signals.