What is HT Physical Mode in your Router? HT Physical Mode In HT Physical mode setting allow for control of the 802.11n wireless environment. Operating Mode Mixed Mode Green Field Mixed Mode: In this mode packets are transmitted with a preamble compatible with the legacy 802.11a/g, the rest of the packet has a new format. In this mode the receiver shall be able to decode both the Mixed Mode packets and legacy packets. Green Field: In this mode high throughput packets are transmitted without a legacy compatible part. Channel BandWidth: Set channel width of wireless radio. 20 20/40 20 Channel Width = 20 MHz 20/40 Channel Width = 20/40 MHz Guard Interval: Support Short/Long GI, the purpose of the guard interval is to introduce immunity to propagation delays, echoes and reflections, to which digital data is normally very sensitive. Long Auto Long Guard Interval, 800 nsec Short Guard Interval, 400 nsec MCS: Fix MCS rate for HT rate. 0-15 The Modulation and Coding Scheme is a value that determines the modulation, coding and number of spatial channels.