xing HT_Greenfield HT GF format for PLCP header Short GI for 20 MHz Short guard interval for the 20 MHz radio channel Short GI for 40 MHz Short guard interval for the 40 MHz radio channel Tx STBC Transmission for the space-time diversity STBC Rx STBC Reception for the space-time diversity STBC HT-Delayed Block Ack Delayed acknowledgment mechanism Maximum size of frame aggregation Maximum A-MSDU Length A-MPDU (3,839 or 7,935 bytes) DSSS/CCK Mode in 40 MHz Using the DSSS/CCK mode for 40 MHz radio channel Forty MHz Intolerant Prohibition to use 40 MHz radio channel L-SIG TXOP Protection Support L-SIG TXOP protection mechanism Table 4.2. Information of HT Capabilities Info field A-MPDU Parameters: this field indicates the maximum size of the frame aggregation A-MPDU that the access point can receive and the minimum time between two MPDU data units of the aggregation. Supported MCS Set: this field indicates the modulation and coding schemes supported by the access point, for transmission and reception. 802. 11n Interface HT Extended Capabilities: this field indicates whether PCO (Phased Coexistence Operation) mode or RD (Reverse Direction) protocol is supported. Transmit Beamforming Capabilities: this field describes the supported features for beamforming. ASEL Capability: this field describes the supported features for antenna selection. The HT Capabilities information element is included in BEACON frames SO that mobiles can determine that the 802.11r interface is available. A mobile inserts the HT Capabilities information element into the PROBE REQUEST frame to search for 802.11n access points. The HT Capabilities information element is also included in the management frames ASSOCIATION REQUEST, ASSOCIATION RESPONSE, REASSOCIATION REQUEST, REASSOCIATION RESPONSE and PROBE RESPONSE. 4.1.1.2. HT Operation information element The HT Operation information element provides the mobile with the characteristics of the 802.1 11n interface and contains the following fields: Primary Channel: this field indicates the number of 