Interpretation of MFB/ASELC information Identifier of the sequence relating to a MFSI (MCS Feedback Sequence Identifier) request for a recommendation on the value of the modulation and coding scheme (MCS) MFB/ASELC (MCS Feedback and Antenna MCS recommended value or features of Selection Command) antenna selection Table 4.3. Information of Link Adaptation Control field Calibration Position: this field indicates the position in the exchange sequence relative to the calibration sounding. Calibration Sequence: this field contains the identifier of the exchange sequence. CSI/Steering: this field indicates the type of response for beamforming. 68 Wi-Fi Integration to the 4G Mobile Network NDP Announcement: this field indicates whether an empty frame is transmitted after the data unit. AC Constraint: this field indicates whether the data in the RD protocol belongs to a single access category (AC). RDG More PPDU: this field is interpreted differently, for the RD protocol, if it is transmitted by the initiator (allocation of a resource or not) or the responder (the frame is the last transmitted or not). 4.1.3. Frame aggregation 4.1.3.1. A-MPDU frame The A-MPDU (Aggregate MAC Protocol Data Unit) frame is an A-MPDU sub-frame sequence (Figure 4.2). Each A-MPDU sub-frame contains a delimiter, an MPDU frame and pad bytes. IP packet IP packet MAC header MAC header Delimiter Delimiter A-MPDU sub-frame A-MPDU sub-frame A-MPDU frame Figure 4.2. Structure of A-MPDU frame With the exception of the last A-MPDU sub-frame, the padding bytes are added SO that the size of each A-MPDU sub-frame is a multiple of four bytes. The delimiter contains the size of the MPDU frame, an error check (CRC) on the frame size and a signature that can be used to detect a delimiter. The unique pattern is set to 4E in hexadecimal notation. As each A-MPDU sub-frame gets its own MAC header, the encryption is applied to each sub-frame independently. Since each A-MPDU sub-frame 802. 11n Interface has its own error detection sequence, an error will only affect 