interfaces. This field allows mobiles that do not handle the 802.11n interface to determine the radio channel occupancy time, the bit rate being 6 Mbps. HT-SIG (HT Signal): Table 4.4 describes the information in this field. Wi-Fi Integration to the 4G Mobile Network Information Bit number Designation Index of the modulation and coding scheme (76 values) Channel Bit to ZERO for a bandwidth at 20 MHz Bandwidth Bit at ONE for a bandwidth at 40 MHz HT Length Size in bytes of the PSDU payload Bit to ONE for smoothing the assessment of channel Smoothing aggregation. Bit to ZERO for independent assessment of each channel Bit to ZERO if the PPDU data unit is a sounding Not Sounding Bit to ONE if not Bit to ONE if the data unit contains A-MPDU sub-frames Aggregation ZERO bit if not 2 bits to ZERO if transmission diversity is not used STBC (Space- Time Block If not, value indicating the difference between the number Coding) of spatial/temporal diversity streams and the number of spatial flows FEC (Forward Bit to ZERO for LDPC (Low-Density Parity Check) Error coding Correction) Bit to UN for BCC (Binary Convolutional Code) coding Short GI Bit to ONE if a short guard interval is used (Guard Interval) ZERO bit if not Indicates the number of extension spatial streams. Number of Set to 0 for no extension spatial stream. extension spatial Set to 1 for 1 extension spatial stream. streams Set to 2 for 2 extension spatial streams. Set to 3 for 3 extension spatial streams. Cyclic redundancy code Tail of the convolutional encoder Table 4.4. HT-SIG field structure 802.1 11n Interface HT-STF (HT Short Training Field): this field has the same purpose as the L-STF field. There are two types of HT-LTF (HT Long Training Field): - DATA HT-LTF field helps to set the MIMO (Multiple Input Multiple Output) mechanism; - HT-LTF Extension field is used for beamforming. The number of HTF LTF fields depends on the number of spatial flows. This field is optional. 4.3. PMD sub-layer Table 4.5 summarizes the features provided by the PMD (Physical Mediu