One can refer the first part of this blog here — <802.11g PLCP Frame Formats – Part 1> ERP-OFDM format The ERP-OFDM format is similar to the 802.11a OFDM PPDU format. The only change is that a signal extension field is added to the OFDM format of 802.11a as is done for all other 802.11g […]

The PLCP supported by 802.11a systems is shown below. The description of the different members of the PLCP is also incorporated. Fig Courtesy: 802.11 standards PLCP starts with training sequence (PLCP preamble), followed by the SIGNAL field and data. Both the training sequence and the 24 bit SIGNAL field are transmitted at 6Mbps rate. The […]

The 802.11n standard supports the legacy 802.11a/b/g PPDU formats. In addition it also supports two new PPDU formats. They are Mixed Mode PPDU format (allows co-existence with older clients) Green-field mode PPDU format (pure 11n client network) – optional The above two formats are termed as HT PPDU formats. The HT-Mixed mode format and the […]

The 802.11ac PPDU format supports the legacy 802.11a/n PPDU formats and the 802.11ac Very High Throughput (VHT) format. As 802.11ac is a 5GHz only standard – it does not have to support 802.11b/g PPDU formats. The PPDU format is shown below Fig Courtesy: 802.11 Standard The 802.11ac standard does not support a pure VHT format […]

The interested reader can refer the first part of the series here — <802.11ac PLCP Frame Format – Part 1> VHT-SIGB Field The VHT-SIGB format provides the Length and MCS rate that the 802.11ac frame was transmitted at in a Multi-User (MU) transmission. The VHT-SIGB field is one symbol and can be 26 bits in […]

The interested reader can refer the first part of the series here — <802.11ac PLCP Frame Format – Part 1> VHT Signal Fields – VHT-SIG A The VHT-SIGA field provides information on the different parameters of the frame at the receiver to configure itself to decode the received 802.11ac frame. The VHT-SIGA field is provided […]

Channel bonding in wireless LAN is the bonding of  adjacent 20 MHz channels to create a wider bandwidth channel (e.g 40MHz/80MHz etc). The higher bandwidth channel in effect will have higher bandwidth and hence higher data rate supported. One such example is shown below Fig Courtesy: Wikipedia As can be seen from the tabular column […]

The 802.11n standard introduced Multi-Input-Multi-Output (MIMO) into WLAN. This enabled Wi-Fi devices to increase their data rate. Further enhancements were also introduced in the 802.11n standard significant of which was MAC layer data aggregation, Channel bonding, transmit beam-forming and higher QAM modulation schemes. The current article delves into the basics of MIMO. MIMO stands for […]

For Transmit Beamforming to function properly, The channel characteristics between the transmitter and the receiver should be known accurately. To allow channel characteristics to be determined the concept of Null Data Packet (NDP) was introduced in the 802.11n specification. The Null Data packet does not contain any data field and purely comprises of the preamble […]

In the Pre-802.11n era, A WLAN device could have multiple antennas, but only transmit/receive the same signal on multiple antennas or use the best antenna for transmit or receive.  With the advent of MIMO, multiple data streams could in effect be transmitted on different antennas simultaneously. MIMO also provided a means of shaping the signal […]