The 802.11ac wireless LAN standard provided additional channel bonding capabilities for 80 MHz/160 MHz and a split mode 80+80 MHz. The channel bonding capabilities build upon the channel bonding capabilities of 802.11n. The HT capability/Operation elements provided the primary channel information and the secondary channel information in the case of 40 MHz channel bonding as […]

If Multiple Mac Protocol Data units are aggregated to form one frame – then the aggregation is termed as A-MPDU aggregation. The A-MPDU aggregation is depicted pictorially below Fig Courtesy: 802.11-2012TM Standard As defined in the standard – the MPDU delimiter is used as below The purpose of the MPDU delimiter is to locate the […]

If the frame aggregation is carried out prior to MAC layer encapsulation – then the aggregation is termed as Aggregated MAC Service Data Unit (A-MSDU). The A-MSDU frame format is provided below Fig Courtesy: 802.11-2012TM Standard As is seen from the figure, each A-MSDU sub-frame consists of a Destination Address (DA), Source Address (SA), Length […]

The WLAN standard body defined how the channel centre frequency would be computed and provided formulae to compute the centre frequency for various channel bonding operations. The below tabular column and examples from the 802.11ac standard depict this operation. For a more detailed explanation – refer channelization section (22.3.14 Channelization) in the 802.11ac standard. Fig […]

802.11n supported 76 MCS rates and the tabular column showing the throughput obtained via the combination of MCS rate, Modulation scheme, channel bonding, guard band are shown below Modulation and coding schemes MCS index Spatial streams Modulation type Coding rate Data rate (in Mbit/s)[a] 20 MHz channel 40 MHz channel 800 ns GI 400 ns GI 800 ns GI 400 ns GI […]

802.11n and later WLAN standards introduced the concept of data frame aggregation. Even in earlier 802.11 standards, it was possible to send certain frames aggregated with a data frame (for e.g. CF-END frame with a QoS Frame), however, Data frames were never aggregated till then. The reason for aggregation of data frames can be depicted […]

The 802.11ac standard provided the number of spatial streams to be 8 and also increased the channel bonding size to 160 MHz (also 80+80MHz operation was allowed). This increased the theoretical throughput available to around 6 Gbps. The below table provides the data rate supported by 802.11ac. Spatial Streams VHT MCS Index Modulation Coding Rate […]

The A-MPDU Parameters define the size of an aggregated packet and also define the proper spacing between aggregated packets so that the receive side WLAN station is able to decode the packet properly. The A-MPDU parameters are part of the HT Capability Information element and the VHT Capability information fields. The A-MPDU parameter set in […]

The High-Throughput (HT) Immediate Block Ack was also introduced in 802.11n along-with aggregation of data packets. The combination of Immediate Block Ack and aggregation was a significant improvement on the Contention Free burst and block ack request/block ack mechanism. The earlier legacy block ack mechanism required the WLAN device to send a block ack request […]

Similar to delayed block Ack, an HT-Delayed Block Ack session provides the WLAN station to receive/transmit a Block Ack frame at a later time from the time when an A-MPDU was transmitted. HT-Delayed Block Ack is an optional feature. The HT-Delayed Block Ack support is advertised in the HT capabilities information field. Fig Courtesy – […]