The 802.11ax standard defines a PPDU as Inter-BSS or Intra-BSS as defined below: If the above conditions are not met for a frame, the frame is characterized as an Intra/Inter-BSS PPDU Dual NAV operation

802.11 stations follow Carrier sense-Multiple Access and Collision Avoidance (CSMA/CA) and the signal detect is around 4 dB above noise floor. Since, the Signal is detected at such a low level, an 802.11 station can latch on to a very far away signal from another BSS (termed Overlapping BSS) and backoff from performing its own […]

The Uplink transmission of frames from 802.11ax capable Stations to an 802.11ax Access Point requires a Trigger frame to be sent by the Access Point to the stations who would participate in the Multi-User UpLink transmission. The Trigger Frame will assign RUs, determine TX power for transmission and spatial streams to the HE capable stations. […]

The Access Point operating in 802.11ax can use the Resource Units that were discussed in the previous article <Resource Units in 802.11ax> to setup packet send to multiple non-AP stations in a single transmission. The Access Point assigns specific Resource Units to Specific stations. The AP encodes a packet meant for a specific station to […]

We saw how Unsolicited BSR is handled in 802.11ax <Buffer Status Reports – Unsolicited BSR>. A Solicited BSR is a response for a request for Buffer Status from a non-AP Station responding to a Buffer Status Report Poll (BSRP) trigger frame from an Access Point. The Trigger frame will have the type set to BSRP […]

Buffer status reports are non-AP stations sending a report to the AP on “Amount of buffered data at station“. This helps the Access Point to determine the RU allocation for specific station. The non-AP station can send buffered data implicitly via QoS control field or BSR control sub-field of any frame transmitted to the Access […]

The MU-RTS frame is a Trigger Frame in 802.11ax which has a trigger sub-field type value of 3. The MU-RTS frame purpose is to elicit a CTS response from atleast one of MU capable Stations addressed in the MU-RTS frame. The Trigger Frame format remains the same for MU-RTS. However, Most of the common info […]

The Trigger frame format and the need for the Trigger Frame was discussed briefly in the article <Trigger Frames in 802.11ax>. The Basic Trigger frame has the same frame format as defined in the previous article. It is depicted below: One major exception is that the “Trigger Dependent Common Info Field” in the Common Information […]

With the ability to transmit/receive to or from multiple non-AP Stations using Downlink/Uplink Multi-User operation, 802.11ax had to devise a set of operations to indicate to the no-AP stations which Resource Units to use. The “Trigger frame” was introduced in 802.11ax to indicate to a non-AP Station which RUs to utilise for its receive/transmit operation. […]

The 802.11ax OFDMA channel consists of 256 sub-carriers. the sub-carrriers can be grouped together into smaller sub-channels known as Resource Units (RUs). Depending on the channel bandwidth and the number of clients connected, the Resource Units can be as small as a 26 sub-carrier resource unit in a 20 MHz channel with 9 Clients or […]