SWRU616B September 2023 – April 2024 CC3300 , CC3301 , CC3301MOD , CC3350 , CC3351
Block acknowledgment (BA) is a feature introduced in the 802.11e IEEE Wi-Fi protocol and became mandatory in the 802.11n Wi-Fi protocol commonly referred to as Wi-Fi 4. It is used in conjunction with A-MPDUs and A-MSDUs to increase channel efficiency. As mentioned in Section 2.2, BA sessions are used to acknowledge multiple MPDUs together in a single BA frame rather than transmitting an individual ACK for every MPDU or frame. The BA protocol can only be used with QoS data frames (discussed in Section 2.7) and the number of possible links are dependent on the device and transmission direction (TX/RX). The CC33xx supports four BA sessions per each device link for data transmission (TX) and eight BA sessions per each device link when receiving data (RX).
This BA session is initialized through the transmission of a request and response exchange of initialization frames, referred to as ADDBA frames, between the AP and STA. This initialization includes an information exchange specifying parameters such as the QoS Transmission ID (TID) and buffer size. After initialization, multiple QoS data frames (the number of frames depends on buffer size) can be transmitted and acknowledged by a single block. This process is repeated until the BA session termination that is initiated by the BA session originator transmitting a session termination request known as a DELBA frame.