BWA stands for Bandwidth Allocation.
BWA is an important aspect when dealing with large group calls, where participants may receive more than a single incoming media stream. In such cases, the decision of what percentage of the estimated bandwidth to allocate per incoming media stream becomes important.
Since each participant is limited by the performance of the device, the display resolution and the download speeds, there is likely to be a need to curb the amount of data being sent. Reducing that amount needs to be done based on the priorities of the given scenario, which is what BWA is meant to achieve. Such priorities can be defined by dominant speaker identification, displayed resolution, phases of the moon or any other heuristic.
BWA will usually get its upper bound of total bitrate from a BWE (bandwidth estimation) algorithm.