In 5G networks, the Buffer Status Report (BSR) is a mechanism used by user devices to inform the network about the amount of data that they have buffered for transmission. This information is then used by the network to schedule resources for the device’s uplink transmission.
Truncated BSR is a feature introduced to reduce the overhead associated with transmitting BSRs. In the traditional BSR mechanism, the user device sends a complete BSR message to the network every time its buffer status changes. This can result in a significant amount of overhead, especially in scenarios with a large number of devices.
With truncated BSR, the user device only sends the most significant bits of the BSR message to the network, rather than sending the complete message. The network can then use this truncated information to estimate the device’s buffer status and schedule resources accordingly. This reduces the amount of overhead associated with BSR transmission, while still providing the network with the necessary information to efficiently schedule uplink resources.
When more than one LCG has data available for transmission but remaining UL allocation is not sufficient to sent Long BSR then Truncated BSR MAC CE is used
