Method and apparatus for communication in an Integrated Access and Backhaul (IAB) system with buffer status report (BSR) are disclosed. The apparatus include a receiver that receives a BSR indicating that data is expected to be received; a processor that calculates a first type of buffer size based on the received BSR indicating that data is expected to be received and/or a second type of buffer size based on data presently stored in a buffer; and a transmitter that transmits a buffer status comprising the first type of buffer size and/or the second type of buffer size.