A method may be provided to operate a node of a radio access network communicating with a wireless terminal. The wireless terminal may be configured to provide a transmit buffer for data to be transmitted to the node during transmission time intervals, to transmit packets of the data from the transmit buffer to the node during respective transmission time intervals, and to provide buffer indicator bits with respective packets of the data during the respective transmission time intervals. The method may include: receiving a packet including data and a buffer indicator bit from the wireless terminal during a respective transmission time interval; and providing an estimate of a quantity of data in the transmit buffer at the wireless terminal responsive to a status of the buffer indicator bit. Related wireless terminals and network nodes are also discussed.