Method and apparatus for supporting link congestion detection in wireless communication system

A method performed by an integrated access and backhaul (IAB)-donor-central unit (CU) configured to operate in a wireless communication system, the method comprising:

• configuring an IAB network comprising an IAB-donor, a first IAB-node and a second IAB-node,
• wherein the IAB-donor is a gNB that provides network access to a user equipment (UE) via the IAB network,
• wherein the IAB-donor includes the IAB-donor-CU and an IAB-donor-distributed unit (DU),
• wherein the IAB-donor-CU is a gNB-CU of the IAB-donor, terminating F1 interface towards IAB-nodes, including the first IAB-node and the second IAB-node, and the IAB-donor-DU,
• wherein the IAB-donor-DU is a gNB-DU of the IAB-donor, hosting an IAB backhaul adaptation protocol (BAP) sublayer, providing wireless backhaul to the IAB-nodes,
• wherein each of the first IAB-node and the second IAB-node includes a DU which is a logical node hosting a radio link control (RLC) layer, a media access control (MAC) layer and a physical layer, and
• wherein the first IAB-node is a next-hop IAB-node of the IAB-donor and the second IAB-node is a next-hop IAB-node of the first IAB-node;
• transmitting downlink (DL) user data which is to be transmitted towards the second IAB-node via the IAB-donor-DU and the first IAB-node;
• based on an occurrence of link congestion or a blockage on a backhaul (BH)-radio link control (RLC) channel between the first IAB-node and the second IAB-node, receiving information about a problem on the BH-RLC channel between the first IAB-node and the second IAB-node,
• wherein the information is generated by the first IAB-node and transmitted from the first IAB-node to the IAB-donor-DU via a Downlink Data Delivery Status frame,
• wherein the information received by the IAB-donor-DU via the Downlink Data Delivery Status frame is forwarded by the IAB-donor-DU to the IAB-donor-CU via a Backhaul Status message, and
• wherein the Backhaul Status message includes information related to a transmission status of the DL user data at a time point when the link congestion or the blockage occurs;
• and
• stopping or reducing transmission of the DL user data towards the second IAB-node via the BH-RLC channel between the first IAB-node and the second IAB-node based on the information.