Method and apparatus for transmitting and receiving signal and communication system

An apparatus for transmitting and receiving signals, applicable to a first integrated access and backhaul node donor central unit (IAB-donor-CU), the apparatus comprising first controller circuitry configured to:

• transmit a traffic offload request to a second IAB-donor-CU;
• and
• receive a reply of agreement of traffic offload or a reply of rejection of traffic offload transmitted by the second IAB-donor-CU, wherein,
• the IAB node is connected to a first parent node, and the IAB node is connected to a second parent node, the first parent node being a node in a topology of the first IAB-donor-CU, and the second parent node being a node in a topology of the second IAB-donor-CU, and
• the traffic offload request is contained in a traffic offload request message, the reply of agreement of traffic offload is contained in a traffic offload request acknowledge message, and the reply of rejection of traffic offload is contained in a traffic offload request reject message.

An apparatus for transmitting and receiving signals, applicable to a second integrated access and backhaul node donor central unit (IAB-donor-CU), the apparatus comprising a-second controller circuitry configured to:

• receive a traffic offload request transmitted by a first IAB-donor-CU;
• and
• transmit a reply of agreement of traffic offload or a reply of rejection of traffic offload to the first IAB-donor-CU,
• wherein the first IAB-donor-CU transmits a first RRC reconfiguration message to an IAB node and/or a descendant IAB node of the IAB node via the IAB node after receiving the reply of agreement of traffic offload,
• the first RRC reconfiguration message comprises at least one TNL address allocated for the IAB node and/or the descendant node of the IAB node, the TNL address being anchored to a second IAB-donor-DU, and
• the IAB node is connected to a first parent node, the first parent node being a node in a topology of the first IAB-donor-CU, and the IAB node is already or is to be connected to a second parent node, the second parent node being a node in a topology of the second IAB-donor-CU.

An apparatus for transmitting and receiving signals, applicable to an IAB node, the IAB node being connected to a first parent node, and the IAB node being already or being to be connected to a second parent node, the first parent node being a node in topology of a first IAB-donor-CU, and the second parent node being a node in topology of a second IAB-donor-CU,

• the apparatus comprising third controller circuitry configured to:
• receive, by the IAB node, a second RRC reconfiguration message transmitted by the second IAB-donor-CU, the second RRC reconfiguration message comprising BAP configuration information (bap-Config), the BAP configuration information including a second BAP address configured for the IAB node;
• and
• transmit an RRC reconfiguration complete message by the IAB node to the second IAB-donor-CU,
• wherein the RRC reconfiguration complete message is used to indicate that the IAB node has received the second RRC Reconfiguration message.