Communications devices, method and mobile communications system

A method of operating a communications device acting as a relay device configured to communicate with a transmitting node operating with a mobile communications network and a receiving node operating with the mobile communications network, the method comprising

• receiving signals representing protocol data units formed from one or more service data units via a first wireless access interface from the transmitting node according to a first automatic repeat request protocol for transmission to the receiving node,
• storing in a buffer data conveyed by or representing the protocol data units received from the transmitting node according to the first automatic repeat request protocol for transmission to the receiving node according to a second automatic repeat request process, wherein the second automatic request process is a hybrid automatic request process,
• wherein based on the data conveyed by or representing the received protocol data units as a number of protocol data units or number of bytes stored in the buffer exceeds a predetermined threshold, the method comprises transmitting by the communications device acting as the relay device to the transmitting node an indication that the data representing the number of protocol data units or the number of bytes stored in the buffer exceeds the predetermined threshold,
• wherein the buffer is a first buffer, the first buffer being a transmission buffer configured to store the protocol data units formed from the one or more service data units that are received for transmission to the receiving node as the data representing the received protocol data units according to the second automatic repeat request process from a second buffer, the second buffer being a reception buffer, and the second buffer is separate from the first buffer.

Circuitry for a communications device acting as a relay device configured to communicate with a transmitting node operating with a mobile communications network and a receiving node operating with the mobile communications network, the communications device acting as the relay device comprising

• receiver circuitry configured to receive signals representing protocol data units formed from one or more service data units via a first wireless access interface from the transmitting node according to a first automatic repeat request protocol for transmission to the receiving node,
• transmitter circuitry configured to transmit signals representing the received protocol data units via a second wireless access interface to the receiving node according to a second automatic repeat request protocol,
• controller circuitry configured to control the transmitter circuitry to transmit the signals and to control the receiver circuitry to receive the signals to transmit, and
• a buffer configured to store data conveyed by or representing the protocol data units received by the receiver circuitry for transmission to the receiving node according to the second automatic repeat request process, wherein the second automatic request process is a hybrid automatic request process,
• wherein based on the data conveyed by or representing a number of the received protocol data units or number of bytes stored in the buffer exceeds a predetermined threshold, the controller circuitry is configured in combination with the transmitter circuitry and the buffer
• to transmit to the transmitting node an indication that the number of protocol data units or the number of bytes stored in the buffer exceeds the predetermined threshold,
• wherein the buffer is a first buffer, the first buffer being a transmission buffer configured to store the protocol data units formed from the one or more service data units received from the receiver circuitry for transmission to the receiving node as the data representing the received protocol data units according to the second automatic repeat request process from a second buffer, the second buffer being a reception buffer, and the second buffer is separate from the first buffer.