Description Of The Pdu

The system provided by the present invention at least comprises a transmitting terminal and a receiving terminal. The transmitting terminal is used to transmit the data in the form of packets through a predetermined first data message pdu. After an Acknowledged Mode Radio Link Control (AM RLC) connection is established between the receiving terminal and the transmitting terminal, the receiving terminal receives the data according to the length of the first data message pdu transmitted from the transmitting terminal, and calculates the ber or the BER of the first data message pdu, so as to calculate an appropriate second data message pdu length, and provide a pdu change request, such that the transmitting terminal continuously transmits data with the second data message pdu length. Furthermore, the transmitting terminal measures a retransmission rate of the first data message pdu, and when the transmitting terminal found that the retransmission rate changes, it calculates an appropriate third data message pdu length according to the ber or BER of the first data message pdu responded from the receiving terminal, and provides the pdu change request, thereby informing the receiving terminal to receive the data with the third data message pdu length.

The pdu formats used in this system at least comprise the following three types. One is the data message pdu, which is transmitted from the transmitting terminal to the receiving terminal, and the transmitting terminal carries the data required for being transmitted by the upper layer, so as to form a packet for being transmitted to the receiving terminal. The above first data message pdu, the second data message pdu, and the third data message pdu all fall into the scope of this category. The second type is a data acknowledgement message pdu, which is transmitted from the receiving terminal to the transmitting terminal, different from the data message pdu, and used for providing information about the receiving state of the data message pdu. The third type is the data message length change requirement pdu, which is transmitted from the receiving terminal to the transmitting terminal, for informing the transmitting terminal to adjust the length of the data message pdu, and the above pdu change request falls in the scope of this category. The data message pdu at least comprises a sequence number field, a data length reset bit field, and a length field. The data acknowledgement message pdu at least comprises a sequence number field and a data message receiving state field. The data message length change requirement pdu at least comprises a changed pdu length filed.

The data transmission method provided by the present invention comprises the following steps. First, a connection is established between a transmitting terminal and a receiving terminal in Step (A). In Step (B), the transmitting terminal transmits data to the receiving terminal with a first data message pdu. In Step (C), the receiving terminal sends a pdu change request to the transmitting terminal. Finally, in Step (D), the transmitting terminal utilizes a second data message pdu in the pdu change request to transmit the subsequent data to the receiving terminal. The above connection is an AM RLC connection.
steps: first, the transmitting terminal sets the data length reset bit of the first data message pdu as 0; next, upon receiving the first data message pdu, the receiving terminal takes the length of the first data message pdu as the used pdu length. Step (C) further comprises: first, the receiving terminal calculates the ber or BER of the received first data message pdu, and informs the transmitting terminal about a message of ber or BER with a pdu change request or a response message; next, the receiving terminal determines whether to change the used pdu length or not according to the information of the ber or BER, and calculates a pdu length that achieves the maximum bandwidth utilization as the length of the second data message pdu, wherein the receiving terminal informs the transmitting terminal about the length of the second data message pdu with the pdu change request. Step (D) further comprises the following sub-steps: the transmitting terminal sets the length of the second data message pdu according to the received pdu change request, and sets the data length reset bit of the second data message pdu as 1 when transmitting the second data message pdu for the first time; then, the receiving terminal changes the pdu length used by the receiving terminal, upon receiving the second data message pdu with the data length reset bit as 1.

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