Steps for PMP Certification
Referring to FIGS. 1 and 3, in this embodiment, the data transmission method includes: (A) establishing a connection between the transmitting terminal and the receiving terminal (Step 310); (B) the transmitting terminal transmitting the data to the receiving terminal with the first data message pdu (Step 320); (C) the receiving terminal providing a pdu change request to the transmitting terminal (Step 330); and (D) the transmitting terminal transmitting.
First, an Acknowledged Mode Radio Link Control (AM RLC) connection is established between the transmitting terminal 110 and the receiving terminal 120. In the WCDMA network, a connection needs to be established before data transmission. Establishing a connection between the transmitting terminal 110 and the receiving terminal 120 includes the following steps. Depending on the circumstance that it is the transmitting terminal 110 or the receiving terminal 120 that initiates to establish a connection, if the transmitting terminal 110 initiates to establish a connection, the transmitting terminal 110 transmits a Radio Resource Control (RRC) message including a plurality of pdu lengths, i.e., types of all the pdu lengths available for being used in the subsequent data transmission. After the transmitting terminal 110 transmits the RRC message, the receiving terminal 120 receives the RRC message, and establishes a type corresponding to the available pdu length.
Then, the transmitting terminal 110 transmits the data to the receiving terminal 120 with the first data message pdu that is configured when establishing the connection. The first data message pdu is the above pdu 210, and the transmitting terminal 110 divides a plurality of batches of data into a plurality of first data message pdus and then transmits them to the receiving terminal 120. The transmitting terminal 110 sets the data length reset bit of the first data message pdus as 0, and after receiving the first data message pdu, the receiving terminal 120 takes the length of the first data message pdu as the predetermined pdu length.
Once receiving the first data message pdu transmitted from the transmitting terminal 110, the receiving terminal 120 calculates the ber or BER of the first data message pdu accordingly. Ber may be obtained by way of check sum, whereas the BER may be calculated and obtained through an equation of BER=(1-(1-ber)pdu length), which are not limited in this embodiment. The transmitting terminal 110 piggybacks the ber or the BER in a pdu change request or a response message to inform the transmitting terminal 110 about the ber or BER of the first data message pdu, wherein the pdu change request is the above pdu 230, and the response message is the above pdu 220. After calculating the ber or the BER, the receiving terminal 120 determines whether to change the currently used pdu length or not according to the calculation result. An excessive large or small pdu length still influences the data transmission. Each transmitted pdu includes a forward message and a real data for being transmitted. Although the correct rate of the data transmission is relatively high if the data is transmitted through the relatively small pdu, repeatedly transmitting the forward message influences the bandwidth utilization. On the contrary, if the data is transmitted through the excessively large pdu length, the repeatedly transmitting of the forward message is saved, but the longer pdu is, the lower the correct rate is, which causes the retransmission of the pdu to be more frequent, thereby indirectly wasting the bandwidth utilization.
First, an Acknowledged Mode Radio Link Control (AM RLC) connection is established between the transmitting terminal 110 and the receiving terminal 120. In the WCDMA network, a connection needs to be established before data transmission. Establishing a connection between the transmitting terminal 110 and the receiving terminal 120 includes the following steps. Depending on the circumstance that it is the transmitting terminal 110 or the receiving terminal 120 that initiates to establish a connection, if the transmitting terminal 110 initiates to establish a connection, the transmitting terminal 110 transmits a Radio Resource Control (RRC) message including a plurality of pdu lengths, i.e., types of all the pdu lengths available for being used in the subsequent data transmission. After the transmitting terminal 110 transmits the RRC message, the receiving terminal 120 receives the RRC message, and establishes a type corresponding to the available pdu length.
Then, the transmitting terminal 110 transmits the data to the receiving terminal 120 with the first data message pdu that is configured when establishing the connection. The first data message pdu is the above pdu 210, and the transmitting terminal 110 divides a plurality of batches of data into a plurality of first data message pdus and then transmits them to the receiving terminal 120. The transmitting terminal 110 sets the data length reset bit of the first data message pdus as 0, and after receiving the first data message pdu, the receiving terminal 120 takes the length of the first data message pdu as the predetermined pdu length.
Once receiving the first data message pdu transmitted from the transmitting terminal 110, the receiving terminal 120 calculates the ber or BER of the first data message pdu accordingly. Ber may be obtained by way of check sum, whereas the BER may be calculated and obtained through an equation of BER=(1-(1-ber)pdu length), which are not limited in this embodiment. The transmitting terminal 110 piggybacks the ber or the BER in a pdu change request or a response message to inform the transmitting terminal 110 about the ber or BER of the first data message pdu, wherein the pdu change request is the above pdu 230, and the response message is the above pdu 220. After calculating the ber or the BER, the receiving terminal 120 determines whether to change the currently used pdu length or not according to the calculation result. An excessive large or small pdu length still influences the data transmission. Each transmitted pdu includes a forward message and a real data for being transmitted. Although the correct rate of the data transmission is relatively high if the data is transmitted through the relatively small pdu, repeatedly transmitting the forward message influences the bandwidth utilization. On the contrary, if the data is transmitted through the excessively large pdu length, the repeatedly transmitting of the forward message is saved, but the longer pdu is, the lower the correct rate is, which causes the retransmission of the pdu to be more frequent, thereby indirectly wasting the bandwidth utilization.