Method for transmitting data packet in mobile communication system

[0028] The present invention will be further described below through specific embodiments.

[0029] Reference image 3 , Figure 4 with Figure 5 , A method for transmitting data packets in a mobile communication system. The service data unit SDU is segmented and processed to generate one or more segments of protocol data unit PDUs, and then the PDUs are divided into byte alignment and can be allocated in a wireless frame. When the data payload of the last segment is not enough to fill the entire segment, add padding bits at the end of the segment to make the length of the segment equal to The other segments are the same, and a unified data packet header is used to indicate the transmission format of these transmission blocks. It includes the following steps:

[0030] ①Segment the business data unit SDU;

[0031] ②Add CRC to the SDU segment to generate PDU;

[0032] ③According to the physical channel resource carrying bit length corresponding to a radio frame, calculate the padding bits required by the PDU, divide the PDU into one or more transmission blocks of the same length;

[0033] ④ Generate the data packet header, perform physical layer processing on the data packet header and transmission block and send it out.

[0034] Reference Figure 4 with Figure 5 , When the business data unit SDU length L SDU When it is greater than the maximum length L of a packet defined by the data link layer L2, the SDU is segmented, and each segment is aligned by bytes, and the length of each segment is less than or equal to L; otherwise, the SDU has only one segment. Less than or equal to the maximum length of PDU Max_L PDU.

[0035] Reference Figure 4 with Figure 5 , After segmenting the SDU, perform a CRC check on each SDU segment, and append the CRC check bit to the end of the SDU segment to generate a protocol data unit PDU with a length of L PDU = The length of the SDU segment L SDU +CRC check length L CRC.

[0036] Reference Figure 4 with Figure 5 , When PDU length L PDU More than the physical channel resource bearer bit length L corresponding to a radio frame TB When the PDU is further divided into length L TB Multiple transmission blocks of equal length, each transmission block is transmitted by a physical channel resource corresponding to a radio frame, if the length of the last segment is less than L TB , Add padding bits at the end of the PDU section so that the length of the section is L after adding padding bits TB; Otherwise, there is only one transmission block, and when L PDU Less than L TB When adding padding bits at the end of the PDU, the length of the segment after adding padding bits is L TB , And when it is necessary to add padding bits at the end of the PDU, the padding bits are always increased by whole bytes.

[0037] Reference figure 1 with figure 2 The frame structure of a TDMA communication system adopted by the present invention includes 7 time slots and a guard time interval GP. Each time slot can be configured as uplink or downlink as required. One available configuration is that Slot 0, 1, 2, and 3 are configured as the downlink direction, and Slots 4, 5, and 6 are configured as the uplink direction. A general time slot structure of the present invention is that each time slot includes 2 pilot bands and 3 data segments. The pilot band carries the pilot sequence, the data section is used to carry signaling, voice or data information, and the transmission block is loaded in the data section for transmission. The pilot band is fixed with π/4DQPSK modulation. For the data section, when used to carry system broadcast information, control signaling or voice information, the π/4DQPSK modulation method is used. When used to carry data information, π/4DQPSK can be used The modulation method or π/8D8PSK modulation method, which modulation method is used, is indicated by the control signaling. The present invention is based on but not limited to this frame structure, and the method of the present invention is also applicable to other digital mobile communication systems.

[0038] Reference figure 1 with figure 2 , Data communication between communication devices is always based on pre-allocated physical channel resources for transmission. When the physical channel resources are determined, the length of data that can be transmitted in a frame is related to the modulation mode and coding rate used. For the frame structure of the above TDMA communication system, if the total number of symbols in a time slot data segment is S, when the π/4DQPSK modulation mode is adopted, the number of bits that can be carried in a time slot is 2*S, and when the π/8D8PSK modulation mode is adopted At this time, the number of bits that a time slot can carry is 3*S. When the adopted channel coding rate is R, the data bit length before channel coding that can be carried in a time slot is 2*S*R or 3*S*R.

[0039] Reference image 3 The data packet header is provided with a TM field for indicating the current data transmission mode, an MCS field for indicating the modulation and coding format of the transport block, and an EF field for indicating whether the currently sent SDU segment is the last segment of the SDU , The SSN field used to indicate the sequence number of the currently sent SDU segment, the LI field used to indicate the byte length of the currently sent PDU, and the SID field and TID field respectively used to indicate the address of the sending device and the address of the receiving device. The transmission mode includes an acknowledged mode AM that requires the receiving device to feed back the receiving state of the transport block and an unacknowledged mode UM that does not require the receiving device to feed back the receiving state of the transport block. In order to ensure reliable transmission of the data packet header, it is also necessary to perform CRC check and FEC encoding on the data packet header.

[0040] Reference image 3 , Figure 4 with Figure 5 , A method for receiving data packets in a mobile communication system. After receiving the data packet header, the receiving device can determine the original number of bits transmitted at one time at the physical layer according to the transmission block modulation coding format indicated by the MCS field, that is, the transmission block length L TB , Combined with L PDU , Can calculate the number of transmission blocks included in this transmission PDU C and the length of filling bits included in the last transmission block L PAD , The C passes to L PDU /L TB The obtained value is rounded up to get, the L PAD =C*L TB -L PDU. According to the number of transmission blocks included in the PDU and the length of the padding bits included in the last transmission block, after receiving all the transmission blocks included in a PDU, the receiving device cascades these transmission blocks and removes the padding bits to restore the data sent by the sender PDU, and pass the CRC check, the length of the end of the PDU is L CRC The CRC check bit is removed, and the SDU segment is recovered. If an SDU is divided into multiple segments during transmission, the receiving device also needs to use the SSN field to indicate the currently sent SDU segment number and to indicate the current Whether the sent SDU segment is an indication of the EF field of the last segment of the SDU, after receiving all the SDU segments, the concatenation restores the original SDU.

[0041] Reference Figure 4 with Figure 5 The process of a method for sending data packets in a mobile communication system of the present invention is as follows:

[0042] ① Receive the original data packet SDU requested by the application layer, and then go to the process ②;

[0043] ②Judging the length of the original data packet SDU L SDU Is it greater than the maximum length L of a packet data packet defined by the data link layer L2, and L is less than or equal to the maximum length of the protocol data unit PDU Max_L PDU , If L SDU L, go to process ③, otherwise, SDU has only one segment, skip to process ④;

[0044] ③Segment the SDU, each segment is aligned by byte, and the length of each segment is Li SDU Less than or equal to L, suppose it is divided into I segments in total, set i=0, and then go to process ④;

[0045] ④ Perform CRC check on the i-th SDU segment, and append the CRC check bit to the end of the SDU segment, the CRC check length is L CRC , The generated length is L PDU =Li SDU +L CRC PDU, then go to process ⑤;

[0046] ⑤Judging the PDU length L PDU Is it greater than the physical channel resource bearer bit length L corresponding to a radio frame TB , If L PDU L TB , Go to process ⑥, otherwise, there is only one transmission block, if L PDU =L TB , Then skip to process ⑦, if L PDU TB , Add L at the end of the PDU TB -L PDU After filling bits, skip to process ⑦;

[0047] ⑥ Segment the PDU and divide it into multiple transmission blocks of equal length, each with a length of L TB , If L PDU /L TB If the remainder is not 0, you need to add padding bits at the end of the PDU, so that after adding padding bits, the PDU can be equally divided into multiple lengths of L TB Transmission block, the number of transmission blocks C and the length of the padding bit L PAD The calculation formula is as follows:

[0048] C=ceil(L PDU /L TB ), where ceil() is rounded up,

[0049] L PAD =C*L TB -L PDU ,

[0050] Then to the process ⑦;

[0051] ⑦Generate the data packet header, perform physical layer processing on the data packet header and each transmission block and send it, and then go to the process ⑧;

[0052] ⑧ Determine whether there are unsent SDU segments, if there are, i=i+1, if i

[0053] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any insubstantial modification of the present invention using this concept should be an act that violates the protection scope of the present invention.