Method for transmitting status report of PDCP layer in mobile telecommunications system and receiver of mobile telecommunications

1. A method for transmitting a status report of a Packet Data Convergence Protocol (PDCP) layer in a mobile communications system, in a method for transmitting, by a receiving side PDCP layer, a status report for a series of data to a transmitting side PDCP layer, the method comprising:

determining, by the receiving side PDCP layer, a reception status of the series of data, wherein the series of data are PDCP Service Data Units (SDUs); and

transmitting, by the receiving side PDCP layer, a reception status report for the PDCP SDUs to the transmitting side PDCP layer, such that the transmitting side PDCP layer is able to transmit or retransmit the series of data during handover, wherein the reception status report is transmitted in the form of a bitmap including sequence number (SN) information of the PDCP SDUs indicating whether or not the PDCP SDUs have successfully been received,

wherein the format of the PDCP data including the reception status report comprises a D/C field, a PDU type field, a bitmap field and a field including SN information on a PDCP SDU corresponding to the first or last bit of the bitmap field, the PDCP data being configured by arranging the fields in the order of the D/C field, the PDU type field, the field including the SN information of the PDCP SDU, and the bitmap field.

2. The method of claim 1 , wherein the reception status report for the series of data is transmitted from the receiving side PDCP layer to the transmitting side PDCP layer in the form of PDCP Protocol Data Unit (PDU).

3. The method of claim 2 , wherein the PDCP data is PDCP data PDU or PDCP control PDU depending on a value of the D/C field.

4. The method of claim 2 , wherein the D/C field indicates whether the PDCP data is PDCP data PDU or PDCP control PDU, the PDU type field indicates a type of control information, the bitmap field is configured as indicators indicating whether or not each of the PDCP SDUs has successfully been received, and the field including the SN information of the PDCP SDU corresponding to the first or last bit of the bitmap field is a First Sequence Number (FSN) field or a Last Sequence Number (LSN) field.

5. The method of claim 4 , wherein the LSN field indicates a sequence number (SN) of a PDCP SDU corresponding to the last bit of the bitmap field.

6. The method of claim 4 , wherein the FSN field indicates a sequence number (SN) of a PDCP SDU corresponding to the first bit of the bitmap field.

7. The method of claim 2 , wherein the PDCP data further comprises a length field, and the length field includes information related to a length of the bitmap field.

8. The method of claim 4 , wherein the bitmap field includes indicators indicating the successful or unsuccessful reception of each of the PDCP SDUs.

9. The method of claim 8 , wherein each of the indicators is comprised of one bit, and a value of the one bit is set to ‘0’ or ‘1’ so as to indicate whether or not a corresponding PDCP SDU has successfully been received.

10. A receiver in a mobile communications system comprising:

a processor configured to determine whether or not PDCP SDUs received via a Packet Data Convergence Protocol (PDCP) layer have successfully been received, generate information related to the reception success or failure of the determined PDCP SDUs in the form of a bitmap, and include the information generated in the form of the bitmap in a PDCP Protocol Data Unit (PDU), such that a transmitting side PDCP layer is able to transmit or retransmit a series of data during handover,

wherein the PDCP PDU comprises a D/C field, a PDU type field, a bitmap field, and a field including Sequence Number (SN) information of a PDCP SDU corresponding to the first or last bit of the bitmap field, the PDCP PDU being configured by arranging the fields in the order of the D/C field, the PDU type field, the field including the SN information of the PDCP SDU, and the bitmap field.

11. The receiver of claim 10 , wherein the D/C field indicates whether the PDCP data is PDCP data PDU or PDCP control PDU, the PDU type field indicates a type of control information, the bitmap field is configured as indicators indicating whether or not each of the PDCP SDUs has successfully been received, and the field including the SN information of the PDCP SDU corresponding to the first or last bit of the bitmap field is a First Sequence Number (FSN) field or a Last Sequence Number (LSN) field,

wherein the FSN field indicates a sequence number (SN) of a PDCP SDU corresponding to the first bit of the bitmap field, and the LSN field indicates a sequence number (SN) of a PDCP SDU corresponding to the last bit of the bitmap field.

12. The receiver of claim 11 , wherein the PDCP PDU further comprises a length field, and the length field includes information related to the length of the bitmap field.