Method of packet reordering and packet retransmission
A packet reordering method and a packet transmission method to implement reliable data communication are disclosed. The method of transmitting packets at a serving base station in case of a mobile station performing handover include, receiving a series of packets from an upper layer entity, and transmitting the series of packets one after the other to a target base station, wherein a packet of the series of packets includes an information field which represents whether the packet is the last transmitted packet. When the mobile station performs the I-RAT handover, the target serving station pre-reorders PDU packets, and transmits the reordered PDU packets to the mobile station, such that the mobile station can quickly transmit data without reordering the packets.
1. A method of transmitting packets at a serving base station in case of a mobile station performing handover, the method comprising:
receiving a series of packets from an upper layer entity;
transmitting the series of packets sequentially to a target base station,
wherein a packet of the series of packets includes a packet type field indicating a type of the series of packets and an information field which represents whether the packet is the last transmitted;
receiving a reception status message regarding the series of packets from the target base station, the reception status message including a bitmap field and a starting sequence number field, the bitmap field indicating whether an error of the series of packets is detected in order from a last transmitted packet to a first transmitted packet, the starting sequence number field indicating a sequence number of a next packet to be transmitted by the serving base station; and
retransmitting at least one error-detected packet to the target base station according to the reception status message.
2. The method of claim 1 , wherein the information field further includes information indicating that the series of packets are transmitted from the serving base station.
3. The method of claim 1 , wherein transmitting the series of packets sequentially to the target base station comprises:
transmitting a packet data convergence protocol (PDCP) header including a sequence number, wherein the sequence number represents completion of the transmitting of the series of packets, after all of the series of packets are transmitted.
4. The method of claim 3 , wherein the sequence number entirely consists of ‘1’ or ‘0’.
5. A method of transmitting reordered packets at a target base station in case of a mobile station performing handover, the method comprising:
receiving a series of first packets sequentially from a serving base station, wherein a first packet of the series of first packets includes an information field indicating whether the first packet is last transmitted;
receiving a series of second packets sequentially from an upper layer entity;
reordering an order of the received packets;
transmitting the reordered packets to the mobile station;
receiving a reception status message regarding the transmitted reordered packets from the mobile station, the reception status message including a bitmap field and a starting sequence number field, the bitmap field indicating whether an error of the transmitted reordered packets is detected in order from a last transmitted packet to a first transmitted packet, the starting sequence number field indicating a sequence number of a next packet to be transmitted by the target base station; and
retransmitting at least one error-detected packet to the mobile station according to the reception status message.
6. The method of claim 5 , further comprising,
after receiving the series of second packets,
storing the series of second packets to a buffer of the target base station.
7. The method of claim 6 , wherein the series of second packets are stored to the buffer, and are transmitted after all of the series of first packets are transmitted.
8. The method of claim 6 , wherein the information field further includes information indicating that the first packet is the last transmitted packet from the serving base station.
9. The method of claim 6 , further comprising:
receiving a packet data convergence protocol (PDCP) header including a sequence number from the serving base station, the sequence number representing completion of transmission of the first series of packets.
10. The method of claim 9 , wherein the sequence number entirely consists of ‘1’ or ‘0’.