Method for transmitting information for LTE-WLAN aggregation system and a device therefor

1. A method for a user equipment (UE) operating in a wireless communication system, the method comprising:

checking, by a Packet Data Convergence Protocol (PDCP) entity, whether a Flow Control Information (FCI) transmission condition is met or not; and

transmitting FCI based on the FCI transmission condition being met,

wherein the FCI includes a PDCP Sequence Number (SN) of a first missing PDCP Service Data Unit (SDU) and a highest PDCP SN among received PDCP SDUs, and

wherein the FCI transmission condition includes at least one of:

a value of percentage of an amount of PDCP Service Data Units (SDUs) stored in a PDCP reordering buffer from a size of the PDCP reordering buffer being above a first threshold for each transmission time interval (TTI) or for each PDCP SDU reception;

a sequence number (SN) gap between a PDCP SN of a next expected PDCP SDU and a PDCP SN of a last delivered PDCP SDU being above a second threshold for each TTI or for each PDCP SDU reception; or

a SN gap between a PDCP SN of an updated last delivered PDCP SN and an old last delivered PDCP SN being above a third threshold for each TTI or for each PDCP SDU reception at a reordering timer expiration.

2. The method according to claim 1 , wherein the FCI is transmitted through status report.

3. The method according to claim 1 , wherein the PDCP entity is associated with a bearer whose radio protocols are located in both an e-NodeB (eNB) and a Wire-less LAN (WLAN) to use both eNB and WLAN radio resources in LTE-WLAN Aggregation.

4. The method according to claim 1 , further comprising:

starting a FCI prohibit timer based on the FCI being transmitted; and

transmitting another FCI only after the FCI prohibit timer expires,

wherein the UE does not check whether the FCI transmission condition is met, and transmit the FCI, while the FCI prohibit timer is running.

5. A user equipment (UE) operating in a wireless communication system, the UE comprising:

a transceiver; and

a processor operatively coupled with the transceiver and that:

checks, by a Packet Data Convergence Protocol (PDCP) entity, whether a Flow Control Information (FCI) transmission condition is met or not; and

transmits FCI based on the FCI transmission condition being met,

wherein the FCI includes a PDCP Sequence Number (SN) of a first missing PDCP Service Data Unit (SDU) and a highest PDCP SN among received PDCP SDUs, and

wherein the FCI transmission condition includes at least one of:

a value of percentage of an amount of PDCP Service Data Units (SDUs) stored in a PDCP reordering buffer from a size of the PDCP reordering buffer being above a first threshold for each transmission time interval (TTI) or for each PDCP SDU reception;

a sequence number (SN) gap between a PDCP SN of a next expected PDCP SDU and a PDCP SN of a last delivered PDCP SDU being above a second threshold for each TTI or for each PDCP SDU reception; or

a SN gap between a PDCP SN of an updated last delivered PDCP SN and an old last delivered PDCP SN being above a third threshold for each TTI or for each PDCP SDU reception at a reordering timer expiration.

6. The UE according to claim 5 , wherein the FCI is transmitted through status report.

7. The UE according to claim 5 , wherein the PDCP entity is associated with a bearer whose radio protocols are located in both an e-NodeB (eNB) and a Wire-less LAN (WLAN) to use both eNB and WLAN radio resources in LTE-WLAN Aggregation.

8. The UE according to claim 5 , wherein the processor further starts a FCI prohibit timer based on the FCI being transmitted, and

transmits another FCI only after the FCI prohibit timer expires,

wherein the UE does not check whether the FCI transmission condition is met, and transmit the FCI, while the FCI prohibit timer is running.