Method of radio bearer transmission in dual connectivity

A method of radio bearer transmission in dual connectivity for a mobile device in a long term evolution (LTE) system, wherein the mobile device is capable of simultaneously connecting to an access point (AP) of a wireless local area network (WLAN) and a base station of the LTE system, the method comprising:

• receiving, from the base station, an AP failure report configuration, wherein the AP failure report configuration includes throughput, a number of attempts to connect with the AP, and a timer of the attempts to connect with the AP;
• receiving, from the AP, a packet data convergence protocol protocol data unit (PDCP PDU) associated to a radio bearer (RB) with an identity, wherein the identity indicates which PDCP entity the PDCP PDU belongs to;
• removing the identity of the PDCP PDU;
• and
• delivering the PDCP PDU to a corresponding PDCP entity according to the identity, wherein the step of delivering the PDCP PDU to the corresponding PDCP entity according to the identity comprises:
• determining to perform a reordering function when an RB type of the RB is a split RB,
• determining not to perform the reordering function when the RB type is an assisted RB, and
• determining not to perform the reordering function when the RB type is a normal RB.