A network node comprising: a communication interfacing unit configured for communicating with a communication device via a radio resource control, RRC, connection and at least one first radio bearer, RB, with a master cell group, MCG, bearer type; and a processor electrically connected with the communication interfacing unit, the processor configured to perform operations comprising: controlling the communication interfacing unit to establish at least one second RB with a secondary cell group, SCG, bearer type between the communication device and an auxiliary network node; and receiving a start signal from the auxiliary network node that a first condition is met; wherein the first condition is that all of downlink data in all of at least one downlink buffer corresponding to one of the at least one second RB is successfully transmitted or all of the at least one downlink buffer corresponding to one of the at least one second RB is empty, and the auxiliary network node does not receive any request for an uplink grant allocation from the communication device; releasing the one of the at least one second RB when it is determined, based on the start signal, that the first condition has been met for a first time period, wherein releasing the one of the at least one second RB when it is determined that the first condition has been met comprises: starting a timer with the first time period when it is determined that the first condition is met; and releasing the one of the at least one second RB when the timer expires. a communication interfacing unit configured for communicating with a communication device via a radio resource control, RRC, connection and at least one first radio bearer, RB, with a master cell group, MCG, bearer type; and a processor electrically connected with the communication interfacing unit, the processor configured to perform operations comprising: controlling the communication interfacing unit to establish at least one second RB with a secondary cell group, SCG, bearer type between the communication device and an auxiliary network node; and receiving a start signal from the auxiliary network node that a first condition is met; wherein the first condition is that all of downlink data in all of at least one downlink buffer corresponding to one of the at least one second RB is successfully transmitted or all of the at least one downlink buffer corresponding to one of the at least one second RB is empty, and the auxiliary network node does not receive any request for an uplink grant allocation from the communication device; releasing the one of the at least one second RB when it is determined, based on the start signal, that the first condition has been met for a first time period, controlling the communication interfacing unit to establish at least one second RB with a secondary cell group, SCG, bearer type between the communication device and an auxiliary network node; and receiving a start signal from the auxiliary network node that a first condition is met; wherein the first condition is that all of downlink data in all of at least one downlink buffer corresponding to one of the at least one second RB is successfully transmitted or all of the at least one downlink buffer corresponding to one of the at least one second RB is empty, and the auxiliary network node does not receive any request for an uplink grant allocation from the communication device; releasing the one of the at least one second RB when it is determined, based on the start signal, that the first condition has been met for a first time period, wherein releasing the one of the at least one second RB when it is determined that the first condition has been met comprises: starting a timer with the first time period when it is determined that the first condition is met; and releasing the one of the at least one second RB when the timer expires. starting a timer with the first time period when it is determined that the first condition is met; and releasing the one of the at least one second RB when the timer expires.