A method performed by a User Equipment, UE, for small data transmission, the method comprising: receiving, when operating in a Radio Resource Control, RRC, CONNECTED state, an RRC release message from a Base Station, BS, the RRC release message indicating at least one downlink, DL, Reference Signal, RS, at least one Configured Grant, CG, resource and information indicating an association between the at least one DL RS and the at least one CG resource; transitioning to an RRC _INACTIVE state in response to receiving the RRC release message; initiating an attempt for the small data transmission; measuring the at least one DL RS to obtain a measurement result; selecting, from the at least one CG resource, a particular CG resource for the small data transmission according to the measurement result; determining whether a Timing Advance, TA, value for the particular CG resource is valid for the small data transmission according to i) an amount of Reference Signal Received Power, RSRP, change of a DL RS associated with the particular CG resource, the DL RS being one of the at least one DL RS, and ii) whether a TA-related timer is running; and performing the small data transmission on the particular CG resource after determining that the TA value is valid, wherein: the TA-related timer defines a time interval during which the TA value is allowed to be determined as valid; the TA-related timer is configured by a TA-related timer configuration provided by the BS; the TA-related timer is started when the TA value is received; and the at least one CG resource is released when the TA-related timer expires. receiving, when operating in a Radio Resource Control, RRC, CONNECTED state, an RRC release message from a Base Station, BS, the RRC release message indicating at least one downlink, DL, Reference Signal, RS, at least one Configured Grant, CG, resource and information indicating an association between the at least one DL RS and the at least one CG resource; transitioning to an RRC _INACTIVE state in response to receiving the RRC release message; initiating an attempt for the small data transmission; measuring the at least one DL RS to obtain a measurement result; selecting, from the at least one CG resource, a particular CG resource for the small data transmission according to the measurement result; determining whether a Timing Advance, TA, value for the particular CG resource is valid for the small data transmission according to i) an amount of Reference Signal Received Power, RSRP, change of a DL RS associated with the particular CG resource, the DL RS being one of the at least one DL RS, and ii) whether a TA-related timer is running; and performing the small data transmission on the particular CG resource after determining that the TA value is valid, wherein: the TA-related timer defines a time interval during which the TA value is allowed to be determined as valid; the TA-related timer is configured by a TA-related timer configuration provided by the BS; the TA-related timer is started when the TA value is received; and the at least one CG resource is released when the TA-related timer expires. the TA-related timer defines a time interval during which the TA value is allowed to be determined as valid; the TA-related timer is configured by a TA-related timer configuration provided by the BS; the TA-related timer is started when the TA value is received; and the at least one CG resource is released when the TA-related timer expires.