A communication device for handling a cellular-wireless local area network, cellular-WLAN, aggregation, CWA, between a 3GPP cellular network and a WLAN network, the communication device comprising: a storage device, for storing instructions of: establishing a radio resource control, RRC, connection to the cellular network; receiving a first RRC message configuring a CWA for a radio bearer from the cellular network on the RRC connection; enabling data handling for the radio bearer in response to the first RRC message; communicating a plurality of packet data convergence protocol, PDCP, protocol data units, PDUs, associated with the radio bearer with the WLAN according to the CWA, when the data handling for the radio bearer is enabled; receiving an RRCConnectionRelease message or a MobilityFromEUTRACommand message on the RRC connection from the cellular network, wherein the RRCConnectionRelease message indicates a suspension of the RRC connection; storing at least one of a current RRC configuration, a current security context, a PDCP state comprising a robust header compression, ROHC, state, a Cell Radio Network Temporary Identifier, C-RNTI, used in a source primary cell, PCell, a cellIdentity, a physical cell identity of the source PCell and a resumeIdentity in response to the RRCConnectionRelease message; disabling the data handling for the radio bearer and stopping performing data recovery for the radio bearer, in response to the RRCConnectionRelease message or the MobilityFromEUTRACommand message; disabling the data handling for the radio bearer and performing the data recovery, when the communication device receives a second RRC message which indicates a release of the CWA or reconfigures the radio bearer to be a cellular-only radio bearer; and a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device. establishing a radio resource control, RRC, connection to the cellular network; receiving a first RRC message configuring a CWA for a radio bearer from the cellular network on the RRC connection; enabling data handling for the radio bearer in response to the first RRC message; communicating a plurality of packet data convergence protocol, PDCP, protocol data units, PDUs, associated with the radio bearer with the WLAN according to the CWA, when the data handling for the radio bearer is enabled; receiving an RRCConnectionRelease message or a MobilityFromEUTRACommand message on the RRC connection from the cellular network, wherein the RRCConnectionRelease message indicates a suspension of the RRC connection; storing at least one of a current RRC configuration, a current security context, a PDCP state comprising a robust header compression, ROHC, state, a Cell Radio Network Temporary Identifier, C-RNTI, used in a source primary cell, PCell, a cellIdentity, a physical cell identity of the source PCell and a resumeIdentity in response to the RRCConnectionRelease message; disabling the data handling for the radio bearer and stopping performing data recovery for the radio bearer, in response to the RRCConnectionRelease message or the MobilityFromEUTRACommand message; disabling the data handling for the radio bearer and performing the data recovery, when the communication device receives a second RRC message which indicates a release of the CWA or reconfigures the radio bearer to be a cellular-only radio bearer; and a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device.