A first base station, BS,, wherein the first BS is a fifth generation, 5G, BS of a new radio, NR, network, the first BS comprising: at least one storage device, configured to store program codes; a first communication interfacing device, configured to transmit signals to or to receive signals from at least one other BS; a second communication interfacing device, configured to transmit signals to or to receive signals from a first communication device; at least one processing circuit, coupled to the at least one storage device and the first and second communication interfacing devices, configured to execute the program codes comprising following steps: (a) associating a first packet data convergence protocol, PDCP, service data unit, SDU, to a first PDCP sequence number, SN, for the first communication device, or associating an internet protocol, IP, packet in the first PDCP SDU to the first PDCP SN, wherein the first PDCP SDU comprises a flow identifier, ID, identifying a data flow and the IP packet; (b) initiating a handover for the first communication device from the first BS to a second BS, wherein the second BS is an evolved NodeB, eNB, of a long term evolution, LTE, network; and (c) controlling the first communication interfacing device to forward the IP packet but not to forward the flow ID, to the second BS in response to the handover. at least one storage device, configured to store program codes; a first communication interfacing device, configured to transmit signals to or to receive signals from at least one other BS; a second communication interfacing device, configured to transmit signals to or to receive signals from a first communication device; at least one processing circuit, coupled to the at least one storage device and the first and second communication interfacing devices, configured to execute the program codes comprising following steps: (a) associating a first packet data convergence protocol, PDCP, service data unit, SDU, to a first PDCP sequence number, SN, for the first communication device, or associating an internet protocol, IP, packet in the first PDCP SDU to the first PDCP SN, wherein the first PDCP SDU comprises a flow identifier, ID, identifying a data flow and the IP packet; (b) initiating a handover for the first communication device from the first BS to a second BS, wherein the second BS is an evolved NodeB, eNB, of a long term evolution, LTE, network; and (c) controlling the first communication interfacing device to forward the IP packet but not to forward the flow ID, to the second BS in response to the handover. (a) associating a first packet data convergence protocol, PDCP, service data unit, SDU, to a first PDCP sequence number, SN, for the first communication device, or associating an internet protocol, IP, packet in the first PDCP SDU to the first PDCP SN, wherein the first PDCP SDU comprises a flow identifier, ID, identifying a data flow and the IP packet; (b) initiating a handover for the first communication device from the first BS to a second BS, wherein the second BS is an evolved NodeB, eNB, of a long term evolution, LTE, network; and (c) controlling the first communication interfacing device to forward the IP packet but not to forward the flow ID, to the second BS in response to the handover.