There is provided a method of operating at least one network unit in a wireless communication system, wherein the wireless communication system comprises a first network unit and a second network unit that are both connected to a third network unit using a first connection, between the first network unit and the third network unit, and using a second connection, between the second network unit and the third network unit, wherein packets comprising the same information are transmitted over both the first connection and the second connection. The method comprises the first network unit receiving information from the third network unit indicating packets received by the third network unit from the first network unit over the first connection, and transmitting an indication to the second network unit enabling removal of packets from one or more transmission buffers of the second network unit corresponding to the indicated packets received by the third network unit from the first network unit over the first connection.

A method, a transmitter and a computer program product for processing data units at the transmitter are disclosed. In one embodiment, data units are transmitted to a receiver according to a protocol and with respective sequence numbers. The protocol indicates that the receiver is to use a reordering window to determine whether a data unit which is newly received from the transmitter is a new or repeated data unit the data stream by comparing the sequence numbers of the newly received data unit and a previously received data unit. A status report is received and based thereon, the sequence number of a next data unit to be transmitted in a new cell following a handover is selectively adjusted such that the next data unit will be determined to be a new data unit. The next data unit is transmitted with the adjusted sequence number to the receiver.

Disclosed is a 5G or pre-5G communication system for supporting a data transmission rate higher than that of a 4G communication system, such as LTE. Disclosed is a method for receiving data in a wireless communication system, comprising the steps of: receiving, by a terminal, transmission point change information from a first base station connected to a gateway; receiving, by the terminal, the data transmitted from the gateway to the first base station through a second base station serving the terminal; and re-receiving, by the terminal, data, of which the transmission has failed, through a third base station according to a change of a transmission point from the second base station to the third base station on the basis of the transmission point change information, when data transmission from the second base station to the terminal has failed.

A first wireless access network node receives, from a second wireless access network node, delay information relating to a delay in buffering data at a protocol layer in the second wireless access network node. The first wireless access network node configures a discard timer based on the received delay information for a packet to be sent to a user equipment.

For continuous data transmission during a handover procedure, Make-Before-Break handover may be introduced, which maintains source evolved NodeB (eNB) connection after reception of radio resource control (RRC) message for handover. In order to reduce ambiguity of Make-Before-Break handover, the present invention provides receiving a handover command from a network, after receiving the handover command from the network, keeping exchanging data with a source cell, stopping exchanging data with the source cell when a condition is met, and after stopping exchanging data with the source cell, starting exchanging data with a target cell.

A method for managing link failure, according to one embodiment of the present invention, comprises the steps of: receiving a link failure report (LFR) for notifying that a link between user equipment and an base station of a second RAT has been disassociated; requesting an entity of a first RAT, which manages interworking between the first RAT and the second RAT, to switch a flow of downlink data for the user equipment, which is to be transmitted to the base station of the second RAT, to a base station of the first RAT; establishing a direct tunnel between the base station of the first RAT and the base station of the second RAT by using an identifier of the base station of the second RAT, which is included in the LFR of the user equipment; and relaying the downlink data for the user equipment, which has been buffered in the base station of the second RAT up to before the switch of the flow after the disassociation of the link, from the base station of the second RAT to the user equipment.

A first base station (BS), comprising: at least one storage device, configured to store program codes; a first communication interfacing device, configured to transmit signals or to receive signals with at least one BS; a second communication interfacing device, configured to transmit signals or to receive signals with a plurality of communication devices; at least one processing circuit, configured to execute the program codes comprising following steps: (a) associating a first PDCP SDU to a first PDCP SN for a first communication device, or associating an IP packet in the first PDCP SDU to a first PDCP SN, wherein the first PDCP SDU comprises a flow ID and the IP packet; (b) initiating a handover for the first communication device to a second BS; 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 method is disclosed for delivering a packet data flow across a radio access network (RAN), comprising: receiving, at an upstream gateway node, an Internet Protocol (IP) data flow; sending, from the upstream gateway node, the IP data flow to a RAN; receiving, at the upstream gateway node, a congestion control message from the RAN based on a request for retransmission of the IP data flow at the RAN to a user equipment (UE); and performing, at the upstream gateway node, IP flow control of the IP data flow based on the congestion control message.

Methods, systems, and devices for mobility optimization in a heterogeneous network are disclosed herein. A base station includes an anchor module, a context information module, and a transmission point module. The anchor module configures the base station as a virtual anchor cell for a plurality of small cells. The context information module is configured to maintain context information for user equipment (UE). The context information for the UE is maintained by the context information module while any small cell of the plurality of small cells is configured as a TP for the UE. The transmission point (TP) change module is configured to send at least a portion of the context information to a small cell configured as the TP for the UE.

A system is proposed to provide handover in a mobile telecommunications environment, particularly applicable to 3GPP networks, which does not increase signalling overhead but minimises user data loss during handover. In the modified system, PDCP SDUs with Sequence numbers are buffered and retransmitted as necessary. At the time of handover, SDUs not received by the user device are forwarded to the target base station for forward transmission to the UE. The handover procedure is designed to minimise packet loss whilst keeping to a minimum the duplication of packet transmission over the air interface.