Patent Publication Number: US-11665579-B2

Title: Apparatus and method for controlling data flow in wireless communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application of prior application Ser. No. 16/468,981, filed on Jun. 12, 2019, which will be issued as U.S. Pat. No. 10,993,138 on Apr. 27, 2021; which is a U.S. National Stage application under 35 U.S.C. § 371 of an International application number PCT/KR2017/014583, filed on Dec. 12, 2017, which is based on and claimed priority of a United Kingdom patent application number 1621072.6, filed on Dec. 12, 2016, in the United Kingdom Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a wireless communication system, and more particularly, relates to apparatus and method for controlling a data flow in wireless communication system. 
     BACKGROUND ART 
     To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. 
     The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. 
     In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. 
     In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed. 
     As a need for data transmission grows rapidly, a plurality of data flows can be configured in a wireless communication network. Therefore, it is required to manage and control the data flows in a wireless communication network. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     An aspect of the present disclosure is to manage and/or control data flows in wireless communication network. 
     Solution to Problem 
     According to the present disclosure there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows. 
     According to a first aspect of the present disclosure, there is provided a method of managing a QoS flow in a telecommunication system, wherein a QoS flow is a flow of data carried by a Data Radio Bearer, DRB, between a mobile device and a radio network, via one or more network entities, comprising the step of a QoS flow being moved from a first DRB to a second DRB. 
     In an embodiment, a plurality of QoS flows of a particular mobile device are routed via at least two network entities sequentially, simultaneously or a combination of both. Here, ‘sequentially’ refers to a handover; ‘simultaneously’ refers to dual connectivity; and ‘a combination of both’ refers to a handover with dual connectivity. 
     In an embodiment, only some of a plurality of QoS flows of a particular mobile device are handed from a first network entity to a second network entity. 
     In an embodiment, the QoS flow is moved individually, not with any other QoS flows carried by the same DRB. 
     In an embodiment, the QoS flow is moved from a source DRB to a target DRB. 
     In an embodiment, the QoS flow is moved along with any other QoS flow(s) carried by the same DRB. 
     In an embodiment, wherein the QoS flow and the any other QoS flow(s) are moved: from source MN or cell to target MN or cell; 
     between MN or cell and SN or cell; 
     from MCG bearer type to MCG-split bearer type; or 
     to conform to LTE+LTE NR 
     In an embodiment, relating to a handover from a source eNB to a target eNB, wherein the handover is either a normal handover wherein the target eNB understands the configuration in the source eNB and continues with that configuration with potential updates, or a full configuration handover wherein the target eNB configures a new Access Stratum configuration. 
     In an embodiment, QoS flow to DRB mappings are maintained to ensure lossless and in sequence delivery. 
     In an embodiment, the QoS low to DRB mapping may be altered if lossless and in sequence delivery is not required. 
     In an embodiment whereby the MCG is LTE and the SCG is NR, the MN is operable to decide whether a QoS flow is offloaded to SCG/SN. 
     In an embodiment, the MN initiates such a request to the CN. 
     In an embodiment, for all or part of the QoS flows of a PDU session, part of the traffic may be terminate to the MN and another part to the SN. 
     In an embodiment, this is possible for all the QoS flows mapped to a particular DRB. 
     In an embodiment, the MN decides the DRBs to be configured and the QoS flow to DRB mapping. 
     According to a second aspect of the present disclosure, there is provided a method of managing a QoS flow in a telecommunication network, operating in a Dual Connectivity configuration, such that communication between a User Equipment and a Core Network is performed over a first node and a second node, comprising the step of the core network creating a second backhaul tunnel between itself and the second node, in addition to a first backhaul tunnel between itself and the first node, wherein the first and second backhaul tunnel are for the same PDU session. 
     According to a third aspect of the present disclosure there is provided a method of forwarding data packets on handover. The method also relates to forwarding of data packets upon change of termination point of a QoS flow in DC. 
     In an embodiment, tunnels per DRB and tunnels per PDU session are employed, for packets allocated to a DRB and for packets designated for QoS mobility, respectively. 
     In an embodiment, packets allocated per DRB are provided with PDCP SN in packet header. 
     In an embodiment, packets allocated for QoS mobility are provide with QoS flow id in packet header. 
     In an embodiment, the target node configures or requests per QoS flow whether forwarding should be performed. 
     In an embodiment, an end marker is provided per QoS flow. 
     Although a few preferred embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims. 
     Advantageous Effects of Invention 
     According to various embodiments of the present disclosure, data flows in wireless communication network can be efficiently controlled and/or managed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which: 
         FIG.  1    illustrates a wireless communication system according to various embodiments of the present disclosure; 
         FIG.  2    illustrates a network device in the wireless communication system according to various embodiments of the present disclosure; 
         FIG.  3    illustrates the terminal in the wireless communication system according to various embodiments of the present disclosure; 
         FIG.  4    illustrates the communication interface in the wireless communication system according to various embodiments of the present disclosure; 
         FIGS.  5 ( a ) and ( b )  show network configurations with 1:1 bearer mapping, as in case of LTE RAN connected to EPC, and QoS flow based scheme respectively, as in the case of NR RAN connected to 5G CN; 
         FIG.  6    shows a more detailed view of  FIG.  5 ( a ) ; 
         FIG.  7    shows LTE QoS architecture in a dual connectivity (DC) configuration according to an embodiment of the invention; 
         FIG.  8    shows a signalling diagram illustrating the message sequence for the case where a first SCG cell is configured to the UE i.e. a procedure referred to as SCG establishment or SN addition according to an embodiment of the invention; 
         FIG.  9    shows NR QoS architecture in a non-DC configuration according to an embodiment of the invention; 
         FIG.  10    shows a representation of Level 1 mobility (i.e. a case involving, for a given DRB, a change QoS flows to DRB mapping) according to an embodiment of the invention; 
         FIG.  11    shows a representation of Level 2 mobility according to an embodiment of the invention; 
         FIG.  12    shows a representation of handover in a combination of Level 1 and Level 2 mobility shown for the case of handover, according to an embodiment of the invention; 
         FIG.  13    shows a representation of handover in Level 1 mobility (I.e. there is no DRB for which the QoS flow to DRB mapping remains un-changed) according to an embodiment of the invention; 
         FIG.  14    shows NR QoS architecture with 1 tunnel per PDU session, where all QoS flows of PDU sessions 2 are offloaded/moved to an SN, according to an embodiment of the invention; 
         FIG.  15    shows NR QoS architecture with multiple tunnels per PDU session according to an embodiment of the invention; 
         FIG.  16    shows NR QoS architecture with split bearers according to an embodiment of the invention; 
         FIG.  17    NR QoS architecture, including ASML layer according to an embodiment of the invention; 
         FIG.  18    shows a message flow diagram relating to MeNB offloading traffic by moving an entire DRB (DRB2) to SeNB, according to an embodiment of the invention; 
         FIG.  19    shows a message flow diagram relating to initiating offloading of additional QoS flow (QoS flow 2) according to an embodiment of the invention; and 
         FIG.  20    shows a message flow diagram relating to initiating offloading of additional QoS flow (QoS flow 3) according to an embodiment of the invention; 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, in various embodiments of the present disclosure, hardware approaches will be described as an example. However, various embodiments of the present disclosure include a technology that uses both hardware and software and thus, the various embodiments of the present disclosure may not exclude the perspective of software. 
     Hereinafter, the present disclosure describes technology for controlling data flows in a wireless communication system. 
     The terms referring to a signal, the terms referring to a channel, the terms referring to control information, the terms referring to a network entity, and the terms referring to elements of a device used in the following description are used only for convenience of the description. Accordingly, the present disclosure is not limited to the following terms, and other terms having the same technical meaning may be used. 
     Further, although the present disclosure describes various embodiments based on the terms used in some communication standards (for example, 3rd Generation Partnership Project (3GPP)), they are only examples for the description. Various embodiments of the present disclosure may be easily modified and applied to other communication systems. 
       FIG.  1    illustrates a wireless communication system according to various embodiments of the present disclosure. In  FIG.  1   , a base station (BS)  110 , a terminal  120 , and a terminal  130  are illustrated as the part of nodes using a wireless channel in a wireless communication system.  FIG.  1    illustrates only one BS, but another BS, which is the same as or similar to the BS  110 , may be further included. 
     The BS  110  is network infrastructure that provides wireless access to the terminals  120  and  130 . The BS  110  has coverage defined as a predetermined geographical region based on the distance at which a signal can be transmitted. The BS  110  may be referred to as “access point (AP),” “eNodeB (eNB),” “5th generation (5G) node,” “wireless point,” “transmission/reception Point (TRP)” as well as “base station.” 
     Each of the terminals  120  and  130  is a device used by a user, and performs communication with the BS  110  through a wireless channel. Depending on the case, at least one of the terminals  120  and  130  may operate without user involvement. That is, at least one of the terminals  120  and  130  is a device that performs machine-type communication (MTC) and may not be carried by the user. Each of the terminals  120  and  130  may be referred to as “user equipment (UE),” “mobile station,” “subscriber station,” “remote terminal,” “wireless terminal,” or “user device” as well as “terminal.” 
     The BS  110 , the terminal  120 , and the terminal  130  may transmit and receive wireless signals in millimeter wave (mmWave) bands (for example, 28 GHz, 30 GHz, 38 GHz, and 60 GHz). At this time, in order to improve a channel gain, the BS  110 , the terminal  120 , and the terminal  130  may perform beamforming. The beamforming may include transmission beamforming and reception beamforming. That is, the BS  110 , the terminal  120 , and the terminal  130  may assign directivity to a transmission signal and a reception signal. To this end, the BS  110  and the terminals  120  and  130  may select serving beams  112 ,  113 ,  121 , and  131  through a beam search procedure or a beam management procedure. After that, communications may be performed using resources having a quasi co-located relationship with resources carrying the serving beams  112 ,  113 ,  121 , and  131 . 
     A first antenna port and a second antenna ports are considered to be quasi co-located if the large-scale properties of the channel over which a symbol on the first antenna port is conveyed can be inferred from the channel over which a symbol on the second antenna port is conveyed. The large-scale properties may include one or more of delay spread, doppler spread, doppler shift, average gain, average delay, and spatial Rx parameters. 
       FIG.  2    illustrates a network device  200  in the wireless communication system according to various embodiments of the present disclosure. A structure exemplified at  FIG.  2    may be understood as a structure of the network device  200 , which may comprises at least one of the BS  110 , serving gateway (S-GW), mobility management entity (MME), or other network entities included in a core network. According to various embodiments of the present disclosure, the BS  110  may be a master eNB (MeNB), or a secondary eNB (SeNB). The term “-module”, “-unit” or “-er” used hereinafter may refer to the unit for processing at least one function or operation and may be implemented in hardware, software, or a combination of hardware and software. 
     Referring to  FIG.  2   , the network device may include a wireless communication interface  210 , a backhaul communication interface  220 , a storage unit  230 , and a controller  240 . 
     The wireless communication interface  210  performs functions for transmitting and receiving signals through a wireless channel. For example, the wireless communication interface  210  may perform a function of conversion between a baseband signal and bitstreams according to a physical layer standard of the system. For example, in data transmission, the wireless communication interface  210  generates complex symbols by encoding and modulating transmission bitstreams. Further, in data reception, the wireless communication interface  210  reconstructs reception bitstreams by demodulating and decoding the baseband signal. 
     In addition, the wireless communication interface  210  up-converts the baseband signal into an Radio Frequency (RF) band signal, transmits the converted signal through an antenna, and then down-converts the RF band signal received through the antenna into the baseband signal. To this end, the wireless communication interface  210  may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog convertor (DAC), an analog-to-digital convertor (ADC), and the like. Further, the wireless communication interface  210  may include a plurality of transmission/reception paths. In addition, the wireless communication interface  210  may include at least one antenna array consisting of a plurality of antenna elements. 
     On the hardware side, the wireless communication interface  210  may include a digital unit and an analog unit, and the analog unit may include a plurality of sub-units according to operation power, operation frequency, and the like. The digital unit may be implemented as at least one processor (e.g., a digital signal processor (DSP)). 
     The wireless communication interface  210  transmits and receives the signal as described above. Accordingly, the wireless communication interface  210  may be referred to as a “transmitter” a “receiver,” or a “transceiver.” Further, in the following description, transmission and reception performed through the wireless channel may be used to have a meaning including the processing performed by the wireless communication interface  210  as described above. 
     According to various embodiments of the present disclosure, the wireless communication interface  210  may be omitted for some network entities. For example, the S-GW, MME, or other network entities in a core network may not comprise the wireless communication interface. 
     The backhaul communication interface  220  provides an interface for performing communication with other nodes within the network. That is, the backhaul communication interface  220  converts bitstreams transmitted to another node, for example, another access node, another BS, a higher node, or a core network, from the BS into a physical signal and converts the physical signal received from the other node into the bitstreams. 
     The storage unit  230  stores a basic program, an application, and data such as setting information for the operation of the network device  200 . The storage unit  230  may include a volatile memory, a non-volatile memory, or a combination of volatile memory and non-volatile memory. Further, the storage unit  230  provides stored data in response to a request from the controller  240 . 
     The controller  240  controls the general operation of the network device  200 . For example, the controller  240  transmits and receives a signal through the wireless communication interface  210  or the backhaul communication interface  220 . Further, the controller  240  records data in the storage unit  230  and reads the recorded data. The controller  240  may performs functions of a protocol stack that is required from a communication standard. According to another implementation, the protocol stack may be included in the wireless communication interface  210 . To this end, the controller  240  may include at least one processor. 
     According to exemplary embodiments of the present disclosure, the controller  240  may control and/or manage data flows in a wireless communication network. For example, the controller  240  may control the network device  200  to perform operations according to the exemplary embodiments of the present disclosure. 
       FIG.  3    illustrates the terminal in the wireless communication system according to various embodiments of the present disclosure. A structure exemplified at  FIG.  3    may be understood as a structure of the terminal  120  or the terminal  130 . The term “-module”, “-unit” or “-er” used hereinafter may refer to the unit for processing at least one function or operation, and may be implemented in hardware, software, or a combination of hardware and software. 
     Referring to  FIG.  3   , the terminal  120  includes a communication interface  310 , a storage unit  320 , and a controller  330 . 
     The communication interface  310  performs functions for transmitting/receiving a signal through a wireless channel. For example, the communication interface  310  performs a function of conversion between a baseband signal and bitstreams according to the physical layer standard of the system. For example, in data transmission, the communication interface  310  generates complex symbols by encoding and modulating transmission bitstreams. Also, in data reception, the communication interface  310  reconstructs reception bitstreams by demodulating and decoding the baseband signal. In addition, the communication interface  310  up-converts the baseband signal into an RF band signal, transmits the converted signal through an antenna, and then down-converts the RF band signal received through the antenna into the baseband signal. For example, the communication interface  310  may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. 
     Further, the communication interface  310  may include a plurality of transmission/reception paths. In addition, the communication interface  310  may include at least one antenna array consisting of a plurality of antenna elements. In the hardware side, the wireless communication interface  210  may include a digital circuit and an analog circuit (for example, a radio frequency integrated circuit (RFIC)). The digital circuit and the analog circuit may be implemented as one package. The digital circuit may be implemented as at least one processor (e.g., a DSP). The communication interface  310  may include a plurality of RF chains. The communication interface  310  may perform beamforming. 
     The communication interface  310  transmits and receives the signal as described above. Accordingly, the communication interface  310  may be referred to as a “transmitter,” a “receiver,” or a “transceiver.” Further, in the following description, transmission and reception performed through the wireless channel is used to have a meaning including the processing performed by the communication interface  310  as described above. 
     The storage unit  320  stores a basic program, an application, and data such as setting information for the operation of the terminal  120 . The storage unit  320  may include a volatile memory, a non-volatile memory, or a combination of volatile memory and non-volatile memory. Further, the storage unit  320  provides stored data in response to a request from the controller  330 . 
     The controller  330  controls the general operation of the terminal  120 . For example, the controller  330  transmits and receives a signal through the communication interface  310 . Further, the controller  330  records data in the storage unit  320  and reads the recorded data. The controller  330  may performs functions of a protocol stack that is required from a communication standard. According to another implementation, the protocol stack may be included in the communication interface  310 . To this end, the controller  330  may include at least one processor or microprocessor, or may play the part of the processor. Further, the part of the communication interface  310  or the controller  330  may be referred to as a communication processor (CP). 
     According to exemplary embodiments of the present disclosure, the controller  330  may perform operations associated with controlling and/or managing of data flows by the network device  200 . For example, the controller  330  may control the terminal to perform operations according to the exemplary embodiments of the present disclosure. 
       FIG.  4    illustrates the communication interface in the wireless communication system according to various embodiments of the present disclosure.  FIG.  4    shows an example for the detailed configuration of the communication interface  210  of  FIG.  2    or the communication interface  310  of  FIG.  3   . More specifically,  FIG.  4    shows elements for performing beamforming as part of the communication interface  210  of  FIG.  2    or the communication interface  310  of  FIG.  3   . 
     Referring to  FIG.  4   , the communication interface  210  or  310  includes an encoding and circuitry  402 , a digital circuitry  404 , a plurality of transmission paths  406 - 1  to  406 -N, and an analog circuitry  408 . 
     The encoding and circuitry  402  performs channel encoding. For the channel encoding, at least one of a low-density parity check (LDPC) code, a convolution code, and a polar code may be used. The encoding and circuitry  402  generates modulation symbols by performing constellation mapping. 
     The digital circuitry  404  performs beamforming for a digital signal (for example, modulation symbols). To this end, the digital circuitry  404  multiples the modulation symbols by beamforming weighted values. The beamforming weighted values may be used for changing the size and phrase of the signal, and may be referred to as a “precoding matrix” or a “precoder.” The digital circuitry  404  outputs the digitally beamformed modulation symbols to the plurality of transmission paths  406 - 1  to  406 -N. At this time, according to a multiple input multiple output (MIMO) transmission scheme, the modulation symbols may be multiplexed, or the same modulation symbols may be provided to the plurality of transmission paths  406 - 1  to  406 -N. 
     The plurality of transmission paths  406 - 1  to  406 -N convert the digitally beamformed digital signals into analog signals. To this end, each of the plurality of transmission paths  406 - 1  to  406 -N may include an inverse fast Fourier transform (IFFT) calculation unit, a cyclic prefix (CP) insertion unit, a DAC, and an up-conversion unit. The CP insertion unit is for an orthogonal frequency division multiplexing (OFDM) scheme, and may be omitted when another physical layer scheme (for example, a filter bank multi-carrier: FBMC) is applied. That is, the plurality of transmission paths  406 - 1  to  406 -N provide independent signal processing processes for a plurality of streams generated through the digital beamforming. However, depending on the implementation, some of the elements of the plurality of transmission paths  406 - 1  to  406 -N may be used in common. 
     The analog circuitry  408  performs beamforming for analog signals. To this end, the digital circuitry  404  multiples the analog signals by beamforming weighted values. The beamformed weighted values are used for changing the size and phrase of the signal. More specifically, according to a connection structure between the plurality of transmission paths  406 - 1  to  406 -N and antennas, the analog circuitry  408  may be configured in various ways. For example, each of the plurality of transmission paths  406 - 1  to  406 -N may be connected to one antenna array. In another example, the plurality of transmission paths  406 - 1  to  406 -N may be connected to one antenna array. In still another example, the plurality of transmission paths  406 - 1  to  406 -N may be adaptively connected to one antenna array, or may be connected to two or more antenna arrays. 
     In a long term evolution (LTE) system, bearers known as Evolved Packet switched System (EPS) bearers are provided which provide a 1:1 mapping between the User Equipment (UE) or mobile device and the Evolved Packet Core (EPC) at the heart of the network by means of a Data Radio Bearer (DRB). This is illustrated in  FIG.  5 ( a )  which illustrates the 1:1 mapping between EPS bearers and DRBs referred to. 
     In a new radio (NR) system, the 1:1 mapping has been replaced with a model based on Quality of Service (QoS) flows, which are part of a Protocol Data Unit (PDU) session. The Radio Access Network (RAN) is responsible for managing the mapping of the QoS flows to DRBs, as required. Such a scheme is illustrated in  FIG.  5 ( b )  which shows the notion of QoS flows between the UE and the 5G Core Network, via a NR RAN. 
       FIG.  6    shows a slightly more detailed representation of a 4G implementation, similar to that shown in  FIG.  5 ( a ) . Here, there is shown the relationship between the UE, the LTE RAN and the EPC. There is a dedicated DRB per EPS bearer between the UE and the LTE RAB and then a dedicated GTP tunnel per EPS bearer between the LTE RAN and the EPC. 
     This configuration applies to a non-Dual-Connectivity case. 
       FIG.  7    shows the configuration according to an embodiment of the invention in the case of a Dual-Connectivity (DC) implementation. In the case of DC, the radio connection between UE and RAN involves multiple cells (i.e. there is a form of carrier aggregation) and some of these cells are controlled by a Master Node (MN or MeNB in case of LTE) while others are controlled by a Secondary Node (SN or SeNB in case of LTE). The cells controlled by MN are referred to as the Master Cell Group (MCG) while the cells controlled by an SN are referred to as an Secondary Cell Group (SCG). 
     In this case, the UE is in communication with an LTE MeNB and an LTE SeNB, in each case via a DRB per EPS bearer. In this case, data traffic moves between the MeNB and the SeNB. When an EPS bearer is moved from the MeNB to the SeNB, as shown, the MeNB requests from the Mobility Management Entity (MME), a different IP address/DL GTP Tunnel Endpoint Identifier (TEID). The EPC is not aware that this IP address/DL GTP TEID corresponds to a different eNB. Further, one eNB can use different IP addresses. 
       FIG.  8    illustrates the signal flow between UE, MeNB, SeNB, S-GW and MME. This is known from prior art LTE DC operation, but is included for context. 
       FIG.  9    shows a non-DC case in 5G. Here, there is shown a GTP tunnel per PDU session  510 ,  520  between the NR RAN  600  and the 5GCN  500 . Each PDU session  510 ,  520  handles multiple QoS flows, shown by the dotted/dashed lines. Between the NR RAN  600  and the UE  700 , there are DRBs  610 ,  611 ,  612  handling a number of QoS flows of one PDU session. 
     It shows that the QoS flows from a PDU session1  510  are mapped by RAN to two DRBs,  610  and  611 . 
     Embodiments of the invention, in particular, concern the handling of QoS flows upon change of MN (handover), as well as upon addition or change of SN i.e. involving a change of the involved network nodes, which can also be regarded as mobility cases. Some of these aspects however equally apply in non-mobility cases e.g. in case of changes regarding the offloading in case of DC. 
     For these cases, attention is given to the mapping of QoS flows to DRBs, which is a function controlled by the RAN nodes (MN and SN). In particular, different cases—which are referred to as level 1 and level 2 mobility in the following—are distinguished. It should be noted that these mobility levels concern the QoS flow to DRB mapping. i.e. a QoS flow mobility level may occur not involving any actual UE mobility or change of the network node(s) controlling the UEs radio connection. 
     In this case, the RAN  600  maps different QoS flows of a certain PDU session to one or more DRBs. In an embodiment, the RAN maps similar flows together on a DRB. Similar flows in this context can mean data flows having similar QoS requirements e.g. similar latency requirements, for instance. Other means of grouping can be implemented as required. 
     For each UE, 5GCN  500  establishes one or more PDU sessions and for each UE, the RAN  600  establishes one or more DRBs per PDU session. The RAN  600  maps packets belonging to different PDU sessions to different DRBs. Hence the RAN  600  establishes at least one default DRB for each PDU session. Non-Access Stratum (NAS) level packet filters in the UE and the 5GCN associate UL and DL packets with QoS flows. AS-level mapping rules in the UE and the RAN associate UL and DL QoS flows with DRBs. 
     At NAS level, the QoS flow is the finest granularity of QoS differentiation in a PDU session. A QoS flow is identified within a PDU session by a QoS Flow ID (QFI) carried in an encapsulation header over NG-U. 
     RAN and 5GC ensure quality of service (e.g. reliability and target delay) by mapping packets to appropriate QoS Flows and DRBs. Hence there is a 2-step mapping of IP-flows to QoS flows (NAS) and from QoS flows to DRBs (Access Stratum). 
     At NAS level, a QoS flow is characterised by a QoS profile provided by 5GC to RAN and QoS rule(s) provided by 5GC to the UE. The QoS profile is used by RAN to determine the treatment on the radio interface while the QoS rules dictates the mapping between uplink User Plane traffic and QoS flows to the UE. A QoS flow may either be Guaranteed Bitrate (GBR) or “Non-GBR” depending on its profile. The QoS profile of a QoS flow contains QoS parameters, for instance: 
     For each QoS flow:
         A 5G QoS Identifier (5QI); and,   An Allocation and Retention Priority (ARP).       

     In case of a GBR QoS flow only:
         Guaranteed Flow Bit Rate (GFBR) for both uplink and downlink;   Maximum Flow Bit Rate (MFBR) for both uplink and downlink.       

     In case of Non-GBR QoS only:
         Reflective QoS Attribute (RQA): the RQA, when included, indicates that some (not necessarily all) traffic carried on this QoS flow is subject to reflective quality of service (RQoS) at NAS.       

     At Access Stratum level, the data radio bearer (DRB) defines the packet treatment on the radio interface (Uu). A DRB serves packets with the same packet forwarding treatment. Separate DRBs may be established for QoS flows requiring different packet forwarding treatment. In the downlink, the RAN maps QoS Flows to DRBs based on NG-U marking (QFI) and the associated QoS profiles. In the uplink, the UE marks uplink packets over Uu with the QFI for the purposes of marking forwarded packets to the CN. 
     In the uplink, the RAN may control the mapping of QoS Flows to DRB in two different ways:
         Reflective mapping: for each DRB, the UE monitors the QFI(s) of the downlink packets and applies the same mapping in the uplink; that is, for a DRB, the UE maps the uplink packets belonging to the QoS flows(s) corresponding to the QFI(s) and PDU Session observed in the downlink packets for that DRB. To enable this reflective mapping, the RAN marks downlink packets over Uu with QFI.   Explicit Configuration: besides the reflective mapping, the RAN may configure by RRC an uplink “QoS Flow to DRB mapping”.       

     The UE shall always apply the latest update of the mapping rules regardless of whether it is performed via reflective mapping or explicit configuration. 
     For each PDU session, a default DRB is configured. If an incoming UL packet matches neither an RRC configured nor a reflective “QoS Flow ID to DRB mapping”, the UE shall map that packet to the default DRB of the PDU session. 
     Within each PDU session, it is up to NG-RAN how to map multiple QoS flows to a DRB. The RAN may map a GBR flow and a non-GBR flow, or more than one GBR flow to the same DRB. The timing of establishing non-default DRB(s) between RAN and UE for QoS flow configured during establishing a PDU session can be different from the time when the PDU session is established. It is up to RAN when non-default DRBs are established. 
     In DC, the QoS flows belonging to the same PDU session can be mapped to different bearer types and as a result there can be two different SDAP entities configured for the same PDU session: one for MCG and another one for SCG (for instance when one MCG bearer and one SCG bearer are used for two different QoS flows). 
     In embodiments of the invention, QoS flow mobility is used to describe any mobility of a QoS flow, such as moving a QoS flow to another DRB and/or DRB type and/or another eNB. 
     There are various alternatives to manage such QoS flow mobility. In a first alternative, QoS flow mobility may only be achieved at one level i.e. individual QoS flow mobility level i.e. a QoS flow can only be moved from one DRB to another DRB. 
     This is illustrated in  FIG.  10   , where a DRB1  620  handles two QoS flows. QoS flow2 can be moved to a new DRB2  621 , while QoS flow1 is retained on DRB1  620 . Individual QoS flows are moved i.e. their mapping is updated from a source DRB to a target DRB. The source and target DRB may be of any type, such as MCG, SCG, split or can belong to different eNBs. 
     The source DRB may be released at the same time as the QoS flow moves, if no other QoS flows are remaining on the DRB, and the target DRB may be established at the same time as the QoS flow moves, if no other QoS flows are already using the target DRB. 
     In this particular example, DRBs are not moved and the type of bearer does not change. In other words, bearers are established (with a certain type) and released and have QoS flows mapped to them. 
     In a second alternative, QoS flow mobility can be achieved at two levels: 
     a DRB may be moved from one DRB type or eNB to another DRB type or eNB (Level 1) 
     a QoSflow can be moved from one DRB to another DRB as described in the first alternative above (Level 2). 
     This is illustrated in  FIG.  11   , which shows QoS flow1 and QoS flow2 on DRB1  630  on MeNB1 moving to DRB1  631  on a new MeNB (MeNB2). This is a case involving no change in mapping between QoS flows and DRB. This is shown for the case of handover (i.e. radio connection involves changing a first to a second MeNB). 
     In level 1, DRBs can be moved. For instance, a DRB can be moved from an MeNB to an SeNB (MCG→SCG bearer type change) or any other bearer type change. Alternatively, a DRB can be moved from one MeNB to another MeNB (e.g. at handover) as shown in  FIG.  11   . 
     Additionally, individual QoS flows can be moved from a source DRB to a target DRB (Level 2). 
     In practice, the second mentioned alternative, above, is preferred. This approach includes DRB mobility at Level 1 and QoS flow mobility at Level 2. 
     The table 1 below shows certain features of this approach and assists in fully understanding the features. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Level 2-Individual 
               
               
                   
                 Level 1-DRB Mobility 
                 QoS flow mobility 
               
               
                   
               
             
            
               
                 1. What is 
                 DRB and all QoS flows mapped 
                 One individual 
               
               
                 moved? 
                 to that DRB 
                 QoS flow 
               
               
                 2. From where 
                 Moved from source MeNB/cell to 
                 Moved from 
               
               
                 to where? 
                 target MeNB/cell (handover) 
                 source DRB 
               
               
                   
                 Moved between MeNB/cell and 
                 to target DRB 
               
               
                   
                 SeNB/cell (MCG &lt;-&gt; SCG bearer  
                   
               
               
                   
                 type change) 
                   
               
               
                   
                 Reconfigured from/to MCG bearer 
                   
               
               
                   
                 type to/from MCG-split bearer type 
                   
               
               
                   
                 Conform to LTE + LTE NR 
                   
               
               
                 3. Lossless? 
                 Yes 
                 No 
               
               
                 4. Signalling to 
                 RRC e.g. at handover (i.e, no 
                 UP (reflective QoS 
               
               
                 the UE 
                 reflective QoS) 
                 (FFS)) and RRC 
               
               
                   
                   
                 Control plane 
               
               
                 5. Signalling to 
                 Control plane 
                 and/or user plane 
               
               
                 5G-CN 
                 Concerns groups 1 . . . n QoS flows 
                 Concerns 1 
               
               
                   
                   
                 individual 
               
               
                   
                   
                 QoS flow 
               
               
                   
               
            
           
         
       
     
     In LTE systems, two different handover types are supported: 
     1) Normal—Target eNB understands the configuration of the source eNB and continues with that configuration with potential updates. 
     2) Full configuration handover—Target eNB does not fully understand the Access Stratum (AS) configuration in the source eNB. Target eNB configures a complete new Access Stratum Configuration 
     In NR systems, these two prior art handover types are also assumed to be supported. 
     According to an embodiment of the invention, a normal handover may involve a combination of Level 1 and Level 2 QoS flow mobility as described previously. This is illustrated in  FIG.  12   . Here, on MeNB1, DRB1  630  carries QoS flow1 and QoS flow2 and DRB2  641  carries QoS flow3 and QoS flow 4. At handover to MeNB2, DRB1  640  is moved to DRB1  642 , carrying QoS flow 1 and QoS flow2. DRB2  641  is moved to DRB2  643 , carrying QoS flow 3 and QoS flow4. Then QoS low 4 is moved to DRB3  644 . The original two DRBs on MeNB1 have been moved to 3 DRBs on MeNB2. 
     According to another embodiment of the invention, a full configuration handover is shown in  FIG.  13   . In this type of handover, the full AS configuration is released. As a result, all DRBs, as well as the QoS flow→DRB mapping is released. As such, DRBs in the target eNB are new DRBs, (i.e. not continued, no PDCP re-establishment). As a result, the target eNB indicates how to map the different QoS flows to the new DRBs based on level 1 QoS mobility flow only. 
     In  FIG.  13   , there is shown MeNB1 with DRB1  650 , DRB2  651  and DRB3  652 . DRB1  650  carried QoS flow1 and QoS flow2; DRB2  651  carries QoS flow3; and DRB3  652  carries QoS flow4. At handover to MeNB2, New DRB1  653  carries QoS flow1 and New DRB2  654  carries QoS flow2, QoS flow3 and QoS flow4. 
     During handover, it is necessary to consider the issue of Xn forwarding. In particular, it is useful to consider if it would it make sense to have all data forwarding in DRB specific GTP tunnels at handover as in prior art LTE systems. 
     a) Packets that are already assigned a PDCP SN and for which a retransmission may be required in target eNB, are forwarded with a drb-id marking (e.g. drb id or drb specific tunnel), or at least an identity with which the target eNB can derive the drb-id. 
     This only if the concerned DRB is continued in the target eNB 
     b) For DL packets that have not been transmitted yet, it is sufficient to forward them with QoS flow id (i.e. no DRB specific marking/tunneling): the target eNB can perform mapping to DRB. 
     Note that if per-DRB tunnelling/forwarding is active, it is possible that packets of type b), above, would be forwarded in a tunnel for DRB1, but actually the target eNB quickly remaps this QoS flow and the end result is that they are handled on a different DRB2. 
     Also considering that embodiments will have a tunnel per PDU session, it is possible to also have per-PDU session tunnels on Xn at handover. 
     The following approach is followed for all handover options described herein: 
     On Xn at handover there is a tunnel per PDU session 
     For packets for which transmission has been attempted in the source, if the concerned DRB is continued at the target eNB, forwarded PDU will contain: 
     FORMAT 1: GTP header (identifying PDU session), QOS flow id, PDCP SN, IP packet 
     For packets for which transmission has not been attempted in the source, forwarded PDU will contain: 
     FORMAT 2: GTP header (identifying PDU session), QOS flow id, IP packet 
     In LTE, the target eNB can configure, per-DRB, whether packets should be forwarded or not. In NR this type of configuration may be performed per QOS flow. 
     However, if a DRB with RLC-AM is continued, since it is not desirable to have holes in the PDCP SN, the concerning DL packets should be forwarded anyway. 
     As a result, the following forwarding behaviour for a normal (non-full-configuration) handover will apply as a table 2: 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
                 Packets 
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 already 
                   
                 QoS flow 
                   
                   
               
               
                   
                 trans- 
                   
                 forward- 
                   
                   
               
               
                   
                 mitted 
                 DRB 
                 ing 
                 Forwarded 
                   
               
               
                   
                 in source 
                 continued? 
                 requested 
                 packets 
                 Comment 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 Y 
                 Y 
                 Does not 
                 FORMAT 
                 Note concerns all QOS 
               
               
                   
                   
                   
                 matter 
                 1 
                 flows mapped to this 
               
               
                   
                   
                   
                   
                   
                 DRB in the source eNB 
               
               
                   
                   
                   
                   
                   
                 i.e. this may concern 
               
               
                   
                   
                   
                   
                   
                 packets of QOS flows 
               
               
                   
                   
                   
                   
                   
                 mapped to other DRB’s 
               
               
                   
                   
                   
                   
                   
                 in target eNB, or  
               
               
                   
                   
                   
                   
                   
                 packets of QOS flows  
               
               
                   
                   
                   
                   
                   
                 that are not continued  
               
               
                   
                   
                   
                   
                   
                 in target eNB 
               
               
                 2 
                 Y 
                 N 
                 Does not 
                 No 
                 FORMAT 1 not 
               
               
                   
                   
                   
                 matter 
                 forwarding 
                 applicable in this case 
               
               
                 3 
                 N 
                 Does not 
                 Y 
                 FORMAT 
                   
               
               
                   
                   
                 matter 
                   
                 2 
                   
               
               
                 4 
                 N 
                 Does not 
                 N 
                 No 
                   
               
               
                   
                   
                 matter 
                   
                 forwarding 
               
               
                   
               
            
           
         
       
     
     In the case of a full configuration handover, the following forwarding behaviour applies as a table 3: 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                   
                 QoS flow 
                   
               
               
                   
                   
                 Packets already 
                 forwarding 
                 Forwarded 
               
               
                   
                   
                 transmitted in source 
                 requested 
                 packets 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 Y 
                 Does not matter 
                 No forwarding 
               
               
                   
                 3 
                 N 
                 Y 
                 FORMAT 2 
               
               
                   
                 4 
                 N 
                 N 
                 No forwarding 
               
               
                   
                   
               
            
           
         
       
     
     The following table 4 illustrates three different handover examples, focusing on QoS flows. Examples 1 and 2 relate to normal handover, while example 3 is a full configuration handover. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                 Forwarding 
                   
                   
               
               
                   
                   
                   
                 requested 
                   
                   
               
               
                   
                 Source 
                 Target 
                 for QOS 
                 Forwarding 
                   
               
               
                   
                 config 
                 config 
                 flows 
                 behaviour 
                 Notes 
               
               
                   
               
             
            
               
                 1. 
                 DRB1: 
                 DRBI: 
                 1,2,3,4,5,6 
                 DRB1: 
                 QOS flow 1,2,4: Forwarding 
               
               
                   
                 QOS 
                 QOS 
                   
                 Outstanding 
                 and continuation on same radio 
               
               
                   
                 flows 1,2 
                 flows 
                   
                 packets with 
                 bearer (loss/insequence)| 
               
               
                   
                 DRB2: 
                 1,2,3 
                   
                 FORMAT1 
                 QOS flow 3: 
               
               
                   
                 QOS 
                 DRB2: 
                   
                 DRB2: 
                 Retransmission from source in 
               
               
                   
                 flows 3,4 
                 QOS 
                   
                 Outstanding 
                 target will still occur on DRB2; 
               
               
                   
                 DRB3: 
                 flows 4,5 
                   
                 packets with 
                 New tx on DRB1. Lossless, but 
               
               
                   
                 QOS 
                   
                   
                 FORMAT1 
                 might have some out of 
               
               
                   
                 flows 5,6 
                   
                   
                 QOS Flow 
                 sequence delivery during 
               
               
                   
                   
                   
                   
                 1,2,3,4,5,6: 
                 handover. 
               
               
                   
                   
                   
                   
                 Non-txed 
                 QOS flow 5: 
               
               
                   
                   
                   
                   
                 packets with 
                 Potential packet loss due to 
               
               
                   
                   
                   
                   
                 FORMAT2 
                 release of DRB3 (no retx of  
               
               
                   
                   
                   
                   
                   
                 outstanding packets in source 
               
               
                   
                   
                   
                   
                   
                 eNB). New tx on DRB2 
               
               
                   
                   
                   
                   
                   
                 QOS flow 6: 
               
               
                   
                   
                   
                   
                   
                 Released. Also no 
               
               
                   
                   
                   
                   
                   
                 retransmissions of outstanding 
               
               
                   
                   
                   
                   
                   
                 packets in source due to DRB3 
               
               
                   
                   
                   
                   
                   
                 release. 
               
               
                 2 
                 DRB1: 
                 DRB1: 
                 1,3 
                 DRB1: 
                 QOS flow 1,3: 
               
               
                   
                 QOS 
                 QOS 
                   
                 Outstanding 
                 Forwarding and continuation 
               
               
                   
                 flows 1,2 
                 flows 1,2 
                   
                 packets with 
                 on same radio bearer 
               
               
                   
                 DRB2: 
                 DRB2: 
                   
                 FORMAT1 
                 (loss/insequence) 
               
               
                   
                 QOS 
                 QOS 
                   
                 DRB2: 
                 QOS flow 2: 
               
               
                   
                 flows 3,4 
                 flows 3 
                   
                 Outstanding 
                 Continues on DRB2 but some 
               
               
                   
                   
                   
                   
                 packets with 
                 loss may occur due to no 
               
               
                   
                   
                   
                   
                 FORMAT1 
                 forwarding 
               
               
                   
                   
                   
                   
                 QOS Flow 
                 QOS flow 4: 
               
               
                   
                   
                   
                   
                 1,3: 
                 Discontinued, but since DRB2 
               
               
                   
                   
                   
                   
                 Non-txed 
                 is continued in target eNB, still 
               
               
                   
                   
                   
                   
                 packets with 
                 some retransmission of 
               
               
                   
                   
                   
                   
                 FORMAT2 
                 outstanding packets in source 
               
               
                   
                   
                   
                   
                   
                 eNB of QOS flow 4 may 
               
               
                   
                   
                   
                   
                   
                 happen in target eNB on DRB2 
               
               
                 3. 
                 DRB1: 
                 New 
                 1,2 
                 QOS Flow 
                   
               
               
                   
                 QOS 
                 DRB1: 
                   
                 1,2: 
                   
               
               
                   
                 flows 1,2 
                 QOS 
                   
                 Non-txed 
                   
               
               
                   
                 DRB2: 
                 flows 1,2 
                   
                 packets with 
                   
               
               
                   
                 QOS 
                 New 
                   
                 FORMAT2 
                   
               
               
                   
                 flows 3,4 
                 DRB2: 
                   
                   
                   
               
               
                   
                   
                 QOS 
                   
                   
                   
               
               
                   
                   
                 flows 3,4 
               
               
                   
               
            
           
         
       
     
     In LTE, there is one end-marker-packet per DRB from the CN. In NR, since the CN is not aware of QOS-flow→DRB mapping, there is one end-marker-packet per QOS flow. This results in slightly updated target-eNB behaviour in NR i.e. when an end-marker-packet for a certain QOS flow is received by the target eNB, this does not mean that all traffic received from the CN for that DRB can be transmitted. i.e. only DL traffic belonging to that QOS flow can be transmitted. 
       FIG.  14    illustrates an example configuration where the MeNB decides to move one complete PDU session to the SeNB. As such, it moves one tunnel endpoint in a manner similar to that described in relation to  FIG.  7   . This is functionally similar to (or the same as) moving all EPS bearers of one PDU connection from MeNB to SeNB in EPC. 
     However, this approach has certain disadvantages in that it does not allow the MeNB to move only some QoS flows to the SeNB. For instance, assume that a PDU session is handling a voice call and best effort data. The MeNB might wish to move the best effort data to the SeNB while keeping the voice call on the MeNB. This would not be possible with this approach. In practice, this approach may have limited utility. 
       FIG.  15    shows an alternative configuration according to an embodiment of the invention. Here, the MeNB requests the 5G-CN to establish a second backhaul tunnel for the same PDU session. Here, only part of the QoS flows of a PDU session are offloaded to/terminated at an SN. i.e. the CN splits the traffic associated with a PDU session using a separate tunnel to each involved RAN node. 
     This is illustrated by PDU session 2-a and PDU session 2-b. This second tunnel has a different IP address/TEID, corresponding to the SeNB. The other PDU session 2-a is routed via the MeNB still. In this way, two parallel tunnels are established for one PDU session. 
     Next, the MeNB asks the 5G-CN to move certain QoS flows from tunnel 2-a to tunnel 2-b. In this case, i.e. RAN connected to 5G-CN, the smallest level of granularity known to the RAN is the QoS flow. The signalling required to manage and coordinate this process could be in the Control Plane or in the User Plane. 
     Unlike the previous embodiment of  FIG.  14   , the embodiment of  FIG.  15    represents a more practical solution in most circumstances. 
     It is assumed that NR DC architecture is applicable for cases of RAN DC connected to 5G-CN. This is as shown in  FIG.  15   . The new QoS architecture is applicable to the following DC cases: MeNB NR+SeNB NR; MeNB eLTE+SeNB NR; MeNB NR+SeNB eLTE; and MeNB eLTE+SeNB eLTE. 
     If the RAN is connected to the EPC, the legacy LTE DC architecture is assumed to be applicable. This is as shown in  FIG.  7   . The types of DC which legacy QoS architecture are applicable are: MeNB LTE+SeNB LTE; and MeNB LTE+SeNB NR. 
     According to the previous description, it is possible to split a PDU session at the CN level, it is reasonable to consider if it is still useful to support split bearers in the NR+NR DC case. 
     This is illustrated in  FIG.  16   , which shows NR+NR DC, with a split DRB as indicated by the connection between the MeNB and SeNB. Here, a RAN node splits the traffic carried by a DRB between MCG and SCG. I.e. some packets use the MCG leg while others are carried by the SCG leg. Furthermore, the traffic of a QoS flow is carried across both legs i.e. the RAN split may be QoS flow agnostic. The figure also shows that some QoS flows may be mapped to a DRB only using the MCG or SCG leg. 
     It transpires that split bearers are still useful because PDU session splitting at the 5G-CN level as described does not allow lossless move of QoS from MeNB to SeNB, since there is no common SN. Further, it does not allow aggregation of MeNB+SeNB resources for one QoS flow. As such, split bearers are useful and can still play a valuable role in network planning and configuration. 
     Previously, Xn forwarding at handover has been described using PDU session tunnels with the following PDU formats: 
     FORMAT 1: GTP header (identifying PDU session), QOS flow id, PDCP SN, IP packet 
     FORMAT 2: GTP header (identifying PDU session), QOS flow id, IP packet 
     There are two options for handling the transport of the split bearer in NR+NR DC: 
     Option 1: PDU session tunnelling 
     Also have per-PDU session tunnelling for this case, and define a 3rd format: 
     FORMAT 3: 
     GTP header (identifying PDU session), DRB-ID, PDCP SN, Compressed/Ciphered IP packet 
     QOS flow not so needed in DL (mapping to DRB already done) 
     QOS flow not available in UL (PDCP and higher layers in MeNB) 
     Option 2: DRB level tunnelling 
     Alternatively, provide DRB specific tunnels (like in LTE) only for this split bearer case: 
     Since packets below PDCP are involved, the PDCP PDUs forwarded between eNBs are primarily part of a bearer. Accordingly it may be possible to have tunnels per-DRB as in LTE. 
     An issue that arises in embodiments of the invention is to do with responsibility for managing DRB/QoS flow. In LTE, there is one DRB per EPS bearer/E-RAB. The MeNB is responsible for DRB type determination, DRB establishment and DRB release. In other words, the MeNB decides which DRBs are to be established whether they are of type MCG, SCG or split. In the case of SCG or split, the MeNB asks the SeNB to support establishment of the required DRBs. In this case, the SeNB performs Call Admission Control (CAC). If the SeNB accepts, it provides the detailed radio configuration for the SCG (RLC and lower) to SeNB, which the MeNB transmits to the UE. 
     In NR systems, however, the RAN has more flexibility and/or responsibility with respect to DRB creation. In NR, the RAN can decide whether to multiplex or not flows of the same PDU session on one DRB. Decisions of this sort are decided by a new layer, known as Access Stratum Mapping layer (ASML) 
     ASML can be configured as a separate protocol layer or, alternatively, can be set up as a sub-layer part of PDCP. 
     In the case of LTE+LTE DC, the MeNB is responsible for DRB management (i.e. setup and release) of DRBs. The same approach is adopted in enabling DRB mobility, such as moving a bearer from MCG to SCG type. 
     In the case of NR+NR DC, the MeNB is responsible for management (setup/type change/release) of all DRBs to the UE i.e. MCG, MCG-split and SCG bearers. 
     It is assumed that it is not generally desirable to allow the ASML layer in the SeNB to be autonomously responsible for mapping QoS flows to DRBs. In order to ensure that QoS flows can be handled without loss when moved between SeNB and MeNB, it is important to have the same QoS flow→DRB mapping in both MeNB and SeNB i.e. in such a case, a DRB move rather than an individual QoS flow move can be executed. 
     If two different entities start to independently determine the QoS flow→DRB mapping, then the possibilities for lossless mobility will decrease. 
     It should be noted that in NR+NR DC, the MeNB control the QoS flow→DRB mapping in both the MeNB and SeNB i.e. for mapping to any DRB type. 
       FIG.  17    shows an embodiment of the present disclosure, highlighting the ASML layer, which is particularly involved in mapping QoS flows to DRBs. Here can be seen the Master ASML, running in the NR MeNB. In the Control Plane, it is responsible for all DRB management, in both the MeNB and the SeNB. It is also responsible for all QoS flow→DRB mapping control, in both the master and slave ASML, running in MeNB and SeNB respectively. 
     In the User Plane, it performs mapping of QoS flows to DRBs for MCG and MCG-split DRBs. 
     The Slave ASML, running in the SeNB, in the User Plane, performs mapping of QoS flows to DRBs for SCG DRBs. 
     It should be noted that responsibilities for MeNB and SeNB with respect to DRB management are the same in LTE+LTE DC as in NR+NR DC, with the addition of the ASML layer. 
     The table 5 below summarises the situation: 
     
       
         
           
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                 MCG 
                 MCG Split 
                 SCG 
               
               
                   
                 Bearer 
                 Bearer 
                 Bearer 
               
               
                   
               
             
            
               
                 1. Responsibility for DRB 
                 MeNB 
                 MeNB 
                 MeNB 
               
               
                 management (establishment, release, 
                   
                   
                   
               
               
                 modification) 
                   
                   
                   
               
               
                 2. Responsibility for ASML mapping 
                 MeNB 
                 MeNB 
                 MeNB 
               
               
                 configuration (only for NR + NR DC) 
                   
                   
                   
               
               
                 3. Responsibility for PDCP 
                 MeNB 
                 MeNB 
                 SeNB* 
               
               
                 configuration 
                   
                   
                   
               
               
                 4. Responsibility for lower layer 
                 MeNB 
                 MeNB + 
                 SeNB* 
               
               
                 configuration (RLC, MAC, L1) 
                   
                 SeNB 
               
               
                   
               
            
           
         
       
     
     Note that for the entries labelled SeNB*, the SeNB no longer receives a QCI for an SCG DRB, but a set of QoS profiles (belonging to the QoS flows mapped to the DRB) that have to be supported by the DRB. The SeNB takes these QoS profiles into account when configuring the lower layers. 
     The mapping of QoS flows (i.e. indicating which DRB is used for transferring packets) can either be explicitly signalled, or a ‘reflective’ approach can be taken whereby a signal header includes the QoS flow information. 
       FIGS.  18  to  20    illustrate signal flows associated with various embodiments and illustrative examples described previously. 
       FIG.  18    shows a signal flow associated with an MCG bearer→SCG bearer move at SeNB additions. This is an example of Level 1 mobility. 
       FIG.  19    illustrates an example of Level 2 mobility, with the movement of an additional QoS flow to the SeNB. 
       FIG.  20    shows an example of Level 2 mobility in the User Plane, To enable quick QoS flow switching between MeNB and SeNB, inband UP switching may be used over NG. 
     This could, for instance, be used in a situation after execution of signalling sequence shown in  FIG.  19    to move QoS flow3 hack to the MeNB. 
     It could also be used if, for instance, at the SeNB addition step, the SeNB is prepared (e.g. DRBs pre-established) for a number of QoS flows, even though these flows are not yet moved to the SeNB. 
     A potential problem may arise If the DL packet on the new DRB arrives earlier at the UE than the last retransmission of a packet on the old DRB. In this case, the UE may ping-pong back the QoS-flow to the old DRB. This is because of reflective QoS i.e. the UE adjusting the QoS flow to DRB mapping it uses in the uplink is based on the packets it receives in the downlink. In other words, if the UE receives a packet of a given QoS flow on another DRB than the DRB previously used, it may update the QoS flow to DRB mapping i.e. it may use the DRB newly used in the downlink for transmission of subsequent packets of the concerned QoS flow in the uplink. 
     This could happen e.g. at handover. As an example, consider a Source has 3 DRB&#39;s: 
     DRB1: QoS flow 1, 2, 3 
     DRB2: QoS flow 4,5 
     DRB3: QoS flow 6 
     Assume that the target MeNB does not like the mapping of QoS flows 1, 2, 3 and wants to handle QoS flow 3 at a separate DRB. Then, the target eNB would signal the following configuration: 
     Continue DRB 1, 2, 3 (automatically moves QoS flows with it, if no additional QOS flow moves are configured) 
     Establish DRB4 
     Move QOS flow 3 to DRB4 
     The Target MeNB will receive packets for QOS flow 3 as part of DRB1 forwarding (FORMAT1 only for QOS flow 3), and as FORMAT2 packets which should be transmitted on DRB2 in the target eNB. If the Target eNB starts immediately to send packets on DRB2, while the retransmissions on DRB1 are still ongoing, the following may happen: 
     The UE receives a packet for QOS flow 3 on DRB2. It updates its UL mapping and sends UL packets for QOS flow 3 on DRB2. 
     Next, the UE receives a packet for QOS flow 3 on DRB1 (retrans). The UE again updates its mapping and sends UL packets for QOS flow 3 on DRB1. 
     Next, the UE receives a DL packet for QOS flow3 on DRB2 and so on. 
     Note that the same problem may exist even if we have the QOSflow→DRB mapping signalled in the CP at handover i.e. subsequent re-transmissions may cause the UE to map the QoS flow back to the previous DRB (i.e. a pong): 
     The UE receives updated mapping QOSflow3→DRB4 in handover command 
     Next, the UE receives DL packet on DRB1 for QOS flow 3, and the UE updates mapping to DRB1 for QOS flow 3 
     It can be seen from the following that it is possible for synchronisation errors and signalling problems to spiral. 
     One solution to this problem is for the network to ensure that it is not allowed to happen. This can be achieved by: 
     Intra-eNB: Wait for transmitting the packet on the new DRB until in-sequence delivery of relevant PDCP PDU&#39;s on old DRB has been confirmed by RLC. 
     Handover: Same behaviour as intra-eNB, above, but the target eNB ensures this 
     Inter-MeNB/SeNB: This configuration renders it more difficult to guarantee. i.e. the MeNB would have to stop DL transmission on MCG bearer, wait until delivery confirmation (discard all DL packets that arrive in the mean time assuming no forwarding), and only after RLC confirmation, inform CN to route via SeNB. 
     Another solution is to use inband “Packet subject to reflective QOS” marker. i.e. only set it for some packets on the new DRB and not set it for the last packets on the previous DRB. This may only result in some out of sequence delivery to higher layers, but no UL QOS flow routing ping pong or back and forth. 
     The preferred option would appear to be the second solution presented above, which also works in combination with CP signalling, e.g.: 
     Target eNB signals in handover command flow has to move from DRB1 to DRB2 
     Immediately after handover: 
     UL: UE only routes packets on DRB2. 
     DL: UE may receive (even in parallel) some packets (late retrans) over DRB1 (no inband indicator) and rest over DRB2 (with inband indicator) 
     According to various embodiments of the present disclosure, a method of managing a data flow in a wireless communication system comprises controlling a quality of service (QoS) flow to be transferred from a first data radio bearer (DRB) to a second DRB. Herein the QoS flow is a flow of data carried by a DRB between a terminal and at least one network entity. 
     According to various embodiments of the present disclosure, a plurality of QoS flows of the terminal are routed via at least two network entities sequentially, simultaneously, or a combination of both. 
     According to various embodiments of the present disclosure, at least one QoS flow of the terminal is handed from a first network entity to a second network entity. 
     According to various embodiments of the present disclosure, the QoS flow is transferred individually while at least one other QoS flow is maintained in the first DRB. 
     According to various embodiments of the present disclosure, the first DRB is a source DRB, and the second DRB is a target DRB. 
     According to various embodiments of the present disclosure, the QoS flow is transferred along with at least one other QoS flow from the first DRB to the second DRB. 
     According to various embodiments of the present disclosure, the QoS flow and the at least one other QoS flow are transferred: 
     from a source master node (MN) or cell to a target MN or cell; 
     between a MN or cell and a secondary node (SN) or cell; 
     from a master cell group (MCG) bearer type to MCG-split bearer type; or 
     to conform to long term evolution (LTE) and LTE-new radio (NR). 
     According to various embodiments of the present disclosure, the transferring of the QoS flow is associated with a handover from a source eNB to a target eNB. Herein, the handover is a normal handover where a configuration in the source eNB is available for the target eNB, or a full configuration handover where the target eNB configures a new access stratum configuration. 
     According to various embodiments of the present disclosure, the target MN or cell determines whether to maintain or change QoS flow to DRB mapping. 
     According to various embodiments of the present disclosure, the MN determine whether to offload at least one QoS flow of a packet data unit (PDU) session to an SN and requesting to transfer the QoS flow. 
     According to various embodiments of the present disclosure, the MN offloads all QoS flows mapped to the associated DRB to an SN. 
     According to various embodiments of the present disclosure, upon transferring a QoS flow from a first network entity to a second network entity, data packets are forwarded from the first network entity to the second network entity. 
     According to various embodiments of the present disclosure, a method of managing a data flow in a wireless communication network comprises generating a first backhaul tunnel between a network entity and a first node. Herein, a first backhaul tunnel is established between the network entity and a second node, the first backhaul tunnel is associated with a packet data unit (PDU) session and the second backhaul tunnel is associated with the PDU session, and the network entity operates in a dual connectivity configuration where a communication between a terminal and the network entity is performed over the first node and the second node. 
     At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as ‘component’, ‘module’ or ‘unit’ used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of others. 
     Furthermore, embodiments of the invention may be defined in terms of methods, corresponding apparatus or devices and programs for computers. 
     Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. 
     All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
     Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
     The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
     Methods according to embodiments stated in claims and/or specifications of the present disclosure may be implemented in hardware, software, or a combination of hardware and software. 
     When the methods are implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium may be configured for execution by one or more processors within the electronic device. The at least one program may include instructions that cause the electronic device to perform the methods according to various embodiments of the present disclosure as defined by the appended claims and/or disclosed herein. 
     The programs (software modules or software) may be stored in non-volatile memories including a random access memory and a flash memory, a read only memory (ROM), an electrically erasable programmable read only memory (EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other type optical storage devices, or a magnetic cassette. Alternatively, any combination of some or all of the may form a memory in which the program is stored. Further, a plurality of such memories may be included in the electronic device. 
     In addition, the programs may be stored in an attachable storage device which is accessible through communication networks such as the Internet, Intranet, local area network (LAN), wide area network (WAN), and storage area network (SAN), or a combination thereof. Such a storage device may access the electronic device via an external port. Further, a separate storage device on the communication network may access a portable electronic device. 
     In the above-described detailed embodiments of the present disclosure, a component included in the present disclosure is expressed in the singular or the plural according to a presented detailed embodiment. However, the singular form or plural form is selected for convenience of description suitable for the presented situation, and various embodiments of the present disclosure are not limited to a single element or multiple elements thereof. Further, either multiple elements expressed in the description may be configured into a single element or a single element in the description may be configured into multiple elements. 
     While the present disclosure has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be defined as being limited to the embodiments, but should be defined by the appended claims and equivalents thereof. 
     Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.