This application is the U.S. national phase of International Application No. PCT/KR2018/009275 filed Aug. 13, 2018 which designated the U.S. and claims priority to IN Patent Application No. 201741028700 filed August 11, 2017, IN Patent Application No. 201741028922 filed Aug. 14, 2017, and IN Patent Application No. 201842030025 filed Aug. 9, 2018, the entire contents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a wireless communication network. More particularly it is related to a method and system for bearer type change of a plurality of radio bearers configured for a User Equipment (UE).

BACKGROUND ART

In the recent years several broadband wireless technologies have been developed to meet the growing number of broadband subscribers and to provide more and better applications and services. The second generation wireless communication system has been developed to provide voice services while ensuring the mobility of users. Third generation wireless communication system supports not only the voice service but also data service. In recent years, the fourth wireless communication system has been developed to provide high-speed data service. However, currently, the fourth generation wireless communication system suffers from lack of resources to meet the growing demand for high speed data services. So fifth generation wireless communication system is being developed to meet the growing demand for high speed data services, support ultra-reliability and low latency applications.

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. The 5G or pre-5G communication system is also called a ‘beyond 4G network’ or a ‘post long term evolution (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, beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large scale antenna techniques are discussed with respect to 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 frequency shift keying (FSK) and Feher's quadrature amplitude 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.

The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of everything (IoE), which is a combination of the IoT technology and the big data processing technology through connection with a cloud server, has emerged.

As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “security technology” have been demanded for IoT implementation, a sensor network, a machine-to-machine (M2M) communication, machine type communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing information technology (IT) and various industrial applications.

In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, MTC, and M2M communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud RAN as the above-described big data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.

As described above, various services can be provided according to the development of a wireless communication system, and thus a method for easily providing such services is required.

The fifth generation wireless communication system will be implemented not only in lower frequency bands but also in higher frequency (mm Wave) bands, e.g., 10 GHz to 100 GHz bands, so as to accomplish higher data rates. To mitigate 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 being considered in the design of fifth generation wireless communication system. In addition, the fifth generation wireless communication system is expected to address different use cases having quite different requirements in terms of data rate, latency, reliability, mobility etc. However, it is expected that the design of the air-interface of the fifth generation wireless communication system would be flexible enough to serve the UEs having quite different capabilities depending on the use case and market segment the UE cater service to the end customer. Few example use cases the fifth generation wireless communication system wireless system is expected to address is enhanced Mobile Broadband (eMBB), massive Machine Type Communication (m-MTC), ultra-reliable low latency communication (URLL) etc. The eMBB requirements like tens of Gbps data rate, low latency, high mobility so on and so forth address the market segment representing the conventional wireless broadband subscribers needing internet connectivity everywhere, all the time and on the go. The m-MTC requirements like very high connection density, infrequent data transmission, very long battery life, low mobility address so on and so forth address the market segment representing the Internet of Things (IoT)/Internet of Everything (IoE) envisioning connectivity of billions of devices. The URLL requirements like very low latency, very high reliability and variable mobility so on and so forth address the market segment representing the Industrial automation application, vehicle-to-vehicle/vehicle-to-infrastructure communication foreseen as one of the enabler for autonomous cars.

In the fourth generation wireless communication systems, the UE in a connected state communicates with an Enhanced Node B (eNB). A radio protocol stack for communication between the UE and the eNB comprises of Packet Data Convergence Protocol (PDCP), Radio link control (RLC), a Medium Access Control (MAC) and Physical (PHY) sub layers. One or more data radio bearers (DRBs) are established between the UE and the eNB for exchanging user plane packets. Each DRB is associated with one PDCP entity and one or more RLC entities. Each DRB is associated with a logical channel in the MAC sub layer. There is one MAC entity in the UE for the eNB.

The main services and functions of the MAC sublayer include: mapping between logical channels and transport channels, Multiplexing/de-multiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on the transport channels, scheduling information reporting, error correction through HARQ, priority handling between the logical channels of one UE, priority handling between the UEs by means of dynamic scheduling, transport format selection and padding.

The main services and functions of the RLC sublayer include: transfer of upper layer PDUs, error correction through ARQ (only for Acknowledged Mode (AM) data transfer), concatenation, segmentation and reassembly of RLC SDUs (only for Unacknowledgement Mode (UM) and AM data transfer), re-segmentation of the RLC data PDUs (only for the AM data transfer), reordering of the RLC data PDUs (only for the UM and AM data transfer), duplicate detection (only for the UM and AM data transfer), protocol error detection (only for the AM data transfer), the RLC SDU discard (only for the UM and AM data transfer), and RLC re-establishment.

Functions of the RLC sub layer are performed by the RLC entities. The RLC entity can be configured to perform the data transfer in one of the following three modes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). Consequently, the RLC entity is categorized as a TM RLC entity, an UM RLC entity and an AM RLC entity depending on the mode of data transfer that the RLC entity is configured to provide. The TM RLC entity is configured either as a transmitting TM RLC entity or a receiving TM RLC entity. The transmitting TM RLC entity receives RLC SDUs from an upper layer (i.e. PDCP) and sends RLC PDUs to its peer receiving the TM RLC entity via lower layers (i.e. MAC). The receiving TM RLC entity delivers the RLC SDUs to the upper layer (i.e. PDCP) and receives the RLC PDUs from its peer transmitting the TM RLC entity via the lower layers (i.e. MAC).

Further, the UM RLC entity is configured either as a transmitting UM RLC entity or a receiving UM RLC entity. The transmitting UM RLC entity receives the RLC SDUs from the upper layer and sends the RLC PDUs to its peer receiving UM RLC entity via the lower layers. The receiving UM RLC entity delivers the RLC SDUs to the upper layer and receives the RLC PDUs from its peer transmitting the UM RLC entity via the lower layers. The AM RLC entity consists of a transmitting side and a receiving side. The transmitting side of the AM RLC entity receives the RLC SDUs from the upper layer and sends the RLC PDUs to its peer AM RLC entity via the lower layers. The receiving side of the AM RLC entity delivers the RLC SDUs to the upper layer and receives the RLC PDUs from its peer AM RLC entity via the lower layers.

The main services and functions of the PDCP sublayer for the user plane include: header compression and decompression: ROHC only, transfer of user data, in-sequence delivery of the upper layer PDUs at PDCP re-establishment procedure for RLC AM, For split bearers in the DC (only support for the RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception, duplicate detection of the lower layer SDUs at the PDCP re-establishment procedure for the RLC AM, retransmission of the PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM, ciphering and deciphering, and timer-based SDU discard in an uplink (UL). Functions of the PDCP sub layer are performed by the PDCP entities. Each PDCP entity carries the data of one radio bearer. Due to the UE mobility, the UE may handover from one eNB to another eNB. In dual connectivity (DC) mode of operation due to UE mobility the UE may handover from one MeNB to another MeNB or SCG change from one SeNB to another SeNB. The eNB may support multiple cells and the UE may also handover from one cell to another cell of same eNB.

In the fourth generation wireless communication system like LTE, the X2 based handover between two enhanced node B (eNBs) or base station for AM data radio bearers (DRBs) is lossless.

After the handover, the user plane protocols for the DRBs configured with the RLC layer in the AM mode are handled as follows in a legacy system: a PDCP SN is maintained on a bearer basis; a source eNB informs the target eNB about the next DL PDCP SN to allocate to a packet which does not have a PDCP sequence number yet (either from the source eNB or from a serving gateway); For security synchronization, a Hyper Frame Number (HFN) is also maintained; the source eNB provides to the target one reference HFN for the UL and one for the DL i.e., HFN and corresponding SN; Security keys are refreshed; the UE sends PDCP status report to the target eNB if the PDCP status report is configured by the target eNB. The configuration to send status report is per bearer; the target eNB may send the PDCP status report to the UE and the UE does not need to wait to resume UL transmission; the UE re-transmits in the target eNB or the target cell, all uplink PDCP SDUs starting from the first PDCP SDU following the last consecutively confirmed PDCP SDU i.e., the oldest PDCP SDU that has not been acknowledged at the RLC in the source, excluding the PDCP SDUs of which the reception is acknowledged through the PDCP SN based reporting by the target eNB. The target eNB re-transmits and prioritizes all downlink PDCP SDUs forwarded by the source eNB (i.e., the target eNB should send data with the PDCP SNs from X2 before sending data from S1), with the exception of the PDCP SDUs of which the reception is acknowledged through the PDCP SN based reporting by the UE; the ROHC is reset; and the RLC/MAC is reset. The PDCP PDUs stored in the PDU reordering buffer are deciphered and decompressed and kept in the PDCP, associated with COUNT.

Alternately, after the handover the user plane protocols for DRBs configured with RLC in the UM mode are handled as follows in legacy system: the PDCP SN is reset; the HFN is reset; the security keys are refreshed; No PDCP status report is transmitted; No PDCP SDUs are retransmitted in the target eNB; The UE PDCP entity does not attempt to retransmit any PDCP SDU in the target cell for which transmission had been completed in the source cell. Instead UE PDCP entity starts the transmission with other PDCP SDUs; ROHC is reset; and RLC/MAC is reset. The user plane protocol of LTE from UE perspective is shown inFIG. 1A.

In the fifth generation wireless communication system, the concept of QoS flows replacing the EPS bearer concept in the core network is introduced. This means the user plane between the gNB and the gateway is based on the QoS flow instead of the S1-U bearer in the LTE system. For the particular UE, there can be one or more QoS flows between the gNB and the data gateway depending on the characteristics of the application/service and the QoS handling of the traffic. The EPS bearer handles all the user packets mapped to the EPS bearer with the same QoS. Within the EPS bearer, there is no further differentiated handling of the user plane packets. The QoS flow concept of the 5G system overcomes this drawback of the EPS bearer concept of the LTE system. The packets mapped to the different QoS flows belonging to the UE traffic can be handled differently. To achieve the same differentiated handling in the LTE system, multiple EPS bearers with different QoS parameters need to be created. In the 5G system, all the different QoS flows of the UE are handled by the PDU session between the g/NB and the data gateway. The UE may have more than one PDU session depending on the number of the PDN connections. However, for one PDN connection one PDU session is created. At high level, the PDU session can be analogous with the EPS bearer in the LTE system.

However, on the radio interface, the 5G system has retained the data radio bearer (DRB) concept for user plane handling. This requires that the one or more QoS flows belonging to the PDU session of the UE is mapped to the DRB depending on the QoS requirement. The mapping of the QoS flow to the DRB is done in the RAN node i.e. the gNB within the new user plane protocol layer called SDAP (Service Data Adaptation Protocol) layer which is placed above the PDCP. The SDAP entities are located in the SDAP sublayer. Several SDAP entities may be defined for the UE. There is the SDAP entity configured per cell group for each individual PDU session. The SDAP entity in the SDAP sublayer performs mapping between the QoS flow and the data radio bearer for both the DL and the UL. The user plane protocol of 5G from UE perspective is shown inFIG. 1Brespectively.

Multi-RAT Dual Connectivity (MR-DC) is a generalization of the Intra-E-UTRA Dual Connectivity (DC) described in 3GPP TS 36.300, where a multiple Rx/Tx UE may be configured to utilize radio resources provided by two distinct schedulers in two different nodes connected via non-ideal backhaul, one providing E-UTRA access and the other one providing NR access. One scheduler is located in the MN and the other in the SN. The MN and SN are connected via a network interface and at least the MN is connected to the core network.

As described in 3GPP TS 37.340, E-UTRAN supports MR-DC via E-UTRA-NR Dual Connectivity (EN-DC), in which a UE is connected to one LTE eNB that acts as a MN and one NR gNB that acts as a SN as shown inFIG. 1C. The MN i.e. LTE eNB is connected to the EPC and the SN i.e. NR gNB is connected to the MN i.e. LTE eNB via the Xn interface.

NG-RAN supports NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), in which a UE is connected to one LTE ng-eNB that acts as a MN and one NR gNB that acts as a SN as shown inFIG. 1D. The LTE ng-eNB is connected to the 5G-Core (5GC) and the NR gNB is connected to the MN i.e. LTE ng-eNB via the Xn interface. The LTE ng-eNB is also referred as eLTE eNB.

NG-RAN supports NR-E-UTRA Dual Connectivity (NE-DC), in which a UE is connected to one NR gNB that acts as a MN and one LTE ng-eNB that acts as a SN as shown inFIG. 1E. The NR gNB is connected to 5GC and the LTE ng-eNB is connected to the MN i.e. NR gNB via the Xn interface.

NG-RAN supports also NR-NR Dual Connectivity (NR-NR DC), in which a UE is connected to one NR gNB that acts as a MN and another NR gNB that acts as a SN as shown inFIG. 1F. The MN i.e. NR gNB is connected to 5GC and the SN i.e. NR gNB is connected to the MN i.e. NR gNB via the Xn interface.

In MR-DC, the UE has a single RRC state, based on the MN RRC and a single C-plane connection towards the Core Network. Each radio node has its own RRC entity (E-UTRA version i.e. LTE RRC if the node is an LTE eNB or LTE ng-eNB or NR version i.e. NR RRC if the node is a NR gNB) which can generate RRC PDUs to be sent to the UE. RRC PDUs generated by the SN can be transported via the MN to the UE. The MN always sends the initial SN RRC configuration via MCG SRB, but subsequent reconfigurations may be transported via MN or SN. When transporting RRC PDU from the SN via SCG SRB, the MN does not modify the UE configuration provided by the SN.

In MR-DC, the radio protocol architecture that a particular radio bearer uses depends on how the radio bearer is setup. Four bearer types exist: MCG bearer, MCG split bearer, SCG bearer and SCG split bearer. These four bearer types are depicted inFIGS. 2A and 2Bassuming the NR user plane protocol stack. The MCG bearer is a MN terminated bearer having the associated PDCP entity anchored in the MN. The lower part of Layer 2 configuration associated with RLC entity and MAC entity for the MCG bearer can be configured either in the MN or SN. The SCG bearer is a SN terminated bearer having the associated PDCP entity anchored in the SN. The lower part of Layer 2 configuration associated with RLC entity and MAC entity for the SCG bearer can be configured either in the MN or SN. The MCG Split bearer is a MN terminated bearer having the associated PDCP entity anchored in the MN. The lower part of Layer 2 configuration associated with RLC entity and MAC entity for the MCG Split bearer can be configured in both the MN and SN. The SCG Split bearer is a SN terminated bearer having the associated PDCP entity anchored in the SN. The lower part of Layer 2 configuration associated with RLC entity and MAC entity for the SCG Split bearer can be configured in both the MN and SN. In theFIGS. 2A and 2Bwhen the LTE eNB is MN and connected EPC i.e. EN-DC (as depicted inFIG. 1C), the SDAP layer is not present in the user plane protocol stack. The MCG bearer or MN terminated bearer can be configured with either LTE PDCP or NR PDCP while the MCG Split bearer i.e. MN terminated Split bearer, the SCG Split bearer i.e. SN terminated Split bearer and SCG bearer i.e. SN terminated bearer is configured with NR PDCP. However when the eNB (i.e. LTE ng-eNB) is MN and connected to 5G-CN i.e. NGEN-DC (as depicted inFIG. 1D), then the SDAP layer protocol stack is presentFIGS. 2A and 2B. The MCG bearer i.e. MN terminated bearer can be configured with either LTE PDCP or NR PDCP while the MCG Split bearer, SCG Split bearer and SCG bearer is configured with NR PDCP in the EN-DC configuration (as depicted inFIG. 1C). The MCG bearer i.e. MN terminated bearer, the MCG Split bearer, SCG Split bearer and SCG bearer is configured with NR PDCP in NGEN-DC configuration (as depicted inFIG. 1D).

In LTE-DC bearer type change occurs either through HO or SN change as a result L2 entities are re-establish and reset. This is introduced to simplify the bearer type change procedure. This procedure impacts the data on other bearers also. This causes interruption in user services. Therefore, in the MR-DC configurations there is need to realize bearer type change without the handover procedure in addition to realizing the bearer type change with HO procedure or SN change procedure.

The above information is presented as background information only to help the reader to understand the present invention. Applicants have made no determination and make no assertion as to whether any of the above might be applicable as Prior Art with regard to the present application.

DISCLOSURE OF INVENTION

Solution to Problem

The principal object of the embodiments herein is to provide a method and system for performing a bearer type change of a plurality of bearers configured for a User Equipment (UE) in a wireless communication system.

Another object of the embodiments herein is to decide by a network to change a bearer type of one or more configured radio bearers.

Another object of the embodiments herein is to determine whether a termination point of an entity corresponding to an upper part of the Layer 2 configuration associated with a configured bearer is relocated from a first network node to a second network node.

Another object of the embodiments herein is to determine whether there is modification of the entity corresponding to a lower part of the Layer 2 configuration associated with the configured bearer.

Another object of the embodiments herein is to indicate to a User Equipment (UE) to perform one or more operations for changing the bearer type.

Another object of the embodiments herein is to perform a change in the security key associated with the configured bearer if it is determined that the termination point of the PDCP entity corresponding to the configured bearer has relocated.

Another object of the embodiments herein is not to change associated with the configured bearer upon determining the termination point corresponding to the PDCP entity has not relocated.

Another object of the embodiments herein is to perform the bearer type change through a handover procedure or a Secondary Node (SN) change procedure in response to performing change in the security key associated with the configured bearer.

Another object of the embodiments herein is to perform the bearer type change through a RRC reconfiguration procedure when there is no change in the security key associated with the configured bearer.

Another object of the embodiments herein is to perform a bearer type change from a MN terminated bearer to a MN terminated Split bearer.

Another object of the embodiments herein is to perform a bearer type change from a MN terminated Split bearer to a MN terminated bearer.

Another object of the embodiments herein is to perform a bearer type change from a SN terminated bearer to a SN terminated Split bearer.

Another object of the embodiments herein is to perform a bearer type change from a SN terminated Split bearer to a SN terminated bearer.

Another object of the embodiments herein is to perform a bearer type change from a MN terminated bearer to a SN terminated bearer.

Another object of the embodiments herein is to perform a bearer type change from a SN terminated bearer to a MN terminated bearer.

