TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communication, and, more particularly, to method of handling of PDU session procedure and mapped EPS bearer context in 5G system (5GS) and 4G LTE systems.

BACKGROUND

The wireless communications network has grown exponentially over the years. A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. LTE systems, also known as the 4G system, also provide seamless integration to older wireless network, such as GSM, CDMA and Universal Mobile Telecommunication System (UMTS). In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNodeBs or eNBs) communicating with a plurality of mobile stations, referred to as user equipments (UEs). The 3rdgeneration partner project (3GPP) network normally includes a hybrid of 2G/3G/4G systems. The Next Generation Mobile Network (NGMN) board, has decided to focus the future NGMN activities on defining the end-to-end requirements for 5G new radio (NR) systems.

In 5G, a Protocol Data Unit (PDU) session establishment is a parallel procedure of a Packet Data Network (PDN) connection procedure in 4G. A PDU session defines the association between the UE and the data network that provides a PDU connectivity service. Each PDU session is identified by a PDU session ID, and may include multiple QoS flows and QoS rules. In 5G network, QoS flow is the finest granularity for QoS management to enable more flexible QoS control. The concept of QoS flow in 5G is like EPS bearer in 4G. Each QoS flow is identified by a QoS flow ID (QFI) which is unique within a PDU session. Each QoS rule is identified by a QoS rule ID (QRI). There can be more than one QoS rule associated with the same QoS flow. A default QoS rule is required to be sent to the UE for every PDU session establishment and it is associated with a QoS flow. Each QoS flow may include multiple QoS rules consisting of QoS profile, packet filters, and precedence order.

When a QoS flow is added, the network can provide a QoS flow description IE to the UE, which comprises a list of QoS flow descriptions. Each QoS flow description comprises a QFI, a QoS flow operation code, a number of QoS flow parameters, and a QoS flow parameters list. Each parameter included in the parameters list consists of a parameter identifier that identifies the parameter. One of the parameter identifiers is the EPS bearer identity (EBI), which is used to identify the EPS bearer that is mapped to or associated with the QoS flow. When a QoS flow is deleted, all the associated EPS bearer context information that are mapped from the deleted QoS flow should be deleted from the UE and the network. This implies that the mapped/associated EPS bearer context should not exist if there is no corresponding QoS flow description. Otherwise, after inter-system change (e.g., from 5GS to EPS), if an EPS bearer is established based on the mapped EPS bearer context without QoS flow description, the associated QoS flow is undefined.

During a PDU session establishment or modification procedure, a UE may receive a mapped EPS bearer context IE of the PDU session for creating a new mapped EPS bearer having an EBI. However, if an existing mapped EPS bearer having the same EBI is associated with a PDU session, then a collision occurs on the EPS bearer. When inter-system changes from 5GS to EPS, UE behavior is undefined on how to handle such collision.

A solution is sought.

SUMMARY

A method of handling mapped EPS bearer context with duplicate EPS bearer ID (EBI) for 5GS to EPS inter-system change enhancement is proposed. UE is provided with a mapped EPS bearer context IE by the network to create a new mapped EPS bearer associated with a PDU session. UE detects collision of the new mapped EPS bearer—it has the same EBI as an existing EPS bearer. Upon successfully process the create request, UE either replaces the existing EPS bearer with the new mapped EPS bearer, or deletes the EPS bearer with duplicate EBI by explicit signaling to the network. As a result, when inter-system change from 5G to EPS happens, there is no EPS collision.

In one embodiment, a UE receives a Protocol data unit (PDU) session related message for a first PDU session in a mobile communication network. The PDU session related message carries a mapped evolved packet system (EPS) bearer context information element (IE) associated to the first PDU session. The UE determines that the mapped EPS bearer context IE comprises a new mapped EPS bearer to be created at the UE for the first PDU session. The new mapped EPS bearer has an EPS bearer identity (EBI). The UE detects that an existing mapped EPS bearer having the same EBI is associated with a second PDU session. The UE deletes the existing mapped EPS bearer associated with the second PDU session, or the UE deletes the new mapped EPS bearer associated with the first PDU session, upon successfully creating the new mapped EPS bearer for the first PDU session.

Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.

