US-12621732-B2 - User device, radio communication system, and radio communication method

Abstract

User equipment (UE) includes a mapping information holding unit that holds association information in which are associated with each other a type of an EPS bearer set in 4G and a type of a QoS flow set in 5G and that depends on a quality of service, a filter holding unit that holds a filter of a traffic flow associated with the EPS bearer set for the UE in the 4G, and a QoS rule generating unit that generates, based on EPS Bearer ID for recognizing the type of the EPS bearer and the filter held by the filter holding unit, 5G QoS Rule associated with the QoS flow.

Inventors

• Takashi Koshimizu
• Jari Mutikainen
• Riccardo Guerzoni
• Irfan Ali

Assignees

• NTT DOCOMO, INC.

Dates

Publication Date

20260505

Application Date

20180615

Priority Date

20170616

Claims (2)

1. 1 . A user device comprising: a memory that holds association information indicating an association between an Evolved Packet System (EPS) bearer that is set in a first radio communication system according to 4G and a Quality of Service (QoS) flow that is set in a second radio communication system according to 5G, the memory that holds a traffic flow template associated with the EPS bearer; and a processor that performs handover from the first radio communication system to the second radio communication system, wherein the processor derives, based on the association information and the traffic flow template, a quality-of-service rule of the QoS flow associated with the traffic flow template when performing the handover, wherein the traffic flow template comprises one or more filter identifiers, precedence, and filter content, and wherein, when a new QoS flow is mapped to an EPS bearer identifier already assigned to an existing QoS flow, the processor recognizes the bearer identifier contained in QoS flow ID description received during handover and links both QoS flows to that same bearer.
2. 2 . A radio communication method implemented in a user device comprising: holding association information indicating an association between an Evolved Packet System (EPS) bearer that is set in a first radio communication system according to 4G and a Quality of Service (QoS) flow that is set in a second radio communication system according to 5G; holding a traffic flow template associated with the EPS bearer; performing handover from the first radio communication system to the second radio communication system; and deriving, based on the association information and the traffic flow template, a quality-of-service rule of the QoS flow associated with the traffic flow template when performing the handover, wherein the traffic flow template comprises one or more filter identifiers, precedence, and filter content, and wherein, when a new QoS flow is mapped to an EPS bearer identifier already assigned to an existing QoS flow, the user device recognizes the bearer identifier contained in QoS flow ID description received during handover and links both QoS flows to that same bearer.

Description

TECHNICAL FIELD The present invention relates to a user device, a radio communication system, and a radio communication method capable of performing inter-system handover. BACKGROUND ART 3rd Generation Partnership Project (3GPP) specifies Long Term Evolution (LTE), and with an aim of further speeding, specifies LTE-Advanced (hereinafter, it is assumed that 4G includes the LTE-Advanced). Moreover, in the 3GPP, specifications of a successor system of the LTE (hereinafter, referred to as 5G) called 5G New Radio (NR) and the like are being studied. The specifications of such 5G also include inter-work between 4G and 5G, for example, handover of a user device (User Equipment, UE) between 4G and 5G. In the inter-system handover between 4G (specifically Evolved Packet Core (EPC)) and 5G (specifically 5G Core (5GC)), a mapping between PDN connection set in the EPC and PDU session set in the 5GC is necessary. Specifically, a mapping between an EPS bearer related to the PDN connection and a QoS flow related to the PDU session is necessary. Moreover, when the UE performs handover from 4G to 5G, it is necessary that the content of a traffic flow template (TFT), which is a list of filters of a traffic flow (IP flow) associated with the EPS bearer, is reflected in a QoS rule associated with the QoS flow of the handover destination. That is, it is necessary that the UE and EPC-5GC recognize filtering content of similar traffic flow before and after the handover. Therefore, when the UE performs handover from 4G to 5G, a method of associating, regardless of the content of the TFT associated with the EPS bearer, a default QoS rule with the QoS flow of the handover destination has been proposed (see Non-Patent Document 1). With this method, when executing the handover, it is not necessary to exchange information between the UE and the EPC-5GC. Therefore, the handover procedure from 4G to 5G can be simplified. Furthermore, because the handover processing load is reduced, this may lead to reduction in delay. PRIOR ART DOCUMENT Non-Patent Document Non-Patent Document 1: “Solution for mobility in the EPC=>5GC direction”, S2-173522, 3GPP TSG SA WG2 Meeting #121, 3GPP, May 2017 SUMMARY OF THE INVENTION The method described in Non-Patent Document 1 considers a case in which a particular TFT is not associated with the EPS bearer (that is, a case in which a so-called “match all” filter is associated). However, for example, there are situations, like in Voice over LTE (VoLTE), in which a particular TFT is associated with the EPS bearer. In such situations, if the method of associating the default QoS rule with the QoS flow of the handover destination described above is used, similar quality of service (QoS) cannot be provided to a traffic flow of the VoLTE after completion of the handover to 5G. The present invention has been made in view of the above discussion. One object of the present invention is to provide a user device, a radio communication system, and a radio communication method that can autonomously reflect the content of the TFT in the QoS rule associated with the QoS flow of the handover destination even when the particular traffic flow template (TFT) is associated with the EPS bearer. A user device according to one aspect of the present invention is a user device (UE 50) that performs handover between a first radio communication system (4G) and a second radio communication system (5G). The user device includes an association information holding unit (mapping information holding unit 56) that holds association information indicative of an association between a type of a bearer (EPS bearer) set in the first radio communication system and a type of a flow (QoS flow) that is set in the second radio communication system and that depends on a quality of service; a filter holding unit (filter holding unit 57) that holds a filter (TFT) of a traffic flow associated with the bearer set for the user device in the first radio communication system; and a rule generating unit (QoS rule generating unit 58) that generates, based on a bearer identifier (EPS Bearer ID) for recognizing the type of the bearer and the filter held by the filter holding unit, a quality-of-service rule (5G QoS Rule) associated with the flow. A radio communication system according to another aspect of the present invention is a radio communication system including a first radio communication system and a second radio communication system. The radio communication system includes an association information holding unit (mapping information holding unit 330) that holds association information indicative of association between a type of a bearer set in the first radio communication system and a type of a flow that is set in the second radio communication system and that depends on a quality of service; a filter acquiring unit (filter acquiring unit 350) that acquires a filter of a traffic flow associated with the bearer set for a user device in the first radio commun