WO2016037642A1

WO2016037642A1 - Handover from 3gpp to untrusted non-3gpp access based on measured communication path characteristics

Info

Publication number: WO2016037642A1
Application number: PCT/EP2014/069179
Authority: WO
Inventors: Daniel Nilsson; Anders LUNDSTRÖM
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2014-09-09
Filing date: 2014-09-09
Publication date: 2016-03-17
Anticipated expiration: 2017-03-09
Also published as: WO2016037670A1

Abstract

The invention relates to a mobile terminal (101,105) and a method of determining whether to perform handover of the mobile terminal in a wireless communications network from a radio access network (102), e.g. E-UTRAN, to an untrusted wireless local area network (103), e.g. WLAN. The method of determining whether to perform handover of a mobile terminal (101) in a wireless communications network from a radio access network (102) to a wireless local area network (103) comprises measuring (S101) a physical property of a communication path established between the mobile terminal (101) and a packet core network gateway node ePDG (105) via the wireless local area network (103), determining (S102) whether the measured physical property complies with at least one communication path quality criterion; and if so performing (S103) handover of the mobile terminal (101) from the radio access network (102) to the wireless local area network (103).

Description

HANDOVER FROM 3GPP TO UNTRUSTED NON-3GPP ACCESS BASED ON MEASURED COMMUNICATION

PATH CHARACTERISTICS

TECHNICAL FIELD

The invention relates to a network device and a method at the network device of determining whether to perform handover of the mobile terminal in a

5 wireless communications network from a radio access network to a wireless

local area network. The invention further relates to a computer program

performing the method according to the present invention, and a computer program product comprising computer readable medium having the

computer program embodied therein. io BACKGROUND

In the art, handover of a mobile terminal from one radio access network

(RAN) to another is commonly performed. The mobile terminal is typically a User Equipment (UE) such as a mobile phone, a personal digital assistant

(PDA), a smart phone, a tablet, a laptop, a media player, etc.

15 Figure 1 shows a schematic overview of an exemplifying wireless

communication network in the form of a Long Term Evolution (LTE) based network. The UE may at an instance be connected to a base station, such as an eNodeB, via a network referred to as Evolved Universal Terrestrial Radio Access Network (E-UTRAN) for LTE communication with the UE over an air

20 interface such as LTE-Uu. The core network in LTE is known as Evolved

Packet Core (EPC), and the EPC together with the E-UTRAN is referred to as Evolved Packet System (EPS). The LTE network will be described in more

detail subsequently in the detailed description.

Illustrated in Figure 1 are also RANs in the form of trusted/untrusted

25 Wireless Local Area Networks (WIANs) connecting to the EPC via a Trusted

Wireless Access Gateway (TWAG) /Access Controller (AC) and an Evolved

Packet Data Gateway (ePDG), respectively. The UE may connect to the ePDG via an SWu interface to establish a communication channel with the EPC

using Subscriber Identity Module (SIM) credentials and utilizing Internet Protocol Security (IPsec) and Internet Key Exchange (IKE) protocols for secure communication. IP mobility between various RANs is thus ensured.

Further, multiple UE Packet Data Network (PDN) connections are supported, where the UE simultaneously connects to the EPC via for instance both E- UTRAN and WLAN using Multi Access PDN Connectivity (MAPCON). Thus, the UE may have an ongoing call over the E-UTRAN and when the UE comes within reach of the WLAN, it connects to the EPC via the WLAN and is subsequently handed over from the E-UTRAN to the WLAN. The connection with the E-UTRAN is thus released, and the call will proceed over WLAN. This process should preferably be effected with minimal interruption (e.g. with a silent period of less than one second). A problem in the art is that the UE may be handed over to the WLAN even if the quality of the connection is not high enough for the call to continue. In such a case, it would have been better if the UE had remained with the E-UTRAN instead of being handed over.

A number of approaches have been proposed for solving this problem:

(a) handover of the UE to WLAN is based on the WLAN signal strength; if the signal strength of a WLAN access point (AP) as measured by the UE is above a handover threshold, then WLAN access is selected,

(b) handover of the UE to WLAN is based on WLAN load and backhaul capacity; a WLAN AP provides appropriate beacon information to the UE, from which the UE can determine whether to handover; and

(c) handover of the UE to WLAN is based on measurements towards

appropriate servers on the Internet; if the connectivity and quality are considered good enough, then the UE is handed over to WLAN.

However, with any one of these prior art approaches, there is still a risk that the UE is handed over to a WLAN having an inferior communication quality, while the UE instead should have remained in the E-UTRAN. SUMMARY

An object of the present invention is to solve, or at least mitigate, this problem in the art and thus to provide an improved method and device for handing over a mobile terminal from one radio access network to another. This object is attained in a first aspect of the present invention by a method of determining whether to perform handover of a mobile terminal in a wireless communications network from a radio access network to a wireless local area network. The method comprises measuring a physical property of a communication path established between the mobile terminal and a packet core network gateway node via the wireless local area network, determining whether the measured physical property complies with at least one

communication path quality criterion; and if so performing handover of the mobile terminal from the radio access network to the wireless local area network. This object is attained in a second aspect of the present invention by a network device configured to determine whether to perform handover of a mobile terminal in a wireless communications network from a radio access network to a wireless local area network. The network device comprises a processing unit and a memory, which memory contains instructions executable by the processing unit, whereby the network device is operative to measure a physical property of a communication path established between the mobile terminal and a packet core network gateway node via the wireless local area network, and to determine whether the measured physical property complies with at least one communication path quality criterion. If so, the mobile terminal is handed over from the radio access network to the wireless local area network.

It should be noted that the network device in one embodiment is

implemented by the mobile terminal, while the network device in a second embodiment is implemented by the packet core network gateway node. Further provided are a computer program performing the method according to the present invention, and a computer program product comprising computer readable medium having the computer programs embodied therein. Advantageously, by measuring a physical property of a communication path between a mobile terminal and a packet core network gateway node, such as an ePDG, via a WLAN, the property being one or more of e.g. bandwidth, latency, jitter, packet loss, etc., it can be determined whether the mobile terminal should be handed over from a RAN, such as for instance E-UTRAN, over which an ongoing communication session is undertaken by the mobile terminal, to the WLAN. Thus, before effecting the handover from for example E-UTRAN to WLAN, it is ensured by the measurement of the quality of the communication between the mobile terminal and the ePDG via the WLAN AP that the communication path is good enough to handle the ongoing communication session, in which case a handover of the mobile terminal is performed. If not, the mobile terminal remains in the E-UTRAN, and no handover is performed. For instance, the property measured could be packet loss of the communication path setup between the mobile terminal and the ePDG acting as a gateway between the WLAN and the EPC. If the criteria is that the packet loss cannot exceed 3%, and the measured packet loss rate is 2%, the mobile terminal is handed over to the ePDG (i.e. WLAN access is effected), since the criteria is complied with. To the contrary, should the measured packet loss amount to 4%, the mobile terminal remains in the E- UTRAN. The method can either be performed at the mobile terminal or the packet core network gateway node. It can even be envisaged that some steps of the method are performed at the mobile terminal while others are performed at the packet core network gateway node. For instance, the measuring of a physical property of a communication path established between the mobile terminal and a packet core network gateway node via the wireless local area network, and the determining whether the measured physical property complies with at least one communication path quality criterion are performed by the mobile terminal, wherein the packet core network gateway node is informed accordingly and performs the step of handing over the mobile terminal from the radio access network to the wireless local area network.

In a practical scenario, a mobile phone user enters her home while

conducting an ongoing Voice over LTE (VoLTE) call on her mobile phone over E-UTRAN. As soon as she enters her home, she comes within reach of her residential WLAN. The mobile phone will thus establish a

communication channel with the WLAN AP while maintaining the VoLTE call over E-UTRAN. However, in an embodiment of the present invention, a property of the communication path established between the mobile phone and the ePDG via the WLAN AP (i.e. the ePDG being located uplink from the AP, thereby acting as a gateway to the EPC), such as for instance packet loss, or latency, is measured, and if the quality of the communication path from the mobile phone to the ePDG is considered good enough, the mobile phone will be handed over to the WLAN where the phone call will continue, while the connection established over the E-UTRAN is released.

It should be noted that a plurality of communication path properties may be measured, for instance both packet loss and channel latency, in which case the criteria may be e.g. that the measured packet loss should be below 3% while maximum channel latency is not exceeded for the handover to be effected. In embodiments of the present invention, further physical properties of the communication path between the mobile terminal and the packet core network gateway to be measured and evaluated comprise one or more of (where uplink denotes direction on the communication path from the mobile terminal to the ePDG, while downlink denotes direction on the communication path from the ePDG to the mobile terminal):

• Uplink + downlink one-way latency. This requires synchronized clocks and could be achieved using Global Positioning System (GPS) in the mobile terminal. · Roundtrip time/latency. Uplink + downlink delay variation (either between two sequential data packets or a difference in variation between e.g. a respective packet and the packet with the lowest packet delay).

• Uplink + downlink Loss ratio · Uplink + downlink duplication ratio

• Uplink + downlink packet reorder ratio

Further embodiments of the present invention will be described in the detailed description of the present application.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic overview of an exemplifying wireless

communication system in which the present invention can be implemented;

Figure 2 illustrates a flowchart of an embodiment of the method according to the present invention;

Figure 3 illustrates a further embodiment of the present invention; and

Figure 4 shows a network device according to an embodiment of the present invention. DETAILED DESCRIPTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description. Figure l shows a schematic overview of an exemplifying wireless

communication system 100 in which the present invention can be

implemented. The wireless communication system 100 is an LTE based system. It should be pointed out that the terms "LTE" and "LTE based" system is here used to comprise both present and future LTE based systems, such as, for example, advanced LTE systems. It should be appreciated that although Figure 1 shows a wireless communication system 100 in the form of an LTE based system, the example embodiments herein may also be utilized in connection with other wireless communication systems, such as e.g. Global System for Mobile Communications (GSM) or Universal Mobile

Telecommunication System (UMTS), comprising nodes and functions that correspond to the nodes and functions of the system in Figure 1.

The wireless communication system 100 comprises one or more base stations in the form of eNodeBs, operatively connected to a Serving Gateway (SGW), in turn operatively connected to a Mobility Management Entity (MME) and a Packet Data Network Gateway (PGW), which in turn is operatively connected to a Policy and Charging Rules Function (PCRF). The eNodeB is a radio access node that interfaces with a mobile radio terminal 101, e.g. a UE or an Access Point. The eNodeB of the system forms the radio access network called Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 102 for LTE communicating with the UE 101 over an air interface such as LTE-

Uu. The core network in LTE is known as Evolved Packet Core (EPC), and the EPC together with the E-UTRAN is referred to as Evolved Packet System (EPS). The SGW routes and forwards user data packets over the Si-U interface, whilst also acting as the mobility anchor for the user plane during inter-eNodeB handovers and as the anchor for mobility between LTE and other 3rd Generation Partnership Project (3GPP) technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and PGW). For idle state UEs, the SGW terminates the downlink data path and triggers paging when downlink data arrives for the UE 101, and further manages and stores UE contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception. The SGW communicates with the MME via interface S11 and with the PGW via the S5 interface. Further, the SGW may communicate with the UMTS radio access network UTRAN and with the GSM EDGE ("Enhanced Data rates for GSM Evolution") Radio Access Network (GERAN) via the S12 interface.

The MME is responsible for idle mode UE tracking and paging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the SGW for a UE at the initial attach and at time of intra- LTE handover involving core network node relocation. It is responsible for authenticating the user by interacting with the Home Subscriber Server (HSS). The Non-Access Stratum (NAS) signaling terminates at the MME and it is also responsible for generation and allocation of temporary identities to UEs via the Si-MME interface. It checks the authorization of the UE 101 to camp on the service provider's Public Land Mobile Network (PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles the security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from the Serving General Packet Radio Service (GPRS) Support Node (SGSN). The MME also terminates the S6a interface towards the home HSS for roaming UEs. Further, there is an interface Sio configured for communication between MMEs for MME relocation and MME-to-MME information transfer.

The PGW provides connectivity to the UE 101 to external packet data networks (PDNs) by being the point of exit and entry of traffic for the UE 101. A UE may have simultaneous connectivity with more than one PGW for accessing multiple PDNs. The PGW performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening. Another key role of the PGW is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA lX and EvDO). The interface between the PGW and the packet data network, being for instance the Internet, is referred to as the SGi. The packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IP Multimedia Subsystem (IMS) services. The PCRF determines policy rules in real-time with respect to the radio terminals of the system. This may e.g. include aggregating information in real-time to and from the core network and operational support systems, etc. of the system so as to support the creation of rules and/or automatically making policy decisions for user radio terminals currently active in the system based on such rules or similar. The PCRF provides the PGW with such rules and/or policies or similar to be used by the acting PGW as a Policy and Charging Enforcement Function (PCEF) via interface Gx. The PCRF further communicates with the packet data network via the Rx interface.

The system further comprises a 3GPP Authentication, Authorization and Accounting (AAA) server, which takes care of the authentication,

authorization and accounting of the UE 101 connecting to the EPC network via an untrusted WLAN 103 and the ePDG 105 across interface SWm. The ePDG 105 further connects to the PGW via interface S2B/GTP. The 3GPP AAA server also connects to the HSS via interface SWx, to the PGW via interface S6b, and to an AC/TWAG via interface STa. The AC/TWAG provides a gateway for the UE 101 between the EPC network and trusted WLAN and further connects to the PGW via interface S2a/GTP. The UE 101 connects to the WLAN 103 via an access point (AP).

With further reference to Figure 1, the method at the mobile terminal 101 (i.e. the UE) of determining whether to handover to the WLAN is performed by a processing unit 115 embodied in the form of one or more microprocessors arranged to execute a computer program 117 downloaded to a suitable storage medium 116 associated with the microprocessor, such as a Random Access Memory (RAM), a Flash memory or a hard disk drive. Thus, as is illustrated by means of dashed lines in Figure 1, the processing unit 115 and the storage medium are included in the UE 101. The processing unit 115 is arranged to carry out the method according to embodiments of the present invention when the appropriate computer program 117 comprising computer- executable instructions is downloaded to the storage medium 116 and executed by the processing unit 115. The storage medium 116 may also be a computer program product comprising the computer program 117.

Alternatively, the computer program 117 may be transferred to the storage medium 16 by means of a suitable computer program product, such as a Digital Versatile Disc (DVD) or a memory stick. As a further alternative, the computer program 117 may be downloaded to the storage medium 116 over a network. The processing unit 115 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), etc.

Figure 2 illustrates a flowchart of an embodiment of the method of the present invention of determining whether to perform handover of the UE 101 in the wireless communications network 100 of Figure 1 from a radio access network 102 such as E-UTRAN to the untrusted WLAN 103. In a first step S101, when the UE 101 comes into reach of the untrusted WLAN 103, it measures a physical property of a communication path 104 established between the UE 101 and the ePDG 105, for instance round-trip latency. Thus, not only radio parameters of the interface between the WLAN AP and the UE 101 are measured, but also packet data parameters of the path 104 uplink of the AP extending to the ePDG 105. In a second step S102, if the value of the round-trip latency is determined to comply with a predetermined quality criterion of the communication path 104, such as e.g. being below a

maximum allowed round-trip latency of 100ms, handover is effected of the ongoing communication session from the eNodeB of the E-UTRAN 102 to the AP of the untrusted WLAN 103 in step 103. If not, the mobile terminal 101 remains with the E-UTRAN 102 in step S104. As previously has been discussed, the method illustrated with reference to Figure 2 may alternatively be implemented at the ePDG 105. Figure 3 shows a detailed illustration of an embodiment of the present invention. Initially in step S201, the UE 101 is connected to LTE via the E- UTRAN 102 and is engaged in an ongoing communication session in the form of a VoLTE call. In step S202, the UE 101 enters a WLAN 103 and performs an authentication process with the AP of the WLAN 103 using the WLAN Service Set Identifier (SSID). The authentication could be undertaken using any known appropriate authentication mechanism, such as an Extensible Authentication Protocol (EAP) employing an Authentication and Key

Agreement (AKA) mechanism in case of managed WLAN, or Wireless

Protected Access 2 (WPA2) encryption in case of residential WLAN. Upon successful authentication with the WLAN 103, the UE 101 will be assigned an Internet connection. However, the UE 101 still uses the established E-UTRAN connection for the VoLTE call.

Thereafter, in optional step S203, using the WLAN internet connection, the UE 101 performs ePDG selection using Domain Name System (DNS) queries. However, the 101 may alternatively be preconfigured to select a certain ePDG.

In order to determine whether to handover the ongoing VoLTE call, the UE 101 measures a physical property of the communication path 104 setup between the UE 101 and the ePDG 105 (for instance latency) in step S204 using for instance a protocol known as Two-Way Active Measurement Protocol (TWAMP). If the measured latency is considered small enough, the UE 101 is handed over to the WLAN AP in step S205 and the call proceeds with the EPC via the ePDG 105, while allocated resources in the E-UTRAN 102 is released. If not, the call is maintained over the E-UTRAN 102, and no channel is setup via the WLAN 103.

The UE 101 may further, in case path quality is considered good enough, authenticate itself towards the ePDG 105 in step S205 using EAP-AKA or EAP-SIM utilizing Internet Key Exchange (IKE) over the SWu interface.

The measurement session should be setup such that conditions are comparable for the ongoing communication session via the E-UTRAN 102 and the communication path between the UE 101 and the ePDG 105, for instance sending the same amount of test packets per seconds as is used in the VoLTE flow. The packet size should preferably also be of the same order. The length of the measurement may depend on the quality of the 3GPP connection; if it is good enough, the measurement period can be relatively long (-10 seconds). If 3GPP coverage is not good, a shorter test period can be selected (-0.5 seconds).

With reference to Figures 2 and 3, steps S201, S205 and S205 of Figure 3 correspond to steps S101, S102 and S103, respectively, of Figure 2.

Figure 4 shows a network device 101 according to an embodiment of the present invention. The network device 101 comprises measuring means 401 adapted to measure a physical property of a communication path established between a mobile terminal and a packet core network gateway node via a WLAN, determining means 402 adapted to determine whether the measured physical property complies with at least one communication path quality criterion. Further, the network device 101 comprises performing means 403 adapted to performing a handover of the mobile terminal from the radio access network to the WLAN. The measuring means 401 and/or the performing means 403 may comprise a communications interface for receiving and providing information to other devices. The network device 101 may further comprise a local storage for storing obtained data. The measuring means 401, determining means 402 and performing means 403, may (in analogy with the description given in connection to Figure 1) be implemented by a processor embodied in the form of one or more

microprocessors arranged to execute a computer program downloaded to a suitable storage medium associated with the microprocessor, such as a RAM, a Flash memory or a hard disk drive. The measuring means 401 and performing means 403 may comprise one or more transmitters and/or receivers and/or transceivers, comprising analogue and digital components and a suitable number of antennae for radio communication.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. A method of determining whether to perform handover of a mobile terminal in a wireless communications network from a radio access network to a wireless local area network, WLAN, comprising:

measuring (S101) a physical property of a communication path established between the mobile terminal and a packet core network gateway node via the WLAN;

determining (S102) whether the measured physical property complies with at least one communication path quality criterion; and if so

performing (S103) a handover of the mobile terminal from the radio access network to the WLAN.

2. The method of claim 1, the physical property being any one or a combination of bandwidth, latency, jitter, data packet loss, one-way latency, two-way latency, delay variation, loss ratio, duplication ratio, and packet reorder ratio.

3. The method of claims 1 or 2, the radio access network being any one of Evolved Universal Terrestrial Radio Access Network, E-UTRAN, Universal Mobile Telecommunication System, UMTS, radio access network, UTRAN, Global System for Mobile Communications, GSM, Enhanced Data rates for GSM Evolution, EDGE, Radio Access Network, GERAN.

4. The method of any one of the preceding claims, wherein the measuring of the physical property is performed using a Two-Way Active Measurement Protocol, TWAMP.

5. The method of any one of the preceding claims, the packet core network gateway comprising an Evolved Packet Data Gateway, ePDG.

6. The method of any one of the preceding claims, further comprising: performing (S202) authentication with an access point, AP, of the

WLAN; and

performing (S203) packet core network gateway selection.

7. The method of any one of claims 1-6, the method being performed at the mobile terminal.

8. The method of any one of claims 1-5, the method being performed at the packet core network gateway node.

9. A network device (101) configured to determine whether to perform handover of a mobile terminal in a wireless communications network (100) from a radio access network (102) to a wireless local area network (103), WLAN, comprising a processing unit (115) and a memory (116), said memory containing instructions executable by said processing unit, whereby said network device is operative to:

measure a physical property of a communication path (104) established between the mobile terminal (101) and a packet core network gateway node (105) via the WLAN (103);

determine whether the measured physical property complies with at least one communication path quality criterion; and if so to

perform a handover of the mobile terminal (101) from the radio access network (102) to the WLAN (103).

10. The network device (101) of claim 9, the physical property being any one or a combination of bandwidth, latency, jitter, data packet loss, one-way latency, two-way latency, delay variation, loss ratio, duplication ratio, and packet reorder ratio.

11. The network device (101) of any one of claims 9 or 10, wherein the measuring of the physical property is performed using a Two-Way Active Measurement Protocol, TWAMP.

12. The network device of any one of claims 9-11, the network device being the mobile terminal (101).

13. The network device of any one of claims 9-11, the network device being the packet core network gateway node (105).

14. A computer program (117) comprising computer-executable instructions for causing a device (101) to perform steps recited in any one of claims 1-8 when the computer-executable instructions are executed on a processing unit (115) included in the device.

15. A computer program product comprising a computer readable medium (116), the computer readable medium having the computer program (117) according to claim 14 embodied therein.