WO2009106098A1

WO2009106098A1 - Method and system for supporting media independent handover (mih) services

Info

Publication number: WO2009106098A1
Application number: PCT/EP2008/001611
Authority: WO
Inventors: Saverio Niccolini; Telemaco Melia; Patrick Stupar
Original assignee: Nec Europe Ltd.
Priority date: 2008-02-29
Filing date: 2008-02-29
Publication date: 2009-09-03

Abstract

A method and a system for supporting media independent handover (MIH) services, preferably according to the IEEE 802.21 standard, wherein a communication node (1) is attached to an access network (3), said access network (3) having access to an information server (4) via appropriate entities, wherein the information server (4) operates a network database which includes information - basic information - regarding the availability of neighbouring networks together (5, 6, 7) with corresponding Layer 2 attachment characteristics of available networks (5, 6, 7), and wherein said basic information stored in the network database of the information server (4) is provided to the communication node (1), in particular upon respective request from the communication node (1), are characterized in that the network database of the information server (4) is configured in such a way as to include information - additional information - regarding the functionality of available networks (5, 6, 7) on application level.

Description

METHOD AND SYSTEM FOR SUPPORTING MEDIA INDEPENDENT HANDOVER (MIH) SERVICES

The present invention relates to a method for supporting media independent handover (MIH) services, preferably according to the IEEE 802.21 standard, wherein a communication node is attached to an access network, said access network having access to an information server via appropriate entities, wherein the information server operates a network database which includes information - basic information - regarding the availability of neighbouring networks together with corresponding Layer 2 attachment characteristics of available networks, and wherein said basic information stored in the network database of the information server is provided to the communication node, in particular upon respective request from the communication node.

Furthermore, the invention relates to a system for supporting media independent handover (MIH) services, preferably according to the IEEE 802.21 standard, the system comprising a multitude of access networks that allow for attachment of communication nodes, at least one information server to which the access networks of said multitude of access networks have access via appropriate entities, wherein the information server operates a network database which includes information - basic information - regarding the availability of neighbouring networks together with corresponding Layer 2 attachment characteristics of available networks, and wherein the communication node is configured in such a way as to retrieve said basic information stored in the network database of the information server.

In recent years several types of wireless communication systems have been developed. For example, wireless local area networks (WLAN) are widely spread nowadays, cellular networks, such as Universal Mobile Telecommunication Systems (UMTS), have gained paramount importance, and, most recently, WiMAX (defined as Worldwide Interoperability for Microwave Access) has been developed as a standard-based technology enabling the delivery of last mile wireless broadband access. Each of these systems provides different types of services and specific applications.

For seamless handover between different types of networks, the IEEE 802.21 MIH (Media Independent Handover) specification has been developed. The scope of the IEEE 802.21 standard is to develop a specification that provides link layer intelligence and other related network information to upper layers to help mobility decision functions (located both in the terminal and in the network) and to optimise handovers between heterogeneous media. In this context, "media" refers to the method or mode of accessing a telecommunication system (e.g. cable, radio, satellite, etc.), as opposed to sensory aspects of communication (e.g. audio, video, etc.).

The standard aims at providing means to improve handovers across heterogeneous networks, including 802.x family of networks, 3GPP and 3GPP2 networks, by sharing information, events and commands between MIH peers which, most generically, will be referred to in the following as communication nodes (mobile terminals, network entities, multimedia devices, etc.). The Information Service, for sharing information between communication nodes, is one of the key concepts of the MIH architecture. This service assumes a centralized network database which resides in the operator's core network and which, in the context of the 802.21 standard, is operated by an Information Server IS. The data stored in this database provide information about the neighbouring networks of a communication node. Consequently, a communication node may request information from the database such as Network Type, Operator Identifier, Service Provider Identifier, Access Network Identifier, Roaming Partners, Cost, Network Standards, Security in Network, QoS in the Network, etc. Every time a communication node needs an update of this kind of information it may send a respective query to the Information Server IS which then scans its network database and forwards the requested information to the communication node.

When a communication node running a specific application, for instance a SIP (Session Initiation Protocol) based application, has to perform handover and several networks are available, which the node is aware of due to deployment of MIH services, the problem of choosing the best network in order to optimize a specific metric related to the running application(s) raises. To identify the best network the communication node has to perform trial and error handover procedures to get attached to a network that provides satisfactory quality parameters with respect to the specific application. However, performing such multiple handovers is time and energy consuming. In particular, if the MIH service reveals the availability of a multitude of neighbouring access networks and the running application is time critical, like VoIP (Voice over IP) applications, a seamless handover will be difficult to accomplish or will be even unfeasible due to the extensiveness of test operations that have to be carried out by the communication node in order to make out the network best suited for its specific requirements.

It is therefore an object of the present invention to improve and further develop a method of the initially described type for supporting media independent handover services in such a way that by employing mechanisms that are readily to implement an improvement in terms of discovering a network that provides optimal performance with respect to a specific application is achieved.

In accordance with the invention, the aforementioned object is accomplished by a method comprising the features of claim 1. According to this claim such a method is characterized in that the network database of the information server is configured in such a way as to include information - additional information - regarding the functionality of available networks on application level.

Furthermore, the aforementioned object is accomplished by a system comprising the features of claim 15. According to this claim such a system is characterized in that the network database of the information server is configured in such a way as to include information - additional information - regarding the functionality of available networks on application level.

According to the invention it has first been recognised that in the context of performing handover decisions the discovery of the best network in order to optimize performance related to a specific running application is a rather complex and time and energy consuming task. Further, it has been recognized that handover optimizations can be achieved by providing a specific extension to the information server. More specifically, according to the invention the network database of the information server is extended in such a way that it includes information regarding the functionality of available networks on application level. By this extension it becomes possible for mobile nodes to perform application layer optimized handover decisions that would not be possible otherwise. Moreover, the invention reduces the risk of performing multiple handovers since trial and error handover procedures to get attached to a network that provides satisfactory quality parameters are avoided. In fact, the additional information regarding the functionality of available neighbouring networks can be employed by a communication node to check application layer performances of different networks prior to handing over its application to one specific access network.

In a specific embodiment, in which the communication node is running a SIP based application, it may be provided that the additional information included in the network database of the information server includes SIP specific information.

The SIP standard provides multiple application layer mechanisms for performing session handover of SIP applications when nodes move among different access networks. Such SIP mechanisms propose which signalling messages (containing which parameters) should be exchanged in order to achieve handovers and the operations that the SIP entities (user agents and proxies) should perform. Latest discussions in the scientific literature and standardization organizations (SDO) have focused on providing such handovers seamlessly by means of inserting an intermediate anchoring element in the signalling and media path (such elements are commonly referred to as Session Border Controllers (SBCs), Outbound Proxies, Multimedia Session Control Function, etc.).

For SIP-based handovers, it is very important to know in advance which entities will be serving the mobile terminal running SIP application in order to optimize performance. The problem is that performance could be tremendously different when anchoring the multimedia session to different intermediate anchoring elements. Currently there is no mean in the IEEE 802.21 standard for terminal nodes running SIP applications to know in advance which SIP entities will be handling the call in the target network (unless these parameters are known in advance by static provisioning) because the discovering methods for such entities are all bound to a successful registration in the target network (via DHCP or via IP- Can specific methods, e.g. successful PDP context activation). By including SIP specific information in the network database of the information server such information can be delivered to the communication node before the handover takes place in order to allow the optimisation of SIP application layer specific performance metrics steering the handover procedure towards one network instead of another.

Advantageously, the additional information regarding SIP specific information includes information regarding the availability of SIP specific devices. Such SIP specific devices include, for instance, Session Border Controllers (SBC), SIP Outbound Proxies, multimedia session control functions, etc., or to put it in IMS (IP Multimedia Subsystem) terminology P-CSCF (Proxy Call Session Control Function), S-CSCF (Server Call Session Control Function), I-CSCF (Interrogation Call Session Control Function), etc.

For SIP specific devices which are existent in available neighbouring access networks it may be provided that the identifiers and/or addresses are stored as additional information in the network database of the information server. In particular, the addresses may include the SIP elements' IP addresses, FQDN (Fully Qualified Domain Name) addresses (which can be resolved into IP addresses by way of DNS (Domain Name System)) and/or MAC addresses

According to a specific embodiment, the communication node may employ the addresses of available SIP specific devices to establish a connection with these devices. Specifically, the connection between the communication node and an available SIP specific device may be established on IP level. After being connected with an available SIP specific device the communication node may trigger a measurement to evaluate the performance parameters of that device. In other words, the communication node may proactively discover SIP devices/elements and may exploit them to obtain application-level-performance information. In this regard it proves to be advantageous that the additional information stored in the network database of the information server includes information regarding Quality of Service (QoS) provided by available SIP specific elements. By using such additional information, the communication node is enabled to perform a metric-optimized application level handover decision. This means that depending on the specific application different metrics may be chosen. For instance, if the communication node performs a data download, an excellent packet loss performance may be chosen. On the other hand, if the application is for instance a (time critical) VoIP application a high-quality performance in terms of minimal delay may be crucial.

According to another specific embodiment the communication node may employ the additional information to proactively compute an estimated Quality of Service for possible future SIP based calls. In particular, such computation may be performed towards callees who are placed on a buddy list of the user of the communication node.

As what concerns a seamless integration into a standard architecture with the requisite of as little change as possible, it may be provided that the complete communication between the communication node on the one hand and the access networks on the other hand is performed by way of 802.21 messages. Furthermore, the additional information stored in the network database of the information server may be configured in form of individual information elements. In this context it proves to be advantageous to use the same data structure for the additional information as the standard one used for the basic information.

Advantageously, the information elements are configured in the network database of the information server according to neighbouring graphs. By this means the identification of those access networks which are relevant from the viewpoint of a communication node due to their operation in the node's neighbourhood can be easily performed.

There are several ways how to design and further develop the teaching of the present invention in an advantageous way. To this end, it is to be referred to the patent claims subordinate to patent claims 1 and 15 and to the following explanation of a preferred example of an embodiment of the invention, illustrated by the figure. In connection with the explanation of the preferred example of an embodiment of the invention by the aid of the figure, generally preferred embodiments and further developments of the teaching will be explained.

In the drawings:

Fig. 1 shows an abstract view of information elements as they are typically stored in a network database of the MIH Information Services according to the IEEE 802.21 standard, and

Fig. 2 shows an illustrative handover procedure according to an embodiment of the present invention.

With reference to Fig. 1 , a typical data structure of information elements according to the 802.21 Information Services (IS) is illustrated. The upper part of Fig. 1 illustrates a list of networks of the MIH Information Services, wherein each sheet represents a single access network. For each access network, the first three Information Elements IE specify the network type (IEEE 802.11 , IEEE 802.16, UMTS, etc.), the operator identifier, and the service provider identifier, respectively. The following Information Elements IE refer to access network specific information. This access network specific information typically includes the access network identifier and the access network auxiliary identifier. Furthermore, network specific information regarding roaming partners, costs, network security, network Quality of Service (QoS), network data rate, network IP configuration methods, network capabilities, and list of supported LCPs (Link Control Protocol). Further information elements may be added. In this context it is to be noted, that IS services can either be extended by the standardisation organisation responsible for them (i.e. currently the IEEE 802.21 Working Group) or can be specifically extended in a vendor-specific way.

The network database of the Information Services IS further includes information regarding the corresponded Layer 2 Point of Attachment (PoAs) of the networks registered with the Information Services IS. This is illustrated in the lower part of Fig. 1. Point of attachments are network nodes to which the communication nodes may attach and which haves access to the Information Server, either directly or indirectly via appropriate network entities acting as an intermediary or as a proxy.

As can be obtained from the lower left hand part of Fig. 1 , the first network, i.e. the network represented by the overhead sheet, comprises a total of k Point of

Attachments labeled PoA₁, PoA₂ PoA_k. The associated PoA specific information includes the PoA's MAC address, its location, its data rate, its channel range, subnet information, IP configuration methods, its capabilities, its IP address and QoS. In the lower right hand side of Fig. 1 the PoA specific information is shown for the second network from the list of all available access networks, which disposes of a total number of n PoAs.

Fig. 2 illustrates the architecture and the operational setup of a system according to an embodiment of the present invention. The embodiment employs the MIH Information Services IS according to the IEEE 802.21 standard.

Fig. 2 illustrates a communication node 1 which is designed as a MIH enabled multimode device 2. The multimode device 2 is attached to its home network 3 via a Point of Attachment which is not shown. When the communication node 1 decides that a handover is imminent, it communicates with the IS 4 of its home network 3 it is attach with in order to retrieve information about the neighbouring access networks which are possible candidates for handover. In the illustrated embodiment, the communication between the multimode device 2 and its home network 3 is performed through 802.21 messages (dotted line arrow). By triggering the MIH layer to signal with the MIH IS 4, the Information Server 4 provides all the topology information of available neighboured access networks as defined by the IEEE 802.21 standard and as illustrated and described above in connection with Fig. 1.

Further to the information mentioned so far, the MIH IS 4 includes information regarding the functionality of available networks on application level. More specifically, in the case shown in Fig. 2, the MIH IS 4 of the home network 3 includes information regarding SIP devices existing in available neighbouring networks. In particular, the SIP specific information includes the IP address and identifiers (if any) of SIP elements existing in the available neighbouring networks. In the specific scenario of Fig. 2, the multimode device has discovered a total of three available neighbouring access networks which are labelled visited network 5, visited network 6 and visited network 7.

The communication node 1 uses the SIP specific information included in the Information Services 4 and establishes a connection with each of the discovered available networks 5, 6, and 7. These connections are based on IP level and are established via the home network 3 (dashed line arrows). They are directed to the SIP devices' IP addresses indicated by the Information Services 4. After having established such connections, the multimode device 2 triggers measurements to evaluate the application level performances achievable when such SIP devices would be used. For instance, such measurements could be retrieved using some specific on-demand architecture and mechanisms able to predict call quality performance. According to its specific optimised metric, the multimode device 2 proactively selects that network form the entirety of available neighbouring access networks 5, 6, and 7 that provides best application level performance. Finally, the multimode device 2 hands over its SIP session to the selected network, which in the specific case shown is visited network 7 (solid line arrow).

It is to be noted that putting application layer information in the Information Services could mean forcing IS to be application-protocol aware which might end up in scalability problems if multiple protocols needs to be supported. However, it may be provided that the extension of the Information Services is restricted to SIP based applications. Such restriction would be relatively safe as SIP will be the protocol for many multimedia applications in the near future.

Many modifications and other embodiments of the invention set forth herein will come to mind the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

C l a i m s

1. Method for supporting media independent handover (MIH) services, preferably according to the IEEE 802.21 standard, wherein a communication node (1 ) is attached to an access network (3), said access network (3) having access to an information server (4) via appropriate entities, wherein the information server (4) operates a network database which includes information - basic information - regarding the availability of neighbouring networks together (5, 6, 7) with corresponding Layer 2 attachment characteristics of available networks (5, 6, 7), and wherein said basic information stored in the network database of the information server (4) is provided to the communication node (1), in particular upon respective request from the communication node (1 ), c h a r a c t e r i z e d i n that the network database of the information server (4) is configured in such a way as to include information - additional information - regarding the functionality of available networks (5, 6, 7) on application level.

2. Method according to claim 1 , wherein said additional information includes SIP (Session Initiation Protocol) specific information.

3. Method according to claim 1 or 2, wherein said additional information includes information regarding the availability of SIP specific elements, in particular SBCs (Session Border Controllers) and/or Outbound Proxies.

4. Method according to claim 3, wherein said additional information includes information regarding the identifiers and/or addresses of available SIP specific elements.

5. Method according to claim 4, wherein the communication node (1 ) employs the addresses of available SIP specific elements to establish a connection with said elements.

6. Method according to claim 5, wherein said connection between the communication node (1 ) and an available SIP specific element is established on IP level.

7. Method according to claim 5 or 6, wherein the communication node (1 ), after being connected with an available SIP specific element, triggers a measurement to evaluate the performance parameters of said element.

8. Method according to any of claims 1 to 7, wherein said additional information includes information regarding Quality of Service (QoS) provided by available SIP specific elements.

9. Method according to any of claims 1 to 8, wherein the communication node (1 ) retrieves said additional information from the network database of the information server (4) to proactively discover SIP elements.

10. Method according to any of claims 1 to 9, wherein the communication node (1 ) employs said additional information to perform a metric-optimized application level handover decision.

11. Method according to any of claims 1 to 10, wherein the communication node (1 ) employs said additional information to proactively compute an estimated Quality of Service (QoS) for possible future SIP based calls, in particular towards callees which are placed on a buddy list of the user of said communication node.

12. Method according to any of claims 1 to 11 , wherein the communication between said communication node (1) and said access network (3) it is attached with is performed by way of 802.21 messages.

13. Method according to any of claims 1 to 12, wherein said basic information and said additional information is stored in the network database of the information server (4) in form of individual information elements.

14. Method according to any of claims 1 to 13, wherein said information elements are configured in the network database of the information server (4) according to neighbouring graphs.

15. System for supporting media independent handover (MIH) services, preferably according to the IEEE 802.21 standard, the system comprising a multitude of access networks that allow for attachment of communication nodes, at least one information server (IS) to which the access networks of said multitude of access networks have access via appropriate entities, wherein the information server (IS) operates a network database which includes information - basic information - regarding the availability of neighbouring networks together with corresponding Layer 2 attachment characteristics of available networks, and wherein the communication node is configured in such a way as to retrieve said basic information stored in the network database of the information server (IS), c h a r a c t e r i z e d i n that the network database of the information server (IS) is configured in such a way as to include information - additional information - regarding the functionality of available networks on application level.