US20090245200A1 - Method and apparatus for communication between wireless telecommunications networks of different technology types - Google Patents

Abstract

For handover between wireless telecommunications networks of different technology types, an air interface is set up between a first node4 included in a network of a first technology type and a second node10 included in a network of a second different technology type. Signaling messaging, in accordance with the second technology type, is related to handover of a mobile terminal from the network of the first technology type to the network of the second technology type. The signaling messaging is encapsulated in a container for transmission over the signaling interface. An identifier is associated with the container to indicate that it encapsulates the signaling messaging. When the identifier is detected at the first node, the container is sent over the interface to the second node. In one method in accordance with the invention, the first technology type is WiMAX and the identifier is a special service flow identifier. This may be detected at an Access Services Network Gateway (ASN GW), for example. A method in accordance with the invention thus permits the use of logical radio channels for encapsulating inter-technology signaling.

Description

FIELD OF THE INVENTION
• The present invention relates to a method and apparatus for communication between wireless telecommunications networks of different technology types, and more particularly, but not exclusively, where the different technology types are what is termed ‘fourth generation’, or ‘4G’, technologies.
BACKGROUND OF THE INVENTION
• Currently, efforts in mobile telecommunications developments are directed to providing broadband data communications, known as 3.5G and 4G, using various competing radio access technologies (RATs) aiming to achieve high bandwidth combined with low latency, high efficiencies and flexibility. High Rate Packet Data (HRPD), also referred to as 1xEV-DO or High Data Rate (HDR), is a high-speed CDMA-based wireless data technology. WiMAX is an IEEE standard 802.16e for mobile technology. Long Term Evolution (LTE) is a Third Generation Partnership Project (3GPP) for enhancing UMTS. Ultra Mobile Broadband (UMB) is a 3GPP2 project.
• A mobile terminal (MS) may have a capability for communicating with networks of different technology types. If conditions deteriorate, for example, when the mobile terminal is connected to a node in one network, it may be desirable to transfer it to a new connection, which may be another node of the same network or a node in a different network. Signaling messaging is required between the mobile terminal and elements of a potential new target network node so as to complete handover preparation, for example, by transferring information regarding the context of the mobile terminal, and to carry out handover from a source node to a target node once the necessary steps have been fulfilled. If handover involves transfer between networks of different technology types, some mechanism must be provided to permit signaling messaging for use in making a connection between the mobile terminal and the target node to be sent to the target network to establish communication between them.
• One problem during inter-technology handover (HO) is timing for real-time services. It is desirable that the traffic interruption during such HO is kept within 300 ms to make the HO seamless and reduce the likelihood of real-time service being.
• Each Radio Access Technology uses different protocols and architectures to establish an IP service for an MS. Many of them involve the setup of the Radio Access Network session for the MS and the setup of L3 connectivity. For example: WiMax requires WiMax RAN access and WiMax session and IP session setup. HRPD requires HRPD session, PPP session and MIP session setup. Each one of these setups may take anytime between 1-5 seconds. Therefore, the setup of these sessions and reservation of the resources must be done in a “make-before-break” fashion, that is, before the actual HO execution. This is achieved by “tunneling” of target technology messages over the current serving technology.
• One possible tunneling mechanism is to rely directly on the IP network of the serving technology, which may be termed IP encapsulation, and tunnel the “pre-registration” directly from serving technology, via the Home Agent (HA), to the target technology's Radio Access Network (RAN).
BRIEF SUMMARY OF THE INVENTION
• According to a first aspect of the invention, a method for communication between wireless telecommunications networks of different technology types includes setting up an air interface between a first node included in a network of a first technology type and a second node included in a network of a second different technology type. Signaling messaging, in accordance with the second technology type, is related to handover of a mobile terminal from the network of the first technology type to the network of the second technology type. The signaling messaging is encapsulated in a container for transmission over the interface. An identifier is associated with the container to indicate that it encapsulates the signaling messaging. When the identifier is detected at the first node, the container is sent over the interface to the second node. In one method in accordance with the invention, the first technology type is WiMAX and the identifier is a special service flow identifier. This may be detected at an Access Services Network Gateway (ASN GW), for example. A method in accordance with the invention thus permits the use of logical radio channels for encapsulating inter-technology signaling.
• By using a method in accordance with the invention, it is not necessary to rely on IP tunneling and thus security issues associated with IP communications, such as Denial of Service attacks, hijacking of sessions and exposure of RAN equipment to hackers, may be avoided during the handover process. Additionally, by using the invention, the source node may be made aware that the mobile terminal is signaling to the second technology in preparation for a handover, whereas this would not visible to a source node if IP encapsulation were to be used instead. Also, by employing a method in accordance with the invention, delays are reduced as there is no need to rely on existing L3 protocols, this being particular advantageous for real time applications such as speech.
• In one method in accordance with the invention, the first technology type is WiMAX and the second technology type may be HRPD, for example. The method may also be applied where the first technology type is HRPD and the second technology type is WiMAX.
• A method in accordance with the invention may use first and second technology types that are respective ones of the following technology types: High Rate Packet Data (HRPD); WiMAX; Long Term Evolution (LTE); and Ultra Mobile Broadband (UMB). Future evolutions of these or other types of technology may be used.
• In one method in accordance with the invention, the interface is an S101 interface, although another common interface standard may be adopted instead. The S101 interface has been proposed for use in inter-RAT communications for communication between LTE and HRPD networks. By adopting the S101 interface for other combinations of technology types, compatibly issues are reduced and there is no need to modify interfaces between different types for each specific combination, aiding backward compatibility and easing later system upgrades and providing a scalable solution.
• Where the first technology type is HRPD, the identifier may, in one method, be in the form of a signaling link protocol (SLP) identifier.
• In a method in accordance with the invention, the interface may be an S101 interface. This is an interface defined initially for use between an LTE network and an HRPD network. The present inventors have realized that such an interface may be more generally applied for use as an interface between networks with other combinations of technology types.
• According to a second aspect of the invention, a node for a wireless telecommunications network of a first technology type, the node comprises a detector for detecting an identifier associated with a message container, the identifier indicating that the container encapsulates handover signaling messaging in accordance with a second technology type different to the first technology type. It further comprises a transmitter for transmitting a container having the detected identifier over an air interface with another node included in a wireless telecommunications network of the second technology type. The first and second technology types may be respective ones of the following technology types: High Rate Packet Data (HRPD); WiMAX; Long Term Evolution (LTE); and Ultra Mobile Broadband (UMB). Other types of technology or evolutions of these may be used.
• According to a third aspect of the invention, a mobile terminal having the capability of communicating with networks of at least two respective different technology types is operative, during handover preparation for handover from a first network of a first technology type to a second network of a second technology type, to add an identifier to signaling messaging for use in the second network to indicate that the signaling messaging is to be tunneled from the first network to the second network over an interface. The first and second technology types may be respective ones of the following technology types: High Rate Packet Data (HRPD); WiMAX; Long Term Evolution (LTE); and Ultra Mobile Broadband (UMB). Other types of technology or evolutions of these may be used.
BRIEF DESCRIPTION OF THE DRAWING
• Some embodiments and methods in accordance with the present invention are now described by way of example only, and with reference to the accompanying drawings, in which:
• FIG. 1 schematically illustrates a wireless telecommunications system having two networks of respective different technology types.
DETAILED DESCRIPTION
• With reference toFIG. 1, an access terminal (or mobile terminal) (AT/MS)1 is in communication with aWiMAX network2, being connected to abase station3. Thebase station3 is connected via an ASN GW4 to common core network elements shown at5 and including AAA6, PCRF7, Home Agent/Location Manager (HA/LMA)8 andIMS9 entities.
• Another network of a second technology type, HRPD, includes an HRPD AN*/PCFsecond node10 which connects to aPDSN11 via the A10/A11 interface12. The PDSN11 connects to the common core network elements shown at5.
• In a Wimax network, all traffic received over the Wimax air interface from the MS1 is sent from the Foreign Agent (FA), which is part of the ASN-GW4, to the Home Agent (HA). The ASN GW4 is the network node that performs RAN control and routing. After transmission to the HA, the traffic is subsequently routed to its destination using standard IP routing.
• In Wimax air interface, a MS may have multiple service flows (SF) simultaneously, and each SF has a unique identifier (called SFID). The Wimax ASN-GW4 is the network element that performs IP classification and mapping of IP flow to Wimax SF and vice versa. To create the equivalent of S101 interface similar to that between LTE and HRPD, theASN GW4 is able to detect all tunneled signaling messages, intercepting them to perform special routing to HRPD RAN instead of going via the standard WiMax FA to HA tunneling mechanism.
• In a method in accordance with the invention, a special service flow is created. This is a flow of traffic that can be identified by its unique ID in the RAN, and not by its IP classifier such as source/destination address, source/destination port number, protocol ID, and so on.
• In a WiMax to HRPD handoff, the ASN-GW4 creates a secure tunnel between itself and the HRPD RAN (there could be more than one tunnel for load sharing purpose) to carry aS101 interface13 between ASN-GW4 andHRPD RAN10. The MS1 uses a special flow (from AT/MS1 to ASN-GW4) to send any HO trigger it may detect, for example, such as change in signal strength). The ASN-GW4 also uses a special flow (from ASN-GW4 to AT1) to convey any network information (such as neighbor list of co-located HPRD BSs and/or border cell notification to AT) to assist HO. For all AT/MS-originated messages (destined for HRPD RAN for HRPD session setup), the ASN-GW4 recognizes the special service flow ID (which is a unique globally known SF ID) and uses the secure tunnel established earlier as S101 to deliver messages, the signaling messaging being encapsulated in a container which also includes an identifier as to its contents.
• From the point of view of the ASN-GW4, all the tunneled signaling messages from HRPD RAN are received as if they come directly from a Wimax terminal via Wimax BS that carries the Wimax air interface over the Wimax R6 interface (such as SS association as if AT/MS has performed a successful ranging, authentication exchange, initial SF creation, IP connectivity setup, etc).
• Thus, the special service flow initiated by ASN-GW4 and/or AT/MS1 is used for intercepting and sending HRPD session set-up messages between AT and HRPD RAN (sent as a WiMAX payload). This avoids the need for a special tunneling capability on the WiMAX air interface.
• For handover from HRPD to one of LTE, Wimax or UMB networks, for example, the same mechanism may be applied. HRPD air interface has the concept of RLP flows and SLP flow. RLP flow corresponds to A10 connection (R-P) with PDSN. SLP flow is used for HRPD signaling messages and it terminates in HRPD RNC. Each MS may support multiple RLP flows, similar to service flows in WiMax. By applying the same technique of identify the HO tunneling message using the special SLP-like flow ID, the HRPD RNC can create the same S101 interface from HRPD to LTE, Wimax or UMB, as applicable.
• Thus, it is possible to minimize changes to deployed networks while providing Network Control of handover, to maintain security of HRPD RAN, and use single Interface from HRPD to a number of emerging technologies, such as WiMAX, LTE and UMB.
• A method and embodiment in accordance with the invention may be deployed without modifying either the HRPD or WiMAX radio interfaces, thus avoiding impact on existing radio interfaces. Changes may be isolated to specific equipment such as RNCs. This potentially leads to a large cost saving over both making radio interface changes and adding security mechanisms such as firewalls.
• Coordination of the radio handover with the bearer path switching is critical, and cannot be efficiently managed by the mobile alone. The network must be involved. This special flow-based tunneling provides operators with security and flexibility for optimization compared to regular IP connection.
• The re-use of certain approaches from LTE to HRPD handover allows an operator for flexibility in making business decisions regarding technologies.
• The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (15)

1. A method for communication between wireless telecommunications networks of different technology types, including the steps of:

setting up an air interface between a MS and a first node included in a network of a first technology type;

setting up a signaling interface between the first node included in a network of a first technology type and a second node included in a network of a second different technology type

providing signaling messaging over the above signaling interface in accordance with the second technology type, the signaling messaging being related to handover of a mobile terminal from the network of the first technology type to the network of the second technology type;

encapsulating the signaling messaging in a container for transmission over the signaling interface;

associating an identifier (from the over-the-air interface message) with the container to indicate that it encapsulates said signaling messaging;

and, when the identifier is detected at the first node, sending the container over the signaling interface to the second node.

2. The method as claimed inclaim 1 and wherein the first technology type is WiMAX and the identifier is a special service flow identifier.

3. The method as claimed inclaim 2 and wherein the second technology type is HRPD.

4. The method as claimed inclaim 3 and wherein the signaling interface is an S101 interface.

5. The method as claimed inclaim 2 and wherein the identifier is detected at the Access Services Network Gateway (ASN GW).

6. The method as claimed inclaim 1 and wherein the first technology type is HRPD.

7. The method as claimed inclaim 6 wherein the identifier is in the form of a signaling link protocol (SLP) identifier or a new identifier that is equivalent to SLP (the common characteristics of this new identifier with SLP is: they boith terminate at HRPD RNC and will not be forwarded to HRPD PDSN).

8. The method as claimed inclaim 1 and wherein the first and second technology types are respective ones of the following technology types: High Rate Packet Data (HRPD); WiMAX; Long Term Evolution (LTE); and Ultra Mobile Broadband (UMB).

9. The method as claimed inclaim 8 and wherein the interface is an S101 interface.

10. A node for a wireless telecommunications network of a first technology type, the node comprising: a detector for detecting an identifier associated with a message container, the identifier indicating that the container encapsulates handover signaling messaging in accordance with a second technology type different to the first technology type; and a transmitter for transmitting a container having the detected identifier over an air interface with another node included in a wireless telecommunications network of the second technology type.

11. The node as claimed inclaim 10 and wherein the first and second technology types are respective ones of the following technology types: High Rate Packet Data (HRPD); WiMAX; Long Term Evolution (LTE); and Ultra Mobile Broadband (UMB).

12. The node as claimed inclaim 10 and wherein the interface is an S101 interface.

13. A mobile terminal having the capability of communicating with networks of at least two respective different technology types and operative, during handover preparation for handover from a first network of a first technology type to a second network of a second technology type, to add an identifier to signaling messaging for use in the second network to indicate that the signaling messaging is to be tunneled from the first network to the second network over an interface.

14. The mobile terminal as claimed inclaim 13 and wherein the first and second technology types are respective ones of the following technology types: High Rate Packet Data (HRPD); WiMAX; Long Term Evolution (LTE); and Ultra Mobile Broadband (UMB).

15. The mobile terminal as claimed inclaim 13 and wherein the interface is an S101 interface.

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