Patent Application
20060120171
1. Field of the Invention
The invention relates to performing a handoff of a mobile terminal between different technologies, in particular between WLAN and a 3rd Generation (3G) mobile telecommunications network.
2. Description of the Related Art
Third Generation (3G) Networks such as CDMA 2000 and UMTS (Universal Telecommunication Network) provide high-speed wireless Internet access to mobile users over a wide coverage area. At the same time, Wireless Local-Area Networks (WLAN) based on technologies such as IEEE 802.11 or European HiperLAN provide low-cost, high-speed wireless Internet access solution within small areas.
In the following simplified network architectures of CDMA2000 and WLAN in respect to
A WLAN, 101, comprises, at least logically, an Access Point, AP 17, and a local area network gateway like for example a Wireless Service Node, WSN 18. According to
A CDMA2000 packet switched network, 100 comprises, at least logically, a Home Agent HA 15, a Foreign Agent FA 16, a Packet Data Serving Node PDSN 13. A Packet Core Function (PCF) usually co-located with a Base Station Controller (BSC) builds in CDMA2000 a radio network node RN 12. Further there is an Authentication, Authorization and Accounting Server AAA 14 and in this particular case a user with a Mobile Station MS 11 being attached to the network. The Mobile Station MS 11 might be a laptop, a palmtop or a phone that can access both technologies, namely the WLAN and the 3G technologies. The BSC, among other things, establishes the traffic channel for the MS, coordinates the access for multiple users. The PCF is responsible, among other things, for deciding which PDSN to send the traffic through. The PDSN aggregates data traffic from multiple BS/PCFs. Further it terminates a Point-to-Point (PPP) connection and maintains session state for each MS in its serving area.
It is well known, that there are two modes of data provision by means of IP connectivity, namely Simple IP and Mobile-IP. In case of Simple-IP if a MS moves from one PDSN to another, a new IP address is acquired and the PPP connection between the MS and the PDSN is to be re-established, which consequently means a re-establishment of all running data sessions. The Mobile IP has been developed to seamless mobility solutions among the diversity of accesses by keeping the same IP address for a session whilst a user moves between PDSNs or even different systems. The Mobile IP defines a Home Agent HA as the anchor point with which the mobile user always has a relationship, wherein the Foreign Agent FA acts as the local tunnel-endpoint at the access network which the mobile user is visiting. Expressed somewhat differently, the HA provides mobile IP services and keeps track of the MSs association with a visited network and with an IP address of an ongoing session. Again, in other words, the HA assigns an IP-address to a MS for a particular data session, if a MS roams in another network or to another PDSN, then it establishes a new PPP connection to the new FA using however the old IP address, which is provided by the HA. Subsequently the HA performs a reallocation of the old IP address to the new FA in an internal entries so that if receiving packets intended for the MS a tunneling of said data packets is performed via the new FA in the network where the MS is located using the relation of the new FA and the IP-address.
Returning to
In case of interoperation with CDMA2000 the WSN located in WLAN and supporting Mobile IP functionality implements an AAA service to interwork with the home AAA server in a 3G network. This enables to authenticate a user being in a WLAN for accessing a service and to collect accounting records generated in the WLAN.
Thus, the current development of the futures network goes into combining of both types of networks to provide ubiquitous high-speed wireless Internet connectivity to mobile users. In particular in such environment a need arises to provide a seamlessly switch between the complementary WLAN and 3G network, even during an ongoing Internet session. Mobile terminals that combine different radio interfaces in one device are already available. Further, there are solutions for seamless handover using Mobile IP. However, Mobile IP suffers from the problems of complex network architecture. First of all the Home Agent and the Foreign Agent are to be implemented in the network. This leads to a complex routing, since the packets are to be routed to a Home Agent and further to a Foreign Agent in a PDSN, which also has the task to route the data packets towards the users. Moreover the utilization of the Mobile IP leads to high handover latency, which even might end up in the range of 10 sec. Further, the implementation of the Mobile IP leads to large overhead of tunnelling IP packets, since the data packets are to be encapsulated for every link on the way from Service provider via the Home Agent, the Foreign Agent to the Mobile Station.
On the other hand the Simple IP as described above does not require the implementation of HA and FA. However, it has the disadvantage of assigning a new IP addresses and consequently of termination of an ongoing data session, which in case of file downloading means the necessity of re-loading the entire data file.
Even though in the above description, an interoperation between CDMA2000 and WLAN is described, it is to be pointed out that the same problems also occur in other 3G networks like in UMTS. Although, in UMTS different nodes are implemented, there is a relation in the provided functionality. Thus, for example the functionality implemented in a Serving GPRS Signalling Node (SGSN) and in a Gateway GPRS Signalling Node (GGSN) might be compared with the functionality of the PDSN node in CDMA2000 providing a serving of a user's session in a corresponding serving area. Further UMTS provides also an authentication unit, like the AAA server.
Further the same problems might also occur within one network, if there are different nodes serving a user in a way that the user has to establish a new connection if changing the serving nodes.
Therefore it is subject of the present invention to provide a solution for a seamless handover between a local area network and a wide area network while guaranteeing an optimized data provision in the networks.
It is therefore one broad object of this invention to provide for a user a seamless handover between a first serving node in a first radio area and a second serving node in a second radio area, wherein a user's data session is identified in the first radio area by means of a first address and wherein an authentication unit being accessible by the first serving node and by the second serving node is provided and wherein said method comprises the following steps being performed in the first serving node,
It is therefore another broad object of this invention to provide for a user a seamless handover between a first serving node in a first radio area and a second serving node in a second radio area, wherein a user's data session is identified in the first radio area by means of a first address and wherein an authentication unit being accessible by the first serving node and by the second serving node is provided and wherein said method comprises the following steps being performed in the second serving node,
It is therefore another broad object of this invention to provide a method for providing for a user a seamless handover between a first serving node in a first radio area and a second serving node in a second radio area, wherein a user's data session is identified in the first radio area by means of a first address and wherein an authentication unit being accessible by the first serving node and by the second serving node is provided and wherein said method comprises the following steps being performed in the authentication unit,
It is therefore another broad object of this invention to provide a first serving node for providing for a user a seamless handover between said first serving node in a first radio area and a second serving node in a second radio area, wherein a user's data session is identified in the first radio area by means of a first address and wherein an authentication unit being accessible by said first serving node and by the second serving node is provided and wherein said first serving node has,
It is therefore another broad object of this invention to provide a second serving node for providing for a user a seamless handover between a first serving node in a first radio area and said second serving node in a second radio area, wherein a user's data session is identified in the first radio area by means of a first address and wherein an authentication unit being accessible by the first serving node and by the second serving node is provided and wherein said second serving node comprises,
In the following preferred examples of the present invention shall be described in detail, in order to provide the skilled person with thorough and complete understanding of the invention, but these detailed embodiments only serve as examples of the invention and are not intended to be limiting. The following description shall make reference to the enclosed drawings, in which
It should be noted that the term “node”, “unit” in the context of the present invention refers to any suitable combination of hardware and software for providing a predetermined functionality in the communication network. In this way, said terms generally refers to a logical entity that can be spread out over several physical entities of the network, but can also refer to a physical entity located in one physical location.
It should be noted that the term “user” in the context of the present invention refers to a user equipment or a mobile station being a combination of hardware and software with the purpose to access a data session, to which an address is to be assigned in order to transmit data. Further no restriction should be made regarding whether it is one user or a multitude of users, which means that either one user might have one or a number of data sessions for which a seamless handover is to be performed, or the term might means a number of user's terminals with their sessions.
Further the first serving node and the second serving node refers to any combination of hardware and software for serving a user and his/hers data sessions. In CDMA2000, a PDCN node might perform the task of the first serving node. In case of UMTS, this task might be performed by a suitable combination of hardware and software being located in SGSN and GGSN.
Preferably the second serving node is located in a local area network, like for example the WLAN and the functionality might be implemented in any suitable gateway in said local network, like for example in the Wireless Service Node WSN in WLAN.
Preferably, the wide area communication network is a mobile communication network, e.g. is a mobile communication network operating according to CDMA2000 or UMTS (Universal Mobile Telephone System) or GPRS (General Packet Switched Radio) or any 3G system like for example EDGE, WCDMA. However, the present invention is also applicable in any communication network aiming to provide seamless handover without employing Mobile IP.
In the following an embodiment of the present invention in respect to
It is proposed that the first serving node participates in a data session by receiving a data session establishment message from the user for the sake of simplicity. However the first serving node might be also implemented as a node being separated from the transmission of data, since the task of the first serving node is to assign the first address. This might be performed for example during the establishment phase of a data session for a user.
Therefore, according to
Upon the first address, like the IP-address is assigned to the user's data session, according to the present invention it is proposed to send the assigned first address and the address of the first serving node to the authentication node, step 22 by sending the message 201. The sending of the addresses might be performed in any suitable way, for example it might be either sent in one or in separate message(s). In a subsequent step, step 23, the first serving node is preferably included in the transmission of the data, which should not be seen as a limitation. The first serving node is to be informed about a user leaving its serving area, step 24. This might preferably be performed by receiving a detach message, which might be sent by the user or any entity in the network notifying that the user has left. Such kind of a detach message is required to start a delay timer, step 25.
Currently when receiving a detach message the first address is discarded, since this means the user is not anymore in the serving area. According to the present invention it is proposed to delay the discarding of the first address, being assigned to user for the duration of the delay timer. Said timer might be implemented in any suitable way providing counting for a set time value. The duration of the timer might be either set statically to a particular value, or it might be variable value. Some experiments have shown that a handover between different networks might last up to 60 sec, so this measured value might be taken as an example in case the method is implemented for an inter-networks handover. However this should not be seen as any limitation to the present invention.
Thus, according to the implementation of the timer, said timer runs unless one of the events occurs, namely either the timer expires or a request from a second serving node, the message 302, for providing the first address is received. If the checking procedure results in an expired timer, step 27, then the first address is discarded, step 28. If the occurred event is the receipt of the request, step 29, then the first address is sent back, step 30 and message 203. Thus, the provision of the first address is only possible if the timer has not expired yet. Preferably if a request from the second serving nodes arrives after the expiration of the timer, then a non-availability of the first address message might be issued to the second serving node. Another option might be that in this case the first serving node does not send any message and it is the responsibility of the second serving node to act accordingly.
In the following an embodiment of the present invention in respect to
As already mentioned, preferably the second serving node is a node being located in a second network with a different technology, like for example a Wireless Service Node WSN located in a WLAN.
A user coming to the second network has to attach to the serving area in said second network to establish a connection for transmission of data. Preferably the second serving node is involved in the communication. Therefore according to
In case of having the first address, said address is assigned to the user's data session, step 37. Since the address has not changed while moving from a first radio network to a second radio network, the user might still access the same data session in a new network. Thus, the user experiences a seamless handover while changing networks. However, if the first address could not be provided, then a second address is assigned to the user, step 38, which means that in this case a session must be re-established. Preferably the second address is to be provided by the second serving node. There are different existing method for provision an address, like for example of IP-address a server might be contacted to assign a unique address or it might be taken form a local pool of addresses. Further it is to be noticed, that the provision of the second address might be performed at any time during the procedure according to
In the following an embodiment of the present invention in respect to
According to
In the following an embodiment of the present invention in respect to
Returning to
The first serving node, 510, comprises a sender, 56, a receiver, 57 and a timer, 55. The components might be realised in any suitable and preferably way. Thus, they might be realised as hardware or software or any combination thereof. Furthermore they might be implemented as separate units or as one unit. The sender 56 provides a first address and an address of said first serving node to the authentication unit, 500, over the connection 201. The task of the receiver 57 is to receive a detach message from the user for detaching from the first serving node, 510. Said message is transferred over the radio connection and the connection depicted as 501. Further there is the timer, 55, for delaying a discarding of the first address as aforementioned.
The authentication unit, 500, comprises a sender, 52, a receiver, 54 and storage, 53. The components might be realised in any suitable and preferably way. Thus, they might be realised as hardware or software or any combination thereof. Furthermore they might be implemented as separate units or as one unit. In particular the receiver is foreseen to receive messages from the first serving node, 510, message 201 carrying the first address plus an address of the first serving node, and from the second serving node, message 301 carrying a request for providing a second address for a user's data session. Preferably both functions are to be implemented in one unit. Further there is also a storage unit, 53 for saving the first address and the address of the first serving node. The sender, 52 sends the messages 401 and 402, which might be implemented as one message carrying the second address and the address of the first serving node to the second serving node.
The second serving node, 520 has a sender, 58 with a function for sending the message 301 carrying a request for providing permission to access a data service and with a function for sending the message 302 carrying a request for providing the first address. A receiver, 59, is foreseen to receive an attach message from the user, MS 11, attaching to the second serving node over the message 502 and for receiving an address of the second serving node from the authentication node, message 401.
According to the present invention the first serving node, 510 sends a first address being assigned to an ongoing user data session and an address of the first serving node, 201 to the authentication node, 502 for storing said addresses in storage 53. Both addresses are to be preferably, IP addresses. After a detach message, 501 from the user is received a timer, 55 for delaying a discarding of the first address is started.
In case a user, MS 11 moves to a second radio network, 111 with the second serving node, 520. At first the MS 11 attaches to the network by means of a attach message, 502, and then the second serving node, 520 sends a request to the authentication unit 500 for providing permission to access a service, which might be performed for example during an authentication procedure. Upon receipt of this message, the authentication unit 500 provides an address of the second serving node, message 401. In the next step, the second serving node, 520 sends a request for the first address to the first serving node 510 by the aid of the received address of the second serving node, message 302. The first serving node, 510 receives the request and at first it checks whether the first address being assigned to the user's data session while having the user in its coverage are is still available, in other words, whether the delay timer has not expired at this point. In this case the first address is provided to the second serving node, 520, message 203. In case the second serving node has received the first address a seamless handover might be guaranteed by assigning the first address to the user's data session, which is performed in the assignment unit, Assig. 51. In order to provide a full functionality of the system it is proposed to assign the second address to the user's data session, in case the first address is not available, as it is known.
In the following an embodiment of the present invention is presented in respect to
In
The Point-to-Point Protocol (PPP) provides a standard method of encapsulating network layer protocol information over point-to-point links. PPP also defines an extensible Link Control Protocol (LCP). The Link Control Protocol (LCP) is utilized for establishing, configuring, and testing a data-link connection. Thus, each end of the PPP link sends at first LCP packets to configure the data link during Link Establishment phase for an optional Authentication phase before proceeding to the Network-Layer Protocol phase, during which data session is transmitted. Currently two protocols are utilized for Authentication, namely the Password Authentication Protocol PAP and the Challenge-Handshake Authentication Protocol CHAP. The Password Authentication Protocol (PAP) provides a simple method for a node to establish its identity by sending repeatedly the assigned identity/password pair until the authentication of said node is acknowledged or the connection is terminated. The Challenge-Handshake Authentication Protocol (CHAP) is used to periodically verify the identity of a node. This is done upon initial link establishment, and may be repeated anytime after the link has been established. Thus, there are different methods, which might be chosen to perform authentification during establishing of a PPP connection. Wherein in order to perform the authentification successfully the communicating nodes are to be configured accordingly, dependent on the chosen method.
Returning to
In the subsequent message, step 607 the MS 11 sends a PAP authentification request carrying as parameter, as mentioned above a pair comprising the user name and the password. In this context it is to be mentioned, that the user name might be provided in any suitable and preferably way, depending on the implemented method in a network. Thus, it might be a NAI number, like for example the IMSI number. Further the authentification by means of PAP is to be seen as one possible embodiment without any limitation to the present invention. Thus, any other authentification method might be applied, or even since the authentification is not mandatory, the establishment phase might be performed without utilization of any authentification protocols. The user name is used for verification whether said user is permitted to access a service. Thus, in step 608 an Access Request, 608, message is sent to the AAA, 62, carrying the user name. In the server AAA a corresponding verification procedure is carried out, like for example the validation of the received password with the user as identified by the user name. In case of a successful verification, an Access Accept message is sent to the MS, 11, in step 609. The MS, 11, receives as an answer to the successful performed authentification, an acknowledgement message, PPP-Auth phase-PAP Auth Ack (610), sending of which means a termination of the authentification phase.
In the next phase, an establishment and a configuration of a IP connection for a data session is issued. Thus, in step 611 the MS, 11, sends a PPP-IPCP phase message to the PDSN, wherein IPCP is an abbreviation for PPP Internet Protocol Control Protocol and is used to establish and configure IP protocol over PPP. Upon receipt of this message, the PDSN, 61, allocates an IP address from the local pool, step 612, and assigns said IP address to the user name. In this context the IP address as just described is an embodiment of the first address as aforementioned. The user, MS, 11, receives a notification of a successful assignment of an IP address in form of an acknowledgment message, PPP-IPCP phase-ACK, 613 wherein said message carries the IP-address assigned to the user, MS 11. In the next step the PDSN 61 sends an accounting request, step 614, to the AAA, 62, for starting an accounting procedure for the following data session. Herein the present invention proposes to provide the AAA server, 62, with the first address, which is in this embodiment the assigned IP address and the IP address of the PDSN. Upon receiving the information the PDSN, 61 stores it in a suitable way, step 615. Preferably it is proposed to store this information in a user profile, which already exists on the AAA server. However it might be performed in any appropriate way, which ensures a reconstruction of the relation between the user name, the assigned IP address and the IP address of the PDSN node.
Subsequently the PDSN, 62 sends an accounting response to the MS 11, in step 616, whereupon the transmission of data session is started, step 617. In case the user moves to another network, or to another PDSN, which might be recognized by receiving a detach message from the user, MS 11, then an Accounting STOP message, 618, is sent from the old PDSN, 61, to the AAA, 62. According to the present invention it is proposed to start a delay timer, step 619 when the account STOP message is sent out. As already mentioned, this timer is used to delay the deleting of the IP-address assigned to a user's data session. Currently this message is being directly deleted after sending the Accounting stop message. According to the present invention, during the duration of the timer the PDSN waits for receiving any information on the location of the user, in other words it waits for receiving a message from the user who sent a detach message and who moved to another network. Thus, the deleting of the IP-address is delayed by the duration of the handover. In case no message from the new network serving the user is received in within the time interval, then upon expiration of the timer, the IP-address of the user's data session is discarded.
In the following an embodiment of the present invention is presented in respect to
For the sake of clarity and continuity, the last steps from
Returning to
A Dynamic Host Configuration Protocol (DHCP) as it is well-known provides a framework for passing configuration information to users on Internet. DHCP adds the capability to automatically allocate reusable network addresses and configuration options to Internet users. DHCP consists of two components: a protocol for delivering user-specific configuration parameters from a DHCP server to a user and a mechanism for allocating network addresses to the users. A DHCP client is an Internet user using DHCP to obtain configuration parameters such as an IP address. In the present embodiment, the user, MS 11 is a DHCP client and the WSN, 72 fulfils the task of a DHCP server. In order to obtain an IP address the user, MS 11, sends a DHCP DISCOVER broadcast message, 704 to locate a DHCP server. Said broadcast message is intercepted by a relay agent, SITE ROUTER, 71, which forwards the packets between the user MS, 11 (DHCP client) and the WSN, 72, (DHCP server), step 705. The WSN (DHCP server), 72 offers configuration parameters such as an IP address to the user in a DHCP OFFER unicast message. According to the present invention before responding with the DHCP OFFER message, the WSN queries the PDSN, step 706, using the received PDSN IP address to get the old user's IP address being an embodiment of the first address, which the user has had in the previous network. As a result of the query the WSN receives an answer, wherein either said answer includes the old user's IP address or it carries an indication, that the user's IP address is not more available, step 707. The content of the answer message depends on a time point of receiving the query message. In case the query message is received within the duration of the delay timer, then an old IP-address is given back. However, if the timer has already expired, than the user's IP has been deleted, and only an indication of non-availability of the IP address is given back.
According to
It is to be mentioned, that in case, the query message has been sent after expiry of the delay timer, then the WSN performs an assignment of a new IP address being an embodiment of the second address, as it is known according to the DHCP protocol. Thus, preferably if the answer message 707 is negative, then the WSP generates a new IP address, which is sent to the user by means of the DHCP OFFER message. Of course, this case does not provide a seamless handover.
Moreover, it is to be pointed out, that even though in the above description, an interoperation between CDMA2000 and WLA is described, this should not be seen as a restriction for the present invention, since the same problems also occur in other 3G networks like in UMTS. Although, in UMTS different nodes are implemented, there is a relation in the provided functionality. Thus, for example the functionality implemented in a Serving GPRS Signalling Node (SGSN) and in a Gateway GPRS Signalling Node (GGSN) might be compared with the functionality of the PDSN node in CDMA2000 providing a serving of a user's session in a corresponding serving area. Therefore the solution of the present invention is also applicable to other networks, like for example UMTS.
Thus, although several preferred embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 60626945 | Nov 2004 | US |
