HK1076971B

HK1076971B - Method and apparatus for handoff in a communication system supporting multiple-service instances

Info

Publication number: HK1076971B
Application number: HK05108899.0A
Authority: HK
Inventors: J.王; R．T．苏
Original assignee: 高通股份有限公司
Priority date: 2002-03-11
Filing date: 2003-03-11
Publication date: 2008-10-31

Description

Method and apparatus for handover in a communication system supporting multiple service instances

Background

FIELD

The present invention relates generally to wireless communication systems, and more particularly to a method and apparatus for packet data service handover.

Background

There is now an increasing demand for packetized data services over wireless communication systems. Since conventional wireless communication systems are designed for voice communications, extension to support data services introduces a number of challenges. In particular, there is a problem in handover of point-to-point protocol (PPP) communications involving data packets. As the system upgrades components, compatibility between the components may hinder the operation of the system. In addition, it is desirable to relieve the base station of handover responsibility and provide intelligent handover by infrastructure elements.

There is a need for fast and accurate handoff between Packet Data Serving Nodes (PDSNs) and other infrastructure elements in a wireless communication system.

Brief description of the drawings

Fig. 1 is a timing diagram illustrating call flow in a communication system in which a source PDSN (S-PDSN) and a target PDSN (T-PDSN) have similar capabilities.

Fig. 2 through 4 are timing diagrams illustrating call flow within a communication system in which a source PDSN (S-PDSN) and a target PDSN (T-PDSN) have similar capabilities but are unable to fully negotiate a handoff.

Fig. 5 is a timing diagram illustrating call flow in a communication system where the S-PDSN and the T-PDSN have similar capabilities, with one service instance dormant.

Fig. 6 is a timing diagram illustrating call flow within a communication system in which a source PDSN (S-PDSN) and a target PDSN (T-PDSN) have similar capabilities, wherein a Radio Network (RN) triggers various point-to-point (PPP) connections to effect handoff.

Fig. 7 is a timing diagram illustrating call flow within a communication system in which a target radio (T-RN) does not support multiple service instances.

Fig. 8 and 9 are timing diagrams illustrating call flow in a communication system in which a T-PDSN does not support multiple service instances.

Fig. 10 is a block diagram of a communication system supporting IP data transmission.

Fig. 11 illustrates the communication links involved in a handoff example of a system in which the S-PDSN and the T-PDSN have similar capabilities.

Fig. 12 illustrates the communication links involved in a handoff example of a system in which the S-PDSN and the T-PDSN have different capacities.

Fig. 13 illustrates the communication links involved in a handover example of a system in which the source radio network (S-RN) and the target radio network (T-RN) have different capacities.

Detailed Description

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated. While the various aspects of the embodiments are illustrated in the accompanying drawings, which are not necessarily drawn to scale unless specifically indicated.

The following discussion expands the exemplary embodiments to send data from or to a mobile node by first illustrating a network implementing mobile IP. The spread spectrum wireless communication system is then discussed. Next, a mobile IP network implemented within a wireless communication system is shown. Messages are illustrated that register a mobile node with a home agent to enable IP data to be sent to and from the mobile node. Finally, a method for reclaiming resources at a home agent is explained.

It is worthy to note that the example embodiments are provided as examples throughout the discussion; however, other embodiments may include various aspects without departing from the scope of the invention. In particular, the various embodiments may be applied to data processing systems, wireless communication systems, mobile IP networks, and any system in which efficient use and management of resources is desired.

The exemplary embodiment uses a spread spectrum wireless communication system. Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), or some other modulation technique. CDMA systems offer certain advantages over other types of systems, including increased system capacity.

The System may be designed to support one or more standards, such as "TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wireless spread Spectrum Cellular System" (IS-95 Standard), by "3^rdThe standards provided by the GenerationPartnership Project (3GPP) are embodied in a set of documents including Nos.3G TS25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214(W-CDMA standard), by "3G TS 25.214^rdThe TR-45.5 standard, provided by Generation Partnership Project 2 "(3 GPP2), was referred to as the cdma2000 standard and was previously referred to as IS-2000 MC. The standards are shown incorporated herein by reference.

Each standard specifically defines the processing of data transmitted from a base station to a mobile station and vice versa, and the following discussion considers, as an exemplary embodiment, a spread spectrum communication system that conforms to the CDMA2000 protocol standard. Other embodiments may include other criteria.

A communication system 100 according to an embodiment is shown in fig. 10. The communication system 100 includes a wireless portion and an Internet Protocol (IP) portion. The terminology used to describe the various elements of system 200 is for the understanding of the handover process described herein. A mobile station 120 operating within the communication system 100 first communicates with a source radio network (S-RN)108, where the term source refers to the RN as the original serving network. MS 120 establishes a Service Instance (SI) with the S-RN. A service instance refers to a link associated with a service part. For example, the service option may be packet data link, voice over IP link, etc. The S-RN establishes an A-10 connection with a source-PDSN (S-PDSN) through IP network 106. The A-10 connection is SI related. It is noted that various elements of the system, such as the S-PDSN 104, the S-RN 108, and the MS 120, may only support one SI or may support multiple SIs. Also, within a given system, such as system 100, individual elements may support only a single SI, while other elements support multiple SIs. The latter system configuration can lead to incompatibility of individual component capabilities and thus affect switching. S-PDSN 102 also communicates with IP network 130. The operation of system 100 may be specified within the cdma2000 wireless IP network standard.

MS 120 is mobile and may move into a region supported by target-RN (T-RN) 118. Since the MS 120 is able to communicate with the T-RN 118, a handoff may be made from the S-RN 108 to the T-RN 118. Once the handoff of the wireless portion of communication system 100 is complete, the packet data portion of system 100 must set up various PPP links, such as an a-10 connection from T-PDSN114 to the T-RN through IP network 116. As discussed above, there may be a variety of scenarios for the configuration and handoff process of a system, such as system 100.

In the first case, illustrated in FIG. 1 and referring to FIG. 11, S-PDSN 104 and T-PDSN114 have the same capacity with respect to handling Service Instances (SIs). As illustrated in fig. 11, multiple SI links may be established to S-PDSN 104 and T-PDSN 114. For multiple SI links, one link is designated as the primary link, or PPP link. The main link is used to set up the PPP link and also for signaling associated with multiple links. The primary link is a link that links the primary packet service instance. This is the service instance that is negotiated first when establishing a packet service. This means that the initial PPP negotiation takes place on this service instance. The primary packet service instance is directly associated with the packet data session. This means that whenever there is a packet data session, there is a primary packet service instance connected to it. The primary link is identified as the "master SI". The additional link is referred to as an auxiliary or second link, identified as "auxiliary si (aux si)". Each link is also defined by an a-10 connection to the PDSN.

In the call flow scenario of fig. 1, infrastructure elements S-PDSN 104 and T-PDSN114 successfully handoff communications with MS 120. The handover is performed without transferring responsibility to the MS 120. In other words, MS 120 does not need to initiate a new communication at the target network, such as may be required if the handover is unsuccessful and the target network may disrupt the primary SI and the secondary SI. As in fig. 1, S-PDSN 104 gives T-PDSN114 the necessary information to establish communication with MS 120. It is worth noting that even if the handover is done within the radio network or wireless part of the system, the packet data part or the IP part requires additional information to establish the various required connections. For example, the T-PDSN114 needs to know which SI is the primary SI because the T-PDSN114 needs to negotiate PPP established over the primary SI.

Fig. 1 illustrates call flow associated with a fast handoff of one embodiment. Fig. 1 illustrates the success of a handoff occurring between the same modifications of two PDSNs, e.g., the two PDSNs implementing IS-835-B procedures. In this case, there is a PDSN-to-PDSN (P-P) connection that is successfully established between the target-PDSN (T-PDSN) and the serving PDSN (S-PDSN). In case the P-P connection cannot be correctly established, a normal hard handover should occur without interrupting the traffic channel. However, if multiple service instances exist (e.g., voice over IP), the target PDSN is not aware of the PPP service instance (primary service instance), and therefore it cannot initiate PPP negotiation on the correct R-P connection. Each identified call flow step of fig. 1 is detailed as follows:

A. the mobile station has one or more sessions established through a source-radio network (S-RN) to a source-packet data serving node (S-PDSN). The mobile station may have multiple service instances allocated within the S-RN.

B. The mobile station detects the change in pilot signal strength and sends a pilot report to the S-RN. At this point, the mobile still has an air link traffic channel to the S-RN and an Internet Protocol (IP) session is established to the S-PDSN.

C.S-RN sends a handover request message to the target-radio network (T-RN) through a Mobile Switching Center (MSC) (not shown).

D.T-RN sends an A11 Registration Request (RRQ) to the target packet data serving node (T-PDSN), which includes setting the S bit to 1, and the serving P-P address attribute to the Pi IP address to the S-PDSN. P-P refers to the connection between the S-PDSN and the T-PDSN.

Pi refers to the PDSN to IP connection. The s bit indicates simultaneous bundling.

E.T-PDSN sends a P-P RRQ, which includes S bits set to 1 to the Pi IP address of the S-PDSN. The setting of the S bit indicates a request for simultaneous bundling at the S-PDSN.

F.S-the PDSN replies with a P-P Registration Reply (RRP) with the reply code set to 0. The reply code indicates whether the operation succeeded (failed). Reply code 0 corresponds to a successful operation, where reply codes other than 0 give different reasons for failure.

G.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

H. At this point, the forward bearer traffic to the S-PDSN is bi-casting to the S-RN and T-PDSN. The T-RN may buffer the last N packets, where N is implementation dependent. Reverse bearer traffic only goes through the S-RN and S-PDSN.

S-RN switches mobile service instances (Sis) to T-RN by sending a handoff direction instruction to the mobile station.

J. The mobile station hands over to the T-RN and sends a handoff completion indication to the T-RN.

K. After completing the Service Instance (SI) handoff, the T-RN sends the A11RRQ to the T-PDSN, which includes setting the s bit to 0 and including the active Start airlink record.

L.T-PDSN sends a P-P RRQ to the S-PDSN with S bit set to 0 and including an active start airlink record. The transmitted active start airlink record is the same as that received from the T-RN.

The M.S-PDSN replies with a P-P RRP, with the reply code set to 0.

N.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

At this point, the forward bearer traffic is piped from S-PDSN to T-PDSN over the P-P interface, then switched to the appropriate a10 session and passed to the T-RN. Reverse bearer traffic is sent from the mobile station to the T-RN and then to the T-PDSN over the appropriate a10 session. The T-PDSN tunnels the traffic to the S-PDSN over the P-P interface. Notably, the P-P session may be refreshed by the T-PDSN periodically sending P-P RRQs to the S-PDSN.

P.S-PDSN initiates Mobile A10/A11 session interruption by sending an A11RUP to the S-RN.

Q.S-RN responded with A11 RAK.

The r.s-RN indicates that the session will be interrupted by sending an a11RRQ to the S-PDSN while the lifetime is set to 0, including the active stop accounting record. Notably, an accounting record is sent from the serving PDSN to an Authentication Authorization and Accounting (AAA) unit. AAA is not shown.

The s.s-PDSN indicates that the session is released by sending an a11RRP to the S-RN, whose lifetime is set to 0. It is worth noting that the S-PDSN does not remove the associated PPP context because it is being used by mobile over the P-P interface.

In the second case, illustrated in fig. 2, again the S-PDSN and T-PDSN share the same capacity, however, they cannot negotiate handover of multiple SI links. The S-PDSN can send a message indicating which links are primary links. The T-PDSN then assumes the responsibility for the handoff and sets up the connection for the MS.

It is noted that the serving PDSN expects to send a PPP service instance indication within the P-P RRP during the signaling exchange period in which the P-P connection is set up. This information may be sent regardless of whether the P-P connection was successfully set up. The target PDSN uses this information to trigger negotiations on the correct R-P connection, either in the event of a P-P connection establishment failure or in the event of a detected connection disruption between the T-PDSN and the S-PDSN. Fig. 2 illustrates this type of call flow. Each identified step of the call flow of fig. 1 is described in detail below.

A. The mobile station has one or more sessions established through the S-RN to the S-PDSN. The mobile may have multiple service instances allocated within the S-RN.

B. The mobile station detects the change in pilot signal strength and sends a pilot report to the S-RN. Notably, the mobile still has an air link traffic channel to the S-RN and an IP session is established to the S-PDSN.

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

D.T-RN sends A11RRQ to T-PDSN, the request includes setting S bit to 1, setting the serving P-P address attribute to the Pi IP address of the S-PDSN.

E.T-PDSN sends a P-P RRQ to the Pi IP address of the S-PDSN, which includes setting the S bit to 1. The setting of the S bit indicates a request for simultaneous bundling at the S-PDSN.

F.S-PDSN replies with a P-P RRP that is set to a non-0 with a reply code that indicates that a P-P session cannot be established and that indicates a PPP service instance.

G.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

H.S-RN hands over the mobile service instance to the T-RN by sending a handoff direction instruction to the mobile station.

I. The mobile station hands over to the T-RN and sends a handoff completion indication to the T-RN.

J. After completing the service instance handoff, the T-RN sends the A11RRQ to the T-PDSN, which includes the s bit set to 0 and includes the active start airlink record.

K.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

L.T-PDSN initially negotiates with mobile PPP by sending a mobile station-LCP configuration request.

M.ppp negotiation is complete. For simple IP sessions, bearer traffic can now flow in both directions over the T-RN and T-PDSN. For a MIP session, the behavior is described as follows.

N.T-the PDSN sends Mobile IP (MIP) proxy advertisements to the mobile. Notably, the mobile can first send a MIP proxy request to the T-PDSN (not shown).

Mobile sending MIP RRQ to T-PDSN

P.T-PDSN processes the MIP RRQ and forwards it over the HA.

If the MIP RRQ is accepted, the HA responds with a MIP RRP with a reply code of 0.

R.T-the PDSN forwards the MIP RRP to the mobile. The mobile can now send and receive bearer data through its MIP session.

If the target PDSN fails to properly receive the P-P RRP after several retransmissions, the target PDSN should indicate an operational failure to the target RN in A11 RRP. In response, the T-RN releases the traffic channel. In this third case, the target PDSN cannot receive any message from the serving PDSN, and the MS releases the traffic channel. The responsibility for the handover falls on the MS because the MS initiates a communication, i.e., session, with the target network. Notably, for a given system, a radio network layer handoff must complete the handoff from S-PDSN to T-PDSN. The third case is illustrated in FIG. 3, where each identified step is described as follows:

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

F.T-the PDSN does not receive the P-P RRQ after the configured number of retransmissions of the P-P RRQ.

G.T-PDSN sends the A11RRP to the T-RN with the reply code set to non-0.

J. After completing the service instance handoff, the T-RN releases the traffic channel.

The ms re-initializes the SO33 to set up the traffic channel. SO33 refers to data service option 33 specified within IS 70.

L.T-RN sends A11RRQ to set up R-P connection.

M.T-PDSN replies with A11RRP setting the generation code to '0'.

Ms initiates PPP negotiation with T-PDSN by sending LCP-configure-request to T-PDSN.

The ppp negotiation is complete. For simple IP sessions, bearer traffic can now flow in both the T-RN and T-PDSN directions. For a MIP session, the behavior is described as follows.

P.T-the PDSN sends a mobile MIP proxy advertisement to the mobile. Notably, the mobile can first send a MIP proxy request to the T-PDSN (not shown).

Mobile sending MIP RRQ to T-PDSN

R.T-PDSN processes the MIP RRQ and forwards it over the HA.

S. if the MIP RRQ is accepted, the HA responds with a MIP RRP with a reply code of 0.

T.T-the PDSN forwards the MIP RRP to the mobile. The mobile can now send and receive bearer data through its MIP session.

In a fourth scenario, the target network, in particular the T-PDSN, cannot receive handover information from the source network, in particular the S-PDSN. The target network attempts to set up a PPP connection over all SI links. In other words, since the T-PDSN does not know which SI connection to use to set up the PPP connection, it sends the request information on all links. In this case, the T-PDSN sends a Link Control Protocol (LCP) registration message on all SI links. In this example, the MS expects two links, one for packet data, such as web access, and the other for voice over IP (VoIP). The target PDSN may still indicate within the a11RRP that the target RN operation was successful. The T-PDSN then sends an LCP configuration request over all R-P connections to trigger PPP negotiation. PPP negotiation occurs on the PPP service instance.

For the second packet service instance, the LCP configure request is treated as a packet data payload (e.g., for voice over IP it is treated as an RTP payload), so if the format is incorrect, or sent to the application as an error, it is discarded. After the PPP session is set up, MCFTP may be used to set up a second packet service instance. Each identified step within the call flow in fig. 4 is described as follows:

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

D.T-RN sends the A11RRQ to the T-PDSN, the request includes setting the s bit to 1,

the service P-P address attribute is set to the Pi IP address of the S-PDSN.

F.T-the PDSN does not receive the P-P RRQ after the P-P RRQ has retransmitted the configured number.

G.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

J. After completing the service instance handoff, the T-RN sends A11RRQ to the T-PDSN

K.T-PDSN replies with an A11 RRP.

L.T-PDSN sends LCP configuration requests on all service instances.

PPP negotiation only on PPP service instance

MCFTP sent over the PPP service instance is used to set up streaming and channel processing for the second service instance.

For a simple IP session, bearer traffic can now flow in both the T-RN and T-PDSN directions. For a MIP session, the behavior is described as follows.

Mobile sending MIP RRQ to T-PDSN

R.T-PDSN processes the MIP RRQ and forwards it over the HA.

In the fifth case, illustrated in fig. 5, the MS also expects multiple Si, especially two Si, however, the primary PPP Si is dormant. When the master SI is dormant, the MS is responsible for triggering dormant handoff after detecting a packet zone id (pzid) change after receiving an intra-traffic system parameter (ISPM) from the traffic channel. PZID identifies the packet data network supporting the MS. There are two problems in this case. First, if the MS is unable to receive ISPM, the call is dropped because there is no a10 and P-P connection for the PPP service instance. Second, dormant service instances must transition to an active state. Dormant service may not be required and it is a waste of resources to make it active to complete the handover. Each identified step is illustrated in FIG. 5, described as follows:

A. the mobile station has one or more sessions established through the S-RN to the S-PDSN. The mobile station has multiple dormant service instances, such as PPP service instances, and multiple active service instances allocated within the S-RN.

B. The mobile station detects the change in pilot signal strength and sends a pilot report to the S-RN. At this point, the mobile still has an air link traffic channel to the S-RN and an IP session is established to the S-PDSN.

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

F.S-PDSN replies with a P-P RRP with the reply code set to 0.

G.T-PDSN sends the A11RRP with the reply code set to 0 to the T-RN.

H. At this point, forward bearer traffic arriving at the S-PDSN is bi-cast to the S-RN and T-PDSN for the active service instance. The T-RN may buffer the last N packets, where N is implementation dependent. Reverse bearer traffic only traverses the S-RN and S-PDSN.

The I.S-RN hands over the mobile service instance (Sis) to the T-RN by sending a handoff direction instruction to the mobile station.

K. After completing the Service Instance (SI) handoff, the T-RN sends the A11RRQ to the T-PDSN, which includes the s bit set to 0 and includes the active Start airlink record.

L.T-PDSN sends a P-P RRQ to the S-PDSN with S bit set to 0 and including an activity start airlink record. The transmitted active start airlink record is the same as that received from the T-RN.

The M.S-PDSN replies with a P-P RRP, with the reply code set to 0.

N.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

O.T-the RN transmits the system information via an intra-traffic System parameter message (ISPM) that includes a new Packet Zone ID (PZID).

MS detects that PZID is unchanged, MS sends Enhanced Origination Message (EOM) to set up SO33, SO33 is the primary service instance as an example.

Q.T-RN sends A11RRQ to set up an A10 connection.

R.T-PDSN sends P-P RRQ to set up P-P connections.

S.S-PDSN replies with a P-P RRP.

T.T-PDSN replies with an A11 RRP.

U.T-RN sends the service connection to the MS to connect to the PPP service instance.

The ms completes the response with the service connection.

W. after connecting the PPP service instance, the T-RN sends a11RRQ to start accounting records.

X.T-PDSN sends a P-PRRQ to the S-PDSN.

Y.S-PDSN replies with a P-P RRP.

Z.T-PDSN replies with an A11 RRP.

At this point, the forward bearer traffic for the PPP service instance and the second service instance is tunneled from the S-PDSN to the T-PDSN over the P-P interface, and then handed off to the appropriate a10 session and sent to the T-RN. Reverse bearer traffic is sent from the mobile to the T-RN and then connected to the mobile to the T-PDSN at the appropriate a 10. The T-PDSN tunnels the traffic to the S-PDSN over the P-P interface. It is noted that the P-P session may be periodically refreshed by the T-PDSN sending P-P RRQs to the S-PDSN periodically.

The BB.S-PDSN initiates an A10/A11 session interruption of the mobile station to the S-RN by sending an A11RUP to the S-RN.

s-RN responds with a11 RAK.

The dd.s-RN indicates that the session will be interrupted by sending an a11RRQ to the S-PDSN while the lifetime is set to 0, including the active stop accounting record.

S-PDSN indicates that the session is released by sending a11RRP to S-RN, whose lifetime is set to 0. It is worth noting that the S-PDSN does not delete the associated PPP context because it is being used by the mobile station over the P-P interface.

In a sixth scenario, illustrated in FIG. 6, when the P-P connection is successfully established for the second service instance with the S-PDSN, the S-PDSN is responsible for triggering the P-P connection for the dormant PPP service instance or other dormant service instance, since the S-PDSN knows which service is in dormant mode. The T-PDSN may begin to trigger the setup of an a10 connection for the dormant service instance. The steps by which the call flow of fig. 6 is identified are described as follows:

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

D.T-RN sends A11RRQ to T-PDSN, the request includes S bit set to 1, setting the serving P-P address attribute to the Pi IP address of S-PDSN.

F.S-PDSN replies with a P-P RRP with the reply code set to 0.

G.T-PDSN sends an A11RRP with the reply code set to 0 to the T-RN.

H. Since the S-PDSN knows that the PPP service instance is in dormant mode, the S-PDSN sends a P-P RRQ to the T-PDSN to set up the P-P connection.

I.T-PDSN replies with a P-P RRP with the result code set to '0'.

There are two options:

option 1:

the T-PDSN sends an A11RUP to the T-RN to request the R-P connection to be established for the PPP service instance.

K.T-RN reverted to A11 RAK.

L. then T-RN sends a11RRQ to set up a10 connection.

Tpdsn replies with a11RRP, with the reply code set to 0.

Option 2:

N.T-PDSN sends A11RRQ for the PPP service instance to establish the R-P connection.

O.T-RN reverts to A11RRP, whose code is set to '0'.

At this point, forward bearer traffic arriving at the S-PDSN is bi-cast to the S-RN and T-PDSN. The T-RN may buffer the last N packets, where N is implementation dependent. Reverse bearer traffic only traverses the S-RN and S-PDSN.

Q.S-RN hands over a mobile service instance (Sis) to the T-RN by sending a handoff direction instruction to the mobile station.

R. the mobile station switches to the T-RN and sends a switch completion indication to the T-RN.

After completing the service instance handoff, the T-RN sends an a11RRQ to the T-PDSN, which includes setting the s bit to 0 and including the active start airlink record.

T.T-PDSN sends a P-P RRQ to the S-PDSN with S bit set to 0 and including an active start airlink record. The transmitted active start airlink record is the same as that received from the T-RN.

The U.S-PDSN replies with a P-P RRP, with the reply code set to 0.

V.T-PDSN sends the A11RRP to the T-RN with the reply code set to 0.

At this point, forward bearer traffic is tunneled from the S-PDSN to the T-PDSN over the P-P interface, then switched to the appropriate a10 session and sent to the T-RN, and then sent to the T-PDSN over the appropriate a10 session. The T-PDSN tunnels the traffic to the S-PDSN over the P-P interface. Notably, the P-P session may be refreshed by the T-PDSN periodically sending P-P RRQs to the S-PDSN.

X.S-PDSN initiates an A10/A11 session interruption to the S-RN by sending an A11RUP to the S-RN.

Y.S-RN responds with A11 RAK.

Z.S-RN indicates that the session will be interrupted by sending the A11RRQ to the S-PDSN while the lifetime is set to 0, including the active stop accounting record.

The aa.s-PDSN indicates that the session is released by sending a11RRP to the S-RN with its lifetime set to 0. It is noted that the S-PDSN does not remove the associated PPP context because it is being used by the mobile station over the P-P interface.

The cases and examples discussed herein assume the same version of protocol for the serving network and the target network. In other words, these examples and scenarios assume that the S-PDSN and the T-PDSN have similar capabilities. For example, each can support multiple service instances. Consider a situation where the packet data network and/or the radio network do not have similar capacity, but one can handle multiple SIs and the other cannot.

When the serving network can support multiple SIs, but the target network cannot, the system must determine which abort, how to implement such an abort. For example, there IS no problem when handing off from a low version PDSN (IS-835 version A or lower) to a high version PDSN (IS-835 version B or higher) because an IS-835-A PDSN can only support one packet data service instance. In this case, the second service instance may be set up after the handoff to the target PDSN. When the serving network has the capability of only a single SI, as specified in IS-95. And cdma2000 release 0 specifies support for a single SI. Starting with cdma2000 release a, specifying that multiple SIs are supported, and that the target can support multiple SIs, is the responsibility of the MS to initiate additional SIs with the target network after the handover.

A seventh scenario is illustrated in fig. 7 and related to fig. 13, where the target radio network T-RN cannot support multiple SIs. It is worth noting that the serving radio network S-RN is aware that the target network cannot support the session that was active within the serving network prior to the handover. For example, when a handoff occurs from a high version PDSN (IS-835 version B or higher) to a low version PDSN (IS-835 version a or lower), if a second service instance IS established, how to handle these multiple service instances can be a problem. In this case, the serving RN only effects a handoff (PPP service instance) to the primary service instance of the T-RN, since the serving RN knows that the target RN cannot support the concurrent service (multiple R-P connections). The MS may also indicate to the user to drop the second service instance because it roamed to a lower version area. Each of the identified steps of the call flow in fig. 7 is described as follows:

B. The mobile station detects the change in pilot signal strength and sends a pilot report to the S-RN. Notably, the mobile station still has an air link traffic channel to the S-RN and an IP session is established to the S-PDSN.

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

D. Since the S-RN knows that the T-RN cannot support the concurrent service, the S-RN hands over the PPP service instance of the mobile station to the T-RN by sending a handoff direction instruction to the mobile station.

E. The mobile station hands over to the T-RN and sends a handoff completion indication to the T-RN.

F. After completing the service instance handoff, the T-RN sends an A11RRQ to the T-PDSN, which includes setting the s bit to 0 and including the active start airlink record.

G.T-PDSN sends A11RRP to the T-RN with the reply code set to 0.

H.T-the PDSN initially negotiates PPP with the mobile station by sending an LCP configure-request to the mobile.

Ppp negotiation is complete. For simple IP sessions, bearer traffic can now flow in both directions over the T-RN and T-PDSN. For a MIP session, the behavior is described as follows.

The j.t-PDSN sends a mobile ip (mip) agent advertisement to the mobile station. Notably, the mobile station can first send a MIP proxy request to the T-PDSN (not shown).

K. Mobile station sends MIP RRQ to T-PDSN

L.T-PDSN processes the MIP RRQ and forwards it over the HA.

M. if the MIP RRQ is accepted, the HA responds with a MIP RRP with a reply code of 0.

N.T-the PDSN forwards the MIP RRP to the mobile station. The mobile station can now send and receive bearer data over its MIP session.

Fig. 13 illustrates a system 100 including a T-PDSN 144 that is capable of multiple SIs, but only one SI allowed by the T-RN 148 is supported in the illustration. After successful handoff to the target network, a master SI is established with the T-RN 148 and an associated A10 connection is established between the T-RN 148 and the T-PDSN 144.

In the eighth case, illustrated in fig. 8 and with respect to fig. 12, the target RN may support concurrent service, i.e., multiple service instances, but the corresponding T-PDSN cannot support multiple service instances. As illustrated in the call flow of fig. 8, the T-RN sends a11RRQ to request bi-casting after the S-RN requests a handoff. Since older versions of the T-PDSN do not support the establishment of P-P connections and bi-casting, the T-PDSN may send an A11RRP to indicate a failure. In this case, the T-RN does not know which is the PPP service instance and must release the traffic channel. The MS should indicate that the user call is dropped due to roaming to a lower release area. The MS sets up SO33 from scratch if needed. The steps of each reference number of FIG. 8 are described as follows:

A. the mobile station has one or more sessions established through the S-RN to the S-PDSN. The mobile station may have multiple service instances allocated within the S-RN.

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown).

D.T-RN sends A11RRQ to T-PDSN, the request includes S bit set to 1, setting the serving P-P address attribute to Pi IP of S-PDSN.

E. Since the T-PDSN does not support fast P-P interface handoff, the T-PDSN sends an A11RRP to the T-RN, with its reply code set to non-0.

F.S-RN hands over the mobile service instance to the T-RN by sending a handoff direction instruction to the mobile station.

G. The mobile station hands over to the T-RN and sends a handoff completion indication to the T-RN.

H. After the service instance handoff is completed, the T-RN releases the traffic channel because it does not know which service instance is the PPP service instance.

The ms re-initializes the SO33 to set up the traffic channel.

The J.T-RN sends A11RRQ to set up the R-P connection.

K.T-PDSN sends A11RRP to the T-RN with the reply code set to 0.

MS initiates PPP negotiation with T-PDSN by sending a mobile LCP configuration request

N.T-the PDSN sends the MIP proxy advertisement to the mobile station. Notably, the mobile station can first send a MIP proxy request to the T-PDSN (not shown).

Mobile station sends MIP RRQ to T-PDSN

P.T-PDSN processes the MIP RRQ and forwards it over the HA.

R.T-the PDSN forwards the MIP RRP to the mobile station. The mobile station can now send and receive bearer data over its MIP session.

Fig. 12 illustrates a system 100 including a T-PDSN 134 that is incapable of supporting multiple sessions. Thus, even though the T-RN 118 may support multiple SIs, only the primary SI has a corresponding A10 connection established with the T-PDSN 134.

In the ninth case, PPP service instance information is also exchanged in the handover of T-RN and S-RN. Thus, when the T-RN receives a failure indication from the T-PDSN, the T-RN releases only the second service instance and maintains the PPP service instance connection. Each of the labeled steps of the call flow of fig. 9 is described as follows:

C.S-RN sends a handoff request message to the T-RN through the MSC (not shown). And the S-RN indicates the PPP service instance to the T-RN.

E. Since the T-PDSN does not support fast P-P interface switching, the T-PDSN sends the A11RRP to the T-RN, with its reply code set to non-0.

F.S-RN sends the instance of the mobile service to the handoff T-RN by sending a handoff direction instruction to the mobile station.

H. Since the T-RN knows which service instance is a PPP service instance, the T-RN sends an A11RRQ to set up an R-P connection for the PPP service instance.

I.T-PDSN replies with an A11RRP, the result code is set to '0'.

The j.tt-RN also sends a service connection to the MS to release the second service instance and maintain the PPP service instance.

K.T-PDSN triggers PPP negotiation by sending an LCP configuration request

The ppp negotiation is complete. For simple IP sessions, bearer traffic can now flow in both directions over the T-RN and T-PDSN. For a MIP session, the behavior is described as follows.

M.T-the PDSN sends the MIP proxy advertisement to the mobile. Notably, the mobile can first send a MIP proxy request to the T-PDSN (not shown).

Mobile sending MIP RRQ to T-PDSN

O.T-PDSN processes the MIP RRQ and then forwards it to the HA.

P. if the MIP RRQ is accepted, the HA responds with a MIP RRP with a reply code of 0.

Q.T-the PDSN forwards the MIP RRP to the mobile station. The mobile station can now send and receive bearer data over its MIP session.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, circuits, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with: a general purpose processor, a Digital Signal Processor (DSP) or other processor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, to implement the functions described herein. A general purpose processor is preferably a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary processor is preferably coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an application specific integrated circuit, ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for handoff in a communication system, comprising:

establishing, prior to initiating a handover, a main link and a second link between a mobile unit and a serving packet data serving node through a serving radio network, the main link and the second link corresponding to separate connections between the serving packet data serving node and the serving radio network, and the main link being used to set up a point-to-point protocol, PPP, link;

initiating a handover from the serving radio network to a target radio network; and

a message identifying the primary link is sent to the target packet data serving node.

2. The method of claim 1, further comprising:

a primary link and a secondary link between the mobile unit and the target packet data serving node are established.

3. The method of claim 2, further comprising:

a point-to-point protocol (PPP) configuration request is sent from the target packet data serving node to the mobile unit.

4. The method of claim 1, wherein the primary link is associated with a first service instance and the second link is associated with a second service instance.

5. The method of claim 4, wherein the second service instance is a voice over internet protocol service.

6. The method of claim 1, wherein the serving packet data serving node and the target packet data serving node comprise compatible protocols.

7. The method of claim 6, wherein the compatible protocols are the same protocol.

8. The method of claim 1, wherein said initiating further comprises:

a pilot report is sent from the mobile unit to the serving radio network.

9. The method of claim 8, further comprising:

a handover message is sent from the serving radio network to the target radio network.

10. The method of claim 9, wherein the pilot report identifies a pilot signal strength.

11. The method of claim 1, wherein the message is a reply to a registration request.

12. A method of handover in a communication system, comprising:

initiating a handover from a serving radio network to a target radio network, wherein prior to initiating the handover, a first link and a second link between a mobile unit and a serving packet data serving node are established through the serving radio network, the first link and the second link corresponding to separate connections between the serving packet data serving node and the serving radio network;

receiving a registration request from the target radio network;

sending a link initiation message to the mobile unit over the target radio network on the first link, the first link associated with a first service instance; and

sending the link initiation message to the mobile unit over the target radio network on the second link, the second link associated with a second service instance.

13. The method of claim 12, wherein the first link is a point-to-point protocol (PPP) connection.

14. The method of claim 13, wherein the second link is a voice over internet protocol auxiliary link.

15. The method of claim 12, further comprising:

registration is requested from a serving packet data serving node.

16. A method of handoff in a communication system, comprising:

initiating a handover from the serving radio network to a target radio network, the serving radio network being adapted to support a plurality of service instances, the target radio network being adapted to support one service instance;

suspending the second link to the serving radio network;

sending primary link information of the serving radio network to the target radio network; and

effecting handover to the target radio network.

17. A method of handoff in a communication system, comprising:

initiating a handover from a serving radio network to a target radio network, the serving radio network coupled to a serving packet data serving node, the serving packet data serving node adapted to support a plurality of service instances, the target radio network coupled to a target packet data serving node, the target packet data serving node adapted to support one service instance;

effecting handover to the target radio network.

18. An apparatus in a communication system, comprising:

means for establishing a primary link and a secondary link between a mobile unit and a serving packet data serving node through a serving radio network prior to initiating a handover, the primary link and the secondary link corresponding to separate connections between the serving packet data serving node and the serving radio network, and the primary link being used to set up a point-to-point protocol, PPP, link;

means for initiating a handover from the serving radio network to a target radio network; and

means for sending a message identifying the primary link to a target packet data serving node.

19. An apparatus in a communication system, comprising:

means for initiating a handover from a serving radio network to a target radio network, wherein prior to initiating the handover, a first link and a second link between a mobile unit and a serving packet data serving node are established through the serving radio network, the first link and the second link corresponding to separate connections between the serving packet data serving node and the serving radio network;

means for receiving a registration request from the target radio network;

means for sending a link initiation message to the mobile unit over the first link through the target radio network, the first link associated with a first service instance; and

means for sending the link initiation message to the mobile unit over the target radio network on the second link, the second link associated with a second service instance.

20. In a communication system, an apparatus comprising:

means for initiating a handover from the serving radio network to a target radio network, the serving radio network being adapted to support a plurality of service instances, the target radio network being adapted to support one service instance;

means for suspending the second link to the serving radio network;

means for sending primary link information of the serving radio network to the target radio network; and

means for enabling handover to the target radio network.