Patent Abstract:
There is provided a method for performing an inter-packet data service node (PDSN) hard handoff. The method is implemented by setting up a channel link passing through a target base station controller (T-BSC), a source base station controller (S-BSC), a source packet control function (S-PCF) and a source-PDSN (S-PDSN) by establishing a channel link between the S-BSC and the T-BSC via a mobile station center (MSC) in an active packet session mode, performing the hard handoff between the S-BSC, the T-BSC and a mobile station (MS) and transmitting or receiving user packet data exchanged between the MS and the T-BSC through the established channel link to or from the S-PDSN in case the hard handoff is completed.

Full Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to synchronous IMT-2000 wireless packet communication networks; and, more particularly, to a method for performing a fast inter-packet data service node (PDSN) hard handoff without data loss via a mobile switching center (MSC) so as to provide high-speed/high-quality real-time data services without data loss in an active packet mode.  
         DESCRIPTION OF RELATED ART  
         [0002]    In conjunction with current integrated Internet protocol (IP) networks, an Internet protocol based wireless packet data network is standardized so as to provide Internet services and real-time VoIP services in a third generation synchronous IMT-2000 wireless access network.  
           [0003]    In particular, there exist technical problems of header compression and a handoff in implementing the current Internet protocol based wireless packet network and these problems should be solved to obtain satisfactory QoS.  
           [0004]    According to a standardization document IS-835 related to the third generation IMT-2000 synchronous wireless packet data network, as components constructing the wireless packet data network, there are a base station controller (BSC), a packet control function (PCF) unit, a packet data service node (PDSN), a mobile Internet protocol (IP) home agent (HA) and an authentication/authorization/accounting (AAA) unit.  
           [0005]    Referring to FIG. 1, there is illustrated a call-processing flow diagram showing an Inter-PDSN hard handoff procedure defined in the IS-835 and IOS V4.x.  
           [0006]    When a message showing that a signal strength of a mobile station (MS)  101  became over a given signal strength threshold defined in a network and the MS  101  will convert to another access network identifier (ANID) is transmitted from the MS  101  to a source-BSC (S-BSC)  103 , the S-BSC  103  sends a Handoff Required message including a cell list within a domain of a target-BSC (T-BSC)  107  to an MSC  111  in step S 101  and actuates a T7 timer. The Handoff Required message contains a previous ANID (PANID).  
           [0007]    The MSC  111  selects the T-BSC  107  having an available wireless channel from the cell list, adds the PANID and a hard handoff indicator to a Handoff Request message and transmits the Handoff Request message to the T-BSC  107  in step S 103 . Herein, the hard handoff indicator means a handoff type component representing a hard handoff. After receiving the Handoff Request message, the T-BSC  107  allocates appropriate idle wireless resources and transmits null traffic channel data on a forward traffic channel.  
           [0008]    To set up an A8-Connection, the T-BSC  107  provides an A9-Setup-A8 message to a target-PCF (T-PCF)  109  and actuates a TA8-Setup timer in step S 105 . Herein, the A8 is a user traffic path for BSC-PCF packet data services defined in the standardization document. The A9 represents a signal path for the BSC-PCF packet data services defined in the standardization document. In step S 105 , a hard handoff indicator field in the A9-Setup-A8 message is set to 1.  
           [0009]    After receiving the A9-Setup-A8 message, the T-PCF  109  sets up the A8-Connection, transmits an A9-Connect-A8 message to the T-BSC  107  and actuates a Twaitho9 timer in step S 107 . At this time, the T-BSC  107  and the T-PCF  109  do not receive packet data from a source-PDSN (S-PDSN)  121  and the PDSN  121  continuously sends forward packet data to the S-BSC  103  through an S-PCF  105 . Meanwhile, after receiving the A9-Connect-A8 message, the T-BSC  107  stops an operation of the TA8-Setup timer.  
           [0010]    Since the hard handoff indicator field in the A9-Setup-A8 message was set to 1, an A10/A11 Connection is not established yet. The A10 and A11 represent traffic and signal paths for PCF-PDSN packet data services defined in the standardization document, respectively.  
           [0011]    Then, in step S 109 , the T-BSC  107  allows the MS  101  to be tuned to a corresponding wireless channel by transmitting a Handoff Request Ack message including appropriate wireless channel information to the MSC  111  and actuates a T9 timer so as to wait for the signal receiving from the MS  101  through the corresponding wireless channel.  
           [0012]    The MSC  111  prepares a call switching from the S-BSC  103  to the T-BSC  107  and delivers a Handoff Command message including the wireless channel information provided from the T-BSC  107  to the S-BSC  103  in step S 111 . The S-BSC  103  terminates an operation of the T7 timer.  
           [0013]    The S-PCF  105  receives an A9-Air Link (AL) Disconnected message from the S-BSC  103  and, then, stops packet data transmission to the S-BSC  103  in step S 113 . After transmitting the A9-AL Disconnected message, the S-BSC  103  actuates a Tald9 timer.  
           [0014]    In step S 115 , the S-PCF  105  sends an A9-AL Disconnected Ack message to the S-BSC  103  and the S-BSC  103  terminates an operation of the Tald9 timer.  
           [0015]    In step S 117 , the S-BSC  103  transmits a general handoff direction message (GHDM) or a universal handoff direction message (UHDM) to the MS  101  and actuates a Twaitho timer so as to allow the MS  101  to return to the S-BSC  103 .  
           [0016]    The MS  101  provides the S-BSC  103  with an MS Ack Order message as a response to the GHDM or UHDM in step S 119 .  
           [0017]    In step S 121 , the S-BSC  103  transmits a Handoff Commenced message to the MSC  111  so as to notify that the MS  101  is instructed to move to a channel of the T-BSC  107  and actuates a T306 timer to wait for transmission of a Clear Command message from the MSC  111 . The Handoff Commenced message is transmitted after an operation of the Twaitho timer is terminated.  
           [0018]    If the MS  101  completes the hard handoff procedure by obtaining synchronization through the use of a backward communication channel frame or preamble data, the MS  101  transmits a Handoff Completion message to the T-BSC  107  in step S 123  and the T-BSC  107  which received the Handoff Completion message transmits a BSC Ack Order message to the MS  101  in step S 125 .  
           [0019]    Further, in step S 127 , the T-BSC  107 , which received the Handoff Completion message from the MS  101 , provides the T-PCF  109  with an A9-AL Connected message including the PANID. The T-BSC  107  terminates an operation of the Twaitho9 timer and the T-PCF  109  actuates a Talc9 timer.  
           [0020]    In step S 128 , the T-PCF  109  selects a target-PDSN (T-PDSN)  123  for a corresponding call and sends an All-Registration Request message with a mobility event indicator included in a vendor/organization specific extension to the T-PDSN  123 .  
           [0021]    If the All-Registration Request message is verified, the T-PDSN  123  accepts a connection by transmitting an All-Registration Reply message including an Accept indication to the T-PCF  109  in step S 129 . At this time, A10 Connection Binding information is updated to the T-PCF  109  in the T-PDSN  123 .  
           [0022]    Then, the T-PCF  109  transmits an A9-AL Connected Ack message to the T-BSC  107  as a response to the A9-AL Connected message and terminates an operation of the Talc9 timer in step S 131 .  
           [0023]    After the T-BSC  107  detects that the MS  101  is connected to the T-BSC  107 , the T-BSC  107  transmits a Handoff Complete message to the MSC  111  so as to notify that the hard handoff is successfully performed for the MS  101  and terminates an operation of the T9 timer in step S 133 .  
           [0024]    After then, in step S 134 , a point-to-point (PPP) link layer connection is established between the MS  101  and the T-PDSN  123  and there is performed a mobile Internet protocol (MIP) registration procedure between the wireless packet network and the MS  101 . If the registration is completed, user packet data are exchanged through the A10 Connection between the MS  101  and an opposite MS.  
           [0025]    Referring to FIG. 2, there will be explained the PPP establishment and MIP registration procedure.  
           [0026]    In step S 135 , the MSC  111 , which received the Handoff Complete message, transmits a Clear Command message to the S-BSC  105 . The S-BSC  105  terminates an operation of the T306 timer and the MSC  111  actuates a T315 timer.  
           [0027]    In step S 137 , the S-BSC  103  sends an A9-Release-A8 message to the S-PCF  105  so as to release the A8-Connection and actuates a Trel9 timer.  
           [0028]    The S-PCF  105  releases the A8/A10/A11-Connection in steps S 138  and S 140  and sends an A9-Release-A8 Complete message to the S-BSC  103  in step S 139 . The S-BSC  103  terminates an operation of the Trel9 timer.  
           [0029]    Then, the S-BSC  103  transmits a Clear Complete message to the MSC  111  in step S 141 .  
           [0030]    In step S 143 , the S-PDSN  121  initializes the closure of the A10 Connection with the S-PCF  105  by sending an All-Registration Update message to the S-PCF  105 .  
           [0031]    The S-PCF  105  provides the S-PDSN  121  with an All-Registration Ack message as a response in step S 145 . Further, the S-PCF  105  sets a lifetime to 0 and transmits an All-Registration Request message and accounting related information to the S-PDSN  121  in step S 147 .  
           [0032]    The S-PDSN  121  stores the received accounting related information for a subsequent process and sends an All-Registration Reply message to the S-PCF  105  in step S 149 . Meanwhile, the S-PCF  105  closes the A10 Connection for the MS  101 .  
           [0033]    In step S 151 , the T-PCF  109  provides an All-Registration Request message to the T-PDSN  123  so as to update the registration of the A 10  Connection to the T-PDSN  123 . The All-Registration Request message is used in transmitting the accounting related information and other information and the accounting related information and the other information are transmitted at a system defined trigger point.  
           [0034]    For the verified All-Registration Request message, the T-PDSN  123  transmits the All-Registration Reply message together with the accept indication and the determined lifetime in step S 153 .  
           [0035]    Referring to FIG. 2, there is shown a flow diagram depicting a PPP re-establishment and MIP re-registration procedure described in FIG. 1. As illustrated in FIG. 2, the T-PDSN  123  establishes a PPP session with the MS  101  and a PPP authentication is not used for an MIP service. After initializing the PPP, the T-PDSN  123  transmits an Agent Advertisement message to the MS  101  and the MS  101  also sends an Agent Solicitation message to the T-PDSN  123 .  
           [0036]    The MS  101  generates an MIP Registration Request message to the packet network. The T-PDSN  123  packetizes the Registration Request message provided from the MS  101  by using an AAA protocol to thereby produce an AA-Mobile-Node Request (AMR) message to a local AAA RADIUS server (AAA-L). The local AAA server uses a network access ID (NAI) so as to transmit the AMR message to an appropriate home AAA server (AAA-H). The AMR message is totally transmitted by using a security association (SA) between a visiting network and a home network.  
           [0037]    The AAA-H verifies a location of a home agent (HA) by using an HA IP address of a mobile node and re-packetizes the AMR message to produce a Home-Agent-MIP-Request (HAR) message. The HA processes the MIP registration procedure of the MS  101  and generates a Home-Agent-MIP-Registration-Answer (HAA) to the AAA-H.  
           [0038]    The AAA-H packetizes the HAA message to produce an AA-Mobile-Node-Answer (AMA) to the local AAA server (AAA-L).  
           [0039]    The local AAA server transmits the AMA to the T-PDSN  123 .  
           [0040]    The T-PDSN  123  generates an MIP Registration Reply message to the MS  101 .  
           [0041]    If user data are actuated between the MS  101  and the PDSN by using the PPP session, it is possible to transmit AAA interim accounting records to the local AAA server (AAA-L) and proxy them to the home AAA server (AAA-H).  
           [0042]    As described above, according to the inter-PDSN hard handoff procedure of the prior art, during the steps S 111  to S 134  being performed, the data transmitted from the S-PDSN  121  are not delivered to users, i.e., the MS  101 . Moreover, since there exist an A8 and A10 connection time between nodes and a PPP re-establishing and MIP re-registering time between the MS  101  and the T-PDSN  123 , there occurs a substantially large time delay.  
           [0043]    Therefore, in order to prevent data loss due to the time delay, there need regular doses of buffers in a node. However, although there are prepared the buffers, in case a size of data stored in the buffers exceeds the capacity of the buffers, there inevitably occurs a severe problem of causing the data loss.  
           [0044]    That is, there is a problem that the existing inter-PDSN hard handoff performing method employed in the third generation IMT-2000 synchronous packet data network is improper to processing the packet data requiring fast transmission without data loss, i.e., real-time services.  
           [0045]    Specifically, since the hard handoff performing method defined in the third generation synchronous IMT-2000 wireless packet network cannot provide fast and seamless real-time services since there is the time delay when the handoff is performed in the active mode, it is difficult to provide real-time audio/video packet data services such as VoIP.  
         SUMMARY OF THE INVENTION  
         [0046]    It is, therefore, a primary object of the present invention to provide an inter-PDSN hard handoff performing method capable of providing a fast inter-packet data service without data loss by establishing a link between BSCs via an MSC in case of an active packet session mode in a third generation synchronous IMT-2000 wireless packet communication network.  
           [0047]    In accordance with the present invention, there is provided a method for performing an inter-packet data service node (PDSN) hard handoff, comprising the steps of: setting up a channel link passing through a target base station controller (T-BSC), a source base station controller (S-BSC), a source packet control function (S-PCF) and a source-PDSN (S-PDSN) by establishing a channel link between the S-BSC and the T-BSC via a mobile station center (MSC) in an active packet session mode; performing the hard handoff between the S-BSC, the T-BSC and a mobile station (MS); and transmitting or receiving user packet data exchanged between the MS and the T-BSC through the established channel link to or from the S-PDSN in case the hard handoff is completed.  
           [0048]    In accordance with the present invention, it is possible to perform a packet hard handoff without packet data loss by reducing a time delay caused in a handoff procedure performed during a packet data session of an active mode in an inter-PDSN.  
           [0049]    In particular, in case it is impossible to directly establish a link between a T-BSC and an S-BSC measuring a power strength of a wireless signal transmitted from an MS in the active mode, the hard handoff is performed by establishing a link between the S-BSC and an MSC by transmitting a circuit identification code (CIC) of the S-BSC when the S-BSC sends a Handoff Required message to the MSC and, meanwhile, establishing a link between the T-BSC and the MSC by transmitting a CIC of the MSC when the MSC sends a Handoff Request message to the T-BSC.  
           [0050]    Therefore, during performing the hard handoff procedure in the active mode, the S-BSC can continuously maintain a link with an S-PCF as an anchor and transmit packets to the MS.  
           [0051]    Furthermore, when the inventive hard handoff procedure is completed, by establishing a link between the T-BSC, a T-PCF and the T-PDSN after being converted to a dormant mode, it is possible to provide packet data services in a next active mode without data loss and time delay due to the link establishment and the PPP/MIP re-establishment/re-registration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0052]    The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0053]    [0053]FIG. 1 provides a call-processing flow diagram showing an inter-PDSN hard handoff procedure defined in IS-835 and IOS V4.x;  
         [0054]    [0054]FIG. 2 shows a flow diagram representing a PPP re-establishment and MIP re-registration procedure described in FIG. 1;  
         [0055]    [0055]FIG. 3 describes a call-processing flow diagram representing an inter-PDSN hard handoff procedure in accordance with the present invention;  
         [0056]    [0056]FIG. 4 is a conceptual diagram depicting a link established between BSCs via an MSC when performing an inter-PDSN hard handoff in an active mode in accordance with the present invention; and  
         [0057]    [0057]FIG. 5 illustrates a conceptual diagram showing a flow of packet data transmitted through a link established between an S-BSC and a T-BSC via an MSC when performing an inter-PDSN hard handoff in an active mode in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0058]    Hereinafter, with reference to the accompanying drawings, some preferred embodiments of the present invention would be explained in detail. Hereinafter, when assigning reference numerals to components constructing each drawing, same components are represented by an identical reference numeral although they are shown in different drawings.  
         [0059]    Referring to FIG. 3, there is illustrated a procedure rapidly supporting an inter-PDSN hard handoff without data loss by establishing a link between BSCs via an MSC in an active mode of a synchronous IMT-2000 wireless packet network. FIG. 3 describes a call-processing flow diagram representing the inter-PDSN hard handoff procedure in accordance with the present invention.  
         [0060]    When a message showing that a signal strength of a mobile station (MS)  101  became over a given signal strength threshold defined in a network and the MS  101  will convert to another access network identifier (ANID) is transmitted from the MS  101  to a S-BSC  103 , the S-BSC  103  sends a Handoff Required message including a cell list within a domain of a T-BSC  107  to an MSC  111  in step S 201  and actuates a T7 timer. The Handoff Required message contains a previous ANID (PANID).  
         [0061]    Further, the Handoff Required message includes a circuit identification code (CIC) value delivering call resources of the S-BSC  103  as an extender.  
         [0062]    The MSC  111  selects the T-BSC  107  having an available wireless channel from the cell list, adds the PANID and a hard handoff indicator to a Handoff Request message and transmits the Handoff Request message to the T-BSC  107  in step S 203 . The Handoff Request message contains a CIC value therein.  
         [0063]    In step S 205 , the T-BSC  107  establishes an ATM-based link channel via the MSC  111  between the S-BSC  103  and the T-BSC  107  by allocating appropriate idle wireless resources as receiving the Handoff Request message. Meanwhile, a S-PDSN  121  continuously transmits forward packet data to the S-BSC  103  through an S-PCF  105 .  
         [0064]    Moreover, the T-BSC  107  transfers null traffic channel data to the MS  101  through a forward traffic channel.  
         [0065]    Then, in step S 207 , the T-BSC  107  allows the MS  101  to be tuned to a corresponding wireless channel by transmitting a Handoff Request Ack message including appropriate wireless channel information to the MSC  111  and actuates a T9 timer so as to wait for the signal receiving from the MS  101  through the corresponding wireless channel.  
         [0066]    In accordance with the present invention, although the hard handoff is performed in the active mode, there are not performed an A8/A9 Connection process and a PPP/MIP re-establishing/re-registering process between the T-BSC  107  and a T-PCF  109  and the A8/A9 Connection and PPP/MIP re-establishing/re-registering process will be executed in a dormant mode as described herein below.  
         [0067]    The MSC  111 , which received the Handoff Request Ack message, prepares a call switching from the S-BSC  105  to the T-BSC  107  and sends a Handoff Command message including the wireless channel information provided from the T-BSC  107  to the S-BSC  103  in step S 209 . Then, the S-BSC  103  terminates an operation of the T7 timer.  
         [0068]    In step S 211 , the S-BSC  103  transmits a general handoff direction message (GHDM) or a universal handoff direction message (UHDM) to the MS  101  and actuates a Twaitho timer so as to allow the MS  101  to return to the S-BSC  103 .  
         [0069]    The MS  101  provides the S-BSC  103  with an MS Ack Order message as a response to the GHDM or UHDM in step S 213 .  
         [0070]    In step S 215 , the S-BSC  103  sends a Handoff Commenced message to the MSC  111  so as to notify that the MS  101  is instructed to move to a channel of the T-BSC  107 . The Handoff Commenced message is transmitted after an operation of the Twaitho timer is terminated.  
         [0071]    If the MS  101  completes the hard handoff procedure by obtaining synchronization through the use of a backward communication channel frame or preamble data, the MS  101  transmits a Handoff Completion message to the T-BSC  107  in step S 217  and the T-BSC  107  which received the Handoff Completion message transmits a BSC Ack Order message to the MS  101  in step S 219 .  
         [0072]    In step S 221 , after the T-BSC  107 , which received the Handoff Completion message, detects that the MS  101  is connected to the T-BSC  107 , the T-BSC  107  transmits a Handoff Complete message to the MSC  111  so as to notify that the hard handoff is successfully performed for the MS  101  and terminates an operation of the T9 timer.  
         [0073]    After then, user packet data transmitted from the MS  101  are delivered to the S-BSC  103  via the T-BSC  107  and the MSC  111 . At this time, the S-BSC  103  exists as an anchor and continuously transmits packet data to the other node of the wireless packet data network through the S-PCF  105  and the S-PDSN  121  until the active mode is converted to the dormant mode. Likewise, the packet data arrived at the MS  101  from the other node are delivered in an order of the S-PDSN  121 , the S-PCF  105 , the S-BSC  103 , the MSC  111  and the T-BSC  107 .  
         [0074]    Therefore, since the S-BSC  103  plays a role of the anchor, there is no need to re-establish the A8/A9 Connection between the T-BSC  107  and the T-PCF  109  and the A10/A11 Connection between the T-PCF  109  and the T-PDSN  123 , respectively.  
         [0075]    Further, the PPP/MIP re-establishing/re-registering process is omitted. As a result, it is possible to prevent a time delay required in establishing a link and performing the PPP/MIP re-establishing/re-registering process in the conventional handoff scheme.  
         [0076]    Referring to FIG. 4, there is shown a conceptual diagram depicting a link established between BSCs via an MSC when performing the inter-PDSN hard handoff in the active mode in accordance with the present invention. FIG. 5 illustrates a conceptual diagram showing a flow of packet data transmitted through a link established between an S-BSC and a T-BSC via an MSC when performing the inter-PDSN hard handoff in the active mode in accordance with the present invention. In FIG. 5, reference numerals 1 to 9 represent a flow of data packets before the handoff and reference numerals  10  and  11  describe a flow of data packets after the handoff.  
         [0077]    As illustrated in FIGS.  3  to  5 , since there is already established a channel link between the S-BSC  103  and the T-BSC  107  via the MSC  111  and the S-BSC  103  is determined as an anchor although the hard handoff of the inter-PDSN is executed in the active mode by performing the above handoff procedure in accordance with the present invention, it is possible to transmit the packet data to the wireless packet data network through the S-PCF  105  and the PDSN  121  by the channel link to the S-BSC  103  established via the MSC  111  even though packet data are exchanged through a wireless link established between the MS  101  and the T-BSC  107  by executing the hard handoff.  
         [0078]    Accordingly, since the process for establishing the A8/A9/A10/A11 Connection between the T-BSC  107 , the T-PCF  109  and the T-PDSN  123  and the PPP/MIP re-establishing/re-registering process are omitted, the time delay due to the hard handoff is substantially reduced and, thus, it is possible to provide seamless fast packet data services.  
         [0079]    The process for setting up the A8/A9/A10/A11 Connection between the T-BSC  107 , the T-PCF  109  and the T-PDSN  123  and the PPP/MIP re-establishing/re-registering process are performed in the dormant mode described herein below.  
         [0080]    As depicted in FIG. 3, after the T-BSC  107  detects that there is no packet data provided from the MS  101  or the S-BSC  103  anymore by actuating a timer, the active mode is converted to the dormant mode. Then, in order to set up the A8-Connection with the T-PCF  109 , an A9-Setup-A8 message is transmitted to the T-PCF  109  and a TA8-Setup timer is actuated in step S 105 .  
         [0081]    The T-PCF  109 , which received the A9-Setup-A8 message, sets up the A8-Connection and, then, provides an A9-Connect-A8 message to the T-BSC  107  in step S 107 . Meanwhile, the T-BSC  107 , which received the A9-Connect-A8 message, stops an operation of the TA8-Setup timer.  
         [0082]    Furthermore, there is established an A10/A11 Connection between the T-PCF  109  and the PDSN  121  in step S 225 . As a result, the A8/A9/A10/A11 Connection is set up between the MS  101 , the T-BSC  107 , the T-PCF  109  and the T-PDSN  123 .  
         [0083]    Then, as shown in FIG. 2, a PPP link layer connection is set up between the MS  101  and the T-PDSN  123  and the MIP registering procedure is performed between the wireless packet network and the MS  101  in step S 229 . If the registration is completed, the user packet data are exchanged between the MS  101  and an opposite MS through the A10 Connection.  
         [0084]    In step S 135 , the MSC  111  supplies a Clear Command message to the S-BSC  105  and the MSC  111  actuates a T315 timer.  
         [0085]    The S-BSC  103  transmits an A9-Release-A8 message to the S-PCF  105  so as to release the A8-Connection with the S-PCF  105  and actuates a Trel9 timer in step S 137 .  
         [0086]    The S-PCF  105  releases the A8-Connection and generates an A9-Release-A8 Complete message as a response in step S 139 . The S-BSC  103  terminates an operation of the Trel9 timer.  
         [0087]    Then, the A10 Connection between the S-PCF  105  and the S-PDSN  121  is released and its state is updated in step S 227 .  
         [0088]    Finally, the S-BSC  103  provides the MSC  111  with a Clear Complete message to thereby terminate the inter-PDSN hard handoff procedure in step S 141 .  
         [0089]    According to the hard handoff procedure in accordance with the present invention, a CIC is used as an extender when the S-BSC  103  transmits the Handoff Required message to the MSC  111  in the active mode and transmitted when the MSC  111  sends the Handoff Request message to the T-BSC  107  to thereby establish a link between BSCs via the MSC  111 , so that the hard handoff procedure can support the hard handoff by using the communication between the BSCs.  
         [0090]    When the handoff occurs, packet data transmitted from the MS  101  to the T-BSC  107  are provided to the S-BSC  103  through a channel link established by the CIC and transmitted to the wireless packet data network through the S-PCF  105  and the S-PDSN  121 .  
         [0091]    Herein, the S-BSC  103  plays a role of the anchor in the active mode to thereby allow the packet data passing through the T-BSC  107  to go through not the T-PCF  109  but the S-BSC  103  although the handoff occurs, so that the time delay due to the A8/A9/A10/A11 Connection and the PPP/MIP re-establishing/re-registering process between the MS  101 , the T-BSC  107 , the T-PCF  109  and the T-PDSN  123  is reduced.  
         [0092]    After executing the handoff, the anchor state of the S-BSC  103  is released in the dormant mode.  
         [0093]    After the handoff, when the MS  101  existing at the cell domain of the T-BSC  107  is converted to the dormant mode, by setting up the A8/A9 Connection between the T-BSC  107  and the T-PCF  109  and the A10/A11 Connection between the T-PCF  109  and the T-PDSN  123  and performing the PPP/MIP re-establishing/reregistering process, there is no need to newly establish the A8/A9/A10/A11 Connection and to perform the PPP/MIP re-establishing/re-registering process when the dormant mode is converted to the active mode again. As a result, it is possible to reduce the time delay caused by the link establishment.  
         [0094]    Accordingly, compared to the prior art, the present invention can provide the packet data services without a break and data loss.  
         [0095]    As described above, the inventive handoff performing method can support the handoff without a break by performing the fast hard handoff in the packet wireless communication network.  
         [0096]    Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Technology Classification (CPC): 7