Abstract:
The present disclosure relates generally to systems and methods for a handoff in a wireless network. In one example, a method for handing off a mobile device includes receiving configuration information from the mobile device at a first base station supporting a first communication session between the mobile device and a first packet data node. The configuration information may be forwarded to a second base station for handoff of the mobile device from the first base station to the second base station. A second communication session may be negotiated between the second base station and a second packet data node using the configuration information. Information corresponding to the second communication session may be sent to the mobile device to enable the mobile device to connect to the second packet data node using the second communication session.

Description:
BACKGROUND 
       [0001]    Communications networks, such as those that can support wireless voice and/or data, generally support the movement of a mobile device from one area of the network (e.g., a cell) to another. In order to provide such support, a network should support the transfer (e.g., handoff) of the mobile device between areas. One type of commonly used handoff is a hard handoff. In a hard handoff scenario, the connection between the mobile device and the network area that the mobile device is leaving is terminated before the connection between the mobile device and the network area that the mobile device is entering is established. In other words, there is a temporary break in the connection between the mobile station and the network. 
         [0002]    Although a hard handoff may not present a problem with certain types of traffic, such as circuit switched voice traffic, such a break in the connection may be detrimental to packet-switched traffic classes such as Voice over Internet Protocol (VoIP) data. Furthermore, the longer the break, the more detrimental it may be to the connection. Accordingly, improvements are needed in handing off a mobile device from one area of a network to another. 
       SUMMARY 
       [0003]    In one embodiment, a method for handing off a mobile device is provided. The method comprises receiving configuration information from the mobile device at a first base station supporting a first communication session between the mobile device and a first packet data node. The configuration information is forwarded to a second base station for handoff of the mobile device from the first base station to the second base station. A second communication session is negotiated between the second base station and a second packet data node using the configuration information. Information corresponding to the second communication session is sent to the mobile device to enable the mobile device to connect to the second packet data node using the second communication session. 
         [0004]    In another embodiment, a method for use by a first base station in a wireless network is provided. The method comprises receiving configuration information from a mobile device, wherein the information represents configuration parameters of a packet data connection existing between the mobile device and a packet data node. The mobile device is identified as needing to be handed off to a second base station, and the configuration information is forwarded to the second base station. 
         [0005]    In still another embodiment, a method for use by a first base station in a wireless network is provided. The method comprises receiving configuration information from a second base station, wherein the information represents configuration parameters of a first packet data connection existing between a mobile device currently serviced by the second base station and a first packet data node. A second packet data connection is negotiated with a second packet data node using the configuration parameters, and information corresponding to the second packet data connection is sent to the mobile device. 
         [0006]    In yet another embodiment, a system is provided. The system comprises a first base station coupled to a second base station, a first packet data node coupled to the first base station, a second packet data node coupled to the second base station, and a plurality of instructions for execution within the system. The instructions include instructions for receiving configuration information at the first base station from a mobile device, wherein the configuration information includes parameters of a first packet data session between the mobile device and the first packet data node. The instructions also include instructions for negotiating a second packet data session between the second base station and the second packet data node using the configuration information. The instructions also include instructions for sending information corresponding to the second packet data session to the mobile device, wherein the mobile device can use the second packet data session without having to negotiate the second packet data session with the second packet data node. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
           [0008]      FIG. 1  is a flowchart illustrating one embodiment of a method for performing a handoff in a wireless network. 
           [0009]      FIG. 2  is a diagram of one embodiment of a wireless network within which the method of  FIG. 1  may be implemented. 
           [0010]      FIG. 3  is a flowchart illustrating one embodiment of a method that may be used within the network of  FIG. 2  to receive configuration information from a mobile device and forward the configuration information within the network. 
           [0011]      FIG. 4  is a flowchart illustrating one embodiment of a method that may be used within the network of  FIG. 2  to negotiate a network connection on behalf of a mobile device. 
           [0012]      FIG. 5  is a diagram illustrating one embodiment of a message sequence that may be used for executing a handoff within the system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
         [0014]    Referring to  FIG. 1 , in one embodiment, a method  100  may be used to optimize the establishment of a communication session during a handoff procedure. In the present example, a mobile device is being handed off from one cell in a communication network to another cell. The mobile device is engaged in a packet data communication session using protocols such as a mobile internet protocol (MIP) and a point-to-point protocol (PPP) over a network connection provided by the communications network. The network connection provided by the communication network may include multiple connections, such as an air traffic channel between the mobile device and a base station, and a transport channel between the base station and a packet-switched node (e.g., a packet data node such as a Packet Data Serving Node (PDSN)) connecting the mobile device to a packet network such as the Internet. 
         [0015]    In a traditional communication network, such as wireless access networks based on Code Division Multiple Access 2000 (CDMA2000) technology, a base station may initiate a hard handoff of an active packet data call to another base station. The base station that receives the call after the handoff (referred to as the Target BS or BS-T) may be connected to a PDSN other than the one to which the originating BS (called the Source BS or BS-S) is connected. Normally, this results in re-negotiations for protocols such as PPP and MIP (if being used by the mobile device) when the mobile device has successfully been handed off. However, this re-negotiation between the mobile device and the PDSN may be disruptive to packet data traffic and may degrade a sensitive application such as VoIP. 
         [0016]    To accomplish the handoff without such re-negotiations, the communication network may pass a pair of IP addresses for the originating PDSN (PDSN-S) to the BS-T via handoff messages. The BS-T may then attempt to contact the PDSN-S directly using one of the IP addresses or, if this is not possible, may send the second IP address to the PDSN-T. The PDSN-T may then attempt to establish a PPP connection to the PDSN-S over an IP network connecting both PDSNs. It is noted that two IP addresses may be passed because the IP network may be different than the network connecting each base station to its respective PDSN. If the PDSN-T is connected to the PDSN-S by the same IP network, the PDSN-T may establish a PPP connection with the PDSN-S and tunnel any traffic to or from the mobile device to the PDSN-S over this tunnel. This may eliminate the need to re-negotiate PPP and MIP when the mobile device is handed off to the BS-T and PDSN-T, although the PDSN-T should be able to contact the PDSN-S for such tunneling to occur. However, if the PDSN-T cannot contact the PDSN-S, then the mobile device will need to renegotiate the connection with the PDSN-T. 
         [0017]    The method  100  may be used to optimize the negotiation of a packet data session for use between the mobile device and the PDSN-T. In step  102 , the base station currently coupled to the mobile device via the air traffic channel (e.g., the BS-S) receives configuration information from the mobile device. As will be described later in greater detail, the configuration information may include various parameters corresponding to the session between the mobile device and the PDSN-S. In step  104 , the BS-S forwards the configuration information to another base station (e.g., the BS-T) for handoff of the mobile device. 
         [0018]    In step  106 , the BS-T receiving the mobile device during handoff may negotiate a communication session with the PDSN-T using the configuration information. In step  108 , after negotiating the new communication session with the PDSN-T, the BS-T sends information corresponding to the new session to the mobile device. This enables the mobile device to connect to the PDSN-T using the second communication session without having to negotiate the new session itself. Accordingly, the BS-T may act as a proxy for the mobile device during negotiations with the PDSN-T and optimize the handoff process. 
         [0019]    Referring to  FIG. 2 , a communications network  200  illustrates one embodiment of a system within which the method  100  of  FIG. 1  may be used. In the present example, the network  200  is a CDMA network that may be compatible with a variety of standards including, but not limited to, Interim Standard 95 (IS-95), Interim Standard 2000 (IS-2000) and Universal Mobile Telecommunications System (UMTS). The network  200  may represent other technologies, including Global System for Mobile communication (GSM), and Orthogonal Frequency Division Multiplexing (OFDM). Accordingly, it is understood that the methods of the present disclosure may be performed in networks based on different technologies, such as High Rate Packet Data-based Radio Access Networks (HRPD-based RANs) and that the examples using a CDMA network are for purposes of illustration only. 
         [0020]    The network  200  comprises a plurality of cells  202   a ,  202   b . In the present example, the network  200  is a wireless network, and may be connected to other wireless and/or wireline networks, such as packet networks  204   a ,  204   b . Each cell  202   a ,  202   b  in the network  200  includes a base station (BS)  206   a ,  206   b , respectively, that are coupled to base station controllers (BSC)  208   a ,  208   b , respectively. A mobile switching center (MSC)  210  may be used to connect the network  200  with other networks such as a Public Switched Telephone Network (PSTN) (not shown). Although not shown, the base stations  206   a  and  206   b  may be coupled to the same BSC, and the BSCs  208   a  and  208   b  may be coupled to separate MSCs. 
         [0021]    The BSCs  208   a ,  208   b  are also coupled to packet-switched nodes (e.g., packet data nodes such as PDSNs)  212   a ,  212   b , respectively, each of which is coupled to one of the packet networks  204   a ,  204   b . The terms “packet” and “packet data”, as used in the present disclosure, may be interchangeable and may include any type of encapsulated data, including datagrams, frames, packets, and the like, and the encapsulated information may include voice, video, data, and/or other encapsulated information. The packet networks  204   a ,  204   b  may be the same network or separate networks, and may be any combination of private and public networks based on any packet technology, such as the Internet Protocol (IP) and the Transport Control Protocol (TCP). 
         [0022]    The network  200  enables a mobile device  214  to communicate with another device (not shown) via the BTS  206   a  associated with the cell  202   a  in which the mobile device is located. Although illustrated in  FIG. 2  as a cellular phone, it is understood that the mobile device  214  may be any portable device capable of wirelessly participating in a packet session, and such devices may include personal digital assistants, portable computers, pagers, and/or cellular phones. The cells  202   a ,  202   b  overlap so that the mobile device  214  may travel from one cell to another (e.g., from the cell  202   a  to the cell  202   b ) while maintaining a communication session. In a handoff region  216  (e.g., the area where the cells  202   a ,  202   b  overlap), the mobile device  214  may be serviced by both the BTS  206   a  and the BTS  206   b.    
         [0023]    Referring to  FIG. 3 , in one embodiment, a method  300  may be executed within a system, such as the system  200  of  FIG. 2 , to aid in handing off a mobile device&#39;s packet data session from one cell to another cell. In the present example, the method  300  may be executed within a base station (e.g., the base station  206   a ), but it is understood that at least portions of the method may be executed elsewhere, such as in the BSC  208   a , and that various steps of the method may be performed by different network elements. Furthermore, messages may actually be sent and received via network elements (e.g., the BSCs  208   a ,  208   b , and MSC  210 ) that have been omitted from the present embodiment for purposes of illustration. 
         [0024]    In the present example, the method  300  begins after a connection between the base station  206   a  and the mobile device  214  has been established, and the mobile device has established a packet data session with the PDSN  212   a  using MIP and PPP. In step  302 , the base station  206   a  receives configuration information (e.g., parameters) from the mobile device  214 . Examples of such configuration parameters for MIP and PPP may include indicators for simultaneous bindings, broadcast datagrams, decapsulation by mobile node, minimal encapsulation, generic routing encapsulation (GRE), and/or use of Van Jacobson header compression. The mobile station  214  may also send the home address, care-of address, and home agent IP address being used by the mobile device, as well as an identifier such as a 64-bit identification number being used by the mobile device. Examples of configuration parameters that may be sent by the mobile device  214  to the base station  206   a  for PPP include an identifier for the mobile device, as well as options that may be used during the PPP negotiations with the PDSN. Such options may include Maximum-Receive-Unit, Authentication-Protocol, Quality-Protocol, Protocol-Field-Compression, and/or Address-and-Control-Field-Compression. 
         [0025]    In step  304 , the base station  206   a  may determine that the mobile device  214  needs to be handed off to another base station, such as the base station  206   b . This determination may be made by the base station  206   a  or may be made elsewhere and communicated to the base station. 
         [0026]    In step  306 , in addition to handoff related messaging, the base station  206   a  may send various configuration parameters to the base station  206   b . In the present example, the parameters may be sent with the handoff messages (e.g., inserted into a field of a handoff message or otherwise encapsulated therewith) or may be sent separately. 
         [0027]    Examples of such configuration parameters for MIP may include indicators for simultaneous bindings, broadcast datagrams, decapsulation by mobile node, minimal encapsulation, generic routing encapsulation (GRE), and/or use of Van Jacobson header compression. The base station  206   a  may also send the home address, care-of address, and home agent IP address being used by the mobile device  214 , as well as an identifier such as a 64-bit identification number being used by the mobile device. 
         [0028]    Examples of configuration parameters that may be sent by the base station  206   a  to the base station  206   b  for PPP include an identifier for the mobile device  214 , as well as options that may be used by the base station  206   b  during the PPP negotiations with the PDSN  212   b . Such options may include Maximum-Receive-Unit, Authentication-Protocol, Quality-Protocol, Protocol-Field-Compression, and/or Address-and-Control-Field-Compression. 
         [0029]    It is understood that the parameters provided are for purposes of illustration and are not intended to be limiting. Accordingly, other parameters may be used and such parameters may vary depending on such factors as the particular protocol or protocols being used, as well as the configuration of the network within which the parameters are implemented. Furthermore, if such parameters are not supported by the network  200  or a particular portion of the network (e.g., the base station  206   b ), then the parameters may be ignored. For example, if the base station  206   a  does not support the parameters received from the mobile device  214 , the base station may ignore them and process the call normally. If the base station  206   a  supports the parameters but the base station  206   b  does not, the base station  206   b  may receive the parameters and ignore them. Alternatively, the base station  206   a  may not send the parameters to the base station  206   b  if the base station  206   b  does not support them. Accordingly, the transfer of the parameters between the elements of a network (or between different networks) may be implemented in different ways. 
         [0030]    In step  308 , the base station  206   a  may instruct the mobile device  214  to switch to the base station  206   b . It is understood that messages commonly used during a handoff process may be exchanged during the method  300 , but is not shown for purposes of clarity. 
         [0031]    Referring to  FIG. 4 , in another embodiment, a method  400  may be executed within a system, such as the system  200  of  FIG. 2 , to aid in handing off a mobile device&#39;s packet data session (based on MIP and PPP) from one cell to another cell. In the present example, the method  300  may be executed within a base station (e.g., the base station  206   b ), but it is understood that the method may be executed elsewhere, such as in the BSC  208   b.    
         [0032]    In step  402 , the base station  206   b  receives configuration information from the base station  206   a . As discussed with respect to  FIG. 3 , this information may include various identifiers and parameters corresponding to the mobile device  214  and a packet data communication session with which the mobile device is involved. In step  404 , the base station  206   b  may attempt to connect to the PDSN  212   a . If the connection attempt is successful, the base station  206   b  may support the established session between the PDSN  212   a  and the mobile device  214  in step  406 . If the base station  206   b  cannot connect to the PDSN  212   a , the base station may enter into negotiations with the PDSN  212   b  in step  408  to establish a new session using the configuration parameters received in step  402 . For example, if the session between the mobile device  214  and PDSN  212   a  uses MIP and PPP, the base station  206   b  may conduct MIP and PPP negotiations with the PDSN  212   b . Accordingly, the base station  206   b  may act as a proxy for the mobile device  214  and negotiate the connection before the mobile device may do so itself 
         [0033]    In step  410 , once the negotiation is complete and the connection is established, the base station  206   b  may send the new MIP and PPP information to the mobile device  214 . The mobile device  214  may then connect to the new PDSN  212   b  without having to negotiate the connection with the PDSN  212   b . It is understood that messages commonly used during a handoff process may be exchanged during the method  400 , but is not shown for purposes of clarity. 
         [0034]    Referring to  FIG. 5 , one embodiment of a message sequence  500  that may be used to hand off a mobile device is provided. For purposes of example, the mobile device is the mobile device  214  of  FIG. 2 , the BS-S is the base station  206   a  of  FIG. 2 , the BS-T is the base station  206   b  of  FIG. 2 , the MSC is the MSC  210  of  FIG. 2 , and the PDSN-T is the PDSN  212   b  of  FIG. 2 . 
         [0035]    In step  502 , the mobile device  214  sends configuration information to the BS-S  206   a . As described previously, the configuration information may represent various identifiers and parameters associated with the mobile device  214  and a packet data session between the mobile device and the PDSN-S  212   a  ( FIG. 2 ). In step  504 , the mobile device  214  may send a message such as a pilot strength measurement message to the BS-S  206   a . Based on the pilot strength measurement message, the BS-S  206   a  may determine in step  506  whether a handoff is needed. Steps  504  and  506  may repeat until the call ends (if no handoff is needed) or until the BS-S  206   a  determines that a handoff is needed. Once the need for a handoff is determined, the BS-S  206   a  sends a message such as a Handoff Required message and the configuration information (either within or separate from the Handoff Required message) to the MSC  210 . It is understood that if the base stations  206   a  and  206   b  are not connected to the same MSC, inter-MSC communication may be needed. One example of such inter-MSC communication is described in the IS-41 standard, which is hereby incorporated by reference in its entirety. 
         [0036]    In step  510 , the MSC  210  may send the configuration information to the BS-T  206   b  with a message such as a Handoff Request message. As with the Handoff Required message, the configuration information may be sent with the Handoff Request message (e.g., encapsulated therein) or may be sent separately. In the present example, although a step for contacting the PSDN-S  212   a  is not illustrated, such a step may occur in the sequence  500 . For example, step  404  of  FIG. 4  may be implemented between steps  510  and  512 . In step  512 , the BS-T  206   b  sends a message such as a Registration Request message to the PDSN-T  212   b . In step  514 , the PDSN-T  212   b  sends a message such as a Registration Response message to the BS-T  206   b  and the BS-T may then send a message such as a Handoff Request Ack message to the MSC  210  to acknowledge the handoff request in step  516 . 
         [0037]    In step  518 , the BS-T  206   b  may act as a proxy for the mobile device  214  and conduct negotiations (e.g., MIP and PPP negotiations) with the PDSN-T  212   b  to establish a connection. It is understood that the negotiations of step  518  may begin before the message of step  516  and may not end until after step  524 . 
         [0038]    In steps  520  and  522 , the handoff process may continue as the MSC  210  sends a message such as a Handoff Command message to the BS-S  206   a  and the BS-S sends a message such as a Universal Handoff Direction message to the mobile device  214  instructing the mobile device to switch to the BS-T  206   b . In step  524 , the mobile device  214  and the BS-T  206   b  may exchange null traffic frames until the mobile device is under power control of the BS-T. 
         [0039]    In step  526 , the BS-T  206   b  may send the configuration information to the mobile device  214  for the new connection established by the BS-T acting as proxy for the mobile device. In the present example, such information may include MIP and PPP parameters. The mobile device  214  may then connect to the PDSN-T  212   b  after receiving the information in step  526  without having to negotiate the packet data connection with the PDSN-T itself. Accordingly, the handoff process may be optimized by enabling a connection with the PDSN-T  212   b  to be established while handoff is occurring, rather than waiting for the mobile device  214  to be handed off to the BS-T  206   a  before beginning negotiations for the connection. 
         [0040]    It is understood that various messages, such as those between the MSC  210 , the base stations  206   a  and  206   b , the PDSNs  212   a  and  212   b , and other network elements (such as the BSCs  208   a  and  208   b ) may be performed in accordance with one or more specified standards, such as TIA-2001, which is hereby incorporated by reference. As stated previously, inter-MSC communication may be performed as described in previously incorporated IS-41. It is understood that the message sequence  500  and the particular messages described are only one example of many possible sequences and that the functionality provided by the sequence  500  may be achieved using different sequences and/or messages. 
         [0041]    Although only a few exemplary embodiments of this disclosure have been described in details above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. For example, various steps from different flow charts may be combined, performed in an order different from the order shown, or further separated into additional steps. Furthermore, steps may be performed by network elements other than those disclosed. Accordingly, all such modifications are intended to be included within the scope of this disclosure.