Abstract:
A wireless network that provides a packet data call connection between a source mobile station (MS) and a destination mobile station (MS) in a coverage area of the wireless network. The wireless network comprises a first base station that wirelessly communicates with the source mobile station, a second base station that wirelessly communicates with the destination mobile station, and a mobile switching center that connecting the first and second base stations. The first base station receives a first message from the source mobile station requesting a MS-MS packet data call connection to the destination mobile station. In response to the first message, the first base station initiates establishment of the MS-MS packet data call connection on a local IP network coupling the first and second base stations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention is related to that disclosed in U.S. patent application Ser. No. 10/695,595, entitled “SYSTEM AND METHOD FOR PERFORMING HANDOFFS OF MOBILE STATION-TO-MOBILE STATION PACKET DATA CALLS IN A WIRELESS NETWORK” and filed concurrently with the present application. The subject matter disclosed in patent application Ser. No. 10/695,595 is hereby incorporated by reference into the present application as if fully set forth herein. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to wireless communication systems and, more specifically, to a system and a related method for making packet data calls between mobile stations in a wireless network. 
     BACKGROUND OF THE INVENTION 
     Wireless communication systems have become ubiquitous in society. Business and consumers use a wide variety of fixed and mobile wireless terminals, including cell phones, pagers, Personal Communication Services (PCS) systems, and fixed wireless access devices (i.e., vending machine with cellular capability). Wireless service providers continually try to create new markets for wireless devices and expand existing markets by making wireless devices and services cheaper and more reliable. The price of wireless devices has decreased to the point where these devices are affordable to nearly everyone and the price of a wireless device is only a small part of the total cost to the user (i.e., subscriber). To continue to attract new customers, wireless service providers are implementing new services, especially digital data services that, for example, enable a user to browse the Internet and to send and receive e-mail. 
     Subscribers have shown great interest in using high-speed applications between mobile stations in wireless networks. Many of these high-speed applications (e.g., video phones) require a radio access network (RAN) that supports streaming data applications. A streaming data application must be transported over constant bandwidth with low delay and low levels of jitter. However, current wireless networks, such as cdma2000 RANs, often experience problems when supporting streaming data applications. Packet data transmissions between a base station (BS) and a mobile station (MS) experience delay and jitter at numerous points in the network, including at the air interface between the MS and the BS and at the interface between the BS and the packet data serving node (PDSN). 
     Delays and jitter would be minimized if streaming data could be transmitted more directly between mobile stations, without passing through some infrastructure of the radio access network (RAN), such as the PDSN. However, the well-known RAN signaling messages specified in TIA-2001-C, “Interoperability Specification for cdma2000 Access Network Interfaces”, Jun. 2003, (hereafter, simply “the TIA-2001-C standard”) and other standards do not provide for direct mobile-to-mobile (MS-MS) packet data calls. The TIA-2001-C standard only allows for mobile originated packet data calls. 
     All packet data calls use control signals that connect the base station (BS) serving the mobile station (MS) that originates a packet data call to a packet data serving node (PDSN). All data transmitted by a source mobile station is transferred through the PDSN to a packet data network. In the case of MS-MS packet data calls, the data is then transferred back to a base station of the wireless network for subsequent transmission to a destination MS. Obviously, transferring the data up to, and then back from, the PDSN is unnecessary and introduces delays. Additionally, the added signaling needed to establish connections to the PDSN increases call set up time and decreases success rates. 
     U.S. patent application No. 20,020,077,096 (hereafter, the “Jin application”) discloses a method for providing mobile station-to-mobile station data calls, provided the same base station (BS) serves both mobile stations. The method disclosed in the Jin application establishes MS-MS packet data calls without requiring connections between the BS and the PDSN. However, as noted, the mobile stations must be located in cells served by a single base station. This may be acceptable in a small wireless network that uses a single base station (e.g., a home or small office network). However, if a wireless network operator deploys a RAN with many base stations, this is a severe limitation. Subscribers who are distant from each other are served by different base stations and cannot engage in a MS-to-MS streaming data application without going through the PDSN and a wide area packet data network. 
     Therefore, there is a need for improved wireless networks that provide mobile station-to-mobile station (MS-MS) packet data connections that have low delay and low jitter characteristics. In particular, there is a need for a wireless network that provides a MS-MS packet data connection from a first base station to a second base station that does not require a packet data serving node and a wide-area packet data network. More particularly, there is a need for a wireless network that enables an MS-MS packet data connection handled by a first base station and a second base station to be transferred from the first base station to a third base station if one of the mobile stations is handed off from the first base station to the third base station. 
     SUMMARY OF THE INVENTION 
     The present invention enables a cdma2000 wireless network to quickly connect two mobile stations that require a streaming data flow (e.g., a video phone call). The present invention accomplishes this by modifying the well-known radio access network (RAN) signaling messages standardized in TIA-2001-C, “Interoperability Specification for cdma2000 Access Network Interfaces”, Jun. 2003. 
     To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a wireless network that provides a packet data call connection between a source mobile station (MS) and a destination mobile station (MS) in a coverage area of the wireless network. According to an advantageous embodiment of the present invention, the wireless network comprises: i) a first base station capable of wirelessly communicating with the source mobile station; ii) a second base station capable of wirelessly communicating with the destination mobile station; and iii) a mobile switching center capable of connecting the first and second base stations, wherein the first base station is capable of receiving a first message from the source mobile station requesting a MS-MS packet data call connection to the destination mobile station and, in response to the first message, the first base station initiates establishment of the MS-MS packet data call connection on a local IP network coupling the first and second base stations. 
     According to one embodiment of the present invention, the first base station responds to the first message by transmitting a second message to the mobile switching center, the second message indicating that the MS-MS packet data call connection to the destination mobile station is requested. 
     According to another embodiment of the present invention, the mobile switching center responds to the second message by transmitting a third message to the second base station, the third message indicating that the MS-MS packet data call connection is requested. 
     According to still another embodiment of the present invention, the second base station responds to the third message by transmitting a fourth message to the mobile switching center, the fourth message containing an IP address of the second base station on the local IP network. 
     According to yet another embodiment of the present invention, the mobile switching center responds to the fourth message by transmitting a fifth message to the first base station, the fifth message containing the IP address of the second base station and a mobile identifier value associated with the destination mobile station. 
     According to a further embodiment of the present invention, the first base station responds to the fifth message by using the IP address of the second base station to establish a packet data bearer connection to the second base station via the local IP network. 
     According to a still further embodiment of the present invention, the first base station transmits the mobile identifier of the destination mobile station to the second base station in order to identify data packets from the source mobile station that are directed to the destination mobile station. 
     The foregoing has outlined rather broadly several features of this disclosure so that those skilled in the art may better understand the Detailed Description of the Invention that follows. Additional features may be described later in this document. Those skilled in the art should appreciate that they may readily use the concepts and the specific embodiments disclosed as a basis for modifying or designing other structures for carrying out the same purposes of this disclosure. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. 
     Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. A controller may be implemented in hardware, firmware, or software, or a combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, and the advantages thereof, reference is made to the following descriptions and the accompanying drawings, wherein like numbers designate like objects, and in which: 
         FIG. 1  illustrates a wireless network in which the supplemental channel (SCH) may be dynamically allocated according to the principles of the present invention; 
         FIG. 2  is a message flow diagram illustrating the set up of a mobile station-to-mobile station packet data call according to the principles of the present invention; 
         FIG. 3  is a message flow diagram illustrating the handoff between base stations of a mobile station-to-mobile station packet data call according to the principles of the present invention; and 
         FIG. 4  is a message flow diagram illustrating the tear down of a mobile station-to-mobile station packet data call according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 through 4 , discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged wireless communication network. 
       FIG. 1  illustrates an exemplary wireless network in which the supplemental channel (SCH) may be dynamically allocated to a single mobile station according to the principles of the present invention. Wireless network  100  comprises a plurality of cell sites  121 - 123 , each containing one of the base stations, BS  101 , BS  102 , or BS  103 . Base stations  101 - 103  communicate with a plurality of mobile stations (MS)  111 - 114  over code division multiple access (CDMA) channels according to the IS-2000-C standard (i.e., Release C of cdma2000). Mobile stations  111 - 114  may be any suitable wireless devices, including conventional cellular radiotelephones, PCS handset devices, personal digital assistants, portable computers, telemetry devices, and the like, which are capable of communicating with the base stations via wireless links. 
     The present invention is not limited to mobile devices. Other types of wireless access terminals, including fixed wireless terminals, may be used. For the sake of simplicity, only mobile stations are shown and discussed hereafter. However, it should be understood that the use of the term “mobile station” in the claims and in the description below is intended to encompass both truly mobile devices (e.g., cell phones, wireless laptops) and stationary wireless terminals (e.g., monitoring devices with wireless capability). 
     Dotted lines show the approximate boundaries of the cell sites  121 - 123  in which base stations  101 - 103  are located. The cell sites are shown approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the cell sites may have other irregular shapes, depending on the cell configuration selected and natural and man-made obstructions. 
     As is well known in the art, cell sites  121 - 123  are comprised of a plurality of sectors (not shown), where a directional antenna coupled to the base station illuminates each sector. The embodiment of  FIG. 1  illustrates the base station in the center of the cell. Alternate embodiments position the directional antennas in corners of the sectors. The system of the present invention is not limited to any particular cell site configuration. 
     In one embodiment of the present invention, BS  101 , BS  102 , and BS  103  comprise a base station controller (BSC) and at least one base transceiver subsystem (BTS). Base station controllers and base transceiver subsystems are well known to those skilled in the art. A base station controller is a device that manages wireless communications resources, including the base transceiver subsystems, for specified cells within a wireless communications network. A base transceiver subsystem comprises the RF transceivers, antennas, and other electrical equipment located in each cell site. This equipment may include air conditioning units, heating units, electrical supplies, telephone line interfaces and RF transmitters and RF receivers. For the purpose of simplicity and clarity in explaining the operation of the present invention, the base transceiver subsystem in each of cells  121 ,  122 , and  123  and the base station controller associated with each base transceiver subsystem are collectively represented by BS  101 , BS  102  and BS  103 , respectively. 
     BS  101 , BS  102  and BS  103  transfer voice and data signals between each other and the public switched telephone network (PSTN) (not shown) via communication line  131  and mobile switching center (MSC)  140 . BS  101 , BS  102  and BS  103  also transfer data signals, such as packet data, with the Internet (not shown) via communication line  131  and packet data server node (PDSN)  150 . Packet control function (PCF) unit  190  controls the flow of data packets between base stations  101 - 103  and PDSN  150 . PCF unit  190  may be implemented as part of PDSN  150 , as part of base stations  101 - 103 , or as a stand-alone device that communicates with PDSN  150 , as shown in  FIG. 1 . Line  131  also provides the connection path to transfer control signals between MSC  140  and BS  101 , BS  102  and BS  103  used to establish connections for voice and data circuits between MSC  140  and BS  101 , BS  102  and BS  103 . 
     Communication line  131  may be any suitable connection means, including a T1 line, a T3 line, a fiber optic link, or any other type of data connection. The connections on line  131  may transmit analog voice signals or digital voice signals in pulse code modulated (PCM) format, Internet Protocol (IP) format, asynchronous transfer mode (ATM) format, or the like. According to an advantageous embodiment of the present invention, line  131  also provides an Internet Protocol (IP) connection that transfers data packets between the base stations of wireless network  100 , including BS  101 , BS  102  and BS  103 . Thus, line  131  comprises a local area network (LAN) that provides direct IP connections between base stations without using PDSN  150 . 
     MSC  140  is a switching device that provides services and coordination between the subscribers in a wireless network and external networks, such as the PSTN or Internet. MSC  140  is well known to those skilled in the art. In some embodiments of the present invention, communications line  131  may be several different data links where each data link couples one of BS  101 , BS  102 , or BS  103  to MSC  140 . 
     In the exemplary wireless network  100 , MS  111  is located in cell site  121  and is in communication with BS  101 . MS  113  is located in cell site  122  and is in communication with BS  102 . MS  114  is located in cell site  123  and is in communication with BS  103 . MS  112  is also located close to the edge of cell site  123  and is moving in the direction of cell site  123 , as indicated by the direction arrow proximate MS  112 . At some point, as MS  112  moves into cell site  123  and out of cell site  121 , a handoff will occur. 
     According to the principles of the present invention, the mobile stations in wireless network  100  are capable of executing streaming data applications (e.g., video phone). To facilitate these high-speed applications, the present invention provides low latency, low delay IP connections between base stations via line  131 , without sending data packets through PDSN  150 . The present invention comprises a system and method of messaging (based on the TIA-2001-C standard) between the base stations of a cdma2000 radio access network (RAN). 
     The present invention is based on the following assumptions:
         i) Both mobile stations are currently in cells that are under the control of a single mobile switching center (i.e., MSC  140 );   ii) An IP-based packet switched network (i.e., line  131 ) connects all base stations under the control of MSC  140 ;   iii) All billing for the MS-MS data call is done at MSC  140  and is based only on air time; and   iv) The MS-MS data call does not go dormant (i.e., both mobile stations stay on the traffic channels for the duration of the data call).       

     The proposed invention can be implemented using the well-known cdma2000 RAN architecture as described in the TIA-2001-C standard.  FIG. 1  shows this architecture and the entities that comprise wireless network  100 . In the example described below, two mobile stations (i.e., MS  111  and MS  113 ) are served by two separate base stations (i.e., BS  101  and BS  102 ) that are connected via an IP-based packet switched network (line  131 ) as defined in the TIA-2001-C standard. Both base stations are attached to MSC  140  via interfaces defined in the TIA-2001-C standard. MS  111  and MS  113  communicate with the base stations of wireless network  100  using messaging defined in the air interface standard TIA-2000-C, “cdma2000 Spread Spectrum Systems”, May 2002. 
       FIG. 2  is a message flow diagram illustrating the set up of a mobile station-to-mobile station (MS-MS) packet data call according to the principles of the present invention.  FIG. 2  shows line  131  as a network cloud in order to illustrate the operation of the present invention. Thereafter, the description below will frequently use the term “IP network 131” to refer to line  131 . 
     A source mobile station (i.e., MS  111 ) initiates an MS-MS packet data call by transmitting Origination message  201  with a service option (SO) data field that indicates an MS-MS packet data call. Message  201  also contains the number of the destination (or dialed) mobile station (MS  113 ). BS  101  sends CM Service Request message  202  to MSC  140  indicating the SO and the phone number of destination MS  113 . The acronym “CM” is attributed various meanings by persons of skill in the art of CDMA wireless communication networks. for example: Connection Management, Communication Management, and Configuration Management. BS  101  also begins to establish a traffic channel to MS  111  at this time. 
     MSC  140  authenticates both MS  111  and MS  113  to verify that both devices are permitted to access wireless network  100 . MS  140  also verifies that MS  111  and MS  113  are both authorized to use the MS-MS packet data call service. MSC  140  finds MS  113  in the service area and sends Paging Request message  203  to BS  102 , which is the last base station on which MS  113  registered. In response, BS  102  transmits Page message  204  to MS  113  with an indication (SO) of an incoming packet data call. MS  113  transmits Response message  205  indicating MS  113  will accept the packet data call. 
     Next, BS  102  sends Paging Response message  206  to MSC  140  indicating that MS  113  has responded to Page message  204 . BS  102  also indicates its own IP Network address in message  206 . Thus, MSC  140  is aware of the IP address of BS  102  on IP network  131 . MSC  140  sends Assignment Request message  207  to BS  102  to begin setting up the packet data call. BS  102  uses conventional air interface messaging to establish a traffic channel to MS  113 . When BS  102  finishes establishing the traffic channel to MS  113 , BS  102  sends Assignment Complete message (not shown) to MSC  140  to indicate that the packet data call connection has been established between BS  102  and MS  113 . 
     Meanwhile, MSC  140  also sends Assignment Request message  208  to BS  101  to notify BS  101  that destination MS  113  has been located and the packet data call is being set up. Message  208  contains the IP address of BS  102  on IP network  131 . Message  208  also contains the mobile identifier (IMSI or ESN) of MS  113 . If not already completed, BS  101  finishes establishing the traffic channel connection to MS  111  (message  209 ). When this traffic channel is finally set up, BS  101  sends an Assignment Complete message (not shown) to MSC  140  indicating that packet data call connection has been established between BS  101  and MS  111 . 
     Using the IP network address of BS  102  provided by MSC  140 , BS  101  establishes packet data bearer connection  210  to BS  102  using messaging as defined in the TIA-2001-C standard. Packet data bearer connection  210  carries data packet traffic associated with the MS-MS call between BS  101  and BS  102 . The control messages between BS  101  and BS  102  include the mobile identifier of MS  113 , so that BS  102  can associate packet data bearer connection  210  with the packet data call to MS  113 . All of the data packets that each of base stations  101  and  102  thereafter receive from one of mobile stations  111  and  113 , respectively, are sent over packet data bearer connection  210  to the other base station for subsequent transmission to the other mobile station. This establishes the RAN traffic link for the call. 
     Finally, MS  111  and MS  113  establish a link layer connection (indicated by dotted line  211 ). This may be, for example, a Point-to-Point Protocol (PPP) connection. Once the link layer is established, mobile stations  111  and  113  can exchange packet data with each other (e.g., for a video call). 
     In order to establish a connection between base stations  101  and  102  via IP network  131 , the present invention requires the following specific changes to conventional cdma2000 RAN messaging:
         i) a new MS-MS packet data service option is defined that allows a mobile station to initiate or receive MS-MS packet data calls and to alert wireless network  100  that the new call is a MS-MS packet data call;   ii) the IP network address of base station  102  must be added to Assignment Request message  208  and Paging Response message  206 , so that MSC  140  can forward the IP address of the destination base station (BS  102 ) to the source base station (BS  101 ). This is needed to establish the BS-BS data link through IP network  131 ; and   iii) for the inter-BS messaging that establishes the IP network link, a new indicator is added that informs the destination base station (i.e., BS  102 ) that the packet data bearer connection is for an MS-MS call.       

       FIG. 3  is a message flow diagram illustrating the handoff between base stations  101  and  103  of a mobile station-to-mobile station packet data call according to the principles of the present invention. In  FIG. 3 , it is assumed that the MS-MS packet data call between MS  111  and MS  113  via BS  101  and BS  102 , as described above in  FIG. 2 , is already in existence. At some point, MS  111  moves out of the coverage area of BS  101  and into the coverage area of BS  103 , as indicated by the dotted line. When this happens, MS  111  is handed off from BS  101  to BS  103 . In order to prevent the MS-MS packet data call from being dropped, BS  103  must assume the role that BS  101  previously performed. Thus, the MS-MS packet data call also must be handed off from BS  101  to BS  103 . 
     In this scenario, MSC  140  exchanges messages with each of BS  101 , BS  102  and BS  103  based on the TIA-2001-C standard. Similarly, BS  101 , BS  102  and BS  103  exchange messages with each other based on the TIA-2001-C standard. MS  111  exchanges messages with BS  101  and BS  103  based on the TIA-2000-C standard. 
     Initially, MS  111  sends pilot strength measurements to BS  101  in message  301  indicating that a handoff to the target cell covered by BS  103  is required. BS  101  responds by sending Handoff Required message  302  to MSC  140 . Message  302  includes the service option (SO) for the MS-MS packet data call, the call identifier that BS  101  and BS  102  are using for the MS-MS packet data call, the mobile identifiers for MS  111  and MS  113 , and the IP Network Address of BS  102 . MSC  140  determines that the target cell belongs to a base station (i.e., BS  103 ) under the control of MSC  140  and sends Handoff Request message  303  to BS  103 . 
     Handoff Request message  303  contains the same information MSC  140  received from BS  101  in Handoff Required message  302 . BS  103  prepares to receive MS  111  and sends Handoff Request Acknowledgment message  304  to MSC  140  indicating that BS  103  accepts the handoff request. At the same time, BS  103  begins to establish packet data bearer connection  305  with BS  102  using the IP address, mobile identifier, and call identifier that BS  103  received from MSC  140 . Once packet data bearer connection  305  is established, BS  102  transmits all data meant for MS  111  to both BS  101  and BS  103  and prepares to receive data from either one of BS  101  and BS  103 . 
     MSC  104  sends Handoff Command message  306  to BS  101 , indicating that BS  103  is ready to receive the handoff. BS  101  sends handoff direction message  307  (e.g., Extended Handoff Direction Message  307 , Universal Handoff Direction Message  307 , etc.) to MS  111  instructing MS  111  to begin sending and receiving information on the target cell covered by BS  103 . When MS  111  acquires BS  103 , MS  111  sends Handoff Completion Message  308  to BS  103 . The MS-MS packet data call has now been handed off from BS  101  to BS  103 . MS  111  and MS  113  continue to exchange data through packet data bearer connection  305  established between BS  102  and BS  103 . 
     Next, BS  103  sends Handoff Complete message  309  to MSC  140  after MS  111  is successfully acquired. MSC  140  sends Clear Command message  310  to BS  101  to indicate that MS  111  has been successfully acquired by BS  103 . BS  101  sends messaging to tear down packet data bearer connection  311  with BS  102 . BS  102  stops sending data destined for MS  111  to BS  101 . After this is completed, BS  101  sends a Clear Complete message (not shown) to MSC  140  to indicate that the MS-Ms packet data call has been cleared on BS  101 . 
     In order to handoff the connection between base stations via IP network  131 , the present invention requires the following specific changes to conventional cdma2000 RAN messaging:
         i) Handoff Required message  302  and Handoff Request message  303  (as defined in the TIA-2001-C standard) must include the new service option (SO) for MS-MS packet data calls, as well as the mobile identifier for MS  113 , and the IP Network Address of BS  102 ; and       

     ii) Changes to the BS-BS messaging are required, similar to those described for  FIG. 2 . 
       FIG. 4  is a message flow diagram illustrating the tear down of a mobile station-to-mobile station packet data call according to the principles of the present invention. In this scenario, MSC  140  exchanges messages with each of BS  101  and BS  102  based on the TIA-2001-C standard. Similarly, BS  101  and BS  102  exchange messages with each other based on the TIA-2001-C standard. MS  111  exchanges messages with BS  101  and BS  102  based on the TIA-2000-C standard. 
     At some point, one mobile station (MS  113  in this example) terminates the MS-MS packet data call. To do this, MS  113  sends Release Order message  401  to BS  102  to release the call. BS  102  transmits message  402  to acknowledge receipt of Release Order message  401  and drops the traffic channel to MS  113 . BS  102  notifies BS  101  on packet data bearer connection  403  of IP network  131  that connection  403  must be torn down. This also notifies BS  101  that BS  101  no longer needs to support the MS-MS packet data call. 
     BS  102  sends Clear Request message  404  to MSC  140  to request that the MS-MS packet data call be released. MSC  140  responds by transmitting Clear Command message  405  to BS  102  to release the MS-MS packet data call. BS  102  then sends Clear Complete message  406  to MSC  140  after all resources have been released. 
     After receiving the indication from BS  102  that packet data bearer connection  403  on IP network  131  is being torn down, BS  101  sends Clear Request message  407  to MSC  140  to request that the MS-MS packet data call be released. MSC  140  sends Clear Command message  408  to BS  102  to release the MS-MS packet data call. BS  101  transmits Release Order message  409  to MS  111  to release the traffic channel. MS  111  transmits message  410  to acknowledge the receipt of Release Order message  409 . At this point, the traffic s channel is released. BS  101  sends Clear Complete message  411  to MSC  140  after all resources are released. 
     The above-described tear down scenario may be accomplished using existing messaging as defined in the TIA-2001-C standard. It is noted that mobile station  111  and  113  may release the MS-MS packet data call simultaneously. MSC  140  keeps track of accounting for each mobile station. 
     The present invention enables direct MS-to-MS packet data calls. Utilizing direct BS-to-BS signaling on IP network  131  bypasses PDSN  150 , thereby allowing for faster call setup and handoff. 
     Although the present invention has been described in detail, those skilled in the art should understand that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.