Patent Publication Number: US-2006003772-A1

Title: Method and system for establishing a voice call for a hybrid mobile station operating in a data mode

Description:
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY  
      The present invention is related to that disclosed in U.S. Provisional Patent No. 60/584,937, filed Jul. 1, 2004, entitled “Method for Cross-Paging Between CDMA2000 and HRPD Systems.” U.S. Provisional Patent No. 60/584,937 is assigned to the assignee of the present application. The subject matter disclosed in U.S. Provisional Patent No. 60/584,937 is hereby incorporated by reference into the present disclosure as if fully set forth herein. The present application hereby claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent No. 60/584,937.  
    
    
     TECHNICAL FIELD OF THE INVENTION  
      The present invention relates generally to wireless networks and, more specifically, to a method and system for establishing a voice call for a hybrid mobile station operating in a data mode.  
     BACKGROUND OF THE INVENTION  
      The use of cellular telephones and wireless networks has become increasingly widespread. As the use of cellular telephones has increased, the number and quality of additional features made available with the cellular telephones has also increased. For example, some mobile stations (e.g., cellular telephones) are able to provide hybrid services by allowing users to participate in either voice calls or data sessions. In this way, a single, hybrid mobile station may provide the functionality of both a cell phone and a device that is operable to send and receive e-mail, text messages, or the like over a data network.  
      When the hybrid mobile station is in a data mode and a voice call for the mobile station is received at a corresponding mobile switching center (MSC), the MSC has to notify the mobile station of the incoming voice call so that the mobile station may switch over to a voice mode and the call may be established. Conventional techniques for establishing a call in this situation include the MSC sending a Page Request message to the base station handling the data session for the mobile station and also sending Page Request messages to any base stations that may be near the mobile station and are able to handle the call session. The MSC also notifies the call session base station not to page the mobile station because the mobile station is operating on a frequency different from the frequency used by the data session base station.  
      The call session base stations then wait for a possible Page Response from the mobile station. At the same time, the data session base station is paging the mobile station, which eventually responds to both the data session base station and one of the call session base stations. This call session base station receives the Page Response and proceeds to set up the voice call using a messaging standard, such as TIA-2001.  
      Thus, because the MSC does not know which call session base station the mobile station will select for the voice call, the MSC must transmit an excessive number of paging messages. In addition, conventional techniques for switching a mobile station from a data session to a call session require a relatively complex implementation of call session base stations because the base stations must have two paging algorithms: one for when the MSC actually wants the base station to send a Page Request over the air to look for a mobile station and one for the cross-paging case where the base station would not send a Page Request over the air, but would instead wait for the mobile station to respond to a Page Request sent from a data session base station.  
      Therefore, there is a need in the art for improved wireless networks that reduce the number of superfluous paging messages for switching mobile stations from data sessions to call sessions and that reduce the complexity of base stations. In particular, there is a need for a wireless network that is able to establish a voice call for a hybrid mobile station that is operating in a data mode without superfluous paging messages and without adding complexity to the base stations.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, a method and system for establishing a voice call for a hybrid mobile station that is operating in a data mode are provided that substantially eliminate or reduce disadvantages and problems associated with conventional methods and systems.  
      To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a method for establishing a voice call for a hybrid mobile station that is initially operating in a data mode. According to an advantageous embodiment of the present invention, the method comprises receiving an incoming voice call for the hybrid mobile station. A single Paging Request message is transmitted based on the incoming voice call. A Connection Management (CM) Service Request message is received. The voice call is established for the hybrid mobile station based on the CM Service Request.  
      According to one embodiment of the present invention, the single Paging Request message is transmitted to a data session base station that the hybrid mobile station is initially accessing in a data session.  
      According to another embodiment of the present invention, the data session base station is capable of operating in a High Rate Packet Data environment.  
      According to still another embodiment of the present invention, no messages are transmitted to a call session base station before the CM Service Request message is received.  
      According to yet another embodiment of the present invention, the CM Service Request message is received from a call session base station and the voice call is established for the hybrid mobile station through the call session base station.  
      According to a further embodiment of the present invention, the call session base station comprises a hybrid base station, the single Paging Request message is transmitted based on the incoming voice call to the hybrid base station, and the hybrid mobile station is initially accessing the hybrid base station in a data session.  
      According to a still further embodiment of the present invention, the call session base station is capable of operating in a CDMA2000 environment.  
      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 term “each” means every one of at least a subset of the identified items; 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; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some 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, 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 its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:  
       FIG. 1  illustrates an exemplary wireless network that is capable of establishing a voice call for a hybrid mobile station that is operating in a data mode according to the principles of the present invention;  
       FIG. 2  illustrates an exemplary hybrid mobile station that is capable of switching from a data mode to a voice mode in order to receive an incoming voice call according to the principles of the present invention; and  
       FIG. 3  is a flow diagram illustrating a voice call set-up operation according to one embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIGS. 1 through 3 , 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 network.  
       FIG. 1  illustrates an exemplary wireless network  100  that is capable of establishing a voice call for a hybrid mobile station that is operating in a data mode 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, for example, the IS-2000 standard (i.e., CDMA2000). In an advantageous embodiment of the present invention, mobile stations  111 - 114  are capable of receiving data traffic and/or voice traffic on two or more CDMA channels simultaneously. Mobile stations  111 - 114  may be any suitable wireless devices (e.g., conventional cell phones, PCS handsets, personal digital assistant (PDA) handsets, portable computers, telemetry devices) that are capable of communicating with base stations  101 - 103  via wireless links.  
      The present invention is not limited to mobile devices. The present invention also encompasses other types of wireless access terminals, including fixed wireless terminals. 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., a machine monitor with wireless capability).  
      Dotted lines show the approximate boundaries of 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, each of cell sites  121 - 123  is comprised of a plurality of sectors, 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 may 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, each of BS  101   a - b,  BS  102  and BS  103  comprises a base station controller (BSC) and one or more base transceiver subsystem(s) (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 subsystems 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   a - b,  BS  102  and BS  103 , respectively.  
      BS  101   a - b,  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   a - b,  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 MSC  140 , or as a stand-alone device that communicates with PDSN  150 , as shown in  FIG. 1 . Line  131  also provides the connection path for control signals transmitted between MSC  140  and BS  101   a - b,  BS  102  and BS  103  that establish connections for voice and data circuits between MSC  140  and BS  101   a - b,  BS  102  and BS  103 .  
      Communication line  131  may be any suitable connection means, including a T 1  line, a T 3  line, a fiber optic link, a network packet data backbone connection, or any other type of data connection. Line  131  links each vocoder in the BSC with switch elements in MSC  140 . 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.  
      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   a - b,  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   a  or BS  101   b . 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 hand-off will occur.  
      As described in more detail below in connection with  FIG. 2 , at least one of mobile stations  111 - 114  may comprise a hybrid mobile station that is capable of communicating in a voice mode and in a data mode. In addition, one or more of the base stations  101 - 103  may be capable of communicating with mobile stations  111 - 114  in either the voice mode or the data mode. These base stations may be referred to as hybrid base stations.  
      For a particular alternative, one or more of the base stations, such as base station  101   a,  may be capable of communicating with mobile stations  111 - 114  only in a voice mode, while one or more other base stations, such as base station  101   b , may be capable of communicating with mobile stations  111 - 114  only in a data mode. For this embodiment, base station  101   a  may be referred to as a call session base station, while base station  101   b  may be referred to as a data session base station. It will be understood that any suitable combination of base stations may be implemented in wireless network  100  without departing from the scope of the present invention.  
      For the following description, base station  101   a  is a call session base station that operates in a CDMA2000 environment, such as 3G-1x, and base station  101   b  is a data session base station that operates in a High Rate Packet Data environment, such as 1xEV-DO. It will be understood that the description also applies to a hybrid base station that includes the functionality of both base stations  101   a  and  101   b.  In addition, mobile station  111  is assumed to be a hybrid mobile station.  
      In operation, according to an advantageous embodiment of the present invention, mobile station  111  is operating in a data mode and is communicating with data session base station  101   b.  MSC  140  receives an incoming voice call for mobile station  111 . MSC  140  sends only one Paging Request in response to receiving the incoming voice call. The Paging Request is sent by MSC  140  to data session base station  101   b.  In response to the Paging Request, data session base station  101   b  pages mobile station  111 , which acknowledges the page to data session base station  101   b  and switches from data mode to voice mode. Mobile station  111  also sends an Origination Message to call session base station  101   a,  which prompts call session base station  101   a  to set up the voice call previously received by MSC  140 .  
      In this way, MSC  140  only has to send out one Paging Request, which eliminates superfluous paging messages. In addition, call session base station  101   a  and any hybrid base station may be implemented without needless additional complexity because these base stations may operate normally in these situations.  
       FIG. 2  illustrates an exemplary hybrid mobile station  111  that is capable of switching from a data mode to a voice mode in order to receive an incoming voice call according to the principles of the present invention. Mobile stations  112 - 114  may be identical to mobile station  111  and are not described separately. Wireless hybrid mobile station  111  comprises antenna  205 , radio frequency (RF) transceiver  210 , transmit (TX) processing circuitry  215 , microphone  220 , and receive (RX) processing circuitry  225 . Hybrid mobile station  111  also comprises speaker  230 , main processor  240 , input/output (I/O) interface (IF)  245 , keypad  250 , display  255 , and memory  260 . Memory  260  further comprises basic operating system (OS) program  261  and control channel (CC) message controller application  262 .  
      Radio frequency (RF) transceiver  210  receives from antenna  205  an incoming RF signal transmitted by a base station of wireless network  100 . Radio frequency (RF) transceiver  210  down-converts the incoming RF signal to produce an intermediate frequency (IF) or a baseband signal. The IF or baseband signal is sent to receiver (RX) processing circuitry  225  that produces a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. Receiver (RX) processing circuitry  225  transmits the processed baseband signal to speaker  230  (i.e., voice data) or to main processor  240  for further processing (e.g., web browsing).  
      Transmitter (TX) processing circuitry  215  receives analog or digital voice data from microphone  220  or other outgoing baseband data (e.g., web data, e-mail, interactive video game data) from main processor  240 . Transmitter (TX) processing circuitry  215  encodes, multiplexes, and/or digitizes the outgoing baseband data to produce a processed baseband or IF signal. Radio frequency (RF) transceiver  210  receives the outgoing processed baseband or IF signal from transmitter (TX) processing circuitry  215 . Radio frequency (RF) transceiver  210  up-converts the baseband or IF signal to a radio frequency (RF) signal that is transmitted via antenna  205 .  
      In an advantageous embodiment of the present invention, main processor  240  is a microprocessor or microcontroller. Memory  260  is coupled to main processor  240 . According to an advantageous embodiment of the present invention, part of memory  260  comprises a random access memory (RAM) and another part of memory  260  comprises a Flash memory, which acts as a read-only memory (ROM).  
      Main processor  240  executes basic operating system (OS) program  261  stored in memory  260  in order to control the overall operation of wireless hybrid mobile station  111 . In one such operation, main processor  240  controls the reception of forward channel signals and the transmission of reverse channel signals by radio frequency (RF) transceiver  210 , receiver (RX) processing circuitry  225 , and transmitter (TX) processing circuitry  215 , in accordance with well-known principles.  
      Main processor  240  also executes control channel (CC) message controller application  262 . Control channel message controller application  262  is responsible for communicating with a base station in the common control channels and for setting up a call session while switching from a data mode to a voice mode according to the principles of the present invention. Thus, control channel message controller application  262  is capable of sending, in the voice mode, an Origination Message to call session base station  101   a  in response to a Paging Request received from data session base station  101   b  when mobile station  111  is in the data mode. The Origination Message results in the establishment of the voice call.  
      In an exemplary embodiment of the present invention, control channel message controller application  262  may be implemented as one of the functions of basic operating system program  261 . However, for the purposes of clarity and simplicity in explaining the operation of the present invention, control channel message controller application  262  is shown in  FIG. 2  as a separate entity from basic operating system program  261 .  
      Main processor  240  is capable of executing other processes and programs resident in memory  260 . Main processor  240  can move data into or out of memory  260 , as required by an executing process. Main processor  240  is also coupled to I/O interface  245 . I/O interface  245  provides hybrid mobile station  111  with the ability to connect to other devices such as laptop computers and handheld computers. I/O interface  245  is the communication path between these accessories and main controller  240 .  
      Main processor  240  is also coupled to keypad  250  and display unit  255 . The operator of hybrid mobile station  111  uses keypad  250  to enter data into hybrid mobile station  111 . Display  255  may be a liquid crystal display capable of rendering text and/or at least limited graphics from web sites. Alternate embodiments may use other types of displays.  
       FIG. 3  is a flow diagram  300  illustrating a voice call set-up operation according to one embodiment of the present invention. For the following description, it is assumed that base station (BS)  101   a  is a call session base station and base station  101   b  is a data session base station. It is also assumed that hybrid mobile station (MS)  111  is initially accessing data session base station  101   b  in a data session and MSC  140  has received an incoming voice call for MS  111 . It will be understood that the description also applies to a hybrid base station that includes the functionality of both base stations  101   a  and  101   b.    
      In response to the incoming voice call, MSC  140  initiates the set-up of the voice call for MS  111  by transmitting a Paging Request message  301  to data session BS  101   b.  In response to Paging Request message  301 , data session BS  101   b  transmits a General Page message  302  to MS  111  that notifies MS  111  of the incoming voice call. For one embodiment, General Page message  302  may comprise a CDMA2000 General Page message included in a 3 G-1 x services packet. In addition, General Page message  302  may or may not comprise information identifying the party that originally initiated the voice call, such as a telephone number.  
      In response to General Page message  302 , MS  111  transmits an acknowledgement in the form of Acknowledgment (Ack) General Page message  303  to data session BS  101   b  and also transmits an Origination Message  304  to call session BS  101   a.  As previously described, data session BS  101   b  and call session BS  101   a  may or may not be the same base station. In addition, MS  111  may choose the call session BS to which Origination Message  304  is to be transmitted based on which call session BS is able to provide the best service for MS  111 .  
      If General Page message  302  comprises information identifying the initiating party, Origination Message  304  may comprise that identifying information. Origination Message  304  may also comprise a preferred voice service option that is able to notify call session BS  101   a  that a voice call is being set up.  
      In response to receiving Origination Message  304  from MS  111 , call session BS  101   a  transmits a Connection Management (CM) Service Request message  305  to MSC  140 . If Origination Message  304  comprises information identifying the initiating party, CM Service Request message  305  may comprise that identifying information. If Origination Message  304  does not comprise the identifying information, CM Service Request message  305  may comprise a Special Service Call Indicator value that is able to indicate to MSC  140  that CM Service Request message  305  corresponds to a mobile-originated voice call without identifying information for the initiating party.  
      Based on CM Service Request message  305 , MSC  140  recognizes that MS  111  is responding to the incoming voice call. At this point, MS  111 , call session BS  101   a,  and MSC  140  may exchange additional messages  306  related to establishing the voice call. For one embodiment, the additional messages  306  may be in a TIA-2001 messaging format.  
      Although the present invention has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.