Abstract:
A method and apparatus for providing bifurcated voice and signaling traffic over a cable telephony architecture by segregating signaling traffic and voice traffic and transmitting the respective traffic over two different mediums to a controller to establish a phone call.

Description:
TECHNICAL FIELD 
   The invention relates to the field of communications systems and, more particularly, to a method and apparatus for providing bifurcated signaling and bearer traffic over a cable telephony network. 
   DESCRIPTION OF THE BACKGROUND ART 
   A cable telephony network allows voice to be transported over the Public Switch Telephone Network (PSTN) or using a Packetized Voice mechanism such as Voice over Internet Protocol (VoIP) for voice to be transported over an Internet Protocol (IP) network. 
   Cable companies have an installed base of equipment, which is primarily directed to the transport of video not voice and data. To provide voice over their infrastructure, cable companies must adapt their networks to accept voice at a great economical expense. Compounding the problem is that the transport of voice is very bandwidth intensive due to, for example, transport overhead. For example, to transport a 64 kilobit per second voice call, in certain circumstances, may require more than 140 kilobits per second of IP traffic. Also, the Cable companies require a Quality of Service (QoS) enabled network and a high processing capacity gateway to support VoIP telephony. 
   Current Host Digital Terminal (HDT) based voice over cable telephony architectures do not have the required end to end bandwidth to support traditional voice processing without the potential of producing signal degradation. Also, existing Packet Cable based voice over cable telephony architectures do not have the required end to end bandwidth to support traditional voice processing without the potential of producing high network delays. Additionally, the transport of voice traffic and signaling information lead to bottlenecks within the infrastructure of the cable telephony network. 
   SUMMARY OF THE INVENTION 
   The invention comprises a system and method for providing bifurcated voice and signaling traffic utilizing a suggested hybrid fiber coaxial (HFC)/wireless access architecture. The invention advantageously provides efficient, end-to-end communication by reducing bottlenecks within the infrastructure of the existing cable network. Additionally, signal degradation and delays are reduced. 
   Specifically, a method, comprising the steps of: segregating signaling traffic and related voice traffic, the signaling traffic including information useful in establishing a communications link for transporting the voice traffic between a calling party and a called party; transmitting the signaling traffic via the first network to a controller, the controller utilizing the signaling traffic to establish the communications link for the voice traffic; and transmitting the voice traffic via the communications link established by the controller, the voice traffic and the signaling traffic being carried by different communications channels. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts a high level block diagram of a communications system including the present invention; 
       FIG. 2  depicts a high level block diagram of a Media Terminal Adapter-Cellular Transceiver (MTA-CT) controller suitable for use in the communications system of  FIG. 1 ; 
       FIG. 3  depicts a flow diagram of a method for providing bifurcated voice traffic and signaling information; 
       FIG. 4A  depicts a logical signaling path in a switch according to the present invention; 
       FIG. 4B  depicts an actual signaling path in a switch according to the invention; 
       FIG. 5  depicts a call flow diagram of an on network to off network call; and 
       FIG. 6  depicts a call flow diagram of an off network to on network call. 
   

   To facilitate understanding, identical reference numerals have been-used, where possible, to designate identical elements that are common to the figures. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The invention will be described within the context of three subscribers (A, B and C) communicating via respective telephony technologies. It should be noted that the present invention is compatible with different telephony technologies (i.e. Voice over Internet Protocol VoIP, Voice over Digital Subscriber Loop (VoDSL), Fiber to the Home (FTTH) and the like). The benefits of the invention can be gained even if a respective subscriber uses an alternate technology. 
   It should be appreciated by those skilled in the art that the voice application presented here can be replaced with any multi-media application. 
     FIG. 1  depicts a high level block diagram of a communications system including the present invention. Specifically, the system  100  of  FIG. 1  comprises at subscriber A a first computer terminal  102  and a first telephone device  104 , both coupled to a first multi-media terminal adapter and cellular transceiver (MTA-CT)  106 . First MTA-CT comprises a MTA  106 A, a cellular transceiver  106 B and a MTA-CT controller  106 C. Coupled to first MTA-CT  106  is a first cable modem  108 . A first fiber coaxial coupler  112  is connected to the first cable modem  108  via a transmission medium  110 . 
   It should be appreciated by those skilled in the art that first MTA-CT  106  may be integrated into first cable modem  108 . 
   At a cable Headend A or a Hub A, a first optical transceiver  116  is coupled to first fiber node  118 . The first fiber node  118  is connected to first fiber coaxial coupler  112  via transmission medium  114 . Second transmission medium  114  comprises, for example, a fiber optic cable. First optical transceiver  116  is coupled to a video transport network  134 . The video transport network  134  supports the distribution of video and audio signals such as movies to headend offices and to subscribers. 
   First optical transceiver  116  is also coupled to a first Cable Modem Termination System (CMTS)  120 . First CMTS  120 , is coupled to a first router  124  which is, in turn, coupled to an internet protocol (IP) network  132 . IP network  132  provides interchange of transport data to a second cable headend or Hub. It will be appreciated by those skilled in the art that IP network  132  can be replaced with a data network adhering to a non-IP protocol. 
   First CMTS  120  is also coupled to a first Circuit Packet Bearer Traffic Gateway (CPBTG)  122 . First CPBTG  122 ′ is coupled to a first switch  128 , illustratively a class 5 Wireless switch which is also known as a Mobile Switching Center (MSC), via a T1 trunk  129 . T1 trunk  129  comprises, illustratively, twenty four Digital Signal Level Zero (DS0) channels. 
   It should be appreciated by those skilled in the art that first switch  128  may be a voice switch with a wireless interface and that CPBTG  122  may be integrated into the switch. 
   First switch  128  is coupled to a first base station system  126  via a second T1 trunk. First switch  128  includes a control module or controller  128 G, a wireless global switch module  128 B which allows a wireless switch module  128 A to communicate with first BSS  126 , a Visitor Location Register (VLR)  128 F for storing the Equipment Identifier Numbers (EIN)  128 E of cellular units from outside the serving area making calls within a local calling area; a Home Location Register (HLR)  128 C database which, stores the EINs of cellular phones from the local serving area; Equipment Identifier Register (EIR)  128 E database for storing EINs of phones allowed to make calls; and Authentication Center (AuC)  128 D database performs mathematical computations to verify authenticity of cell phone identity. 
   It will be appreciated by those skilled in the art that VLR  128 F, HLR  128 C, EIR  128 E, and AuC  128 D databases may be stored externally from first switch  128 . 
   First base station system  126  is coupled to first MTA-CT  106  via a radio frequency (RF) link. First switch  128  is also coupled to the Public Switch Telephone Network (PSTN)  130 . PSTIN  130  supports communication between first switch  128  and a second switch  138  at central office B (which is local to subscriber B). Included in PSTN  130  is a gateway switch  131  for routing calls between local serving switches, for example, first switch  128  and second switch  138 . A third telephone, at subscriber C, is coupled to gateway switch  131 . 
   Second switch  138  is coupled to a second BSS  140  via a third T1 trunk  139 . Second BSS  140  is coupled to a second MTA-CT  160 , located at subscriber B, via a second radio frequency link. Second MTA-CT  160  is coupled to a second telephone  162  and a second computer  164 . Second MTA-CT  160  is also coupled to cable modem  158 . A second fiber coaxial coupler  154  is coupled to second cable modem  158  via transmission medium  156  for example, a coaxial cable. 
   At cable Headend B or Hub B a second optical transceiver  150  receives video from video transport network  134 . A second fiber node  148  is coupled to second optical transceiver  150 . Second fiber node  148  is coupled to second fiber coaxial coupler  154  via a transmission medium  152  such as coaxial cable. Second optical transceiver  150  is also coupled to a second CMTS  144 . CMTS is coupled to a second router  146  which receives and transmits data information to and from the IP network  132 . Second CMTS  144  is also coupled to a second CPBTG  142 . Second CPBTG  142  is also coupled to second switch  138  via a fourth trunk  141 . 
   In the case of a voice communication from subscriber A to subscriber B, the first MTA-CT  106  detects an “off hook” condition from first telephone  104  and communicates with first BSS  126  via a radio frequency link. First BSS  126  establishes a signaling path, with first switch  128  via a DS0 channel on T1 trunk  127 . Signaling between first BSS  126  and first switch  128  can be done using, for example, Signaling System 7 (SS7) protocol. 
   Once a signaling path is established between first BSS  126  and first switch  128 , first BSS  126  notifies first MTA-CT  106  that the signaling path is established. First MTA-CT  106 , responsively communicates signaling messages to first switch  128 . Once signaling messages are established and the called party picks up the second telephone  162 , the voice traffic flows from telephone  104  to first MTA-CT  106  in digitized form to first cable modem  108 . The voice signal is then communicated to first CMTS  120 . First cable modem  108  and first CMTS  120  utilize Data Over Cable System Interface Specification (DOCSIS) protocol to communicate data packet data between the respective devices. The bandwidth DOCSIS provides primarily depends upon channel radio frequency (RF) bandwidth, symbol rate, and modulation techniques used. 
   It will be appreciated by those skilled in the art that first MTA-CT  106  will transmit voice in compressed form via first cable modem  108  based upon the wireless technology used. Since first switch  128  is a wireless switch, wireless voice compression techniques can be utilized between first MTA-CT  106  and first switch  128 . In case local power is lost to first MTA-CT  106 , the voice traffic is transmitted over the wireless network. 
   Further data compression can be achieved via the use of DOCSIS and Internet Protocol (IP)/User Datagram Protocol (UDP)/Real-time Transport Protocol (RTP) header compression. 
   First CMTS  120  then communicates voice signals to first CPBTG  122  where the voice signal is depacketized and communicated to first switch  128  in circuit form rather than packet form. Specifically, CPBTG  122  converts voice path setup and packet to circuit conversions and vice versa as opposed to present devices which only perform Network Based Call Signaling (NCS) and voice path-setup. Illustratively, a product such as the Packet Star Access Concentrator model 1250(PSAX 1250) manufactured by Lucent Technologies, Inc of Murray Hill, N.J. could be used with minor modifications as CPBTG  122 . 
   First switch  128  then communicates the voice traffic to PSTN  130  where It is then communicated to second switch  138 . Based on a called party number, second switch  138  determines that a call is going to a cable modem customer, and initiates communication with second BSS  140  where a signaling path is established between second switch  138  and second BSS  140 . BSS  140 , in turn, initiates a signaling path with second MTA-CT  160 . Second MTA-CT  160  receives the signaling information and detects a ringing condition from subscriber A. In turn, MTA-CT  160  rings second telephone  162 . 
   Once subscriber B picks up second telephone  162 , this signaling information is conveyed back to first MTA-CT  106 , and a voice path is established between first MTA-CT  106  and second MTA-CT  160  whereby voice traffic is communicated between first MTA-CT  106  to second MTA-CT  160  via the route first MTA-CT  106  to first cable modem  108  to first CMTS  120  to first CPBTG  122  to first switch  128  over public switch telephone network  130  to second switch  138  to second CPBTG  142  to second CMTS  144  to second cable modem  158  to second MTA-CT  160 . 
     FIG. 2  depicts a MTA-CT controller  106 C suitable for use in the communications system  100  of  FIG. 1 . Specifically, the exemplary MTA-CT controller  106 C of  FIG. 2  comprises a processor  106 -C 4  as well as memory  106 -C 2  for storing various control programs such as program  106 -C 5 . The processor  106 -C cooperates with conventional support circuitry  106 -C 3  such as power supplies, clock circuits, cache memory and the like as well as circuits that assist in executing the software routines stored in the memory  106 -C 2 . As such, it is contemplated that some of the process steps discussed herein as software processes may be implemented within hardware, for example, as circuitry that cooperates with the processor  106 -C to perform various steps. The MTA-CT controller  106 -C also contains input/output circuitry  106 -C 1  that forms an interface between the various functional elements communicating with the MTA-CT controller  106 C. For example, in an embodiment of  FIG. 1 , the MTA-CT  106  communicates with a first BSS  126  via a signal path S 1 , a computer  102  via signal path S 2 , a telephone  104  via signal path S 3  and a first cable modem  108  via signal path S 4 . 
   Although the MTA-CT controller  106 C is depicted as a general purpose computer that is programmed to perform various MTA-CT controller functions in accordance with the present invention, the invention can be implemented in hardware as, for example, an application specific integrated circuit (ASIC). As such, the process steps described herein are intended to be broadly interpreted as being equivalently performed by software, hardware or a combination thereof. 
   The MTA-CT controller  106 C of the present invention communicates with a first cable modem  108  such as those being used by current cable telephony customers to provide voice and data over a network. 
     FIG. 3  comprises a flow diagram of a method for providing bifurcated voice traffic and signaling information. Specifically, the method  300  of  FIG. 3  utilizes MTA-CT  106  to provide bifurcated voice traffic and signaling information. 
   The method  300  of  FIG. 3  is entered at step  302  and proceeds to step  304 , where an “off hook” condition is detected by MTA  106 A, and a dial tone is generated by MTA  106 A. The method  300  then proceeds to step  306 . 
   At step  306 , a wireless communications link is established with first BSS  126 . First BSS  126  serves as a link for the CT  106 B to communicate and connect a call to a switch. 
   In response to CT  106 B establishing a communication link with first BSS  126 , first BSS  126 , in turn, establishes a signaling link with first switch  128  at step  308 . During the process of establishing a link with first switch  128 , the CT  106 B is going through an equipment authentication phase. During the equipment authentication phase, the CT&#39;s  106 B authenticity is determined in a conventional manner. 
   At step  310 , first switch establishes a communications link with second switch  138  via PSTN  130 . At step  312 , second switch  138 , in response, causes subscriber B&#39;s second telephone  162  to ring. The method  300  then proceeds to step  314 . 
   At step  314  a voice path is established between subscriber A and Subscriber B. At step  316 , in response to a voice path being established at step  314 , voice traffic is communicated between subscriber A and subscriber B via first MTA  106 , first cable modem  108 , first CMTS  120 , first CPBTG  122 , first switch  128 , PSTN  130 , second switch  138 , second CPTG  142 , second CMTS  144 , second cable modem  158 , and second MTA-CT  160 . 
   At step  318 , the method  300  then ends. 
     FIG. 4A  depicts the logical signaling path in the switch according to the present invention. Within the first switch  128  is a control module  128 G coupled respectively to WSM 1    128 A 1 , WSM 2    128 B 2  and WGSM  128 B. WGSM  128 B is coupled to WSM 1    128 A 1  and WSM 2    128 A 2  via DS0 time slots passing through control module  128 G. WSM 1    128 A 1  is coupled, respectively, to first CPBTG  122  and second CPBTG  142  via T1 trunks. WSM 2    128 A 2  is coupled to first CPBTG  122  and second CPBTG  142  respectively via T1 trunks. First CPBTG  122  is coupled to first CMTS  120  which is in turn coupled to first MTA-CT  106  via a hybrid coax connection. Second CPBTG  142  is coupled to second CMTS  144 . Second CMTS  144  is in turn coupled to MTA-CT  160  via a hybrid fiber coaxial connection. WGSM  128 B is coupled respectively to BSS  126  and BSS  140  via DS0 channels on a T1 trunk. BSS  126  is coupled to MTA-CT  106  and BSS  140  is coupled to MTA-CT  160  both via radio frequency links. Signaling System 7 (SS7) can be used to provide signaling between first switch  128  and first BSS  126 . 
   When an “off hook” condition is detected for a subscriber, MTA-CT  106  communicates the “off hook” condition to the first BSS  126  via the radio frequency link. BSS  126 , in turn, communicates the “off hook” condition to WGSM  128 B. WGSM  128 B is a wireless switch module with the global responsibility of distributing signaling messages between base station systems and wireless switch modules. All signaling from base station systems ultimately terminate on the wireless global switch module. Up to four maximum signaling links per base signaling station can be engineered. Since T1 trunks and call handling responsibilities between the switch and a given base station system are distributed across multiple wireless switch modules, it is necessary to have a signaling message switch WGSM  128 B. The paths between WGSM 1    128 A 1  and WSM  128 A 2  and WGSM  128 B are known as message delivery paths (MD-PH) and are on dedicated DS0 time slots for the purpose of delivering signaling messages to the correct WSM. Each wireless switch module has one MD-PH to the wireless global switch module. For example, if a switch is equipped with 10 WSMs, then the WGSM would have 10 MD-PHs, one for each of the WSMs. The maximum number of WGSMs that can be equipped in a switch is one. Additionally, the WGSM  128 B hides internal switch distributed processor/processing architectural details from base station systems, thus providing the appearance to all base station systems that a switch is logically one entity. 
   Once a signaling path has been established and the calling party has been alerted that the called party has picked up the telephone, a voice path is established from first MTA-CT  106  to second MTA-CT  160 . 
   WGSM provides a capability for any wireless switch module to send messages to any base station system, and vice versa, even if there are no physical facilities between a given base station system and wireless switch module. 
     FIG. 4B  depicts an actual signal path in a switch according to the invention. The only difference pictorially between  FIG. 4A  and  FIG. 4B  is that rather than the signal path going from BSS  126  to WGSM  128 B and from BSS  140  to WGSM  128 B, the path goes from BSS  126  to WSM 1    128 A 1  through the control module  128 G to WGSM  128 B. The signal path also goes from BSS  126  to WSM 2    128 A 2  to control module  128 G to WGSM  128 B. The signal path also goes from BSS  140  to WSM 1    128 A 1  and WSM 2    128 A 2  through control module  128 G to WGSM  128 B. 
   When the base station system initiates communication with a wireless switch module, the wireless switch module communicates with the wireless global switch module via the MD-PH. The wireless global switch module then decides which wireless switch module is to communicate with the base station system. The base station system will not know if the wireless switch module it initiated communication with is not the same wireless switch module processing the signaling messages between the base station system and the wireless system module. The wireless global switch module hides internal switch functions from the base station system, thus providing the appearance to all base station systems that the switch is logically one entity. 
     FIG. 5  depicts a call flow diagram useful in understanding an embodiment of the present invention. Specifically,  FIG. 5  depicts an on network to off network call flow diagram or process  500 . 
   Party A initiates the call flow at step  501  by picking up first telephone  104 . At step  502 , the MTA- 106 A portion of the MTA-CT  106  detects the off hook condition and generates a dial tone. The user then enters the phone number of the called party. 
   At step  503 , the cellular transceiver  106 B portion of the MTA-CT  106  communicates a channel request message over a common access channel to first BSS  126 . The purpose of the channel request message is to alert the first BSS  126  that a call is being made. The process  500  proceeds to step  504 . 
   At step  504 , first BSS  126  dedicates a signaling channel assignment for MTA-CT  106 . When first BSS  126  receives the channel request message from MTA-CT  106 , it allocates a stand-alone dedicated control channel (SDCCH) and forwards this channel assignment information to the cellular transceiver  106 B portion of MTA-CT  106  over the access grant channel (AGCH). It is over the SDCCH that the cellular transceiver  106 B portion of first MTA-CT  106  will communicate with first BSS  126  and first switch  128  until a traffic channel is assigned. 
   At step  505 , the CT  106 B portion of first MTA-CT  106 B communicates a service request message to first BSS  126 . The service request message is communicated over the SDCCH. Included in this message is a cellular transceiver temporary cellular identification number (TMSI) and location area identification (LAI). This message also establishes a layer 2 signaling connection between the cellular transceiver  106 B of MTA-CT  106  and first BSS  126 . Every time a call is made, a TMSI is assigned to CT  106 B. The location identifier just identifies the area where the call is made from. The process proceeds to step  506 . 
   At step  506 , the first BSS  126  communicates a service request message to first switch  128 . This message also causes the start-up of a Signaling Connection Control Part (SCCP) if cellular transceiver  106 B does not have any other call instances active. At step  507 , first switch  128  informs its Home Location Register (HLR)  128 C that a particular cellular transceiver is requesting service. 
   Process  500  enters the authentication and call setup phase of the call process. At step  508  the HLR  128 C requests authentication parameters from an Authentication Center (AUC)  128 D. Three authentication parameters are used by the HLR  128 C in order to authenticate a given cellular transceiver an authentication Random Number (RAND), an Authentication Side Response (SRES) and a Cipher Key (Kc). The visitor location register VLR  128 F is capable of requesting and storing up to five authentication parameters per register as described from the AUC  128 D, via the cellular subscriber&#39;s HLR  128 C. The HLR  128 C forwards this request to the Authentication Center  128 D. 
   In response to the HLR&#39;s  128 C request for authentication parameters the AUC  128 D, at step  509 , communicates authentication parameters to the HLR  128 C. The AUC  128 D, using the International Mobile Subscriber Identity (IMSI) which identifies cellular transceiver&#39;s  106 B home country and service provider, extracts the subscriber&#39;s authentication key (Ki). The AUC  128 D then generates a random number, applies the Ki and RAND to authentication algorithm (A 3 ) and the cipher key generates an algorithm (A 8 ) to produce an authentication signed response and a cipher key (Kc). The AUC  128 D then returns to the HLR  128 C authentication parameters: RAND, SRES and Kc. 
   At step  510 , the HLR  128 C communicates a request for authentication to first switch  128 . This is done for security purposes. The HLR is trying to verify if the call is a legitimate call and that cellular transceiver&#39;s  106 B identity hasn&#39;t been stolen. Included in the message is a random number. At step  511 , first switch  128  communicates a request for authentication to cellular transceiver  106 B of first MTA-CT  106 . First switch  128  forwards the authentication request message to the cellular transceiver  106 B. The cellular transceiver  106 B portion of first MTA-CT  106  reads this authentication key (Ki) from the Subscriber Identity Module (SIM), applies the random number (RAND) and Ki to both its authentication algorithm (A 3 ) and cipher key generation algorithm (A 8 ) to produce an authentication signed response (SRES) and cipher key (Kc). The cellular transceiver  106 B portion of first MTA-CT  106  saves Kc for later and will use Kc when it receives a command to cipher the channel. At step  512 , the cellular transceiver  106 B portion of first MTA-CT  106  transmits an authentication response to first switch  128 . The process  500  then proceeds to step  513 . 
   At step  513 , the first switch  128  forwards the SRES message to the HLR  128 C. The HLR  128 C compares the SRES message returned from the cellular transceiver  106 B with the expected SRES message received earlier from the AUC  128 D. If the values contained within the SRES messages are equal, the cellular transceiver  106 B passes authentication. If unequal, appropriate actions will be taken which could result in the subscriber identity module (SIM) being disabled. For purposes of simplicity, it&#39;s assumed that cellular  106 B passed authentication. 
   The process  500  enters the ciphering stage where at step  514 , HLR  128 C communicates a set ciphering message to first switch  128 . The HLR  128 C requests the first switch  128  to cipher the radio channel. Included in the message is the cipher key (Kc) which was made available earlier during authentication. At step  515 , the first switch  128  communicates an end cipher command to the first BSS  126 . 
   In response to receiving the end cipher command, the first BSS, at step  516 , retrieves the cipher key Kc from the message and then transmits a request to the first cellular transceiver  106 B requesting it to begin ciphering a channel. At step  517 , the first cellular transceiver  106 B transmits a cipher mode complete to first BSS  126 . The first cellular transceiver  106 B uses the cipher key generated previously when it was authenticated to cipher the up link channel, and transmits a confirmation over the cipher channel to first BSS  126 . 
   In response to receiving the cipher mode complete message, first BSS  126 , at step  518 , uses the cipher key it previously received from the first switch  128  to cipher the downlink channel. First BSS  126  then sends a cipher complete message to first switch  128 . 
   Process  500  now enters the equipment validation phase of the call process. The purpose of the equipment validation phase is to read the cellular equipment serial number from cellular transceiver  106 B and check it against the equipment identity register (EIR) to determine if special action should be taken, such as denying service. Equipment validation is optional and is controlled by the service provider. 
   At this point, the cellular transceiver  106 B has been authenticated and the radio channel is being encrypted. Two events will now occur in parallel. First, the first switch  128  interrogates the first cellular transceiver  106 B for its equipment number and checks the equipment number against information in equipment identity register. Second, the first cellular transceiver  106 B, after receiving the cipher command, forwards a call set up request to the first switch  128 . Equipment validation is performed after the ciphering phase and in parallel with call set up. Thus, in this scenario the equipment validation phase is shown to occur before the cellular transceiver  106 B forwards a call set up request message to first switch  128 . 
   At step  519 , the first switch  128  transmits an international mobile equipment identity (IMEI) or electronic serial number (ESN) request. Cellular transceiver  106 B is required to respond with its IMEI or ESN number. 
   In response to a request for an IMEI or ESN number, cellular transceiver  106 B, at step  520 , reads this equipment serial number or IMEI number and returns this value to first switch  128 . At step  521 , the first switch  128  communicates a checked IMEI/ESN message to equipment identity register (EIR)  128 E. The EIR  128 E checks the validity of the IMEI/ESN. The EIR  128 E will first check to see if the IMEI/ESN value is within a valid range. If so, it then checks to see if the IMEI/ESN is on a suspect or known list of invalid equipment. 
   At step  522 , the EIR  128 E communicates the IMEI/ESN results to first switch  128 . If the results are negative, the first switch  128  might abort the call or possibly let the call continue and will inform the network service provider of the event. For purposes of simplicity, it is assumed that IMEI/ESN is valid. 
   The process  500  enters the call set up for the on network portion of the call process. At step  523 , the cellular transceiver  106 B communicates a call set up request message to first switch  128 . This can be done after the first cellular transceiver  106 B begins ciphering the radio channel. Included in this request message are the dialed digits. 
   In response to first switch  128  receiving the call set up request message, first switch  128 , at step  524 , will communicate an access subscriber data message to HLR  128 C. The HLR  128 C will be requested to supply the subscriber parameters necessary for handling the call. The message will contain a caller number and service indication, if required and available. At step  525 , the HLR  128 C will communicate the called subscriber data to first switch  128 . The HLR  128 C will check the call for call barring conditions, such that the first cellular transceiver  106 B be barred from making specific outgoing calls or possibly if some supplementary services are active which prevent the call from being granted. If the HLR  128 C determines that a call cannot be processed, the HLR  128 C will provide the reason to first switch  128 . For purposes of simplicity, it is assumed that this procedure is successful. The HLR  128 C returns a message to first switch  128  containing the service parameters for the particular subscriber. 
   At step  526 , first switch  128  communicates the call proceeding message to first cellular transceiver  106 B. This indicates that a call is being processed. At step  527 , first switch  128  communicates a network set up message to PSTN  132 . A trunk will be established between first switch  128  and PSTN  132 . At step  528 , PSTN  132  communicates a network alerting message to first switch  128 . This message alerts the first switch  128  that a path has been established between first switch  128  and second switch  138 . Included in this message are cellular transceiver&#39;s  106 B dialed digits and details specifying which trunk should be used for the call. The process  500  proceeds to step  529  where the first switch  128  communicates an alerting message to first CT  106 B. This alerting message alerts the CT  106 B that a path has been established. Subscriber A will hear ringing from first telephone  104 . 
   At step  530 , first switch  128  communicates a message to first CPBTG  122  that a trunk between first switch  128  and CPBTG  122  currently serving the cable subscriber has been allocated. At step  530 , included in this message is a trunk number allocated. At step  531 , first CPBTG  122  communicates an assigned voice channel message to first cellular transceiver  106 B. In turn, first cellular transceiver  106 B communicates at step  532  an assigned voice channel to first MTA  106 A. 
   In response to the assigned voice channel message from first cellular transceiver  106 B, first MTA  106 A, at step  533 , communicates a voice channel assigned message to first cellular transceiver  106 B. First MTA  106 A has created an IP voice path to the CPBTG  122  and communicates a path assignment complete message to first cellular transceiver  106 B. At step  534 , first cellular transceiver  106 B communicates a voice channel assigned and complete message to first BSS  126 . At this point, CPBTG  122  connects the voice channel to the assigned trunk to first switch  128 . In turn, first BSS  126  at step  535 , communicates the trunk and CPBTG  122  channel number assigned and complete message to first switch  128 . The CPBTG channel assigned is a voice channel. 
   The process  500  proceeds to the call set up off network portion of the process. At this point, the voice path has been established between the cellular transceiver  106 B and first switch  128 . Subscriber A hears silence since a complete voice path has not yet been established. The last phase of setting up a mobile originated call involves first switch  128  establishing a voice path from first switch  128  to the PSTN  132 . At step  536 , subscriber B has picked up telephone handset  162 . This information is communicated to the public switched telephone network  132 . The public switched telephone network in turn communicates this information to first switch  128 . At step  537 , the first switch  128  communicates a connect message to first MTA  106 A. The process  500  then proceeds to step  538 . 
   At step  538  a voice path is established between first MTA  106 A and public switched telephone network  132 . At step  539 , first MTA  106 A communicates a connect acknowledgement message to first switch  128 . Communication between subscriber A and subscriber B can commence. 
   The process  500  enters the disconnect phase of the call process. In the disconnect phase of the call process, a call can be terminated in one of two ways either via subscriber A hanging up the handset or subscriber B hanging up the handset. For purposes of simplicity, it is assumed that subscriber A hangs up the handset. At step  540 , the first MTA  106 A detects subscriber A hanging up telephone  104  and communicates a disconnect message to first cellular transceiver  106 B. At step  541 , the first cellular transceiver  106 B communicates the disconnect message to first BSS  126 . In turn first BSS  126  communicates, at step  542 , a disconnect message to first switch  128 . 
   In response to receiving a disconnect message from first BSS  126 , first switch  128 , at step  543 , communicates a network release message to PSTN  132 . The network release message is a command to release the call. The PSTN  132  and first switch  128  will disconnect the call via the trunk connecting first switch  128  and PSTN  132 . When the trunk has been released, first switch  128  will communicate a release command at step  543  to first BSS  126 . First BSS  126  will in turn communicate the release message to first cellular transceiver  106 B. First cellular transceiver  106 B will in turn communicate the release message to first MTA  106 A at step  546 . The process  500  then proceeds to step  547 . 
   At step  547 , the first cellular transceiver  106 B will communicate a release complete message to first BSS  126 . The first BSS  126 , at step  548 , will communicate a release complete message to first switch  128 . At step  549 , first switch  128  will communicate a clear command message to CPBTG  122 . In response, CPBTG  122 , at step  550 , will communicate a release voice channel message to first MTA  106 A. First MTA  106 A will issue a clear complete message at step  551  to first cellular transceiver  106 B. At step  552 , first cellular transceiver  106 B communicates a clear complete message to first BSS  126 . Finally, BSS  126 , at step  553 , communicates a clear complete message to the first switch  128 . 
     FIG. 6  depicts a call flow diagram useful in understanding an embodiment of the present invention. Specifically,  FIG. 6  depicts an off network to on network call routing call flow. Party C initiates a telephone voice call by picking up telephone  136  at step  601  and dialing party A&#39;s mobile subscriber integrated services digital network (MSISDN) number. At step  602 , PSTN  130  routes the call to gateway switch  131  assigned to its direct number. Gateway switch  131  sends a message to the HLR  128 C requesting it to provide routing information for the MSISDN. In response, the message at step  603  HLR  128 C returns to gateway switch  131  a directory number of first cellular transceiver  106 B. As previously mentioned VLR/HLR can be stored on a switch or external to a switch. For purposes of simplicity it is assumed the HLR/VLR is stored on first switch  128 . But those skilled in the art will know that HLR/VLR can be stored anywhere even on gateway switch  131 . The method  600  proceeds to step  604 . 
   At step  604 , gateway switch  131  communicates an incoming call message to subscriber A&#39;s serving switch, for example, first switch  128 . At step  605 , first switch  128  uses the location area identifier to determine which BSS should page the first cellular transceiver  106 B. First switch  128  transmits a message to the BSS, for example first BSS  126 , requesting that a page be performed. Included in the message is a TMSI of first cellular transceiver  106 B. 
   In response to the perform page message, first BSS  126 , at step  606 , broadcasts the TMSI of first cellular transceiver  106 B on a paging channel. When first cellular transceiver  106 B hears its TMSI, or IMSI, at step  607 , broadcasted on the paging channel, first cellular transceiver  106 B responds with a channel request message over a common access channel, for example random access channel (RACH). The access scheme for this channel is similar in concept to slotted ALOHA. 
   In response to the channel request message, first BSS  126 , at step  608 , allocates a stand alone dedicated control channel (SDCCH) and forwards this channel assignment information to first cellular transceiver  106 B over the access grant channel (AGCH). It is over the SDCCH that first cellular transceiver  106 B will communicate with first BSS  126  and first switch  128  until a traffic channel is assigned. The method  600  proceeds to step  609 . 
   At step  609 , first cellular transceiver  106 B transmits a page response message to first BSS  126  over the SDCCH. Included in this message is first cellular transceiver&#39;s  106 B, TMSI and location area identification (LAI). This message also establishes a layer 2 signaling connection between first cellular transceiver  106 B and first BSS  126 . 
   In response to receiving the page response message first BSS  126 , at step  610 , forwards the page response message to first  128 . This message also causes the start up of an SCCP connection, if the first cellular transceiver  106 B does not have any other call instances active. 
   Call process  600  now enters the authentication portion of the call process. Since the air interface is vulnerable to fraudulent access, it is necessary to determine if the TMSI received from the first cellular transceiver  106 B is from the SIM that was assigned the TMSI. Authentication is built around the notion that an authentication key (Ki) resides in only two places: in an authentication center (AUC) and in the user&#39;s SIM card. Since the authentication key is never to be transmitted, it is virtually impossible for unauthorized individuals to obtain this key to impersonate a given cellular transceiver. 
   At step  611 , the HLR  128 C requests authentication parameters from the authentication center (AUC)  128 D. At step  612 , the AUC  128 D, using the IMSI, extracts the subscriber&#39;s authentication key (Ki). The AUC  128 D then generates a random number, applies the Ki and RAND to both the authentication algorithm (A 3 ) and a cipher key generation algorithm (A 8 ) to produce an authentication signed response and a cipher key (Kc). The AUC  128 D then returns to the HLR  128 C and authentication triplet: RAND, SRES and Kc. 
   At step  613 , HLR  128 C sends a message to first switch  128  requesting that the first cellular transceiver  106 B be authenticated. Included in the message is a random number. The process  600  proceeds to step  614 . 
   At step  614 , first switch  128  forwards the authentication request message to the first cellular transceiver  106 B. First cellular transceiver  106 B reads its authentication key (Ki) from the SIM, applies the random number and Ki to both its authentication algorithm (A 3 ) and cipher key generation algorithm (A 8 ) to produce an authentication signed response (SRES) and cipher key (Kc). First cellular transceiver  106 B saves Kc for later, and will use Kc when it receives a command to cipher the channel. At step  615 , first cellular transceiver  106 B returns to generate an SRES to first switch  128 . 
   In response to the message, first switch  128 , at step  616 , forwards the SRES message to the HLR  128 C. The HLR  128 C compares the SRES returned from first cellular transceiver  106 B with the expected SRES received earlier from the AUC  128 D. If equal, first cellular transceiver passes authentication. If unequal, appropriate action will be taken which could result in the SIM being disabled. For purposes of simplicity, it is assumed that cellular transceiver  106 B passes authentication. 
   The process  600  enters the ciphering portion of the call flow where at step  617 , the HLR  128 C requests that first switch  128  cipher the radio channel. Included in this message is a cipher key (Kc), which was made available during authentication. 
   In response to the set ciphering message, the first switch  128 , at step  618 , forwards this request to first BSS  126 . At step  619 , first BSS  126  retrieves the cipher key, Kc, from the message and then transmits a request to first cellular transceiver  106 B requesting it to begin ciphering the channel. 
   In response to the cipher mode command message first cellular transceiver  106 B, at step  620 , uses the cipher key generated previously when it was authenticated to cipher the up link channel, and transmits a confirmation over the cipher channel to first BSS  126 . At step  621 , the first BSS  126  upon receiving the cipher mode complete message uses the cipher key previously received from first switch  128  to cipher the downlink channel. The first BSS  126  then sends a cipher complete message to first switch  128 . 
   The process  600  now enters the equipment validation phase of the call process flow. The purpose of the equipment validation phase is to read the cellular equipment serial number from first cellular transceiver  106 B and check it against the equipment identity register (EIR)  128 E to determine if special action should be taken, such as deny service. Equipment validation is optional and is controlled by the service provider. Equipment alienation is performed after the cipher phase and can be performed in parallel with call setup or is even performed after the call is set up. For purposes of simplicity, call flow diagram  600  shows the equipment validation phase occurring before call setup. In actuality, the call set up phase will probably be performed immediately after ciphering in order to keep call set up delays at a minimum. Equipment validation would typically occur during call set up. 
   At step  622 , first switch  128  transmits a request to first cellular transceiver  106 B requesting it to respond with an international mobile equipment identity or electronic serial number. 
   In response to a request for an IMEI/ESN, first cellular transceiver  106 B, at step  623 , communicates an equipment serial number and returns its value to first switch  128 . At step  624 , first switch  128  then requests the EIR  128 E to check the IMEI/ESN for validity. The EIR  128 E will first check to see if the IMEI/ESN value is within a valid range. If so, it then checks to see if the IMEI/ESN is on a suspect or known list of invalid equipment. The process  600  then proceeds to step  625 . 
   At step  625 , the EIR  128 E returns to first switch  128  the results of the IMEI validation. If the results are negative, first switch  128  might abort a call or possibly let the call continue but inform the network service provider of the event. For purposes of simplicity, it is assumed that the IMEI/ESN is valid. Call process  600  now enters the call set up phase of the call process flow. At step  626 , first switch  128  communicates a call set up message to first cellular transceiver  106 B. After first switch  128  received the encipher complete message from the first cellular transceiver  106 B, first cellular transceiver  106 B is informed that a call will be set up via a set up message. 
   Upon receiving the set up message, first cellular transceiver  106 B performs a compatibility check before responding to the set up message. It is possible that first cellular transceiver  106 B might be incompatible for certain types of call set ups. Assuming that first cellular transceiver  106 B passes the compatibility check, it acknowledges the call set up message, at step  627 , with a set up confirm message to first switch  128 . The call process of  600  then proceeds to step  628 . 
   At step  628 , first switch  128  communicates an assign trunk message to CPBTG  122 . CPBTG  122  assigns a trunk from the trunks linking CPBTG  122  and first switch  128 . At step  629 , CPBTG  122  communicates an assign IP voice channel message to cellular transceiver  106 B. 
   In response to the assign voice channel message, cellular transceiver  106 B creates an IP voice path to CPBTG  122  and communicates a voice channel complete message to CPBTG  122 , at step  630 . CPBTG  122 , in turn, communicates a trunk assignment complete message to first switch  128  indicating that a trunk has been selected, at step  631 . Included in this message is a trunk number. The process  600  then proceeds to step  632 . 
   At step  632 , once alerting has begun, first cellular transceiver  106 B sends an alerting message to first BSS  126 . In response to the alerting message, first BSS  126 , at step  633 , forwards an alerting message to first switch  128 . 
   Upon receiving the alerting message, first switch  128 , at step  633 , communicates a network alerting message to PSTN  130 . First switch  128  communicates audible ringing to subscriber A. Prior to this, the calling party heard silence. 
   At step  635 , subscriber A picks up telephone  104 . In response to this first cellular transceiver  106 B stops alerting and sends a connect message to first switch  128 . 
   In response to receiving a connect message from CT  106 B, first switch  128  communicates an acknowledgement message to CT  106 B. 
   First switch  128 , at step  637 , removes audible ringing to PSTN  130  and connects the PSTN trunk to first BSS  126  and sends a connect message to the PSTN  130 . At step  638 , a voice channel is established between subscriber A and subscriber C. 
   Call process  600  now enters the release stage. At step  639 , subscriber C hangs up the telephone  136 . This results in PSTN  130  sending a network release signal to first switch  128 . The actual type of message that is received from the remote exchange depends on country signaling conventions. This message could, for example, be a clear-forward message (Q.721–Q.725) or release message (Q.761–Q.764). 
   At step  640 , first switch  128  requests first cellular transceiver  106 B to begin its clear procedure. In response to the disconnect message, first cellular transceiver  106 B, at step  641 , informs first switch  128  that it has started its clear procedure by communicating a release message. The process  600  then proceeds to step  642 . 
   At step  642 , the first switch  128  acknowledges receiving first cellular transceiver&#39;s  106 B release message by communicating a release complete message to cellular transceiver  106 B. First cellular transceiver  106 B completes its clear procedure. 
   The previous four steps cause a given instance of a call to be released. If the first cellular transceiver  106 B has one or more other instances of a connection active between itself and the first switch  128 , then the next three steps are not performed. With respect to signaling, a cellular transceiver can have several instances of calls all sharing the same voice switch dedicated signaling connection. The signaling connection control part (SCCP) layer of the “A interface” between first BSS  126  and first switch  128  is used in a connection oriented fashion. A SCCP connection is established when a cellular transceiver first gains access to the network and is torn down when all call activity instances have concluded. 
   At step  643 , assuming that there are no more instances of calls with first cellular transceiver  106 B, first switch  128  sends a clear command to first BSS  126  asking it to release all allocated dedicated resources for a given SCCP connection. 
   In response to the clear command, first BSS  126 , at step  644 , instructs first cellular transceiver  106 B to release the radio traffic channel by communicating a release message. First cellular transceiver  106 B would then go back to its idle mode of operation, which involved searching and returning to the strongest signal from first BSS  126 . 
   Finally, at step  645 , first BSS  126  acknowledges that it has released all allocated dedicated resources. 
   Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. As such, the appropriate scope of the invention is to be determined according to the claims which follow herewith.