Abstract:
An 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 switch to establish a phone call.

Description:
TECHNICAL FIELD 
   The invention relates to the field of communications systems and, more particularly, to an 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 an apparatus 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, an apparatus for providing bifurcated voice and signaling data over a network, comprising: a memory, for storing protocols for interfacing with the network; and a processor, coupled to said memory, for segregating signaling traffic and related voice traffic including information useful in establishing a communications link, for transporting said voice traffic between a calling party and called party, and for transmitting said voice traffic and said signaling traffic via different communication 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 an integrated multi-media terminal adapter and cellular transceiver; 
       FIG. 3  depicts the software architecture of the MTA-CT for use in the communications system of  FIG. 1 ; and 
       FIG. 4  depicts the software architecture for a nonintegrated MTA and CT. 
   

   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 and a cellular transceiver (CT)  106 B. 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 (DSO) 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 also 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 the authenticy of the cell phone&#39;s 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 . PSTN  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 DSO channel on T1 trunk  127 . Signaling between first BSS  126  and first switch  12 B 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. 
   It will be appreciated by those skilled in the art that other communication protocols other than DOCSIS may be substituted. 
   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 an integrated multi-media terminal adapter and cellular transceiver. Specifically,  FIG. 2  depicts the MTA  106 A and the cellular transceiver  106 B discussed above with respect to the first MTA-CT of FIG.  1 .
         MTA-CT  106  comprises a Digital Signal Processing (DSP) portion, a cellular portion, a user interface portion, a battery back up portion and a data portion.       
   The DSP portion transmits, receives and processes signals from the data portion, the user interface portion and cellular portion of MTA-CT  106 . The cellular portion communicates signaling messages with first BSS  126 . The data portion of MTA-CT  106  communicates data information between MTA-CT  106  and first cable modem  108 . The user interface portion communicates with the data portion and cellular portion as well as peripheral devices. 
   The user interface portion provides the user interface functions of a telephone and may include an interface jack interfacing with a telephone. For example, an RJ11 jack. Traditional interface devices can be a key pad for dialing numbers, an audible indicator for announcing calls, keys such as mute, redial, hold, transfer, conferencing, a display for displaying user prompts, number dialed, Caller ID and the like. It should be noted that those skilled in the art may devise other devices that can be used with the present invention. 
   The data portion of the MTA-CT  106  comprises, illustratively, an Ethernet control processor  218  for processing data information from the DSP portion of the circuit and from the user interface portion of the circuit. Ethernet control processor  218  performs the voice processing, call processing, and network management software functions of MTA-CT  106 . 
   Random Access Memory (RAM)  214  is coupled to Ethernet control processor  218 . Flash memory  212  is also coupled to Ethernet control processor  218  as well as Ethernet transceiver  244 . 
   Ethernet transceiver  244  serves as an interface to data devices such as cable modem  108  or first computer terminal  102 . In addition, ethernet transceiver  244  allows the transmission and reception of voice packets from/to an IP telephone. The interface to the ethernet transceiver  244  and an external device can be, for example an RJ45 jack. 
   Flash memory  212  allows easy upgradability of MTA-CT  106  since changes to standards or protocols can be reprogrammed in blocks instead of one byte at a time. 
   The cellular portion of MTA-CT  106  comprises an antenna  202  for transmitting or receiving radio signals. The preferred embodiment is a mechanical antenna due to its ability to dither at small intervals, and thus can maintain accurate signal tracking when used in conjunction with an angular position determinant. It will be appreciated by those skilled in the art that an electronic antenna may also be substituted for the mechanical antenna. 
   A cellular transceiver  242  comprising a radio frequency section (not shown) is coupled to antenna  202 . Cellular control processor  228  is coupled to cellular transceiver  242  to process this cellular information and also communicate with the DSP portion and user interface portion of MTA-CT  106 . 
   Coupled to cellular control processor  228  are a Non-Volatile Random Access Memory (NVRAM)  226  and a Battery Back up Random Access Memory (BBRAM)  224 . NVRAM  226  provides memory retention when the power is off. Cellular control processor  228  together with NVRAM  226  and BBRAM  224  provide the overall executive control of the functions and interfaces of cellular transceiver  106 B. 
   Antenna  202  is also coupled to a diplexer  204  having a receive portion and a transmit portion. A low noise amplifier  206  is coupled to the receive portion of diplexer  204 . Low noise amplifier  206  amplifies the signal and communicates the signal to down converter mixer  208 . Down converter mixer  208  takes the high frequency signal from low noise amplifier  206  and combines it with a signal from synthesizer  234  and creates an intermediate frequency range signal for further processing. This signal having the intermediate frequency range is communicated to analog-to-digital converter  210  and is further communicated to the DSP portion of MTA-CT  106 . 
   The DSP portion of MTA-CT  106  communicates the signal to digital-to-analog converter  232  which, in turn, communicates the signal to up converter modulator  236 . Up converter modulator  236  also receives a signal from synthesizer  234 . Up converter modulator  236  takes the incoming signals and performs frequency translation in such a manner that the output frequency is higher than the input frequency. The output frequency is communicated to high power amplifier  238  which in turn communicates the signal to the transmit portion of diplexer  204 . Diplexer  204  allows radio frequency signals to be received and transmitted simultaneously. 
   The DSP portion of MTA-CT  106  comprises a modem  220  and an audio coder  222 . The modem  220  modulates and demodulates signals from the data portion and cellular portion of MTA-CT  106 . Audio coder  222  interfaces various peripheral devices such as an ear phone, microphone, an RJ11 jack for connecting a telephone, and the like. Audio coder  222  provides a conversion of analog voice into digital samples and vice versa. It also communicates these signals to data portions and cellular portions of MTA-CT  106 . 
   The power battery backup portion of MTA-CT  106  includes an uninterruptable power supply (UPS)  216  which converts household power to direct current power for MTA-CT  106 . UPS  216  also provides battery backup to maintain MTA-CT  106  operation through local power outages. For phone service to be operational the phone must be capable of originating calls, ringing, and terminating calls. Coupled to UPS  216  is a local power failure detector and communicator  246 . Local power failure detector communicator  246  detects an absence of local power and in turn communicates a signal to the head end office alerting personnel to the absence of local power. 
   It is assumed for the purposes of powering that first MTA-CT  106  is integrated into the first cable modem  108 . Cable modem failure detection requirements can be found in document DOCSIS operation support system interface specification document number SP-OSSIv1. 1-D01991115. 
   It should be appreciated by those skilled in the art that if the first MTA-CT  106  is not integrated into first cable modem  108  then the UPS  216  and local power failure detector communicator  246  are supporting both first cable modem  108  and MTA-CT  106  independently. 
   It should also be noted that the processor portions of the circuit comprising Ethernet control processor  218 , cellular control processor  228  and DSP portion of MTA-CT  106  are each described as performing separate functions, for example, voice processing, call processing, protocol processing, and network management software management functions of the telephone. This may consist of a digital signal processor for voice related functions, Ethernet control processor for controlling Ethernet functions and cellular control processor for controlling cellular transceiver functions. However, such functions can be integrated into a single processor. 
     FIG. 3  depicts the software architecture of the MTA-CT for use in the communications system of FIG.  1 . Specifically, the software architecture  300  comprises four layers. Software architecture  300  allows a uniform interface for hiding MTA-CT  106  related protocols, and other hardware specific details. This abstracts and provides a uniform view of the underlying integrated system. 
   The real-time operating system (RTOS) interfaces the physical layer containing the hardware components of MTA-CT  106 . The ROTS layer includes a link/media access control (MAC)  302  layer which controls access to the cellular system physical layer. The RTOS layer also provides standard interfaces such as flash memory interface  304 , DSP interface  308 , an infrared data association (IrDE) interface  310 , a serial interface  338 , a display interface  340 , and a universal serial bus (USB) interface  342 . Drivers such as the Ethernet driver  306  are also supported on the RTOS layer. 
   The RTOS layer also includes a data packet structure portion for implementation which includes an internet protocol (IP)  312  data structure for keeping track of internet addresses for different nodes, for routing outgoing messages and recognizing incoming messages. A “user datagram protocol” (UDP)  316  packet structure which transports packets and transmission control protocol (TCP)  314  packet structure are encapsulated in the IP  312  data structure. Real time transport protocol (RTP)  318  which supports a transport of real time data, for example like interactive voice or video is encapsulated in the UDP  316  packet structure. The data packet structure portion can be utilized by the link/MAC layer  302  and/or the Ethernet drivers  306 . 
   The second layer, the device server layer, includes two different device servers, one for cellular transceiver  106 B and one for MTA  106 A. The cellular transceiver device server includes a radio resource management  320  component. Above the radio resource management  320  component is a mobility management  322  component. Call control component  328 , message support component  326  and miscellaneous services component  324  are above mobility management component  322 . Mobility management component  322 , call control  328 , message support  326  and miscellaneous services  324  are used in setting up of services between cellular transceiver  106 B and the first base station system  126 . The cellular transceiver device server is used to set up and tear down calls, and to support messaging and other advanced services. Additionally, cellular transceiver device server interfaces with the link/MAC layer  302  and the data packet structure portion. 
   The second device server of the device server layer applies to MTA  106 A. Device server  330  handles all the registration, management, signaling and other services required by MTA  106 A and communicates with a call server at the cable hub. The call server at the cable hub determines specific properties of device server  330 . MTA device server interfaces with the data packet structure portion. The third layer, the transparent media layer, provides a critical function of providing a seamless integration of cellular and cable functions in one unit such that MTA  106 A and cellular transceiver  106 B function as one unit. The transparent media layer includes a management component  336  which handles operations administration and maintenance (OAM), a transparent media handler  334  and a user interface control interface  332 . OAM includes fault management, compression, dial plan, securities, authentication, and other services. The management component  336  interfaces with the cellular transceiver device server and MTA device server  330  and transparent media handler  334 . 
   Transparent media handler  334  manages the functions of MTA-CT  106  before, during, and after the call set up and the media transfer and determines the medium through which data and signaling is transmitted. The transparent media handler  334  can also be used to negotiate CODEX, select different compression techniques, mix data streams, perform authentication, and various other features such as using resources, such as new compression techniques, dial plan, and the like, from the device server  330  in cellular transceiver stack device server and vice versa. Transparent media handler  334  interfaces the cellular transceiver stack, device server  330  and user interface control interface  332  and distal signal processor interface  308 . 
   The user interface control interface  332  interfaces with serial interface  338 , USB interface  342 , display interface  340  and transparent media handler component  334 . 
   The fourth layer, the application layer, is above the transparent media layer and interfaces with the device server layer. The application layer allows rapid development of applications for the MTA-CT  106  through the application programming interface (API) provided by the transparent media layer component  334 . The APIs and the separation of details from the device server layer by the transparent media layer provide the necessary abstraction for new applications to take advantage of unique interface of the MTA-CT  106 . 
   Signaling is normally done through cellular transceiver  106 B and data is transmitted through MTA  106 A in the RTOS layer. However, if management component  336  detects that the MTA&#39;s  106 A link is down, then the transparent media layer  334  switches to transmitting the data through the cellular transceiver  106 B. This switching is done without the knowledge of the application layer above. That is, the application layer does not need to care about the switch from transmitting data through MTA  106 A to transmitting data to CT  106 B. The transparent media handler component  334  allows the application layer control over starting, stopping and other features of media streams without providing the application layer any control over the transmission medium. 
     FIG. 4  depicts the software architecture for a nonintegrated MTA and CT. Specifically, MTA-CT  106  comprises an MTA  106 A that is off the shelf and a cellular transceiver  106 B that is off the shelf. The application layer and transparent media layer of  FIG. 3  remain the same. More specifically,  FIG. 4  depicts a cellular transceiver hardware component  401  with a cellular transceiver software component  402  above it. Cellular transceiver software  402  interfaces with a management layer  336  and transparent media handler component  334 . MTA hardware component  403  is below MTA software component  404 . MTA software component  404  interfaces with transparent media handler  334 . Functionally, the MTA  106  of  FIG. 4  operates similarly to the MTA  106  of FIG.  3 . Only the layer below the transparent media layer is changed and the interaction between the transparent media layer and the layer below, protocols and RTOS layers has changed. 
   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.