Abstract:
There is provided system and method for receiving speech signals via a plurality of speech lines and communicating the speech signals over a phone line. For example, the communication system comprises a modem, a multiplexor in data communication with the modem, and a plurality of speech codecs in data communication with the multiplexor. According to this aspect, each of the plurality of speech codecs receives a portion of the speech signals via one of the plurality of speech lines and encodes that portion of the speech signals to generate encoded speech signals, and wherein the encoded speech signals from each of the plurality of speech codecs are multiplexed by the multiplexor to generate multiplexed encoded speech signals, and wherein the modem transmits the multiplexed encoded speech signals over the phone line.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to voice communication and, more particularly, to systems and methods for voice communication using speech compression and modem technologies. 
   2. Related Art 
   Today, various means are employed to access the central office (“CO”) for voice communications. For example, residential customers use the standard twisted pair for voice communications through the CO. Also, as shown in  FIG. 1 , communication system  105 , such as those used by commercial entities and large enterprises, use T1/E1 line  110  for voice connectivity to CO  115 . As shown, CO  115  routes the voice traffic through T1/E1 line  110  through public switched telephone network (“PSTN”) lines  120  for delivery to the ultimate recipients of the voice communications. 
   A major drawback of T1/E1 line  110  or other broadband media is the tremendous cost associated with such services. For example, today, the service cost for a single T1 line is about $500-$1,200 per month. This price is extremely high when compared to the monthly cost of a twisted pair or an analog telephone line, which is about $10-$15 per month. On the other hand, a twisted pair or an analog telephone line can only support one voice channel, whereas a T1 line is capable of supporting up to 24 voice channels and an E1 line is capable of supporting up to 30 voice channels. 
   Accordingly, there is an intense need for a new voice access or communication model that can provide a communication bandwidth comparable to T1/E1 lines, but at the cost comparable to that of an analog telephone line. 
   SUMMARY OF THE INVENTION 
   In accordance with the purpose of the present invention as broadly described herein, in one aspect of the present invention, there is provided system and method for receiving speech signals via a plurality of speech lines and communicating the speech signals over a phone line. For example, the communication system comprises a modem, a multiplexor in data communication with the modem, and a plurality of speech codecs in data communication with the multiplexor. According to this aspect, each of the plurality of speech codecs receives a portion of the speech signals via one of the plurality of speech lines and encodes that portion of the speech signals to generate encoded speech signals, and wherein the encoded speech signals from each of the plurality of speech codecs are multiplexed by the multiplexor to generate multiplexed encoded speech signals, and wherein the modem transmits the multiplexed encoded speech signals over the phone line. 
   In another aspect, there is provided system and method for receiving modulated multiplexed encoded speech signals via a phone line for communication over a plurality of speech lines. For example the communication system comprises a modem, a demultiplexor in data communication with the modem, and a plurality of speech codecs in data communication with the demultiplexor. According to this aspect, the modem receives the modulated multiplexed encoded speech signals over the phone line and demodulates the modulated multiplexed encoded speech signals to generate multiplexed encoded speech signals, and wherein the demultiplexor demultiplexes the multiplexed encoded speech signals to generate a plurality of encoded speech signals, and wherein each of the plurality of speech codecs receives one of the plurality of encoded speech signals and decodes the one of the plurality of encoded speech signals to generate a plurality of speech signals for communication over the plurality of speech lines. 
   These and other aspects of the present invention will become apparent with further reference to the drawings and specification, which follow. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The features and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein: 
       FIG. 1  illustrates a conventional voice communication system or model; 
       FIG. 2  illustrates a conventional modem communication system or model; 
       FIG. 3  illustrates a voice access model according to one embodiment of the present invention; 
       FIG. 4  illustrates a voice transmission model according to one embodiment of the present invention for use in conjunction with the voice access model of  FIG. 3 ; and 
       FIG. 5  illustrates a voice reception model according to one embodiment of the present invention for use in conjunction with the voice access model of  FIG. 3 . 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   The present invention may be described herein in terms of functional block components and various processing steps. It should be appreciated that such functional blocks may be realized by any number of hardware components and/or software components configured to perform the specified functions. For example, the present invention may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, and the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. Further, it should be noted that the present invention may employ any number of conventional techniques for data transmission, signaling, signal processing and conditioning, tone generation and detection and the like. Such general techniques that are known to those skilled in the art are not described in detail herein. It should be appreciated that the particular implementations shown and described herein are merely exemplary and are not intended to limit the scope of the present invention in any way. 
     FIG. 2  illustrates conventional modem communication system or model  200  that is typically employed for use by communication system  205  for data communication. As shown, communication system  205  can use modem  207  to call modem  225  via phone line  210 . Phone line  210  is routed through central office  215  and PSTN lines  220  to provide a communication link between modem  207  and modem  225 . After an initial training, modem  207  and modem  225  are able to establish a communication channel or connection via the communication link through phone line  210 , central office  215  and PSTN lines  220 . Modem  207  is capable of receiving data from communication system  205 , modulating the data to generate modulated data and performing digital-to-analog conversion for transmission of the modulated data as analog signals via a telephone line to modem  225 . Modem  225  is also capable of receiving the analog signals, performing analog-to-digital conversion to obtain the modulated data and demodulating the modulated data retrieve the data. Modem  225  may be connected to a network or an Internet Service Provider (“ISP”). 
     FIG. 3  illustrates voice access model  300  according to one embodiment of the present invention. The exemplary voice access model of  FIG. 3  illustrates an alternative to the T1/E1-based communication systems, and provides a voice communication bandwidth, which is comparable T1/E1, but at the low cost of analog voice or phone lines. In the exemplary embodiment of  FIG. 3 , voice access model  300  uses three phone lines  311 ,  312  and  313  to provide communication links between communication system  310  and central office  315 , rather than using expensive broadband communication lines, such as T1/E1 lines. 
   As shown, communication system  310  includes a number of modems, such as modem  307 , modem  308  and modem  309 . Each of modems  307 ,  308  and  309  is in communication with central office  315  via phone lines  311 ,  312  and  313 , respectively. Further, each of modems  307 ,  308  and  309  receives data from codec/multiplexor  304 ,  305  and  306 , respectively, and transmits the data over phone lines  311 ,  312  and  313 , respectively. As it is known in the art, each speech codec (coder/decoder) includes an encoder portion for coding speech signal and a decoding portion for decoding coded speech signal. Each of lines  301 ,  302  and  303  includes a plurality of speech lines. 
   Referring now to  FIG. 4 , it illustrates voice transmission model  400  according to one embodiment of the present invention for use in conjunction with voice access model  300  of  FIG. 3 . It should be noted modem  440  represents each of modems  307 ,  308  and  309 ; phone line  445  represents each of phone lines  311 ,  312  and  313 ; multiplexor  404  and speech encoders  411 - 418  represent each of codec/multiplexor  304 ,  305  and  306 ; and speech lines  401 - 408  represent each of lines  301 ,  302  and  303 . 
   In  FIG. 4 , exemplary modem  440  is shown to accommodate a plurality of speech lines  401 - 408  carrying speech signals emanating from a plurality of sources (not shown). Each speech line  401 - 408  arrives at its respective speech encoder  411 - 418 , where the speech signal is compressed or encoded to generate coded speech  421 - 428 . Speech encoders  411 - 418  may use a variety of speech coding algorithms for compressing the speech signal. For example, in one embodiment, speech encoders can implement and are in compliance with the Selectable Mode Vocoder (“SMV”) standard, entitled “Selectable Vocoder Mode Service Option for Wideband Spread Spectrum Communication Systems”, dated December 2001, 3GPP2, Version 2, which is hereby incorporated by reference. In an embodiment utilizing the SMV standard, communication system  300  will also allow dynamic quality adjustments to improve the voice quality. Continuing with  FIG. 4 , multiplexor  430  receives the plurality of coded speeches  421 - 428  and generates multiplexed coded speech  435  including a combination of the plurality of coded speeches  421 - 428 . Next, modem  440  performs modulation and digital-to analog conversion on multiplexed coded speech  435  for transmission on phone line  445 . Modem  440  may perform modulation/demodulation in accordance with any proprietary scheme or in compliance with a variety of known standards, such as V.92, V.90, V.34, V.32bis, V.32, V.22bis, V.22, etc. 
   According to the SMV standard, full-rate speech compression requires about 8 kbps of data bandwidth, half-rate speech compression requires about 4 kbps of data bandwidth, and quarter-rate speech compression requires about 2 kbps of data bandwidth. Therefore, if each speech encoder  411 - 418  performs speech compression at the full-rate, coded speeches  421 - 428  would each require about 8 kbps of data bandwidth, which results in about 64 kbps of total data bandwidth for multiplexed coded speech  435  that can be accommodated by modem  440 . Accordingly, modems  307 ,  308  and  309  may each provide eight (8) channels of full-rate speech, or twenty-four channels in total, via regular telephone lines. In other words, in one embodiment, the present invention can provide the same number of channels as a T1 line at the cost of three regular phone lines. Yet, in other embodiments, all speech encoder  411 - 418  may perform speech compression at the half-rate, in which event, coded speeches  421 - 428  would each require about 4 kbps of data bandwidth, which results in 32 kbps of total data bandwidth for multiplexed coded speech  435 . Therefore, in such embodiment, the number of speech lines may be increased from eight (8) to sixteen (16) to accommodate sixteen speech lines per modem, which results in forty-eight speech lines or twice as many speech channels that can be supported by a single T1 line. Of course, speech encoders  411 - 418  may each run at a different rate, based on various predetermine settings, or dynamically change based on system requirements or speech compression algorithm or protocol, such as SMV. It should be noted that in some embodiments, each speech encoder  411 - 418  may use a different speech encoding algorithm. For example, one speech encoder may encode the speech signal in compliance with the G.711 standard, whereas another encoder may operate according to the G.723.1 standard, the G.729 standard, or the SMV standard, etc. 
   Turning to  FIG. 5 , it illustrates voice reception model  500  according to one embodiment of the present invention for use in conjunction with voice access model  300  of  FIG. 3 . It should be noted modem  510  represents each of modems  317 ,  318  and  319 ; phone line  505  represents each of phone lines  311 ,  312  and  313 ; demultiplexor  520  and speech decoders  541 - 548  represent each of demultiplexor/codec  321 ,  322  and  323 ; and speech lines  551 - 558  represent each of PSTN lines  326 ,  327  and  328 . According to  FIG. 5 , exemplary modem  510  is shown to receive, on phone line  505 , the data transmitted by exemplary modem  440  on phone line  445 . Modem  510  converts the analog signal on phone line  505  to digital data, which is then demodulated by modem  510  to obtain multiplexed coded speech  515 . As shown in  FIG. 5 , demultiplexor  520  demultiplexes multiplexed coded speech  515  and routes coded speeches  531 - 538  to their respective speech decoders  541 - 548 . Each speech decoder  541 - 548  decodes or decompresses respective coded speeches  531 - 538  in accordance with the speech compression algorithm used by respective speech encoders  411  - 418 . After decoding each of coded speeches  531 - 538  by respective speech decoder  541 - 548 , speech decoders  541 - 548  generate audio or analog speeches  551 - 558 , which are provided to users over analog telephone lines  551 - 558 . 
   In some embodiments communication system  310  may be a single device at a voice gateway or a PBX gateway that can operate in conjunction with a single device at CO  315  over a plurality of analog telephone lines. In one embodiment, one or more phone lines from CO  315  may bypass modems, encoders and multiplexors of communication system  310  and reach the user device to provide a direct connection, which may be used for modem connections, facsimile connections, regular voice connections, etc. In other embodiments, facsimile and modem connections may also be established through encoders, multiplexors and modems of communication system  310 . 
   In a further embodiment of the present invention, communication systems  310  includes a soft switch signaling module, which implements a soft switch signaling protocol, such as SS7 signaling for communication via PSTN lines. SS7 or Signaling System No. 7 is a global standard for telecommunications that defines the procedures and protocol by which network elements in the PSTN exchange information over a digital signaling network to effect wireless and wireline call setup, routing and control. 
   The methods and systems presented above may reside in software, hardware, or firmware on the device, which can be implemented on a microprocessor, digital signal processor, application specific IC, or field programmable gate array (“FPGA”), or any combination thereof, without departing from the spirit of the invention. Furthermore, the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.