Abstract:
A multi-media terminal adapter includes a narrowband SLIC and a wideband SLIC. A DSP circuit is configured to encode a VoIP data stream and to transmit the encoded VoIP data stream to the wideband SLIC or the narrowband SLIC. A processor determines whether the VoIP data stream includes narrowband audio data or wideband audio data, and instructs the DSP circuit to transmit the encoded VoIP data stream to the wideband SLIC or the narrowband SLIC depending on whether the received VoIP data stream includes narrowband audio data or wideband audio data.

Description:
BACKGROUND 
       [0001]    Plain Old Telephone Systems (POTS) represent the traditional type of analog phone service. POTS using the public switched telephone network (PSTN) to route calls. When a call is made, the telephone converts the caller&#39;s voice to analog electrical signals, which are transmitted over the local loop to a central office. The analog signals are converted to digital signals at the central office and transmitted over the PSTN to a central office local to the callee. The digital signals are converted to analog signals and sent to the callee&#39;s telephone via a local loop. 
         [0002]    Typically, a codec at the central office converts the analog voice signals to 64 kbs, digital, voice streams transmitted in the PSTN. The sampling rate for digitizing voice is 8 kHz for transmission in the PSTN, and frequencies below 200 Hz and above 3.4 kHz in the analog signals are filtered out. The 200 Hz to 3.4 kHz range is referred to as the narrowband. Better voice quality can be achieved by increasing the sampling rate and by sampling a greater frequency range. However, because of the limited capacity of the PSTN, the standard 64 kbs digital voice streams are beneficial to prevent overloading the PSTN. 
         [0003]    With the advances of voice over Internet Protocol (VoIP), where digital audio data is transmitted over the Internet, greater bandwidth is available for transmitting audio data between the caller and the callee. Accordingly, the concept of wideband telephony has gained increased awareness. Wideband telephony encompasses a frequency range from 50 Hz to 7 kHz, as opposed to the narrowband range of 200 Hz to 3.4 kHz traditionally used in POTS. Also, the sampling rate of wideband telephony, e.g., 16 kHz, can be approximately double the sampling rate of POTS. Thus, the sound quality of wideband telephony tends to be much better. 
         [0004]    Conventionally, VoIP service is provided at the customer premises using a cable or DSL modem and a multi-media terminal adapter (MTA). The MTA interfaces with an IP network and is operable to adapt VoIP data for use by customer premises equipment (CPE), such as telephones, connected to the subscriber line via home wiring. The MTA may be an embedded MTA (eMTA), which is an MTA and a modem incorporated in a single device, or the MTA may be provided as a standalone device connected to a modem. 
         [0005]    An MTA typically include subscriber line interface circuits (SLICs) and a digital signal processing (DSP) circuit for providing VoIP service. The SLIC emulates the functions of a central office. For example, the SLIC generates a line voltage on a loop line at the customer premises, which is typically provided by a telephone central office for traditional POTS service. For example, on-hook and off-hook voltages, also referred to as tip and ring voltages, are generated by the SLIC. 
         [0006]    As the popularity of wideband audio data increases, service providers need to deploy equipment that is capable of providing wideband audio services. For example, MTAs need to be modified to include SLICs that can supply wideband audio data to the customer premises equipment. Traditionally, MTAs include two narrowband SLICs, and service providers may simply replace all the narrowband SLICs with wideband SLICs. However, a wideband SLIC is typically more expensive than a narrowband SLIC, so replacing all narrowband SLICs with wideband SLICs is costly. Furthermore, the majority of audio data received at the MTA may be narrowband, and thus replacing all the narrowband SLICs may be unnecessary. 
       SUMMARY 
       [0007]    According to an embodiment, a multi-media terminal adapter includes a narrowband SLIC and a wideband SLIC. A DSP circuit is configured to encode a VoIP data stream and to transmit the encoded VoIP data stream to the wideband SLIC or the narrowband SLIC. A processor determines whether the VoIP data stream includes narrowband audio data or wideband audio data, and instructs the DSP circuit to transmit the encoded VoIP data stream to the wideband SLIC or the narrowband SLIC depending on whether the received VoIP data stream includes narrowband audio data or wideband audio data. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Embodiments are illustrated by way of example and not limited in the following Figure(s), in which like numerals indicate like elements, in which: 
           [0009]      FIG. 1  illustrates an MTA, according to an embodiment; 
           [0010]      FIG. 2  illustrates a system using the MTA, according to an embodiment; and 
           [0011]      FIGS. 3A-B  illustrate a method for dynamically routing wideband and narrowband audio data in an MTA, according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    For simplicity and illustrative purposes, the principles of the embodiments are described by referring mainly to examples thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one of ordinary skill in the art, that the embodiments may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the embodiments. 
         [0013]    According to an embodiment, an MTA includes one or more wideband SLICs and one or more narrowband SLICs. The MTA dynamically routes wideband and narrowband audio data between a DSP circuit and the SLICs depending on whether the data includes wideband audio data or narrowband audio data. A selection process is implemented to select a channel for transmitting VoIP data to the appropriate SLIC, i.e., either a wideband SLIC or a narrowband SLIC. Because the selection process is implemented, only a subset of the narrowband SLICs in an existing MTA may be changed to a wideband SLIC, which saves costs. Without the selection process, the DSP circuit may arbitrary pick a channel, which may result in wideband audio data being sent to a narrowband SLIC that is unable to process the wideband audio data. 
         [0014]      FIG. 1  illustrates an MTA  100  according to an embodiment. The MTA  100  may be a standalone MTA or an eMTA. The MTA  100  includes an interface  1   06 and VoIP data streams for calls are received via the interface  106  and are transmitted to the interface  106 . The interface  106  may be connected to a IP network, such as the Internet, and may include a modem. 
         [0015]    The MTA  100  includes a processor  101  and a computer readable medium storing software executed by the processor  101 . The computer readable medium may be comprised of a memory  102 . The software includes a call control layer that instructs a DSP circuit  103  to send data from received VoIP data streams to either a narrowband SLIC  110  or a wideband SLIC  111  depending on whether the data includes wideband audio data or narrowband audio data. 
         [0016]    The DSP circuit  103  processes the received VoIP data streams for transmission to the narrowband SLIC  110  and the wideband SLIC  111 . For example, the DSP circuit  103  may include a CODEC converting received VoIP data streams to a format for transmission on a bus  104  to the narrowband SLIC  110  and the wideband SLIC  111 . The format may include pulse code modulation (PCM). 
         [0017]    In addition, according to an embodiment, the DSP circuit  103  dynamically transmits VoIP data to the narrowband SLIC  110  and the wideband SLIC  111 . The bus  104  is shown as a cloud to illustrate that the bus may accommodate multiple channels and that the channels are dynamically selected as described above. For example, the bus  104  is a serial data bus. The DSP circuit  103  transmits data on the bus  104  to the narrowband SLIC  110  and the wideband SLIC  111  using time division multiplexing (TDM). 
         [0018]    As is known in the art, TDM provides a plurality of time slots which act as time multiplexed channels during which transmissions may be transmitted and received on the bus. Time slots are shown in the bus  104  as TS 1 , TS 2 , TS 3 , . . . . Channels comprised of predetermined time slots for transmitting data, such as the pulse code modulated VoIP data streams, are pre-allocated to different SLICs. For example,  FIG. 1  shows a 4-channel DSP circuit  103 , and each of the SLICs  110  and  111  is capable of handling two channels. The channels are shown as narrowband SLIC channels  1  and  2  and wideband SLIC channels  1  and  2 . narrowband SLIC channels  1  and  2  and wideband SLIC channels  1  and  2  are allocated to the narrowband SLIC  110  and the wideband SLIC  111  respectively, and each of the channels is comprised of pre-allocated time slots. For example, time slots  1 ,  5 ,  9 , etc., are assigned to narrowband SLIC channel  1 , and the DSP circuit  103  transmits data for narrowband SLIC channel  1  in these time slots to the narrowband SLIC  110 . The narrowband SLIC  110  retrieves data in these time slots. Time slots  2 ,  6 ,  10 , etc., are for narrowband SLIC channel  2 , and the DSP circuit  103  transmits data for narrowband SLIC channel  2  in these time slots to the narrowband SLIC  110 . The narrowband SLIC  110  retrieves data in these time slots. Similarly, times slots  3 ,  7 ,  11 , etc are for wideband SLIC channel  1 , and time slots  4 ,  8 ,  12 , etc., are for wideband SLIC channel  2 . The wideband SLIC  111  retrieves data in these time slots for wideband SLIC channels  1  and  2 . Data may be transmitted to the SLICs  110  and  111  from the DSP circuit  103  in the pre-allocated time slots, or data may be transmitted from the SLICs  110  and  111  to the DSP circuit  103  in the pre-allocated time slots. 
         [0019]    To dynamically transmit data to a particular SLIC, the processor  101  determines the type of data in a VoIP data stream and selects a particular SLIC to receive the data depending on the data type. For example, if a VoIP data stream includes narrowband audio data, the processor  101  selects a narrowband SLIC channel and instructs the DSP circuit  103  to place the VoIP data in time slots for the selected channel. If a VoIP data stream includes wideband audio data, the processor  101  selects a wideband SLIC channel and instructs the DSP circuit  103  to place the VoIP data in time slots for the selected channel. Then, the data is transmitted to the corresponding SLIC on the bus  104 . 
         [0020]    The wideband SLIC  111  may be configured to operate in wideband mode to process wideband data or in a narrowband mode to process narrowband data. If narrowband SLIC channels  1  and  2  are full, for example, because the channels are currently being used for two narrowband calls, and a VoIP data stream including narrowband audio data for a third call is received, the processor  101  may instruct the DSP circuit  103  to send the narrowband audio data for the third call to the wideband SLIC  111 . Thus, if the narrowband SLIC  110  is at full capacity, then the wideband SLIC  111  may be used for additional narrowband calls. Note that the narrowband SLIC  110  may not be able to process wideband audio data. Also, if the wideband SLIC  111  is at full capacity, then the narrowband SLIC  110  will be used to process the VoIP data stream. According to an embodiment, whether a wideband SLIC or a narrowband SLIC is to be used for processing a VoIP data stream for a call is dependent on the wideband or narrowband resources available at each party&#39;s MTA. For example, the MTAs of the parties involved in the call pre-negotiate whether to use wideband or narrowband resources for a call before sending the VoIP data stream based on their resource availability at that time. This is described in further detail with respect to  FIG. 3 . 
         [0021]    The narrowband SLIC  110  and the wideband SLIC  111  process narrowband audio data and wideband audio data respectively. This may include performing analog-to-digital conversions or digital-to-analog conversions, sampling at the respective rates (e.g., 16 kHz for wideband and 8 kHz for narrowband), and performing other conventional SLIC functions, such as generating tip and ring line voltages, detecting on-hook, off-hook status of a loop line at the customer premises, etc. 
         [0022]    The narrowband SLIC  110  and the wideband SLIC  111  are connected to ports  120 - 123 . One or more of the ports  120 - 123  may be connected to wiring at the customer premises, such as a loop line at the customer premises. For example, the loop line may include a conventional twisted-pair loop in the customer premises, where customer premises equipment (CPE), such as telephones, fax machines, etc., may be connected. The ports may include RJ-11 ports for connecting to a wired interface. One or more of the ports  120 - 123  may include wireless interfaces, and CPE may interface with these wireless interfaces to send and receive data. 
         [0023]    The narrowband SLIC  110  and the wideband SLIC  111  are connected to the ports  120 - 123  via a bus  114 . The bus  114  is shown as a cloud because in one embodiment the narrowband SLIC  110  and the wideband SLIC  111  may dynamically send data to different ports. For example, the ports  120 - 123  are individually addressable by the narrowband SLIC  110  and the wideband SLIC  111 . The narrowband SLIC  110  and the wideband SLIC  111  may be programmed to send narrowband audio data or wideband audio data to a specific port by addressing the port. Thus, if CPE that is wideband-audio-capable is connected to port  123 , the wideband SLIC  111  may be programmed to send wideband audio data, for example, from wideband SLIC channels  1  or  2  to port  123 . Similarly, the narrowband SLIC  110  may be programmed to send narrowband audio data to a particular port. 
         [0024]    The processor  101  may be connected to the narrowband SLIC  110  and the wideband SLIC  111  to instruct the narrowband SLIC  110  and the wideband SLIC  111  to send data to a particular one of the ports  120 - 123 . Programming the narrowband SLIC  110  and the wideband SLIC  111  may be performed automatically via the processor  101  or may be performed in response to a user selection via the processor  101 . For example, the processor  101  may automatically detect that a call is being made from a wideband-capable telephone connected to port  123  or that a call is being received by a wideband-capable telephone connected to port  123 . Then, the processor  101  instructs the wideband SLIC  111  to send data to the port  123 . Also, a user may configure the SLIC to send data to a particular port. For example, the MTA  100  may be connected to wireless local area network (WLAN) at the customer premises and has its own IP address in the WLAN. The user may login to the MTA  100  via the WLAN and configure MTA settings, including identifying which port is connected to wideband-capable customer premises equipment (CPE). 
         [0025]    In another embodiment, the narrowband SLIC  110  and the wideband SLIC  111  cannot select a port to send data to and receive information from. Instead, each SLIC input/output is connected to a particular port. For example, the narrowband SLIC  110  has 2 channel outputs which may be connected to ports  120  and  121  respectively. 
         [0026]    It will be apparent to one of ordinary skill in the art that the MTA  100  may include more than one narrowband SLIC and more than one wideband SLIC. Furthermore, a DSP circuit may be used that can accommodate more than 4 channels. Furthermore, the narrowband SLIC  110  and the wideband SLIC  111  are shown as 2-channel SLICs by way of example. Also, more than four ports connected to the customer premises may be provided. 
         [0027]      FIG. 2  illustrates a system  200  including the MTA  100 , according to an embodiment. The MTA  100  is shown as an eMTA connected to an IP network  201 , which may include the Internet. The MTA  100  sends data from a customer premises  201  to the IP network  201  and receives data from the IP network  201  for the customer premises  201 . The data may include VoIP data streams. The MTA  100  may exchange information and establish VoIP sessions with MTAs at other customer premises, such as the MTAs  251   a - n  in the customer premises  250   a - n.    
         [0028]    The MTA  100  is connected to CPE  220   a - n  and  230  via ports  120 - 123 . Port  120  is shown as connected to a loop line  210  at the customer premises, and the CPE  220   a - n  are connected to the loop line  210 . For example, the CPE  220 a may include a telephone. The MTA  100  receives a VoIP data stream for a telephone call including narrowband audio data. The DSP circuit  103  sends the narrowband audio data for the call to the narrowband SLIC  110 , and the narrowband SLIC  110  sends the data to the CPE  220   a - n  connected to port  120  via the loop line  210 . 
         [0029]    The ports  120 - 123  in the MTA  100  may also be connected to CPE via other wired or wireless connections. For example, a cordless telephone system comprising a base station  230  and handsets  231   a - c  may be connected to the MTA  100 . For example, the base station  230  is connected to the MTA  100  via port  123 . The base station may be connected to the port  123  via a wireless or wired connection. The handsets  231   a - c  communicate with the base station  230  to make and receive calls. The cordless telephone system may be a wideband-capable device. Thus, the wideband SLIC  111  in the MTA  100  may send data to and receive data from the cordless base station  230 . Although not shown, it will be apparent to one of ordinary skill in the art that other devices and multiple loop lines may be connected to the MTA  100  via the ports. Also, note that only some of the ports  120 - 123  in the MTA  100  from  FIG. 1  are shown in  FIG. 2 . 
         [0030]      FIGS. 3A-B  illustrate a method  300  for dynamically routing wideband and narrowband audio data in an MTA, according to an embodiment. The method  300  is described by way of example and not limitation with respect to one or more of  FIGS. 1 and 2 , and the method  300  may be practiced in other systems and devices. 
         [0031]    The method  300  provides steps for dynamically routing wideband and narrowband audio data in an MTA for two scenarios. One scenario is described with respect to step  301 , whereby the MTA  100  receives signaling to establish a VoIP session for wideband audio data. The signaling is part of a pre-negotiation between the MTAs with regard to resource availability for the VoIP session. The MTA  250   a  shown in  FIG. 2  is requesting to setup a VoIP session with the MTA  100  for a wideband telephone call. Another scenario is described with respect to step  315 , whereby the MTA  100  receives signaling to establish a VoIP session for narrowband audio data. For example, the MTA  251   a  shown in  FIG. 2  is requesting to setup a VoIP session with the MTA  100  for a narrowband telephone call. It will be apparent to one of ordinary skill in the art that many of the steps in the method  300  can be performed if the MTA  100  is attempting to initiate a VoIP call. For example, if a VoIP call is being placed from the MTA  100  to the MTA  251   a , and the MTA  100  has a wideband SLIC channel available, the MTA  100  sends a signaling message to the MTA  251   a  requesting a VoIP session for wideband audio data. Similarly, the MTA may request a VoIP session for narrowband audio data if no wideband SLIC channels are available or if the MTA  251   a  is only capable of handling narrowband audio data. 
         [0032]    At step  301 , the MTA  100  is requested to establish a VoIP session for wideband audio data. For example, the MTA  100  receives a signaling message to establish a VoIP session for a call with another MTA  251   a  shown in  FIG. 2 . Signaling messages include information about the type of codec (which is layer  6 ), the type of client (layer  7 ), and the IP addresses and port (layers  3  and  4 ). For example, the signaling message indicates that the MTA  251   a  has wideband resources available and is capable of sending wideband audio data. Session Initiation Protocol (SIP) may be used for sending/receiving signaling messages. 
         [0033]    At step  302 , the processor  101  determines whether the wideband SLIC  111  is at full capacity. For example, the processor  101  in the MTA  100  keeps track of which resources are available and which resources are unavailable at the MTA  100 . The processor  101  may maintain a table of available and unavailable SLIC channels in the memory  102  shown in  FIG. 1 . The processor  101  determines whether any wideband SLIC channels are available. 
         [0034]    At step  303 , if the wideband SLIC  111  is not at full capacity, the processor  101  sends a message to the MTA  251   a  indicating that wideband resources are available and for establishing a VoIP session with the MTA  251   a  for sending wideband audio data. 
         [0035]    At step  304 , a wideband SLIC is selected at the MTA  100 . This may include selecting a wideband SLIC channel, including pre-allocated timeslots, for sending the VoIP data stream from the DSP circuit  103  to the wideband SLIC  111 . For example, the processor  101  selects the wideband SLIC  111  and wideband SLIC channel  1  for sending the VoIP data stream on the bus  104  to the wideband SLIC  111 . This information may be used to select a SLIC channel for sending data to a SLIC. 
         [0036]    At step  305 , the DSP circuit  103  is instructed to use the selected wideband SLIC channel. For example, the processor  101  selects the wideband SLIC channel  1  that is available, and instructs the DSP circuit  103  to use the wideband SLIC channel  1  to send the VoIP data stream to the wideband SLIC  111 . 
         [0037]    At step  306 , the VoIP data stream including the wideband audio data is received at the MTA  100 . 
         [0038]    At step  307 , the VoIP data stream including the wideband audio data is transmitted on the selected channel to the wideband SLIC. For example, the DSP circuit  103  time division multiplexes the VoIP data stream using the slots for wideband SLIC channel  1  to transmit the VoIP data stream to the wideband SLIC  111 . 
         [0039]    If the processor  101  determines that the wideband SLIC  111  is at full capacity at step  302 , the processor  101  determines whether the narrowband SLIC  110  is at full capacity at step  308 . If the narrowband SLIC  110  is also at full capacity, then no resources are available and the lines are busy (step  309 ). For example, if all the SLIC channels in the MTA  100  are being used, then the processor  101  sends a signaling message to the MTA  251   a  indicating a busy signal (i.e., that no resources are available at this time). If the narrowband SLIC  110  is not at full capacity at step  308 , then the processor  101  sends a signaling message to the MTA  25   1 a indicating that wideband resources are not available and that narrowband resources are available (step  310 ) to establish a VoIP session. 
         [0040]    At step  311 , the processor  101  selects an available narrowband SLIC channel for sending the VoIP data stream to the narrowband SLIC  110 . 
         [0041]    At step  312 , the DSP circuit  103  is instructed to use the selected narrowband SLIC channel. For example, the processor  101  selects the narrowband SLIC channel  1  that is available, and instructs the DSP circuit  103  to use the narrowband SLIC channel  1  to send the VoIP data stream to the narrowband SLIC  110 . 
         [0042]    At step  313 , the VoIP data stream including the narrowband audio data is received at the MTA  100 . 
         [0043]    At step  314 , the VoIP data stream including the narrowband audio data is transmitted on the selected channel to the narrowband SLIC. For example, the DSP circuit  103  time division multiplexes the VoIP data stream using the slots for wideband SLIC channel  1  to transmit the VoIP data stream to the narrowband SLIC  110 . 
         [0044]    Step  315  describes the second scenario, whereby the MTA  100  receives signaling to establish a VoIP session for narrowband audio data. For example, the MTA  251   a  shown in  FIG. 2  is requesting to setup a VoIP session with the MTA  100  for a narrowband telephone call. 
         [0045]    At step  316 , the processor  101  determines whether the narrowband SLIC  110  is at full capacity. If the narrowband SLIC is not at full capacity, then steps  310 - 314  are performed, such as described above. If the narrowband SLIC  110  is at full capacity, then at step  317 , the processor  101  determines whether the wideband SLIC  111  is at full capacity. If the wideband SLIC  111  is also at full capacity, then no resources are available, and a signaling message is sent to the MTA  251   a  indicating that the MTA is busy at step  309 . If the wideband SLIC  111  is not at full capacity, then steps  318 - 321  are performed. 
         [0046]    At step  318 , a wideband SLIC channel is selected. Also, a signaling message is sent to the MTA  251   a  indicating that narrowband resources are available. At step  319 , the processor  101  places the wideband SLIC  111  in narrowband mode for the selected channel. Thus, the wideband SLIC is operable to process narrowband audio data received on the selected channel. 
         [0047]    At step  320 , the MTA receives the VoIP data stream including narrowband audio data. At step  321 , the VoIP data stream including the narrowband audio data is transmitted on the selected channel to the narrowband SLIC  110 . 
         [0048]    One or more of the steps of the method  300  and other steps described herein and software described herein may be implemented as software embedded or stored on a computer readable medium. The steps may be embodied by a computer program, which may exist in a variety of forms both active and inactive. For example, they may exist as software program(s) comprised of program instructions in source code, object code, executable code or other formats for performing some of the steps when executed. Modules include software, such as programs, subroutines, objects, etc. Any of the above may be stored on a computer readable medium, which include storage devices and signals, in compressed or uncompressed form. Examples of suitable computer readable storage devices include conventional computer system RAM (random access memory), ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), and magnetic or optical disks or tapes. Examples of computer readable signals, whether modulated using a carrier or not, are signals that a computer system hosting or running the computer program may be configured to access, including signals downloaded through the Internet or other networks. Concrete examples of the foregoing include distribution of the programs on a CD ROM or via Internet download. In a sense, the Internet itself, as an abstract entity, is a computer readable medium. The same is true of computer networks in general. It is therefore to be understood that those functions enumerated herein may be performed by any electronic device capable of executing the above-described functions. 
         [0049]    While the embodiments have been described with reference to examples, those skilled in the art will be able to make various modifications to the described embodiments without departing from the true spirit and scope. The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. In particular, although the methods have been described by examples, steps of the methods may be performed in different orders than illustrated or simultaneously. Those skilled in the art will recognize that these and other variations are possible within the spirit and scope as defined in the following claims and their equivalents.