Abstract:
Disclosed is a stereo mobile terminal including an RF section for receiving or transmitting stereo speech data during a voice call; a demultiplexer for demultiplexing the received stereo speech data into a plurality of speech data and outputting the plurality of speech data; an audio codec for converting the plurality of speech data into a plurality of speech signals to output the speech signals to a plurality of speakers and converting a plurality of speech signals inputted from a plurality of microphones into a plurality of speech data and outputting the plurality of speech data; a multiplexer for multiplexing the plurality of speech data outputted from the audio codec to output the same as stereo speech data; and a control section for controlling operations of the mobile terminal to perform voice communication with a caller&#39;s terminal according to a user&#39;s demand.

Description:
PRIORITY  
       [0001]     This application claims priority to an application entitled “Stereo Terminal and Method for Voice Call Using Stereo Terminal” filed with the Korean Intellectual Property Office on Oct. 8, 2004 and assigned Serial No. 2004-80630, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a mobile communication terminal, and more particularly to a mobile terminal having the capability of providing stereo voice calls.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, mobile terminals use monophonic (mono) sound for voice calls, sometimes with video. In mono mode, speech signals are received and transferred in monotone over a single channel. Mobile terminals performing voice calls in mono mode are called “mono mobile terminals.” 
         [0006]      FIG. 1  is a block diagram of a conventional mono terminal that performs control operations for a voice call with a single-channel speech signal in mono mode. During a voice call, a control unit  11  controls overall operations of the mono terminal to output mono speech data received from a caller&#39;s terminal as a speech signal, and also converts speech signals input through a microphone  17  into mono speech data to be sent to the caller&#39;s terminal. An RF unit  12  receives and transmits mono speech data under the control of the control unit  11 . An audio codec  13 , including a decoder  14  and an encoder  15 , processes speech signals and converts mono speech data received through the RF unit  12  into a speech signal and outputs the speech signal. In addition, the audio codec  13  converts input speech signals into mono speech data and outputs the mono speech data. To be specific, the encoder  15  converts speech signals input through the microphone  17  into mono speech data and outputs the mono speech data to the control unit  11 , while the decoder  14  converts mono speech data transferred from the control unit  11  into a speech signal and outputs the speech signal through a speaker  16 .  
         [0007]     Most conventional mobile terminals were designed to be monophonic, enabling voice calls with less data because of the narrow transmission bandwidths of early wireless networks.  
         [0008]      FIG. 2  is a schematic view illustrating a conventional system for voice communication between mono terminals. Referring to  FIG. 2 , a caller&#39;s mono terminal  10  receives and transmits mono speech data from and to a recipient&#39;s mono terminal  20  via the wireless network  50  to perform a voice call. Simple voice transfer can be achieved by the transmission of mono speech data and single-channel mono speech signals. However, mono terminals cannot sufficiently transfer vivid stereo speech sounds generated at the place of call.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a stereo mobile terminal capable of performing a vivid stereo voice call or video call with a plurality of speech signals and a method for performing a voice call using the stereo mobile terminal.  
         [0010]     Another object of the present invention is to provide a stereo mobile terminal capable of performing a voice call even with a mono mobile terminal and a method for performing a voice call between a stereo mobile terminal and a mono mobile terminal.  
         [0011]     In accordance with one aspect of the present invention for accomplishing the above objects, there is provided a stereo mobile terminal including an RF section for receiving or transmitting stereo speech data during a voice call; a demultiplexer for demultiplexing the received stereo speech data into a plurality of speech data and outputting the plurality of speech data; an audio codec for converting the plurality of speech data into a plurality of speech signals to output the speech signals to a plurality of speakers and converting a plurality of speech signals input from a plurality of microphones into a plurality of speech data and output the plurality of speech data; a multiplexer for multiplexing the plurality of speech data output from the audio codec to output the same as stereo speech data; and a control section for controlling operations of the mobile terminal to perform voice communication with a caller&#39;s terminal according to a user&#39;s demand.  
         [0012]     In accordance with another aspect of the present invention, there is provided a method for performing a voice call between stereo mobile terminals, including when a caller&#39;s stereo terminal inputs a demand for a voice call to a recipient&#39;s stereo terminal, connecting a voice call to the recipient&#39;s stereo terminal; inputting a plurality of speech signals through a plurality of microphones to perform the voice call to the recipient&#39;s stereo terminal; converting the input speech signals into a plurality of speech data and multiplexing the plurality of speech data to generate stereo speech data; and sending the generated stereo speech data to the recipient&#39;s stereo terminal.  
         [0013]     In accordance with still another aspect of the present invention, there is provided a method for performing a voice call to a mono mobile terminal from a stereo mobile terminal, including when the stereo mobile terminal inputs a demand for a voice call to the mono mobile terminal, connecting a voice call to the mono mobile terminal; inputting a plurality of speech signals through a plurality of microphones to perform the voice call to the mono mobile terminal and mixing the speech signals into a single speech signal; and converting the single speech signal into mono speech data and sending the mono speech data to the mono mobile terminal.  
         [0014]     In accordance with still another aspect of the present invention, there is provided a method for performing a voice call to a stereo mobile terminal from a mono mobile terminal, including when the mono mobile terminal inputs a demand for a voice call to the stereo mobile terminal, connecting a voice call to the stereo mobile terminal; inputting a speech signal through a single microphone to perform the voice call to the stereo mobile terminal to generate mono speech data; and sending the mono speech data to the stereo mobile terminal to be output as a single speech signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0016]      FIG. 1  is a block diagram of a conventional mono mobile terminal;  
         [0017]      FIG. 2  is a schematic view illustrating a conventional system for voice communication between mono mobile terminals;  
         [0018]      FIG. 3  is a block diagram of a stereo mobile terminal according to an embodiment of the present invention;  
         [0019]      FIG. 4  is a schematic view illustrating a system for voice communication between stereo mobile terminals according to an embodiment of the present invention;  
         [0020]      FIG. 5  is a flow chart illustrating a process of performing a voice call between stereo mobile terminals according to an embodiment of the present invention;  
         [0021]      FIG. 6  is a schematic view illustrating a system for voice communication between a stereo mobile terminal and a mono mobile terminal according to an embodiment of the present invention;  
         [0022]      FIG. 7  is a flow chart showing a process of performing a voice call between a stereo mobile terminal and a mono mobile terminal according to a first embodiment of the present invention;  
         [0023]      FIG. 8  is a flow chart showing a process of performing a voice call between a stereo mobile terminal and a mono mobile terminal according to a second embodiment of the present invention; and  
         [0024]      FIG. 9  is a flow chart showing a process of performing a voice call between a stereo mobile terminal and a mono mobile terminal according to a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]     Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear.  
         [0026]      FIG. 3  is a block diagram of a stereo mobile terminal according to the present invention. The stereo mobile terminal includes a control unit  110 , an RF unit  120 , a demultiplexer  130 , a multiplexer  140 , an audio codec  150 , a first speaker  162 , a second speaker  164 , a first microphone  172  and a second microphone  174 .  
         [0027]     The control unit  110  controls operations to perform a stereo voice call using a plurality of speech signals. As used herein, stereo voice call refers to a type of telephone call using a plurality of speech signals with different phases. Under the control of the control unit  110 , stereo speech data received from a caller&#39;s terminal are output as a plurality of speech signals. Speech signals input through the microphones are converted into stereo speech data to be sent to the caller&#39;s terminal. The RF unit  120  receives or transmits stereo speech data under the control of the control unit  110 . When stereo speech data multiplexed from a plurality of speech data is received, the demultiplexer  130  demultiplexes the received stereo speech data and outputs a plurality of speech data, which is demultiplexed. When a plurality of speech data are received, the multiplexer  140  multiplexes the received speech data and outputs the single stereo speech data which is multiplexed.  
         [0028]     The audio codec  150  includes a plurality of decoders and encoders for processing a plurality of speech signals. The decoders convert the plurality of speech data output from the demultiplexer  130  into speech signals that will be output through the speakers. The encoders convert speech signals input from the plurality of microphones into a plurality of speech data that will be output to the multiplexer  140 .  
         [0029]     In preferred embodiments of the present invention, a stereo mobile terminal is capable of performing a voice call using two speech signals (for example, a left-channel speech signal and a right-channel speech signal). When two (left-channel and right-channel) speech signals are used, a first encoder  156  converts speech signals input from the first microphone  172  into left-channel speech data and outputs the left-channel speech data, while a second encoder  158  converts speech signals input from the second microphone  174  into right-channel speech data and outputs the right-channel speech data.  
         [0030]     The first and second microphones  172  and  174  for left and right channels, respectively, can be located at different positions (for example, a left side and a right side) of the stereo mobile terminal. In stereo, speech signals input to the two microphones have different phases. The multiplexer  140  receives left-channel speech data and right-channel speech data from the first encoder  156  and the second encoder  158 , respectively. The multiplexer  140  multiplexes the left-channel and right-channel speech data and outputs stereo speech data. The demultiplexer  130  demultiplexes the stereo speech data into left-channel speech data and right-channel speech data to output the two speech data. The first decoder  152  converts the left-channel speech data into a speech signal and outputs it to the first (left-channel) speaker  162 . The second decoder  154  converts the right-channel speech data into a speech signal and outputs it to the second (right-channel) speaker  164 . The two speakers  162  and  164  for left and right channels, respectively, can be located at different positions (for example, a left side and a right side) of the stereo mobile terminal.  
         [0031]     In stereo, speech signals output from the two speakers have slightly different phases. For example, the left-channel speaker  162  has a higher output level for sound produced on the left side. The right-channel speaker  164  has a higher output for sound produced on the right side. The stereo mobile terminal according to an embodiment of the present invention simultaneously outputs two speech signals with different phases through the left and right speakers, thereby transferring vivid and authentic stereo sound.  
         [0032]      FIG. 4  is a block diagram of a system for voice communication between stereo mobile terminals according to an embodiment of the present invention.  
         [0033]     Referring to  FIG. 4 , the wireless network  50  has a much broader bandwidth than early wireless networks to enable large-volume data transmission. The wireless network  50  transfers stereo speech data from a caller&#39;s stereo terminal  100  to a recipient&#39;s stereo terminal  200 .  
         [0034]     A server  55  stores stereo support information of each terminal to indicate whether a terminal is monophonic or stereophonic. When requested, the server  55  provides stereo support information of a pertinent terminal.  
         [0035]     When the caller&#39;s stereo terminal  100  inputs a demand for a voice call to a specific recipient&#39;s terminal, it can receive stereo support information of the recipient&#39;s terminal from the server  55  and confirm that the recipient&#39;s terminal is stereophonic. Then the stereo terminal  100  generates stereo speech data and sends the stereo speech data to the recipient&#39;s terminal. Since the stereo speech data includes data of the plurality of speech signals, it is greater in size than mono speech data for a single speech signal.  
         [0036]     The recipient&#39;s stereo terminal  200  receives stereo speech data from the caller&#39;s stereo terminal  100  through the wireless network  50  and outputs a plurality of speech signals corresponding to the received stereo speech data through the plurality of speakers.  
         [0037]     Hereinafter, a process of performing a voice call between the caller&#39;s stereo terminal  100  and the recipient&#39;s stereo terminal  200  will be explained in more detail.  
         [0038]      FIG. 5  is a flow chart showing the process of performing a voice call between two stereo mobile terminals according to an embodiment of the present invention. Referring to  FIGS. 4 and 5 , the caller having the stereo terminal  100  can input a demand for a voice call to a specific recipient&#39;s terminal at step  502 . Then the stereo terminal  100  sends a request for stereo support information of the recipient&#39;s terminal to the server  55  through the wireless network  50  at step  504 . The server  55  determines whether the recipient&#39;s terminal support a stereo mode at step  506  and sends the stereo support information of the recipient&#39;s terminal to the caller&#39;s stereo terminal  100  at step  508 . The stereo terminal  100  receives the stereo support information from the server  55  and confirms that the recipient&#39;s terminal is stereophonic at step  510 . The caller&#39;s stereo terminal  100  connects a voice call to the recipient&#39;s stereo terminal  200  at step  512 .  
         [0039]     When the voice call to the recipient&#39;s stereo terminal  200  is connected, the caller using the stereo terminal  100  inputs speech signals through the plurality of microphones in step  514 . At step  516 , the stereo terminal  100  converts the input speech signals into its respective speech data and multiplexes the multiple speech data to generate single stereo speech data. At step  518 , the caller&#39;s stereo terminal  100  sends the stereo speech data to the recipient&#39;s stereo terminal  200  via the wireless network  50 .  
         [0040]     At step  520 , the recipient&#39;s stereo terminal  200  receives the stereo speech data from the caller&#39;s stereo terminal  100 . At step  522 , the recipient&#39;s stereo terminal  200  outputs a plurality of speech signals corresponding to the received stereo speech data through the plurality of speakers. In further detail, the recipient&#39;s stereo terminal  200  demultiplexes the received stereo speech data into a plurality of speech data and converts the plurality of speech data into corresponding speech signal or sound. The speech signals are then output through the respective speakers.  
         [0041]     As compared to a voice call between mono mobile terminals, a voice call between stereo mobile terminals using a plurality of speech signals can transfer more vivid and authentic sound.  
         [0042]     Since mono mobile terminals process mono speech data only, the stereo voice call as explained above cannot be performed between a mono mobile terminal and a stereo mobile terminal. The present invention provides a system and method for performing a voice call between a stereo mobile terminal and a mono mobile terminal, in addition to a system and method for performing a voice call between two stereo mobile terminals.  
         [0043]      FIG. 6  is a schematic view illustrating a system for voice communication between a stereo mobile terminal and a mono mobile terminal according to the present invention. Referring to  FIG. 6 , when the caller&#39;s stereo terminal  100  inputs a demand for a voice call to a specific recipient&#39;s terminal, it can receive stereo support information of the recipient&#39;s terminal from the server  55  and confirm that the recipient&#39;s terminal is monophonic. The stereo terminal  100  mixes speech data corresponding to a plurality of speech signals to generate mono speech data and sends the mono speech data to the recipient&#39;s mono terminal  300 . The generated mono speech data has a volume similar to general mono speech data. The recipient&#39;s mono terminal  300  receives the mono speech data from the caller&#39;s stereo terminal  100  via the wireless network  50  and outputs a speech signal corresponding to the received mono speech data through a single speaker.  
         [0044]     Hereinafter, a process of performing a voice call between the stereo mobile terminal  100  and the mono mobile terminal  300  will be explained in more detail. There are at least three embodiments of a voice call between the stereo mobile terminal  100  and the mono mobile terminal  300 .  
         [0045]     In accordance with the first embodiment, the stereo mobile terminal  100  makes a voice call to the mono mobile terminal  300  using mono speech data.  FIG. 7  is a flow chart showing a process of performing a voice call between the stereo mobile terminal  100  and the mono mobile terminal  300  according to the first embodiment. Referring to  FIGS. 6 and 7 , the caller having the stereo terminal  100  can input a demand for a voice call to a specific recipient&#39;s terminal at step  702 . The stereo terminal  100  sends a request for stereo support information of the recipient&#39;s terminal to the server  55  through the wireless network  50  at step  704 .  
         [0046]     The server  55  determines whether the recipient&#39;s terminal support a stereo mode at step  706  and sends the stereo support information of the recipient&#39;s terminal to the caller&#39;s stereo terminal  100  at step  708 .  
         [0047]     The stereo terminal  100  receives the stereo support information from the server  55  and confirms that the recipient&#39;s terminal is monophonic at step  710 . The caller&#39;s stereo terminal  100  connects a voice call to the recipient&#39;s mono terminal  300  at step  712 .  
         [0048]     When the voice call to the recipient&#39;s mono terminal  300  is connected, the caller&#39;s stereo terminal  100  accepts, as input, speech signals from the caller through the plurality of microphones in step  714 . At step  716 , the stereo terminal  100  converts the speech signals into their respective speech data and mixes the speech data to generate mono stereo speech data. At step  718 , the caller&#39;s stereo terminal  100  sends the mono speech data to the recipient&#39;s mono terminal  300  via the wireless network  50 .  
         [0049]     At step  720 , the recipient&#39;s mono terminal  300  receives the mono speech data from the caller&#39;s stereo terminal  100 . At step  722 , the recipient&#39;s mono terminal  300  outputs a single speech signal corresponding to the received mono speech data through a single speaker.  
         [0050]     As explained above, the stereo terminal  100  generates mono speech data, instead of stereo speech data, to make a voice call to the mono terminal  300 .  
         [0051]     In accordance with the second embodiment, the server  55  converts stereo speech data sent from the stereo terminal  100  into mono speech data to enable a voice call between the stereo terminal  100  and the mono terminal  300 .  FIG. 8  is a flow chart showing a process of performing a voice call between the stereo terminal  100  and the mono terminal  300  according to the second embodiment.  
         [0052]     Referring to  FIGS. 6 and 8 , the caller having the stereo terminal  100  can input a demand for a voice call to a specific recipient&#39;s terminal at step  802 . The stereo terminal  100  connects a voice call to the recipient&#39;s mono terminal  300  at step  804 .  
         [0053]     When the voice call to the recipient&#39;s mono terminal  300  is connected, the caller&#39;s stereo terminal  100  proceeds with step  806  to convert speech signals input through the plurality of microphones into respective speech data, and multiplexes the speech data to generate stereo speech data. At step  808 , the stereo terminal  100  sends the stereo speech data to the server  55  via the wireless network  50 .  
         [0054]     At step  810 , the server  55  obtains a plurality of speech signals from the stereo speech data received from the stereo terminal  100 . To do so, the server  55  demultiplexes the stereo speech data to obtain a plurality of speech data, and acquires a plurality of speech signals from the speech data through digital-to-analog conversion. At step  812 , the server  55  mixes the plurality of speech signals into a single speech signal and generates mono speech data from the speech signal. At step  814 , the server  55  sends the mono speech data to the recipient&#39;s mono terminal  300 .  
         [0055]     At step  816 , the recipient&#39;s mono terminal  300  receives the mono speech data from the server  55 . At step  818 , the recipient&#39;s mono terminal  200  outputs a single speech signal corresponding to the received mono speech data through a single speaker.  
         [0056]     In the second embodiment, the server  55  converts stereo speech data sent from the stereo terminal  100  into mono speech data to enable a voice call between the stereo terminal  100  and the mono terminal  300 .  
         [0057]     The third embodiment enables a voice call to the stereo terminal  100  from the mono terminal  300 .  FIG. 9  is a flow chart showing a process of performing a voice call between the stereo terminal  100  and the mono terminal  300  according to the third embodiment.  
         [0058]     The process in  FIG. 9  is performed when the mono terminal  300  initiates an outgoing call to the stereo terminal  100 . Referring to  FIGS. 6 and 9 , the caller having the mono terminal  300  can input a demand for a voice call to the stereo terminal at step  902 . Then the mono terminal  300  connects a voice call to the stereo terminal  100  at step  904 .  
         [0059]     When the voice call to the recipient&#39;s stereo terminal  100  is connected, the mono terminal  300  proceeds with step  906  to generate mono speech data from a single speech signal inputted through a microphone. At step  908 , the mono terminal  300  sends the mono speech data to the stereo terminal  100  via the wireless network  50 .  
         [0060]     At step  910 , the stereo terminal  100  receives the mono speech data from the mono terminal  300 . At step  912 , the stereo terminal  100  outputs a single speech signal corresponding to the received mono speech data through the plurality of speakers.  
         [0061]     Although the stereo terminal  100  can convert stereo speech data into mono speech data, it cannot convert mono speech data into stereo speech data. When mono speech data is received, the stereo terminal  100  outputs a single speech signal converted from the mono speech data.  
         [0062]     As compared to mono mobile terminals, stereo mobile terminals using a plurality of speech signals during a voice call have superior sound quality and thereby enhance user satisfaction. Furthermore, stereo mobile terminals can improve sound source separation using a plurality of speech signals during a voice call and transfer vivid and authentic stereo speech sounds. The present invention is applicable to a voice call between a stereo mobile terminal and a mono mobile terminal, as well as a voice call between stereo mobile terminals.  
         [0063]     Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims, including the full scope of equivalents thereof.