Abstract:
A mobile device with walkie-talkie functionality initiates a half-duplex transmission, which prompts a transmission request to be sent to a server mediating audio transmissions within channels of the network. The server receives the transmission request and determines if the requested channel is currently busy. An access grant or refusal message is sent to the mobile device accordingly. The access grant message may accord rights to a channel to the mobile device until the audio transmission has been sent, at which point a transmission completion message may be sent to the server. The access refusal message may also detail a list of alternately available channels and/or automatically tune the mobile device to one of said alternately available channels.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a channel access arbitration mechanism for walkie-talkie devices. 
       BACKGROUND 
       [0002]    Walkie-talkie devices use a half-duplex multicast system where one user may transmit an audio transmission across a certain channel to any plurality of recipients. This half-duplex transmission is transmitted over a Voice over Internet Protocol (VOIP) network, where voice conversations are routed to their destination over the internet via any series of routers and servers. In the half-duplex transmission, only one user may transmit an audio signal across a channel at any given time. Any plurality of recipients that are tuned into this channel may receive the audio transmission. Therefore, under one scenario, if two users were to initiate an audio transmission at essentially the same time, only the signal which is transmitted first will be multicast, while the second user will have its session ignored. 
         [0003]    Under another scenario, some recipients will respond to the first user who transmits, while others may respond to the second transmitter if those other recipients receive, due to network effects, the transmission of the second user before that of the first user. 
         [0004]    Additionally, two users on different networks may attempt to multicast a signal at the same time. In this case, each network separately identifies who initiated their transmission first. It is therefore possible to have the undesirable situation where multiple audio transmissions are sent across one channel at the same time. 
       SUMMARY OF THE INVENTION 
       [0005]    Accordingly, in the exemplary embodiments of the present invention, a mobile device with walkie-talkie functionality (e.g., a cell phone, a personal digital assistant, a walkie-talkie, a two-way radio, a data acquisition device, etc.) is provided with a channel access arbitration mechanism to streamline the process of multicasting audio transmissions. 
         [0006]    A server system may be employed to mediate audio transmissions within channels of a network. The server system may receive transmission requests from mobile devices wishing to transmit audio signals across a channel. The server may then determine if the requested channel is currently in use and send an access grant or refusal message to the mobile device accordingly. The access grant and refusal messages may allow or deny rights to the requested channel, respectively. Additionally, the refusal message may incorporate a list of alternately available channels for the mobile device to use. The refusal message may also automatically tune the mobile device to an alternately available channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0008]      FIG. 1  shows a first exemplary system for employment of a channel access arbitration mechanism according to an exemplary embodiment of the present invention. 
           [0009]      FIG. 2  shows a first exemplary method for the first system of  FIG. 1 . 
           [0010]      FIG. 3  shows a second exemplary system for employment of a channel access arbitration mechanism according to an exemplary embodiment of the present invention. 
           [0011]      FIG. 4  shows a second exemplary method for the second system of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION  
       [0012]    A method and system are herein described for providing a channel access arbitration mechanism for wireless mobile devices with half-duplex walkie-talkie capabilities (e.g., a cell phone, a personal digital assistant, a walkie-talkie, a two-way radio, a data acquisition device, etc.). The aforementioned arbitration system seeks to prevent a condition where multiple mobile devices simultaneously transmit an audio transmission over a particular channel at the same time. Additionally, the present invention allows mobile devices the option to be able to communicate over a walkie-talkie channel without having to wait for a particular channel to become available. 
         [0013]    Walkie-talkie devices such as those noted above may operate as Voice over Internet Protocol (VOIP) devices such that the routing of the audio transmissions from sender to recipient(s) is done via the use of one or more servers within the network. The present invention seeks to take advantage of these servers to be able to create a central arbitration system for the regulation of audio transmissions sent across any particular channel. 
         [0014]    The present invention may be further understood with reference to the following description and the appended drawings. An exemplary embodiment of the present invention describes a system including a plurality of mobile devices involved in a half-duplex communication transmission over a particular channel 
         [0015]      FIG. 1  shows a first system according to an exemplary embodiment of the present invention. Initially, the mobile device  10  and the mobile device  20  are both prepared to transmit audio signals over the same channel. Those skilled in the art will understand that the selection of the channel may be done via any conventional means. The user of the mobile device  10  is first to engage the “Push to Talk” button and therefore, the first to send a transmission request  15  to a server  30 . 
         [0016]    When the server  30  receives the transmission request  15 , it checks to see if there is any current activity on the channel in question. In this case, the channel to be used is free and, as such, the server sends a grant message  19  to the mobile device  10 . The grant message  19  accords mobile device  10  the rights to the channel in question. Accordingly, as long as the mobile device  10  continues to press the “Push to Talk” button, an audio signal  11  may be transmitted across the channel to a recipient, mobile device  40 , who is tuned to the channel in question. Those skilled in the art will understand that the audio signal  11  may be transmitted to any plurality of recipients that are tuned to the channel in question. Once the mobile device  10  releases the “Push to Talk” button, a transmission complete message  16  is sent to the server  30 . The transmission complete message  16  notifies the server  30  that the channel is once again available for use. 
         [0017]    When the mobile device  20  engages the “Push to Talk” button, a transmission request  25  is sent to the server  30 . In this case, since the mobile device  20  is second to send a request to the server  30 , the mobile device  10  receives priority. Therefore, the server  30  transmits a refusal message  29  to the mobile device  20 . The refusal message  29  indicates to the mobile device  20  that the indicated channel is not currently available. The refusal message  29  also inquires of the mobile device  20  if the mobile device  20  would like to wait for the channel to become available, as will be discussed with respect to  FIG. 2  below. 
         [0018]      FIG. 2  shows a first exemplary method for the first system of  FIG. 1 . The method of  FIG. 2  will be described with reference to the system of  FIG. 1 . In step  200 , the mobile device  10  may select the “Push to Talk” button. In step  201 , a transmission request  15  may be sent to the server  30 . The transmission request  15  may include information regarding the transmission including the channel being utilized, a timestamp indicating when the transmission was initiated, IP address of the mobile device  10 , etc. When the server  30  receives this data from the mobile device  10 , a check is performed to determine if the requested channel is free (step  202 ). 
         [0019]    If it is determined that the channel is free in step  202 , a grant message is sent to the mobile device  10  (step  203 ). In step  204 , the server  30  marks the requested channel as busy so that no other mobile device may transmit any audio transmissions at the same time as the mobile device  10 . In step  205 , the mobile device  10  may send the audio transmission  11  to any plurality of recipients tuned into the channel in question. Once the audio transmission is complete and the mobile device  10  has released the “Push to Talk” button, a transmission complete message  16  may be sent to the server  30  to indicate that the requested channel is now free (step  206 ). Alternatively, the server  30  may monitor the channel to make this determination. The server  30  may then mark the channel as free in step  207  and the process may be ended. 
         [0020]    If it is determined that the channel is not free in step  202 , a refusal message is sent to the mobile device  10  in step  208 . At this point, the mobile device  10  is prompted to request if the mobile device  10  would like to wait for the requested channel to be free (step  209 ). If the mobile device  10  decides to wait, it is placed in line and receives priority over the channel once the current transmission is complete. The process is looped back to step  201  and, as soon as the channel is free, a grant message is sent to the mobile device  10  and the method goes through steps  201 - 207  as mentioned above. 
         [0021]    If, in step  209 , the mobile device  10  decides not to wait for the requested channel to be free, the process is ended. If, at a later time, the mobile device  10  decides to again attempt to transmit an audio signal across this or any other channel, the mobile device  10  will now need to go through the entire method of  FIG. 2  again. 
         [0022]      FIG. 3  shows a second exemplary system for employment of a channel access arbitration mechanism according to an exemplary embodiment of the present invention. This system employs the same overall structure as that of  FIG. 1 . However, in this system, when the mobile device  20  sends the transmission request  25  to the server  30  at a time when the channel is in use by the mobile device  10 , the server  30  does not return a refusal message  29 . Rather, the server  30  allows the mobile device  20  to be able to transmit the audio signal via a different channel. As such, once the server  30  receives the transmission request  25  from the mobile device  20 , the server  30  checks to see if the requested channel is free. Once the server  30  determines that the requested channel is not free, it performs a scan to determine which channels are free. A redirect message  26  is then compiled and provides a list of alternatively available channels that may be utilized for the transmission The redirect message  26  is then sent to the mobile device  20  and indicates to the mobile device  20  that the requested channel is not free, providing a list of alternatively usable channels. 
         [0023]    Those skilled in the art will understand that the list of alternatively available channels can be sought in several ways. For example, the server  30  may track activity across all channels within a given time frame and compile a list in order of least activity. As another means, the server  30  may track the channels recently used by the mobile device  20  and compile a list of available channels from within that scope. Those skilled in the art will understand that the number of channels provided in the redirect message  26  may range anywhere from one channel to any plurality of channels, as may be determined and adjusted by the user of the mobile device  20 . 
         [0024]    The redirect message  26  may be sent to other selected recipients as well, as shown in  FIG. 4 . This may allow any intended recipients of the mobile device  20 &#39;s audio signal to all tune to the available channel. Upon receipt of the redirect message  26 , the mobile device  20  may request that the redirect message  26  also be transmitted to a selected recipient(s). This request may be sent via a number of methods (e.g., the user interface of the mobile device  20  may display a prompt to request if forwarding should be done, the mobile device  20  may establish its settings to automatically forward the redirect message  26  to a certain predefined list of recipients, the mobile device  20  may manually forward the redirect message  26  to a list of recipients, etc.) 
         [0025]    The redirect message  26  may enable the mobile device  20  to be able to transmit the audio transmission to the same recipients without having to wait for the requested channel to become available. Those skilled in the art will understand that, in addition to displaying a list of alternate channels, the redirect message may also automatically tune the receiving mobile device to an available channel. The user of said mobile device may selectively modify the above noted function (i.e., so that the device may be tuned to a new channel automatically, upon initiation by the user of said mobile device, etc.). 
         [0026]      FIG. 4  shows a second exemplary method for the second system of  FIG. 3 . The method of  FIG. 4  will be described with reference to the system of  FIG. 3 . In step  400 , the mobile device  20  may select the “Push to Talk” button. In step  401 , a transmission request  25  may be sent to the server  30 . The transmission request  25  may include information regarding the transmission including the channel intended to be utilized, a timestamp indicating when the transmission was initiated, details regarding the mobile device  20 , etc. When the server  30  receives this data from the mobile device  20 , a check is performed to determine if the requested channel is free (step  402 ). 
         [0027]    If it is determined that the channel is free in step  402 , a grant message is sent to the mobile device  20  (step  403 ). In step  404 , the server  30  marks the requested channel as busy so that no other mobile device may transmit any audio transmissions at the same time as the mobile device  20 . In step  405 , the mobile device  20  may send the audio transmission  11 . Once the “Push to Talk” button is released, a transmission complete message  16  is then sent to the server  30  in step  406  and the server  30  consequently marks the requested channel as free in step  407  before the process is ended. 
         [0028]    If it is determined that the channel is not free in step  402 , the server  30  scans to determine which channels are available. Once the list of alternate available channel(s) has been compiled (step  408 ), the server  30  sends a redirect message  26  to the mobile device  20  (step  409 ). At this point, the mobile device  20  displays a prompt asking if the mobile device  20  would like to place the audio transmission on the alternate channel (step  410 ). 
         [0029]    If the mobile device  20  decides not to place the audio transmission on the alternate channel, the process is ended. If the mobile device  20  does decide to place the audio transmission on the alternate channel, the process moves to step  411  where the redirect channel message is sent to the intended recipient(s) as described with respect to  FIG. 3  above. The alternate channel is then marked as busy (step  404 ). The audio transmission  11  is then sent, the alternate channel marked as free, and the process ended (step  405 - 407 ). 
         [0030]    Those skilled in the art will understand that the described exemplary embodiments of the present invention may be altered without departing from the spirit or scope of the invention. Thus, it is to be understood that these embodiments have been described in an exemplary manner and are not intended to limit the scope of the invention which is intended to cover all modifications and variations of this invention that come within the scope of the appended claims and their equivalents.