DATA MESSAGE WAITING

Abstract: A method for transmitting a data message to a voice/data subscriber unit (114) in a trunked voice/data communication system (100). When the subscriber unit (114) is in a voice mode, the system transmits a paging message regarding the existence of the data message via the voice channel thus, solving the problem of the voice using partly not knowing data is waiting. The system can then transmit the data message via a data channel.

Description: DATA MESSAGE WAITING Background of the Invention This invention pertains to trunked radio systems, wherein certain channels are allocated from time to time for voice traffic, and other channels are allocated from time to time for data messages, and certain subscriber units are arranged to operate in either a voice mode or one of several data modes. Hereinafter, these voice/data subscriber units are referred to as subscriber units. In general, such subscriber units can only communicate on one channel at a time and, consequently, when they are communicating on a voice channel, they are incapable of simultaneously receiving a data message on a data channel. A problem arises with this arrangement whenever the system desires to deliver a data message to a subscriber unit that is in the active voice mode. Current radio systems wait until the subscriber unit terminates the voice session and then attempt to deliver the data message to the subscriber unit on a data channel. There are problems with such an approach. Since the system must hold all data messages for subscriber units in the active voice mode, the system data message through-put is decreased. Further, since all data messages for subscriber units in the active voice mode are delayed by an average holding time, the average data message propagation time is increased. Also, when the subscriber unit operator is communicating on a voice channel, he has no way of knowing that a data message is waiting for him. As a result, often the subscriber unit operator will continue communicating on the voice channel even though a data message is waiting for him. As a result, a high-priority data message may be needlessly delayed, or even lost. Summary of the Invention Accordingly, it is an object of the present invention to provide a trunked voice/data communications system an improved method of transmitting a data message to a voice/data subscriber unit. In one embodiment, the subscriber unit may pre-select operation in either a message-waiting mode or a data pre-empt mode. In the message-waiting mode, the communications system will inform an active voice mode subscriber unit when data messages are waiting to be sent to that subscriber unit. Thereafter, the communications system will, for a limited time interval, hold the message for the subscriber unit and wait for a response from the subscriber unit on a data channel. If the system receives such a response within this time interval, the system will transmit the data message to the subscriber unit on the data channel. This mode allows the subscriber to continue communicating on the voice channel, at least for the limited time interval, and still receive the data message. in the data pre-empt mode, the system will inform an active voice mode subscriber unit that a data message exists and the subscriber unit will automatically cease communicating on the voice channel. The subscriber unit will then automatically operate on a data channel and receive the data message as sent by the system. The message-waiting mode and the pre-empt mode can be selected by the subscriber unit operator in one embodiment, or can be made system-controllable in another embodiment. Brief Description of the Drawings Fig. 1 is a block diagram of the trunked voice/data communication system; Fig. 2 is a flow diagram illustrating the steps of the present invention executed by the fixed-end equipment of Fig. 1; and, Fig. 3 is a flow diagram illustrating the steps of the present invention executed by a voice/data subscriber unit of Fig. 1. Detailed Description of the Drawings Fig. 1 shows a block diagram of a trunked voice/data communication system (100) using the present invention. The centralized or fixed-end equipment embodying the present invention includes a network controller (108) , a voice channel (104B) , and a data channel (104C) . Fig. 1 also depicts a voice/data subscriber unit (114) . The operation of trunked radio communications systems is generally well understood in the art, and hence no additional description will be provided here except where specific description of the system is pertinent to understanding the invention. Fig. 2 illustrates the steps (200) of the present invention as executed by the network controller (108) . The process begins (201) when the controller (108) receives a data message intended for voice/data subscriber unit (114) . The network controller then determines (202) whether the target subscriber unit is presently communicating on a voice channel. If not, the controller transmits the data message (210) to the subscriber unit. If the answer to this determination step (202) is affirmative, the controller sends a paging message (203) to the subscriber unit (114) on the voice channel. This paging message preferably will be non-audible to thereby avoid undue disturbance to the voice communication in progress. For example, the paging message could occupy a subaudible portion of the communication channel (in the art, this typically means the message will take the form of a signal having a frequency less than 300 Hz) . The controller then waits for a brief period of time (204), such as l second. The waiting period serves two purposes. First, this period tends to insure that the subscriber has time to successfully receive and interpret the paging message. Second, upon receipt of the message-waiting message, and if the subscriber unit (114) has previously selected the data pre-empt mode, this waiting period tends to insure that the subscriber unit has adequate time to cease communicating on the voice channel (104B) and commence communicating on the data channel (104C) . After this waiting step (204) , the controller assumes the subscriber unit has received the paging message and, in the case of the pre-empt mode, the controller further assumes that the subscriber unit has acquired the data channel. The controller (108) then determines (204) whether the subscriber unit has previously selected the data pre-empt mode or the message-waiting mode. In a typical embodiment, this determination may be accomplished by storing this information in any convenient memory storage means and, whenever this information is needed, accessing this information. In another embodiment, the paging message from the controller (108) can include an indication of the priority of the data message, or even an instruction that causes the subscriber unit to automatically select one mode or the other. For example, high priority data messages could justify causing the subscriber unit to select the pre-empt mode. If the data pre-empt mode has been selected, the controller transmits the data message (210) to the subscriber unit (114) . If the message-waiting mode has been selected, the controller will wait for at least a time interval (such as 10 minutes) . During this time the controller holds the data message, and waits for the subscriber unit to respond on the data channel. If the subscriber unit (114) responds on the data channel within this time interval, the controller transmits the data message (210) to the subscriber unit (114) . If the subscriber unit fails to respond on the data channel within the time interval, the controller ceases its present attempt to transmit the data message (207). Fig. 3 illustrates the steps (300) of the present invention as executed by the voice/data subscriber unit (114). For purposes of this description, it may be assumed that the subscriber unit is communicating on a voice channel (104B) and concurrently receives a paging message (301) from the network controller (108) as described above in Fig. 2. The subscriber unit now determines (302) whether it has previously selected the data pre-empt mode, or the message-waiting mode, and/or whether one of these modes has been commanded by the controller. If the data pre-empt mode has been selected, the subscriber unit ceases communicating (310) on the voice channel, and begins communicating on the data channel to await the receipt of a data message from the controller (108) . If the message waiting mode has been selected instead, the subscriber unit can optionally inform the operator of the existence of the waiting data message (303) . This can be accomplished, for example, through use of an indicator light. The subscriber unit then continues communicating on the voice channel (104B) until the operator concludes that communication. If the operator ceases communicating (306) on the voice channel within the time interval noted earlier (305) , the subscriber unit can acquire a data channel (307) and transmit a message to the network controller (108) indicating that the subscriber unit is ready to receive the data message. On the other hand, if the operator maintains the voice communication beyond the time interval (305) , the subscriber unit (114) may elect not to respond on the data channel and thereby disregard the paging message. In use, in the message-waiting mode, if the subscriber unit operator is not communicating on a voice channel when the communications system acquires a data message for him, it will deliver it to him automatically on a data channel. On the other hand, if the operator is communicating on a voice channel when the communications system acquires a data message for him, it will inform him of this on the voice channel. The operator, having been so informed, will know that he has exactly 10 minutes to retrieve the data message on the data channel, or else the data message may be lost. On the other hand, in a pre-empt mode (selected either by the subscriber unit operator or the controller) , the operator can be assured of never missing a data message. What is claimed is:

Claims: - 7 - Claims 1. In a trunked voice/data communication system haying at least one voice/data subscriber unit for communicating over a plurality of communication channels, at least some of which are allocated from time to time as voice channels for voice traffic, and at least one of which is allocated from time to time as a data channel for data traffic, a method of transmitting a data message to a particular subscriber unit, comprising at least the following steps: (1) determining whether said subscriber unit is communicating on a voice channel; and, (2) when said subscriber unit is communicating on said voice channel, transmitting a message to said subscriber unit on said voice channel, said message at least containing an indication that said data message exists. 1 - 8 - 2. The method of claim 1 that includes the further step of: (2a) when said subscriber unit is communicating on said voice channel, transmitting a further message to said subscriber unit on said voice channel, said further message at least containing an indication of the priority of said data message. 3. The method of claim 1 that includes the further step of: (3) after the passage of at least a first predetermined time interval, transmitting at least said data message to said subscriber unit on said data channel. 4. The method of claim 1 that includes the further step of: (3) determining whether said subscriber unit is communicating on said data channel. 5. The method of claim 1 that includes the further step of: (3) determining whether said subscriber unit is communicating on said data channel; and, (4) when said subscriber unit is communicating on said data channel, transmitting at least said data message to said subscriber unit on said data channel. 6. The method of claim 1 that includes the further step of: (3) determining whether said subscriber unit is communicating on said data channel; and, (4) after the passage of at least a second predetermined time interval, postponing transmitting said data message to said subscriber unit. - 9 - 7. In a voice/data subscriber unit for communicating in a trunked voice/data communication system having a plurality of communication channels, at least some of which are allocated from time to time as voice channels for voice traffic, and at least one of which is allocated from time to time as a data channel for data traffic, a method of receiving a data message, comprising at least the following step: (1) when said subscriber unit is communicating on a voice channel, receiving a message on said voice channel, said message at least containing an indication that said data message exists. 8. The method of claim 7 that includes the further step of: (la) when said subscriber unit is communicating on a voice channel, receiving a further message on said voice channel, said further message at least containing an indication of the priority of said data message. 9. The method of claim 7 that includes the further step of: (2) receiving at least a portion of said data message on said data channel. 10. The method of claim 7 that includes the further step of: (2) communicating on said voice channel. 11. The method of claim 7 that includes the further steps of: (2) communicating on said voice channel; (3) communicating on said data channel; and, (4) receiving at least a portion of said data message on said data channel. - 11 - 12. In a trunked voice/data communication system having at least one voice/data subscriber unit for communicating over a plurality of communication channels, at least some of which are allocated from time to time as voice channels for voice traffic, and at at least one of which is allocated from time to time as a data channel for data traffic, an arrangement for transmitting a data message to a particular subscriber unit, comprising: (1) determining means for determining whether said subscriber unit is communicating on a voice channel; and, (2) transmitting means responsive to said determining means for transmitting a message to said subscriber unit on said voice channel when said subscriber unit is communicating on said voice channel, said message at least containing an indication that said data message exists. 13. The arrangement of claim 12, wherein said transmitting means is further arranged to transmit a further message to said subscriber unit on said voice channel when said subscriber unit is communicating on said voice channel, said further message at least containing an indication of the priority of said data message. 14. The arrangement of claim 12 wherein said transmitting means is further arranged to transmit at least said data message to said subscriber unit on said data channel after the passage of at least a first predetermined time interval. 15. The arrangement of claim 12 wherein said determining means is further arranged to determine whether said subscriber unit is communicating on said data channel. 16. The arrangement of claim 12 wherein said determining means is further arranged to determine whether said subscriber unit is communicating on said data channel and said transmitting means is further arranged to transmit at least said data message to said subscriber unit on said data channel when said subscriber unit is communicating on said data channel. 17. The arrangement of claim 12 wherein said determining means is further arranged to determine whether said subscriber unit is communicating on said data channel and said transmitting means is further arranged to postpone transmitting said data message to said subscriber unit after the passage of at least a second predetermined time interval. 18. In a voice/data subscriber unit constructed and arranged to communicate in a trunked voice/data communication system having a plurality of communication channels, at least some of which are allocated from time to time as voice channels for voice traffic, and at least one of which is allocated from time to time as a data channel for data traffic, an arrangement for receiving a data message, comprising: (1) determining means for determining whether said subscriber unit is communicating on a voice channel; and, (2) receiving means responsive to said determining means for receiving a message on said voice channel when said subscriber unit is communicating on said voice channel, said message at least containing an indication that said data message exists. 19. The arrangement of claim 18 wherein said receiving means is further arranged to receive a further message on said voice channel when said subscriber unit is communicating on said voice channel, said further message at least containing an indication of the priority of said data message. 20. The arrangement of claim 18 wherein said receiving means is further arranged to receive at least a portion of said data message on said data channel after receiving said message on said voice channel. 21. The arrangement of claim 18 wherein said subscriber unit is further arranged to communicate on said voice channel after said receiving means receives said message on said voice channel. 22. The arrangement of claim 18 wherein said subscriber unit is further arranged to communicate on said voice channel after said receiving means receives said message on said voice channel and said subscriber unit is further arranged to communicate on said data channel after communicating on said voice channel and said receiving means is further arranged to receive at least a portion of said data message on said data channel after said subscriber unit has commenced communicating on said data channel.

Inventors: ABLAY SEWIN FEWSI, BIANCALANA PETER, THRO STUART WELLS, ZDUNEK KENNETH JOHN, ABLAY, SEWIN, FEWSI, BIANCALANA, PETER, THRO, STUART, WELLS, ZDUNEK, KENNETH, JOHN
Applicants: MOTOROLA INC, MOTOROLA, INC.
Application year: 1989
Main classification: H04M11
IPC codes: H04M11, H04W84