Voter arrangement for multiple site PST RF trunking system

• US 5,113,413 A
• Filed: 03/30/1990
• Issued: 05/12/1992
• Est. Priority Date: 06/09/1989
• Status: Expired due to Term

• Current Assignee: Pine Valley Investments, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Ericsson GE Mobile Communications Inc (Telefonaktiebolaget LM Ericsson)
• Inventors: Szczutkowski, Craig, Brown, Thomas A., Derenge, Charles L., Hughes, Houston H. III, Tucker, Marcella M., Teel, Vicki J.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Bocure, Tesfaldet
• Application Number:
  US07/501,940
• Time in Patent Office: 774 Days
• Field of Search: 375/40, 375/3, 375/4, 375/100, 455/57, 455/10, 455/13, 455/133, 455/62, 455/134, 455/135, 455/136
• US Class Current: 375/267
• CPC Class Codes: H04W 4/10 Push-to-Talk [PTT] or Push-On-Call services
• CPC Class Codes: H04W 76/45 for Push-to-Talk [PTT] or Push-to-Talk over cellular [PoC] services
• CPC Class Codes: H04W 84/08 Trunked mobile radio systems

Abstract

A digital voter system for a multiple site digitally trunked RF communications system includes an improved voting arrangement which tests for actual redundancy before removing redundant messages--thereby decreasing retransmission traffic in simulcast and other large coverage area RF trunking systems. Status messages indicating ongoing call reception are generated periodically by each receiver site which receives a given call. The status messages are received by a digital voter, which in a clear voice mode is used to determine (in responses to the status messages) whether an analog voter should maintain a clear voice call.

Claims

1. In a digitally trunked radio frequency communication system of the type including at least one transmitting site, multiple receiving sites for receiving RF call signals associated with a call involving at least one mobile or portable radio transceiver, and a voting apparatus coupled to said transmitting site and to each of said multiple receiving sites, said multiple receiving sites providing received call signals associated with said call to said voting apparatus, a method of operating said system including the following steps:

processing said call signals provided by said multiple receiving sites for retransmission by said transmitting site;

generating digital status messages at said multiple receiving sites indicating whether RF signals associated with an ongoing call continue to be received from said mobile or portable radio transceiver;

substantially concurrently with providing received call signals to said voting apparatus, providing said digital status messages from each of said multiple receiving sites to said voting apparatus; and

terminating processing of said call signals at said voting apparatus if said digital status messages indicate that none of said multiple receiving sites continue to receive signals associated with said call.

2. A system as in claim 1 wherein said digital status message generating step includes the step of periodically generating said digital status messages.

3. A system as in claim 1 further including the steps of:

(i) communicating received signals between a first of said multiple receiving sites and said voting apparatus over a first signal pathway; and

(ii) simultaneously with said first communicating step (i), communicating digital status messages between said first receiving site and said voting apparatus over a second signal pathway which is isolated from said first signal pathway.

4. A system as in claim 1 wherein said digital status messages each comprise a sequence of multiple digital bit values.

5. In a digitally trunked radio frequency communication system of the type including plural receiving sites for receiving transmitted RF signals, and a voting apparatus coupled to said plural receiving sites, said plural receiving sites for receiving an RF transmission and providing responsive received signals to said voting apparatus, said voting apparatus processing said responsive received signals, a method of operating said system comprising the following steps:

receiving an RF transmission with said plural receiving sites and providing responsive received signals to said voting apparatus;

generating digital status messages at said plural receiving sites and communicating said status messages to said voting apparatus, said status messages indicating continued reception of said RF transmission;

applying, at said voting apparatus, a redundant message removal process to status messages provided by said plural receiving sites so as to determine whether any of said plural receiving sites is receiving said transmission; and

terminating processing of said responsive received signals at said voting apparatus if said redundant message removal process fails to yield at least one status message indicating said transmission continues to be received.

6. In a trunked digital radio communications system of the type including plural geographically separated digital radio frequency (RF) transceivers each for receiving digital radio frequency signals transmitted over a common radio frequency channel, an improved digital voting system comprising:

a first digital receiver means for receiving a first digital message responsive to an RF message transmitted over said RF channel;

a second digital receiver means for receiving a second digital message responsive to an RF message transmitted over said RF channel;

message selecting means coupled to said first and second digital receiver means for selecting said first digital message or said second digital message and for echoing the selected digital message to both of said first and second digital receiver means; and

comparison means operatively coupled to said first digital receiver means and connected to receive said echoed selected message, for inhibiting said message selecting means from selecting said first digital message if said first digital message is substantially identical to said echoed selected message.

7. In a trunked digital radio communications system of the type including:

a first radio frequency (RF) receiver disposed at a first geographical location, said first RF receiver receiving RF signals and forwarding responsive signals to a voter; and

a second RF receiver disposed at a second geographical location different from said first location, said second RF receiver receiving RF signals and forwarding responsive signals to said voter,

said voter being connected to receive said responsive signals forwarded by each of said first and second RF receivers, said voter selecting from signals forwarded thereto and discarding redundant versions of said signals,

an improved method of operating said system comprising;

(a) in response to receipt of said RF signals by said first RF receiver, continually generating, with a first signal processor coupled to said first RF receiver, status messages indicating that said first RF receiver is receiving said RF signals;

(b) in response to receipt of said RF signals by said second RF receiver, continually generating, with a second signal processor coupled to said second RF receiver, further status messages indicating that said second RF receiver is receiving said RF signals; and

(c) inhibiting, with said voter, selection of any of said responsive signals if said first and further status messages indicate said first and second RF receivers have both ceased receiving said RF signals.

8. A method as in claim 7 wherein said said generating steps (a) and (b) are performed periodically by said first and second signal processors.

9. A trunked digital radio communications system having an improved voter call maintenance arrangement, said system including:

a first radio frequency (RF) receiver disposed at a first geographical location, said first RF receiver receiving RF signals and communicating signals responsive to said RF signals received thereby to a voter;

first status message generating means operatively coupled to said first RF receiver for continually generating digital status messages indicating whether said first RF receiver is receiving said F signals;

a second RF receiver disposed at a second geographical location different from said first location, said second RF receiver receiving RF signals and communicating signals responsive to said RF signals received thereby to said voter;

second status message generating means operatively coupled to said second RF receiver for continually generating status messages indicating whether said second RF receiver is receiving said RF signals,

said voter being connected to receive said responsive signals communicated thereto by said first and second RF receivers and also connected to receive said status messages, said voter selecting from signals communicated thereto and providing said selected signals to an output thereof, said voter inhibiting said selection and/or ceasing to provide said communicated signals if said status messages indicate said first and second RF receivers have each ceased receiving said RF signals.

10. A system as in claim 9 wherein said first and second status generating means periodically generate said status messages.

11. In a digitally trunked RF communications system of the type including first and second RF receivers each for providing received versions of RF signal messages, an improved voting apparatus including:

message selecting means operatively coupled to said first and second RF receivers, said message selecting means for selecting between a received version of a message provided by said first RF receiver and a received version of a message provided by said second RF receiver and for echoing said selected messages;

a buffer coupled to said message selecting means for temporarily storing echoed messages; and

comparison means, operatively coupled to said buffer and connected to receive messages provided by said first RF receiver, for discarding messages provided by said first RF receiver that are redundant with echoed messages stored in said buffer.

12. A trunked digital radio communications system having an improved voter, said system including:

an RF transmitting station;

a voter coupled to said RF transmitting station for selecting one of plural signals and providing said selected signal to said RF transmitting site for retransmission over an RF channel;

a radio frequency (RF) satellite receiver site geographically distant from said RF transmitting site, said RF satellite receiver site receiving RF signals and communicating a signal responsive to said RF signals received thereby to said voter over a first signal path coupling said RF satellite receiver site to said voter, said voter being capable of selecting said communicated signal as one of said plural signals; and

status message generating means disposed at said RF satellite receiver site for generating digital status messages indicating if said RF satellite receiver site is receiving said RF signals and for providing said digital status messages to said voter over a further signal path isolated from said first signal path at least during the time said RF satellite receiver site is receiving said RF signals,

wherein said voter is capable of selectively terminating voting on said plural signals in response to said digital status messages.