Simulcast group determination of best signal by master site

• US 5,448,758 A
• Filed: 02/26/1993
• Issued: 09/05/1995
• Est. Priority Date: 02/26/1993
• Status: Expired due to Term

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Grube, Gary W., Shaughnessy, Mark L., Ng, Richard
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): TO, DORIS HA
• Application Number:
  US08/023,982
• Time in Patent Office: 921 Days
• Field of Search: 455/51.2, 455/69, 455/67.1, 455/54.1, 455/53.1, 455/54.2, 455/33.1, 455/33.4, 455/51.1, 455/56.1, 375/107, 375/109, 379/58, 379/60
• US Class Current: 455/503
• CPC Class Codes: H04B 17/20 of receivers
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• 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

Processing of dispatch calls in a simulcast multi-site communication system begins when a source communication unit transmits a message to one or more network receivers. The received signals are analyzed immediately at the received sites for signal quality. Each of the signals are time stamped to identify when they where received. The received signals are transported with their time stamp and signal quality metric to each of the other sites via a digital communication network connecting the sites. A master transmitter site determines the receiver source with the best quality signal as indicated by the signal quality metric. The master transmitter then transports the chosen best quality signal to each of the other sites via a digital communication network. Each transmitter site performs a transmit operation by storing the chosen best quality signal until it is time to transmit the signal in phase with all the other transmitter sites in a simulcast manner. The time stamp allows a time in the future to be chosen to accommodate the worst case expected transport delay through the digital network.

Claims

1. In a simulcast communication system that includes a plurality of sites, a time reference, at least two transmitters operable within the plurality of sites, and a plurality of communication units operable within the plurality of sites, wherein each site of the plurality of sites includes at least one receiver and receiver processing means for processing information and for transporting information to a digital communication network, wherein each of the at least two transmitters includes transmitter processing means for processing information and for receiving information from the digital communication network, and wherein the plurality of sites are operably linked together by the digital communication network, a method for a master transmitter, wherein the master transmitter is one of the at least two transmitters to determine signal quality of a received signal and transmitting by the at least two transmitters, in substantial concurrence with each of the at least two transmitters, the received signal with a highest signal quality, the method comprising the steps of:

a) receiving, by a receiver in at least two sites, a signal from a communication unit;

b) transporting, by each receiver processing means in the at least two sites, the signal to the at least two transmitters to produce at least two received signals;

c) comparing, by a master transmitter processing means the at least two received signals to determine a highest quality signal;

d) transporting, by the master transmitter, the highest quality signal to the at least two transmitters; and

e) transmitting, in phase, the highest quality signal by the at least two transmitters to the plurality of communication units.

2. In the method of claim 1 step (e) further comprises:

1) determining, by the master transmitter, a launch time of the highest quality signal;

2) time stamping, by the master transmitter, the highest quality signal with the launch time; and

3) transmitting in phase, the highest quality signal at the launch time by the at least two transmitters.

3. In the method of claim 1, wherein the method of comparison to determine the highest quality signal of step (c) further comprises analyzing signal strength of the at least two received signals.

4. In the method of claim 1, wherein the method of comparison to determine the highest quality signal of step (c) further comprises analyzing signal to noise ratio of the at least two received signals.

5. In the method of claim 1, wherein the method of comparison to determine the highest quality signal of step (c) further comprises analyzing bit error rate of the at least two received signals.

6. In a simulcast communication system that includes a plurality of sites, a time reference, at least two transmitters, operable within the plurality of sites, and a plurality of communication units, operable within the plurality of sites, wherein each site of the plurality of sites includes at least one receiver and receiver processing means for processing information and for transporting information to a digital communication network, wherein each of the at least two transmitters includes transmitter processing means for processing information and for receiving information from the digital communication network, and wherein the plurality of sites are operably linked together by the digital communication network, a method for a master transmitter, wherein the master transmitter is one of the at least two transmitters to determine signal quality of a received signal and transmitting by the at least two transmitters, in substantial concurrence with each of the at least two transmitters, the received signal with a highest signal quality, the method comprising the steps of:

a) receiving, by a receiver in at least two sites, a signal from a communication unit of the plurality of communication units;

b) determining a signal quality metric for the signal by the receiver processing means of each said receiver in the at least two sites;

c) determining, by the receiver processing means, a time stamp for the signal to produce an associated time stamp of each said receiver;

d) transporting, via the digital communication network, by each said receiver processing means in the at least two sites the signal and the associated time stamp to produce at least two received signals;

e) receiving, by the at least two transmitters via the digital communication network, the at least two received signals and the associated time stamp of each said receiver;

f) comparing, by a transmitter processing means of the master transmitter, the at least two received signals to determine a highest quality signal;

g) transporting, by the master transmitter via the digital communication network, the highest quality signal and the associated time stamp;

h) receiving, by the at least two transmitters via the digital communication network, the highest quality signal and the associated time stamp;

i) determining, by the transmitter processing means of the at least two transmitters, a launch time for the highest quality signal;

j) buffering, by the transmitter processing means of the at least two transmitters, the highest quality signal; and

k) transmitting, by the transmitter processing means of the at least two transmitters, the highest quality signal at the launch time.

7. In the method of claim 6, wherein the determination of the signal quality metric of step (b) further comprises analyzing signal strength of the signal.

8. In the method of claim 6, wherein the determination of the signal quality metric of step (b) further comprises analyzing signal-to-noise ratio of the signal.

9. In the method of claim 6, wherein the determination of the signal quality metric of step (b) further comprises analyzing bit error rate of the signal.

10. In the method of claim 6, wherein the determination of the time stamp of step (c) further comprises determining time of arrival of the signal.

11. In the method of claim 10, wherein the determination of the time of arrival further comprises adding a predetermined offset to the time of arrival of the signal.

12. In the method of claim 6, wherein the transporting of the signal and the associated time stamp of step (d) further comprises compressing and packetizing the signals and the associated time stamp.

13. In the method of claim 6, wherein the determination of the launch time of step (i) further comprises adding a predetermined offset to time of arrival, at the receiver, of the highest quality signal.

14. In the method of claim 6, wherein the determination of the launch time of step (i) further comprises the associated time stamp of the highest quality signal.

15. In the method of claim 6, wherein the determination of the launch time of step (i) further comprises adding a predetermined offset to the associated time stamp of the highest quality signal.