Simulcast synchronization and equalization system and method therefor

• US 5,261,118 A
• Filed: 10/04/1991
• Issued: 11/09/1993
• Est. Priority Date: 10/04/1991
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Vanderspool, Jan P. II, Goreham, Steven A.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US07/771,911
• Time in Patent Office: 767 Days
• Field of Search: 455/12.1, 455/13.2, 455/51.1, 455/51.2, 455/53.1, 455/69, 455/67.5, 455/67.6, 375/107, 375/108, 375/109
• US Class Current: 455/503
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency

Abstract

A control station 12 initiates a system timing signal transmission which is re-transmitted from a satellite 14. In response to receiving the system timing signal, the control station 12 then generates a time correction factor which is distributed to a plurality of transmission stations 16, 18. The transmission stations 16, 18 in response to receiving the system timing signal transmission and the time correction factor distributed from the control station 12 generate a time adjustment factor which is used to correct the local transmission clocks 36, 36'"'"', thereby providing time synchronization of data transmissions generated from the transmission stations 16, 18.

Claims

1. A simulcast transmission system having means for time synchronizing the transmission of data signals therefrom, comprising:

a control station comprising first time generating means for generating system timing signals and for transmitting the same, means for receiving the transmitted system timing signals, means for comparing the transmitted and received system timing signals to generate a time correction factor signal in response thereto, and means for distributing the time correction factor signal to a plurality of transmission stations; and

each of said plurality of transmission stations comprising second time generating means for generating local timing signals, means responsive to local timing signals for transmitting the data signals, means for receiving the transmitted system timing signals, means for receiving the time correction factor signal, means for comparing the received system timing signals and time correction factor signal with the local timing signals to generate a time adjustment factor signal, and means responsive to the time adjustment factor signal for adjusting the timing of said second time generating means.

2. The simulcast transmission system according to claim 1, wherein said first time generating means comprises:

means for generating frequency reference signals; and

master clock means, responsive to the frequency reference signals for generating the system timing signals.

3. The simulcast transmission system according to claim 1, wherein said second time generating means comprises:

means for generating frequency reference signals; and

local clock means, responsive to the frequency reference signals for generating the local timing signals.

4. The simulcast transmission system according to claim 1, wherein said means for transmitting the system timing signals comprises:

satellite up-link transmitter means for transmitting the system timing signals to a satellite, said satellite having satellite receiving means for receiving the transmitted system timing signals, and satellite transmitter means, coupled to said satellite receiving means, for re-transmitting the received system timing signals.

5. The simulcast transmission system according to claim 4, wherein said means for transmitting the system timing signals further transmits the data signals and data transmission start time signals.

6. The simulcast transmission system according to claim 1, wherein said means for comparing the transmitted and received system timing signals comprises a microcomputer.

7. The simulcast transmission system according to claim 6, wherein the time correction factor signal includes a time correction factor value calculated by said microcomputer using

8. The simulcast transmission system according to claim 1, wherein said means for comparing the received system timing signals and time correction factor signal with the local timing signals comprises a microcomputer.

9. The simulcast transmission system according to claim 8, wherein the time adjustment factor signal includes a time adjustment factor value calculated by said microcomputer using

10. The simulcast transmission system according to claim 1, wherein the system timing signals include at least timing information corresponding to a predetermined time for the transmission of the data signals from said plurality of transmission stations and synchronization signals which include at least synchronization information identifying a predetermined time mark and data signal transmission time information corresponding thereto.

11. The simulcast transmission system according to claim 10, wherein the synchronization signals re periodically generated.

12. The simulcast transmission system according to claim 1, wherein said means for adjusting the timing of said second time generating means comprises:

means for storing a time adjustment factor value derived by comparing the received system timing signals and time correction factor signal with the local timing signals;

converter means, coupled to said storing means, for converting the stored time adjustment factor value into the time adjustment factor signal.

13. The simulcast transmission system according to claim 12, wherein said time adjustment factor value is a digital information sequence, and wherein said converter means converts the digital information sequence into an analog signal corresponding to the time adjustment factor signal.

14. The simulcast transmission system according to claim 1, wherein said transmissions stations further comprise means for storing a distance correction factor signal, and said means for comparing compares the received system timing signals and time correction factor signal with the local timing signals and a distance correction factor signal to generate the time adjustment factor signal.

15. The simulcast transmission system according to claim 14, wherein said transmissions station further comprises memory means for storing information, and wherein the distance correction factor signal includes a distance correction factor value which is stored in said memory means.

16. The simulcast transmission system according to claim 15, wherein said means for comparing the received system timing signals and time correction factor signal with the local timing signals and a distance correction factor signal comprises a microcomputer.

17. The simulcast transmission system according to claim 16, wherein the time adjustment factor signal includes a time adjustment factor value calculated by said microcomputer using

18. A transmission station for use in a simulcast transmission system comprising a plurality of transmission stations which are capable of providing simulcast transmission of data signals, the simulcast transmission system having a control station which is capable of generating system timing signals, and in response thereto generating a time correction factor signal, and for distributing the time correction factor signal to the plurality of transmission stations, said transmission station comprising:

time generating means for generating local timing signals;

means, responsive to local timing signals, for transmitting the data signals;

means for receiving the transmitted system timing signals;

means for receiving the time correction factor signal;

means for comparing the received system timing signals and the time correction factor signal with the local timing signals to generate a time adjustment factor signal; and

means responsive to the time adjustment factor signal for adjusting the timing of said time generating means.

19. The transmission station according to claim 18, wherein said time generating means comprises:

frequency reference generating means for generating frequency reference signals; and

local clock means, responsive to the frequency reference signals for generating the local timing signals.

20. The transmission station according to claim 19, wherein said means for transmitting the data signals transmits the data signals at a predetermined transmission frequency.

21. The transmission station according to claim 20, wherein the predetermined transmission frequency is established by the frequency reference signals generated.

22. The transmission station according to claim 18, wherein said means for comparing the received system timing signals and the time correction factor signal with the local timing signals comprises a microcomputer.

23. The transmission station according to claim 22, wherein the time adjustment factor signal includes a time adjustment factor value calculated by

24. The transmission station according to claim 18, wherein the system timing signals include at least timing information corresponding to a predetermined time for data signal transmission from said transmission station and synchronization signals which include at least synchronization information identifying a predetermined time mark and data signal transmission time information corresponding thereto.

25. The transmission station according to claim 23, wherein said means for adjusting the timing of said time generating means comprises:

means for storing the time adjustment factor value;

converter means, coupled to said storing means, for converting the stored time adjustment factor value into the time adjustment factor signal.

26. The transmission station according to claim 25, wherein said time adjustment factor value is a digital information sequence, and wherein said converter means converts the digital information sequence into an analog signal corresponding to the time adjustment factor signal.

27. The transmission station according to claim 18 further comprising means for storing a distance correction factor signal, and said means for comparing compares the received system timing signals and time correction factor signal with the local timing signals and a distance correction factor signal to generate the time adjustment factor signal.

28. The transmission station according to claim 27 further comprising memory means for storing information, and wherein the distance correction factor signal includes a distance correction factor value which is stored in said memory means.

29. The transmission station according to claim 28, wherein said means for comparing the received system timing signals and the time correction factor signal with the local timing signals and the distance correction factor signal comprises a microcomputer.

30. The transmission station according to claim 29, wherein the time adjustment factor signal includes a time adjustment factor value calculated by

31. A method of time synchronizing data signal transmissions originating from a plurality of transmission stations operating within a simulcast transmission system, the transmission stations having transmission clocks for controlling the starting time of the data signal transmissions, said method comprising the step of:

generating, at a control station, a time correction factor signal in response to the control station generating and transmitting a system timing signal;

distributing the system timing signal and the time correction factor signal from the control station to the transmission stations;

generating, at the transmission stations, local time adjustment factor signals in response to receiving the system timing signal and the time correction factor signal;

adjusting the transmission clocks at the transmission stations in response to the local time adjustment factor signals generated.

32. The method of time synchronizing data signal transmissions according to claim 31 wherein said step of generating a time correction factor signal at the control station comprises the steps of:

transmitting, from the control station, the system timing signal which includes at least a timing word which provides a time mark indicating a time of transmission of the system timing signal;

receiving the system timing signal including the timing word at the control station to detect the time of reception of the system timing signal; and

comparing the time of reception of the system timing signal with the time of transmission of the system timing signal to determine a value for the time correction factor signal.

33. The method of time synchronizing data signal transmissions according to claim 32, wherein said step of comparing comprises the step of calculating a value for the time correction factor signal according to the formula

34. The method of time synchronizing data signal transmissions according to claim 32 wherein said step of generating a time adjustment factor signal comprises the steps of:

receiving the system timing signal including the timing word at the transmission station to detect the local time of reception of the timing word; and

comparing the local time of reception with the time of transmission of the system timing signal and the time correction factor to determine a value for the time adjustment factor signal.

35. The method of time synchronizing data signal transmissions according to claim 34, wherein said step of comparing comprises the step of calculating the value for the time adjustment factor signal according to the formula