TDM communication system for efficient spectrum utilization

• US 4,754,450 A
• Filed: 03/25/1986
• Issued: 06/28/1988
• Est. Priority Date: 03/25/1986
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Schorman, Eric R., Linder, Donald L., Lynk, Charles N. Jr.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Marcelo, Melvin
• Application Number:
  US06/843,882
• Time in Patent Office: 826 Days
• Field of Search: 370/29, 370/26, 370/30, 370/50, 370/75, 370/95, 370/97, 370/109, 370/118, 381/36, 455/17
• US Class Current: 370/280
• CPC Class Codes: H04B 1/66 for reducing bandwidth of signals; for improving efficiency of transmission H04B1/68 takes precedence
• CPC Class Codes: H04J 3/1688 the demands of the users being taken into account after redundancy removal, e.g. by predictive coding, by variable sampling reducing bandwidth of signals in general H04B1/66; in PCM-systems H04B14/046; removal of redundancy in telegraph communication H03M7/30

Abstract

A time division multiplexed (TDM) communication system is disclosed, which apportions radio frequency communication channels into at least two time slots. Voice signals for transmission on this system are analyzed and vo-coded into a digital signal that is transmitted during one or more of the time slots. Received messages are recovered from at least one of these time slots and the voice message synthesized from the vo-coded signal. In this manner multiple voice messages may be transceived in a time division multiplexed manner on a single narrowband communication channel.

Claims

1. In a time division multiplex communication system which apportions radio frequency communications channels into at least two time slots for communicating voice signals vo-coded at a predetermined rate, V, a transceiving device comprising:

means for providing a clock signal having a frequency at least twice that of the vo-coding rate;

means for receiving a vo-coded signal from a communication channel having a predetermined maximum data rate, C, during at least one time slot in accordance with a time division multiplex protocol defining N time slots, where N is a positive integer less than or equal to C/V, at a rate approximately equal to said clock signal to provide a received signal, said receiving means including means for synchronizing the device to said received signal;

means for buffering said received signal to provide a buffered signal;

means for transmitting said buffered signal onto said communication channel during at least one of said N time slots at a rate approximately equal to said clock signal, said transmitting means including means for generating and preambling a data signal which includes at least a synchronization signal to said buffered signal;

means for controlling the device whereby the device operates as a single frequency repeater.

2. In a time division multiplex communication system which apportions radio frequency communication channels into at least two time slots for communicating voice signals vo-coded at a predetermined rate, V, a transceiving device comprising:

means for providing a clock signal having a frequency at least twice that of the vo-coding rate;

means for receiving a vo-coded signal from a first communication channel having a predetermined maximum data rate, C, during at least one time slot in accordance with a time division multiplex protocol defining N time slots, where N is a positive integer less than or equal to C/V, at a rate approximately equal to said clock signal to provide a received signal, said receiving means including means for synchronizing the device to said received signal;

means for transmitting said received signal onto a second communication channel also having said predetermined maximum data rate, C, during at least one time slot in accordane with said time division multiplexed protocol defining said N time slots, at a rate approximately equal to said clock signal, said trasmitting means including means for generating and preambling a data signal which includes at least a synchronization signal to said received signal;

means for controlling the device whereby the device operates as a time division multiplex repeater.

3. In a time division multiplex communication system which apportions radio frequency communication channels into at least two time slots for communicating voice signals, an improved transceiving device comprising:

means for receiving a vo-coded signal from a communication channel having predetermined maximum data rate, C, during at least one time slot in accordance with a time division multiplex protocol defining N time slots, where N is a positive integer less than or equal to C/V, where V comprises a selected coding rate, at a rate approximately equal to twice said selected coding rate to provide a received signal, said receiving means including means for synchronizing the device to said received signal;

means for analyzing a voice signal at said selected coding rate to provide a vo-coded signal;

means for generating and preambling a data signal which includes at least a synchronization signal to said vo-coded signal;

first and second buffering means for buffering respectively said recevied signal at approximately twice said selected coding rate, and said vo-coded signal at said selected coding rate;

means for transmitting said buffered vo-coded signal onto said communication channel during at least one of said N time slots at a rate approximately equal to twice said selected coding rate;

means for synthesizing a recovered voice signal from said buffered received signal at a rate approximately equal to said selected coding rate; and

means for controlling the time division multiplex transceiving device, whereby the device operates in a first mode to repeat said vo-coded signal received during said first time slot during said second time slot, and operates in a second mode to simulate full duplex operation on a single communication channel.

4. In a time division multiplex communication system which apportions radio frequency communication channels into at least two time slots for communicating voice signals, a transceiving device comprising:

means for transmitting a vo-coded signal onto a communication channel having a predetermined maximum data rate, C, in accordance with a time division multiplex protocol defining N time slots where N is a positive integer less than or equal to C/V, where V comprises a selected coding rate, said vo-coded signal being temporarily buffered at a first rate and transmitted at a rate exceeding 2 V during at least one of said N time slots, said transmitting means including means for analyzing a voice signal at said selected coding rate, V, to provide said vo-coded signal, and means for generating and preambling a data signal, which includes at least a synchronization signal to said vo-coded signal;

means for receiving and buffering a vo-coded signal from the communication channel in accordance with said time division multiplex protocol during at least one of said N time slots to provide a received signal, said receiving means including means for synchronizing to at least a portion of said synchronization signal, and means for processing said received signal at said selected coding rate, V, to synthesize a recovered voice signal from said received signal; and

means for intercoupling and controlling said transmitting means and said receiving means such that the device operates to repeat said received signal received in at least one of said N time slots during at least one other time slot thereby providing a single frequency repeater.

5. The device of claim 4, wherein the frequency of said selected coding rate comprises 4.8 kHz.

6. The device of claim 4, wherein the frequency of said selected coding rate comprises 2.4 kHz.

7. The device of claim 4, wherein said analyzing means comprises an LPC analyzer.

8. The device of claim 4, wherein said analyzing means comprises a SBC analyzer.

9. The device of claim 4, wherein said processing means comprises an LPC synthesizer.

10. The device of claim 4, wherein said processing means comprises a SBC synthesizer.

11. The device of claim 4, wherein said transmitting and receiving means are constructed and arranged to operate on a communication channel having a 25 kHz bandwidth.

12. In a time division multiplex communication system which apportions radio frequency communication channels into at least two times slots for communicating voice signals, a transceiving device comprising:

means for transmitting a vo-coded signal onto a communication channel having a predetermined maximum data rate, C, in accordance with a time division multiplex protocol defining N time slots where N is a positive integer less than or equal to C/V, where V comprises a selected coding rate, said vo-coded signal being temporarily buffered at a first rate and transmitted at a rate exceeding 2 V during at least one of said N time slots, said transmitting means including means for analyzing a voice signal at said selected coding rate, V, to provide said vo-coded signal, and means for genrating said preambling a data signal, which includes at least a synchronization signal to said vo-coded signal;

means for receiving and buffering a vo-coded signal from the communication channel in accordance with said time division multiplex protocol during at least one of said N time slots to provide a received signal, said receiving means including means for synchronizing to at least a portion of said synchronization signal, and means for processing said received signal at said selected coding rate, V, to synthesize a recoverd voice signal from said received signal; and

means for duplexing said transmitting means and said receiving means such that the device operates to repeat said received signal received from at least one of said N time slots on a first frequency in at least one of said N time slots on a second frequency.

13. The device of claim 12, wherein the frequency of said selected coding rate comprises 4.8 kHz.

14. The device of claim 12, wherein the frequency of said selected coding rate comprises 2.4 KHz.

15. The device of claim 12, wherein said analyzing means comprises an LPC analyzer.

16. The device of claim 12, wherein said analyzing means comprises an SBC analyzer.

17. The device of claim 12, wherein said processing means comprises an LPC synthesizer.

18. The device of claim 12, wherein said processing means comprises an SBC synthesizer.

19. The device of claim 12, wherein said transmitting and said receiving means are constructed and arranged to operate on a communication channel having a 25 kHz bandwidth.

20. In a time division multiplex communication system which apportions radio frequency communication channels into at least two time slots for communicating voice signals, a transceiving device comprising:

means for transmitting a vo-coded signal onto a communication channel having a predetermined maximum data rate, C, in accordance with a time division multiplex protocol defining N time slots where N is a positive integer less than or equal to C/V, where V comprises a selected coding rate, said vo-coded signal being temporarily buffered at a first rate and transmitted at a rate exceeding 2 V during at least one of said N time slots, said transmitting means including means for analyzing a voice signal at said selected coding rate, V, to provide said vo-coded signal, and means for generating and preambling a data signal, whih includes at least a synchronization signal to said vo-coded signal;

means for receiving and buffering a vo-coded signal from the communication channel in accordance with said time division multiplex protocol during at least one of said N time slots to provide a received signal, said receiving means including means for synchronizing to at least a portion of said synchronization signal, and means for processing said received signal at said selected coding rate, V, to synthesize a recovered voice signal from said received signal; and

means for controlling and selectively intercoupling said transmitting means and said receiving means, such that the device operates in a first mode to repeat said received signal received in at least one of said N time slots during at least one other time slot, and operates in a second mode to simulate full duplex communication on a single channel.

21. The device of claim 20, wherein the frequency of said selected coding rate comprises 4.8 kHz.

22. The device of claim 20, wherein the frequency of said selected coding rate comprises 2.4 kHz.

23. The device of claim 20, wherein said analyzing means comprises an LPC analyzer.

24. The device of claim 20, wherein said analyzing means comprises an SBC analyzer.

25. The device of claim 20, wherein said processing means comprises an LPC synthesizer.

26. The device of claim 20, wherein said processing means comprises an SBC synthesizer.

27. The device of claim 20, wherein said transmitting and said receiving means are constructed and arranged to operate on a communication channel having a 25 kHz bandwidth.