Data transmission method and apparatus by period shift keying (TSK)

• US 4,926,444 A
• Filed: 04/29/1988
• Issued: 05/15/1990
• Est. Priority Date: 04/29/1988
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Farmer, James O., Naddor, David J., Harney, Michael P., Hamilton, Scott L., Frederick, Richard B., Schaubs, Randolph J.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Bocure, Tesfaldet
• Application Number:
  US07/187,978
• Time in Patent Office: 746 Days
• Field of Search: 375/9, 375/44, 375/45, 375/51, 375/46, 375/47, 375/48, 375/49, 375/50, 375/62, 375/67, 375/82, 375/83, 375/88, 329/110, 332/9, 332/16, 379/96, 360/43
• US Class Current: 375/223
• CPC Class Codes: H04L 27/10 Frequency-modulated carrier systems, i.e. using frequency-shift keying H04L27/32 takes precedence

Abstract

Apparatus for transmitting and receiving a period shift keyed data stream comprises a data processor such as a microprocessor which may control the generation of the waveform as well as the determination of the bit values of an incoming signal. When the data to be transmitted comprises a plurality of data values, each data value is represented by a different predetermined frequency. Further, each data value is represented by the transmission of the predetermined frequency for a predetermined transitionary interval plus one cycle or period. One portion of the transitionary interval precedes and the remaining portion follows the one cycle. For example, the data value may be represented by a three cycle burst of frequency such that, in determining the represented data value, two cycles of transitionary interval are detected but ignored and the central cycle of the three cycle burst is timed for determining the data value by edge detection techniques. Consequently, transitionary influences caused by changes in frequency do not adversely affect data value determination.

Claims

1. A method for transmitting data by period shift keying, the data to be transmitted having a plurality of data values, each data value being represented by a different predetermined frequency, the data transmission method comprising the steps of:

storing period values of the predetermined frequencies of the plurality of data values to be transmitted and

generating a waveform having a predetermined number of cycles at the different predetermined frequency for each data value, said waveform consisting of a predetermined transitionary interval and at least one period for each data value to be transmitted, one portion of the predetermined transitionary interval preceding and a remaining portion following the at least one period for each data value to be transmitted, the generated waveform beginning at an edge of a pulse and including at least two additional pulse edges.

2. The data transmission method of claim 1 wherein the predetermined transitionary interval comprises two cycles.

3. The data transmission method of claim 2 wherein each transitionary interval portion comprises one cycle.

4. The data transmission method of claim 1 wherein the plurality of data values comprises binary bit values, zero and one.

5. A method for receiving period shift keyed data on a waveform, the received period shift keyed data having a plurality of data values, each data value being determined by the period of a different predetermined frequency, each data value being represented by the transmission of a predetermined number of cycles at the different predetermined frequency for each data value, the waveform consisting of a predetermined transitionary interval and at least one period for each data value, one portion of the predetermined transitionary interval preceding and a remaining portion following the at least one period for each data value, the data reception method comprising the steps of:

storing at least one threshold value associated with the plurality of data values,

sensing the waveform and ignoring transitionary intervals,

calculating the duration of the at least one period for each received data value between at least two successive pulse edges,

comparing the calculated duration of the at least one period with the associated threshold value for the plurality of data values, and

determining the data value from the comparison.

6. The data reception method of claim 5 wherein the predetermined transitionary interval comprises two cycles.

7. The data reception method of claim 6 wherein each transitionary interval portion comprises one cycle.

8. The data reception method of claim 5 wherein the plurality of data values comprises binary bit values, zero and one.

9. The data reception method of claim 5 wherein the threshold value is determined from calculating an average period value for received period shift keyed data.

10. Apparatus for encoding data by period shift keying, the data to be transmitted having a plurality of data values, each data value being represented by a different predetermined frequency, the data encoding apparatus comprising

memory means for storing period values of the predetermined frequencies of the plurality of data values to be transmitted, a predetermined transitionary interval comprising one portion and a remaining portion, and a software algorithm;

means for providing a clock oscillator output at a reference frequency much larger than the predetermined frequencies of the plurality of data values; and

means, responsive to the memory means and the clock means, for controlling the generation of a waveform having a predetermined number of cycles at the different predetermined frequency for each data value, the waveform consisting of the transitionary interval and at least one period for each data value to be transmitted, the one portion of the transitionary interval preceding and the remaining portion following the at least one period of the predetermined frequency for each data value to be transmitted, the generated waveform beginning at an edge of a pulse and including at least two additional pulse edges.

11. Data encoding apparatus of claim 10 wherein the predetermined transitionary interval comprises two cycles.

12. Data encoding apparatus of claim 11 wherein each transitionary interval portion comprises one cycle.

13. Data encoding apparatus of claim 10 wherein the plurality of data values comprises binary bit values, zero and one.

14. Data encoding apparatus of claim 10 further comprising

means, responsive to the waveform generation control means, for conditioning the generated waveform for transmission on a particular transmission channel.

15. Data encoding apparatus of claim 14 wherein the conditioning means comprises an active filter circuit.

16. Apparatus for decoding period shift keyed data on a waveform, the received period shift keyed data having a plurality of data values, each data value being determined by the period of a different predetermined frequency, each data value being represented by the transmission of a predetermined number of cycles at the different predetermined frequency for each data value, the waveform consisting of a predetermined transitionary interval and at least one period for each data value, one portion of the predetermined transitionary interval preceding and the remaining portion following the one period for each data value, the data decoding apparatus comprising

memory means for storing at least one threshold value associated with the period of the different predetermined frequencies of the plurality of data values transmitted, the predetermined transitionary interval comprising the one portion and the remaining portion, and a software algorithm;

means for providing a clock oscillator output at a reference frequency much higher than the predetermined frequencies of the plurality of data values; and

means, responsive to the memory means and the clock means, for controlling the determination of data values from an incoming period shift keyed data waveform by sensing and ignoring transitionary intervals, calculating the duration of the at least one period for each received data value between two successive edges, comparing the calculated duration of the one period with the associated threshold value for the plurality of data values and determining the data value for each received data value from the comparison.

17. The data decoding apparatus of claim 16 wherein the predetermined transitionary interval comprises two cycles.

18. The data decoding apparatus of claim 17 wherein each transitionary interval portion comprises one cycle.

19. The data decoding apparatus of claim 16 wherein the plurality of data values comprises binary data values, zero and one.

20. The data decoding apparatus of claim 16 further comprising

means, coupled to a transmission channel, for conditioning the incoming period shift keyed waveform to an appropriate level and pass band and

means, coupled to the conditioning means, for comparing the output of the conditioning means to a reference voltage, the output of the comparison means being coupled to an input of the data value determination control means.

21. Apparatus for encoding and decoding period shift keyed data, the period shift keyed data having a plurality of data values, each data value being determined by the period of a different predetermined frequency, each data value being represented by the transmission of the different predetermined frequency for a predetermined transitionary interval plus at least one period, one portion of the predetermined transitionary interval preceding and the remaining portion following the one period of the predetermined frequency, the data encoding and decoding apparatus comprising

memory means for storing the periods of the predetermined frequencies of the plurality of data values to be transmitted, at least one threshold value associated with the periods of the predetermined frequencies, the predetermined transitionary interval comprising the one portion and the remaining portion, and a software algorithm;

means for providing a clock oscillator output at a reference frequency much higher than the predetermined frequencies of the plurality of data values; and

means, responsive to the memory means and the clock means, for controlling the generation of a waveform having a predetermined number of cycles of period shift keyed data for each data value to be transmitted and the determination of data values from an incoming period shift keyed data waveform having an equal number of cycles of period shift keyed data for each received data value.

22. The data encoding and decoding apparatus of claim 21 wherein the predetermined transitionary interval comprises two cycles.

23. The data encoding and decoding apparatus of claim 22 wherein each transitionary interval portion comprises one cycle.

24. The data encoding and decoding apparatus of claim 21 wherein the plurality of data values comprises binary bit values, zero and one.

25. The data encoding and decoding apparatus of claim 21 further comprising

a transmission channel interface particularly comprising a first filter coupled to a data output of the controller means at which output is provided the period shift keyed data output, a transmission channel interface network coupled to the output of the first filter and to a transmission channel, a second filter, coupled to the transmission channel interface network, for receiving a data signal from the transmission channel, and a comparator, coupled to a data input of the controller means and to an output of the first filter.

26. The data encoding and decoding apparatus of claim 25 wherein the first filter further provides a dynamic reference level input to the comparator for comparison with the output of the second filter.

27. The data encoding and decoding apparatus of claim 26 wherein the dynamic reference level input to the comparator is coupled to the output of the comparator and the data input of the controller means.

28. The data encoding and decoding apparatus of claim 25 further comprising a telephone network circuit coupled between the transmission channel interface and the transmission channel, the transmission channel comprising a telephone channel, the controller means for further controlling the operation of the telephone network circuit.

29. A data encoding method for transmission of data on a waveform comprising the steps of:

(a) fetching a data value;

(b) determining a predetermined half period corresponding to said fetched data value;

(c) generating said waveform by toggling an output state of an output signal and starting a timer to time said predetermined half period;

(d) returning to step (c) when said timer has finished timing said predetermined half period until a predetermined number "n" of toggled output states have been toggled for said fetched data value; and

(e) returning to step (a) for transmitting another data value.

30. The data encoding method of claim 29, wherein "n" is at least 6.

31. A data decoding method for reception of data on a waveform comprising the steps of:

(a) sensing an integral number "p" of transitions of said waveform, wherein "p" is greater than zero;

(b) sensing a further transition of said waveform and marking a reference time;

(c) sensing an integral number "q" of additional transitions of said waveform, wherein "q" is greater than zero, and determining elapsed time since said further transition at said marked reference time;

(d) comparing said elapsed time with predetermined thresholds;

(e) generating a signal comprising a data value in response to said comparison; and

(f) repeating steps (a) through (e) to receive another data value on said waveform.

32. The data decoding method of claim 31, wherein "p" is at least 2 and "q" is at least 1.

33. The data decoding method of claim 31, wherein said transitions consist of either rising edges or falling edges.