Simultaneous analog and digital communication

• US 5,448,555 A
• Filed: 06/14/1993
• Issued: 09/05/1995
• Est. Priority Date: 06/14/1993
• Status: Expired due to Term

• Current Assignee: Summit Technology Systems LP
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Bremer, Gordon, Ko, Kenneth D., Smithwick, Luke J.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): BLUM, RUSSELL
• Application Number:
  US08/076,505
• Time in Patent Office: 813 Days
• Field of Search: 370/19, 370/20, 370/32.1, 375/8.39, 375/7, 329/304, 332/103
• US Class Current: 370/206
• CPC Class Codes: H04J 7/00 Multiplex systems in which the amplitudes or durations of the signals in individual channels are characteristic of those channels
• CPC Class Codes: H04L 27/186 in which the information is carried by both the individual signal points and the subset to which the individual signal points belong, e.g. coset coding or related schemes
• CPC Class Codes: H04L 27/32 Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
• CPC Class Codes: H04L 27/3483 using a modulation of the constellation points
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 7/08 Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band , e.g. by time division H04N7/007 takes precedence

Abstract

A method and apparatus for concurrent communication of analog information and digital information. In general terms, when the communication channel is viewed as a multi-dimensional space, the digital information signal is divided into symbols, and the symbols are mapped onto the signal space with a preset distance between them. The analog signal, generally limited in magnitude to less than the distance separating the symbols, is converted to component signals and added (i.e., vector addition) to the symbols. The sum signal is then transmitted to the receiver where the symbols are detected and subtracted from the received signal to yield the analog signal components. The transmitted analog signal is recreated from those components. Both half-duplex and full-duplex operation is available in accordance with the disclosure.

Claims

1. A method for communicating a digital signal together with a bandlimited analog signal, comprising the steps of:

mapping the digital signal into a sequence of symbols containing an N plurality of components, where N is an integer, forming thereby an N plurality of concurrent component sequences;

mapping the analog signal into an M plurality of mutually exclusive correlated component signals representing the analog signal, where M is an integer greater than 1; and

algebraically combining the plurality of concurrent component sequences with the plurality of component signals representing the analog signal, to form thereby a plurality of source signals.

2. The method of claim 1 where M is at most equal to N.

3. The method of claim 1 where M equals N.

4. The method of claim 1 further comprising the step of modulating the source signals with orthogonal modulation signals.

5. The method of claim 1 further comprising a step of measuring the signal power of the analog signal.

6. The method of claim 1 further comprising a step pre-emphasizing a selected frequency range of the analog signal.

7. The method of claim 1 further comprising a step modifying the frequency spectrum of the analog signal.

8. The method of claim 4 further comprising the step of transmitting the signals developed by the step of modulating.

9. The method of claim 1 wherein the analog signal comprises a plurality of constituent analog input signals and the step of mapping the analog signal comprises assigning different ones of the constituent analog input signals to different ones of the component signals representing the analog signal.

10. The method of claim 1 further including a step of multiplexing received analog constituent signals to form the analog signal employed in the step of mapping the analog signal.

11. The method of claim 1 further comprising a step of sampling an incoming analog signal to form the analog signal employed in the step of mapping the analog signal.

12. The method of claim 11 wherein the step of mapping the analog signal maps the samples obtained from the step of sampling.

13. The method of claim 11 wherein the step of mapping the analog signal maps the samples obtained from the step of sampling by scrambling their order.

14. The method of claim 11 further comprising a step of quantizing the analog samples obtained from the step of sampling.

15. The method of claim 11 further comprising a step of digitizing the analog samples obtained from the step of sampling.

16. The method of claim 15 wherein the steps of mapping the analog signal, mapping the digital signal, and combining are carried out digitally.

17. The method of claim 1 wherein the step of mapping the analog signal comprises sampling the analog signal and assigning successive samples to different ones of the component signals representing the analog signal.

18. The method of claim 17 further comprising a step of multiplying each of the analog signals with a coefficient derived from a pseudo-random sequence.

19. In a method for communicating digital signals where the digital signal is divided into a sequence of symbols, where each of the symbols is mapped onto a pair of components to form a pair of component sequences, and where the component sequences are modulated by respective carrier signals that are orthogonal to each other, an improvement comprising the step of:

adding a first stream of analog samples to one of the pair of component sequences and a second stream of analog samples to the other of the pair of component sequences, prior to the component sequences being modulated where the first stream of samples and the second stream of samples are mutually exclusive.

20. A method for communicating a digital signal together with a bandlimited analog signal, where the digital signal is represented by a sequence of symbols and the analog signal is represented by a sequence of samples, comprising the steps of:

converting each of the symbols into a base multi-dimensional signal element;

joining groups of said samples and converting each such group into an additive multi-dimensional signal element;

combining the additive multi-dimensional signal elements with the base multi-dimensional signal elements to form combined multi-dimensional signal elements;

modulating the combined multi-dimensional signal elements signal to form a modulated signal; and

transmitting the modulated signal.

21. A method for communicating a digital signal together with a bandlimited analog signal, where the digital signal is represented by a sequence of symbols and the analog signal is represented by a sequence of samples, comprising the steps of:

converting each of the symbols into component signals x_d and y_d ;

identifying pairs of samples in the sequence of samples representing the analog signal and converting each such pair into component signals x_a and y_a ;

forming super symbols by creating x=x_a +x_d and y=y_a +y_d component signals;

modulating the x and y component signals to form a modulated signal; and

transmitting the modulated signal.

22. The method of claim 21 wherein said step of modulating comprises:

modulating component x with a first carrier signal to form a V_x signal,

modulating component y with a second carrier signal to form a V_y signal,

where the second carrier signal is orthogonal to the first carrier signal, and

adding the V_x signal and the V_y signal to form said modulated signal.

23. A method for communicating a digital signal represented by a sequence of symbols, and a bandlimited analog signal represented by a sequence of samples, comprising the steps of:

converting each of the symbols into a set of N base signals, where N is a preselected integer greater than 1;

joining said samples into groups of N samples each, and converting each such group into a set of N additive signals;

forming combinations of the sets of N additive signals and the sets of N base signals, to form super symbols formed of sets of N signals; and

modulating each set of N signals of the super symbols with a carrier from a set of N mutually orthogonal carrier signals.

24. A method for transmitting a digital data signal and a bandlimited analog signal, comprising the steps of:

creating a symbol representative of a number of bits of the digital data signal,

mapping said symbol into a first component signal and a second component signal,

obtaining a first sample and a second sample of the bandlimited analog signal,

adding the first sample to the first component signal to form a first added signal,

modulating the first added signal with a first carrier signal,

adding the second sample to the second component signal to form a second added signal, and

modulating the second added signal with a second carrier signal, which carrier signal is orthogonal to the first carrier signal.

25. A method for receiving a signal that concurrently contains both a digital signal and an analog signal, comprising the steps of:

demodulating a received signal to form a plurality of combined component signals,

detecting digital signal components contained within the combined component signals,

de-mapping at least some of the digital signal components to form a stream of digital signals, and

subtracting at least some of the detected digital signal components from the combined component signals to develop component analog signals.

28. The method of claim 25 further comprising a step of adaptive filtering of the signals developed by the step of demodulating.

29. The method of claim 28 wherein said step of filtering is a function of filter coefficients that are modifiable under command of control signals.

26. A method for receiving a signal that concurrently contains both a digital signal and an analog signal, comprising the steps of:

demodulating a received signal to form a plurality of combined component signals,

detecting digital signal components contained within the combined component signals,

de-mapping the digital signal components to form a stream of digital signals,

subtracting the detected digital signal components from the combined component signals to develop component analog signals, and

de-mapping the component analog signals to form an output analog signal.

27. A method for receiving a signal that concurrently contains both a digital signal and an analog signal, comprising the steps of:

demodulating a received signal to form component signals,

detecting symbols in the component signals,

de-mapping the symbols to form a stream of digital signals,

mapping the symbols to form digital component signals,

subtracting the digital component signals from the component signals obtained from the step of demodulating, to form component analog signals, and

de-mapping the component analog signals to form an output analog signal.

30. In a system including a signal space mapper followed by a modulator, where a digital input symbol applied to the mapper is assigned to a constellation point in N-dimension space, and where the modulator modulates the constellation point with N mutually orthogonal carrier signals, at improvement comprises:

an analog port included in the mapper, for accepting a group of N analog signal samples, and

said mapper including means for altering the constellation point assignment for the digital input sample in response to the group of N analog signal samples.

31. The system of claim 30 further including a processor coupled to the analog port for receiving an analog signal and for developing said group of N analog signal samples.

32. The system of claim 31 wherein said process pre-emphasizes a selected frequency range of said analog signal.

33. The system of claim 31 wherein said processor encodes the analog signal to develop an encoded signal having a dynamic range that is smaller than the dynamic range of the analog signal.

34. The system of claim 31 wherein said processor performs automatic gain control on the analog signal.

35. The system of claim 30 wherein the analog samples are pulse code modulated.

36. The system of claim 31 wherein said processor shifts the frequency band of the input signal.

37. A modem comprising:

a signal mapper having a digital signal applied to the mapper at a digital port and an analog signal applied to the mapper at an analog port,

a modulator, responsive to the Signal mapper, for developing a modulated output signal at an output port of the modulator representable by an N-dimensional signal space, where N is greater than 1, that is composed of a plurality of N-dimensional enclosed spaces with a predetermined point in each of the spaces associated with a digital symbol applied to said mapper via the applied digital signal, and other points in each of the spaces associated with the analog signals applied to said signal mapper,

means for coupling the output port of the modulator to an output port of the modem, and

selection means having inputs A and B and outputs A and B, where output A is an analog output that is connected to the analog port and output B is a digital output that is connected to the digital port, responsive to an analog input signal at input A and a digital input signal at input B, for selectively applying the signals at input A and input B to the analog input port and the digital input port, to form an output signal at the output port of the modem which represents

the analog signal at input A and not the digital signal at input B,

the digital signal at input B and not the analog signal at input A,

the analog signal at input A as well as the digital signal at input B.

38. A modem comprising:

a first mapper responsive to a digital signal,

a second mapper responsive to an analog signal, and

an orthogonal modulator having two inputs, where the two inputs are concurrently responsive to output signals of the first mapper and output signals of the second mapper to develop an output signal, the modem further comprising pre-emphasis means preceding said first mapper, for increasing the high frequency components of the analog signal.

39. A modem comprising:

a first mapper responsive to a digital signal,

a second mapper responsive to an analog signal, and

an orthogonal modulator concurrently responsive to output signals of the first mapper and the second mapper, developing an output signal, the modem further comprising multiplexer means responsive to a plurality of constituent analog signals for developing the analog signal applied to said first mapper.

40. A modem comprising:

a first mapper responsive to a digital signal,

a second mapper responsive to an analog signal,

an orthogonal modulator concurrently responsive to output signals of the first mapper added to output signals of the second mapper to develop an output signal,

a hybrid having a first port that receives the output signal developed by the orthogonal modulator, said hybrid communicating substantially all of the signals received at the first port to a second port of the hybrid,

an echo canceller coupled to a third port of the hybrid, for subtracting from the third port a portion of the signal applied to said first port of the hybrid,

a demodulator responsive to output signals of the echo canceller,

a slicer for detecting digital signal components contained in output signals developed by the demodulator,

a first de-mapper for forming a stream of digital signals in response to output signals of the slicer,

means for subtracting the detected digital signal components from the signals developed by the demodulator, to develop thereby component analog signals, and

a second de-mapper for forming analog signal from output signals of the means for subtracting.

41. The modem of claim 40 further comprising an equalizer interposed between the demodulator and the slicer.

42. The modem of claim 41 wherein the equalizer is adaptive.

43. The modem of claim 42 wherein the equalizer includes coefficients that are altered under control of a signal power measuring means that is responsive to the output signals of the means for subtracting.

44. The modem of claim 42 wherein the equalizer includes coefficients that are altered under control of a signal power measuring means that is responsive to the output signals of the second de-mapper.

45. The modem of claim 40 further comprising a demultiplexer interposed before the second de-mapper.

46. A modem including a transmitter carrier frequency rotator, two Hilbert passband transmitter filters responsive to the transmitter carrier frequency rotator, having their outputs summed and applied to a hybrid circuit, an echo canceller responsive to the transmitter carrier frequency rotator and to an output of the hybrid circuit, for developing an echo-canceled received signal, two additional Hilbert passband receiver filters responsive to the echo-canceled received signal, a receiver carrier frequency rotator responsive to the two Hilbert passband receiver filters, an equalizer responsive to the receiver carrier frequency rotator, and a carrier phase corrector responsive to the equalizer, THE IMPROVEMENT COMPRISING:

an analog signal mapper responsive to applied analog signals for applying a first input signal to the transmitter carrier frequency rotator,

a digital signal mapper responsive to applied digital signals for applying a second input signal to the transmitter carrier frequency rotator,

a digital signal detector responsive to output signals of said carrier phase corrector for developing a digital output signal and subtraction signals,

means for combining the subtraction signals with the output signals of the carrier phase corrector, and

a de-mapper responsive to the means for combining, for developing analog output signals.