Communication signal compression system and method

• US 4,974,099 A
• Filed: 06/21/1989
• Issued: 11/27/1990
• Est. Priority Date: 06/21/1989
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: International Mobile Machines Corporation (InterDigital, Inc.)
• Inventors: Lin, Daniel, McCarthy, Brian M., Kurtz, Scott D., Kresse, James M.
• Primary Examiner(s): Coles, Sr., Edward L.
• Application Number:
  US07/369,292
• Time in Patent Office: 524 Days
• Field of Search: 358/426, 358/428, 358/429, 358/433, 382/56, 341/51, 375/122
• US Class Current: 358/426.08
• CPC Class Codes: H04B 1/66 for reducing bandwidth of signals; for improving efficiency of transmission H04B1/68 takes precedence
• CPC Class Codes: H04N 1/41 Bandwidth or redundancy reduction by scanning H04N1/17 ; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00

Abstract

A telecommunication system and method for communicating communication signals between various stations over a selected carrier medium. An improved encoder and method is provided for compressing a communication signal into a selectively formatted encoded signal to facilitate its transmission over the selected carrier medium. The method is particularly useful for encoding fax and modem data signals which do not exhibit the harmonics of a voice signal. A decoder and method for reconstruction of the encoded signal are also provided.

Claims

1. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved encoding method comprising:

transforming the communication signal into two separate components including;

determining the approximate center frequency Ω

of the communication signal,

mixing the communication signal with cos(Ω

t) to produce an in-phase component, and

mixing the communication signal with sin(Ω

t) to produce a quadrature component;

quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter; and

formatting the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system.

2. An encoding method according to claim 1 further comprising:

filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above a selected level.

3. An encoding method according to claim 2 further comprising:

decimating the respective filtered in-phase and quadrature components by a selected factor M prior to quantizing.

4. An encoding method according to claim 3 further comprising:

interpolating the communication signal by a selected factor M'"'"' prior to mixing the communication signal with cos(Ω

t) and sin(Ω

t) to produce respective in-phase and quadrature components.

5. An encoding method according to claim 4 wherein:

the approximate center frequency Ω

of the communication signal is determined by determining the type of communication signal and assigning a preselected value Ω

to based upon the type of signal.

6. An encoding method according to claim 5 wherein:

the preselected value assigned to Ω

is 1800, M is selected to be 20, M'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined to be a fax signal;

the preselected value assigned to Ω

is 1200, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

is 2400, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined to be an answering band signal of a split band modem signal.

7. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved method of encoding fax signals comprising:

transforming the fax signal into two separate components including;

mixing the fax signal with cos(1800t) to produce an in-phase component, and

mixing the fax signal with sin(1800t) to produce a quadrature component;

quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter; and

formatting the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system.

8. An encoding method according to claim 7 further comprising:

filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above 1400 Hz.

9. An encoding method according to claim 8 further comprising:

interpolating the fax signal by a factor of 3 prior to mixing the fax signal to produce in-phase and quadrature components; and

decimating the respective filtered in-phase and quadrature components by a factor of 10 prior to quantizing.

10. An encoding method according to claim 9 wherein the in-phase and quadrature components are quantized into 6 levels.

11. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved method of encoding split band modem signals comprising:

transforming the modem signal into two separate components including;

determining the band of the modem signal,

mixing the modem signal with cos(Ω

t) to produce an in-phase component and mixing the modem signal with sin(Ω

t) to produce a quadrature component where Ω

is 1200 for an originating band signal and Ω

is 2400 for an answering band signal;

quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter; and

formatting the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system.

12. An encoding method according to claim 11 further comprising:

filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above 700 Hz.

13. An encoding method according to claim 12 further comprising:

interpolating the modem signal by a factor of 3 prior to mixing the modem signal to produce in-phase and quadrature components; and

decimating the respective filtered in-phase and quadrature components by a factor of 20 prior to quantizing.

14. An encoding method according to claim 11 wherein the in-phase and quadrature components are quantized into 32 levels.

15. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal comprised of quantized in-phase and quadrature signals and a gain component to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved decoding method comprising:

separating the quantized in-phase and quadrature signals and gain component of a compressed encoded signal received over the selected carrier medium of the communication system;

determining the approximate center frequency Ω

of the communication signal being decoded;

reconstructing the respective in-phase and quadrature signals by quantize decoding in accordance with the gain component;

mixing the reconstructed in-phase signal with cos(Ω

t);

mixing the reconstructed quadrature signal with sin(Ω

t); and

summing the two mixed, reconstructed signals to reproduce the decoded, decompressed communication signal.

16. A decoding method according to claim 15 wherein:

the approximate center frequency Ω

of the communication signal is determined by determining the type of communication signal and assigning a preselected value to Ω

based upon the type of signal.

17. A decoding method according to claim 16 wherein:

the preselected value assigned to Ω

is 1800 when the communication signal is determined to be a fax signal;

the preselected value assigned to Ω

is 1200 when the communication signal is determined to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

is 2400 when the communication signal is determined to be an answering band signal of a split band modem signal.

18. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal comprised of quantized in-phase and quadrature signals and a gain component to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved method of decoding compressed encoded fax signals comprising:

separating the quantized in-phase and quadrature signals and gain component of a compressed encoded fax signal received over the selected carrier medium of the communication system;

reconstructing the respective in-phase and quadrature signals by quantize decoding in accordance with the gain component;

mixing the reconstructed in-phase signal with cos(1800t);

mixing the reconstructed quadrature signal with sin(1800t); and

summing the two mixed, reconstructed signals to reproduce the decoded, decompressed fax signal.

19. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal comprised of quantized in-phase and quadrature signals and a gain component to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved method of decoding compressed encoded modem signals comprising:

separating the quantized in-phase and quadrature signals and gain component of a compressed encoded modem signal received over the selected carrier medium of the communication system;

reconstructing the respective in-phase and quadrature signals by quantize decoding in accordance with the gain component;

determining the band of the modem signal,

mixing the reconstructed in-phase signal with cos(Ω

t) and mixing the reconstructed quadrature signal with sin(Ω

t) where Ω

is 1200 for an originating band signal and Ω

is 2400 for an answering band signal; and

summing the two mixed, reconstructed signals to reproduce the decoded, decompressed modem signal.

20. In a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, an improved communication method comprising:

transforming the communication signal into two separate components including;

determining the approximate center frequency Ω

of the communication signal,

mixing the communication signal with cos(Ω

t) to produce an in-phase component, and

mixing the communication signal with sin(Ω

t) to produce a quadrature component;

quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter;

formatting the quantized signals and gain component to thereby produce a compressed encoded signal;

transmitting the compressed encoded signal over the selected carrier medium of the communication system;

separating the quantized in-phase and quadrature signals and gain component of the compressed encoded signal received over the selected carrier medium of the communication system;

reconstructing the respective in-phase and quadrature signals by quantize decoding in accordance with the gain component;

mixing the reconstructed in-phase signal with cos(Ω

t);

mixing the reconstructed quadrature signal with sin(Ω

t); and

summing the two mixed, reconstructed signals to reproduce the decoded, decompressed communication signal.

21. A method according to claim 20 further comprising:

filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above a selected level; and

filtering each of the mixed, reconstructed signals prior to summing to remove from each component'"'"'s frequency domain all frequencies above said selected filtering level.

22. A method according to claim 21 further comprising:

decimating the respective filtered in-phase and quadrature components by a selected factor M prior to quantizing; and

interpolating the reconstructed in-phase and quadrature signals by M prior to mixing.

23. A method according to claim 22 further comprising:

interpolating the communication signal by a selected factor M'"'"' prior to mixing the communication signal with cos(Ω

t) and sin(Ω

t) to produce respective in-phase and quadrature components; and

decimating the respective mixed and filtered reconstructed in-phase and quadrature signals by M'"'"' prior to summing.

24. A method according to claim 23 wherein:

the approximate center frequency Ω

of the communication signal is determined by determining the type of communication signal and assigning a preselected value to Ω

based upon the type of signal.

25. A method according to claim 24 wherein:

the preselected value assigned to Ω

is 1800, M is selected to be 20, M'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined to be a fax signal;

the preselected value assigned to Ω

is 1200, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

is 2400, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined to be an answering band signal of a split band modem signal.

26. A signal compression encoder for a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, the encoder comprising:

means for transforming a communication signal into two separate components including;

means for determining the approximate center frequency Ω

of the communication signal,

means for mixing the communication signal with cos(Ω

t) to produce an in-phase component, and

means for mixing the communication signal with sin(Ω

t) to produce a quadrature component;

means for quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter

formatting means for multiplexing the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system.

27. An encoder according to claim 26 further comprising:

means for filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above a selected level.

28. An encoder according to claim 27 further comprising:

means for decimating the respective filtered in-phase and quadrature components by a selected factor M prior to quantizing.

29. An encoder according to claim 28 further comprising:

means for interpolating the communication signal by a selected factor M'"'"' prior to mixing the communication signal with cos(Ω

t) and sin(Ω

t) to produce respective in-phase and quadrature components.

30. An encoder according to claim 29 wherein:

said means for determining the approximate center frequency Ω

of the communication signal determines the type of communication signal and assigns preselected values to Ω

, M, M'"'"', the level of filtering and the number of quantization levels based upon the type of signal.

31. An encoder according to claim 30 wherein:

the preselected value assigned to Ω

is 1800, to M is 20, to M'"'"' is 3, to the filtering level is 1400 Hz and to the number of quantization levels is 6 for when the communication signal is determined to be a fax signal;

the preselected value assigned to Ω

is 1200, to M is 10, to M'"'"' is 3, to the filtering level is 700 Hz and to the number of quantization levels is 32 for when the communication signal is determined to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

is 2400, to M is 10, to M'"'"' is 3, to the filtering level is 700 Hz and to the number of quantization levels is 32 for when the communication signal is determined to be an originating band signal of a split band modem signal.

32. A signal decompression decoder for a telecommunication system for communicating communication signals between various locations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal comprised of quantized in-phase and quadrature signals and a gain component to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, the decoder comprising:

format decoding means for separating the quantized in-phase and quadrature signals and gain component of a compressed encoded signal received over the selected carrier medium of the communication system;

means for determining the approximate center frequency Ω

of the communication signal being decoded;

quantize decoding means for reconstructing the respective in-phase and quadrature signals in accordance with the gain component;

means for mixing the reconstructed in-phase signal with cos(Ω

t);

means for mixing the reconstructed quadrature signal with sin(Ω

t); and

means for summing the two mixed, reconstructed signals to reproduce the decoded, decompressed communication signal.

33. A decoder according to claim 32 wherein:

said means for determining the approximate center frequency Ω

of the communication signal determines the type of communication signal and assigns a preselected value to Ω

based upon the type of signal.

34. An encoder according to claim 33 wherein:

the preselected value assigned to Ω

is 1800 when the communication signal is determined to be a fax signal;

the preselected value assigned to Ω

is 1200 when the communication signal is determined to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

is 2400 when the communication signal is determined to be an answering band signal of a split band modem signal.

35. A communication station for a telecommunication system for communicating communication signals between various stations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, the communication station comprising:

at least one signal compression encoder including;

means for transforming a communication signal into two separate components including;

means for determining the approximate center frequency Ω

of the communication signal,

means for mixing the communication signal with cos(Ω

t) to produce an in-phase component, and

means for mixing the communication signal with sin(Ω

t) to produce a quadrature component;

means for quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter

formatting means for multiplexing the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system; and

at least one signal decompression decoder including;

format decoding means for separating the quantized in-phase and quadrature signals and gain component of a compressed encoded signal received over the selected carrier medium of the communication system;

means for determining the approximate center frequency Ω

'"'"' of the communication signal being decoded;

quantize decoding means for reconstructing the respective in-phase and quadrature signals in accordance with the gain component and a selected number of quantization levels;

means for mixing the reconstructed in-phase signal with cos(Ω

'"'"'t);

means for mixing the reconstructed quadrature signal with sin(Ω

'"'"'t); and

means for summing the two mixed, reconstructed signals to reproduce the decoded, decompressed communication signal.

36. A plurality of communication stations according to claim 35 comprising a telecommunication system wherein one of said stations is a base station.

37. A communication station according to claim 35 wherein:

said at least one signal compression encoder further comprises means for filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above a selected level; and

said at least one signal compression decoder further comprises means for filtering each of the mixed, reconstructed signals prior to summing to remove from each component'"'"'s frequency domain all frequencies above a selected filtering level.

38. A communication station according to claim 37 wherein:

said at least one signal compression encoder further comprises means for decimating the respective filtered in-phase and quadrature components by a selected factor M prior to quantizing; and

said at least one signal compression decoder further comprises means for interpolating the reconstructed in-phase and quadrature signals by m prior to mixing.

39. A communication station according to claim 38 wherein:

said at least one signal compression encoder further comprises means for interpolating the communication signal by a selected factor M'"'"' prior to mixing the communication signal with cos(Ω

t) and sin(Ω

t) to produce respective in-phase and quadrature components; and

said at least one signal compression decoder further comprises means for decimating the respective mixed and filtered reconstructed in-phase and quadrature signals by m'"'"' prior to summing.

40. A communication station according to claim 39 wherein:

said at least one encoder'"'"'s means for determining the approximate center frequency Ω

of the communication signal determines the type of communication signal and assigns preselected values to Ω

, M, M'"'"', the level of filtering and the number of quantization levels based upon the type of signal; and

said at least one decoder'"'"'s means for determining the approximate center frequency Ω

'"'"' of the communication signal determines the type of communication signal and assigns preselected values to Ω

'"'"', m, m'"'"', the level of filtering and the number of quantization levels based upon the type of signal.

41. A communication station according to claim 40 wherein:

the preselected value assigned to Ω

is 1800, M is selected to be 20, M'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined by said encoder to be a fax signal;

the preselected value assigned to Ω

is 1200, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said encoder to be an originating band signal of a split band modem signal;

the preselected value assigned to Ω

is 2400, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said encoder to be an answering band signal of a split band modem signal;

the preselected value assigned to Ω

'"'"' is 1800, m is selected to be 20, m'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined by said decoder to be a fax signal;

the preselected value assigned to Ω

'"'"' is 1200, m is selected to be 10, m'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said decoder to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

'"'"' is 2400, m is selected to be 10, m'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said decoder to be an answering band signal of a split band modem signal.

42. A plurality of communication stations according to claim 41 comprising a telecommunication system wherein one of said stations is a base station.

43. A communication station for a telecommunication system for communicating communication signals between various stations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, the communication station comprising:

a plurality of signal compression encoders and signal decompression decoders for encoding and decoding a selected type of signal;

means for selecting one of said encoders for processing a signal to be transmitted in accordance with the signal type;

means for selecting one of said decoders for processing a received signal in accordance with the signal type;

at least one of said signal compression encoders including;

means for transforming a communication signal into two separate components including;

means for mixing the communication signal with cos(Ω

t) to produce an in-phase component where Ω

is a preselected value, and

means for mixing the communication signal with sin(Ω

t) to produce a quadrature component;

means for quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter

formatting means for multiplexing the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system; and

at least one of said signal decompression decoders including;

format decoding means for separating the quantized in-phase and quadrature signals and gain component of a compressed encoded signal received over the selected carrier medium of the communication system;

quantize decoding means for reconstructing the respective in-phase and quadrature signals in accordance with the gain component and a selected number of quantization levels;

means for mixing the reconstructed in-phase signal with cos(Ω

'"'"'t) where Ω

'"'"' is a preselected value;

means for mixing the reconstructed quadrature signal with sin(Ω

'"'"'t); and

means for summing the two mixed, reconstructed signals to reproduce the decoded, decompressed communication signal.

44. A plurality of communication stations according to claim 43 comprising a telecommunication system wherein one of said stations is a base station.

45. A communication station according to claim 43 wherein:

said at least one signal compression encoder further comprises means for filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above a selected level; and

said at least one signal compression decoder further comprises means for filtering each of the mixed, reconstructed signals prior to summing to remove from each component'"'"'s frequency domain all frequencies above a selected filtering level.

46. A communication station according to claim 45 wherein:

said at least one signal compression encoder further comprises means for decimating the respective filtered in-phase and quadrature components by a selected factor M prior to quantizing; and

said at least one signal compression decoder further comprises means for interpolating the reconstructed in-phase and quadrature signals by m prior to mixing.

47. A communication station according to claim 46 wherein:

said at least one signal compression encoder further comprises means for interpolating the communication signal by a selected factor M'"'"' prior to mixing the communication signal with cos(Ω

t) and sin(Ω

t) to produce respective in-phase and quadrature components; and

said at least one signal compression decoder further comprises means for decimating the respective mixed and filtered reconstructed in-phase and quadrature signals by m'"'"' prior to summing.

48. A communication station according to claim 47 wherein:

said encoder selecting means determines the type of communication signal and assigns to said at least one encoder preselected values for Ω

, M, M'"'"', the level of filtering and the number of quantization levels based upon the type of signal; and

said decoder selecting means determines the type of communication signal and assigns to said at least one decoder preselected values for Ω

'"'"', m, m'"'"', the level of filtering and the number of quantization levels based upon the type of signal.

49. A communication station according to claim 48 wherein:

the preselected value assigned to Ω

is 1800, M is selected to be 20, M'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined by said encoder selecting means to be a fax signal;

the preselected value assigned to Ω

is 1200, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said encoder selecting means to be an originating band signal of a split band modem signal;

the preselected value assigned to Ω

is 2400, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said encoder selecting means to be an answering band signal of a split band modem signal;

the preselected value assigned to Ω

'"'"' is 1800, m is selected to be 20, m'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined by said decoder selecting means to be a fax signal;

the preselected value assigned to Ω

'"'"' is 1200, m is selected to be 10, m'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said decoder selecting means to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

'"'"' is 2400, m is selected to be 10, m'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined by said decoder selecting means to be an answering band signal of a split band modem signal.

50. A plurality of communication stations according to claim 49 comprising a telecommunication system wherein one of said stations is a base station.

51. A telecommunication system for communicating communication signals between various stations over a selected carrier medium wherein the communication signal is compressed into a selectively formatted encoded signal to facilitate its transmission over the selected carrier medium and the communication signal is reconstructed after reception, the system comprising:

a first station having at least one signal compression encoder including;

means for transforming a communication signal into two separate components including;

means for determining the approximate center frequency Ω

of the communication signal,

means for mixing the communication signal with cos(Ω

t) to produce an in-phase component, and

means for mixing the communication signal with sin(Ω

t) to produce a quadrature component;

means for quantizing each separated signal component into a selected number of levels thereby encoding the signal components into quantized signals and an associated quantization gain parameter

formatting means for multiplexing the quantized signals and gain component to thereby produce a compressed encoded signal for transmission over the selected carrier medium of the communication system; and

a second station for receiving the compressed encoded signal from said first station having at least one signal decompression decoder including;

format decoding means for separating the quantized in-phase and quadrature signals and gain component of a compressed encoded signal received over the selected carrier medium of the communication system;

means for determining the approximate center frequency Ω

of the communication signal being decoded;

quantize decoding means for reconstructing the respective in-phase and quadrature signals in accordance with the gain component;

means for mixing the reconstructed in-phase signal with cos(Ω

t);

means for mixing the reconstructed quadrature signal with sin(Ω

t); and

means for summing the two mixed, reconstructed signals to reproduce the decoded, decompressed communication signal.

52. A telecommunication system according to claim 51 wherein on of said stations is a base station.

53. A telecommunication system according to claim 52 wherein:

said at least one signal compression encoder further comprises means for filtering each of the in-phase and quadrature components prior to quantizing to remove from each component'"'"'s frequency domain all frequencies above a selected level; and

said at least one signal compression decoder further comprises means for filtering each of the mixed, reconstructed signals prior to summing to remove from each component'"'"'s frequency domain all frequencies above said selected filtering level.

54. A telecommunication system according to claim 53 wherein:

said at least one signal compression encoder further comprises means for decimating the respective filtered in-phase and quadrature components by a selected factor M prior to quantizing; and

said at least one signal compression decoder further comprises means for interpolating the reconstructed in-phase and quadrature signals by M prior to mixing.

55. A telecommunication system according to claim 54 wherein:

said at least one signal compression encoder further comprises means for interpolating the communication signal by a selected factor M'"'"' prior to mixing the communication signal with cos(Ω

t) and sin(Ω

t) to produce respective in-phase and quadrature components; and

said at least one signal compression decoder further comprises means for decimating the respective mixed and filtered reconstructed in-phase and quadrature signals by M'"'"' prior to summing.

56. A telecommunication system according to claim 55 wherein:

said means for determining the approximate center frequency Ω

of the communication signal determines the type of communication signal and assigns preselected values to Ω

, M, M'"'"', the level of filtering and the number of quantization levels based upon the type of signal.

57. A telecommunication system according to claim 56 wherein:

the preselected value assigned to Ω

is 1800, M is selected to be 20, M'"'"' is selected to be 3, the filtering level is selected to be 1400 Hz and the in-phase and quadrature components are quantized into 6 levels when the communication signal is determined to be a fax signal;

the preselected value assigned to Ω

is 1200, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined to be an originating band signal of a split band modem signal; and

the preselected value assigned to Ω

is 2400, M is selected to be 10, M'"'"' is selected to be 3, the filtering level is selected to be 700 Hz and the in-phase and quadrature components are quantized into 32 levels when the communication signal is determined to be an answering band signal of a split band modem signal.