Signal processing system

• US 3,909,721 A
• Filed: 02/28/1974
• Issued: 09/30/1975
• Est. Priority Date: 01/31/1972
• Status: Expired due to Term

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Herbert Gish, Julian J. Bussgang
• Inventors: Bussgang, Julian J., Gish, Herbert
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/446,782
• Time in Patent Office: 579 Days
• Field of Search: 340/146.1R,146.1A,146.1B,146.1BA,146.1BE,206,207,347AD 179/15.55R 178/66R,67,DIG.3 325/38R,39,40,41,30
• US Class Current: 375/280
• CPC Class Codes: H03M 13/35 Unequal or adaptive error protection, e.g. by providing a different level of protection according to significance of source information or by adapting the coding according to the change of transmission channel characteristics
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• 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

Abstract

A signal processing system for processing an analog signal which has been quantized by suitable sampling techniques, different portions of the quantized data information having different significances. The processing is accomplished so as to improve the overall error characteristics of the system wherein the quantized data information is encoded for transmission, the quantized data being selectively handled in the encoding process so that the more significant quantized data information is encoded in such a manner that it is afforded more protection from error during transmission than the less significant quantized data information. A receiver system appropriately decodes the encoded transmitted information by selectively reforming the arrangement of the quantized data information in conformity with the selective arrangement provided in the transmitter encoding process. The reformed quantized data information is then converted to an analog signal representing the analog signal processed by the transmitting system.

Claims

1. A transmitter signal processing system for processing an analog signal for transmission over a communication channel, said transmitter signal processing system comprising means responsive to said analog signal for producing quantized data information representing periodic samples of said analog signal, different portions of said quantized data information having different significances;

processing means responsive to said quantized data information for producing a selectively arranged encoded information signal, said processing means including means for selectively arranging said quantized data information in accordance with said different significances thereof;

means for encoding said selectively arranged quantized data information to produce said selectively arranged encoded information signal in a manner so as to provide the more significant quantized data information with more protection from eror than the less significant quantized data information;

means responsive to said selectively arranged encoded information signal for re-arranging said signal in accordance with different significances to provide a re-arranged encoded information signal capable of being selectively protected by a modulation process;

modulation means respOnsive to said re-arranged encoded information signal for producing a modulated signal in which said re-arranged encoded information is provided with said selective protection by said modulation process; and

means responsive to said modulated signal for transmitting said signal over said communication channel.

2. A processing system in accordance with claim 1 wherein said encoding means is a redundant encoding means for encoding said selectively arranged quantized data information so that said encoded data information has differing degrees of redundancy, the redundantly encoded data information being encoded so that more significant data information thereof is provided with greater redundancy and less significant data information thereof is provided with lesser redundancy.

3. A signal processing system in accordance with claim 2 wherein said encoding and selective re-arranging means comprise a cross-stream tapered matrix encoder arranged so that said selectively arranged quantized data information is encoded and further re-arranged in said selected format in accordance with a pre-selected operating matrix.

4. A signal processing system in accordance with claim 3 wherein said encoding and selective re-arranging means includes a plurality of shift registers each responsive to a selected portion of said input data information to provide output data information representing said selected portion of said input data information in undelayed form, in a form delayed by a time unit D, and in a form delayed by a time unit D2, said shift registers being arranged to produce encoded and selectively re-arranged data information in accordance with the following pre-selected operating matrix:

5. A signal processing system in accordance with claim 2 wherein said encoding means includes a plurality of separate encoders for providing encoded information having redundant characteristics, the redundant characteristics of at least some of said encoders being different;

said encoders each being responsive to separate portions of said selectively arranged quantized data information for producing said selected groups of encoded data information therefrom, said separate portions thereof having the greater significance being provided with greater encoded redundancy and said separate portions thereof having lesser significance being provided with lesser encoded redundancy.

6. A receiver signal processing system for processing a received signal which has been transmitted over a communication channel from a transmitter signal processing system which received signal is a modulated information signal representing an analog signal which has been quantized, selectively arranged and encoded by said transmitter system and which selectively arranged encoded information signal being further re-arranged in accordance with a selected format and modulated by said transmitter system, said receiver system comprising means for synchronizing the operation of said receiver system with the operation of said transmitter system;

means responsive to said received signal for demodulating said received signal to produce a demodulated re-arranged encoded information signal;

means responsive to said demodulated re-arranged encoded information signal for converting said information signal into a form corresponding to that of said selectively arranged encoded information signal in said transmitter signal processing system;

means for decoding said re-formed selectively arranged encoded information signal and for further re-forming said decoded signal in conformity with said quantized data information in said transmitter signal processing system; and

means responsive to said decoded anD further re-formed information signal for producing an analog signal substantially representing the analog signal processed by said transmitter signal processing system.

7. A transmitter signal processing system for processing an analog signal for transmission over a communication channel, said transmitter signal processing system comprising means responsive to said analog signal for producing quantized data information in parallel form representative of periodic samples of said analog signal, different portions of said quantized data information having different significances;

means for converting said quantized data parallel information to series form; and

means responsive to said quantized data information in series form for selectively re-arranging said series information in accordance with said different signficances;

phase modulating means for producing a phase modulated signal wherein prescribed phases of said modulated signal are selected to represent prescribed quantized data combinations and wherein different bit positions in said prescribed data combinations are afforded different protections from error;

means for selectively feeding said selectively arranged quantized data information to said phase modulating means so that the more significant portions of said selectively re-arranged data information are placed in those positions of said phase modulating means having the greater protection from error; and

means for transmitting said phase modulated signal over said communication channel.

8. A transmitter signal processing system in accordance with claim 7 wherein each sample of said quantized data information in parallel form includes n data bits, said bits having differing significances;

and said quantized data information in series form includes n streams of data bits, each stream containing data bits from successive samples having the same significance.

9. A signal processing system in accordance with claim 8 wherein said selective re-arranging means provides groups of n/2-bit data streams wherein alternating ones of said data bits of said n-bit data stream are contained in one of said n/2-bit data groups and intervening ones of said data bits of said n-bit data streams are contained in the other of said n/2-bit data

10. A signal processing system in accordance with claim 9 wherein said phase modulating means includes a phase modulator arranged to provide 2 n/2 prescribed phases representative of selected n/2-bit combinations, said n/2-bit combination being selected so that said combinations in adjacent phase positions differ in only one bit position and said selected n/2-bit combinations being further arranged so that successive data bit positions therein are progressively more susceptible to error.

11. A signal processing system in accordance with claim 10 wherein n equals 8.

12. A transmitter signal processing system in accordance with claim 7 wherein said means for producing said information in parallel form further includes storage means for storing one or more periodic samples of said analog signal to provide a combined signal containing quantized data information from two or more of said periodic samples in parallel form for feeding to said processing means.

13. A receiver signal processing system for processing a received signal which has been transmitted over a communication channel from a transmitter signal processing system which received signal is a phase modulated quantized data information signal representing an analog signal which has been quantized in accordance with a first arrangement, selectively re-arranged, and modulated by said transmitter system in accordance with said selective re-arrangement, said receiver system comprising means for synchronizing the operation of said receiver system with the operation of said transmitter system;

detector means responsive to said receivEd signal for phase detecting said received signal to produce a demodulated quantized data information signal;

means responsive to said demodulated quantized data information signal for selectively re-forming said demodulated quantized data information in conformity with said first arrangement of the quantized data information as provided for in said transmitter signal processing means; and

means responsive to said re-formed quantized data information for producing an analog signal substantially representing the analog signal processed by said transmitter signal processing system.

14. A receiver signal processing system for processing a received signal which has been transmitted over a communication channel from a transmitter signal processing system which received signal is a modulated signal representing an analog signal which has been quantized, redundantly encoded into selected groups of redundantly encoded data information in accordance with different degrees of redundancy, selectively rearranged, and modulated by said transmitter system, said receiver signal processing system comprising receiving and demodulating means for demodulating said received signal to produce a demodulated information signal;

means for reforming said demodulated information signal to produce a redundantly encoded information signal;

means for decoding said redundantly encoded information signal in accordance with said different degrees of redundancy to produce decoded quantized data information;

means responsive to said quantized data information for producing an analog signal substantially representing the analog signal processed by said transmitter signal processing system.

15. A receiver signal processing system for processing a received signal which has been transmitted from a transmitter signal processing system, which received signal is a modulated signal representing an analog signal processed by said transmitter system in accordance with an encoded form, said receiver signal processing system comprising means for receiving and demodulating said received signal;

means responsive to said received signal for quantizing said received signal to produce encoded quantized data information;

means responsive to said encoded quantized data information for forming said data information into said encoded form;

means for decoding said encoded form of said data information to produce decoded quantized data information, said decoding means including a matrix syndrome decoder for producing decoded quantized data information susceptible of errors;

means for correcting errors in said decoded data information to produce corrected data information; and

means responsive to said corrected data information for producing an analog signal substantially representing the analog signal processed by said transmitter signal processing system.

16. A receiver signal processing system in accordance with claim 15 wherein said matrix syndrome decoder includes a syndrome calculator for operating on said encoded form of said received data information to produce quantized data information, a first portion of which represents uncorrected data information in said encoded form and a second portion of which represents syndromes of said uncorrected data information;

means for storing said syndromes to produce quantized data information signals having error patterns determined by the errors in said received data information;

means for producing error correction signals in response to said error pattern signals;

means responsive to said uncorrected data information and to said error correction signal for producing said corrected data information.

17. A receiver signal processing system in accordance with claim 16 wherein said syndrome calculator includes a plurality of shift registers each responsive to a selected portion of said encoded form of said received data information to provide output data information representing said selected portion of said received data information in undelayed form, in a form delayed by a time unit D, in a form delayed by a time unit D2, and in a form delayed by a time unit D3, said shift registers being arranged to produce said uncorrected data information and said syndromes in accordance with the following pre-selected inverse operating matrix:

18. A receiver signal processing system in accordance with claim 16 wherein said syndrome storing means includes a plurality of shift registers each responsive to a selected portion of said syndromes to provide stored output data information representing said selection portions in undelayed form, in a form delayed by a time unit D, in a form delayed by a time unit D2, and in a form delayed by a time unit D3, said shift registers being arranged to produce stored date in a pattern determined by the presence of an error in said received signal.

19. A receiver signal processing system for processing a received signal which has been transmitted over a communication channel from a transmitter signal processing system which received signal is a modulated information signal representing an analog signal which has been quantized, selectively arranged and encoded by a plurality of separate redundant encoders of said transmitter system in accordance with different redundancy characteristics to produce selected groups of redundantly encoded data information and which selected groups have been further re-arranged in accordance with a selected format to produce a redundantly encoded and re-arranged signal, said receiver signal processing system comprising receiving and demodulating means for demodulating said received signal to produce a demodulated redundantly encoded and selectively re-arranged information signal in series form;

means for re-forming said series information signal into parallel form in accordance with said selected format to produce said selected groups of redundantly encoded parallel data information;

a plurality of separate decoders for providing decoded information, the decoding characteristics of at least some of said decoders being adapted to decode information having said different redundancy characteristics;

said decoders being arranged to be responsive to said selected groups having different redundancy characteristics for separately decoding said selected groups thereof to produce decoded selectively arranged quantized data information in parallel form; and

means for converting said decoded selectively arranged quantized data information to analog form to provide an analog signal substantially representing the analog signal processed by said transmitter signal processing system.

20. A transmitter signal processing system for processing an analog signal for transmission over a communications channel, said transmitter signal processing system comprising means responsive to said analog signal for producing quantized data information in binary form representing periodic samples of said analog signal, said quantized data producing means being arranged to provide a plurality of parallel data bit streams, the information in different data bit streams having different significances;

means for converting a first selected number of said parallel data bit streams containing more significant information from parallel to series form;

first means for redundantly encoding said selected number of series data bit streams to provide a first number of parallel encoded bit streams greater than said first selected number Thereof;

second means for encoding a second selected number of said parallel data bit streams containing less significant information to provide a second number of parallel encoded data bit streams less than said second selected number thereof, said encoding means converting said data streams from binary to multilevel form;

means for selectively feeding said second selected number of parallel data bit streams to said second encoding means so that the data bit streams thereof having the more significant information are placed in positions having the greater protection from error;

means responsive to said first number of parallel encoded data bit streams, said second number of parallel encoded data bit streams, and a third number of non-encoded parallel data bit streams for converting all of said data bit streams from parallel to series form;

means for modulating said series data bit streams and for transmitting said modulated signal over a communication channel.

21. A transmitter signal processing system in accordance with claim 20 wherein said second encoding means converts said second selected number of data bit streams from binary to quaternary form and wherein the total number of said first number of parallel encoded data bit streams, said second number of parallel encoded data bit streams, and said third number of parallel non-encoded data bit streams is equal to the number of parallel data bit streams provided by said quantized data information producing means.

22. A receiver signal processing system for processing a received signal which has been transmitted over a communication channel from the transmitter signal processing system of claim 20, said receiver system comprising means for demodulating said received signal to provide quantized data information in series form;

means for converting said received quantized data information from series form to a plurality of data bit streams in parallel form;

first decoding means for decoding a first selected number of said parallel data bit streams corresponding to said redundantly encoded data bit streams of said transmitted signal to produce a first number of decoded parallel data bit streams;

second decoding means for decoding a second selected number of said parallel data bit streams corresponding to said multilevel encoded data bit streams of said transmitted signal to produce a second number of decoded parallel data bit streams;

means responsive to said first number of parallel decoded data bit streams, said second number of parallel decoded data bit streams, and a third number of parallel non-decoded data bit streams corresponding to said parallel non-encoded data bit streams of said transmitted signal to produce an analog signal corresponding to the analog signal processed by said transmitter signal processing system.

23. A receiver signal processing system in accordance with claim 22 wherein said analog signal producing means includes a low pass filter means.