Non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation)
View Patent ↗Non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation). A non-systematic and non-linear PC-TCM code is presented that provides quite comparable performance to turbo encoding using only systematic and linear trellis codes (e.g., convolutional codes). The non-systematic and non-linear PC-TCM described herein may be modified to support a wide variety of code rates (e.g., rate 2/3, 5/6, 8/9, and 3/4 among other rates) and also a wide modulation types (e.g., 8 PSK (8 Phase Shift Key) and 16 QAM (16 Quadrature Amplitude Modulation) among other modulation types). In one embodiment, a non-systematic and non-linear PC-TCM presented herein comes to within approximately 0.15 dB of a systematic and linear turbo code. A design approach is presented that allows for the design of such non-systematic and non-linear PC-TCM codes and several exemplary embodiments are also presented that have been designed according to these presented principles.
1. A non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation) code design method, the method comprising:
for a trellis, identifying a fixed output state distribution and a plurality of fixed state transitions;
for the trellis, identifying a corresponding input state distribution to support non-systematic and non-linear trellis encoding using the trellis;
identifying a plurality of possible non-systematic and non-linear PC-TCM encoders capable of performing the non-systematic and non-linear trellis encoding using the trellis according to the identified, corresponding input state distribution, the fixed output state distribution, and the plurality of fixed state transitions;
for each non-systematic and non-linear PC-TCM encoder of the plurality of possible non-systematic and non-linear PC-TCM encoders, identifying a symbol mapper, operable to map output symbols to a corresponding constellation, that provides for a best performance in terms of a lowest BER (Bit Error Rate) for output bits that are grouped into the output symbols;
determining the overall performance of each non-systematic and non-linear PC-TCM encoder of the plurality of possible non-systematic and non-linear PC-TCM encoders in terms of the E b /N 0 (ratio of energy per bit E b to the Spectral Noise Density N 0 ) waterfall parts and corresponding BERs; and
selecting a non-systematic and non-linear PC-TCM encoder of the plurality of possible non-systematic and non-linear PC-TCM encoders that provides the lowest E b /N 0 waterfall part with the lowest BER floor.
2. The method of claim 1 , wherein:
the selected non-systematic and non-linear PC-TCM encoder includes a rate k/k+n upper constituent encoder and a rate k/k+n lower constituent encoder;
input provided to the rate k/k+n lower constituent encoder passes through an interleaver that is operable to perform sub-block interleaving on groups of input bits taken during alternate clock cycles; and
k and n are both integers.
3. The method of claim 2 , wherein:
during alternate clock cycles, the symbol mapper alternatively maps output symbols generated by the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder, respectively.
4. The method of claim 2 , wherein:
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 2/3 constituent encoders, rate 5/6 constituent encoders, rate 8/9 constituent encoders, or rate 3/4 constituent encoders.
5. The method of claim 4 ; wherein:
each of the rate 5/6 constituent encoders and the rate 8/9 constituent encoders is implemented using a rate 2/3 constituent encoder in conjunction with puncturing of at least output bit.
6. The method of claim 5 , wherein:
for the rate 5/6 constituent encoders, the output bits are grouped to simultaneously form 2 separate output symbols of 3 bits each; and
for the rate 8/9 constituent encoders, the output bits are grouped to simultaneously form 3 separate output symbols of 3 bits each.
7. The method of claim 4 , wherein:
the output bits include at least one encoded bit and at least one uncoded bit.
8. The method of claim 2 , wherein:
the trellis is an 8 state trellis;
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 2/3 constituent encoders; and
each of the rate 2/3 upper constituent encoder and the rate 2/3 lower constituent encoder encodes input symbols including 2 bits each and generates output symbols including 3 bits each.
9. The method of claim 1 , wherein:
the selected non-systematic and non-linear PC-TCM encoder is a rate 2/3 non-systematic and non-linear PC-TCM encoder that maps output symbols to an 8 PSK (8 Phase Shift Key) shaped constellation according to the identified symbol mapper;
for a communication channel having a Shannon's limit capacity of approximately 2 bits per second per Hz (Hertz), the lowest E b /N 0 waterfall part of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 3.45 dB (decibels) at a BER of approximately 2×10 −3 and approximately 3.65 db at a BER of approximately 3×10 −7 ; and
the BER floor of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 2×10 −7 and approximately 3×10 −7 .
10. The method of claim 1 , further comprising:
implementing the selected non-systematic and non-linear PC-TCM encoder within at least one of a satellite communication system, an HDTV (High Definition Television) communication system, a cellular communication system, a microwave communication system, a point-to-point communication system, and a uni-directional communication system, a bi-directional communication system, and a one to many communication system.
11. A non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation) code design method, the method comprising:
for a trellis, identifying a fixed output state distribution and a plurality of fixed state transitions;
for the trellis, identifying a corresponding input state distribution to support non-systematic and non-linear trellis encoding using the trellis;
identifying a plurality of possible non-systematic and non-linear PC-TCM encoders capable of performing the non-systematic and non-linear trellis encoding using the trellis according to the identified, corresponding input state distribution, the fixed output state distribution, and the plurality of fixed state transitions;
for each non-systematic and non-linear PC-TCM encoder of the plurality of possible non-systematic and non-linear PC-TCM encoders, identifying a symbol mapper, operable to map output symbols to a corresponding constellation, that provides for a best performance in terms of a lowest BER (Bit Error Rate) for output bits that are grouped into the output symbols;
determining the overall performance of each non-systematic and non-linear PC-TCM encoder of the plurality of possible non-systematic and non-linear PC-TCM encoders in terms of the E b /N 0 (ratio of energy per bit E b to the Spectral Noise Density N 0 ) waterfall parts and corresponding BERs;
selecting a non-systematic and non-linear PC-TCM encoder of the plurality of possible non-systematic and non-linear PC-TCM encoders that provides the lowest E b /N 0 waterfall part with the lowest BER floor;
the selected non-systematic and non-linear PC-TCM encoder includes a rate k/k+n upper constituent encoder and a rate k/k+n lower constituent encoder;
input provided to the rate k/k+n lower constituent encoder passes through an interleaver that is operable to perform sub-block interleaving on groups of input bits taken during alternate clock cycles;
during alternate clock cycles, the symbol mapper alternatively maps output symbols generated by the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder, respectively; and
wherein k and n are both integers.
12. The method of claim 11 , wherein:
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 2/3 constituent encoders, rate 5/6 constituent encoders, rate 8/9 constituent encoders, or rate 3/4 constituent encoders;
each of the rate 5/6 constituent encoders and the rate 8/9 constituent encoders is implemented using a rate 2/3 constituent encoder in conjunction with puncturing of at least output bit;
for the rate 5/6 constituent encoders, the output bits are grouped to simultaneously form 2 separate output symbols of 3 bits each; and
for the rate 8/9 constituent encoders, the output bits are grouped to simultaneously form 3 separate output symbols of 3 bits each.
13. The method of claim 11 , wherein:
the trellis is an 8 state trellis;
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 2/3 constituent encoders; and
each of the rate 2/3 upper constituent encoder and the rate 2/3 lower constituent encoder encodes input symbols including 2 bits each and generates output symbols including 3 bits each.
14. The method of claim 11 , wherein:
the selected non-systematic and non-linear PC-TCM encoder is a rate 2/3 non-systematic and non-linear PC-TCM encoder that maps output symbols to an 8 PSK (8 Phase Shift Key) shaped constellation according to the identified symbol mapper;
for a communication channel having a Shannon's limit capacity of approximately 2 bits per second per Hz (Hertz), the lowest E b /N 0 waterfall part of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 3.45 dB (decibels) at a BER of approximately 2×10 −3 and approximately 3.65 dB at a BER of approximately 3×10 −7 ; and
the BER floor of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 2×10 −7 and approximately 3×10 −7 .
15. The method of claim 11 , further comprising:
implementing the selected non-systematic and non-linear PC-TCM encoder within at least one of a satellite communication system, an HDTV (High Definition Television) communication system, a cellular communication system, a microwave communication system, a point-to-point communication system, and a uni-directional communication system, a bi-directional communication system, and a one to many communication system.
16. A non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation) encoder, the encoder comprising:
a rate k/k+n upper constituent encoder that is operable to receive input bits and to generate a first plurality of output bits there from;
a sub-block interleaver that is operable to interleave input bit sub-blocks selected during alternate clock cycles;
a rate k/k+n lower constituent encoder that is operable to receive the interleaved input bit sub-blocks from the sub-block interleaver and to generate a second plurality of output bits there from;
during alternate clock cycles, a symbol mapper that alternatively selects and groups bits from the first plurality of output bits and the second plurality of output bits to generate a plurality of output symbols;
wherein the symbol mapper maps output symbols from the plurality of output symbols to a constellation according to a symbol mapping;
wherein each of the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder employs a trellis having a fixed output state distribution and a plurality of fixed state transitions;
wherein a corresponding input state distribution for the trellis is identified and employed to support non-systematic and non-linear trellis encoding within each of the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder; and
wherein k and n are both integers.
17. The encoder of claim 16 , wherein:
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 2/3 constituent encoders.
18. The encoder of claim 16 , wherein:
the symbol mapper selects and employs at least one uncoded bit when generating at least one output symbol of the plurality of output symbols.
19. The encoder of claim 16 , wherein:
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 5/6 constituent encoders, rate 8/9 constituent encoders, or rate 3/4 constituent encoders.
20. The encoder of claim 16 , wherein:
each of the rate 5/6 constituent encoders and the rate 8/9 constituent encoders is implemented using a rate 2/3 constituent encoder in conjunction with puncturing of at least output bit.
21. The encoder of claim 20 , wherein:
for the rate 5/6 constituent encoders, the output bits are grouped to simultaneously form 2 separate output symbols of 3 bits each;
for the rate 8/9 constituent encoders, the output bits are grouped to simultaneously form 3 separate output symbols of 3 bits each;
the output symbols of 3 bits each are 8 PSK (8 Phase Shift Key) output symbols; and
the symbol mapper is an 8 PSK symbol mapper.
22. The encoder of claim 16 , wherein:
for the rate 3/4 constituent encoders, three output bits and one uncoded bit are grouped to form an output symbols having 4 bits;
the output symbol having 4 bits is a 16 QAM (16 Quadrature Amplitude Modulation) output symbol; and
the symbol mapper is a 16 QAM symbol mapper.
23. The encoder of claim 16 , wherein:
the trellis is an 8 state trellis;
the rate k/k+n upper constituent encoder and the rate k/k+n lower constituent encoder are both rate 2/3 constituent encoders; and
each of the rate 2/3 upper constituent encoder and the rate 2/3 lower constituent encoder encodes input symbols including 2 bits each and generates output symbols including 3 bits each.
24. The encoder of claim 16 , wherein:
the non-systematic and non-linear PC-TCM encoder is a rate 2/3 non-systematic and non-linear PC-TCM encoder;
the symbol mapper maps output symbols to an 8 PSK (8 Phase Shift Key) shaped constellation;
for a communication channel having a Shannon's limit capacity of approximately 2 bits per second per Hz (Hertz), the lowest E b /N 0 (ratio of energy per bit E b to the Spectral Noise Density N 0 ) waterfall part of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 3.45 dB (decibels) at a BER (Bit Error Rate) of approximately 2×10 −3 and approximately 3.65 dB at a BER of approximately 3×10 −7 ; and
the BER floor of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 2×10 −7 and approximately 3×10 −7 .
25. The encoder of claim 16 , wherein:
the encoder is implemented within at least one of a satellite communication system, an HDTV (High Definition Television) communication system, a cellular communication system, a microwave communication system, a point-to-point communication system, and a uni-directional communication system, a bi-directional communication system, and a one to many communication system.
26. A rate 2/3 non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation) encoder, the encoder comprising:
a rate 2/3 upper constituent encoder that is operable to receive input bits and to generate a first plurality of output bits there from;
a sub-block interleaver that is operable to interleave input bit sub-blocks selected during alternate clock cycles, the input bit sub-blocks being generated from an input bit block;
a rate 2/3 lower constituent encoder that is operable to receive the interleaved input bit sub-blocks from the sub-block interleaver and to generate a second plurality of output bits there from;
during alternate clock cycles, a symbol mapper that alternatively selects and groups bits from the first plurality of output bits and the second plurality of output bits to generate a plurality of output symbols;
the symbol mapper maps output symbols from the plurality of output symbols to a constellation according to a symbol mapping;
wherein each of the rate 2/3 upper constituent encoder and the rate 2/3 lower constituent encoder employs a trellis having a fixed output state distribution and a plurality of fixed state transitions; and
wherein a corresponding input state distribution for the trellis is identified and employed to support non-systematic and non-linear trellis encoding within each of the rate 2/3 upper constituent encoder and the rate 2/3 lower constituent encoder.
27. The encoder of claim 26 , wherein:
the trellis is an 8 state trellis; and
each of the rate 2/3 upper constituent encoder and the rate 2/3 lower constituent encoder encodes input symbols including 2 bits each and generates output symbols including 3 bits each.
28. The encoder of claim 26 , wherein:
the symbol mapper maps output symbols to an 8 PSK (8 Phase Shift Key) shaped constellation;
for a communication channel having a Shannon's limit capacity of approximately 2 bits per second per Hz (Hertz), the lowest E b /N 0 (ratio of energy per bit E b to the Spectral Noise Density N 0 ) waterfall part of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 3.45 dB (decibels) at a BER (Bit Error Rate) of approximately 2×10 −3 and approximately 3.65 dB at a BER of approximately 3×10 −7 ; and
the BER floor of the rate 2/3 non-systematic and non-linear PC-TCM encoder ranges between approximately 2×10 −7 and approximately 3×10 −7 .
29. The encoder of claim 26 , wherein:
the encoder is implemented within at least one of a satellite communication system, an HDTV (High Definition Television) communication system, a cellular communication system, a microwave communication system, a point-to-point communication system, and a uni-directional communication system, a bi-directional communication system, and a one to many communication system.
30. A rate 5/6 and two 8-PSK non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation) encoder, the encoder comprising:
a rate 5/6 upper constituent encoder that is operable to receive input bits and to generate a first plurality of output bits there from;
a sub-block interleaver that is operable to interleave input bit sub-blocks selected during alternate clock cycles, the input bit sub-blocks being generated from an input bit block;
a rate 5/6 lower constituent encoder that is operable to receive the interleaved input bit sub-blocks from the sub-block interleaver and to generate a second plurality of output bits there from;
during alternate clock cycles, a symbol mapper that alternatively selects and groups bits from the first plurality of output bits and the second plurality of output bits to generate a plurality of output symbols;
the symbol mapper maps output symbols from the plurality of output symbols to a constellation according to a symbol mapping;
wherein each of the rate 5/6 upper constituent encoder and the rate 5/6 lower constituent encoder employs a trellis having a fixed output state distribution and a plurality of fixed state transitions;
wherein a corresponding input state distribution for the trellis is identified and employed to support non-systematic and non-linear trellis encoding within each of the rate 5/6 upper constituent encoder and the rate 5/6 lower constituent encoder;
wherein each of the rate 5/6 upper constituent encoder and the rate 5/6 lower constituent encoder includes a rate 2/3 non-systematic encoder;
wherein the trellis is an 8 state trellis;
wherein each of the rate 2/3 non-systematic encoders within the rate 5/6 upper constituent encoder and the rate 5/6 lower constituent encoder encodes input symbols including 2 bits each and generates output symbols including 3 bits each; and
wherein the plurality of output symbols includes 2 output symbols of 3 bits each such that the 2 output symbols are 8 PSK (8 Phase Shift Key) symbols.
31. The encoder of claim 30 , wherein:
the 2 output symbols are simultaneously generated over a 2 clock cycle period; and
at least one output symbol of the 2 output symbols includes at least one uncoded bit.
32. The encoder of claim 30 , wherein:
the 2 output symbols are simultaneously generated over a 2 clock cycle period; and
at least one output bit of the first plurality of output bits and the second plurality of output bits is punctured when forming the 2 output symbols.
33. The encoder of claim 30 , wherein:
the symbol mapper maps the 2 output symbols to an 8 PSK (8 Phase Shift Key) shaped constellation using 2 different constellation mappings;
for a communication channel having a Shannon's limit capacity of approximately 2.5 bits per second per Hz (Hertz), the lowest E b /N 0 (ratio of energy per bit E b to the Spectral Noise Density N 0 ) waterfall part of the rate 5/6 and 2-8PSK non-systematic and non-linear PC-TCM encoder ranges between approximately 5.5 dB (decibels) at a BER (Bit Error Rate) of approximately 2×10 −4 and approximately 5.66 dB at a BER of approximately 2×10 −6 ; and
the BER floor of the rate 5/6 and 2-8PSK non-systematic and non-linear PC-TCM encoder ranges between approximately 1.75×10 −6 and approximately 2×10 −6 .
34. A rate 8/9 and 8-PSK non-systematic and non-linear PC-TCM (Parallel Concatenate Trellis Coded Modulation) encoder, the encoder comprising:
a rate 8/9 upper constituent encoder that is operable to receive input bits and to generate a first plurality of output bits there from;
a sub-block interleaver that is operable to interleave input bit sub-blocks selected during alternate clock cycles, the input bit sub-blocks being generated from an input bit block;
a rate 8/9 lower constituent encoder that is operable to receive the interleaved input bit sub-blocks from the sub-block interleaver and to generate a second plurality of output bits there from;
during alternate clock cycles, a symbol mapper that alternatively selects and groups bits from the first plurality of output bits and the second plurality of output bits to generate a plurality of output symbols;
the symbol mapper maps output symbols from the plurality of output symbols to a constellation according to a symbol mapping;
wherein each of the rate 8/9 upper constituent encoder and the rate 8/9 lower constituent encoder employs a trellis having a fixed output state distribution and a plurality of fixed state transitions;
wherein a corresponding input state distribution for the trellis is identified and employed to support non-systematic and non-linear trellis encoding within each of the rate 8/9 upper constituent encoder and the rate 8/9 lower constituent encoder;
wherein each of the rate 8/9 upper constituent encoder and the rate 8/9 lower constituent encoder includes a rate 2/3 non-systematic encoder;
wherein the trellis is an 8 state trellis;
wherein each of the rate 2/3 non-systematic encoders within the rate 8/9 upper constituent encoder and the rate 8/9 lower constituent encoder encodes input symbols including 2 bits each and generates output symbols including 3 bits each; and
wherein the plurality of output symbols includes 3 output symbols of 3 bits each such that the 3 output symbols are 8 PSK (8 Phase Shift Key) symbols.
35. The encoder of claim 34 , wherein:
the 3 output symbols are simultaneously generated over a 3 clock cycle period; and
at least one output symbol of the 3 output symbols includes at least one uncoded bit.
36. The encoder of claim 34 , wherein:
the 3 output symbols are simultaneously generated over a 3 clock cycle period; and
at least one output bit of the first plurality of output bits and the second plurality of output bits is punctured when forming the 3 output symbols.
37. The encoder of claim 34 , wherein:
the symbol mapper maps the 3 output symbols to an 8 PSK (8 Phase Shift Key) shaped constellation using 3 different constellation mappings;
for a communication channel having a Shannon's limit capacity of approximately 2.66 bits per second per Hz (Hertz), the lowest E b /N 0 (ratio of energy per bit E b to the Spectral Noise Density N 0 ) waterfall part of the rate 8/9 and 3-8PSK non-systematic and non-linear PC-TCM encoder ranges between approximately 6.55 dB (decibels) at a BER (Bit Error Rate) of approximately 4×10 −5 and approximately 6.65 dB at a BER of approximately 1.5×10 −6 ; and
the BER floor of the rate 8/9 and 3-8PSK non-systematic and non-linear PC-TCM encoder ranges between approximately 1×10 −6 and approximately 15×10 −6 .