Transmitters incorporating uniform and non-uniform constellations with rings
Communication systems are described that use unequally spaced constellations that have increased capacity compared to conventional constellations operating within a similar SNR band. One embodiment is a digital communications system including a transmitter transmitting signals via a communication channel, the transmitter including a coder capable of receiving user bits and outputting encoded bits at a rate, a mapper capable of mapping encoded bits to symbols in a constellation, and a modulator capable of generating a modulated signal for transmission via the communication channel using symbols generated by the mapper, wherein the constellation is unequally spaced and characterizable by assignment of locations and labels of constellation points to maximize parallel decode capacity of the constellation at a given signal-to-noise ratio so that the constellation provides a given capacity at a reduced signal-to-noise ratio compared to a uniform constellation that maximizes the minimum distance between constellation points of the uniform constellation.
1. A digital communication system, comprising:
a transmitter capable of transmitting signals via a communication channel, where the transmitter comprises:
a coder capable of receiving bits and outputting encoded bits using a Low Density Parity Check (LDPC) code;
a mapper, coupled to the coder, capable of mapping the encoded bits to symbols in a symbol constellation selected from a plurality of symbol constellations based upon communication channel condition, where each of the plurality of symbol constellations comprises a plurality of constellation points and each constellation point corresponds to a plurality of bits that are all encoded by the coder using the LDPC code; and
a modulator, coupled to the mapper, capable of generating a signal for transmission via the communication channel based upon symbols selected by the mapper;
wherein the plurality of symbol constellations use phase shift keying and comprise a first type and a second type of symbol constellation;
wherein the first type of symbol constellation is a non-uniformly spaced symbol constellation and comprises a ring of unequally spaced constellation points; and
wherein the second type of symbol constellation comprises a ring of equally spaced constellation points.
2. The communication system of claim 1 , wherein:
each of the plurality of symbol constellations is associated with a different signal-to-noise ratio (SNR); and
the plurality of symbol constellations includes multiple different sixteen-point symbol constellations of the first type that are each associated with SNRs that are less than 14.8 dB.
3. The communication system of claim 2 , wherein the plurality of symbol constellations includes a sixteen-point symbol constellation of the second type.
4. The communication system of claim 1 , wherein:
each of the first type of symbol constellation is associated with a different signal-to-noise ratio (SNR);
the plurality of symbol constellations includes an eight-point symbol constellation of the first type that is associated with an SNR that is less than 8.4 dB;
the plurality of symbol constellations includes a thirty-two-point symbol constellation of the first type that is associated with an SNR that is less than 20.4 dB.
5. The communication system of claim 1 , wherein:
each of the first type of symbol constellation is associated with a different signal-to-noise ratio (SNR); and
at least one of the first type of symbol constellation is characterized by the assignment of labels and the spacing of the constellation points such that the at least one of the first type of symbol constellation is capable of providing greater parallel decoding capacity when operated at its respective associated SNR than any of the other plurality of symbol constellations when operated at the same SNR.
6. The communication system of claim 1 , wherein at least one of the first type of symbol constellation is characterized by the assignment of labels and the spacing of the constellation points so as to maximize parallel decoding capacity at a specific SNR subject to at least one constraint.
7. The communication system of claim 1 , wherein each of the first type of symbol constellation is a multi-dimensional symbol constellation.
8. The communication system of claim 1 , wherein:
the transmitter is capable of receiving a symbol constellation change request; and
the mapper is capable of selecting the selected symbol constellation from the plurality of symbol constellations based upon communication channel condition by selecting the selected symbol constellation from the plurality of symbol constellations in response to a received symbol constellation change request sent by a remote receiver in response to a change in communication channel condition.
9. The communication system of claim 1 , wherein the transmitter is capable of substituting the plurality of symbol constellations by an upgrade to at least one of the transmitter software and firmware.
10. The communication system of claim 1 , further comprising:
a receiver that is capable of receiving signals via the communication channel at a channel signal-to-noise ratio (SNR) at the receiver, wherein the receiver comprises:
a demodulator capable of demodulating a received signal into a demodulated signal;
a demapper, coupled to the demodulator, capable of determining likelihoods using the demodulated signal and the symbol constellation selected from the plurality of symbol constellations; and
a decoder, coupled to the demapper, capable of using the likelihoods determined by the demapper to provide a sequence of received bits based upon the LDPC code.
11. A digital communication system, comprising:
a transmitter that transmits signals via a communication channel, where the transmitter comprises:
a coder that receives bits and outputs encoded bits using a Low Density Parity Check (LDPC) code;
a mapper that maps the encoded bits to symbols in a symbol constellation selected from a plurality of symbol constellations based upon communication channel condition, where each of the plurality of the symbol constellations comprises a plurality of constellation points and each constellation point corresponds to a plurality of bits that are all encoded by the coder using the LDPC code; and
a modulator that generates a signal for transmission via the communication channel based upon symbols selected by the mapper;
wherein the mapper is interposed between the modulator and the coder and the mapper receives information from the coder and provides information to the modulator;
wherein the plurality of symbol constellations use phase shift keying and comprise a first type and a second type of symbol constellation;
wherein the first type of symbol constellation is a non-uniformly spaced symbol constellation and comprises a ring of unequally spaced constellation points; and
wherein the second type of symbol constellation comprises a ring of equally spaced constellation points.
12. The communication system of claim 11 , wherein:
each of the plurality of symbol constellations is associated with a different signal-to-noise ratio (SNR); and
the plurality of symbol constellations includes multiple different sixteen-point symbol constellations of the first type that are each associated with SNRs that are less than 14.8 dB.
13. The communication system of claim 12 , wherein the plurality of symbol constellations includes a sixteen-point symbol constellation of the second type.
14. The communication system of claim 11 , wherein:
each of the first type of symbol constellation is associated with a different signal-to-noise ratio (SNR);
the plurality of symbol constellations includes an eight-point symbol constellation of the first type that is associated with an SNR that is less than 8.4 dB;
the plurality of symbol constellations includes a thirty-two-point symbol constellation of the first type that is associated with an SNR that is less than 20.4 dB.
15. The communication system of claim 11 , wherein:
each of the first type of symbol constellation is associated with a different signal-to-noise ratio (SNR); and
at least one of the first type of symbol constellation is characterized by the assignment of labels and the spacing of the constellation points such that the at least one of the first type of symbol constellation provides greater parallel decoding capacity when operated at its respective associated SNR than any of the other plurality of symbol constellations when operated at the same SNR.
16. The communication system of claim 11 , wherein at least one of the first type of symbol constellation is characterized by the assignment of labels and the spacing of the constellation points so as to maximize parallel decoding capacity at a specific SNR subject to at least one constraint.
17. The communication system of claim 11 , wherein each of the first type of symbol constellation is a multi-dimensional symbol constellation.
18. The communication system of claim 11 , wherein:
the transmitter receives a symbol constellation change request; and
the mapper selects the selected symbol constellation from the plurality of symbol constellations based upon communication channel condition by selecting the selected symbol constellation from the plurality of symbol constellations in response to a received symbol constellation change request sent by a remote receiver in response to a change in communication channel condition.
19. The communication system of claim 11 , wherein the transmitter can substitute the plurality of symbol constellations by an upgrade to at least one of the transmitter software and firmware.
20. The communication system of claim 11 , further comprising:
a receiver that receives signals via the communication channel at a channel signal-to-noise ratio (SNR) at the receiver, wherein the receiver comprises:
a demodulator that demodulates a received signal into a demodulated signal;
a demapper that determines likelihoods using the demodulated signal and the symbol constellation selected from the plurality of symbol constellations; and
a decoder that uses the likelihoods determined by the demapper to provide a sequence of received bits based upon the LDPC code;
wherein the demapper is interposed between the demodulator and the decoder and the demapper receives information from the demodulator and provides information to the decoder.
21. A digital communication system, comprising:
a transmitter that transmits signals via a communication channel, where the transmitter uses a symbol constellation selected from a plurality of symbol constellations based upon communication channel condition to transform encoded bits into the transmitted signals, where each of the plurality of symbol constellations comprises a plurality of constellation points and each constellation point corresponds to a plurality of bits that are all encoded by a coder using a Low Density Parity Check (LDPC) code;
wherein the plurality of symbol constellations use phase shift keying and comprise a first type and a second type of symbol constellation;
wherein the first type of symbol constellation is a non-uniformly spaced symbol constellation and comprises a ring of unequally spaced constellation points; and
wherein the second type of symbol constellation comprises a ring of equally spaced constellation points.
22. The communication system of claim 21 , wherein:
each of the plurality of symbol constellations is associated with a different signal-to-noise ratio (SNR); and
the plurality of symbol constellations includes multiple different sixteen-point symbol constellations of the first type that are each associated with SNRs that are less than 14.8 dB.
23. The communication system of claim 22 , wherein the plurality of symbol constellations includes a sixteen-point symbol constellation of the second type.
24. The communication system of claim 21 , wherein:
each of the first type of symbol constellation is associated with a different signal-to-noise ratio (SNR);
the plurality of symbol constellations includes an eight-point symbol constellation of the first type that is associated with an SNR that is less than 8.4 dB;
the plurality of symbol constellations includes a thirty-two-point symbol constellation of the first type that is associated with an SNR that is less than 20.4 dB.
25. The communication system of claim 21 , wherein:
each of the first type of symbol constellation is associated with a different signal-to-noise ratio (SNR); and
at least one of the first type of symbol constellation is characterized by the assignment of labels and the spacing of the constellation points such that the at least one of the first type of symbol constellation provides greater parallel decoding capacity when operated at its respective associated SNR than any of the other plurality of symbol constellations when operated at the same SNR.
26. The communication system of claim 21 , wherein at least one of the first type of symbol constellation is characterized by the assignment of labels and the spacing of the constellation points so as to maximize parallel decoding capacity at a specific SNR subject to at least one constraint.
27. The communication system of claim 21 , wherein each of the first type of symbol constellation is a multi-dimensional symbol constellation.
28. The communication system of claim 21 , wherein:
the transmitter receives a symbol constellation change request; and
the transmitter selects a new symbol constellation from the plurality of symbol constellations based upon communication channel condition by selecting the selected symbol constellation from the plurality of symbol constellations in response to a received symbol constellation change request sent by a remote receiver in response to a change in communication channel condition.
29. The communication system of claim 21 , wherein the transmitter can substitute the plurality of symbol constellations by an upgrade to at least one of the transmitter software and firmware.
30. The communication system of claim 21 , further comprising a receiver that receives signals via the communication channel at a channel signal-to-noise ratio (SNR) at the receiver, wherein the receiver uses the symbol constellation selected from the plurality of symbol constellations to transform the received signals into received bits.