Transmitters Incorporating Unequally Spaced Constellations that Provide Reduced SNR Requirements as Compared to Equally Spaced Constellations

• US 20200137595A1
• Filed: 12/27/2019
• Published: 04/30/2020
• Est. Priority Date: 06/05/2007
• Status: Active Grant

• Current Assignee: Constellation Designs, LLC (SoftBank Group Corp.)
• Original Assignee: Constellation Designs, LLC (SoftBank Group Corp.)
• Inventors: Barsoum, Maged F., Jones, Christopher R.
• Granted Patent: US 10,708,794 B2
• Time in Patent Office: Days
• CPC Class Codes: H03M 13/255 with Low Density Parity Check [LDPC] codes
• CPC Class Codes: H03M 13/6325 Error control coding in combination with demodulation
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 27/3405 Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power
• CPC Class Codes: H04L 27/3483 using a modulation of the constellation points
• CPC Class Codes: H04L 27/3809 Amplitude regulation arrangements
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

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.

Claims

1. A communication system, comprising:

a transmitter capable of transmitting signals via a communication channel having a channel signal-to-noise ratio (SNR), wherein 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 that includes a group of symbol constellations that each have the same number of constellation points and comprise a ring of constellation points that are unequally spaced along the ring; and

a modulator, coupled to the mapper, capable of generating a signal for transmission via the communication channel based upon the mapped symbols;

wherein the labels and spacing of the constellation points in each of the symbol constellations in the group of symbol constellations are arranged such that the symbol constellation is capable of providing a given capacity at a reduced signal-to-noise ratio as compared to a similar symbol constellation that differs only in that the constellation points in the ring are equally spaced around the ring.

2. The communication system of claim 1, wherein:

each of the plurality of symbol constellations are associated with a different SNR; and

the group of symbol constellations comprises symbol constellations with sixteen constellation points that are associated with SNRs that are less than 14.8 dB.

3. The communication system of claim 2, wherein:

the plurality of symbol constellations further comprises a symbol constellation that includes a sixteen point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring; and

the sixteen point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the sixteen point symbol constellations in the group of symbol constellations.

4. The communication system of claim 3, wherein:

the plurality of symbol constellations further comprises a second group of symbol constellations that each contain eight constellation points associated with SNRs less than 8.4 dB;

a third group of symbol constellations that each contain thirty-two constellation points associated with SNRs less than 20.4 dB;

each of the symbol constellations in the second and third groups of symbol constellations comprises a ring of constellation points that are unequally spaced along the ring where the labels and spacing of the constellation points are arranged such that each of the symbol constellations in the second and third groups of symbol constellations are capable of providing a given capacity at a reduced signal-to-noise ratio as compared to a similar symbol constellation that differs only in that the constellation points in the ring are equally spaced around the ring;

the plurality of symbol constellations further comprises;

an eight point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring; and

a thirty-two point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring;

the eight point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the eight point symbol constellations in the second group of symbol constellations; and

the thirty-two point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the thirty-two point symbol constellations in the third group of symbol constellations.

5. The communication system of claim 1, wherein:

each of the plurality of symbol constellations are associated with a different SNR; and

the labels and spacing of the constellation points in each constellation in the group of symbol constellations are arranged such that each of the symbol constellations in the group of symbol constellations are capable of providing greater parallel decoding capacity when operated at its 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 the symbol constellations within the group of symbol constellations are 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 the plurality of symbol constellations are multi-dimensional symbol constellations having multiple degrees of freedom.

8. The communication system of claim 1 wherein the transmitter is capable of receiving a request from a remote receiver to modulate the signals transmitted via the communication channel using a specific symbol constellation from the plurality of symbol constellations, where the specific symbol constellation is determined based on a quality measurement by the remote receiver.

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 communication system, comprising:

a transmitter that transmits signals via a communication channel having a channel signal-to-noise ratio (SNR), wherein 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 that includes a group of symbol constellations that each have the same number of constellation points and comprise a ring of constellation points that are unequally spaced along the ring; and

a modulator that generates a signal for transmission via the communication channel based upon the mapped symbols;

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 labels and spacing of the constellation points in each of the symbol constellations in the group of symbol constellations are arranged such that the symbol constellation provides a given capacity at a reduced signal-to-noise ratio as compared to a similar symbol constellation that differs only in that the constellation points in the ring are equally spaced around the ring.

12. The communication system of claim 11, wherein:

each of the plurality of symbol constellations are associated with a different SNR; and

the group of symbol constellations comprises symbol constellations with sixteen constellation points that are associated with SNRs that are less than 14.8 dB.

13. The communication system of claim 12, wherein:

the plurality of symbol constellations further comprises a symbol constellation that includes a sixteen point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring; and

the sixteen point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the sixteen point symbol constellations in the group of symbol constellations.

14. The communication system of claim 13, wherein:

the plurality of symbol constellations further comprises a second group of symbol constellations that each contain eight constellation points associated with SNRs less than 8.4 dB;

a third group of symbol constellations that each contain thirty-two constellation points associated with SNRs less than 20.4 dB;

each of the symbol constellations in the second and third groups of symbol constellations comprises a ring of constellation points that are unequally spaced along the ring where the labels and spacing of the constellation points are arranged such that each of the symbol constellations in the second and third groups of symbol constellations provide a given capacity at a reduced signal-to-noise ratio as compared to a similar symbol constellation that differs only in that the constellation points in the ring are equally spaced around the ring;

the plurality of symbol constellations further comprises;

an eight point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring; and

a thirty-two point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring;

the eight point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the eight point symbol constellations in the second group of symbol constellations; and

the thirty-two point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the thirty-two point symbol constellations in the third group of symbol constellations.

15. The communication system of claim 11, wherein:

each of the plurality of symbol constellations are associated with a different SNR; and

the labels and spacing of the constellation points in each constellation in the group of symbol constellations are arranged such that each of the symbol constellations in the group of symbol constellations provide greater parallel decoding capacity when operated at its 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 the symbol constellations within the group of symbol constellations are 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 the plurality of symbol constellations are multi-dimensional symbol constellations having multiple degrees of freedom.

18. The communication system of claim 11 wherein the transmitter receives a request from a remote receiver to modulate the signals transmitted via the communication channel using a specific symbol constellation from the plurality of symbol constellations, where the specific symbol constellation is determined based on a quality measurement by the remote receiver.

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 communication system, comprising:

a transmitter that transmits signals via a communication channel having a channel signal-to-noise ratio (SNR), wherein the transmitter uses a symbol constellation to transform encoded bits into the transmitted signals, where the symbol constellation is selected from a plurality of symbol constellations that includes a group of symbol constellations that each have the same number of constellation points and comprise a ring of constellation points that are unequally spaced along the ring;

wherein the labels and spacing of the constellation points in each of the symbol constellations in the group of symbol constellations are arranged such that the symbol constellation provides a given capacity at a reduced signal-to-noise ratio as compared to a similar symbol constellation that differs only in that the constellation points in the ring are equally spaced around the ring.

22. The communication system of claim 21, wherein:

each of the plurality of symbol constellations are associated with a different SNR; and

the group of symbol constellations comprises symbol constellations with sixteen constellation points that are associated with SNRs that are less than 14.8 dB.

23. The communication system of claim 22, wherein:

the plurality of symbol constellations further comprises a symbol constellation that includes a sixteen point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring; and

the sixteen point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the sixteen point symbol constellations in the group of symbol constellations.

24. The communication system of claim 23, wherein:

the plurality of symbol constellations further comprises a second group of symbol constellations that each contain eight constellation points associated with SNRs less than 8.4 dB;

a third group of symbol constellations that each contain thirty-two constellation points associated with SNRs less than 20.4 dB;

each of the symbol constellations in the second and third groups of symbol constellations comprises a ring of constellation points that are unequally spaced along the ring where the labels and spacing of the constellation points are arranged such that each of the symbol constellations in the second and third groups of symbol constellations provide a given capacity at a reduced signal-to-noise ratio as compared to a similar symbol constellation that differs only in that the constellation points in the ring are equally spaced around the ring;

the plurality of symbol constellations further comprises;

an eight point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring; and

a thirty-two point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring;

the eight point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the eight point symbol constellations in the second group of symbol constellations; and

the thirty-two point symbol constellation that comprises a ring of constellation points that are evenly spaced along the ring is associated with an SNR that is higher than any of the SNRs associated with the thirty-two point symbol constellations in the third group of symbol constellations.

25. The communication system of claim 21, wherein:

each of the plurality of symbol constellations are associated with a different SNR; and

the labels and spacing of the constellation points in each constellation in the group of symbol constellations are arranged such that each of the symbol constellations in the group of symbol constellations provide greater parallel decoding capacity when operated at its 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 the symbol constellations within the group of symbol constellations are 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 the plurality of symbol constellations are multi-dimensional symbol constellations having multiple degrees of freedom.

28. The communication system of claim 21 wherein the transmitter receives a request from a remote receiver to modulate the signals transmitted via the communication channel using a specific symbol constellation from the plurality of symbol constellations, where the specific symbol constellation is determined based on a quality measurement by the remote receiver.

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.