Modulation and demodulation for enhanced noise margins in 5G and 6G
View Patent ↗Message faults are expected to become a major problem for next-generation 5G/6G networks, due to signal fading, high backgrounds, and high density of users. Disclosed are methods to modulate and demodulate messages to optimize noise margins, greatly enhancing reliability at negligible cost, according to some embodiments. A transmitter can modulate a message using amplitude-phase modulation, yet a receiver can conveniently receive and process the signals according to separate in-phase (I) and quad-phase (Q) branches, that is, according to QAM. The receiver can then convert the I and Q values to the original waveform amplitude and phase mathematically, and then demodulate those values using predetermined amplitude and phase levels as provided by a proximate demodulation reference. By converting the as-received QAM values to the as-transmitted amplitude-phase values, the receiver can thereby avoid many noise vulnerabilities inherent in QAM-modulated messages, and thereby obtain the full noise margins provided by amplitude-phase modulation.
1. A method for a wireless receiver to demodulate a message, the method comprising:
a) receiving a demodulation reference modulated, by a transmitter, according to an amplitude-phase modulation scheme comprising Namp amplitude levels and Nphase phase levels;
b) determining, according to the demodulation reference, the Namp amplitude levels and the Nphase phase levels of the amplitude-phase modulation scheme;
c) receiving a message modulated, by the transmitter, according to the amplitude-phase modulation scheme, the message comprising message elements, each message element comprising a resource element of a resource grid, wherein each message element, as received by the wireless receiver, contains a received wave comprising a received wave amplitude and a received wave phase;
d) for each message element, separating the received wave into an I-branch and an orthogonal Q-branch, the I-branch comprising an I-branch amplitude and the Q-branch comprising a Q-branch amplitude, the I-branch and Q-branch comprising a QAM (quadrature amplitude modulation) modulation scheme;
e) for each message element, calculating the received wave amplitude according to a square root of a sum of the I-branch amplitude squared plus the Q-branch amplitude squared, and calculating the received wave phase according to an arctangent of a ratio of the Q-branch amplitude divided by the I-branch amplitude; and
f) demodulating the message by selecting a particular amplitude level, of the Namp amplitude levels, closest to the received wave amplitude, and selecting a particular phase level, of the Nphase phase levels, closest to the received wave phase.
2. The method of claim 1 , wherein the message is received according to 5G or 6G technology.
3. The method of claim 1 , wherein the amplitude-phase modulation scheme comprises amplitude modulation multiplexed with phase modulation.
4. The method of claim 1 , wherein the Namp amplitude levels are equally spaced apart in amplitude, and the Nphase phase modulation levels are equally spaced apart in phase.
5. The method of claim 1 , wherein the Nphase phase modulation levels are equally spaced apart in phase, and wherein the Namp amplitude levels are spaced apart unequally according to a formula.
6. The method of claim 1 , wherein Namp is different from Nphase.
7. The method of claim 1 , wherein the QAM modulation scheme comprises Nstate modulation states, wherein Nstate equals Namp times Nphase.
8. The method of claim 1 , wherein the separating the received wave into an I-branch and an orthogonal Q-branch comprises:
a) measuring the I-branch amplitude according to an in-phase component of the received wave; and
b) measuring the Q-branch amplitude according to a quadrature-phase component of the received wave.
9. The method of claim 1 , wherein:
a) the demodulation reference comprises a first resource element and a second resource element;
b) the first resource element is modulated, by the transmitter, according to a maximum amplitude level of the Namp amplitude levels, multiplexed with a maximum phase level of the Nphase phase levels; and
c) the second resource element comprises zero transmission.
10. The method of claim 9 , further comprising:
a) measuring a received phase angle according to a received demodulation signal in the first resource element of the demodulation reference; and
b) determining a phase rotation angle comprising a difference between the received phase angle and the maximum phase level of the Nphase phase levels.
11. The method of claim 10 , further comprising:
a) before demodulating each message element, subtracting the phase rotation angle from from the received wave phase of the message element.
12. The method of claim 9 , further comprising:
a) receiving a background signal in the second resource element of the demodulation reference; and
b) determining a background amplitude of the background signal and a background phase of the background signal.
13. The method of claim 12 , further comprising:
a) for each message element, subtracting the background amplitude from the received wave amplitude when the background phase is aligned with the received wave phase, and adding the background amplitude to the received wave amplitude when the background phase is opposite to the received wave phase.
14. The method of claim 12 , further comprising, before calculating the received wave amplitude and phase:
a) for each message element, calculating an I-branch amplitude correction according to the background amplitude and the background phase, and calculating a Q-branch amplitude correction according to the background amplitude and the background phase; and
b) subtracting the I-branch amplitude correction from the I-branch amplitude, and subtracting the Q-branch amplitude correction from the Q-branch amplitude.
15. A method for a transmitter of a base station of a wireless network to mitigate message faults, the method comprising:
a) using a modulation scheme comprising amplitude modulation multiplexed with phase modulation, the amplitude modulation according to integer Namp amplitude levels and the phase modulation according to integer Nphase phase modulation levels;
b) determining a rate of amplitude faults and a rate of phase faults, wherein an amplitude fault comprises a message modulated, by the transmitter, according to a particular amplitude level of the Namp amplitude levels, and then demodulated, by a receiver, according to a different amplitude level of the Namp amplitude levels, and wherein a phase fault comprises a message modulated, by the transmitter, according to a particular phase level of the Nphase phase levels, and then demodulated, by a receiver, according to a different phase level of the Nphase phase levels;
c) selecting a second modulation scheme comprising integer Mamp amplitude levels and integer Mphase phase levels, wherein Mamp and Mphase are selected according to the rate of amplitude faults and the rate of phase faults; and
d) wherein either Mamp is different from Namp, or Mphase is different from Nphase, or both.
16. The method of claim 15 , wherein the selecting a second modulation scheme comprises:
a) when the rate of amplitude faults exceeds the rate of phase faults, selecting Mamp less than Namp; and
b) when the rate of phase faults exceeds the rate of amplitude faults, selecting Mphase less than Nphase.
17. The method of claim 15 , wherein Namp is different from Nphase, or Mamp is different from Mphase, or both.
18. A method for a wireless transmitter to optimize communication throughput, the method comprising:
a) using a first modulation scheme comprising amplitude modulation multiplexed with phase modulation, the amplitude modulation according to integer Namp amplitude levels and the phase modulation according to a first plurality of phase levels, wherein the phase levels of the first plurality are uniformly spaced apart by a first phase separation;
b) determining a rate of phase faults, wherein a phase fault comprises a message transmitted, by the transmitter, according to a particular phase level of the first plurality, and demodulated, by a receiver, according to a different phase level of the first plurality than the particular phase level; and
c) when the rate of phase faults exceeds a predetermined threshold, changing to a second modulation scheme comprising a second plurality of phase levels uniformly spaced apart by a second phase separation, wherein the second phase separation is larger than the first phase separation.
19. The method of claim 18 , further comprising:
a) when the rate of phase faults is less than a second predetermined threshold, changing to a third modulation scheme comprising a third plurality of phase levels uniformly spaced apart by a third phase separation, wherein the third phase separation is smaller than the first phase separation.
20. The method of claim 18 , further comprising:
a) after changing to the second modulation scheme, determining a subsequent rate of phase faults;
b) when the subsequent rate of phase faults exceeds the first predetermined threshold, changing to a modulation scheme comprising amplitude modulation according to integer Mamp amplitude levels, and phase modulation according to a single phase modulation level.