Ultra-compact phase-tracking demodulation reference for 5G/6G

1. A method for a base station of a wireless network to communicate, the method comprising:

a) providing a resource grid comprising resource elements, each resource element comprising a symbol-time representing time and a subcarrier representing frequency; and

b) transmitting, on a predetermined subcarrier, in one or more symbol-times scheduled for downlink transmissions, a compact phase-tracking reference;

c) wherein the compact phase-tracking reference comprises a resource element comprising an I-branch signal and an orthogonal Q-branch signal;

d) wherein the I-branch signal is transmitted with a predetermined non-zero amplitude; and

e) wherein the Q-branch signal is transmitted with the predetermined non-zero amplitude.

2. The method of claim 1 , wherein the resource grid is configured according to 5G or 6G technology.

3. The method of claim 1 , wherein:

a) a modulation scheme comprises amplitude modulation according to a plurality of predetermined amplitude levels;

b) the plurality of predetermined amplitude levels comprises a maximum amplitude level; and

c) the predetermined non-zero amplitude equals the maximum amplitude level.

4. The method of claim 1 , further comprising:

a) transmitting a system information message indicating a schedule and a format;

b) wherein the schedule indicates one or more times and one or more frequencies at which the compact phase-tracking reference is to be transmitted; and

c) wherein the format indicates the predetermined non-zero amplitude.

5. The method of claim 4 , wherein the system information message comprises at least one of:

a) an SSB (synchronization signal block) message;

b) an SIBn (system information block number n) message;

c) an RAR (random access response) message;

d) a Msg4 (message-4) of a 4-stage initial access procedure; and

e) a MsgB (message-B) of a 2-stage initial access procedure.

6. The method of claim 1 , further comprising repeating the transmitting of the compact phase-tracking reference periodically according to a period, wherein the period is one frame or one subframe or one slot of the resource grid.

7. The method of claim 1 , further comprising transmitting the compact phase-tracking reference in every symbol-time that is scheduled for downlink transmissions, other than symbol-times allocated for downlink control messages.

8. The method of claim 1 , further comprising transmitting the compact phase-tracking reference in every symbol-time that is allocated for downlink control messages.

9. The method of claim 1 , further comprising transmitting the compact phase-tracking reference in every symbol-time that includes a downlink message.

10. A method for a user device of a wireless network to communicate, the method comprising:

a) receiving or determining a schedule and a format, wherein the schedule comprises a particular subcarrier and one or more downlink symbol-times, wherein the format specifies parameters of a compact phase-tracking reference, wherein the compact phase-tracking reference comprises a reference I-branch signal and an orthogonal reference Q-branch signal;

b) wherein the reference I-branch signal is transmitted with a predetermined non-zero amplitude and the reference Q-branch signal is transmitted with the predetermined non-zero amplitude;

c) receiving, at one of the downlink symbol-times, on the particular subcarrier, a received compact phase-tracking reference comprising a received I-branch amplitude and a received Q-branch amplitude; and

d) determining, according to the received Q-branch amplitude and the received I-branch amplitude, a phase rotation angle.

11. The method of claim 10 , further comprising:

a) calculating a received angle according to an arctangent of the received Q-branch amplitude divided by the received I-branch amplitude;

b) then calculating the phase rotation angle by subtracting 45 degrees from the received angle;

c) receiving, in the particular symbol-time, a message comprising message elements, each message element comprising a modulated resource element; and

d) correcting each message element according to the phase rotation angle.

12. The method of claim 11 , further comprising:

a) determining a reference amplitude comprising a square root of a sum of the received I-branch amplitude squared plus the received Q-branch amplitude squared; and

b) further correcting each message element according to the reference amplitude.

13. The method of claim 12 , further comprising:

a) after the correcting each message element and the further correcting each message element, demodulating the message element by comparing an amplitude of the message element to a plurality of predetermined branch amplitude levels.

14. The method of claim 12 , further comprising:

a) for each message element, calculating a corrected I-branch amplitude and a corrected Q-branch amplitude according to the phase rotation angle and the reference amplitude; and

b) demodulating the message by comparing the corrected I-branch amplitude to a plurality of predetermined branch amplitude levels, and comparing the corrected Q-branch amplitude to the plurality of predetermined branch amplitude levels.

15. The method of claim 10 , further comprising:

a) transmitting, to a base station of the wireless network, an uplink message concatenated with an uplink compact phase-tracking reference;

b) wherein the uplink compact phase-tracking reference comprises a single resource element comprising an uplink I-branch signal and an orthogonal uplink Q-branch signal; and

c) wherein the uplink I-branch signal is transmitted with a predetermined non-zero amplitude and the uplink Q-branch signal is transmitted with the predetermined non-zero amplitude.

16. A method for a user device of a wireless network to communicate with a base station, the method comprising:

a) receiving, from the base station, a first message, and determining that the first message is faulted;

b) responsive to the determining that the first message is faulted, transmitting, to the base station, a request message requesting for the base station and the user device to provide a single-branch phase-tracking reference proximate to each message transmitted to the user device or transmitted by the user device;

c) then receiving, from the base station, a downlink message comprising a downlink single-branch phase-tracking reference;

d) wherein the downlink single-branch phase-tracking reference comprises an I-branch signal and an orthogonal Q-branch signal, wherein the I-branch signal is amplitude modulated according to a maximum branch amplitude of a QAM (quadrature amplitude modulation) modulation scheme, and the Q-branch signal has zero amplitude, as transmitted by the base station;

e) determining, according to the downlink single-branch phase-tracking reference as-received, a received I-branch amplitude and a received Q-branch amplitude; and

f) determining, according to a ratio of the received I-branch amplitude and the received Q-branch amplitude, a phase rotation angle.

17. The method of claim 16 , further comprising:

a) transmitting, to the base station, an uplink message comprising an uplink single-branch phase-tracking reference comprising an uplink I-branch signal and an orthogonal uplink Q-branch signal, wherein the uplink I-branch signal is amplitude modulated according to the maximum branch amplitude of the QAM modulation scheme, and the Q-branch signal has zero amplitude as-transmitted.

18. The method of claim 17 , wherein:

a) the uplink message occupies a single OFDM (orthogonal frequency-division multiplexing) symbol; and

b) the uplink single-branch phase-tracking reference is concatenated with a beginning of the uplink message.

19. The method of claim 17 , wherein the uplink message comprises a request to suspend future transmissions of the uplink and downlink single-branch phase-tracking references.

20. The method of claim 19 , further comprising receiving an acknowledgement message from the base station, wherein the acknowledgement message includes no single-branch phase-tracking references.