Extremely compact phase-tracking 5G/6G reference signal
Precision synchronization is key to reliable communications at the high frequencies planned for 5G and 6G. A timing reference signal can provide a compact, resource-efficient, low-complexity phase noise mitigation while also providing an amplitude noise calibration. The timing reference signal is a QAM (quadrature amplitude modulation) signal with an I branch multiplexed with an orthogonal Q branch, in which one of the branches is modulated according to a maximum amplitude level of the modulation scheme, and the other branch has zero amplitude as-transmitted. When received, the amplitude and phase may be altered by noise. The receiver can measure the overall magnitude of the received I and Q signals to mitigate amplitude noise, and can also calculate a phase rotation angle according to a ratio of the I and Q branch signals as-received, and thereby correct for phase noise in the message.
1. A method for a base station of a wireless network to communicate with user devices of the wireless network, the method comprising:
a) transmitting or broadcasting a timing signal comprising an I branch multiplexed with an orthogonal Q branch;
b) wherein the timing signal comprises exactly one resource element;
c) wherein one branch, of the I and Q branches, is amplitude modulated according to a maximum amplitude level of a QAM (quadrature amplitude modulation) modulation scheme; and
d) wherein the other branch, of the I and Q branches, is transmitted with zero amplitude.
2. The method of claim 1 , wherein the resource element is transmitted according to 5G or 6G technology.
3. The method of claim 1 , further comprising:
a) periodically transmitting or broadcasting the timing signal according to a predetermined schedule or periodicity.
4. The method of claim 3 , wherein:
a) the predetermined schedule or periodicity comprises one transmission or broadcast of the timing signal per each symbol-time allocated to downlink messaging.
5. The method of claim 3 , wherein
a) the predetermined schedule or periodicity comprises one transmission or broadcast of the timing signal per each two symbol-times allocated to downlink messaging.
6. The method of claim 1 , further comprising:
a) receiving, from a particular user device, a request to include the timing signal concatenated with each downlink message addressed to the particular user device.
7. The method of claim 6 , further comprising:
a) transmitting, to the particular user device, a downlink message concatenated with the timing signal.
8. The method of claim 1 , further comprising:
a) determining a rate of phase faults, wherein each phase fault comprises a message or message element that is transmitted according to a first modulation state of a modulation scheme, and is demodulated according to a second state of the modulation scheme, wherein the first and second states of the modulation scheme differ by a phase.
9. The method of claim 8 , further comprising:
a) upon determining that the rate of phase faults exceeds a predetermined threshold, broadcasting a message indicating that the timing signal will be provided periodically in a particular subcarrier of a resource grid.
10. The method of claim 9 , further comprising:
a) then, upon determining that the rate of phase faults no longer exceeds the predetermined threshold, broadcasting a message indicating that the timing signal will no longer be provided periodically.
11. A mobile wireless user device configured to:
a) receive, on a sidelink channel, a sidelink message from a wireless entity;
b) wherein the sidelink message includes or is concatenated with a timing reference symbol;
c) wherein the timing reference symbol comprises a single resource element of a resource grid;
d) wherein the timing reference symbol is modulated according to a QAM (quadrature amplitude modulation) modulation scheme comprising an I branch signal multiplexed with an orthogonal Q branch signal;
e) wherein one of the signals, of the I branch signal and the Q branch signal, is modulated, by a transmitting entity, according to a maximum amplitude level of the QAM modulation scheme, and the other signal is modulated, by the transmitting entity, at zero amplitude.
12. The mobile wireless user device of claim 11 , further configured to:
a) separate the received timing signal into a received I branch signal and a received Q branch signal;
b) calculate a sum-signal amplitude comprising a square root of a sum of the of the received I branch signal squared plus the received Q branch signal squared.
13. The mobile wireless user device of claim 12 , further configured to:
a) calculate a sum-signal phase comprising an arctangent of a ratio of the received Q branch signal divided by the received I branch signal.
14. The mobile wireless user device of claim 13 , further configured to:
a) determine a phase rotation angle by subtracting a predetermined phase from the sum-signal phase, wherein the predetermined phase is related to the I branch signal and the Q branch signal as transmitted by the transmitting entity.
15. The mobile wireless user device of claim 11 , further configured to:
a) transmit a second message to the wireless entity, the second message including or concatenated with a second timing signal, the second timing signal comprising an I branch signal modulated at zero amplitude or a Q branch signal modulated at zero amplitude.
16. Non-transitory computer-readable media in a base station or a core network of a wireless network, the media containing instructions that when implemented in a computing environment cause a method to be performed, the method comprising:
a) broadcasting a system information message comprising a format for a timing reference signal, the timing reference signal comprising an I branch signal multiplexed with an orthogonal Q branch signal, the I branch signal modulated according to a predetermined non-zero amplitude and the Q branch signal modulated at zero amplitude.
17. The non-transitory computer-readable media of claim 16 , wherein the system information message is an SSB (synchronization signal block) message or an SIB1 (first system information block) message.
18. The non-transitory computer-readable media of claim 16 , wherein the format indicates an initial phase comprising an arctangent of a ratio of the Q branch amplitude divided by the I branch amplitude.
19. The non-transitory computer-readable media of claim 16 , wherein the predetermined non-zero amplitude is a maximum branch amplitude of a QAM (quadrature amplitude modulation) modulation scheme or √2 times the maximum branch amplitude of the QAM modulation scheme.
20. The non-transitory computer-readable media of claim 19 , the method further comprising transmitting a message comprising message elements, wherein:
a) each odd-numbered message element is modulated to encode message data in a message I branch signal and a message Q branch signal, and
b) each even-numbered message element is modulated to encode message data in the message I branch signal, and to encode zero amplitude in the message Q branch signal.