High peak to average power ratio (PAPR) mitigation in high speed data networks using symbol mapping adjustment
View Patent ↗Embodiments provide techniques for high peak to average power ratio (PAPR) event mitigation in high speed data networks, such as cable networks, for example. Embodiments are applicable to multi-carrier and single-carrier modulation systems. Embodiments operate by predicting or detecting the occurrence of a peaking event at the transmitter, and then mitigating potential effects of the peaking event at the transmitter, including application of alternative constellation symbol mappings.
1. A method of mitigating a peaking event, comprising:
detecting or predicting, at a transmitter, a peaking event in a signal to be transmitted by the transmitter, wherein the signal is a multi-carrier modulated signal, generated by modulating a plurality of symbols with a respective plurality of sub-carriers;
enumerating the plurality of sub-carriers to assign a respective number to each of the plurality of sub-carriers;
determining an amplitude of the peaking event;
processing the signal, after said detecting or predicting, to reduce the peaking event in the signal to generate a peak mitigated signal, wherein said processing comprises modifying in the frequency domain one or more symbols of a plurality of symbols associated with the signal;
adjusting phases of one or more of the plurality of sub-carriers having respective numbers above a predetermined number, wherein the predetermined number is selected based on the amplitude of the peaking event; and
transmitting the peak mitigated signal by the transmitter.
2. The method of claim 1 , wherein said processing comprises one or more of:
applying a constellation rotation to the one or more symbols associated with the plurality of symbols;
applying a constellation translation to the one or more symbols associated with the plurality of symbols; and
adjusting phases of the one or more symbols associated with the plurality of symbols.
3. The method of claim 1 , wherein said detecting or predicting comprises:
computing an average power over a selected number of sub-carriers of the plurality of sub-carriers;
comparing the average power to a predetermined threshold; and
detecting the peaking event based on the comparison of the average power and the predetermined threshold.
4. The method of claim 3 , wherein the selected number of sub-carriers is any number of the plurality of sub-carriers.
5. The method of claim 3 , wherein the predetermined threshold is determined a priori based on average power measurements associated with peaking events.
6. The method of claim 2 , wherein said adjusting comprises adjusting phases of a first set and a second set of symbols of the plurality of symbols, wherein said adjusting further comprises:
adjusting the phases of the first set of symbols by a first phase offset; and
adjusting the phases of the second set of symbols by a second phase offset.
7. The method of claim 1 , wherein said plurality of symbols are generated from a respective plurality of source symbols, wherein said processing further comprises:
adjusting one or more bit values in one or more of said source symbols.
8. The method of claim 1 , wherein said plurality of symbols are generated by symbol mapping a respective plurality of source symbols according to a constellation.
9. The method of claim 8 , wherein the constellation satisfies one or more of the following: rotationally-invariant; includes set-partitioned coded modulation; includes set-partitioned coded modulation, with Gray-mapped or count-mapped uncoded bits; includes set-partitioned coded modulation, with uncoded bits count-mapped in the right-hand quadrant of the constellation; uses differentially encoded Most Significant Bits (MSBs); and is a Gray-mapped or count-mapped constellation.
10. The method of claim 1 , wherein the signal includes an orthogonal frequency division multiplexing (OFDM) frame.
11. The method of claim 1 , further comprising:
communicating information regarding the peaking event to a receiver.
12. The method of claim 11 , wherein the peaking event is detected or predicted in a current frame of the signal, and wherein said communicating comprises communicating the information regarding the peaking event in the current frame or a subsequent frame of the signal.
13. A transmitter, comprising:
a peaking event detector or predictor module configured to predict or detect a peaking event in a signal to be transmitted by the transmitter, wherein the signal is a multi-carrier modulated signal, generated by modulating a plurality of symbols with a respective plurality of sub-carriers, and wherein the peaking event detector or predictor module is configured to enumerate the plurality of sub-carriers to assign a respective number to each of the plurality of sub-carriers and to determine an amplitude of the peaking event; and
a symbol mapper configured to process the signal, after the prediction or detection of the peaking event, to reduce the peaking event in the signal to generate a peak mitigated signal, wherein the symbol mapper is configured to modify in the frequency domain one or more of a plurality of symbols associated with the signal to generate the peak mitigated signal, wherein the symbol mapper is configured to adjust phases of one or more of the plurality of sub-carriers having respective numbers above a predetermined number, wherein the predetermined number is selected based on the amplitude of the peaking event.
14. The transmitter of claim 13 , wherein the symbol mapper is configured to perform one or more of the following to reduce the peaking event:
apply a constellation rotation to the one or more symbols associated with the plurality of symbols;
apply a constellation translation to the one or more symbols associated with the plurality of symbols; and
adjust phases of the one or more symbols associated with the plurality of symbols.