Methods, devices and systems for modifying a power profile of a frequency division multiplexed signals
A method can include receiving a plurality of digital data symbols; encoding each data symbol into frequency domain values, the frequency domain values for each data symbol transmitted over a different frequency range; combining samples of multiple frequency domain values into a sequence of initial output values in time; generating a sequence of modification values that form a modification pulse, the modification pulse having a non-linear slope that decreases as it approaches a modification pulse maximum and increases as it departs from the modification pulse maximum; decreasing the initial output values according to the modification values to generate modified output values; and transmitting a wireless signal compatible with at least one IEEE wireless standard according to the modified output values. Corresponding devices and systems are also disclosed.
1. A method, comprising:
receiving a plurality of digital data symbols;
encoding each data symbol into frequency domain values, the frequency domain values for each data symbol transmitted over a different frequency range;
combining samples of multiple frequency domain values into a sequence of initial output values in time;
generating a sequence of modification values that form a modification pulse that includes
selecting a pulse feature set from a plurality of stored pulse feature sets with selection values, and
generating the sequence of modification values according to the selected pulse feature set, the modification pulse having a non-linear slope that decreases as it approaches a modification pulse maximum and increases as it departs from the modification pulse maximum;
decreasing the initial output values according to the modification values to generate modified output values; and
transmitting a wireless signal compatible with at least one IEEE wireless standard according to the modified output values.
2. The method of claim 1 , wherein:
the modification pulse has the shape of a Gaussian pulse.
3. The method of claim 1 , further including:
in response to determining that the initial output values are outside of a predetermined peak average power ratio (PAPR) over a predetermined time period, decreasing the initial output values according to the modification values.
4. The method of claim 1 , further including wherein:
generating the sequence of modification values further includes
generating selection values in response to at least the data symbols.
5. The method of claim 4 , wherein:
selecting the pulse feature set includes applying the selection values to a look-up table.
6. The method of claim 1 , wherein:
decreasing the initial output values according to the modification values includes
subtracting the modified output values from the initial values to form the modified output values, and
by operation of a digital-to-analog converter, converting the modified output values to an analog output signal.
7. The method of claim 1 , wherein:
decreasing the initial output values according to the modification values includes
by operation of a digital-to-analog converter, converting the initial output values to an initial analog output signal,
applying the initial analog output signal to an input of a variable gain amplifier, and
modulating the gain of the variable gain amplifier according to the modification values.
8. A device, comprising:
a data encoder circuit configured to encode data values into multi-bit data symbols;
a frequency encoder circuit configured to receive data symbols in parallel and encode each data symbol into frequency domain values, the frequency domain values for each data symbol being transmitted over a different frequency range;
an evaluation circuit configured to generate modification pulse values in response to the data symbols that includes
a modification pulse store configured to store a plurality of pulse feature sets, and
a modification pulse generation circuit that varies the generated modification pulse values in response to a selected pulse feature set;
a transmit power adjust circuit configured to
combine samples of multiple different frequency domain values into a sequence of initial output values in time, and
decrease the initial output values according to the modification pulse values to generate modified output values; and
wireless circuits configured to transmit a wireless signal compatible with at least one IEEE 802.11 wireless standard according to the modified output values; wherein
the modification pulse has a non-linear slope that decreases as it approaches a modification pulse maximum and increases as it departs from the modification pulse maximum.
9. The device of claim 8 , wherein:
the frequency encoder circuit comprises an inverse fast-Fourier transform circuit.
10. The device of claim 8 , wherein:
the evaluation circuit is configured to determine a peak-average-power-ratio (PAPR) for at least a portion of the initial output values; and
the transmit power adjust circuit is configured to decrease the initial output values in response to the PAPR being outside of a predetermined limit.
11. The device of claim 8 , wherein:
the evaluation circuit includes
arithmetic logic circuits configured to subtract the modification pulse values from the initial output values, and
a digital-to-analog converter configured to convert the modified output values into an analog signal.
12. The device of claim 8 , wherein:
the evaluation circuit includes
a digital-to-analog converter configured to convert the initial output values into an initial analog signal, and
an amplifier having a gain modulated by the modification pulse values.
13. The device of claim 8 , wherein:
the modification pulse has the shape of a Gaussian pulse.
14. A system, comprising:
a frequency multiplexing section that includes
a frequency modulating circuit configured to frequency modulate each of a plurality of data symbols over different frequency ranges to generate a plurality of modulated signals;
a radio circuit configured to transmit the modulated signals in parallel as an output signal that is compatible with at least one IEEE 802.11 wireless standard;
a power modification circuit configured to reduce a transmit power of the output signal according to a modification pulse that includes
a modification pulse store configured to store a plurality of pulse feature sets, and
a modification pulse generation circuit that varies the generated modification pulse values in response to a selected pulse feature set; and
an antenna system configured to at least transmit the output signal; wherein
the modification pulse has a non-linear slope that decreases as it approaches a modification pulse maximum and increases as it departs from the modification pulse maximum.
15. The system of claim 14 , wherein:
the power modification circuit is configured to
determine a peak-average-power-ratio (PAPR) for at least a portion of the modulated signals, and
reduce the transmit power in response to the PAPR being outside of a predetermined limit.
16. The system of claim 14 , wherein:
the different frequency ranges overlap one another and correspond to orthogonal carrier frequencies.
17. The system of claim 14 , wherein:
the modification pulse comprises a Gaussian pulse.