Systems and methods for the reduction of peak to average signal levels of multi-bearer single-carrier and multi-carrier waveforms
View Patent ↗The present invention is related to methods and apparatus that can advantageously reduce a peak to average signal level exhibited by single or by multicarrier multibearer waveforms. Embodiments of the invention further advantageously can manipulate the statistics of the waveform without expanding the spectral bandwidth of the allocated channels. Embodiments of the invention can be applied to either multiple carrier or single carrier systems to constrain an output signal within predetermined peak to average bounds. Advantageously, the techniques can be used to enhance the utilization of existing multicarrier RF transmitters, including those found in third generation cellular base stations. However, the peak to average power level managing techniques disclosed herein can apply to any band-limited communication system and any type of modulation. The techniques can apply to multiple signals and can apply to a wide variety of modulation schemes or combinations therof.
1. An adaptive control circuit that provides parameter updates to a digital waveshaping circuit configured to de-crest signal peaks, the adaptive control circuit coupled to at least one input symbol stream and to an output sample stream, where the input symbol stream is also provided as an input to the digital waveshaping circuit and the output sample stream is generated by the digital waveshaping circuit, the adaptive control circuit comprising:
a reference input configured to receive reference information, where the parameter updates are controlled at least in part by data received at the reference input;
an input monitoring circuit configured to monitor the at least one input symbol stream provided to the digital waveshaping circuit;
a receiver circuit configured to monitor the output sample stream from the digital waveshaping circuit, wherein the receiver circuit is configured to monitor the output sample stream before the output sample stream is amplified by a power amplifier; and
a parameter update circuit configured to calculate and to provide updated parameters to the digital waveshaping circuit based on the reference input, a monitored portion of the at least one input symbol stream, and the output sample stream, wherein the updated parameters comprise at least a parameter for adjustment of a pulse generator of the digital waveshaping circuit.
2. The adaptive control circuit as defined in claim 1 , wherein the parameter update circuit is configured to calculate the updated parameters in non real time.
3. The adaptive control circuit as defined in claim 1 , wherein the reference input is configured to accept information that controls the dynamic range compression of the digital waveshaping circuit.
4. The adaptive control circuit as defined in claim 1 , wherein the reference input is configured to accept information that controls a relative hardness or relative softness of limiting of the digital waveshaping circuit.
5. A method of adaptively controlling a digital waveshaping process, the method comprising:
receiving reference information as a control input;
monitoring at least one input symbol stream applied to the waveshaping process;
monitoring an output of the waveshaping process, where the output includes a waveform that is pulse-shaped and upconverted from the at least one input symbol stream;
updating a first parameter based, at least in part, on the monitored symbol stream and the control input, where the first parameter is used to select an impulse that is applied to the input symbol stream to at least partially reduce the magnitude of a signal peak in the output of the waveshaping process; and
updating a second parameter used to select a band-limited pulse that is applied to the output of the waveshaping process.
6. The method as defined in claim 5 , wherein updating the first parameter is not performed in real time.
7. The method as defined in claim 5 , wherein updating the second parameter is not performed in real time.
8. An apparatus for adaptively controlling a digital waveshaping process, the apparatus comprising:
means for receiving reference information as a control input;
means for monitoring at least one input symbol stream applied to the waveshaping process;
means for monitoring an output of the waveshaping process, where the output includes a waveform that is pulse-shaped and upconverted from the at least one input symbol stream;
means for updating a first parameter based, at least in part, on the monitored symbol stream and the control input, where the first parameter is used to select an impulse that is applied to the input symbol stream to at least partially reduce the magnitude of a signal peak in the output of the waveshaping process; and
means for updating a second parameter used to select a band-limited pulse that is applied to the output of the waveshaping process.
9. The apparatus as defined in claim 8 , wherein the first parameter updating means does not update the first parameter in real time.
10. The apparatus as defined in claim 8 , wherein the second parameter updating means does not update the second parameter in real time.