Method and apparatus for par reduction
Embodiments of the present disclosure provide an apparatus of reducing a peak-to-average ratio of a multi-carrier signal to be transmitted in a wireless communication system. The apparatus comprises a multi-carrier processing circuitry, a storage and a peak cancellation circuitry. The multi-carrier processing circuitry is configured to process a plurality of signals on respective carriers and to combine the processed plurality of signals into a multi-carrier signal to be transmitted. The multi-carrier processing circuitry is further configured to process an injected impulse to obtain an impulse response of the multi-carrier processing circuitry. The storage is configured to store the impulse response as a clipping pulse. The peak cancellation circuitry is configured to apply the clipping pulse to the multi-carrier signal to cancel a peak of the multi-carrier signal whose amplitude is over a predetermined threshold.
1. An apparatus for reducing a peak-to-average ratio of a multi-carrier signal to be transmitted in a wireless communication system, the apparatus comprising:
multi-carrier processing circuitry configured to process a plurality of signals on respective carriers and to combine the processed plurality of signals into the multi-carrier signal to be transmitted, wherein the multi-carrier processing circuitry is further configured to process an injected impulse to obtain an impulse response of the multi-carrier processing circuitry;
a storage configured to store the impulse response as a clipping pulse; and
a peak cancellation circuitry configured to apply the clipping pulse to the multi-carrier signal to cancel a peak of the multi-carrier signal whose amplitude is over a predetermined threshold.
2. The apparatus of claim 1 , wherein
the multi-carrier processing circuitry is further configured to:
process the injected impulse within a first time period;
process the plurality of signals within a second time period; and
combine the processed plurality of signals within the second time period, and
the peak cancellation circuitry is further configured to apply the clipping pulse to the multi-carrier signal within the second time period.
3. The apparatus of claim 1 , wherein the multi-carrier processing circuitry comprises a plurality of carrier processing branches each processing a different one of the plurality of signals on the respective carriers, and
wherein the impulse is injected to each of the plurality of carrier processing branches.
4. The apparatus of claim 3 , wherein each of the plurality of carrier processing branches comprises:
a filtering circuit configured to filter the impulse with a preconfigured bandwidth;
a delay aligning circuit configured to delay aligning the impulse with a preconfigured delay alignment coefficient; and
a frequency translating circuit configured to frequency translate the impulse to a frequency of the corresponding carrier, and
wherein the multi-carrier processing circuitry comprises an adder configured to combine the impulses processed by the plurality of carrier processing branches to obtain the impulse response.
5. The apparatus of claim 4 , wherein each of the plurality of carrier processing branches further comprises:
a gain adjusting circuit configured to adjust an amplitude of the impulse; and
a rate converting circuit configured to convert a rate of the impulse with a preconfigured rate converting parameter.
6. The apparatus of claim 5 , wherein
the preconfigured bandwidth, the preconfigured delay alignment coefficient, and the preconfigured rate converting parameter are configured according to a signal processed by the corresponding carrier processing branch.
7. The apparatus of claim 5 , wherein
the amplitude of the impulse is adjusted according to power spectrum densities of the plurality of signals on the respective carriers.
8. The apparatus of claim 2 , wherein
the wireless communication system is a time division duplex system,
if the multi-carrier signal is transmitted in downlink from a base station to a terminal device, the first time period is an uplink period for transmission from the terminal device to the base station, and
if the multi-carrier signal is transmitted in uplink from the terminal device to the base station, the first time period is a downlink period for transmission from the base station to the terminal device.
9. The apparatus of claim 2 , wherein
the wireless communication system is a frequency division duplex system, and
the first time period is an idle symbol period.
10. A method of reducing a peak-to-average ratio of a multi-carrier signal to be transmitted in a wireless communication system, the method comprising:
generating a clipping pulse by injecting an impulse to a multi-carrier processing system for processing a plurality of signals on respective carriers to obtain an impulse response of the multi-carrier processing system;
storing the impulse response as the generated clipping pulse;
processing, by the multi-carrier processing system, the plurality of signals on the respective carriers;
combining, by the multi-carrier processing system, the processed plurality of signals into the multi-carrier signal to be transmitted; and
applying the generated clipping pulse to the multi-carrier signal to cancel a peak of the multi-carrier signal whose amplitude is over a predetermined threshold.
11. The method of claim 10 , wherein:
generating the clipping pulse is performed within a first time period; and
processing the plurality of signals, combining the processed plurality of signals, and applying the generated clipping pulse are performed within a second time period.
12. The method of claim 10 , wherein the multi-carrier processing system comprises a plurality of carrier processing branches, each processing a different one of the plurality of signals on the respective carriers, and
wherein injecting the impulse comprises injecting the impulse to each of the plurality of carrier processing branches.
13. The method of claim 12 , wherein generating the clipping pulse comprises:
processing the impulse at each of the plurality of carrier processing branches by at least:
filtering the impulse by a filter with a preconfigured bandwidth,
delay aligning the impulse with a preconfigured delay alignment coefficient, and
frequency translating the impulse to a frequency of the corresponding carrier; and
combining the impulses processed by the plurality of carrier processing branches.
14. The method of claim 13 , wherein processing the impulse at each of the plurality of carrier processing branches further comprises:
adjusting an amplitude of the impulse; and
converting a rate of the impulse with a preconfigured rate converting parameter.
15. The method of claim 14 , wherein
the preconfigured bandwidth, the preconfigured delay alignment coefficient, and the preconfigured rate converting parameter are configured according to a signal processed by the corresponding carrier processing branch.
16. The method of claim 14 , wherein
the amplitude of the impulse is adjusted according to power spectrum densities of the plurality of signals on the respective carriers.
17. The method of claim 11 , wherein;
the wireless communication system is a time division duplex system,
if the multi-carrier signal is transmitted in downlink from a base station to a terminal device, the first time period is an uplink period for transmission from the terminal device to the base station, and
if the multi-carrier signal is transmitted in uplink from the terminal device to the base station, the first time period is a downlink period for transmission from the base station to the terminal device.
18. The method of claim 11 , wherein:
the wireless communication system is a frequency division duplex system, and
the first time period is an idle symbol period.