Extracting sub-bands from signals in a frequency domain
Embodiments are disclosed for extracting sub-bands of interest from signals in a frequency domain for transmission via a distributed antenna system. In one aspect, a transformed downlink signal is generated by performing a frequency transform on a downlink signal. The transformed downlink signal represents the downlink signal in a frequency domain. At least one sub-band of the transformed downlink signal is identified as including data to be transmitted via the distributed antenna system. The sub-band is extracted from the transformed downlink signal for transmission via the distributed antenna system.
1. A method comprising:
sub-dividing a downlink signal into a sub-divided downlink signal having a plurality of downlink signal components in a time domain, wherein each of the plurality of downlink signal components corresponds to a respective sub-band;
determining that at least one component of the plurality of downlink signal components corresponds to at least one sub-band having data to be transmitted via a distributed antenna system;
generating, subsequent to determining that the at least one component from the sub-divided downlink signal corresponds to the at least one sub-band, a transformed downlink signal by performing a frequency transform on the downlink signal, wherein the transformed downlink signal represents the downlink signal in a frequency domain;
determining that the at least one sub-band of the transformed downlink signal includes the data to be transmitted; and
extracting the at least one sub-band from the transformed downlink signal for transmission via the distributed antenna system, wherein extracting the at least one sub-band from the transformed downlink signal comprises:
providing, by the unit, data for at least a portion of the transformed downlink signal in the frequency domain that corresponds to the at least one sub-band to at least one remote antenna unit of the distributed antenna system.
2. The method of claim 1 , wherein performing the frequency transform comprises executing at least one of a fast Fourier transform algorithm, a discrete Fourier transform algorithm, and a discrete cosine transform algorithm using the downlink signal as an input.
3. The method of claim 1 , wherein determining that the at least one sub-band of the transformed downlink signal includes the data to be transmitted comprises:
identifying, for each of a plurality of portions of the transformed downlink signal in the frequency domain, a respective signal level for the portion; and
determining that at least one of the plurality of portions that corresponds to the at least one sub-band has a signal level exceeding a threshold signal level.
4. The method of claim 1 , wherein determining that the at least one sub-band of the transformed downlink signal includes the data to be transmitted comprises:
receiving a control signal from a base station;
identifying, from the control signal, at least one channel used by the base station to transmit downlink signals; and
identifying the at least one sub-band from the at least one identified channel.
5. The method of claim 1 , wherein discarding the additional data for the at least one additional portion comprises:
configuring a combiner module of the unit to exclude the additional data from a combining operation used to route the data for the at least one portion to the at least one remote antenna unit.
6. The method of claim 1 , further comprising:
determining that at least one additional sub-band lacks data to be transmitted via the distributed antenna system;
modifying the transformed downlink signal to exclude the at least one additional sub-band; and
reducing a sampling rate of the transformed downlink signal based on the transformed downlink signal being modified to exclude the at least one additional sub-band.
7. The method of claim 1 , further comprising:
receiving, by the unit of the distributed antenna system, a plurality of transformed uplink signals from a plurality of remote antenna units of the distributed antenna system, wherein each of the plurality of transformed uplink signals is generated by performing an additional frequency transform on a respective uplink signal to represent the respective uplink signal in the frequency domain;
identifying, by the unit, a subset of sub-bands from the plurality of transformed uplink signals that include uplink data to be transmitted via the distributed antenna system; and
combining, by the unit, the subset of sub-bands for transmission to a base station, wherein a combining operation performed by the unit excludes sub-bands other than the subset of sub-bands that include the uplink data.
8. The method of claim 1 , wherein the at least a portion of the transformed downlink signal includes at least one bin.
9. A unit comprising:
a first interface section configured to receive a downlink signal from a base station;
a signal processing section configured to sub-divide the downlink signal into a sub-divided downlink signal having a plurality of downlink signal components in a time domain, wherein each of the plurality of downlink signal components corresponds to a respective sub-band;
a processor communicatively coupled to the first interface section and configured to:
determine that at least one component of the plurality of downlink signal components corresponds to at least one sub-band having data to be transmitted via a distributed antenna system;
generate, subsequent to determining that the at least one component from the sub-divided downlink signal corresponds to the at least one sub-band, a transformed downlink signal by performing a frequency transform on the downlink signal, wherein the transformed downlink signal represents the downlink signal in a frequency domain;
determine that the at least one sub-band of the transformed downlink signal includes the data to be transmitted; and
extract the at least one sub-band from the transformed downlink signal; and
a second interface section configured to provide the at least one sub-band extracted from the transformed downlink signal to at least one remote antenna unit of the distributed antenna system remote from the unit;
wherein the processor is configured to extract the at least one sub-band from the transformed downlink signal by being configured to:
provide data for at least one portion of the transformed downlink signal in the frequency domain that corresponds to the at least one sub-band to the at least one remote antenna unit of the distributed antenna system.
10. The unit of claim 9 , wherein the processor is configured to:
provide the frequency transform by executing at least one of a fast Fourier transform algorithm, a discrete Fourier transform algorithm, and a discrete cosine transform algorithm using the downlink signal as an input.
11. The unit of claim 9 , wherein the processor is configured to determine that the at least one sub-band of the transformed downlink signal includes the data to be transmitted by being configured to:
identify, for each of a plurality of portions of the transformed downlink signal in the frequency domain, a respective signal level for the portion; and
determine that at least one of the plurality of portions that corresponds to the at least one sub-band has a signal level exceeding a threshold signal level.
12. The unit of claim 9 , wherein the processor is configured to determine that the at least one sub-band of the transformed downlink signal includes the data to be transmitted by being configured to:
receive a control signal from a base station;
identify, from the control signal, at least one channel used by the base station to transmit downlink signals; and
identify the at least one sub-band from the at least one identified channel.
13. The unit of claim 9 , wherein the processor is configured to discard the additional data for the at least one additional portion by being configured to:
provide a control signal to a combiner module of the unit, wherein the control signal is configured to cause the combiner module to exclude the additional data from a combining operation used to route the data for the at least one portion to the at least one remote antenna unit.
14. The unit of claim 9 , wherein the processor is further configured to determine that at least one additional sub-band lacks data to be transmitted via the distributed antenna system wherein the signal processing section is further configured to:
modify the transformed downlink signal to exclude the at least one additional sub-band; and
reduce a sampling rate of the transformed downlink signal based on the transformed downlink signal being modified to exclude the at least one additional sub-band.
15. The unit of claim 9 , wherein the second interface section is further configured to receive a plurality of frequency-transformed uplink signals from a plurality of remote antenna units of the distributed antenna system;
wherein the processor is further configured to identify a subset of sub-bands from the plurality of transformed uplink signals that include uplink data to be transmitted via the distributed antenna system;
wherein the signal processing section is further configured to combine the subset of sub-bands for transmission to the base station and excluding sub-bands other than the subset of sub-bands that include the uplink data.
16. The unit of claim 9 , wherein the at least one portion of the transformed downlink signal includes at least one bin.
17. A distributed antenna system comprising:
a unit configured to:
receive a downlink signal;
sub-divide the downlink signal into a sub-divided downlink signal having a plurality of downlink signal components in a time domain, wherein each of the plurality of downlink signal components corresponds to a respective sub-band;
determine that at least one component of the plurality of downlink signal components corresponds to at least one sub-band having data to be transmitted via the distributed antenna system;
generate, subsequent to determining that the at least one component from the sub-divided downlink signal corresponds to the at least one sub-band, a transformed downlink signal by performing a frequency transform on the downlink signal, wherein the transformed downlink signal represents the downlink signal in a frequency domain;
determine that the at least one sub-band of the transformed downlink signal includes the data to be transmitted;
extract the at least one sub-band from the transformed downlink signal, and
provide the at least one sub-band extracted from the transformed downlink signal to at least one remote antenna unit; and
the at least one remote antenna unit configured to:
receive, from the unit, the at least one sub-band extracted from the transformed downlink signal;
generate a wireless RF signal based on the at least one sub-band, and transmit the wireless RF signal to a terminal device;
wherein the unit is configured to extract the at least one sub-band from the transformed downlink signal by being configured to:
provide data for at least one portion of the transformed downlink signal in the frequency domain that corresponds to the at least one sub-band to the at least one remote antenna unit.
18. The distributed antenna system of claim 17 , wherein the unit is configured to perform the frequency transform by executing at least one of a fast Fourier transform algorithm, a discrete Fourier transform algorithm, and a discrete cosine transform algorithm using the downlink signal as an input.
19. The distributed antenna system of claim 16 , wherein the unit is configured to determine that the at least one sub-band of the transformed downlink signal includes the data to be transmitted by being configured to:
identify, for each of a plurality of portions of the transformed downlink signal in the frequency domain, a respective signal level for the portion; and
determine that at least one of the plurality of portions that corresponds to the at least one sub-band has a signal level exceeding a threshold signal level.
20. The distributed antenna system of claim 16 , wherein the at least one portion of the transformed downlink signal includes at least one bin.