Compression and decompression between elements of a wireless communications system (WCS)
View Patent ↗Systems and methods for compression and decompression between elements of a wireless communications system (WCS) such as a distributed antenna system (DAS) contemplate performing a fast Fourier transform (FFT) operation before compression and transmission across a transport medium in a DAS. Further, a size of an FFT block may be varied based on latency requirements. For example, the FFT block size may be based on a sampling rate extracted from channel information. By selecting the FFT block size to meet latency requirements, overall throughput across the transport medium may be increased.
1. A device comprising:
an input configured to receive a signal from a remote source, wherein the input is configured to receive a plurality of input signals in a corresponding plurality of channels;
a compression unit coupled to the input, the compression unit comprising:
a size calculator unit configured to evaluate channel requirements to determine a fast Fourier transform (FFT) block size, wherein the size calculator unit comprises a look-up table that compares the channel requirements to channel information to determine the FFT block size;
a variable-sized FFT unit coupled to the size calculator unit and configured to:
receive digital samples based on the signal; and
perform an FFT operation thereon to produce a transformed signal; and
a transformed signal compression unit coupled to the variable-sized FFT unit and configured to apply a compression algorithm on the transformed signal to produce a compressed signal; and
a fronthaul interface coupled to the compression unit and configured to:
receive the compressed signal;
couple to a transport medium; and
send the compressed signal over the transport medium.
2. The device of claim 1 , wherein the device comprises a head end unit.
3. The device of claim 2 , wherein the input configured to receive the signal from the remote source is configured to receive the signal from a base station.
4. The device of claim 1 , wherein the compression unit comprises a hardware circuit.
5. The device of claim 1 , wherein the compression unit comprises a control circuit with software.
6. The device of claim 1 , wherein the device comprises a remote unit.
7. The device of claim 6 , wherein the input comprises an antenna configured to receive a radio frequency (RF) signal from a wireless communication device.
8. The device of claim 1 , wherein the input is configured to receive a plurality of input signals in a corresponding plurality of channels.
9. The device of claim 8 , wherein the compression unit further comprises a scheduler configured to process the plurality of channels.
10. The device of claim 1 , wherein the size calculator unit is configured to receive common public radio interface (CPRI) channel information and derive the channel requirements therefrom.
11. The device of claim 1 , wherein at least one channel requirement comprises latency.
12. The device of claim 11 , wherein at least a second channel requirement comprises bandwidth.
13. The device of claim 1 , wherein the variable-sized FFT unit comprises an upsampling unit configured to insert zeros into a sample before performing an FFT operation.
14. The device of claim 1 , further comprising a switch and a bypass route configured to bypass selectively the variable-sized FFT unit.
15. The device of claim 1 , further comprising:
a second input configured to be coupled to the fronthaul interface; and
a decompression unit configured to decompress signals received through the second input.
16. The device of claim 15 , wherein the decompression unit comprises:
a received signal decompression unit configured to produce a decompressed signal; and
a variable-sized inverse FFT (IFFT) unit coupled to the received signal decompression unit and configured to:
receive the decompressed signal; and
perform an IFFT operation thereon.
17. The device of claim 15 , wherein the decompression unit further comprises a decompression block size calculator.
18. A wireless communications system (WCS), comprising:
a head end unit, wherein the head end unit comprises:
an electrical-to-optical (E/O) converter configured to convert a plurality of downlink communications signals into a plurality of downlink optical communications signals, respectively; and
an optical-to-electrical (O/E) converter configured to convert a plurality of uplink optical communications signals into a plurality of uplink communications signals, respectively; and
a plurality of remote units each coupled to the head end unit via a transport medium, each remote unit of the plurality of remote units comprising:
a respective O/E converter configured to convert a respective one of the plurality of downlink optical communications signals into a respective one of the plurality of downlink communications signals; and
a respective E/O converter configured to convert a respective one of the plurality of uplink communications signals into a respective one of the plurality of uplink optical communications signals;
wherein the head end unit comprises a compression unit, the compression unit comprising:
a size calculator unit configured to evaluate channel requirements to determine a fast Fourier transform (FFT) block size;
a variable-sized FFT unit coupled to the size calculator unit and configured to:
perform an FFT operation on digital samples to produce a transformed signal; and
a transformed signal compression unit coupled to the variable-sized FFT unit and configured to apply a compression algorithm on the transformed signal to produce a compressed signal; and
a fronthaul interface coupled to the compression unit and configured to:
receive the compressed signal;
couple to the transport medium; and
send the compressed signal over the transport medium.
19. The WCS of claim 18 , wherein a remote unit comprises a decompression unit.
20. The WCS of claim 18 , wherein a remote unit comprises a second compression unit.