Transport data reduction for DAS systems
An endpoint element of a distributed antenna system includes processing circuitry configured for processing a plurality of digital signals for conditioning the signals and compression circuitry configured for compressing at least one of the digital signals according to a compression scheme to yield at least one compressed digital signal and compression settings. The digital signals are combined into a single digital stream and combined and time division multiplexed onto a serial data link with the compression settings. The digital signals are also transmitted with compression settings to another endpoint element over the serial data link.
1. An endpoint element of a distributed antenna system having multiple endpoints coupled together by serial data links, comprising:
processing circuitry configured to process a plurality of digital signals including a first digital signal corresponding to a first signal received on a first signal path and a second digital signal corresponding to a second signal received on a second signal path separate from the first signal path, wherein the processing circuitry includes adaptive filtering circuitry configured to filter the first digital signal to produce a filtered first digital signal;
circuitry configured to determine a difference signal that is reflective of a difference between the second digital signal and the first filtered digital signal; and
circuitry configured to transmit the first digital signal and the determined difference signal to a second endpoint of the distributed antenna system having multiple endpoints over a serial data link.
2. The endpoint element of claim 1 , wherein the adaptive filtering circuitry comprises one of:
a least mean square filter; or
a recursive least squares filter.
3. The endpoint element of claim 1 , wherein the determined difference signal is provided as feedback to the adaptive filtering circuitry, wherein the adaptive filtering circuitry is configured to adjust filter coefficients based on the determined difference signal.
4. The endpoint element of claim 3 , wherein the adaptive filtering circuitry is configured to adjust the filter coefficients to minimize the determined difference signal.
5. The endpoint element of claim 1 , wherein the processing circuitry configured to process a plurality of digital signals is configured to generate filter coefficients when filtering the first digital signal,
wherein the circuitry configured to transmit the first digital signal and the determined difference signal is configured to transmit the filter coefficients to the second endpoint over the serial data link.
6. The endpoint element of claim 1 , wherein the first digital signal and the second digital signal comprise one of Multiple-Input Multiple-Output (MIMO) signals or diversity signals.
7. A distributed antenna system, comprising:
a first endpoint of the distributed antenna system including:
processing circuitry configured to process a plurality of digital signals including a first digital signal corresponding to a first signal received on a first signal path and a second digital signal corresponding to a second signal received on a second signal path separate from the first signal path, wherein the processing circuitry includes adaptive filtering circuitry configured to filter the first digital signal to produce a filtered first digital signal;
circuitry configured to determine a difference signal that is reflective of a difference between the second digital signal and the first filtered digital signal; and
circuitry configured to transmit the first digital signal and the determined difference signal over a serial data link; and
a second endpoint of the distributed antenna system including:
circuitry configured to receive the first digital signal and the determined difference signal from the serial data link; and
circuitry configured to reconstruct the second digital signal from the first digital signal and the determined difference signal.
8. The distributed antenna system of claim 7 , wherein the processing circuitry configured to process a plurality of digital signals is configured to generate filter coefficients when filtering the first digital signal,
wherein the circuitry configured to transmit the first digital signal and the determined difference signal is configured to transmit the filter coefficients to the second endpoint over the serial data link.
9. The distributed antenna system of claim 8 , wherein the circuitry configured to reconstruct the second digital signal from the first digital signal and the determined difference signal is configured to derive the second digital signal using the first digital signal, the determined difference signal, and the filter coefficients.
10. The distributed antenna system of claim 9 , wherein the circuitry configured to reconstruct the second digital signal from the first digital signal and the determined difference signal comprises a configurable filter.
11. The distributed antenna system of claim 10 , wherein the configurable filter is configured to:
generate another filtered first digital signal by filtering the first digital signal received from the serial data link using the filter coefficients; and
generate the second digital signal by adding the another filtered first digital signal to the determined difference signal.
12. The distributed antenna system of claim 7 , wherein the first digital signal and the second digital signal comprise one of Multiple-Input Multiple-Output (MIMO) signals or diversity signals.
13. The distributed antenna system of claim 7 , wherein the determined difference signal is provided as feedback to the adaptive filtering circuitry, wherein the adaptive filtering circuitry is configured to adjust filter coefficients based on the determined difference signal.
14. The distributed antenna system of claim 13 , wherein the adaptive filtering circuitry is configured to adjust the filter coefficients to minimize the determined difference signal.
15. A method of transmitting digital data between endpoints of a distributed antenna system, comprising:
processing a plurality of digital signals at one endpoint of the distributed antenna system including a first digital signal corresponding to a first signal received on a first signal path and a second digital signal corresponding to a second signal received on a second signal path separate from the first signal path;
filtering the first digital signal using an adaptive filter to produce a filtered first digital signal;
determining a difference signal that is reflective of a difference between the second digital signal and the first filtered digital signal; and
transmitting the first digital signal and the determined difference signal to a second endpoint of the distributed antenna system over a serial data link.
16. The method of claim 15 , further comprising:
providing the determined difference signal as feedback to the adaptive filter; and
adjusting filter coefficients of the adaptive filter based on the determined difference signal.
17. The method of claim 16 , wherein adjusting filter coefficients of the adaptive filter based on the determined difference signal comprises adjusting the filter coefficients to minimize the determined difference signal.
18. The method of claim 15 , further comprising generating filter coefficients when filtering the first digital signal and transmitting the filter coefficient to the second endpoint over the serial data link.
19. The method of claim 15 , further comprising, at the second endpoint:
generating another filtered first digital signal by filtering the first digital signal using a configurable filter; and
deriving the second digital signal by adding the determined difference signal to the another filtered first digital signal at the second endpoint.
20. The method of claim 15 , wherein the first digital signal and the second digital signal are one of multiple-input multiple-output (MIMO) signals or diversity signals.