Automatic gain control configuration for a wideband distributed antenna system
One embodiment is directed to a distributed antenna system in which a setting for automatic gain control functionality in at least one unit included in the system (for example, in a hub unit or a remote unit) is determined by interpolating between two detected levels measured at that unit while the automatic gain control functionality is operating in two respective predetermined configurations and by interpolating between two target levels that are associated with the two respective predetermined configurations. In one example, the intersection of the two resulting interpolations is used to determine the setting for the automatic gain control functionality.
1. A distributed antenna system comprising:
a hub unit configured to receive an original downlink signal comprising a plurality of downstream frequency bands, each of the plurality of downstream frequency bands associated with a respective radio frequency channel; and
a remote antenna unit that is communicatively coupled to the hub unit;
wherein the hub unit is configured to communicate a downstream transport signal from the hub unit to the remote antenna unit, wherein the transport signal is derived from the original downlink signal received at the hub unit;
wherein the remote antenna unit uses the downstream transport signal to generate a downstream radio frequency signal for radiation from an antenna associated with the remote antenna unit, wherein the downstream radio frequency signal comprises at least a subset of the plurality of downstream frequency bands;
wherein the remote antenna unit comprises automatic gain control functionality operable to automatically control at least one of a gain in the remote antenna unit and a slope in the remote antenna unit; and
wherein the remote antenna unit uses a data structure comprising a plurality of entries, each of the entries associating at least one setting for the automatic gain control functionality in the remote antenna unit with a target level for a pilot tone included in the downstream transport signal;
wherein at least one setting for the automatic gain control functionality in the remote antenna unit is derived from:
a first interpolation between:
a first data point that is associated with a detected level for the at least one pilot tone while the automatic gain control functionality is configured in accordance with a first one of the plurality of entries; and
a second data point that is associated with a detected level for the at least one pilot tone while the automatic gain control functionality is configured in accordance with a second one of the plurality of entries; and
a second interpolation between:
a third data point that is associated with a target level for the at least one pilot tone stored in the first one of the plurality of entries; and
a fourth data point that is associated with a target level for the at least one pilot tone stored in the second one of the plurality of entries.
2. The system of claim 1 , wherein the downstream transport signal comprises a first pilot tone and a second pilot tone;
wherein the first data point is associated with detected levels for the first and second pilot tones while the automatic gain control functionality is configured in accordance with the first one of the plurality of entries;
wherein the second data point is associated with detected levels for the first and second pilot tones while the automatic gain control functionality is configured in accordance with the second one of the plurality of entries; and
wherein the third data point is associated with target levels for the first and second pilot tones stored in the first one of the plurality of entries; and
wherein the fourth data point is associated with target levels for the first and second pilot tone stored in the second one of the plurality of entries.
3. The system of claim 2 , wherein the first data point is associated with a difference between the detected levels for the first and second pilot tones while the automatic gain control functionality is configured in accordance with the first one of the plurality of entries;
wherein the second data point is associated with a difference between the detected levels for the first and second pilot tones while the automatic gain control functionality is configured in accordance with the second one of the plurality of entries;
wherein the third data point is associated with a difference between the target levels for the first and second pilot tones stored in the first one of the plurality of entries; and
wherein the fourth data point is associated with a difference between the target levels for the first and second pilot tones stored in the second one of the plurality of entries.
4. The system of claim 1 , wherein the at least one setting for the automatic gain control functionality in the remote antenna unit is derived by determining an intersection between the first interpolation and the second interpolation.
5. The system of claim 1 , wherein the downstream transport signal comprises intermediate frequency versions of the original downstream radio frequency signals.
6. The system of claim 1 , wherein the system comprises a plurality of remote antenna units.
7. The system of claim 1 , wherein the remote antenna unit comprises a master remote antenna unit that processes the downstream transport signal.
8. The system of claim 1 , wherein the remote antenna unit comprises at least one slave unit that produces the downstream radio frequency signal.
9. The system of claim 1 , wherein a frequency band specific gain offset is applied to at least one of the at least a subset of the plurality of frequency bands included in the downstream radio frequency signal.
10. The system of claim 9 , wherein the frequency band specific gain offset is derived from the first interpolation and the second interpolation.
11. The system of claim 1 , wherein the hub unit and the remote antenna unit are a part of an analog distributed antenna system.
12. The system of claim 1 , wherein the hub unit and the remote antenna unit are a part of an analog subsystem included in a hybrid digital-analog distributed antenna system.
13. The system of claim 1 , wherein each of the plurality of entries is generated at least in part using a measured swept response cascaded with a modeled loss for a medium communicatively coupling the hub unit to the remote antenna unit.
14. The system of claim 13 , wherein cascading the measured swept response with the modeled loss for the medium communicatively coupling the hub unit to the remote antenna unit produces a cascade response, wherein a first order least squares fit is performed on the cascade response to derive a closed-from equation to determine an equivalent length for the medium communicatively coupling the hub unit to the remote antenna unit.
15. The system of claim 1 , wherein the remote antenna unit is configured to receive an original upstream signal comprising a plurality of upstream frequency bands, each of the plurality of upstream frequency bands associated with a respective radio frequency channel; and
wherein the remote antenna unit is configured to communicate an upstream transport signal from the remote antenna unit to the hub unit;
wherein the hub unit uses the upstream transport signal to generate an upstream signal, wherein the upstream signal comprises at least a subset of the plurality of upstream frequency bands;
wherein the hub unit comprises automatic gain control functionality operable to automatically control at least one of a gain in the hub unit and a slope in the hub unit; and
wherein the hub unit uses a data structure comprising a plurality of upstream entries, each of the upstream entries associating at least one setting for the automatic gain control functionality in the hub unit with a target level for an upstream pilot tone included in the upstream transport signal;
wherein at least one setting for the automatic gain control functionality in the hub unit is derived from:
a third interpolation between:
a fifth data point that is associated with a detected level for the at least one upstream pilot tone while the automatic gain control functionality in the hub unit is configured in accordance with a first one of the plurality of upstream entries; and
a sixth data point that is associated with a detected level for the at least one upstream pilot tone while the automatic gain control functionality in the hub unit is configured in accordance with a second one of the plurality of upstream entries; and
a fourth interpolation between:
a seventh data point that is associated with a target level for the at least one upstream pilot tone stored in the first one of the plurality of upstream entries; and
an eighth data point that is associated with a target level for the at least one upstream pilot tone stored in the second one of the plurality of upstream entries.
16. A system for distributing a first radio frequency signal comprising a plurality of frequency bands, each of the plurality of frequency bands associated with a respective radio frequency channel, the system comprising:
a first unit configured to receive a first signal derived from the first radio frequency signal; and
a second unit that is communicatively coupled to the first unit;
wherein the first unit is configured to communicate a transport signal from the first unit to the second unit, wherein the transport signal is derived from the first signal received at the first unit;
wherein the second unit uses the transport signal to generate a second radio frequency signal for radiation from an antenna associated with the second unit, wherein the second radio frequency signal comprises at least a subset of the plurality of frequency bands;
wherein the second unit comprises automatic gain control functionality operable to automatically control at least one of a gain in the second unit and a slope in the second unit; and
wherein the second unit uses a data structure comprising a plurality of entries, each of the entries associating at least one setting for the automatic gain control functionality in the second unit with a target level for a pilot tone included in the transport signal;
wherein at least one setting for the automatic gain control functionality in the second unit is derived from:
a first interpolation between:
a first data point that is associated with a detected level for the at least one pilot tone while the automatic gain control functionality is configured in accordance with a first one of the plurality of entries; and
a second data point that is associated with a detected level for the at least one pilot tone while the automatic gain control functionality is configured in accordance with a second one of the plurality of entries; and
a second interpolation between:
a third data point that is associated with a target level for the at least one pilot tone stored in the first one of the plurality of entries; and
a fourth data point that is associated with a target level for the at least one pilot tone stored in the second one of the plurality of entries.
17. The system of claim 16 , wherein the system comprises at least one of a distributed antenna system, repeater, and distributed base station system.
18. A system for distributing a first radio frequency signal comprising a plurality of frequency bands, each of the plurality of frequency bands associated with a respective radio frequency channel, the system comprising:
a first unit configured to receive the first radio frequency signal from an antenna associated with the first unit;
a second unit that is communicatively coupled to the first unit;
wherein the first unit is configured to communicate a transport signal from the first unit to the second unit, wherein the transport signal is derived from the first radio frequency signal received at the first unit;
wherein the second unit uses the transport signal to generate a second signal for communication to a base station, wherein the second signal comprises at least a subset of the plurality of frequency bands;
wherein the second unit comprises automatic gain control functionality operable to automatically control at least one of a gain in the second unit and a slope in the second unit; and
wherein the second unit uses a data structure comprising a plurality of entries, each of the entries associating at least one setting for the automatic gain control functionality in the second unit with a target level for a pilot tone included in the transport signal;
wherein at least one setting for the automatic gain control functionality in the second unit is derived from:
a first interpolation between:
a first data point that is associated with a detected level for the at least one pilot tone while the automatic gain control functionality is configured in accordance with a first one of the plurality of entries; and
a second data point that is associated with a detected level for the at least one pilot tone while the automatic gain control functionality is configured in accordance with a second one of the plurality of entries; and
a second interpolation between:
a third data point that is associated with a target level for the at least one pilot tone stored in the first one of the plurality of entries; and
a fourth data point that is associated with a target level for the at least one pilot tone stored in the second one of the plurality of entries.
19. The system of claim 18 , wherein the system comprises at least one of a distributed antenna system, repeater, and distributed base station system.
20. A method of characterizing a signal path in a system operable to distribute radio frequency signals having a plurality of frequency bands, the method comprising:
sweeping a signal through a frequency range that includes the plurality of frequency bands;
measuring a corresponding swept response;
calculating an equivalent length for a communication medium associated with the system based on the swept response;
adjusting a gain setting based on the equivalent length; and
storing at least one setting associated with the signal path for use in configuring the system.
21. The method of claim 20 , wherein the system comprises at least one of a distributed antenna system, repeater, and distributed base station system.
22. The method of claim 20 , wherein the signal path being characterized includes at least one of automatic gain control functionality, pilot tone functionality, and band-specific gain adjustment functionality.
23. The method of claim 20 , wherein the at least one setting associated with the signal path comprises at least one of:
a gain setting;
a slope setting;
a gain offset for at least one of the plurality of frequency bands; and
a level for a pilot tone.
24. The method of claim 20 , wherein the equivalent length is calculated based on a closed form equation derived from a least squares fit function based on a measured swept response cascaded with a modeled loss for the medium associated with the system.