DISTRIBUTED ANTENNA SYSTEM HAVING HIGH NEAR FAR PERFORMANCE

• US 20140248050A1
• Filed: 03/03/2014
• Published: 09/04/2014
• Est. Priority Date: 03/02/2013
• Status: Active Grant

• Current Assignee: Westell Incorporated (Westell Technologies Incorporated)
• Original Assignee: Cellular Specialties Incorporated (Westell Technologies Incorporated)
• Inventors: Crilly, William J. Jr., Schwartz, David J.
• Granted Patent: US 9,467,230 B2
• Time in Patent Office: Days
• US Class Current: 398/38
• CPC Class Codes: H04B 10/25753 Distribution optical network, e.g. between a base station and a plurality of remote units
• CPC Class Codes: H04B 10/25758 between a central unit and a single remote unit by means of an optical fibre

Abstract

The system and method for ameliorating the effect of close-in user equipment up to a point where the user equipment itself limits the performance. The system and method utilizes a digital filter in front of the LASER modulator being applied to the LASER. Additionally, total power detectors may be used at input to prevent unwanted signals from overloading stages in front of the LASER. In uplink and downlink directions, bidirectional digital filtering in the RUs allows the selective use of a given RU in a given sub-band, by a given WSP. The use of digital filtering in the RU reduces the need for hardware RF switching at the head end to accomplish the same objective of signal flexibility, by one of more WSPs, providing one or more sectors exists within the DAS.

Claims

1. A distributed antenna system comprising

one or more interfaces to one or more base stations;

one or more optical paths;

one or more analog to digital and/or digital to analog converters;

one or more remote units, having a plurality of sub-bands and digital signal processing;

a photodiode;

a LASER;

one or more server antennas; and

uplink and/or downlink digital filtering, wherein the digital filtering is in one or more remote units thereby improving the uplink and/or downlink Near Far performance of the distributed antenna system.

2. The distributed antenna system of claim 1, wherein selective uplink and downlink filtering occurs at a first remote unit to allow the selective transmission and reception of a selected sub-band within the first remote unit.

3. The distributed antenna system of claim 2, wherein a downlink combined signal is carried by an optical path to a second remote unit, transmitting the downlink combined signal, wherein the downlink combined signal is filtered by the first remote unit, thereby reducing the requirement for hardware switching of signals.

4. The distributed antenna system of claim 1, further comprising a total power detector to prevent unwanted signals from overloading stages in front of the LASER.

5. The distributed antenna system of claim 1, further comprising a sub-band specific uplink automatic gain control feature within the digital signal processing in the remote unit.

6. The distributed antenna system of claim 1, further comprising one or more detectors operating within the digital signal processing, and in front of the analog to digital converter, to protect the analog to digital converter from overload.

7. The distributed antenna system of claim 1, wherein the digital filtering within a remote can be eliminated when Near Far performance degradation does not occur.

8. The distributed antenna system of claim 5, wherein uplink attacks and decay times operating in the automatic gain control feature are dependent on the technology used for the downlink of the same sub-band.

9. The distributed antenna system of claim 8, wherein the selection of the delay of a digital filter in the uplink and/or downlink paths is used to equalize the delay of the transmission time of signals from multiple remote units, while simultaneously meeting the rejection requirements of the digital filter.

10. The distributed antenna system of claim 1, wherein flexible signal selection is accomplished without requiring an RF switch at the head end, when there are no co-channel signals within a DAS.