Selective Uplink Signal Combining in Distributed Antenna Systems
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Solution Overview
Problem
Distributed antenna systems (DAS) face challenges in combining uplink signals, as indiscriminate combining of noise and signal can increase the noise floor, limiting the number of remote units that can be used and degrading signal quality.
Innovation Solution
A method and unit within the DAS that selectively combine uplink signals by identifying and excluding or attenuating noise-free channels, generating combined uplink signals only from channels with data for transmission to a base station, thereby reducing the noise floor and optimizing signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If uplink transmissions from all remote units are combined indiscriminately, then the power of weak uplink signals is boosted, but the noise floor increases due to combining noise from channels without valid signals
Solution Approach 1:
The system performs preliminary detection at the master unit to identify which remote units have valid uplink signals before combining. This preliminary action prevents noise from units without signals from being combined in the first place, thereby boosting weak signals without increasing the noise floor.
Solution Approach 2:
The master unit receives feedback information from remote units indicating whether they have detected valid uplink signals. This feedback mechanism allows the master unit to make informed decisions about which signals to combine, ensuring that only channels with valid signals contribute to the combined output, thus avoiding noise accumulation.
2Productivity
If the number of remote units is increased to improve coverage, then system capacity is enhanced, but signal quality degrades due to higher noise floor from indiscriminate combining
Solution Approach 1:
Before combining signals from multiple remote units, the system performs preliminary identification to detect which units have valid signals. This allows the system to scale the number of remote units for improved coverage while maintaining signal quality by excluding noise-contributing units from the combining process.
3Adaptability or versatility
If all remote units are utilized to expand coverage area, then system versatility is improved, but the effective number of usable remote units is limited by noise accumulation
Solution Approach 1:
Remote units provide feedback to the master unit about the presence of valid uplink signals. This feedback enables the system to utilize a larger number of remote units for expanded coverage while automatically excluding units that would contribute only noise, thus maintaining signal quality across the extended coverage area.
Data Source
AI summary
Certain aspects involve selectively combining uplink transmissions in a distributed antenna system (“DAS”). For example, a unit of the DAS can receive baseband uplink transmissions from remote units of the DAS via a first channel and a second channel. The unit can generate a first combined uplink signal by combining baseband uplink transmissions received from a first subset of the remote units via the first channel that include data for transmission to a base station. The unit can generate a second combined uplink signal that includes baseband uplink transmissions received from a second subset of the remote units via the second channel and excludes or attenuates baseband uplink transmissions that are received from the first subset of the remote units via the second channel and that lack data for transmission to the base station are excluded or attenuated. The unit can transmit the combined uplink signals to the base station.