Distributed Antenna System Reverse Path Summation
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Solution Overview
Problem
Distributed antenna systems face challenges in uplink simulcast operations due to non-uniform signal-to-noise ratios and power control issues across heterogeneous remote antenna units, leading to reduced dynamic range and potential digital overflow.
Innovation Solution
The method involves normalizing the noise power of each remote antenna unit to the lowest noise floor and scaling their output gains to maintain optimal signal-to-noise ratios, preventing digital overflow by adjusting gains digitally before signal summation, thereby preserving the dynamic range and ensuring the host unit receives a balanced composite signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital RF signals from multiple RAUs are summed directly at the host unit, then the composite signal is formed for uplink simulcast operation, but non-uniform noise factors and signal-to-noise ratios across heterogeneous RAUs degrade the overall signal quality and dynamic range
Solution Approach 1:
The patent applies local quality by normalizing the noise floor of each RAU individually based on its specific noise factor characteristics. Each RAU's digital RF signal components are scaled by a normalization factor that is locally determined from its noise factor, allowing each component to contribute equally to the composite signal regardless of the RAU's position in the daisy-chain topology or its specific equipment variations.
Solution Approach 2:
The patent changes the parameter of signal scaling by introducing a normalization factor derived from noise factors. The host unit calculates these normalization factors based on the specific noise characteristics of each RAU and applies them to scale the digital RF signal components before summation. This parameter transformation equalizes the contribution of each RAU and optimizes the overall signal-to-noise ratio of the composite uplink signal.
2Device complexity
If RAUs in a daisy-chain configuration receive digital RF signals through sequential coupling, then the system topology is simplified, but signals from RAUs farther from the host unit undergo greater attenuation and accumulate more noise, creating non-uniform signal levels
Solution Approach 1:
The patent implements feedback by having the host unit measure or receive noise factor information from each RAU and use this information to calculate appropriate normalization factors. This feedback loop allows the host unit to compensate for the cumulative noise and attenuation effects in the daisy-chain topology by appropriately scaling each RAU's signal contribution based on its position and characteristics in the chain.
Solution Approach 2:
The patent addresses the non-uniform signal levels caused by daisy-chain topology by transforming the signal parameters through normalization. Each RAU's digital RF signal components are multiplied by a normalization factor that compensates for the position-dependent attenuation and noise accumulation, converting the non-uniform contributions into uniform effective levels at the composite signal stage.
3Ease of operation
If the host unit sends digitized RF signals to multiple RAUs for downlink simulcast, then power control is straightforward, but in the uplink direction the host unit cannot control the power of wireless RF signals received at each RAU
Solution Approach 1:
The patent applies inversion by reversing the traditional power control approach. Instead of the host unit controlling transmit power at RAUs (which works for downlink but not uplink), the system measures the actual received signal characteristics at each RAU and applies compensating normalization factors in reverse - scaling the digital RF signal components to equalize their contributions to the composite uplink signal, effectively achieving power balance through post-reception processing rather than pre-transmission control.
4Reliability
If normalization schemes are applied to equalize digital RF signal components from heterogeneous RAUs, then signal-to-noise ratio is improved, but the complexity of determining appropriate normalization factors increases
Solution Approach 1:
The patent applies self-service by having each RAU measure or report its own noise factor characteristics, which are then used by the host unit to calculate normalization factors. The system utilizes the inherent noise measurements already available at each RAU location, eliminating the need for complex external calibration equipment or procedures. The host unit simply processes the reported noise factors to determine the appropriate scaling factors, making the normalization process self-contained and relatively simple.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
Systems and methods for distributed antenna system reverse path summation using signal-to-noise ratio optimization are provided. In one embodiment, a method for reverse path summation for a distributed antenna system comprises: normalizing an uplink noise floor for a plurality of remote antenna units of a distributed antenna system, wherein the uplink noise floor is normalized based on a first remote antenna unit having a lowest noise floor of the plurality of remote antenna units; and scaling an uplink output gain of each of the plurality of remote antenna units by a scaling factor, wherein the scaling factor attenuates the uplink output gain based on a composite maximum host peak power for a host unit coupled to the plurality of remote antenna units.