Delta-Sigma Carrier Digitization for Multi-RAT Mobile Fronthaul
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Solution Overview
Problem
Conventional digital mobile fronthaul (MFH) networks face challenges in supporting high-order modulation formats and multiple radio access technologies (RATs) due to low spectral efficiency and compatibility issues, particularly with CPRI, which is cost-prohibitive and lacks support for Wi-Fi and 5G-NR.
Innovation Solution
The implementation of a multiband delta-sigma digitization interface that oversamples and noise-shapes signals to push quantization noise out of band, allowing for simultaneous digitization of multiple RATs without frequency conversion, thereby eliminating the need for DAC and RF devices at remote radio heads and enhancing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional digital MFH networks use CPRI for digitization, then compatibility with existing systems is maintained, but spectral efficiency is low and cost is prohibitive
Solution Approach 1:
The patent changes the digitization parameters by using delta-sigma modulation with oversampling and noise shaping, transitioning from conventional CPRI digitization methods. This allows simultaneous digitization of multiple RATs with different sampling rates and modulation formats, improving spectral efficiency while maintaining system compatibility through standardized interfaces.
Solution Approach 2:
The patent creates a universal digitization interface that can handle multiple radio access technologies (4G-LTE, Wi-Fi, 5G-NR) simultaneously. The delta-sigma ADC architecture provides multi-functionality by accommodating different sampling rates, modulation formats, and bandwidth requirements through a single standardized interface, eliminating the need for separate digitization paths for each RAT.
2Adaptability or versatility
If multiple RATs are aggregated in heterogeneous MFH networks, then service diversity and coverage are enhanced, but system complexity and cost increase
Solution Approach 1:
The patent merges multiple radio access technology signals into a single aggregated waveform that is transmitted over a shared fiber link. The delta-sigma digitization interface combines 4G-LTE, Wi-Fi, and 5G-NR signals simultaneously, reducing the number of separate transmission paths and simplifying the overall system architecture while maintaining service diversity.
Solution Approach 2:
The patent introduces a standardized digitization interface as an intermediary between the baseband processing unit and remote radio heads. This intermediary layer handles the complexity of multi-RAT aggregation, signal conditioning, and digitization, shielding the rest of the system from implementation details and reducing overall system complexity.
3Productivity
If delta-sigma digitization with oversampling is used, then spectral efficiency is improved and multiple RATs are supported, but quantization noise is generated
Solution Approach 1:
The patent employs periodic noise shaping through the delta-sigma modulation process, where quantization noise is systematically pushed to higher frequency bands through periodic feedback. This allows the useful signal to occupy lower frequency bands with minimal noise, while the shaped noise is filtered out, effectively separating signal from noise through periodic modulation and filtering operations.
Data Source
AI summary
A baseband processing unit includes a baseband processor configured to receive a plurality of component carriers of a radio access technology wireless service, and a delta-sigma digitization interface configured to digitize at least one carrier signal of the plurality of component carriers into a digitized bit stream, for transport over a transport medium, by (i) oversampling the at least one carrier signal, (ii) quantizing the oversampled carrier signal into the digitized bit stream using two or fewer quantization bits.