Distributed Radio Signal Combining for Multi-Operator Mid-Haul
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Solution Overview
Problem
RAN systems face challenges in accommodating multiple network operators and private networks with different cellular technologies, including 3G to O-RAN implementations, while meeting strict 5G latency requirements and managing shared spectrum access.
Innovation Solution
A method for processing downlink and uplink signals from multiple base stations and remote units, involving conversion, frequency shifting, and digital summing of RF and packetized data streams to generate composite signals, accommodating legacy and digital baseband processors, and utilizing MIMO layers to optimize signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If legacy analog RF base station signals are integrated with packetized mid-haul signals of multiple operators, then the RAN system can serve multiple network operators and private networks with different cellular technologies, but the system complexity increases significantly
Solution Approach 1:
The RAN system is segmented into independent functional units: analog RF signal processing path, packetized mid-haul processing path, and a digital summing/composite signal generation path. Each operator's signals are processed separately through their respective paths before being combined, allowing multiple technologies to coexist without increasing individual path complexity
Solution Approach 2:
A digital summing device acts as an intermediary that receives processed signals from both legacy analog base stations and modern packetized baseband processors, converts them to compatible digital formats, and combines them into a unified composite signal. This intermediary handles the complexity of multi-technology integration centrally, leaving individual signal paths relatively simple
2Productivity
If multiple base stations share a frequency band with different cellular technologies, then spectrum utilization is improved, but signal interference and frequency management complexity increase
Solution Approach 1:
The system applies frequency offset shifts to packetized data streams before digital summing, aligning different cellular technologies' carrier frequencies to a common reference. This parameter transformation allows signals from different operators and technologies sharing the same frequency band to be combined without interference, simplifying frequency management
3Measurement precision
If analog RF signals and packetized data streams are converted and summed digitally, then signal integration accuracy is improved, but processing time and computational load increase
Solution Approach 1:
Analog RF signals are converted to digital baseband signals and packetized data streams are processed through baseband offset frequency shifts before the final digital summing operation. This preliminary processing prepares all signals in compatible digital formats with proper frequency alignment, enabling accurate integration while minimizing the time required for the final combining operation
Data Source
AI summary
A distributed radio system has one or more distributed radio processors that processes analog RF signals from a plurality of legacy base station transceivers (BTSs) as well as packetized digital mid-haul data (such as 7.2× data packets) from one or more baseband units. The system digitizes the RF signals and provides baseband frequency offsets to the I/Q time domain data processed from the digital mid-haul data such that each incoming signal is assigned a unique carrier baseband frequency offset so that none of the signals interferes with another. The digital signals are summed and transmitted to one or more remote units. For the uplink, the process is reversed. A supervisor module provides the offset frequencies to the relevant digital baseband signals.