CRAN I/Q Compression by Removing Meaningless Higher-Order Bits
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Solution Overview
Problem
In Cloud Radio Access Networks (CRAN), the separation of digital and radio units leads to high data transmission requirements between the digital unit (DU) and radio unit (RU), resulting in increased capital and operational expenditures due to the need for extensive optical cabling, with existing methods like non-integral multiple re-sampling having limitations in significantly reducing data transmission.
Innovation Solution
A method of compressing and decompressing In-phase/Quadrature (I/Q) data by calculating and removing meaningless higher-order bits, using Huffman coding, and transmitting header information to minimize data transmission, with the compression process applied in units of basic frames defined in the Common Public Radio Interface (CPRI) standard.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-integral multiple re-sampling is used to reduce data amount, then data transmission amount is reduced, but the reduction is limited and cannot achieve significant compression
Solution Approach 1:
The patent segments the I/Q data into multiple subcarriers after FFT transformation. Each subcarrier's real and imaginary parts are processed independently to identify and remove meaningless higher-order bits. This segmentation allows targeted compression of redundant information across different frequency components, achieving significant overall data reduction beyond what uniform re-sampling can accomplish.
Solution Approach 2:
The patent extracts and removes meaningless higher-order bits from each subcarrier's real and imaginary parts. By calculating the maximum absolute values of these components and determining the meaningful bit depth, the system extracts only the necessary significant bits for reconstruction, discarding the redundant higher-order bits that do not contribute to signal quality.
2Productivity
If more optical cables are used to connect DU and RU, then signal transmission capacity increases, but capital expenditure and operational expenditure increase significantly
Solution Approach 1:
The patent merges multiple frequency assignment (FA) and sector signals into a single optical cable by applying compression to the I/Q data. Through FFT transformation and removal of meaningless higher-order bits from each subcarrier, the system combines what would traditionally require multiple separate cable connections into one compressed data stream, reducing CAPEX and OPEX while maintaining transmission capacity.
3Quantity of substance
If higher-order bits are removed from I/Q samples, then data amount is reduced, but transmission precision may be affected
Solution Approach 1:
The patent applies local quality by treating each subcarrier's real and imaginary parts differently based on their specific characteristics. For each subcarrier, the system calculates the maximum absolute value of the real part and imaginary part separately, determining the meaningful bit depth locally for each component. This allows optimal precision retention for each subcarrier while achieving overall compression, rather than applying a uniform bit reduction across all data.
Data Source
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AI summary
A method of compressing In-phase/Quadrature (I/Q) data transmitted and received between a Digital Unit (DU) and a Radio Unit (RU) in a Cloud Radio Access Network (CRAN) structure is disclosed. The method includes (a) calculating a minimum value DiMSB among meaningless higher-order bit digits DMSBi,jwith respect to each of j-th I/Q samples having a predetermined resolution among i-th unit blocks that are units of compression, and (b) transmitting each of the samples after each of the samples is converted into a binary number and DiMSB number of higher-order bits, excluding a sign bit, are removed.