CPRI I/Q Compression by Removing Redundant Bits in C-RAN
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Solution Overview
Problem
In Cloud Radio Access Networks (CRAN), there is a significant challenge in reducing the amount of data transmitted and received between digital units (DU) and radio units (RU), leading to high capital and operational expenditures due to the large amount of I/Q data being exchanged, which current methods like non-integral multiple re-sampling cannot effectively address.
Innovation Solution
A method is introduced that compresses I/Q data by calculating and removing meaningless higher-order bits and optionally lower-order bits, using a header for code word information, and applying lossless coding like Huffman coding, all within the framework of the Common Public Radio Interface (CPRI) standard, to minimize data transmission while ensuring a minimum compression rate.
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 compression rate is insufficient and fundamental limitation exists
Solution Approach 1:
The patent segments I/Q data into multiple groups and applies different compression processes to each group. Specifically, it divides the data stream into first groups and second groups, applying different bit removal strategies and compression techniques to each segment, thereby achieving higher overall compression rates while maintaining signal integrity.
Solution Approach 2:
The patent dynamically changes compression parameters based on data characteristics. It calculates standard deviations of I and Q components, determines optimal bit removal amounts based on these statistical parameters, and adjusts compression intensity accordingly. This parameter-based adaptation enables significant compression while maintaining quality within acceptable ranges.
2Quantity of substance
If more optical cables are used to connect DU and RU, then signal transmission capacity is increased, but facility costs and CAPEX are significantly increased
Solution Approach 1:
The patent extracts and removes redundant information from I/Q data streams before transmission. By calculating and removing meaningless higher-order bits and applying lossless coding to extract only essential information, it reduces the data volume requiring optical cable bandwidth, thereby reducing the number of cables needed and associated facility costs.
Solution Approach 2:
The patent merges multiple data streams and applies joint compression techniques. By processing I and Q components together and applying correlated compression strategies, it achieves more efficient utilization of available transmission capacity, reducing the total bandwidth and cable infrastructure required.
3Quantity of substance
If data compression is applied to I/Q data, then data transmission amount is reduced, but data loss and EVM deterioration may occur
Solution Approach 1:
The patent employs dynamic compression strategies that adapt to changing data characteristics. It continuously monitors standard deviations and signal properties, adjusting the number of bits to remove and compression intensity in real-time. This dynamic adaptation ensures that compression maintains data quality within acceptable EVM limits while maximizing compression ratios.
Solution Approach 2:
The patent implements feedback mechanisms where compression performance is monitored and used to adjust subsequent compression parameters. By measuring EVM and data quality metrics after compression, it feeds this information back to optimize the compression process, ensuring quality thresholds are maintained while achieving maximum compression.
Data Source
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 Di,jMSB with 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.