Prefix Code Construction From Fixed Code Lengths
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Solution Overview
Problem
Existing methods, such as Huffman Coding, cannot construct prefix codes according to given code lengths, which is essential for identifying Radio Link Protocol (RLP) streams in mobile communication systems, affecting message transmission rates.
Innovation Solution
A device and method involving a sort indexer, generator, and sequence regulator to generate prefix codes by sorting code lengths, generating prefix codes by modifying previous codes, and regulating sequences to match given code lengths, while reporting errors if conditions are not met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If Huffman Coding algorithm is used to construct prefix codes, then the average code length is minimized, but the code lengths cannot be controlled to match given requirements
Solution Approach 1:
The patent changes the fundamental parameter of code construction from probability-based optimization to length-based construction. By accepting sorted code lengths as input and systematically generating prefix codes based on these fixed length parameters, the system achieves precise control over code length while maintaining the prefix code property, thus resolving the contradiction between transmission efficiency and length adaptability.
Solution Approach 2:
The patent performs preliminary sorting of the given code lengths before code generation. By pre-sorting the code lengths in ascending order and validating their feasibility (ensuring sum of 2^-li ≤ 1), the system establishes a solid foundation for subsequent prefix code generation, ensuring both the given length requirements and prefix code properties are satisfied from the outset.
2Productivity
If prefix codes are constructed according to given code lengths, then message transmission rate requirements are met, but the average code length may not be optimal
Solution Approach 1:
The patent prioritizes code length as a fixed parameter over average code length optimization. By systematically generating prefix codes based on the sorted given lengths using bit manipulation operations, the system ensures exact adherence to transmission rate requirements while accepting that the average code length may not be minimized, thus resolving the contradiction between productivity and time loss.
3Ease of manufacture
If code lengths are sorted in ascending order, then prefix code generation is simplified, but the original sequence information is lost
Solution Approach 1:
The patent introduces an intermediary mapping relationship between sorted code lengths and original code lengths. By creating and maintaining a correspondence table that records which sorted position maps to which original position, the system simplifies the generation process while preserving the ability to restore the original sequence, thus resolving the contradiction between ease of manufacture and information loss.
4Reliability
If error checking is performed during prefix code generation, then code validity is ensured, but generation time increases
Solution Approach 1:
The patent performs error checking in advance during the sorting and validation phase. By checking whether the sum of 2^-li ≤ 1 before code generation and validating during the generation process, the system ensures code validity is established early, preventing wasted generation time on invalid configurations and thus resolving the contradiction between reliability and generation time.
Data Source
AI summary
The present invention provides a device and method for realizing prefix code construction. The device includes a sort indexer, a generator and a sequence regulator. The sort indexer is used to sort a group of received code lengths to obtain a group of sorted code lengths, and record the position correspondence relationship. The generator receives the sorted code lengths and orderly generates the prefix codes. Except that the first prefix code is preconfigured, the generator generates a current prefix code by adding one to the adjacently previous prefix code and then shifting left by a certain number of bits. The sequence regulator is used to receive the prefix codes corresponding to the sorted code lengths, and regulates the sequence of the prefix codes corresponding to the sorted code lengths according to the position correspondence relationship recorded by the sort indexer to obtain the prefix codes corresponding to the code lengths.