Polar Code Blind Decoding With CRC State Changes for False Alarm Reduction
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, the ambiguity in payload size and high false alarm rates during blind decoding of polar codes lead to incorrect information parsing and decoding errors, as users cannot accurately determine the bit length of transmitted control information.
Innovation Solution
A base station generates polar-encoded codewords with initialized error detection code (EDC) algorithms in non-all-zero states, scrambles or interleaves bits, and includes multiple EDC values to assist users in determining the correct bit length and reduce false alarms by supporting early termination decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple bit length hypotheses are used for blind decoding, then the ability to detect control information is improved, but the false alarm rate increases and size ambiguity occurs
Solution Approach 1:
The patent introduces an intermediary verification mechanism (CRC check with non-zero initialization) that acts as a mediator between multiple decoding hypotheses and the final decision. This intermediary step allows the system to evaluate multiple hypotheses while using the CRC verification as a filtering mechanism to eliminate false alarms and determine the correct bit length.
Solution Approach 2:
The patent changes the initialization parameter of the CRC algorithm from the conventional all-zero state to a non-all-zero state. This parameter change fundamentally alters the CRC calculation results, ensuring that different bit length hypotheses produce distinct CRC values and enabling accurate bit length determination while reducing false alarms.
2Ease of operation
If conventional CRC initialization is used, then decoding simplicity is maintained, but false alarm rate increases due to repeating cyclic redundancy check states
Solution Approach 1:
The patent modifies the initialization parameter of the CRC algorithm from all-zero to non-all-zero. This single parameter change prevents the generation of repeating CRC states that cause false alarms, while maintaining the overall simplicity of the decoding process. The change is transparent to the decoding structure and requires minimal additional complexity.
3Measurement precision
If EDC algorithm is initialized to non-all-zero state, then false alarm rate is reduced and bit length determination is improved, but computational complexity increases
Solution Approach 1:
The patent implements a simple parameter change in the EDC initialization process. Rather than requiring complex additional processing, the solution modifies a single initialization parameter (from all-zero to non-all-zero), which achieves improved bit length determination and false alarm reduction with minimal increase in computational complexity.
Data Source
AI summary
Size ambiguity and false alarm rate reduction for polar codes. A user equipment (UE) may determine a decoding candidate bit sequence for a polar-encoded codeword having a codeword size based on a decoding hypothesis for control information having a particular bit length of multiple different bit lengths for the codeword size. The UE may calculate an error detection code (EDC) value for a payload portion of the decoding candidate bit sequence using an EDC algorithm, and may initialize an EDC variable state with at least one non-zero bit value. Scrambling or interleaving of bits may also be performed prior to, or after, polar encoding and may depend on the bit length. In examples, information bits may be bit-reversed prior to generating an EDC value. In examples, the encoded bits may include multiple EDC values to assist the UE in performing early termination and to reduce a false alarm rate.