NR-PBCH Polar Code Bit Mapping for Decoding Reliability
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Solution Overview
Problem
The decoding performance of the Physical Broadcast Channel (PBCH) in 5G new radio (NR) systems is hindered by the varying reliability of Polar code bit channels, as not all information bits are known to the decoders, leading to suboptimal data bit allocation during transmission.
Innovation Solution
A novel bit mapping method is proposed where timing-related bits known to the decoders are placed at the least reliable Polar code bit positions, improving decoding performance by exploiting known bits during the encoding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bit mapping is used for NR-PBCH transmission, then all 56 data bits are transmitted through Polar code, but decoding performance is limited due to varying channel reliability of different Polar code bit channels
Solution Approach 1:
The patent applies local quality by differentiating the treatment of information bits based on their known status. Known bits (timing-related bits) are mapped to least reliable Polar code bit positions, while unknown bits are mapped to more reliable positions. This selective mapping strategy optimizes decoding performance by exploiting the different reliability characteristics of various Polar code bit channels, with each bit position receiving treatment appropriate to its specific requirements.
2Reliability
If timing-related bits are placed at most reliable Polar code bit positions, then unknown information bits benefit from high reliability, but decoding performance deteriorates because known bits cannot exploit their a priori knowledge
Solution Approach 1:
The patent inverts the conventional mapping approach by placing known bits (timing-related bits) at the least reliable Polar code bit positions rather than at the most reliable positions. This inversion allows the decoder to effectively exploit the known status of these bits, as they are positioned where they can be reliably identified and used to aid decoding of unknown bits. The unknown bits are consequently mapped to more reliable positions, creating an optimized distribution that leverages the known information.
3Productivity
If all 56 data bits are treated equally during encoding, then the encoding process is simple, but decoding latency and complexity increase due to suboptimal bit allocation
Solution Approach 1:
The patent applies preliminary action by performing bit mapping optimization before the actual encoding and decoding processes. The transmitter pre-determines the optimal mapping between information bits and Polar code bit positions based on the known status of timing-related bits. This preliminary arrangement of bits according to their reliability requirements enables the decoder to efficiently exploit known bits and reduce decoding latency, as the optimal bit allocation is established in advance rather than requiring complex real-time decisions.
Data Source
AI summary
A method of new radio physical broadcast channel (NR-PBCH) bit mapping is proposed to improve for NR-PBCH decoding performance under Polar codes. NR-PBCH carries 32 information bits and 24 CRC bits. Specifically, NR-PBCH uses 512-bit Polar codes to carry total 56 data bits. Different Polar code bit channels have different channel reliability. As a general rule, the most reliable Polar code bit channels are used for the 56 data bits. In accordance with a novel aspect, within the 32 NR-PBCH information bits, some of the information bits that can be known to the decoders under certain conditions and therefore are placed at the least reliable Polar code bit positions. As a result, by mapping the NR-PBCH data bits properly at the input bit positions of Polar codes, the NR-PBCH decoding performance is improved when the known bits a priori can be exploited.