Bit-to-Symbol Mapping for Shaped QAM Power and Reliability
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Solution Overview
Problem
Existing wireless communication systems, particularly 5G NR, face challenges in optimizing signal encoding to reduce transmission power and improve reliability and efficiency, especially in scenarios involving quadrature amplitude modulation (QAM) transmissions.
Innovation Solution
Implement bit-level constellation shaping (BLCS) by performing bit-shaping operations on information bits, adding cyclic redundancy check (CRC) bits, and mapping these bits to symbols using block-code based shaping, along with FEC decoding and de-shaping operations to optimize power distribution and error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bit mapping is used for QAM transmission, then the transmission process is simple, but the average transmission power is high and reliability is reduced
Solution Approach 1:
The patent applies parameter changes by modifying the probability distribution of bits before mapping to constellation points. Specifically, it uses bit-level constellation shaping to transform uniformly distributed bits into shaped bits with non-uniform probability distribution, where certain bit patterns are mapped to more frequently used constellation points. This changes the statistical parameters of the transmitted signal, reducing average power while maintaining data rate and improving reliability through optimized power distribution across constellation points.
Solution Approach 2:
The patent implements local quality by applying different mapping rules to different bit positions and different constellation points. Instead of uniform mapping, it assigns different probabilities and power levels to different bit patterns and constellation point locations. This allows optimal power allocation at each local position in the constellation diagram, improving overall system reliability while reducing average transmission power through localized optimization.
2Reliability
If bit-level constellation shaping is implemented, then average transmission power is reduced and reliability is improved, but the encoding complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the bit stream into separate groups that are processed independently through different shaping and mapping functions. It segments bits into information bits, parity bits, and shaped bits, each undergoing specific transformations before being mapped to constellation points. This modular segmentation reduces overall encoding complexity by breaking down the complex shaping operation into manageable, independent processing stages.
Solution Approach 2:
The patent implements preliminary action by pre-defining and storing mapping tables that associate shaped bit patterns with constellation points. Instead of performing complex real-time calculations during transmission, the system pre-computes optimal mappings and stores them in lookup tables. This preliminary preparation significantly reduces runtime encoding complexity while maintaining the reliability and power efficiency benefits of bit-level constellation shaping.
Data Source
AI summary
The apparatus may be configured to process input information including a set of information bits for a quadrature amplitude modulated (QAM) transmission by performing a bit-shaping operation for the set of information bits to generate a set of shaped bits and adding cyclic redundancy check (CRC) bits before forward error correction (FEC) on a combination of the set of information bits and the CRC bits. The apparatus may further be configured to transmit the QAM transmission. The apparatus may be configured to receive a QAM transmission; perform a FEC decoding on the QAM transmission; obtain CRC bits from the QAM transmission after the FEC decoding; and perform a bit level de-shaping operation on a set of shaped bits to obtain a set of information bits.