Bit Position Assignment in CoMP Multi-Bit Symbols
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Solution Overview
Problem
In cellular wireless networks, CoMP UEs receiving identical bit groups from multiple base stations may experience unequal downlink channel conditions, leading to unequal effective channel conditions and potential errors in decoding, especially for certain bit positions in modulation symbols.
Innovation Solution
A method where each base station receives bit streams for multiple UEs, subdivides them into bit sub-stream groups, determines quality rankings of downlink channel conditions, and modulation encodes bit sub-stream groups into multi-bit symbols with bit positions ordered from least significant to most significant based on quality rankings, ensuring that UEs with worse channel conditions receive bits with higher bit-level protection and those with better conditions receive bits with lower protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If identical bit groups are transmitted to multiple CoMP UEs from multiple base stations, then spectral efficiency and resource utilization are improved, but unequal downlink channel conditions cause unequal effective channel conditions leading to decoding errors
Solution Approach 1:
The patent applies local quality by assigning different bit positions within modulation symbols to different UEs based on their individual channel conditions. Each UE receives bits at positions optimized for its specific channel quality, with UEs having worse channel conditions assigned to more robust bit positions with higher signal-to-noise ratios. This resolves the contradiction by maintaining identical modulation symbols for spectral efficiency while providing differentiated bit-level protection for reliability.
2Reliability
If bit position assignment is optimized for each UE's channel condition, then error tolerance is improved, but system complexity increases due to quality ranking and bit position mapping procedures
Solution Approach 1:
The patent implements preliminary action by pre-determining quality rankings of downlink channel conditions and establishing bit position mappings before actual data transmission. The base station performs quality ranking assessments and creates lookup tables that map UE identifiers to optimal bit positions in advance. This reduces real-time processing complexity while maintaining optimized bit position assignment for error tolerance.
3Productivity
If all UEs receive the same modulation symbols, then transmission efficiency is improved, but UEs with worse channel conditions experience higher error rates due to insufficient bit-level protection
Solution Approach 1:
The patent applies parameter changes by modifying the bit position parameter within modulation symbols based on UE-specific channel conditions. While the overall modulation scheme and symbol structure remain unchanged to maintain transmission efficiency, the assignment of specific bits to specific positions within symbols is dynamically adjusted according to channel quality rankings. This allows robust transmission for weak channel UEs without sacrificing the efficiency gains of unified modulation symbol transmission.
Data Source
AI summary
A method and system for bit-level protection in concurrent downlink coordinated multipoint transmission of bit groups to multiple user equipment devices (UEs) from multiple base stations. Multiple base stations each serving a respective UE and each having a separate bit stream to communicate to its respective served UE will define bit groups across the bit streams, such that each bit group includes at least one bit from each base station's bit stream. Each bit group will be transmitted as a multi-bit data symbol modulated onto a subcarrier frequency. Susceptibility to pairwise confusion between different data symbols due to misidentification of particular bits will be used to determine bit-level protection for various bit positions of the data symbols. Assignment of particular bits of each bit group to particular UEs will include consideration of bit-level protection, such that UEs with lower quality downlink properties will be assigned bits providing higher bit-level protection, and vice versa.