OFDM Symbol Mapping for Decoding Performance
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Solution Overview
Problem
In OFDM mobile communication systems, the power allocation for reference symbols (RS) reduces the available power for data transmission, leading to lower Signal to Noise Ratio (SNR) for data symbols in OFDM symbols containing RS, which affects decoding performance, especially for systematic bit streams.
Innovation Solution
A method and apparatus for mapping modulation symbols to Resource Elements (REs) such that systematic bit streams are preferentially arranged in REs without RS, and parity bit streams are arranged in REs with RS, optimizing power allocation and improving decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power is allocated to reference symbols for channel estimation, then channel estimation accuracy is improved, but available power for data transmission is reduced
Solution Approach 1:
The patent applies local quality by differentiating power allocation between different types of REs. REs containing RS are allocated different power levels compared to REs containing only data symbols. This allows optimized power distribution where RS-containing REs receive sufficient power for accurate channel estimation, while other REs maximize data transmission power, resolving the contradiction between measurement precision and energy usage.
2Device complexity
If systematic bit streams are transmitted in REs with reference symbols, then power allocation is simplified, but decoding performance deteriorates due to lower SNR
Solution Approach 1:
The patent implements local quality by assigning different mapping locations to systematic and parity bit streams based on RE type. Systematic bit streams are preferentially mapped to REs without RS which have higher available power and thus higher SNR, while parity bits are mapped to remaining REs including those with RS. This differentiated mapping improves decoding performance without significantly increasing power allocation complexity.
Solution Approach 2:
The patent introduces an intermediary mapping mechanism that acts as a mediator between the channel encoder output and the physical transmission medium. The mapping module separates systematic and parity bits and assigns them to different RE types based on power availability, serving as an intermediary that optimizes the transmission path for each bit stream component, thereby improving overall decoding performance.
3Measurement precision
If reference symbols are inserted in OFDM symbols for channel estimation, then channel state tracking is improved, but Signal to Noise Ratio for data symbols in those OFDM symbols is reduced
Solution Approach 1:
The patent applies local quality by creating distinct power allocation zones within OFDM symbols. REs containing RS are identified and allocated power specifically for channel estimation purposes, while REs containing only data symbols are allocated maximum power for data transmission. This results in higher SNR for data symbols in OFDM symbols that contain RS, as the power allocation is optimized for each RE's specific function.
Data Source
AI summary
A method for mapping wireless resources of reference symbols for channel state estimation and modulation symbols for user information transmission in a transmitter of an Orthogonal Frequency Division Multiplexing (OFDM) mobile communication system is disclosed. The mapping method includes channel-encoding and modulating a user information stream to be transmitted, and then generating a systematic symbol stream and a parity symbol stream; and preferentially arranging systematic modulation symbols in resource elements of a symbol including no reference symbol, and then arranging parity modulation symbols in remaining resource elements.