SC-FDMA Multiple Codeword Transmission with SIC
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Solution Overview
Problem
The SC-FDMA system experiences high peak to average power ratio (PAPR) and interference between transmission symbols in frequency selective fading environments, limiting its performance.
Innovation Solution
The method involves dividing user data into multiple sub-streams, performing independent channel coding and QAM mapping, mapping signals to DFT indices, and transmitting multiple codewords using DFT and IFFT, while receiving signals through FFT and subcarrier demapping, with successive interference cancellation to reduce interference and adjust transmission power based on channel state information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If SC-FDMA system transmits only one stream, then PAPR is reduced, but interference between symbols occurs in frequency selective fading environment
Solution Approach 1:
The transmitted signal is segmented into multiple codewords (first codeword and second codeword), each carrying portions of the data stream. This segmentation allows the system to maintain the single-carrier low-PAPR advantage while using multiple coded streams to combat symbol interference through diversity and interference cancellation techniques
Solution Approach 2:
The receiver discards the interference component by successively canceling out decoded codewords from the received signal. After decoding the first codeword, the receiver reconstructs and subtracts it from the received signal, then decodes the second codeword from the residual signal, effectively recovering the original data without symbol interference
2Reliability
If multiple codewords are transmitted, then interference between symbols is reduced, but system complexity increases
Solution Approach 1:
The data stream is divided into multiple codewords with distinct coding rates and modulation schemes, allowing independent processing and optimization of each codeword while maintaining overall system performance through diversity
Solution Approach 2:
The receiver provides feedback about channel conditions and decoding results to the transmitter, enabling adaptive modulation and coding adjustments. This feedback mechanism allows the system to optimize the number and characteristics of codewords based on current channel quality, managing complexity dynamically
3Reliability
If different coding rates are used for multiple codewords, then performance in frequency selective fading is improved, but processing complexity increases
Solution Approach 1:
Different coding rates and modulation schemes are assigned to different codewords based on their specific channel conditions and importance. This local optimization allows critical data to use more robust coding while less critical data uses higher-rate coding, improving overall reliability without uniformly increasing complexity
Solution Approach 2:
The channel coding process is segmented into independent coding operations for each codeword, allowing parallel processing and independent optimization of coding parameters for each stream based on channel conditions
Data Source
AI summary
The present invention relates a method and apparatus for transmitting/receiving data using multiple codewords in a communication system using SC-FDMA (single carrier frequency division multiple access). A transmitter generates the multiple codewords for user data and transmits the generated multiple codewords. A receiver receives the multiple codewords and sequentially performs decoding and SIC (successive interference cancellation) on the received multiple codewords. Therefore, this structure can minimize a PAPR (peak to average power ratio) and considerably reduces interference between symbols in a frequency selective fading environment.