Partial Decoding for Interference Cancellation in Multi-User Receivers
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Solution Overview
Problem
Multi-user receivers face significant delays in interference cancellation due to the need to wait for complete codeword reception, which is unacceptable for time-sensitive applications like voice communication, and is complicated by varying signal lengths and uncoordinated transmissions from multiple users.
Innovation Solution
The method involves partial decoding of codewords by treating unavailable coded bits as erasures or punctured bits, allowing for interference cancellation without waiting for full codeword reception, using techniques like setting soft values to zero for unavailable bits and reconstructing signals to reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the receiver waits for complete codeword reception before performing interference cancellation, then the accuracy of interference cancellation is improved, but the processing delay increases
Solution Approach 1:
The receiver performs preliminary interference cancellation using the portion of the codeword that has been received so far, before the complete codeword is available. This allows the second signal to benefit from interference cancellation earlier, reducing processing delay while maintaining reasonable accuracy.
Solution Approach 2:
Instead of waiting for the complete codeword, the receiver performs interference cancellation using only the partial codeword that is available at the current time. This partial action enables earlier processing of the second signal, trading some cancellation accuracy for reduced delay.
2Productivity
If the receiver processes signals in parallel without coordination, then the processing speed is improved, but the interference cancellation performance deteriorates
Solution Approach 1:
The receiver performs preliminary decoding and signal reconstruction for the first signal as soon as enough samples are available, even before the complete codeword is received. This preliminary action enables earlier interference cancellation for the second signal, improving processing speed while maintaining coordination between signals.
3Loss of information
If the receiver waits for all samples in the codeword span to be received, then the completeness of signal decoding is improved, but the delay for subsequent signal processing increases
Solution Approach 1:
The receiver performs preliminary decoding using the portion of the codeword that has been received so far, reconstructing the signal for interference cancellation purposes before all samples are available. This reduces the waiting time for subsequent signal processing while accepting that the decoding is based on incomplete information.
Solution Approach 2:
The receiver performs partial decoding using only the available samples within the current processing time, rather than waiting for all samples in the complete codeword span. This partial decoding enables earlier interference cancellation, reducing delay for subsequent signals.
Data Source
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AI summary
The delay associated with performing interference cancellation in a multi-user receiver is reduced by enabling partial decoding. According to an embodiment, interference is canceled from a received signal having signal contributions from multiple users by partially decoding a first codeword obtained from the received signal and transmitted by a first user via a first signal. The first signal is reconstructed based on the partial decoding of the first codeword and canceled from the received signal to yield a reduced-interference signal. A second codeword obtained from the reduced-interference signal and transmitted by the first user or a second user via a second signal is at least partially decoded. In one embodiment, the first codeword is partially decoded by puncturing one or more coded bits of the first codeword and decoding the first codeword based on the one or more punctured coded bits and estimates of the remaining coded bits. It is determined whether reconstruction and cancellation of the first signal is beneficial for the at least partial decoding of the second signal based on one or more signal quality metrics.