BICM-ID Receiver Candidate Narrowing for Lower MIMO Demodulation Load
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Solution Overview
Problem
In wireless communication systems using BICM-ID, the large modulation multilevel number leads to an exponential increase in received signal point candidates, resulting in a huge calculation amount for the MIMO demodulator, especially when iterative decoding is performed, which deteriorates decoding characteristics and increases processing complexity.
Innovation Solution
A receiver configuration that includes a demodulator, deinterleaver, decoder, and interleaver, with a received signal point candidate generator and narrowing-down unit, which uses a priori information and signal point candidate distances to reduce the number of candidates for likelihood calculation, thereby reducing the calculation amount and maintaining decoding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the modulation multilevel number is increased to improve communication efficiency, then the data transmission rate is improved, but the number of received signal point candidates increases exponentially, resulting in a huge calculation amount for the MIMO demodulator
Solution Approach 1:
The patent segments the received signal point candidates into multiple groups based on their metric values (distance from received signal). Instead of processing all candidates uniformly, the demodulator divides them into first candidates (with smaller metrics) and second candidates (with larger metrics), processing them differently to reduce overall calculation complexity while maintaining decoding accuracy.
Solution Approach 2:
The patent changes the processing parameters based on the iteration count in iterative decoding. When the iteration count is below a threshold, both first and second candidates are processed. When the iteration count reaches or exceeds the threshold, only first candidates are processed. This dynamic parameter change reduces calculation amount in later iterations while maintaining performance.
2Reliability
If iterative decoding processing is performed to improve decoding characteristics, then the decoding performance is improved, but the calculation amount of the MIMO demodulator increases due to repeated processing
Solution Approach 1:
The patent makes the processing dynamic by adapting to the iteration count. The demodulator dynamically adjusts which candidates to process based on whether the current iteration is below or at/above a threshold. This dynamic adaptation allows the system to maintain high decoding performance in early iterations while reducing calculation burden in later iterations when a priori information is already strong.
Solution Approach 2:
The patent changes the processing parameter (number of candidates processed) based on the iteration count. In early iterations (count < threshold), all candidates are processed to ensure accurate extrinsic information generation. In later iterations (count ≥ threshold), only the most promising first candidates are processed, reducing calculation amount while maintaining decoding performance.
3Measurement precision
If all received signal point candidates are used for likelihood calculation to maintain demodulation accuracy, then the demodulation characteristics are maintained, but the processing time and calculation amount become huge
Solution Approach 1:
The patent segments candidates into first candidates (smaller metric values, closer to received signal) and second candidates (larger metric values, farther from received signal). By processing first candidates in all iterations and conditionally processing second candidates only in early iterations, the patent maintains demodulation accuracy while significantly reducing processing time in later iterations.
Solution Approach 2:
The patent applies partial action by processing only a subset of candidates (first candidates) in later iterations when the iteration count reaches or exceeds the threshold. This partial processing is sufficient to maintain demodulation accuracy because a priori information from previous iterations already provides strong guidance, eliminating the need to process all candidates.
Data Source
AI summary
Provided is a BICM-ID technique which suppresses deterioration of decoding characteristics and reduces a calculation amount. A receiver includes a demodulator, deinterleaver, decoder, and interleaver. The demodulator outputs first extrinsic information by using a received signal encoded and interleaved and a priori information. The deinterleaver processes the first extrinsic information and outputs second extrinsic information. The decoder outputs third extrinsic information by using the second extrinsic information. The interleaver processes the third extrinsic information and outputs fourth extrinsic information. In the receiver that performs iterative decoding processing using the fourth extrinsic information as the a priori information, the demodulator includes a generator, a received signal point candidate narrowing-down unit, and a likelihood calculation unit. The generator generates a plurality of received signal point candidates. The likelihood calculation unit creates the first extrinsic information based on the narrowed-down received signal point candidates, the a priori information, and the received signal.