Programmable Reduced-State Trellis Decoder for Lower FEC Complexity
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Solution Overview
Problem
Current communication systems face challenges with high computational complexity in Forward Error Correction (FEC) schemes, particularly at higher modem data rates, and lack programmable decoders capable of reduced-state sequence estimation for trellis-coded modulation and continuous phase modulation, which are essential for efficient error correction in noisy channels.
Innovation Solution
A programmable decoder with reduced-state trellis structure parameters is developed, supporting demodulation of waveforms with memory and FEC codes, utilizing Ungerboeck set-partitioning and Svensson-style structures, implemented in a field programmable gate array (FPGA) to reduce computational complexity and improve error correction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard Viterbi decoding with full-state trellis is used, then error correction performance is maintained, but computational complexity becomes prohibitive at higher data rates
Solution Approach 1:
The patent applies segmentation by dividing the full-state trellis into multiple reduced-state trellises. Each reduced-state trellis handles a subset of the original states, allowing parallel processing that reduces the computational burden on individual processing units while maintaining overall decoding performance through coordinated operation of multiple segments.
Solution Approach 2:
The patent implements dynamics by making the trellis structure programmable and adaptable. The decoder can dynamically configure the number of states, trellis depth, and other parameters based on channel conditions and performance requirements, allowing the system to optimize between complexity and performance in real-time rather than being fixed to a single trellis configuration.
2Reliability
If FEC codes approach the theoretical Shannon limit, then error correction capability is improved, but the decoder fails when signal is below the minimum signal-to-noise ratio
Solution Approach 1:
The programmable trellis decoder can dynamically adjust its operation based on signal quality. When the signal-to-noise ratio is below the minimum threshold, the decoder can modify its decoding strategy, such as adjusting the effective trellis depth or state transitions, to maintain adaptability across a wider range of signal conditions rather than failing completely.
Solution Approach 2:
The patent changes parameters by allowing dynamic modification of trellis characteristics including the number of states, constraint length, and other decoding parameters. This enables the system to adapt to varying signal conditions by adjusting these parameters in response to measured signal quality, thereby extending operational range below the traditional minimum signal-to-noise ratio threshold.
3Ease of manufacture
If a fixed-state trellis decoder is implemented, then hardware design is simplified, but the decoder cannot support multiple waveform types and FEC codes
Solution Approach 1:
The patent achieves universality by designing a programmable trellis decoder that can support multiple waveform types (such as CPM, TCM) and various FEC codes through configuration rather than requiring separate dedicated hardware for each. The same physical hardware structure can be reconfigured via programming to handle different communication standards and protocols, providing multi-functionality without increasing physical complexity.
4Device complexity
If reduced-state trellis is used, then computational complexity is reduced, but demodulation accuracy for waveforms with memory deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the reduced-state decoding into multiple stages or segments that process different aspects of the signal. This allows the system to maintain reduced computational complexity at each stage while collectively achieving accurate demodulation of waveforms with memory through the coordinated action of multiple segmentation layers.
Solution Approach 2:
The programmable nature of the reduced-state trellis decoder allows dynamic adjustment of the reduction level based on the specific waveform characteristics. For waveforms with memory, the system can dynamically increase the effective state tracking capability while still maintaining overall reduced complexity compared to full-state decoding, thereby preserving demodulation accuracy.
Data Source
AI summary
A programmable decoder includes at least one programming input for a plurality of programmable, reduced state trellis parameters. A programmable device is connected to the at least one programming input and implements a Reduced-State Sequence Estimation (RSSE) decoder comprising at least one reduced-state trellis structure based upon the plurality of programmable reduced-state trellis parameters, including one of at least the number of super-states, the number of full-states, the number of branches per super-state, a reverse super-state trellis table, a decoder super-state survivor as a full-state, a forward full-state table, a full-state to super-state mapping table, a decoder super-state path metric and decoder super-state traceback array.