Turbo Decoder Extrinsic Feedback Control for VoLTE Voice Quality
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Solution Overview
Problem
Conventional communication systems fail to effectively utilize redundancy and correlations in data transmission, leading to suboptimal voice quality and increased packet loss rates in VoLTE services, particularly in LTE communication systems.
Innovation Solution
Implementing joint source channel decoding (JSCD) with a turbo decoder that includes multiple MAP decoders and analysis logic, which iteratively refines 'soft' decision representations by combining extrinsic information and a-priori data to avoid premature convergence and enhance decoding accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional decoding techniques are used, then device complexity is reduced, but voice quality deteriorates and packet loss rate increases
Solution Approach 1:
The decoder is segmented into multiple specialized MAP decoders (first MAP decoder for channel bits, second MAP decoder for source bits) that work in parallel. Each decoder handles a specific aspect of the decoding process, allowing complex joint source-channel decoding to be divided into manageable segments that improve voice quality while maintaining reasonable device complexity through functional specialization.
Solution Approach 2:
The patent merges channel decoding and source decoding into a unified joint source-channel decoding framework. By combining extrinsic information from both channel decoding and source modeling, the system achieves superior voice quality and packet loss resistance compared to conventional separate decoding approaches, while the merged structure efficiently utilizes shared computational resources.
2Measurement precision
If iterative decoding with multiple MAP decoders is implemented, then decoding accuracy is improved, but computational power consumption increases
Solution Approach 1:
The iterative decoding process implements feedback loops where extrinsic information from the first MAP decoder is fed into the second MAP decoder, and vice versa. This feedback mechanism allows the system to progressively refine decoding accuracy through multiple iterations, achieving high measurement precision while the feedback structure enables efficient reuse of computational results across iterations.
Solution Approach 2:
The system performs partial iterations of the decoding process, using a predetermined number of iterations that balances decoding accuracy with power consumption. By not performing excessive iterations beyond what is necessary for acceptable voice quality, the system achieves sufficient decoding precision while constraining power usage within acceptable limits for mobile devices.
3Reliability
If joint source channel decoding is implemented, then packet loss resistance is improved, but device complexity increases
Solution Approach 1:
The joint source-channel decoder is segmented into distinct functional modules: a first MAP decoder for channel bit decoding, a second MAP decoder for source bit decoding, and analysis logic for combining extrinsic information. This segmentation allows the complex joint decoding functionality to be implemented through manageable, specialized components that improve packet loss resistance while keeping individual module complexities low.
Solution Approach 2:
The decoder structure implements multi-functionality where the same MAP decoder architecture serves dual purposes: the first MAP decoder processes channel bits while the second MAP decoder processes source bits. Both decoders use similar computational structures but apply different modeling assumptions, allowing the system to achieve joint source-channel decoding capabilities without proportionally increasing device complexity through repeated specialized hardware.
Data Source
AI summary
A turbo decoder is configured to perform iterative decoding of data bits of a data packet received via a source signal to converge on a “soft” decision representation for each data bit of the data packet. The turbo decoder includes both an interleaved decoder and a non-interleaved decoder that work collaboratively to refine and improve the “soft” decision of each of the originally-received data bits. The interleaved decoder and the non-interleaved decoder are injected with extrinsic information based on at least a-priori information of the source signal. The turbo decoder avoids positive feedback of the a-priori information regarding the source signal from one decoder to the other by subtracting out extrinsic information based on the a-priori information that is injected into a decoder from the “soft” decision(s) determined by the decoder.