Distributed Iterative Decoding for Wireless Relay Systems
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Solution Overview
Problem
Current relay-based wireless communication systems face challenges in achieving efficient joint decoding for high data rates without increasing complexity, which can render the system impractical due to high implementation costs and computational expenses.
Innovation Solution
The method involves distributing iterative decoding between the destination and one or more relays, where the source transmits an LDPC encoded data block in the first time interval and additional parity in the second time interval, allowing the relay to partially decode and the destination to complete decoding using the received modified data and parity, thereby reducing processing load and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If joint decoding is performed at the destination to combine direct and indirect link signals, then co-operative diversity gain is achieved, but decoding complexity increases significantly
Solution Approach 1:
The patent segments the joint decoding process into two separate stages: first, the relay performs decoding on the indirect link signal independently; second, the destination performs decoding on the combined signal using the relay's decoded output. This segmentation reduces the overall decoding complexity while maintaining co-operative diversity gain, as each node only needs to perform partial decoding rather than full joint decoding of all signals simultaneously.
Solution Approach 2:
The relay performs preliminary decoding of the indirect link signal before the destination combines it with the direct link signal. This preliminary action simplifies the destination's decoding task, as it only needs to combine already-decoded relay signals with its own received signals, rather than performing complex joint decoding of all signals simultaneously.
2Productivity
If iterative decoding is performed with increased iterations to achieve high data rates, then decoding performance improves, but computational complexity and implementation cost increase
Solution Approach 1:
The patent applies partial action by performing iterative decoding at the relay for a limited number of iterations to achieve sufficient decoding performance, rather than performing the maximum number of iterations at the destination. This partial decoding at the relay, combined with the direct link signal at the destination, achieves high data rates while reducing overall computational complexity and implementation cost.
3Productivity
If relays are added to extend coverage and increase throughput, then network capacity improves, but system complexity and implementation cost increase
Solution Approach 1:
The relay node performs self-service by independently decoding the indirect link signal it receives from the source, rather than requiring the destination to perform all decoding operations. This self-service capability at the relay reduces the overall system complexity, as the relay handles its own decoding needs while still contributing to the co-operative diversity scheme, thereby enabling network extension and throughput increase without proportionally increasing system complexity.
Data Source
AI summary
A source sends an encoded data block during a first time interval to a destination and to a relay. The source sends additional parity bits for the encoded data block during a second time interval. The relay partially decodes that encoded data block to a process-defined end point (typically only a partial decoding), such as a fixed number of decoding iterations. After partial decoding the relay forms a modified data block having corrected information bits and the parity bits of the block it received, and sends the modified data block to the destination, during the second time interval. The destination decodes to a results-defined end point the modified data block it received from the relay using the additional parity bits it received from the source. If that end-point cannot be reached, the destination may begin anew decoding the original encoded data block it received from the source.