Dynamic Modulation and Coding for HF Communication Channels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing broadband high-frequency communication systems using multiple channels face challenges in adapting to varying propagation conditions and channel losses due to the instability of the ionosphere and interference, leading to inefficiencies in bit rate and reliability.
Innovation Solution
A dynamic choice protocol for modulation and coding schemes is implemented, allowing each channel to have independent modulation and coding based on its quality, with a common error correcting code and interleaver, and an extended autobaud preamble to manage channel quality and redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single modulation and coding scheme is used across all channels, then system complexity is reduced and ease of operation is improved, but the ability to adapt to varying channel conditions deteriorates, leading to reduced productivity and reliability
Solution Approach 1:
The system segments the broadband channel into multiple narrowband channels (n channels), each experiencing different propagation conditions. This segmentation allows independent modulation and coding scheme selection for each channel while maintaining overall system manageability through shared coding resources.
Solution Approach 2:
The system dynamically selects modulation and coding schemes for each channel based on real-time channel quality assessment. The autobaud extension preamble enables dynamic adaptation by carrying information about the modulation used on each channel, allowing the system to respond to varying ionospheric conditions while maintaining operational simplicity through automated selection.
2Reliability
If the useful bit rate is reduced on all channels to handle strong fading on one channel, then reliability is improved, but productivity deteriorates due to underutilization of good channels
Solution Approach 1:
The system applies local quality adaptation by selecting different modulation and coding schemes tailored to each channel's specific propagation conditions. Channels with good quality can use higher-order modulations and higher bit rates, while channels experiencing fading use more robust schemes, optimizing the overall system throughput and reliability balance.
Solution Approach 2:
The system changes modulation and coding parameters independently for each channel based on assessed channel quality. The autobaud extension preamble carries information about the modulation used on each channel, enabling parameter adaptation without reducing the bit rate on channels that are experiencing good propagation conditions.
3Adaptability or versatility
If channels are processed separately with dedicated modems, then adaptability to individual channel conditions is improved, but device complexity increases and coding diversity is lost
Solution Approach 1:
The system merges the coding functions across multiple channels by using a common correcting code and interleaver for all n channels. This consolidation reduces device complexity compared to having dedicated modems for each channel, while still allowing independent modulation scheme selection for adaptability to individual channel conditions.
Solution Approach 2:
The correcting code and interleaver serve multiple channels simultaneously, providing universal error correction capabilities across all n channels. This multi-functional approach reduces the number of separate processing components needed while maintaining the ability to adapt modulation schemes to individual channel characteristics.
4Device complexity
If a common correcting code is used across all channels, then device complexity is reduced and coding diversity is achieved, but the ability to optimize error correction for specific channel conditions deteriorates
Solution Approach 1:
The system applies a common correcting code to all channels, providing sufficient error correction capability for the worst-case channel conditions. This partial optimization approach accepts that not all channels will be fully optimized, but ensures reliable operation across all channels while maintaining low system complexity and enabling coding diversity through the shared correction mechanism.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Method and system of communication in a wide band high frequency HF communication system comprising at least n communication channels, an interleaver common to the n channels, a means making it possible to determine the quality of communication of each of the n channels, characterized in that it comprises at least the following steps: a step where at least the following information is introduced into the structure of the frame of the data at the level of an autobaud: . an item of information about the modulation employed on each of the n channels chn, . an item of information about the interleaver considered, common to the n channels, . the corrector code FEC employed, common to the n channels, . the number of channels employed (n) as well as for each one its identifier idn making it possible to order them, a choice of the modulation on a channel n, a common operation of coding and interleaving on the n channels, the transmission of the information introduced in the shared autobaud.