Adaptive HF Communication System Using Dynamic Channel Selection
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Solution Overview
Problem
HF communications face bandwidth limitations due to ionospheric and surface wave propagation instabilities, leading to low throughput rates, which are insufficient for applications like Internet and videophone services, and existing solutions either increase complexity or have theoretical limits in bit rate.
Innovation Solution
An adaptive communications method that dynamically selects a sub-band of non-contiguous frequency channels based on predicted ionospheric disturbances and quality scores, allowing simultaneous transmission on multiple channels to increase bandwidth without significantly increasing equipment complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bandwidth is increased by taking into account adjacent channels, then the useful bit rate is improved, but the complexity of the systems, transmitters and receivers is increased
Solution Approach 1:
The HF band is segmented into multiple narrow frequency channels (e.g., 3 kHz each) that can be independently selected and combined. The system divides the available spectrum into discrete channels and transmits data across multiple selected channels simultaneously, achieving bandwidth expansion without requiring a single complex broadband transmitter design.
Solution Approach 2:
The patent transitions from single-channel transmission to multi-channel parallel transmission, adding a temporal and spectral dimension to the communication system. By selecting and combining multiple non-contiguous channels across the HF band, the system effectively increases the dimensional space available for data transmission, achieving higher bit rates without proportionally increasing device complexity.
2Productivity
If the yield of the corrector coding is increased to improve spectral efficiency, then the useful bit rate is improved, but the range and probability of establishing the communication are reduced
Solution Approach 1:
The communication stream is segmented and transmitted across multiple frequency channels with independent fading characteristics. This segmentation allows the system to achieve diversity gain, where the probability that all channels simultaneously experience deep fades is significantly reduced, thereby maintaining reliability while improving overall throughput through parallel transmission.
Solution Approach 2:
The system dynamically changes transmission parameters including the selection of frequency channels, modulation schemes, and coding rates based on real-time channel conditions. By adapting these parameters, the system can maintain high spectral efficiency on good channels while ensuring minimum reliability thresholds are met across the diverse channel set, balancing bit rate and communication probability.
3Reliability
If automatic frequency search is carried out to combat HF propagation channel instabilities, then link reliability is improved, but the temporal evolution of medium availability cannot be finely and dynamically taken into account
Solution Approach 1:
The system implements continuous feedback mechanisms where channel quality is monitored in real-time across multiple frequency channels. Based on this feedback, the system dynamically adjusts which channels are active, modifies transmission power distribution, and adapts modulation and coding parameters to exploit favorable channel conditions while avoiding degraded paths, thereby achieving both reliability and dynamic adaptability.
Solution Approach 2:
The patent employs dynamic channel selection and resource allocation that continuously adapts to changing HF propagation conditions. Rather than static frequency assignment or periodic frequency search only, the system dynamically activates/deactivates channels, adjusts power levels, and modifies transmission parameters in real-time based on observed medium availability, enabling fine-grained adaptation to temporal evolution of the HF channel.
Data Source
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AI summary
The method involves determining a useful sub band (310) available for transmission in high frequency band based on criteria e.g. number of frequencies allocated to user based on a plan (301) of allocation of frequencies and physical availability of the sub band evaluated based on prediction of disturbances induced on signal by reflections from ionospheric layers. A set of frequency channels with identical width is selected (313) in the sub band based on the plan and connection quality of each channel. The channels of a signal respecting a high frequency wave are simultaneously transmitted. An independent claim is also included for a high frequency band communication system comprising a high frequency transmitter and a high frequency receiver.