OFDM Sub-channel Selection for Interference Avoidance
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Solution Overview
Problem
In countries without organized frequency spectrum allocation systems, establishing reliable wireless communications is challenging due to unmanaged frequency congestion and interference, especially in conflict zones where military or government communications are vulnerable to jamming.
Innovation Solution
The system identifies available frequency spectrum by selecting an initial center frequency and generating orthogonal frequency division multiplexed (OFDM) sub-channels, allowing for adaptive modulation schemes and power levels based on channel quality, and implements frequency hopping to mitigate interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If frequency spectrum is used for wireless communications in countries without organized allocation systems, then communications can be established, but frequency congestion and interference occur
Solution Approach 1:
The patent divides the frequency spectrum into multiple sub-channels within an OFDM structure. Instead of using a single frequency band, the system segments the spectrum into numerous smaller sub-channels that can be individually selected and combined, allowing the transmitter to avoid congested frequencies while maintaining communication capability
Solution Approach 2:
The system dynamically selects which sub-channels to use based on real-time channel quality indicators (CQI) and interference conditions. The set of available sub-channels is not fixed but changes adaptively according to environmental conditions, enabling the system to optimize performance and avoid interference continuously
2Ease of operation
If military or government communication systems use fixed frequency bands, then communications can be established, but they become vulnerable to jamming
Solution Approach 1:
The communication system employs dynamic frequency selection where the set of active sub-channels changes over time based on channel conditions and interference detection. This dynamic behavior makes it difficult for adversaries to jam the communication effectively, as the frequencies being used are not predictable or fixed
Solution Approach 2:
The system changes multiple parameters simultaneously including frequency selection (which sub-channels are active), modulation schemes (QPSK, 16-QAM, 64-QAM), and power levels based on channel quality. This multi-parameter adaptation provides resilience against jamming by allowing the system to switch to alternative configurations when interference is detected
3Reliability
If high power levels are used to transmit data, then data transmission reliability is improved, but energy consumption increases
Solution Approach 1:
The system adaptively adjusts transmit power levels based on channel quality indicators for each sub-channel. When channel conditions are good, lower power levels are sufficient; when conditions deteriorate, power is increased only for affected sub-channels. This selective parameter adjustment maintains reliability while minimizing overall energy consumption
Solution Approach 2:
By segmenting the frequency spectrum into sub-channels, the system can apply different power levels to different sub-channels based on their individual quality. This allows concentrated power allocation only where needed rather than uniformly high power across all frequencies, reducing total energy consumption while maintaining transmission reliability
4Productivity
If contiguous frequency bands are used for transmission, then spectrum efficiency is improved, but susceptibility to interference increases
Solution Approach 1:
The system segments the frequency spectrum into many narrow sub-channels rather than using wide contiguous bands. This segmentation allows selective combination of non-contiguous sub-channels that are free from interference, achieving spectrum efficiency through careful selection while avoiding interference by excluding contaminated frequencies
Solution Approach 2:
Each sub-channel is evaluated individually for its local quality (channel conditions, interference level, CQI). The system selects and combines only those sub-channels with acceptable local quality, allowing non-contiguous frequency selections that optimize both spectrum efficiency and interference avoidance based on local channel characteristics
Data Source
AI summary
Information is transmitted over selected, Orthogonal Frequency Division Multiplexed (OFDM) sub-channels to avoid frequencies with unacceptable congestion, noise or interference levels. Using frequency hopping, selected non-contiguous OFDM sub-channels used for transmission may vary with time. Once a group of OFDM sub-channels is selected, a power level and modulation technique may also be selected based on channel quality.