Multi-tone Concatenated Spread Spectrum Jamming Resistance
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Solution Overview
Problem
Existing communications systems lack robustness against a wide range of jammers and interference, particularly in highly dimensional systems, as they often fail to effectively allocate capacity and tolerate interference across multiple axes such as time, frequency, and code space.
Innovation Solution
A multi-tone concatenated spread spectrum (MT-CSS) system that spreads input data in both frequency and time dimensions, using digital modulators, inner code spread spectrum modulators, interleavers, and inverse discrete Fourier Transform processors to generate and process a multi-tone concatenated spread spectrum signal, providing robustness against impulse and narrow/partial band jammers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional OFDM systems use a large number of tones to achieve high dimensionality in frequency, then jamming resistance in the presence of narrowband jammers is improved, but each tone can still be affected by impulse jammers and the system lacks robustness across multiple dimensions
Solution Approach 1:
The patent transitions from traditional single-frequency dimension OFDM to a multi-dimensional approach by incorporating time-domain spreading sequences. Each frequency tone is further spread across multiple time slots, creating a two-dimensional protection grid that simultaneously defends against both narrowband frequency jammers and impulse time jammers, thereby resolving the vulnerability to impulse jammers while maintaining frequency diversity benefits
Solution Approach 2:
The patent implements a nested structure where frequency-domain OFDM tones are nested within a time-domain spreading code structure. Each OFDM tone is modulated with a spreading sequence that time-spreads the signal across multiple periods. This nested arrangement creates multiple layers of protection: the outer frequency layer provides narrowband jamming resistance while the inner time layer provides impulse jamming resistance, achieving comprehensive multi-dimensional jamming immunity
2Reliability
If spread spectrum systems are used to improve robustness against interference, then jamming resistance is enhanced, but the system complexity increases due to multiple processing stages
Solution Approach 1:
The patent merges the OFDM modulation process with the spread spectrum modulation process into a unified concatenated structure. The frequency-domain OFDM symbols are combined with time-domain spreading sequences in a way that integrates both functions into a single modular system. This merging approach maintains the robustness benefits of both OFDM and spread spectrum while reducing overall system complexity through unified processing architecture
Solution Approach 2:
The patent segments the complex modulation process into distinct functional modules: an OFDM modulation stage that handles frequency-domain processing, and a spread spectrum modulation stage that handles time-domain spreading. This segmentation allows each module to be optimized independently and simplifies the overall system architecture by breaking down the complex concatenated operation into manageable, separable components
Data Source
AI summary
Apparatus and methods spread input symbols for transmission in multiple dimensions. When input symbols are spread over time, frequency, and code space, the resulting symbols exhibit good immunity to interference. In one embodiment, a system with a multi-tone outer code/modulation and a direct sequence spread spectrum (DSSS) inner code/modulation provides good communications performance characteristics and can be efficiently implemented.