OFDM Video Transport for Long-Range Interference-Resistant Transmission
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Solution Overview
Problem
Electromagnetic pathways inherently degrade video signals due to attenuation, reflections, and impinging aggressor signals, leading to imperfect signal quality, especially in noisy environments and long-distance transmissions.
Innovation Solution
Implementing orthogonal frequency division multiplexing (OFDM) with improved encoding techniques to modulate and demodulate analog or digital samples, utilizing I and Q components for enhanced signal resilience and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If video signals are transmitted over electromagnetic pathways for long distances, then the transmission range is extended, but signal quality degrades due to attenuation, reflections, and interference
Solution Approach 1:
The video signal is divided into multiple subcarriers in the frequency domain through OFDM modulation. Each subcarrier carries a portion of the data and experiences independent fading characteristics, allowing the system to overcome frequency-selective fading and improve signal quality over long distances
Solution Approach 2:
The patent transforms the video signal from time domain to frequency domain using IFFT, modulates it onto multiple orthogonal subcarriers, and transmits it. At the receiver, FFT converts it back to time domain. This parameter transformation in the frequency domain enables better resistance to multipath interference and attenuation
2Reliability
If traditional modulation techniques are used to transmit video signals, then the system complexity is low, but information density and immunity to interference are insufficient
Solution Approach 1:
The patent transitions from single-carrier time-domain modulation to multi-carrier frequency-domain modulation. By utilizing the frequency dimension and creating orthogonal subcarriers, the system achieves better interference immunity while managing complexity through efficient IFFT/FFT processing
Solution Approach 2:
The patent introduces cyclic prefixes as intermediary elements between OFDM symbols. These cyclic prefixes act as guards against inter-symbol interference and simplify equalization at the receiver, improving reliability while maintaining manageable system complexity
3Reliability
If conventional transmission methods are used, then the implementation is simple, but channel equalization is complex and signal degradation occurs
Solution Approach 1:
Instead of equalizing the channel in the time domain as in conventional systems, the patent performs equalization in the frequency domain after FFT transformation. This inversion of the processing domain simplifies equalization to simple complex division operations on each subcarrier, reducing overall system complexity while improving signal quality
Data Source
AI summary
An orthogonal frequency division multiplexing (OFDM) transmitter maps a digital level into I and Q components. The transmitter uses every other digital level as an I or Q component or divides the MSBs and LSBs of a digital level into the I and Q components. An analog OFDM transmitter uses a pair of input analog levels as the I and Q components. An inverse FFT outputs a complex value and OFDM symbols are transmitted. An inverse FFT may also output a real value using complex conjugates. An optional encoder encodes digital or analog samples into L levels using N orthogonal codes before input into the OFDM transmitter. OFDM receivers receive the OFDM signal and output digital or analog samples. Video signals are input into a distributor that distributes analog or digital samples into vectors, each vector input into an OFDM transmitter that transmits to a corresponding receiver.