FTN OFDM/OQAM Pre-coding for Interference Cancellation
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Solution Overview
Problem
Faster-Than-Nyquist (FTN) transmission systems experience significant interference, particularly in multicarrier systems, which limits their ability to transmit data beyond the Nyquist rate without increasing transmission power, leading to reduced efficiency and increased errors.
Innovation Solution
The proposed method involves pre-coding symbols to partially cancel interference between symbols and carriers by modifying their values based on their position in the transmission pattern, allowing for reduced interference and increased data transmission rates beyond the Nyquist rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If FTN transmission is implemented to increase data transmission rate beyond Nyquist rate, then productivity is improved, but interference between symbols and carriers increases leading to reduced reliability
Solution Approach 1:
The patent applies preliminary action by performing pre-coding of symbols before transmission to anticipate and cancel interference. The pre-coding process modifies symbols based on predicted interference from adjacent symbols and carriers, so that when interference occurs during FTN transmission, the pre-cancelled interference patterns neutralize the harmful effects, maintaining reliability while enabling higher transmission rates
Solution Approach 2:
The patent implements preliminary anti-action by introducing pre-coded symbols that generate counter-interference patterns. The pre-coding process creates symbols with modified values that produce interference patterns opposite to the expected harmful interference, thereby canceling it out before it can degrade transmission accuracy during FTN operation
2Reliability
If transmission power is increased to reduce interference in FTN systems, then reliability is improved, but use of energy increases
Solution Approach 1:
The patent applies parameter changes by modifying the symbol values through pre-coding operations. Instead of increasing transmission power, the system changes the parameters of the transmitted symbols themselves, applying interference-canceling transformations that allow reliable transmission at lower power levels. This parameter modification approach substitutes for power increase while maintaining transmission accuracy
3Reliability
If pre-coding is applied to cancel interference, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the pre-coding process into distinct operational stages: interference prediction, pre-coding transformation, and transmission. This segmentation allows the complex pre-coding operation to be broken down into manageable processing steps, reducing overall system complexity while maintaining the interference cancellation functionality and transmission reliability
Data Source
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AI summary
The invention relates to precoding (or rather pre-equalisation) for a faster-than-Nyquist OFDM or OFDM/OQAM-type transmitter. Compression of faster-than-Nyquist OFDM pulses over time introduces an inter-symbol interference (ISI) and a sub-carrier interference (ICI). Assuming a Gaussian-type channel (AWGN), the ISI and ICI can be estimated at the transmitter and, in this way, some of the symbols (at most half) can be precoded (according to the value of the adjacent symbols), such as to cancel the ISI and ICI introduced during transmission and reception.