Precoding Mitigates Intersymbol Interference in Faster-Than-Nyquist Systems
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Solution Overview
Problem
Faster-than-Nyquist (FTN) signaling introduces Intersymbol Interference (ISI), making reliable symbol estimation challenging, and existing receiver structures like the Viterbi algorithm are computationally inefficient for practical applications due to their high complexity.
Innovation Solution
A communication system with a precoder and decoder that perform matrix operations to transform input symbols and sampled symbols, respectively, using a pulse filter and matched filter, to mitigate ISI without amplifying noise, allowing for efficient data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pulses are packed tighter in time to increase data rate (FTN signaling), then productivity increases, but intersymbol interference increases making symbol detection difficult
Solution Approach 1:
The patent applies pre-coding at the transmitter that performs preliminary interference cancellation by predicting and removing ISI effects before transmission. This preliminary action prepares the signal so that when it undergoes FTN packing, the interference is already mitigated, enabling both high data rates and reliable detection without requiring complex receiver processing.
2Reliability
If Viterbi algorithm is used for maximum likelihood estimation in FTN systems, then symbol detection accuracy improves, but device complexity increases exponentially
Solution Approach 1:
The patent extracts and removes the ISI component from the received signal through the pre-coding operation at the transmitter. By taking out the interference element beforehand, the receiver no longer needs to perform complex iterative ML estimation or Viterbi decoding, dramatically reducing computational complexity while maintaining detection accuracy.
Solution Approach 2:
The pre-coding operation acts as an intermediary that transforms the transmitted signal to preemptively account for ISI effects. This intermediary processing at the transmitter side eliminates the need for complex intermediary processing (like Viterbi algorithms) at the receiver, simplifying the overall system while maintaining reliability.
3Reliability
If matched filter is used at the receiver for FTN signaling, then a theoretical solution exists for minimum error estimation, but the problem becomes NP-hard and computationally infeasible
Solution Approach 1:
The pre-coding performs preliminary interference cancellation that transforms the NP-hard detection problem into a tractable one. By preliminarily removing ISI effects, the received signal structure is simplified such that standard detection methods become computationally feasible while still achieving minimum error estimation performance.
Data Source
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AI summary
The invention refers to faster than Nyquist communication system wherein a set of symbols is conveyed from a transmitter (21) to a receiver (23), wherein the transmitter (21) and the receiver (23) are coupled by means of a transmission channel (22), comprising a precoder (210) adapted for generating a set of precoded symbols from a set of input symbols by performing a matrix operation with a precoding matrix, a pulse filter (212) adapted for generating a transmission signal to be transmitted over the transmission channel (22) as a function of the precoded symbols, a receiving filter (230) adapted for generating a set of sampled symbols as a function of the transmission signal and noise added by the transmission channel, and a decoder (232) adapted for generating a set of decoded symbols as a function of the set of sampled symbols, wherein the elements of the precoding matrix are dependent on a property of the pulse filter (212), The invention further refers to a transmitter, a receiver and corresponding methods, and to a user equipment and a base station.