核心概念
Faster-than-Nyquist (FTN) signaling can increase the number of independent signaling dimensions compared to Nyquist rate signaling, leading to higher channel capacity and maximum channel coding rates in the finite blocklength regime.
要約
The key insights from the content are:
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FTN signaling can increase the number of independent signaling dimensions compared to Nyquist rate signaling by packing more data symbols within the same time and frequency. This is particularly beneficial in the finite blocklength (FBL) regime where the Nyquist sampling theorem is not optimal.
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There are two distinct operating regions of FTN signaling in the FBL regime:
a) When the time-acceleration factor τ is above a certain threshold τ0, FTN has both higher channel capacity and maximum channel coding rate (MCCR) than Nyquist rate signaling, especially when using non-sinc pulse shapes.
b) When τ is below τ0, the channel capacity remains fixed but the MCCR of FTN can continue to increase, thereby reducing the gap between capacity and MCCR. This benefit is present regardless of the pulse shape, including the ideal sinc pulse.
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FTN signaling can be used to either increase the MCCR for a fixed block error rate, or alternatively, reduce the block error rates for a fixed channel coding rate, compared to Nyquist signaling in the FBL regime.
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The author derives tight bounds on the MCCR of FTN signaling using finite blocklength information theory, and provides an asymptotic analysis to show the accuracy of the derived normal approximation.
統計
The time-bandwidth product (TBP) is defined as Ω = 2WTd, where W is the bandwidth and Td is the total time duration.
The channel capacity of FTN signaling is given by:
CFTN(τ) = (1/2) ∫_0^W log(1 + ρ|ŝ_folded(f)|^2/τ) df [bps/Hz]
where ρ is the SNR and ŝ_folded(f) is the folded spectrum of the modulating pulse.
引用
"A unique aspect of FTN signaling is that it can increase the blocklength by packing more data symbols within the same time and frequency to yield strictly higher number of independent signaling dimensions than that of Nyquist rate signaling."
"When τ > τ0, FTN has both higher channel capacity and MCCR than that of Nyquist rate signaling, when the utilized pulse shape is non-sinc. Since the issues associated with the ideal sinc pulse only get exacerbated when packets are short, the benefit of FTN becomes more significant in the FBL regime."
"When τ < τ0, the channel capacity is fixed but MCCR of FTN can continue to increase to a certain degree, thereby reducing the gap between the capacity and MCCR. This benefit is present regardless of the utilized pulse shape, including the ideal sinc-pulse, and is unique to the FBL regime."