Impact of spectrum sharing on the efficiency of Faster-Than-Nyquist signaling

Abstract

Capacity computations are presented for Faster-Than-Nyquist (FTN) signaling in the presence of interference from neighboring frequency bands. It is shown that Shannon's sinc pulses maximize the spectral efficiency for a multi-access channel, where spectral efficiency is defined as the sum rate in bits per second per Hertz. Comparisons using root raised cosine pulses show that the spectral efficiency decreases monotonically with the roll-off factor. At high signal-to-noise ratio, these pulses have an additive gap to capacity that increases monotonically with the roll-off factor.

The Evolution of Faster-Than-Nyquist Signaling

“…In [6], the information rate of binary FTN signaling was investigated; it was shown that when τ → 0, binary FTN signaling is capable of attaining an information rate close to the capacity of unprecoded FTN signaling C FTN derived in [5]. Furthermore, the information rate of unprecoded FTN signaling has been studied in a multi-user scenario [8][9][10]. In [10], FTN signaling was considered in a multi-user downlink scenario, where the different user's data symbols were broadcast by superimposing multiple different FTN signals.…”

“…Most of the studies of FTN signaling can be classified into four categories: information-theoretic analysis [5][6][7][8][9][10][11][12][13][14][15][16][17][18], reduced-complexity receiver , channel estimation (CE) issues [35,39,[41][42][43], and transmit preprocessing/precoding [13-15, 18, 21, 44-51]. In the informationtheoretic studies, the achievable performance gains of FTN signaling over Nyquist signaling were investigated in terms of several metrics, such as the minimum Euclidean distance (MED), the mutual information, the capacity and the bit error ratio (BER).…”

SVD-Precoded Faster-Than-Nyquist Signaling With Optimal and Truncated Power Allocation

“…This implies that the capacity of ( 27) has no performance gain over the classic Shannon capacity for Nyquist-criterionbased signaling in the AWGN channel. This holds true for the information-theoretic analysis in the previous studies [6], [8], [10], [14]. By contrast, when employing the RRC shaping filter, a capacity gain is achievable, owing to FTN signaling with the packing ratio of τ ≥ 1/(1 + β), as mentioned in [6].…”

“…In [36], the capacity of the SVD-precoded FTN signaling scheme, which does not rely on power allocation unlike our proposed scheme, was provided, although its detail derivation is absent in [36]. In this section, we reformulate the mutual information in [36] with the aid of the independent parallel substreams attainable by SVD-based precoding of (10).…”

“…The capacity advantages of FTN signaling over its Nyquist-criterion-based counterpart have been investigated in the context of spectrum-sharing systems [10], multiple-access channels [11], multiple-input multiple-output (MIMO) systems [12], and broadcasting systems [14]. Furthermore, one study [13] calculated the information rate of FTN signaling, precoded using the square root of an FTN-induced ISI matrix, and other studies [6], [7], [10]- [12], [14] considered unprecoded FTN signaling. The spectral efficiency of the multi-carrier FTN signaling scheme that packs information symbols both in the time and frequency domains was also analyzed [15], [16].…”