This article presents the architecture and operations of ARENA-PAC, a globally geo-distributed high-bandwidth research and education network. We highlight the experiments on ARENA-PAC and present a site-dedicated prefix design that keeps each PoP independently reachable, and describe an anycast-based resilient service and measurement research as two applications built on this design.

In this paper, we propose a closed-form, near-optimal signal detection (SD) scheme for underwater acoustic wireless (UAW) communication affected by non-Gaussian impulsive noise. First, we introduce an optimal SD scheme based on a Neyman-Pearson criterion-driven likelihood-ratio test (LRT), which directly employs a noise probability density function (PDF) calculated from measured UAW noise. We demonstrate that this optimal SD scheme significantly outperforms the conventional linear correlator (LC)-based SD scheme designed for Gaussian-noise channels, in terms of detection error rate (DER) performance. To address the prolonged noise observation time required for direct PDF calculation, we then propose an SD scheme that approximates the noise PDF using the Student ’s t-distribution (StD). The StD-aided PDF approximation yields a closed-form LRT expression and enables low-complexity statistical parameter estimation, in contrast to the conventional α- stable distribution-based schemes. Simulation results based on a variety of noise datasets reveal that the proposed StD-based SD scheme achieves DER performance close to that of the optimal SD scheme, while maintaining substantially lower computational complexity and shorter noise observation times.

In this paper, we propose a novel precoded non-orthogonal frequency division multiplexing (NOFDM) with subcarrier index modulation (SIM) to increase spectral efficiency for multicarrier systems. The proposed NOFDM-SIM scheme is constituted by a filterbank multicarrier system under reduced subcarrier spacing, where precoded index modulated symbols are mapped onto the subcarriers. The detrimental effects of inter-carrier interference (ICI) resulting from the non-orthogonality between subcarriers are efficiently mitigated with the aid of eigenvalue-decomposition-based precoding. Our simulation results demonstrate that the proposed precoded NOFDM-SIM system exhibits a similar peak-to-average power ratio to OFDM and OFDM-SIM counterparts while achieving the bit error rate limit of zero-ICI OFDM in a channel-uncoded setting. We analyze the power spectral density of the proposed scheme to demonstrate that the proposed scheme is strictly bandlimited, unlike its orthogonal counterpart. Furthermore, we present detailed investigations of the effects on ICI in the proposed scheme with and without precoding as well as power allocation. Finally, we introduce a three-stage iterative decoding architecture for our proposed scheme and show near-capacity error performance.

In this paper, we propose novel reduced-complexity fast Fourier transform (FFT)-spread faster-than-Nyquist (FTN) signaling with optimal power allocation for a frequency-selective fading channel. The information rate of the proposed FTN signaling is approximately derived by relying on the circulant approximation of the FTN-specific intersymbol interference matrix and noise covariance matrix. This allows us to constitute efficient calculations of precoding and weighting matrices. The power allocation coefficients are optimized such that the approximated information rate is maximized. Our simulation results demonstrate that the proposed scheme achieves the bit error ratio performance close to the conventional eigenvalue-decomposition (EVD)-precoded FTN signaling counterpart that is optimal in terms of an achievable information rate while significantly reducing the computational complexity as low as the order of ${\mathcal{O}}(N\log N)$.

In this paper, we propose a novel precoded non-orthogonal frequency division multiplexing (NOFDM) with sub-carrier index modulation (SIM) to increase spectral efficiency for multicarrier systems. The proposed NOFDM-SIM scheme is constituted by a filterbank multicarrier system under reduced subcarrier spacing, where precoded index modulated symbols are mapped onto the subcarriers. The detrimental effects of inter-carrier interference (ICI) resulting from the non-orthogonality between subcarriers are efficiently mitigated with the aid of eigenvalue-decomposition-based precoding. Our simulation results demonstrate that the proposed precoded NOFDM-SIM system exhibits a similar peak-to-average power ratio to OFDM and OFDM-SIM counterparts while achieving the bit error ratio limit of zero-ICI OFDM.

In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index-modulated symbol transmission. More precisely, eigenvalue decomposition (EVD) precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain index modulation (IM). While the FTN scheme increases the spectral efficiency and data rate by increasing the density of transmit symbols, the time-domain IM works towards the same objective while maintaining symbol sparsity. We analytically derive the constrained capacity of the proposed system. Our simulation results show that the proposed scheme has better bit error ratio (BER) performance than the conventional FTN-IM scheme, particularly for the scenario of a higher packing ratio. With the proposed scheme, a 2.5 dB performance gain is observed at the BER of 10−4, where the packing ratio is 0.7 and the roll-off factor is 0.5 in the channel-uncoded scenario. We further analyze our scheme’s performance by characterizing its minimum Euclidean distance and inter-symbol interference. Furthermore, we present a three-stage serially concatenated iterative detection architecture for the proposed EVD-FTN-IM signaling scheme. It is demonstrated in our simulations that a near-capacity BER performance is achievable in the proposed turbo-coded FTN-IM scheme.

In this paper, we propose eigenvalue decomposition (EVD)-precoded faster-than-Nyquist (FTN) signaling with power allocation in a frequency-selective fading channel. More specifically, we derive the mutual information associated with the proposed FTN signaling. Then, the optimal power coefficients are calculated such that the derived mutual information is maximized. Our analytical performance results show that the proposed FTN signaling scheme achieves a higher information rate than the conventional FTN signaling scheme without relying on power allocation and the classic Nyquist signaling scheme, under the assumption that all the schemes employ a root-raised cosine shaping filter. Moreover, we derive the proposed scheme’s achievable information rate in the presence of channel estimation errors. Furthermore, our numerical simulation results for the bit error ratio performance and the power spectral density demonstrate that the proposed FTN scheme outperforms the conventional Nyquist signaling scheme without incurring any bandwidth broadening.

In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index modulated (IM) symbol transmission. More precisely, eigenvalue decomposition precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain IM. While the FTN scheme increases the spectral efficiency and data rate by packing more transmit symbols per block duration than those defined in the Nyquist criterion, time-domain IM works towards the same objective while maintaining symbol sparsity. We analytically derive the constrained capacity of the proposed system. Our simulation results show that the proposed scheme has better bit error ratio (BER) performance over the conventional FTN-IM scheme, particularly for the scenario of a higher packing ratio. In the proposed scheme, 2.5-dB performance gain is observed at the BER of = 10−4, employing the packing ratio of 0.7 and the roll-off factor of 0.5 in a channel-uncoded scenario.

In this paper, we investigate the achievable performance of precoded faster-than-Nyquist (FTN) signaling with truncated power allocation from the information-theoretic perspective. More specifically, the effects of the eigenvalue distribution of the FTN-specific inter-symbol interference (ISI) matrix on the information rate were investigated. In order to evaluate the effects of significantly low eigenvalues, 1024-bit eigendecomposition calculations, which is significantly accurate in comparison to the calculations in the standard double-precision environment, are carried out. It is demonstrated that there is a novel performance tradeoff between the information rate versus the calculation precision of a transmit signal in the precoded FTN signaling scheme with truncated power allocation.

This paper proposes a novel ultra-dense non-orthogonal frequency-division multiplexing (NOFDM) transmission, where subcarrier spacing is set significantly lower than that of OFDM. Eigenvalue-decomposition-aided precoding is conceived for eliminating the detrimental effects of NOFDM-specific inter-carrier interference and correlated noises. The classic capacity formula is extended to that supporting our precoded NOFDM scheme. Optimal power allocation (PA) is developed for maximizing the derived capacity of the proposed scheme. In analytical and numerical results, we demonstrate that the proposed NOFDM scheme with optimal PA outperforms the conventional NOFDM and the classic OFDM schemes.

This paper proposes a novel ultra-dense non-orthogonal frequency-division multiplexing (NOFDM) transmission, where subcarrier spacing is set significantly lower than that of orthogonal frequency-division multiplexing (OFDM). In order to eliminate the detrimental effects of NOFDM-specific inter-carrier interference and correlated additive noises, eigenvalue-decomposition-aided precoding is conceived. The classical capacity formula is extended to one supporting our precoded NOFDM scheme. Optimal power allocation (PA) is developed in order to maximize the derived capacity of the proposed scheme. Furthermore, truncated PA is developed to combat the limitations due to significantly low eigenvalues, which are specifically imposed by the proposed ultra-dense NOFDM. Through analytical and numerical results, we demonstrate that the proposed NOFDM schemes with optimal and truncated PA outperform the conventional NOFDM and the classical OFDM schemes.

This paper proposes a precoded faster-than-Nyquist (FTN) signaling scheme based on singular-value decomposition (SVD) with optimal power allocation. An information-theoretic analysis is conducted on the proposed SVD-precoded FTN signaling architecture. Analytical performance results demonstrate that the proposed optimal scheme outperforms its conventional Nyquist-criterion- based counterpart and the conventional SVD-precoded FTN signaling scheme, which does not use power allocation. In order to overcome the limitations associated with significantly low singular values, suboptimal truncated power allocation is incorporated.

This letter proposes a differentially modulated non-orthogonal spectrally efficient frequency-division multiplexing (D-SEFDM) architecture, which allows us to dispense with any pilot overhead needed for channel estimation at the receiver, while increasing the bandwidth efficiency in comparison to the orthogonal frequency-division multiplexing counterpart. While it is a challenging task to carry out differential-modulation-assisted non-coherent detection for multi-carrier transmissions in the presence of a severe inter-carrier interference (ICI), in the proposed scheme ICI elimination and symbol demodulation are implemented in a non-coherent manner, by exploiting the fact that ICI imposed by D-SEFDM is deterministically given, once we have a compression factor of non-orthogonal subcarriers. It is verified in our simulations that the proposed D-SEFDM exhibits a higher performance than the conventional coherent SEFDM scheme, especially for the scenarios of a high Doppler frequency.

In this letter, motivated by the recent differential faster-than-Nyquist (DFTN) signaling concept, we propose an improved 16-point double-ring star quadrature amplitude modulation (QAM)-aided DFTN signaling transmission, which allows us to attain a higher bandwidth efficiency as well as a simple receiver based on noncoherent detection. We derive an analytical error-rate bound for the proposed star-QAM DFTN signaling in an uncoded scenario. The derived bound is used for optimizing the star-QAM constellation for our DFTN signaling in terms of error-rate performance in an uncoded scenario. Our simulation results demonstrate that the proposed star-QAM DFTN scheme outperforms its conventional phase-shift-keying-based DFTN counterpart.

This study proposes a precoded faster-than-Nyquist (FTN) signaling scheme based on singular-value decomposition (SVD) with optimal power allocation. An information-theoretic analysis is conducted on the conventional and proposed SVD-precoded FTN signaling architectures. The associated information rate bound is derived in a closed-form by extending the classic Shannon capacity to support the SVD-precoded FTN signaling schemes. Our analytical performance results demonstrate that the proposed scheme outperforms its conventional Nyquist-criterion-based counterpart and the conventional SVD-precoded FTN signaling scheme, which does not use power allocation. Several important implementation issues, such as inter-block interference, the use of a frequency-selective (dispersive) channel, truncation, and sampling rate, are also considered. Finally, a suboptimal power allocation scheme that overcomes the truncation issue is presented.

In this paper, we propose a novel differential faster-than-Nyquist (DFTN) signaling scheme, which allows us to dispense with any channel estimation at the receiver while benefiting from the rate boost of faster-than-Nyquist (FTN) signaling. At the transmitter, differentially modulated binary phase-shift keying (DBPSK) symbols are transmitted with the symbol interval that is smaller than that defined by the Nyquist criterion. The receiver noncoherently estimates the DBPSK symbols, suffering from the effects of FTN-specific inter-symbol interference (ISI), based on frequency-domain equalization. This is enabled, because FTN-specific lSI is deterministic, by assuming that the FTN's symbol packing ratio and the roll-off factor of a shaping filter are known in advance at the receiver.

In this paper, we propose semi-blind iterative frequency domain joint channel estimation (CE) and data detection (DD) of faster-than-Nyquist signaling (FTNS). The proposed scheme achieves low-complexity operation, while maintaining a performance close to that of the perfect channel state information scenario. More specifically, we derive low-complexity frequency-domain CE for the faster-than-Nyquist pilot (FTNP) transmission scenario, where the symbol duration of a pilot block is lower than the Nyquist-criterion-based pilot transmission. Moreover, we propose a serially concatenated channel-encoded FTNS transceiver that takes into account FTNS-specific colored noise effects. The proposed low-complexity receiver carries out soft-decision frequency-domain equalization with the aid of the minimum-mean square error criterion while whitening the colored noise. As explicit benefits of the proposed frequency-domain CE for the FTNP, the demodulated FTNS data block can also be used as a long pilot block, so the iterative joint CE and DD becomes realistic. Simulation results demonstrate that the proposed two-stage-concatenated FTNS system relying on binary phase-shift keying-based FTNP and FTNS-data symbols achieves a better error-ratio performance than previous systems that do not consider colored noise effects in the high-symbol-packing FTNS regime.

In this paper, we propose a serially concatenated turbo-encoded faster-than-Nyquist signaling (FTNS) transceiver that takes into account FTNS-specific colored noise effects. The proposed low-complexity receiver carries out soft-decision frequency-domain equalization with the aid of the minimum-mean square error criterion while whitening the colored noise. Simulation results demonstrate that the proposed multi-stage-concatenated FTNS system achieves a better error-ratio performance than previous systems that do not consider colored noise effects in the high-symbol-packing FTNS regime. Furthermore, as an explicit benefit of the proposed iterative decoder, near-capacity performance is achieved with practical decoding complexity.