299 research outputs found
Multistream faster than Nyquist signaling
We extend Mazo's concept of faster-than-Nyquist (FTN) signaling to pulse trains that modulate a bank of subcarriers, a method called two dimensional FTN signaling. The signal processing is similar to orthogonal frequency division multiplex (OFDM) transmission but the subchannels are not orthogonal. Despite nonorthogonal pulses and subcarriers, the method achieves the isolated-pulse error performance; it does so in as little as half the bandwidth of ordinary OFDM. Euclidean distance properties are investigated for schemes based on several basic pulses. The best have Gaussian shape. An efficient distance calculation is given. Concatenations of ordinary codes and FTN are introduced. The combination achieves the outer code gain in as little as half the bandwidth. Receivers must work in two dimensions, and several iterative designs are proposed for FTN with outer convolutional coding
High performance faster-than-nyquist signaling
AbstractIn a wireless broadband context, multi-path dispersive channels can severely affectdata communication of Mobile Terminals (MTs) uplink.Single Carrier withFrequency-Domain Equalization (SC-FDE) has been proposed to deal with highlydispersive channels for the uplink of broadband wireless systems. However, currentsystems rely on older assumptions of the Nyquist theorem and assume that a systemneeds a minimum bandwidth 2Wper MT. Faster-Than-Nyquist (FTN) assumesthat it is possible to employ a bandwidth as low as 0.802 of the original Nyquistbandwidth with minimum loss - despite this, the current literature has only proposedcomplex receivers for a simple characterization of the wireless channel. Furthermore,the uplink of SC-FDE can be severely affected by a deep-fade and or poor channelconditions; to cope with such difficulties Diversity Combining (DC) Hybrid ARQ(H-ARQ) is a viable technique, since it combines the several packet copies sent bya MT to create reliable packet symbols at the receiver.In this thesis we consider the use of FTN signaling for the uplink of broadbandwireless systems employing SC-FDE based on the Iterative Block with DecisionFeedback Equalization (IB-DFE) receiver with a simple scheduled access HybridAutomatic Repeat reQuest (H-ARQ) specially designed taking into account thecharacteristics of FTN signals. This approach achieves a better performance thanNyquist signaling by taking advantage of the additional bandwidth employed of aroot-raised cosine pulse for additional diversity.Alongside a Packet Error Rate (PER) analytical model, simulation results show that this receiver presents a better performance when compared with a regular system,with higher system throughputs and a lower Energy per Useful Packet (EPUP)
Coordinate Interleaved Faster-than-Nyquist Signaling
Faster-than-Nyquist (FTN) signaling is an attractive transmission technique
which accelerates data symbols beyond the Nyquist rate to improve the spectral
efficiency; however, at the expense of higher computational complexity to
remove the introduced intersymbol interference (ISI). In this work, we
introduce a novel FTN signaling transmission technique, named coordinate
interleaved FTN (CI-FTN) signaling that exploits the ISI at the transmitter to
generate constructive interference for every pair of the counter-clockwise
rotated binary phase shift keying (BPSK) data symbols. In particular, the
proposed CI- FTN signaling interleaves the in-phase (I) and the quadrature (Q)
components of the counter-clockwise rotated BPSK symbols to guarantee that
every pair of consecutive symbols has the same sign, and hence, has
constructive ISI. At the receiver, we propose a low-complexity detector that
makes use of the constructive ISI introduced at the transmitter. Simulation
results show the merits of the CI-FTN signaling and the proposed low-complexity
detector compared to conventional Nyquist and FTN signaling
Time Localization and Capacity of Faster-Than-Nyquist Signaling
In this paper, we consider communication over the bandwidth limited analog
white Gaussian noise channel using non-orthogonal pulses. In particular, we
consider non-orthogonal transmission by signaling samples at a rate higher than
the Nyquist rate. Using the faster-than-Nyquist (FTN) framework, Mazo showed
that one may transmit symbols carried by sinc pulses at a higher rate than that
dictated by Nyquist without loosing bit error rate. However, as we will show in
this paper, such pulses are not necessarily well localized in time. In fact,
assuming that signals in the FTN framework are well localized in time, one can
construct a signaling scheme that violates the Shannon capacity bound. We also
show directly that FTN signals are in general not well localized in time.
Therefore, the results of Mazo do not imply that one can transmit more data per
time unit without degrading performance in terms of error probability.
We also consider FTN signaling in the case of pulses that are different from
the sinc pulses. We show that one can use a precoding scheme of low complexity
to remove the inter-symbol interference. This leads to the possibility of
increasing the number of transmitted samples per time unit and compensate for
spectral inefficiency due to signaling at the Nyquist rate of the non sinc
pulses. We demonstrate the power of the precoding scheme by simulations
Faster-than-Nyquist Signaling for MIMO Communications
Faster-than-Nyquist (FTN) signaling is a non-orthogonal transmission
technique, which has the potential to provide significant spectral efficiency
improvement. This paper studies the capacity of FTN signaling for both
frequency-flat and for frequency-selective multiple-input multiple-output
(MIMO) channels. We show that precoding in time and waterfilling in space is
capacity achieving for frequency-flat MIMO FTN. For frequency-selective fading,
joint waterfilling in time, space and frequency is required.Comment: Have been submitted to IEEE transactions on wireless communication
Constrained capacities for faster-than-Nyquist signaling
This paper deals with capacity computations of faster-than-Nyquist (FTN) signaling. It shows that the capacity of FTN is higher than the orthogonal pulse linear modulation capacity for all pulse shapes except the sinc. FTN signals can in fact achieve the ultimate capacity for the signal power spectral density (PSD). The paper lower and upper bounds the FTN capacity under the constraint of finite input alphabet. It is often higher than the capacity for comparable orthogonal pulse systems; sometimes it is superior to all forms of orthogonal signaling with the same PSD
Impact of Spectrum Sharing on the Efficiency of Faster-Than-Nyquist Signaling
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.Comment: IEEE copyrights notice applies. This paper is accepted at WCNC 201
Faster-than-Nyquist signaling for next generation communication architectures
We discuss a few promising applications of the faster-than-Nyquist (FTN) signaling technique. Although proposed in the mid 70s, thanks to recent extensions this technique is taking on a new lease of life. In particular, we will discuss its applications to satellite systems for broadcasting transmissions, optical long-haul transmissions, and next-generation cellular systems, possibly equipped with a large scale antenna system (LSAS) at the base stations (BSs). Moreover, based on measurements with a 128 element antenna array, we analyze the spectral efficiency that can be achieved with simple receiver solutions in single carrier LSAS systems
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