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

Near BER optimal partial response codes

Partial response signaling (PRS) codes with maximal minimum Euclidean distance have previously been found by linear programming. These perform very well in the narrowband-high energy region, but they were not optimized for minimal bit error rate (BER), so they are only optimal in the limit of infinite signal to noise ratio. Here we search for codes that perform better for more practical signal to noise ratios. The BER objective function is no longer linear, but it is still conve

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

Serial and parallel concatenations based on faster than Nyquist signaling

We investigate the performance of concatenated coding schemes based on Faster Than Nyquist(FTN) signaling over the AWGN channel. We test both serial and parallel concatenations. In serial concatenation the FTN signaling is considered as the inner encoder and the outer code is a rate b/c convolutional code. In parallel schemes we use two parallel Gaussian channels and transmit FTN pulse trains in both; here a precoding device turns out to be crucial. The convergence behaviour is analysed using EXIT charts. The overall spectral density of the schemes varies but is roughly 1–2 bit/s/Hz. The results, in terms of needed Eb/N0 for reliable communication versus spectral density, are very good

Successive interference cancellation in multistream faster-than-Nyquist Signaling

In earlier work we have extended Mazo's concept of faster-than-Nyquist signaling to pulse trains that modulate adjacent subcarriers, a method we called two dimensional Mazo signaling. The signal processing is similar to orthogonal frequency division multiplex (OFDM) transmission. Despite pulses that are faster than the Nyquist limit and subcarriers that significantly overlap, the transmission achieves the isolated pulse error performance. In this paper we review the method and test a receiver based on successive interference cancellation. It virtually achieves the matched filter bound

Receivers for faster-than-Nyquist signaling with and without turbo equalization

Faster-than-Nyquist (FTN) signaling is a trellis coding method that maintains the error rate while reducing signal bandwidth. The combined effect is to move closer to capacity. We study some basic receiver issues: How to model the signaling efficiently in discrete time, how much the Viterbi receiver can be truncated, and how to combine the method with an outer code. The methods are modeling for minimum phase, minimum distance calculation and receiver tests. Concatenated FTN in a turbo equalization scenario proves to be a strong coding method

New reduced state space BCJR algorithms for the ISI channel

A critical component in detection under intersymbol interference (ISI) and in turbo equalization is the BCJR algorithm. We study two approaches to reducing its computation. First, the state space is reduced by optimizing the receiver's phase-maximizing all pass filter. Then the state space used by the BCJR calculation is reduced by breaking the state into an offset and a main state. These procedures are demonstrated by ISI detection and turbo equalization over strongly bandlimited channels

Faster-than-Nyquist modulation based on short finite pulses

We investigate faster-than-Nyquist modulation based on short finite pulses over the AWGN channel. We consider several pulse shapes and compare their information rates for several system setups. We compare the effect of increasing the alphabet size versus of increasing the signaling rate. The outcome is that for these pulses the FTN symbol rate is of greater importance than the alphabet size. Finally we test some concatenated coding schemes where faster-than-Nyquist modulation constitutes the innermost encoder; the outcome is very good

A minimum distance analysis of a certain class of two dimensional ISI channels

In this paper we perform a minimum distance analysis of a class of two dimensional intersymbol interference channels. In particular, some important cases of multitrack multihead magnetic recording systems fall into the studied class. Previously, Soljanin and Georghiades have studied the same problem as we do. The results derived in this paper are more conclusive and they improve upon theirs. The fundamental proof technique that we will use is to transform the channel into an equivalent minimum phase channel