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.
We consider the problem of bounding the information rate of intersymbol interference channels via simulation-based algorithms. The adopted approach, which is based on a general class of ...reduced-complexity receivers that includes several previously studied receivers as special cases, leads to provable upper and lower bounds on the information rate of interest. As a by-product of the information-theoretic investigations, novel insights on the design of efficient reduced-complexity receivers are also provided, since the proposed lower bounds are known to be achievable by practical receivers. In many scenarios, our novel approach significantly outperforms the existing ones, for all practical values of the signal-to-noise ratio.
Mazo, in 1975, showed that the signaling rate of a linear modulation can be significantly higher than the maximum rate for orthogonal signaling without any loss of minimum square Euclidean distance. ...In subsequent literature the highest such rate is referred to as the Mazo-limit. In this letter we ask whether there exists a Mazo-limit also on MIMO channels. The answer is yes, but it applies to the largest pairwise error probability rather than to minimum square Euclidean distance. Moreover, it occurs at exactly the same rate as in the AWGN case. As a special case results for single-input single-output fading channels are obtained.
Faster than Nyquist (FTN) signaling is an important method of narrowband coding. The concept is extended here to non binary signal constellations; these are much more bandwidth efficient than binary ...ones. A powerful method of finding the minimum distance for binary and non binary FTN is presented. Preceding FTN transmissions with short linear filters proves to be an effective way to gain distance. A Shannon limit to bit error rate is derived that applies for FTN. Tests of an M-algorithm receiver are performed and compared to this limit.
We present a method to compute, quickly and efficiently, the mutual information achieved by an independent identically distributed (IID) complex Gaussian signal on a block Rayleigh-faded channel ...without side information at the receiver. The method accommodates both scalar and multiple-input multiple-output (MIMO) settings. Operationally, this mutual information represents the highest spectral efficiency that can be attained using Gaussian codebooks. Examples are provided that illustrate the loss in spectral efficiency caused by fast fading and how that loss is amplified when multiple transmit antennas are used. These examples are further enriched by comparisons with the channel capacity under perfect channel-state information at the receiver, and with the spectral efficiency attained by pilot-based transmission.
We deal with the construction of optimal channel shortening, also known as combined linear Viterbi detection, algorithms for ISI and MIMO channels. In the case of MIMO channel shortening, the tree ...structure to represent MIMO signals is replaced by a trellis. The optimization is performed from an information theoretical perspective and the achievable information rates of the shortened models are derived and optimized. Closed form expressions for all components of the optimal detector of the class are derived. Furthermore, we show that previously published channel shortening algorithms can be seen as special cases of the derived model.
This correspondence investigates the asymptotic behavior of reduced-state intersymbol interference (ISI) equalizers, based on the Ungerboeck and Forney observation models. It is shown that ...Ungerboeck-based equalizers can suffer from correct-path-loss (CPL) even in the noiseless regime. ISI conditions that lead to CPL are analytically derived and illustrated by examples.
Consider receivers that do not exploit any knowledge of the channel distribution in non-coherent block-fading multiple-input multiple-output (MIMO) channels. The main contribution of this letter is ...to derive a semi-analytical semi-numerical lower bound to the achieveble rate of such receivers. The bound is of operational meaning since practical receivers can achieve the lower bound. Several numerical examples with Gaussian block fading channels, which illuminate that the lack of channel distribution at the receiver imposes a significant penalty if the coherence time (counted in symbol times) is not much larger than the number of transmit antennas, are provided.
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.
We perform a minimum distance analysis of a class of two-dimensional intersymbol interference (ISI) channels applicable to multitrack magnetic recording and orthogonal frequency division multiplex ...transmission systems. Exact minimum distance for a wide class of ISI responses is derived. The fundamental analytical technique is to transform the channel into an equivalent minimum phase channel. The results improve upon the prior work of Soljanin and Georghiades.
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