Class Of Decoders Research Articles

Mixed coherent states in coupled chaotic systems: Design of secure wireless communication

A general coupling design is proposed to realize a mixed coherent (MC) state: coexistence of complete synchronization, antisynchronization, and amplitude death in different pairs of similar state variables of the coupled chaotic system. The stability of coupled system is ensured by the Lyapunov function and a scaling of each variable is also separately taken care of. When heterogeneity as a parameter mismatch is introduced in the coupled system, the coupling function facilitates to retain its coherence and displays the global stability with renewed scaling factor. Robust synchronization features facilitated by a MC state enable to design a dual modulation scheme: binary phase shift key (BPSK) and parameter mismatch shift key (PMSK), for secure data transmission. Two classes of decoders (coherent and noncoherent) are discussed, the noncoherent decoder shows better performance over the coherent decoder, mostly a noncoherent demodulator is preferred in biological implant applications. Both the modulation schemes are demonstrated numerically by using the Lorenz oscillator and the BPSK scheme is demonstrated experimentally using radio signals.

Coherent Product Superposition for Downlink Multiuser MIMO

In a two-user broadcast channel where one user has full CSIR and the other has none, a recent result showed that TDMA is strictly suboptimal and a product superposition requiring non-coherent signaling achieves DoF gains under many antenna configurations. This work introduces product superposition in the domain of coherent signaling with pilots, demonstrates the advantages of product superposition in low-SNR as well as high-SNR, and established DoF gains in a wider set of receiver antenna configurations. Two classes of decoders, with and without interference cancellation, are studied. Achievable rates are established by analysis and illustrated by simulations.

Universal Decoding for Arbitrary Channels Relative to a Given Class of Decoding Metrics

We consider the problem of universal decoding for arbitrary unknown channels in the random coding regime. For a given random coding distribution and a given class of metric decoders, we propose a generic universal decoder whose average error probability is, within a sub-exponential multiplicative factor, no larger than that of the best decoder within this class of decoders. Since the optimum, maximum likelihood (ML) decoder of the underlying channel is not necessarily assumed to belong to the given class of decoders, this setting suggests a common generalized framework for: (i) mismatched decoding, (ii) universal decoding for a given family of channels, and (iii) universal coding and decoding for deterministic channels using the individual-sequence approach. The proof of our universality result is fairly simple, and it is demonstrated how some earlier results on universal decoding are obtained as special cases. We also demonstrate how our method extends to more complicated scenarios, like incorporation of noiseless feedback, and the multiple access channel.

Source Coding Using Families of Universal Hash Functions

This correspondence is concerned with new connections between source coding and two kinds of families of hash functions known as the families of universal hash functions and N-strongly universal hash functions, where N ges 2 is an integer. First, it is pointed out that such families contain classes of well-known source codes such as bin codes and linear codes. Next, performance of a source coding scheme using either of the two kinds of families is evaluated. An upper bound on the expectation of the decoding error probability is obtained for each family. The expectation of the decoding error probability is analyzed in detail for the cases of discrete memoryless sources and sources without the memoryless assumption under a certain class of decoders.

Achievable Error Exponents for the Private Fingerprinting Game

Fingerprinting systems in the presence of collusive attacks are analyzed as a game between a fingerprinter and a decoder on the one hand, and a coalition of two or more attackers on the other hand. The fingerprinter distributes, to different users, different fingerprinted copies of a host data (covertext), drawn from a memoryless stationary source, embedded with different fingerprints. The coalition members create a forgery of the data while aiming at erasing the fingerprints in order not to be detected. Their action is modeled by a multiple-access channel (MAC). We analyze the performance of two classes of decoders, associated with different kinds of error events. The decoder of the first class aims at detecting the entire coalition, whereas the second is satisfied with the detection of at least one member of the coalition. Both decoders have access to the original covertext data and observe the forgery in order to identify member(s) of the coalition. Motivated by a worst case approach, we assume that the coalition of attackers is informed of the hiding strategy taken by the fingerprinter and the decoder, while they are uninformed of the attacking scheme. Achievable single-letter expressions for the two kinds of error exponents are obtained. Single-letter lower bounds are also derived for the subclass of constant composition codes. These lower and the upper bounds coincide for the error exponent of the first class. Further, for the error of the first kind, a decoder that is optimal is introduced, and the worst case attack channel is characterized

How often is hard-decision decoding enough?

The problem of decoding binary linear block codes has received much attention; the two extremes are optimal, high-complexity soft-decision (or maximum-likelihood) decoding and lower performance, much lower complexity hard-decision (or algebraic) decoding. This article considers a class of decoders which first implements hard-decision decoding; second, tests to see if that is enough, that its result matches the result of soft-decision decoding; and third, continues to search if a match is not found. The advantage of such a testing procedure is that if the hard-decision decoding result is found to be enough (called a success for the test), then the computational effort expended by the decoder is low. The performance, as measured by the probability of a success, of a variety of simple tests of the hard-decision codeword are analyzed.

On multidimensional coded modulations having uniform error property for generalized decoding and flat-fading channels

We consider the problem of uniform error property (UEP) for a coded modulation with constant energy multidimensional symbols, transmitted over the additive white Gaussian noise (AWGN) or fading channels and received by a broad class of decoders. This class includes coherent, partially coherent, double differential, and noncoherent decoders, decoders designed for fading channels, decoders using one or multiple-symbol observations, and many more. These decoders are described as special cases of a general decoder model. This decoder operates by maximizing an arbitrary likelihood function that its arguments are front-end correlator (matched-filter) outputs, A group code structure that guarantees UEP is developed by using the theory of geometrically uniform codes and applying it to the general decoder. These codes are defined over groups (commonly nonbinary) with isometric mapping to channel symbols. We show the code construction for the specific case of Lth-dimensional M-ary phase-shift keying (MPSK). An additional interesting property of these general uniform error codes is related to the case of noncoherent decoding. We show that when using codes of this family, if a code is noncoherently catastrophic, then it is also rotationally invariant. Then, the use of preceding of the input such that the code becomes rotationally transparent will also make it noncatastrophic.

Algebraic decoding of class of multilevel pseudocyclic codes

The algebraic decoding of a class of multilevel pseudocyclic codes is presented. An affine permutation is employed which does not preserve the original code but changes it into a cyclic code over an extension field. After a cyclic code is obtained the ordinary algebraic decoding techniques are then applicable.

A set of voltage-switched magnetic-core decoding matrices

A class of decoders is described which translates an input of N bits to a unique output signal on one of 2N output line s. This operation is equivalent to that performed by diode decoding matrices except that the output may be a current pulse of several hundred ma (milliamperes) rather than a logical level. The logic on which these decoders are based is described and implementations of it which use only magnetic cores, wires, resistors, and standard semiconductor circuit elements are analyzed. These implementations require as few as N+1 cores, N+1 related drivers, and a single current source. Decoding is accomplished by current steering. Consideration is also given to the use of these matrices for error detection and correction in redundant codes.