35,776 research outputs found
Trellis-Coded Non-Orthogonal Multiple Access
In this letter, we propose a trellis-coded non-orthogonal multiple access (NOMA) scheme. The signals for different users are produced by trellis coded modulation (TCM) and then superimposed on different power levels. By interpreting the encoding process via the tensor product of trellises, we introduce a joint detection method based on the Viterbi algorithm. Then, we determine the optimal power allocation between the two users by maximizing the free distance of the tensor product trellis. Finally, we manifest that the trellis-coded NOMA outperforms the uncoded NOMA at high signal-to-noise ratio (SNR)
Dynamical formation of stable irregular transients in discontinuous map systems
Stable chaos refers to the long irregular transients, with a negative largest
Lyapunov exponent, which is usually observed in certain high-dimensional
dynamical systems. The mechanism underlying this phenomenon has not been well
studied so far. In this paper, we investigate the dynamical formation of stable
irregular transients in coupled discontinuous map systems. Interestingly, it is
found that the transient dynamics has a hidden pattern in the phase space: it
repeatedly approaches a basin boundary and then jumps from the bundary to a
remote region in the phase space. This pattern can be clearly visualized by
measuring the distance sequences between the trajectory and the basin boundary.
The dynamical formation of stable chaos originates from the intersection points
of the discontinuous boundaries and their images. We carry out numerical
experiments to verify this mechanism.Comment: 5 pages, 5 figure
Nonparametric Detection of Geometric Structures over Networks
Nonparametric detection of existence of an anomalous structure over a network
is investigated. Nodes corresponding to the anomalous structure (if one exists)
receive samples generated by a distribution q, which is different from a
distribution p generating samples for other nodes. If an anomalous structure
does not exist, all nodes receive samples generated by p. It is assumed that
the distributions p and q are arbitrary and unknown. The goal is to design
statistically consistent tests with probability of errors converging to zero as
the network size becomes asymptotically large. Kernel-based tests are proposed
based on maximum mean discrepancy that measures the distance between mean
embeddings of distributions into a reproducing kernel Hilbert space. Detection
of an anomalous interval over a line network is first studied. Sufficient
conditions on minimum and maximum sizes of candidate anomalous intervals are
characterized in order to guarantee the proposed test to be consistent. It is
also shown that certain necessary conditions must hold to guarantee any test to
be universally consistent. Comparison of sufficient and necessary conditions
yields that the proposed test is order-level optimal and nearly optimal
respectively in terms of minimum and maximum sizes of candidate anomalous
intervals. Generalization of the results to other networks is further
developed. Numerical results are provided to demonstrate the performance of the
proposed tests.Comment: Submitted for journal publication in November 2015. arXiv admin note:
text overlap with arXiv:1404.029
Reply to "Comment on 'Semiquantum-key distribution using less than four quantum states' "
Recently Boyer and Mor pointed out the first conclusion of Lemma 1 in our
original paper is not correct, and therefore, the proof of Theorem 5 based on
Lemma 1 is wrong. Furthermore, they gave a direct proof for Theorem 5 and
affirmed the conclusions in our original paper. In this reply, we admit the
first conclusion of Lemma 1 is not correct, but we need to point out the second
conclusion of Lemma 1 is correct. Accordingly, all the proofs for Lemma 2,
Lemma 3, and Theorems 3--6 are only based on the the second conclusion of Lemma
1 and therefore are correct.Comment: 1 pag
Time-and event-driven communication process for networked control systems: A survey
Copyright © 2014 Lei Zou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In recent years, theoretical and practical research topics on networked control systems (NCSs) have gained an increasing interest from many researchers in a variety of disciplines owing to the extensive applications of NCSs in practice. In particular, an urgent need has arisen to understand the effects of communication processes on system performances. Sampling and protocol are two fundamental aspects of a communication process which have attracted a great deal of research attention. Most research focus has been on the analysis and control of dynamical behaviors under certain sampling procedures and communication protocols. In this paper, we aim to survey some recent advances on the analysis and synthesis issues of NCSs with different sampling procedures (time-and event-driven sampling) and protocols (static and dynamic protocols). First, these sampling procedures and protocols are introduced in detail according to their engineering backgrounds as well as dynamic natures. Then, the developments of the stabilization, control, and filtering problems are systematically reviewed and discussed in great detail. Finally, we conclude the paper by outlining future research challenges for analysis and synthesis problems of NCSs with different communication processes.This work was supported in part by the National Natural Science Foundation of China under Grants 61329301, 61374127, and 61374010, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany
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