Constellation Design for Media-Based Modulation Using Block Codes and Squaring Construction

We propose two low-complexity lattice code constructions that have competitive coding and shaping gains. The first construction, named systematic Voronoi shaping , maps short blocks of integers to the dithered Voronoi integers, which are dithered integers that are uniformly distributed over the Voronoi region of a low-dimensional shaping lattice. Then, these dithered Voronoi integers are encoded using a high-dimensional lattice retaining the same shaping and coding gains of low- and high-dimensional lattices. A drawback to this construction is that there is no isomorphism between the underlying message and the lattice code, preventing its use in applications such as compute-and-forward. Therefore, we propose a second construction, called mixed nested lattice codes , in which a high-dimensional coding lattice is nested inside a concatenation of low-dimensional shaping lattices. This construction not only retains the same shaping/coding gains as first construction but also provides the desired algebraic structure. We numerically study these methods, for point-to-point channels as well as compute-and-forward using low-density lattice codes as coding lattices and $E_{8}$ and Barnes–Wall as shaping lattices. Numerical results indicate a shaping gain of up to 0.86 dB, compared with the state-of-the-art of 0.4 dB; furthermore, the proposed method has lower complexity than the state-of-the-art approaches.

It has been conjectured that lattice codes are good for (almost) everything. As an additional bit of evidence for this claim, we offer a few results showing the utility of lattice codes for the AWGN relay channel. We show that the decode-and-forward rates of the relay channel can be achieved using lattice encoding and decoding. We present an encoding/decoding technique that uses a doubly-nested lattice code. Encoding is accomplished using a combination of superposition encoding and block Markov encoding, while decoding is accomplished using a strategy reminiscent of Cover and El Gamal's list decoding. Our technique can be extended to a wide variety of relay topologies, including the half-duplex relay channel and the cooperative multiple-access channel.

Mirror activation pattern (MAP) in media-based modulation (MBM) refers to the ON/OFF status of radio-frequency mirrors, which create different near field geometries for different ON/OFF combinations. In this letter, we introduce a novel coding scheme for MBM in which indices are assigned to MAPs, such that these indices are used as labels for the elements in a Galois field. The MAP indices are then coded across time, and the block transmission is carried out. The resulting signal set has good distance distribution, which leads to good bit error performance. Structured sparse matrix sketching-based signal detection algorithms for the proposed scheme are presented.

We present a natural and low-complexity technique for achieving the capacity of the Gaussian relay network in the high SNR regime. Specifically, we propose the use of end-to-end structured lattice codes with the amplify-and-forward strategy, where the source uses a nested lattice code to encode the messages and the destination decodes the messages by lattice decoding. All intermediate relays simply amplify and forward the received signals over the network to the destination. We show that the end-to-end lattice-coded amplify-and-forward scheme approaches the capacity of the layered Gaussian relay network in the high SNR regime. Next, we extend our scheme to non-layered Gaussian relay networks under the amplify-and-forward scheme, which can be viewed as a Gaussian intersymbol interference (ISI) channel. Compared with other schemes, our approach is significantly simpler and requires only the end-to-end design of the lattice precoding and decoding. It requires little knowledge of the network topology or the individual channel gains.

For assessing the core critical heat flux ratio in VVER-type nuclear reactors, the lattice computation code TIGRSP (steady-state thermal and hydraulic analysis of parameters in fuel rod bundles) is used. Despite the fact that quite a large amount of verification studies has been accomplished and that the code has passed the certification procedure, work on improving the code capabilities is still being continued. One of the modern tendencies is the wide-scale involvement of CFD codes for studying local parameters in fuel assemblies (FAs). Along with comparison with experimental data, it is advisable to carry out cross verification of lattice codes with the results of 3D thermal-hydraulic computations for conditions for which experimental data are either lacking or limited for some or other reasons. This article considers thermal-hydraulic processes during coolant flow in a 19-rod assembly with parameters close to the nominal conditions in the FAs of a VVER-1000 reactor. The 3D model is verified with respect to empirical formulas and experimental data. Based on the results of test and verification computations, we determined the mesh and turbulence model parameters using the ANSYS CFX code by means of which it is possible to obtain reliable results in estimating the hydraulic characteristics of FAs fitted with spacer grids, heat transfer in the single-phase region, and coolant flow distribution over the FA cross section. The CFD computation of coolant flow for the 19-rod assembly is carried out, and the coolant mass velocity and temperature in different sections over the length and corresponding cells of the TIGRSP code are calculated. The TIGRSP code has been verified against experimental data and taking into account the CFD simulation of the 19-rod FA, and a software module for graphically visualizing the lattice code output results has been developed. The presented data can be used for verification of thermal-hydraulic codes and in elaborating the design of FAs for VVER-type reactors.

Wireless Physical Layer Network Coding (WNC) techniques exploit the inherent nature of wireless channels to improve the performance of wireless communication systems. Unlike conventional Network Coding, in WNC the transmitted signals constructively interact directly in the constellation space, thus inducing specific requirements on the source constellation design. Suitable multi-source constellations should enable direct decoding of WNC functions of user data (from the observed superimposed constellations at receiving nodes) and simultaneously they should allow delivery of partial information to nodes with worse channel conditions (exploiting the natural broadcast property of wireless channels). Source constellations possessing both the aforementioned attributes simultaneously can be desirable in a WNC-based system and thus proper constellation design can become a relatively challenging task. In this paper we focus on this problem and we introduce a systematic constellation design algorithm for a 5-node Wireless Butterfly Network (WBN) with WNC processing, where the basic principles of multi-source constellation design for WNC systems can be demonstrated. We show that the proposed constellations outperform the conventional approaches over the whole range of SNR conditions in the system.

The union bound is known as the most useful tool for the computation of error probability in digital communication schemes (both coded and non-coded). Given a signal set or codebook C={x/sub 0/,x/sub 1/,...,x/sub M-1/}, the conditional error probability P(e|x/sub 0/) is upper bounded by a sum of pairwise error probabilities (PEP). Here we consider the additive white Gaussian channel, where C is a discrete and finite set of points in the N-dimensional real Euclidean space. In this case, the PEPs are the probabilities of the noise taking a signal on the other side of the hyperplane bounding the decision regions of x/sub 0/ and x/sub i/. An important step toward the reduction of the union bound to its minimal form was made by Verdu, who derived a theorem, commonly referred to as the Verdu-Shields theorem showing how terms can be removed from the upper bound to error probability in the case of binary antipodal transmission over the Gaussian channel with intersymbol interference. In this paper we derive a generalization of the Verdu-Shields theorem which provides a sufficient condition for expurgating a given error sequence x/sub k/ from the union bound.

Recent studies have shown that analog joint source-channel coding (AJSCC) is capable of approaching the optimum performance theoretically attainable (OPTA). However, it would be costly to transmit the continuous output of AJSCC. This paper proposes a two-dimensional (2D) quantization-based modulation scheme to map the discrete-time real-valued source encoder output into a finite set of 2D constellation points for modulated transmission. To minimize the resultant quantization distortion, the constellation is optimized by constructing a centroidal Voronoi diagram that can best match the distribution of the source encoder output under power transformation. Based on a comprehensive analysis of effects of encoder configuration and power transformation in connection with the channel condition, an algorithm is presented for jointly optimizing the source encoder and the constellation, with the objective of maximizing the system performance in terms of the end-to-end signal-to-distortion ratio (SDR) with respect to the channel condition in terms of signal-to-noise ratio (SNR). Simulation results show that under joint optimization, the modulated AJSCC system improves as the modulation order increases, and it tends to approach the benchmark performance of the unmodulated system that is close to the OPTA. More practically, the modulated AJSCC system is robust to tolerate imperfect channel estimation to some extent. This work provides a promising way of enabling a source-oriented AJSCC system to access digital communication networks.

PARCS code multi-group neutron diffusion constants generation using Monte Carlo method

Consider a slowly fading Gaussian relay channel where the source is not aware of channel state information (CSI) and the relay is only partially aware of CSI. As a single cooperation strategy, Decode-and-Forward (DF) or Compress-and-Forward (CF), is not the best for all channel states, the relay should be able to switch between them according to its CSI. However as the source cannot be aware of chosen cooperative strategy, it should use so called oblivious codes that perform equally well under different cooperative strategies. In this paper, we prove that doubly nested lattice codes is an oblivious code which can be used to achieve DF, CF or point-to-point rate in the relay channels. Using the oblivious lattice coding, the relay, according to its CSI, decides to use DF, CF or no cooperation at all. We show that inner bound on outage probability is significantly improved if the oblivious lattice code is used with selective coding strategy at the relay.

Nuclear-data uncertainty propagations in burnup calculation for the PWR assembly

In this paper, a novel 3-dimensional (3-D) constellation design is proposed for spatial modulation (SM) multiple-antenna system (MIMO) employing maximum ratio combing (MRC) detector. The 3-D constellation is established for spatial modulated systems to minimize the system symbol error rate (SER) by jointly exploiting the potential of both antenna and signal domains. A low-complexity and efficient design algorithm is proposed to find out the 3-D constellation sub-optimally. The performance of the jointly mapped SM (JM-SM) with the designed 3-D constellation is investigated. Simulation results show that the proposed JM-SM schemes can bring obvious performance gain compared with the existing adaptive SM systems under the same spectral efficiency.

Trellis coding using multidimensional quadrature amplitude modulation (QAM) signal sets is investigated. Finite-size 2D signal sets are presented that have minimum average energy, are 90 degrees rotationally symmetric, and have from 16 to 1024 points. The best trellis codes using the finite 16-QAM signal set with two, four, six, and eight dimensions are found by computer search (the multidimensional (multi-D) signal set is constructed from the 2-D signal set). The best moderate complexity trellis codes for infinite lattices with two, four six, and eight dimensions are also found. The minimum free squared Euclidean distance and number of nearest neighbors for these codes were used as the selection criteria. Many of the multi-D codes are fully rotationally invariant and give asymptotic coding gains up to 6.0 dB. From the infinite lattice codes, the best codes for transmitting J, J+1/4, J+1/3, J+1/2, J+2/3, and J+3/4 b/sym (J an integer) are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

For the transmission of video on time variant mobile radio channels we discuss a self-adapting hierarchical channel coding scheme. Based on the cutoff rate for multilevel coding on fading channels we derive a procedure for the joint design of unequal error protection and clustered signal constellation.

Bit-interleaved turbo-coded modulations (BITCM) have been shown to achieve bit error rate performance very close to the capacity limit over both additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. So far, most studies have been done on BITCM systems designed using rectangular QAM signal sets. In this paper, we address the problem of finding some constellations that would be more suitable than rectangular QAM for designing power efficient BITCM. When the parameter M is in the form M=2/sup 2p/ where p is an integer, we show that rectangular QAM constellations are surprisingly the most attractive signal sets for the design of power-efficient BITCM schemes over AWGN channels. This is not necessarily true with Rayleigh fading channels.