A Belief Propagation Based Framework for Soft Multiple-Symbol Differential Detection

Soft noncoherent detection, which relies on calculating the \textit{a posteriori} probabilities (APPs) of the bits transmitted with no channel estimation, is imperative for achieving excellent detection performance in high-dimensional wireless communications. In this paper, a high-performance belief propagation (BP)-based soft multiple-symbol differential detection (MSDD) framework, dubbed BP-MSDD, is proposed with its illustrative application in differential space-time block-code (DSTBC)-aided ultra-wideband impulse radio (UWB-IR) systems. Firstly, we revisit the signal sampling with the aid of a trellis structure and decompose the trellis into multiple subtrellises. Furthermore, we derive an APP calculation algorithm, in which the forward-and-backward message passing mechanism of BP operates on the subtrellises. The proposed BP-MSDD is capable of significantly outperforming the conventional hard-decision MSDDs. However, the computational complexity of the BP-MSDD increases exponentially with the number of MSDD trellis states. To circumvent this excessive complexity for practical implementations, we reformulate the BP-MSDD, and additionally propose a Viterbi algorithm (VA)-based hard-decision MSDD (VA-HMSDD) and a VA-based soft-decision MSDD (VA-SMSDD). Moreover, both the proposed BP-MSDD and VA-SMSDD can be exploited in conjunction with soft channel decoding to obtain powerful iterative detection and decoding based receivers. Simulation results demonstrate the effectiveness of the proposed algorithms in DSTBC-aided UWB-IR systems.Comment: 14 pages, 12 figures, 3 tables, accepted to appear on IEEE Transactions on Wireless Communications, Aug. 201

Detecting Byzantine Attacks Without Clean Reference

We consider an amplify-and-forward relay network composed of a source, two relays, and a destination. In this network, the two relays are untrusted in the sense that they may perform Byzantine attacks by forwarding altered symbols to the destination. Note that every symbol received by the destination may be altered, and hence no clean reference observation is available to the destination. For this network, we identify a large family of Byzantine attacks that can be detected in the physical layer. We further investigate how the channel conditions impact the detection against this family of attacks. In particular, we prove that all Byzantine attacks in this family can be detected with asymptotically small miss detection and false alarm probabilities by using a sufficiently large number of channel observations \emph{if and only if} the network satisfies a non-manipulability condition. No pre-shared secret or secret transmission is needed for the detection of these attacks, demonstrating the value of this physical-layer security technique for counteracting Byzantine attacks.Comment: 16 pages, 7 figures, accepted to appear on IEEE Transactions on Information Forensics and Security, July 201

Wireless information and energy transfer in multi-cluster MIMO uplink networks through opportunistic interference alignment

In this paper, we consider a K-cluster (K >= 2) simultaneous wireless information and power transfer (SWIPT) network, where S nodes (S >= 2) are selected from N nodes within each cluster for the uplink information transmission (IT) and the remaining N - S idle nodes are dedicated to energy harvesting (EH). Based on the intra-cluster performance aware (ICPA) philosophy, a pair of opportunistic interference alignment (OIA) schemes, namely the coarse ICPA-OIA (C-ICPA-OIA) and the refined ICPA-OIA (R-ICPA-OIA), are proposed for balancing the sum rate performance achieved and the energy harvested. Specifically, the C-ICPA-OIA treats the overall signal strength within the reference signal subspace (RSS) as a coarse description of the node’s effective signal strength. By comparison, to take full advantage of zero-forcing (ZF) based reception, the R-ICPA-OIA considers the projected signal strength with respect to the orthonormal basis of RSS as a substantially refined description of the node’s effective signal strength. Furthermore, we analyzed the harvested power and the working time of the system. Extensive simulation results validate our theoretical analyses, demonstrating that our schemes outperform the existing OIA schemes

Research of the wrinkling elimination of stainless steel SUS304 by viscous pressure

Wrinkling is one of the most important factors influencing a forming precision of sheet metal, which brings difficulties to the forming process of sheet metal. In order to eliminate the wrinkling during the forming process, an accurate prediction is necessary. In this paper, the wrinkling elimination process was investigated based on the principle of the Yoshida Buckling Test (YBT) and viscous pressure forming. The experimental device was designed, and evaluation method of the wrinkling elimination rate was presented by the stainless steel SUS304. On this basis, the wrinkling elimination experiment was carried out, the influences of both the viscous medium molecular weight and the tensile state of wrinkle under the viscous pressure on the wrinkling elimination were obtained

Influence of welding quality on stability of SUS304 tube-compression by viscous pressure forming

One of the major problems affecting viscous pressure forming (VPF) is the stability of tubecompression, whereas the main defect influencing the stability of welded tube-compression is the quality of welded joints. This article utilizes the finite element method to analyze the influence of weld joint strength and width on stability of SUS304 tube-compression by VPF. Meanwhile, SUS304 welded tube-blanks with different weld joint strength and width are obtained by plasma welding, TIG-Tungsten Inert Gas welding, laser welding and high frequency welding and then the stability test by VPF is carried out. The results showed that the weld joint strength and width affect the stability of tube-compression. The system and process of controlling weld joint width can improve the stability of tube-blank preferably relative to weld joint strength

Influence of welding quality on stability of SUS304 tube-compression by viscous pressure forming

One of the major problems affecting viscous pressure forming (VPF) is the stability of tubecompression, whereas the main defect influencing the stability of welded tube-compression is the quality of welded joints. This article utilizes the finite element method to analyze the influence of weld joint strength and width on stability of SUS304 tube-compression by VPF. Meanwhile, SUS304 welded tube-blanks with different weld joint strength and width are obtained by plasma welding, TIG-Tungsten Inert Gas welding, laser welding and high frequency welding and then the stability test by VPF is carried out. The results showed that the weld joint strength and width affect the stability of tube-compression. The system and process of controlling weld joint width can improve the stability of tube-blank preferably relative to weld joint strength