Trellis Structure Research Articles

Percentage Coverage of Tropical Climbing Plants of Green Facade

Green façade (GF) is one of vertical greenery systems used as passive solutions applied on building façade in improving indoor thermal environment and energy efficiency. However, optimum improvement of thermal environment from GF is dependent on the overall foliage coverage established on the system itself. Higher percentage coverage of the foliage is expected to regulate and lessen the heat transfer toward inside environment. Therefore, this study is to investigate the potential of selected tropical climbing plants in establishing foliage coverage on the GF. Three selected tropical species of climbers used on green façade; i.e. Anemopaegma chamberlaynii (AC), Antigonon leptopus (AL), and Quisqualis indica (QI). A small-scale experiment with small scale size of freestanding walls (1.5 m (height) × 1.0 m (width) × 0.15 m (thick)) attached with GFs (modular trellis) and planter boxes at ground were built for this study. Despite small size leaf, AC performed consistently and has the highest percentage coverage throughout the measurement period with average of 86.5 %. The dominant trait of AC which is vigorous and fast growth rate contributed to the dense and almost fully covered the trellis structure of green façade. Higher percentage coverage also estimated to generate an instantaneous effect on thermal environment modification.

Mechanical contribution of secondary phloem to postural control in trees: the bark side of the force.

To grow straight, plants need a motor systemthat controls posture by generating forces to offset gravity. This motor function in trees was long thought to be only controlled by internal forces induced in wood. Here we provide evidence that bark is involved in the generation of mechanical stresses in several tree species. Saplings of nine tropical species were grown tilted and staked in a shadehouse and the change in curvature of the stem was measured after releasing from the pole and after removing the bark. This first experiment evidenced the contribution of bark in the up-righting movement of tree stems. Combined mechanical measurements of released strains on adult trees and microstructural observations in both transverse and longitudinal/tangential plane enabled us to identify the mechanism responsible for the development of asymmetric mechanical stress in the bark of stems of these species. This mechanism does not result from cell wall maturation like in wood, or from the direct action of turgor pressure like in unlignified organs, but is the consequence of the interaction between wood radial pressure and a smartly organized trellis structure in the inner bark.

Factor Graph Aided Multiple-Symbol Differential Detection in the Broadcasting Phase of a Network Coding Based UWB Relay System

A factor-graph-aided multiple-symbol differential detection (FG-MSDD) is proposed and its performance is analyzed and evaluated in the broadcasting phase (i.e., the downlink phase) of an ultra-wideband (UWB) two-way relay system (TWRS). In the downlink of the TWRS, the relay is transmitting network-coded information to the sources, and each source node aims to calculate a posteriori probabilities (APPs) of the information symbols from the relay node. A sampling method based on the modified autocorrelation receiver is proposed for FG-MSDD, which has a trellis structure. The trellis can be decomposed into multiple subtrellises depending on the FG factorization. Then, a methodology for APPs is derived when the forward-and-backward message passing is performed on the subtrellises. The main advantage of FG-MSDD is that it exploits soft information accurately with the aid of the bidirectional message passing. In addition, the proposed FG-MSDD, in conjunction with any soft-input soft-output (SISO) decoding scheme, is capable of obtaining an iterative detection algorithm. Various performance evaluation results obtained by means of computer simulations have verified that the proposed algorithm improves detection performance for the noncoherent UWB TWRS.

Discrete-Phase Constant Envelope Precoding for Massive MIMO Systems

We consider downlink of a multiuser massive multiple-input multiple-output (MIMO) system and focus on reducing the hardware costs by using a single common power amplifier and separate phase shifters (PSs) for antenna front-ends. In the previous literature, the use of analog PSs in this setup has been considered. Here, we study the use of practical digital PSs, which only support a limited set of discrete phases. Considering the sum of interference powers as a metric, we formulate the corresponding nonlinear discrete optimization problem and solve for the phases to be used during transmission. We devise a low-complexity algorithm, which employs a trellis structure providing suboptimal, but efficient and effective solutions. We demonstrate via examples that the proposed solutions have comparable performance to conventional analog PS-based algorithms. Furthermore, we prove that by utilizing discrete-phase constant envelope precoding, the interference can be made arbitrarily small by increasing the number of antennas. Therefore, the asymptotic gains promised by massive MIMO systems are preserved. We also obtain closed-form expressions for the rate loss due to errors in the phase and amplitude of the PSs, for both low and high SNR regimes.

Решение нелинейной задачи по определению прогибов решетчатых пролетных строений

Решение нелинейной задачи по определению прогибов решетчатых пролетных строений

Multihead Multitrack Detection for Next Generation Magnetic Recording, Part I: Weighted Sum Subtract Joint Detection With ITI Estimation

Multitrack detection with array-head reading is a promising technique proposed for next generation magnetic storage systems. The multihead multitrack (MHMT) system is characterized by intersymbol interference in the downtrack direction and intertrack interference (ITI) in the crosstrack direction. Constructing the trellis of a MHMT maximum likelihood (ML) detector requires knowledge of the ITI, which is generally unknown at the receiver. Furthermore, in a time-varying ITI environment, updating ML trellis labels using adaptively-generated ITI estimates could incur significant delay. In this paper, we propose one approach to solve these issues. The proposed detector uses a different trellis structure whose output labels are independent of the ITI level, with ITI-dependence appearing only in a scale factor used to suitably weight the computed path metrics in order to retain ML optimality. The detector formulation facilitates the design of a gain loop structure that can track the time-varying ITI and provide ITI estimates to adaptively adjust the weights in the path metric evaluation. Simulation results show that the proposed detector architecture with ITI estimation offers a substantial performance advantage over ML detection using a static ITI estimate.

Comparative investigation into Viterbi based and multiple hypothesis based track stitching

In this study a comparative analysis is performed between a novel Viterbi based and multiple hypothesis based track stitching algorithms. The track fragments in the Viterbi based track stitching algorithm are modelled as nodes in a trellis structure. A sequential Viterbi data association algorithm is then used to solve the trellis and associate track fragments with each other. A Kalman filter is used to determine the possible associations as well as the probabilities of the associations between the track fragments. In the multiple hypothesis track stitching algorithm, the hypothesis based multiple hypothesis tracking (MHT) algorithm is extended to perform track fragment to track fragment associations, rather than associating observations to tracks. Aspects of the developed multiple hypothesis algorithm are compared with implementations of a similar nature. Novel aspects of this research include the modification of the sequential Viterbi algorithm, as well as the extension of the MHT algorithm to solve the track stitching problem. It was found that the sequential Viterbi track stitching algorithm performed somewhat better than the multiple hypothesis track stitching algorithm for similar execution times. The Viterbi based track stitching algorithm is also shown to produce more consistently acceptable results.

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.

Achieving FEC and RLL for VLC: A Concatenated Convolutional-Miller Coding Mechanism

Run-length limited (RLL) codes are widely used in visible light communications to avoid long runs of 1s and 0s that potentially cause the flicker. This letter explores the serial concatenation of convolutional codes and Miller codes to simultaneously achieve forward error correction and RLL control. Miller codes with high bandwidth efficiency are much ignored in practice due to their disappointing power efficiency. The novelty of this letter is that we identity the merit of this previously unfavorable RLL code (i.e., trellis structure and soft decidability), exploit some important coding principles (i.e., interleaved serial concatenation and soft-iterative decoding), and assemble it to a powerful turbo structure that makes it outperform the existing favorable choices. A modified Bahl-Cocke-Jelinek-Raviv decoding algorithm is developed for the proposed concatenation. Analysis and simulations confirm that the new system is capable of solid RLL control and a superb performance better than the existing schemes.

Turbo Quantization of Oversampled Signals

We present a new iterative quantization procedure for oversampled frames with guaranteed convergence and stability. The procedure uses similar concepts to that of turbo decoding in the context of error control coding. The quantization process is modeled as a quadratic integer-programming problem. A trellis structure is introduced to solve the problem, where the quantized coefficients represent a path through the trellis diagram. The quantization metric is iteratively improved through turbo iterations by exchanging quantization extrinsic information. The proposed procedure is shown to provide significant improvement over prior art in quantization and integer programming.

Space Time State Trellis Codes for MIMO Systems Using Reconfigurable Antennas

We present a novel class of space time trellis codes based on super quasi-orthogonal space time codes for a reconfigurable antenna system. We call them space time state trellis codes (STSTCs). We design for 4 trellis states and both 2 and 4 branch trellis structures for BPSK and QPSK constellations. The proposed codes take advantage of the additional degrees of diversity offered by reconfigurable antennas and changing propagation states. They achieve full rate, full diversity and high coding gain. Simulation results demonstrate their good performance. STSTCs achieve the diversity order expected of four transmit antennas while using only two reconfigurable transmit antennas. Our code out performs the existing super orthogonal space time trellis code, which fails to achieve full diversity in a reconfigurable antenna system. The proposed 4 trellis state STSTC is designed based on the following performance criteria: minimum coding gain distance of the minimum return path (CGD MRP), performance factor (PF), rank of the partial valid path (RPVP) on top of traditional minimum coding gain distance of parallel path (CGD PP). We show through analysis and simulations that minimum CGD PP is not a sufficient criteria and that additional performance gains are provided by considering the CGD MRP.

A Pipeline for Trunk Detection in Trellis Structured Apple Orchards

The ability of robots to meticulously cover large areas while gathering sensor data has widespread applications in precision agriculture. For autonomous operations in orchards, a suitable information management system is required, within which we can gather and process data relating to the state and performance of the crop over time, such as distinct yield count, canopy volume, and crop health. An efficient way to structure an information system is to discretize it to the individual tree, for which tree segmentation/detection is a key component. This paper presents a tree trunk detection pipeline for identifying individual trees in a trellis structured apple orchard, using ground‐based lidar and image data. A coarse observation of trunk candidates is initially made using a Hough transformation on point cloud lidar data. These candidates are projected into the camera images, where pixelwise classification is used to update their likelihood of being a tree trunk. Detection is achieved by using a hidden semi‐Markov model to leverage from contextual information provided by the repetitive structure of an orchard. By repeating this over individual orchard rows, we are able to build a tree map over the farm, which can be either GPS localized or represented topologically by the row and tree number. The pipeline was evaluated at a commercial apple orchard near Melbourne, Australia. Data were collected at different times of year, covering an area of 1.6 ha containing different apple varieties planted on two types of trellis systems: a vertical I‐trellis structure and a Güttingen V‐trellis structure. The results show good trunk detection performance for both apple varieties and trellis structures during the preharvest season (87– accuracy) and near perfect trunk detection performance (99% accuracy) during the flowering season.

Performance Analysis of a Modified MAP Decoder Architecture for Low Power Dissipation

A modified architecture for minimized power dissipation in the maximum a posteriori (MAP) decoder based on clock gating and toggle filtering is proposed in this paper. Log likelihood ratio (LLR) in the trellis structure of the MAP decoder consumes large power. To minimize the power dissipation, toggle-filtering technique is introduced in the LLR unit of MAP decoder and clock-gating approach is introduced in the state metric, branch metric and again in LLR blocks of the MAP decoder. Toggle filter is used to avoid early injection of signals from the state metric and branch metric units. Clock-gating approach is used to keep the idle block in the disabled state. A power dissipation of 53.64 % has been achieved when toggle-filtering technique is applied and 54.4 % when clock-gating technique is applied. Power dissipation of 64.07 % has been achieved for the combined effect of toggle-filtering and clock-gating technique.

Trellis-Extended Codebooks and Successive Phase Adjustment: A Path From LTE-Advanced to FDD Massive MIMO Systems

It is of great interest to develop efficient ways to acquire accurate channel state information (CSI) for frequency division duplexing (FDD) massive multiple-input multiple-output (MIMO) systems for backward compatibility. It is theoretically well known that the codebook size for CSI quantization should be increased as the number of transmit antennas becomes larger, and 3GPP long term evolution (LTE) and LTE-Advanced codebooks also follow this trend. Thus, in massive MIMO, it is hard to apply the conventional approach of using pre-defined vector-quantized codebooks for CSI quantization mainly because of codeword search complexity. In this paper, we propose a trellis-extended codebook (TEC) that can be easily harmonized with current wireless standards such as LTE or LTE-Advanced by extending standardized codebooks designed for 2, 4, or 8 antennas with trellis structures. TEC exploits a Viterbi decoder and convolutional encoder in channel coding as the CSI quantizer and the CSI reconstructer, respectively. By quantizing multiple channel entries simultaneously using standardized codebooks in a state transition of trellis search, TEC can achieve fractional bits per channel entry quantization to have a practical feedback overhead. Thus, TEC can solve both the complexity and the feedback overhead issues of CSI quantization in massive MIMO systems. We also develop trellis-extended successive phase adjustment (TE-SPA) which works as a differential codebook of TEC. This is similar to the dual codebook concept of LTE-Advanced. TE-SPA can reduce CSI quantization error even with lower feedback overhead in temporally correlated channels. Numerical results verify the effectiveness of the proposed schemes in FDD massive MIMO systems.

Novel Joint Detection and Decoding Schemes for TDMR Channels

Two-dimensional magnetic recording (TDMR) relies on advanced signal processing and coding techniques to enable storage of data at higher densities. Various detection and decoding schemes have been proposed in the literature. In this paper, a recently proposed joint detection and decoding scheme known as the joint Viterbi detector decoder (JVDD) is presented for TDMR channels. The JVDD operates on a trellis and attempts to find a sequence in the trellis that belongs to a legal codeword with minimum metric. It does so by using a metric thresholding and parity checking technique over the same trellis structure. The iterative detector/decoder consisting of a soft-output Viterbi algorithm detector and low-density parity check decoder is used as a performance benchmark for the JVDD. In this paper, we perform the comparison with various equalization/detection techniques consisting of: 1) a 1-D general partial response equalization scheme followed by a 1-D-detector as used in today’s Partial Response Maximum Likelihood Detection (PRML) channels; 2) a 2-D equalization scheme that equalizes to a 1-D target [fully equalizing away the intertrack interference (ITI)], followed by a series of parallel 1-D-detectors to handle the intersymbol interference (ISI); and 3) a 2-D-equalization scheme followed by 2-D detector to combat both ITI and ISI.

Impact of SRS in WDM Systems and Its Mitigation by Maximum Likelihood Sequence Detection

Non linear effects play a major role in hindering the progress of optical communication systems in terms of higher data rates and long haul transmissions. Maximum Likelihood Sequence Detection (MLSD) has been proposed to combat the nonlinear effects in optical channels. The main objective is to extract the original signal from the received signal which is distorted due to the non linear effects arising in the fiber. MLSD is an optimum detector as it uses the Viterbi detection through the Trellis structure. In this paper, the impact of SRS in the transmitted signal and its mitigation by MLSD are analyzed. MLSD is implemented for DWDM systems with 4 and 8 channels and its performance is compared with the direct detection receivers.

High-Throughput Trellis Processor for Multistandard FEC Decoding

Trellis codes, including Low-Density Parity-Check (LDPC), turbo, and convolutional code (CC), are widely adopted in advanced wireless standards to offer high-throughput forward error correction (FEC). Designing a multistandard FEC decoder is of great challenge. In this paper, a trellis application specified instruction-set processor (TASIP) is presented for multistandard trellis decoding. A unified forward-backward recursion kernel with an eight-state parallel trellis structure is proposed. Based on the kernel, a datapath for multialgorithm and a shared memory subsystem are introduced. The flexibility and the compatibility are guaranteed by a programmable decoding flow and the trellis decoding instruction set. Synthesis results show that the area consumption is 2.12 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (65 nm). TASIP provides trimode FEC decoding ability with the throughput of 533, 186, and 225 Mb/s for LDPC, turbo, and 64 states CC under the clock frequency of 200 MHz, which outperforms other trimode proposals both in area efficiency and recursion efficiency. TASIP provides high-throughput decoding for current standards, including 3rd Generation Partnership Project-Long Term Evolution, 802.16e, and 802.11n, with unified architecture and high compatibility.

Peak and Average Power Reduction of OFDM Signals Based on Trellis Shaping with Controllable Region Expansion

Trellis shaping (TS) is an efficient and flexible signal controlling technique based on the trellis structure at the transmitter. It can be used for reducing both average power and peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals. Most studies in the framework of TS have focused on the simple sign-bit shaping, which controls the signal transition with only a single controlling bit per quadrature amplitude modulation (QAM) symbol (or subcarrier). In this paper, we attempt to increase the number of the controlling bits so as to improve the PAPR reduction capability of OFDM signals. The resulting approach, which we refer to as a controllable region expansion, is a novel extension of the conventional TS where the number of the controlling bits per QAM is increased without imposing additional complexity. Through the investigation based on extensive computer simulations using a nonlinear power amplifier (PA) model, it is shown that the proposed extended TS can achieve a better trade-off compared to the conventional sign-bit TS in terms of PAPR reduction capability, PA efficiency, and resulting bit error rate (BER) performance.

Low complexity trellis representations of convolutional codes via sectionalization of the minimal trellis

It has been shown by McEliece and Lin that convolutional codes can be represented by a minimal trellis structure in order to reduce the decoding complexity of the Viterbi algorithm. This trellis module has an irregular structure presenting sections with different number of states. In this paper we present the sectionalization of the minimal trellis module which yields a more compact and regular trellis representation (in terms of maximum number of states and total number of sections) with the same decoding complexity and distance spectrum of the minimal trellis module. We investigate the effects of the trellis sectionalization over the trellis and merge complexity measures. A set of rules are constructed to govern these effects. A list of the most compact sectionalized trellis modules with the same complexities than the minimal module is shown for codes of several rates. We show that various trellis topologies proposed in the literature are specific cases of the sectionalized minimal trellis.

홀로그래픽 저장장치를 위한 2차원 6/8 균형부호의 트렐리스 인코딩

Holographic data storage is a strong contender to become the next-generation data storage method. Its major weaknesses are two-dimensional intersymbol interference between neighboring pixels and interpage interference caused by storing multiple pages in a single volume of hologram. In this paper, we present a trellis encoding scheme of 6/8 balanced modulation code, to address the two weaknesses. The proposed modulation coding scheme captures on characteristics of the balanced code: the scheme relaxes IPI and enables error correction by exploiting the trellis structure. The proposed method showed improved SNR over the conventional 6/8 modulation