在衰落移动信道中图象传输的神经网络译码方法

我们采用（２,１,３）卷积码,仿真和讨论了标准图象通过具有四种不同调制方式和两种不同车速的八个移动信道的神经网络译码器性能,并且研究了在移动信道中卷积码快衰落特征对图象传输可靠性的影响和纠错性能。我们得到一些重要的结果和提出一些移动通信系统中图象传输的建议。     

块交错方案在移动图像通信系统中的应用

提出了一种适合于卷积码的新的交错方案块交错方案,并对采用块交错方案的(2,1,3)卷积码在移动图像通信系统中的抗干扰性能进行了计算机模拟,且与周期交错方案的结果做了比较.模拟结果表明周期交错方案不适合于卷积码,而采用块交错方案的(2,1,3)卷积码可明显改善图像质量,大大提高了快衰落移动信道环境中图像通信系统的可靠性.     

一种面向移动无线信道的混沌交织算法

交织是抵抗移动无线衰落信道突发差错的有效技术.为了抵抗二维突发差错,提出了一种新的基于Baker映射的混沌交织算法.该算法首先将二进制信源序列转化为数据矩阵,再使用混沌Baker映射方法将其随机离散化,从而实现二维长突发差错在解交织后变为一维短突发差错.再者,将该算法和基于Viterbi解码的卷积码联合使用,分别应用于(2,1,3)和(2,1,7)两种卷积码场景下进行性能比较.仿真结果显示,当移动信道传输图像画面时,该算法相比传统方案具有显著优势;该算法的抗衰落性能随着分组长度的增加而更加优越,并且有效降低了算法复杂度;该算法通过使用不同的密钥能够增强每个传输分组的安全性.     

移动信道下采用Punctured卷积码实现不等错误保护的研究

本文以移动信道的四状态Markov模型为基础,将Punctured卷积码(Punctured Convolutional Codes;PCC)用于快衰落移动信道下的图像传输系统中, 提出了通过对码率、母码约束长度和交织度这三种不同自由度的调整,实现图像传输的不等错误保护(Unequal Error Protection;UEP)方案.计算机模拟结果表明,所提出的方案具有明显的不等错误保护能力,可以满足在具有不等错误保护要求的移动环境下对传输图像质量的要求.     

卷积码和Turbo码在视频传输中的性能比较

提出改进的数字视频传输方案和移动信道模型,分析卷积码和Ｔｒｕｂｏ码在不同调制方式的性能仿真结果,得出在ＡＷＧＮ和衰落信道上传输ＤＶＢ信号时编码方案。     

（2,1,3）,（2,1,5）卷积码在典型快衰落移动信道中的纠错性能

本文介绍一种在用三状态Ｍａｒｋｏｖ模型表示的典型移动信道上运行的（２，１，３）和（２，１，５）卷积码纠错抗干扰的性能，模拟完成了一个卷积码编码（Ｔｒｅｌｉｓ结构）、加错、Ｖｉｔｅｒｂｉ译码的全过程。并将（２，１，３）、（２，１，５）卷积码在ＢＳＣ和典型移动信道中的纠错抗干扰性能进行了比较，得出了一些有意义的结论。     

基于Simulink的平坦瑞利衰落信道的建模与性能分析

该文利用Simulink建立了平坦瑞利衰落信道仿真模型,分别给出无信道编码和有信道编码两种情况下的建模仿真与性能。信道编码采用卷积码,译码算法采用Viterbi译码。仿真结果表明:在无信道编码情况下,由于深度衰落的影响,平坦瑞利衰落信道的误码性能与信噪比成线性关系,这与理论分析结果相一致。而基于卷积码的平坦瑞利衰落信道的性能在高信噪比有明显改善,但低信噪比改善有限。同时,仿真中给出不同的约束长度的卷积码,仿真表明卷积码的约束长度越长性能越好。     

卷积码的编码及其Viterbi译码的计算机模拟

本文对差错控制中卷积码的编码及其用Viterbi算法译码进行了计算机模拟,然后,根据计算机模拟数字声音广播移动接收信道所产生的差错序列,把卷积码进行了比特交错,模拟了几组参数变化对性能改善的影响。     

移动数据传输的差错控制

无线电信道中存在衰落、干扰等多种因素，导致数据传输性能恶化，如何在移动信道中实现可靠而有效的通信值得关注。 差错控制 差错控制方案有三类，正向纠错（ＦＥＣ）、检错加自动重发（ＡＲＱ）及混合纠错（ＨＥＣ）。其中ＦＥＣ有循环码（或者称为块码）及卷积码两大类。ＡＲＱ有停止／等待，退Ｎ步与选择重发三种。ＨＥＣ综合了ＦＥＣ及ＡＲＱ两种方式。纠错码的选择与其所应用的场合是密切相关的。 由于移动信道是时变、非线性信道，专家在研究了移动信道数据传输的性能后，得出了不同条件下的差错图样的分布情况，但不管如何，信道的…     

Punctured卷积码在HDTV信号传输中的应用

基于Punctured卷积码的特点 ,本文分析了其在HDTV(High -DefinitionTV)信号传输中的应用 ,分别在AWGN信道和Rayleigh衰落信道下将Punctured卷积码用于静态图像传输 ,通过计算机仿真给出了其性能分析并与RS码进行了比较。     

JPEG image transmission over mobile network with an efficient channel coding and interleaving

This article studies improving of coloured JPEG image transmission over mobile wireless personal area network through the Bluetooth networks. This article uses many types of enhanced data rate and asynchronous connectionless packets. It presents a proposed chaotic interleaving technique for improving a transmission of coloured images over burst error environment through merging it with error control scheme. The computational complexity of the used different error control schemes is considered. A comparison study between different scenarios of the image transmission is held in to choose an effective technique. The simulation experiments are carried over the correlated fading channel using the widely accepted Jakes’ model. Our experiments reveal that the proposed chaotic interleaving technique enhances quality of the received coloured image. Our simulation results show that the convolutional codes with longer constraint length are effective if its complexity is ignored. It reveals also that the standard error control scheme of old Bluetooth versions is ineffective in the case of coloured image transmission over mobile Bluetooth network. Finally, the proposed scenarios of the standard error control scheme with the chaotic interleaver perform better than the convolutional codes with reducing the complexity.     

一种改进的噪声图像语义分割方法

在图像的获取和传输过程中,可能会出现噪声, 它不仅破坏了图像的真实信息,而且严重影响了图像的视觉效果。因此, 噪声图像的语义分割成为图像分析中最具挑战性的问题之一。为了提高噪声图像的分割性能 ,本文在分析全卷积网络(FCN)的 基础上,提出一种改进的FCN模型(IFCN)对噪声图像语义分割。该算法采用一种新的中值 池化方法代替卷积神经网络的最大值 池化,可以在去除噪声的同时保留更多边缘信息。在训练整个深度网络时,通过反向传播算 法以一种直接的端到端,像素到像素 的方式映射。实验结果表明,提出的模型在PASCAL VOC2012数据集上对噪声图像语义分割 可以获得比较好的分割效果,准确率mean IU达到86.5%。     

Forward Error Correction Coding for Fading Compensation in Mobile Satellite Channels

Fading in mobile satellite communications severely degrades the performance of data transmission. The channel is modeled with nonfrequency selective Rice and Rayleigh fading. Also, stored channel simulation is used for hardware data transmission. FEC coding with Viterbi decoding of convolutional codes, and Berlekamp-Massey decoding of Reed-Solomon codes, are used to compensate for the fading. In addition to interleaving, channel state and erasure information improve the performance of the decoder. The BER after decoding is calculated for specific codes on several channels and for different transmission schemes. Using very simple channel state and erasure information gives 2-7 dB additional coding gain. These gains have been verified by hardware data transmission on synthetic fading channels and stored mobile satellite channels.     

Medical image transmission over a GSM cellular system

This authors report on an investigation of possible source/channel coders for medical image transmission over a GSM cellular link. Two source coders (JPEG and EZW) and two channel coders (convolutional and turbo codes) are used. Analysis of the results indicates that EZW with convolutional coding gives the best performance, but some kind of automatic repeat on request (ARQ) is also needed     

Multi-scale convolutional attention network for lightweight image super-resolution

Convolutional neural network (CNN) based methods have recently achieved extraordinary performance in single image super-resolution (SISR) tasks. However, most existing CNN-based approaches increase the model’s depth by stacking massive kernel convolutions, bringing expensive computational costs and limiting their application in mobile devices with limited resources. Furthermore, large kernel convolutions are rarely used in lightweight super-resolution designs. To alleviate the above problems, we propose a multi-scale convolutional attention network (MCAN), a lightweight and efficient network for SISR. Specifically, a multi-scale convolutional attention (MCA) is designed to aggregate the spatial information of different large receptive fields. Since the contextual information of the image has a strong local correlation, we design a local feature enhancement unit (LFEU) to further enhance the local feature extraction. Extensive experimental results illustrate that our proposed MCAN can achieve better performance with lower model complexity compared with other state-of-the-art lightweight methods.     

Performance of H.263 video transmission over wireless channelsusing hybrid ARQ

This paper proposes a hybrid ARQ error control scheme based on the concatenation of a Reed-Solomon (RS) code and a rate compatible punctured convolutional (RCPC) code for low-bit-rate video transmission over wireless channels. The concatenated hybrid ARQ scheme we propose combines the advantages of both type-I and type-II hybrid ARQ schemes. Certain error correction capability is provided in each (re)transmitted packet, and the information can be recovered from each transmission or retransmission alone if the errors are within the error correction capability (similar to type-I hybrid ARQ). The retransmitted packet contains redundancy bits which, when combined with the previous transmission, result in a more powerful RS/convolutional concatenated code to recover information if error correction fails for the individual transmissions (similar to type-II hybrid ARQ). Bit-error rate (BER) or signal-to-noise ratio (SNR) of a radio channel changes over time due to mobile movement and fading. The channel quality at any instant depends on the previous channel conditions. For the accurate analysis of the performance of the hybrid ARQ scheme, we use a multistate Markov chain (MSMC) to model the radio channel at the data packet level. We propose a method to partition the range of the received SNR into a set of states for constructing the model so that the difference between the error rate of the real radio channel and that of the MSMC model is minimized. Based on the model, we analyze the performance of the concatenated hybrid ARQ scheme. The results give valuable insight into the effects of the error protection capability in each packet, the mobile speed, and the number of retransmissions. Finally, the transmission of H.263 coded video over a wireless channel with error protection provided by the concatenated hybrid ARQ scheme is studied by means of simulations     

Joint source and channel coding using turbo codes over rings

Turbo codes are a practical solution for achieving large coding gains. We present a new turbo coding scheme where the component codes are convolutional codes (CCs) over the ring of integers modulo M, with M being the alphabet size of the source encoder. The a priori knowledge of the source statistics is used during the iterative decoding procedure for improved decoder performance. As an example of application, we examine differential pulse code modulation (DPCM) encoded image transmission