LT码新型度分布及其在电力线通信中的应用

Luby变换(Luby Transform,LT)码作为信道编码应用于电力线通信(Power Line Communication,PLC)，可实现电信号的可靠传输。度分布对LT码编译码性能的影响至关重要。为了得到更优的度分布，首先调整二进制指数分布(Binary Exponential Distribution,BED)中的度数比例，获得一种译码性能更优的改进的二进制指数分布(Improved BED,IBED)。然后，根据IBED在冗余度较小时译码成功率高，而冗余度增大后鲁棒孤子分布(Robust Soliton Distribution,RSD)的译码性能表现更佳的特点，通过求和归一化的方式将IBED与RSD两种度分布的优势进行有机结合，提出一种新型二进制鲁棒孤子分布(Binary RSD,BRSD)。仿真结果表明，与其他方法及传统的RSD相比，采用新度分布进行LT编码，可明显降低译码开销，并节约编译码耗时。将新型度分布应用于基于LT码的PLC系统中，能有效地抑制PLC信道中各种噪声对电信号的干扰，并提高通信效率。     

Inconvenience cost of mobile communication failure: The case of South Korea

Mobile communication failure can occur when mobile traffic exceeds the manageable level. This depends on frequency bandwidth. Mobile communication failure causes inconveniences in a user's daily life that lead to social and economic damage. To address this issue, mobile telecommunications companies deploy additional bandwidths and develop new technologies, but these are costly strategies. This study applies a spike model based on a contingent valuation method (CVM) to measure the inconvenience cost resulting from mobile communication failure. The mean monthly willingness-to-pay (WTP) to avoid communication failure per user is estimated to be KRW 898.14 (USD 0.80) over a period of five years in our study. The inconvenience cost borne by the population is estimated to be KRW 2.97 trillion (USD 2.61 billion). Users experiencing greater frequency of communication failure are found to be willing to pay more to avoid the inconvenience. When excluding respondents citing zero-WTP, the mean WTP per user was calculated to be KRW 3426.41 (USD 3.01). Data traffic usage and frequency at which communication failure is experienced are variables that exhibit statistically significant effects on WTP to avoid mobile communication failure. Overall, estimation results show that a price discrimination based on data traffic usage or quality can be considered by mobile telecommunications companies and regulators to address the issue of data traffic inducing mobile communication failure.     

An empirical examination of the effects of design elements of email newsletters on consumers’ email responses and their purchase

In this research, we empirically explore the effects of various design elements of email newsletters on consumers' email responses and their purchases. We capture the consumers' email responses using three metrics, namely email open, email click, and email reopen. We operationalize consumers' purchases as their spending on product items that are featured in email newsletters. Using a novel email marketing database, first, we model the influence of design elements of email newsletter on consumers' email responses at the individual consumer level. The email design elements constitute several email attributes, situational factors, and integrated marketing communication. Second, we quantify the effects of these three email responses, open, click, and reopen, on consumers' purchases. Our empirical results suggest a significant influence of email attributes, situational factors, and marketing communications on consumers' email responses. Furthermore, among open, click, and reopen, we find clicks tend to have the highest impact on consumers’ purchase, followed by email reopening and opening. However, email newsletters with higher opening probability are more effective in influencing purchases than those email newsletters with higher reopening probability. Furthermore, consumers who indulge in all three email responses, namely opening, clicking, and reopening, tend to purchase the most. Results from our study offer several critical insights for email marketing strategy helping managers improving the effectiveness of email campaigns by careful consideration for the design elements of email newsletters.     

Seeing history: a visual assessment of the historic-grounding of Old Western tourist towns

Despite the significant role that the visual plays in the experience of tourism, few studies have specifically examined the visual appearances of heritage tourist destinations. This study sought to analyze how historically grounded the visual appearances were of two heritage tourist towns in the state of Arizona: Tombstone and Jerome. These towns were both mining towns that experienced historic booms during the days of the American Old West and survive today as tourist destinations. This study utilized a detailed visual comparison of historic and contemporary town photographs in order to assess the relative historic-grounding of building exteriors and streets. It also incorporated the findings of interviews with tourists and town residents regarding their perceptions of visual historic-grounding. Study findings offered a means to assess and compare visual historic-grounding. Additionally, they suggested that while visual historic-grounding was important to visitors, it was one of several factors influencing their perceptions of the town's historic appearance: visual appeal, personal reflections, engaging activities, and previous visitor expectations of the American Old West (often grounded in filmic-representations) worked together to visually communicate a general impression of history within each town.     

基于信息辅助块稀疏贝叶斯学习的直扩通信窄带干扰抑制

现有基于Nyquist-Shannon采样定理的窄带干扰(Narrowband Interference,NBI)抑制方法存在应用受限于采样率较高的问题。应用压缩感知(Compressive Sensing,CS)理论解决上述问题，利用NBI在频域表现出的块稀疏特性以及直接序列扩频(Direct Sequence Spread Spectrum,DSSS)信号的类噪声特性，提出了基于块稀疏贝叶斯学习(Block Sparse Bayesian Learning,BSBL)框架的DSSS通信NBI抑制模型。实现干扰抑制后，利用传统的CS重构算法实现DSSS信号的压缩域解调。为进一步提高算法性能，将NBI稀疏分块的块内自相关矩阵建模为单位矩阵，提出了信息辅助BSBL(Aid BSBL,ABSBL)算法，设计了基于ABSBL的DSSS通信NBI抑制算法。该算法在保持较好NBI抑制性能的条件下，提高了运算效率并且不依赖NBI的稀疏结构。仿真验证和对比分析结果表明，所提方法能够有效抑制DSSS通信中的NBI，在干扰强度相同的条件下，NBI带宽越小、压缩率越大，算法对NBI的抑制性能越好。     

利用双正交小波变换优化G3-PLC系统性能

为了提高G3-PLC(G3-Power Line Communication)在复杂信道环境下通信的可靠性，提出了基于双正交小波变换的正交频分复用（Discrete Wavelet Transform-Orthogonal Frequency Division Multiplexing,DWT-OFDM）。通过双正交小波变换减小复杂信道环境下G3-PLC通信系统中OFDM载波间干扰，并通过合理减少循环前缀，优化传输效率，降低峰均比。在DWT-OFDM的G3-PLC系统中，通过不同小波基性能分析与对比，利用bior6.8双正交小波基进行系统性能优化。将DWT-OFDM的G3-PLC系统在实际电力线噪声库环境下进行实验分析，仿真结果表明，在平均误码率为10-3量级时，性能有5 dB左右提升，通信效率由40%提高至54%；结合限幅法，峰均比由11 dB降低至8 dB，通信性能极大优于基于FFT-OFDM的G3-PLC系统。     

基于卷积神经网络自编码器结构的空时分组传输方案

为提高现有端到端通信系统的泛化能力和可靠性，提出了一种基于卷积神经网络的空时分组码（Space-Time Block Coding，STBC）多输入多输出通信系统物理层方案。该方案将通信系统物理层表述、调制和解调过程联合起来形成端到端自编码器系统，引入多层一维卷积层，分别构建发射机和接收机，并扩展为多天线模式。为进一步提高系统可靠性，合理规划网络结构和参数，联合信号的调制和编码方案，优化了系统模型。仿真实验表明，针对瑞利相关衰落下多输入多输出（Multiple-Input Multiple-Output，MIMO）信道应用场景，训练模型可以实现传统STBC系统的误码性能，两发两收系统在发送端相关系数为0和0.9时分别优于传统系统0.5 dB和1 dB。此外，经过优化后的系统可获得采用卷积编码的性能改善效果，其两发两收不同工作方式优于传统1/2码率卷积编码STBC系统1~3 dB。     

微纳卫星组网星间链路设计及关键技术分析

微纳卫星组网应用可大幅度提高航天装备的能力，较单颗大卫星具有明显的优势。首先，介绍了国内外微纳卫星组网的研究情况，以组网侦察应用为例分析了星间测量与通信链路的技术需求，并进行了系统架构和体制设计；其次，在星座设计基础上开展系统仿真，并提出了一体化设备实现方案；最后，分析了微纳卫星组网系统中几项重要的关键技术及其解决方案，对系统的设计和工程实现具有参考价值。     

变革中多渠道信息传递对员工绩效的影响机制

面对日趋复杂的外部环境,组织变革成为企业获得竞争力的重要方式。员工参与是组织变革成败的关键,充足的组织变革信息有利于员工积极投入变革。本文以社会信息加工理论为基础,对来自被兼并企业的36个工作团队185名员工进行研究,探索多渠道变革信息传递对员工的影响机制。基于多层次线性模型的数据分析结果表明:(1)变革情境下,组织正式渠道进行信息沟通和变革氛围包含的非正式信息,均能正向促进员工变革绩效;(2)员工所持有的积极变革期望,在多渠道信息传递和变革绩效间起到中介作用;(3)变革氛围跨层调节变革信息沟通对员工积极变革期望的正向作用,相比于低变革氛围情景,具有高变革氛围的团队,通过变革信息沟通更能显著提升员工对变革的积极期望。研究结论对企业变革实践中信息传递和沟通工作具有现实指导意义。