基于梳状导频的OFDM分组自适应比特装载与功率控制

无线通信环境中信道信息(ChannelStateInformation,CSI)随时间变化明显,需要不断地更新自适应比特装载和功率控制的策略。现有的OFDM自适应比特装载方法需要大量的信令来传递当前比特装载的策略,不适用于无线通信的应用环境。为此,本文针对OFDM系统的特征提出了一种利用插入梳状导频的信道估计得到的带有误差的信道信息,来完成自适应比特装载的算法。首先把OFDM子载波进行分组,然后利用基于梳状导频的信道估计对信道时变进行跟踪,使用即时获得的CS完成自适应比特装载算法。仿真实验证明,在保证算法简单、实用及保证要求的误码率(BER)性能的情况下,信道信令的开销低于传统算法的10%。     

联合信道均衡与时间反演的室内保密通信方法

针对物理层无线通信的窃听信道问题,提出了一种适用于室内频率选择性衰落信道的均衡时间反演(Equalized Time Reversal,ETR)保密通信方法。首先,建立了均衡时间反演窃听模型,在信号发送端将均衡器级联配置,利用信道均衡技术提高信息传输的保密性能;其次,通过传统时间反演(Time Reversal,TR)技术的等效信道分析对均衡器进行了设计,根据均衡后的信道推导了系统保密信干噪比、系统保密容量、误码率的闭合表达式。理论分析和仿真结果表明,与传统的TR技术相比,ETR的保密信干噪比、系统保密容量更高,合法接收用户的误码率更低。     

一种利用信源冗余的Turbo均衡新算法

为克服无线衰落信道中严重的符号间干扰(ISI)的影响,提出了一种新的利用信源冗余的Turbo均衡算法。该算法将联合信源信道译码技术与Turbo均衡技术结合起来,在均衡、译码、信源之间建立起软信息交互的环路,有效提高了整体接收的性能。外信息传递(EXIT)图分析与计算机仿真均表明,尽管信源冗余给译码器带来的性能提升较为有限,但是将这部分信息反馈回均衡器后,在严重ISI信道,信源冗余度为70%时,整体接收的性能改善约为9.5 dB,基本达到了理想加性高斯白噪声（AWGN）信道下的误码性能。     

HSDPA技术特性研究及其对WCDMA网络的影响分析

HSDPA是一些无线增强技术的集合．利用HSDPA技术可以在现有的技术的基础上使下行数据峰值速率有很大的提高。HSDPA通过自适应调制编码、多码传输、快速和有效的重传机制替代R99版本中物理信道使用的变SF和快速功率控制技术。运营商在WCDMA网络中增加HSDPA可以增加扇区的吞吐量并降低用户的延时,这些改善有助于运营商拓展新的应用业务。首先阐述了HSDPA的概念．然后研究了HSDPA包含的各项关键技术．最后详细分析了HSDPA的引入对WCDMA网络结构和网络性能的影响．验证了HSDPA技术的优势和重要性。     

基于最小均方误差的8PSK解调算法

在EDGE(Enhanced Data Rate for GSM Evolution)移动通信系统中,提出了一种基于最小均 方误差的自适应8PSK均衡解调算法。 利用基于最小均方误差的自适应滤波器,根据突发中已知的训练序列,可快速准确地估计出 系统信道参数,然后通过判决反馈均衡消除多径信道对接收信号的干扰,从而保证系统的性 能。仿真结果表明,在各种多径信道模型下,该算法均可快速收敛,利用系统的26个训练序 列准确估计出系统信道参数,并实现均衡和解调;在信噪比为8～10 dB时,通过标准规 定 的MCS-5信道编解码后,系统的误码率就已经小于10－4,完全符合标准要求 ,是一种简单实用的算法,便于硬件实现。     

消费者失望厌恶行为对时尚零售商数量承诺的影响

理性预期均衡(REE)策略和数量承诺(QC)是时尚零售商经常实施的两种降价销售策略,零售商在REE策略下公布产品的库存,在QC下不公布产品库存,而策略型消费者在两种策略下可能延迟至降价期才购买产品。在降价期存在缺货风险,策略型消费者预期在降价期购买不到产品会感到失望,反之亦然。在失望对效用的影响大于欣喜对效用的影响时,策略型消费者是失望厌恶的。QC在失望厌恶水平低于临界值时优于REE策略,在失望厌恶水平高于临界值时与REE策略一致。     

频率选择性信道下Turbo码和SC-FDE的联合方案

针对频率选择性信道下宽带数据传输存在符号间干扰(ISI),提出了一种频率选择性 信道下联合Turbo码和单载波频域均衡（SC-FDE）的宽带传输方案。通过改进传统SC-FDE结 构,设计了一种SC-FDE软信息提取方法,提高了进入Turbo码译码器先验信息的精确性,从 而改善了系统整体性能。仿真结果表明,相比较于硬信息输出,采用SC-FDE软信息输 出能够改善输出信噪比,提高系统性能。     

短波SC-FDE系统中改进的LS信道估计算法

针对短波单载波频域均衡(SC-FDE)系统中最小二乘(LS)信道估计算法受噪声影响大而导致的估计精度低的问题,提出了一种改进的基于小波去噪的LS信道估计算法。改进算法采用基于分块导频的帧结构,首先用LS算法对信道进行初步估计,然后根据小波多分辨率分析(Mallat)理论将LS估计的结果分解,并设置一个合理阈值对分解得到的小波系数处理,从而消除LS估计的残留噪声,提高估计精度。仿真结果表明,在短波信道下,改进算法不仅减小了系统开销,而且提高了LS估计的性能。     

基于“农超对接”模式的质量改进与公平偏好研究

通过构建"农超对接"模式下的Stackelberg博弈模型,本文以农户无公平偏好无质量改进情形下供应链均衡策略为参照,对比研究了农户无公平偏好有质量改进和有公平偏好有质量改进对供应链均衡策略变化的影响。研究表明,为了激励农户进行农产品质量改进,超市主动承担了一部分质量改进的成本,但并不是其承担的比例越大越好;当超市分担质量改进成本比例较小时,超市效用会随着公平偏好系数增大而减小,超市效用在公平偏好足够大时会小于无质量改进情形,而农户和供应链整体的效用却随着公平偏好系数增大而增大,并且远远大于无质量改进情形。     

OFDM系统中载波间干扰抑制方法

在高速移动通信环境下,OFDM系统在传输过程中出现的多普勒频移和收发两端本地振荡器之间的频率偏差,形成子载波间干扰(ICI)并造成系统性能降低。在分析子载波间干扰机制的基础上,讨论了自消除方法和分段均衡方法,并提出一种利用加窗技术改进的分段均衡方法。仿真结果表明,采用该改进的分段均衡方法能更好地改善系统的性能,有约2 dB的信道估计增益。     

无线基带信道模型Chaotic-Map误码特性分析

介绍了一种新的基于混沌映射的基带信道模型,即Chaotic-Map模型。对此模型的意义和用法进行了详细描述,研究了该模型中参数取值与信道特性的对应关系,并且通过仿真验证了该模型对具有突发误码特性的无线信道的适应性。     

Consumer response to marketing channels: A demand-based approach

Abstract

Marketing channels have faced rapid structural and functional transformations during the last few decades. While a large body of research has been devoted to understanding the supply-side aspects of marketing channels, much less research has taken the demand-side perspective to study consumer perception of channel position and functions. This article extends the channel literature to a broader domain and develops a consumer-based theoretical framework reflecting factors that influence consumer perception of and reaction to channel strategies and decisions. The authors conceptualize that consumers’ perceived channel value is a critical factor in determining their loyalty behavior. Seven important channel features are identified that would positively influence the perceived channel value. The relationship between perceived channel value and channel preference is strongly dependent on the level of customer value co-creation. The article concludes with research implications and suggestions of avenues for future research.     

移动平台对无线信道特性的影响分析

针对移动平台对无线信道特性的影响,在分析移动多径信道特性的基础上,建立了不同信道模型下多普勒效应的计算机仿真模型。不仅针对不同信道衰落条件下平台移动引起的多普勒效应进行仿真,而且为进一步阐述多普勒效应的影响,还对平台移动引起的数字通信误码率进行了仿真。信真结果表明,平台移动不但会扩展多普勒频谱,而且会加快信道衰落,造成误码率上升。     

Equilibrium in supply chain network with competition and service level between channels considering consumers' channel preferences

This paper considers a dual-channel supply chain network consisting of multiple competing manufacturers, multiple competing retailers and multiple demand markets. Each manufacturer produces and distributes his products via direct e-commerce channel along with traditional physical channel. The manufacturers also provide services for the consumers in both channels, while the retailers only offer offline services to the consumers. On this basis, a dual-channel supply chain network equilibrium model with pricing and service decisions are established based on variational inequality theory. Nash equilibrium solutions are obtained by modified projection and contraction method. Combined with numerical examples, we analyze the impact of three critical factors on the equilibrium states and profits. Some interesting managerial insights are derived. We find that the profits of the manufacturers decrease (increase) in the raw material conversion ratio under single channel case (dual-channel case), while the increase of the raw material conversion ratio always benefits the retailers and the whole dual-channel supply chain network; the service level in each channel is positively correlated with its transaction volume. There are significant inconsistencies among the best combinations of cross-channel price coefficients between two channels for the manufacturers, the retailers and the whole dual-channel supply chain network. The same equilibrium decision (service level, price) or profit may exhibit the opposite changing trend with respect to cross-channel price coefficients under two cases of active e-commerce transaction and inactive e-commerce transaction. When the introduction of e-commerce channel can bring more profits for the whole dual-channel supply chain network, the manufacturers should provide reasonable allocation schemes of profit increment for the retailers to satisfy their participation constraints.     

移动通信中无线信道特性的研究

从等效低通信道的时变冲激响应的相关函数和功率密度谱函数出发，研究了一些描述广义平稳非相关散射(WSSUS)的无线信道特性的统计参数，并对无线移动衰落信道的特性进行分类。分析了3种常见的小尺度多径衰落信道的统计模型，给出了在平坦衰落信道中系统传输比特误码率的一般分析方法。最后，利用这些模型和方法，给出了一些常见数字调制信号的传输误码率的数值结果。结果表明：衰落对无线移动通信系统传输性能的影响是很大的，在实际中应设法消除它。     

Managing International Distribution Channel Partners: A Cross-Cultural Approach

Although the topic of conflict has been extensively studied in the distribution channels literature from a domestic perspective, there is relatively little published research examining the construct within the international distribution channels context. This is of particular concern because cross-national channel partnerships are on the rise, and divergent cultures may engender heightened conflict, which has a deleterious effect on channel performance. This article explores the extent to which different channel leadership styles, predicated on Hofstede's dimensions of national culture, can be effective strategies to manage conflict in international distribution channels. Specifically, the article examines whether the relationship between leadership style and conflict in international distribution channels is moderated by national culture. Additionally, the impact of manifest conflict on international channel partner performance is investigated. A conceptual model and research propositions are developed. The use of leadership styles to manage disagreements among international channel partners is argued to be culturally specific. International channel management implications and directions for future research are suggested.     

Determination of Export Channel Strategies–The Experience of New Zealand Firms

ABSTRACT

There are many issues which need to be considered when businesses decide to internationalise their operations. One of the issues is the choice of export channels. The choice of export channels has a decisive impact on a firm's international marketing program. Export channel decisions are well researched in many countries However little attention has been made to investigate the choice of export channels by New Zealand international marketers This study examines the factors influencing the choice of export channels of 115 New Zealand firms conducting business with Taiwan. The results suggest that marketer's choice of export channels is influenced by the host market's business system, market size of the industry in the host market, and the degree of produce differentiation. The host market's business system is revealed for the first time to be a factor influencing the choice of export channels.     

Will Online Shopping Compete More with Traditional Retailing or Catalog Shopping?

This paper examines consumer substitution behavior among three distribution channels: online shopping, traditional retail and catalog shopping. A model of consumer transactions costs is presented in which consumer investments in shopping human capital determine distribution channel choice. This model predicts that consumers who make investments that spillover to multiple channels will tend to have lower transactions costs for those two channels and will tend to consider these two channels to be closer substitutes than other channels. The model implies that, even if these investments are not measured, they will represent a component of the regression models' residual terms, which will predict distribution channel choice. I test this implication using the GVU Center's survey data on channel selection for various product categories. The results strongly suggest that consumers consider online shopping and catalog shopping to be closer substitutes than any other pair of channels.     

Experimental analysis of consumer channel-mix use

Today's consumers have access to multiple consumer distribution channels. To remain competitive, retailers must offer different contact points to consumers. This empirical study examines channel-mix use decisions for 352 online customers' holiday booking preparations. A scenario based experimental approach studies consumer channel-mix use by channel and decision context attributes. The study models effects of time pressure, expected expenditure, channel quality, and access costs on the use of eight channel options, including traditional and online options. Over one-half of respondents use multiple channels to decide trip booking; however, most travelers book trips using the channel they initially investigated for information. Results show expected expenditure does not influence channel use; however, overall cost affects the booking's timing. Time pressures force respondents to visit a travel agent or collect additional brochures to quickly complete the purchase. Results suggest brochures fulfill an important support role.     

基于共赢理念的双渠道冲突管理研究

网络技术和电子商务的发展使很多制造企业不仅通过传统零售渠道分销产品,而且通过网络渠道直接向消费者销售产品。双渠道策略的实施在实现网络渠道与传统渠道优势互补的同时,也引发了渠道冲突。双渠道环境下的渠道冲突可分为外部冲突和内部冲突。外部冲突和内部冲突会相互影响,相互转化。有效管理企业内外部渠道冲突以求得整个渠道系统利益的最大化,对双渠道运营的企业来说既是机会又是挑战。文章通过构造制造商和传统零售商的博弈模型,分析、比较模型中的局中人赢得,认为可通过模型中部分变量的选择来实现双渠道环境下制造商和传统零售商的共赢。双渠道环境下,对制造商而言,应对外部和内部渠道冲突实施不同的管理策略,对外部渠道冲突进行有效区隔,对内部渠道冲突增进企业内部渠道组织之间的沟通和协调;对传统零售商而言,应直面制造商采用网上直销渠道的现状,争取更大的销售折扣,增加销量,降低成本。