基于Kronecker法的MIMO信道模拟及硬件实现

针对多输入多输出（Multiple-Input Multiple-Output,MIMO）无线通信系统,在基于Kronecker 的MIMO信道模型中综合考虑了路径损耗、阴影衰落和多径衰落等因素,实现了基于现场可编程门阵列（Field Programmable Gate Array,FPGA）的MIMO信道模拟器,并分析了硬件设计方案以及MIMO信道模拟的实现方法。实测结果表明,设计的MIMO信道模拟器可以模拟瑞利衰落、莱斯衰落以及阴影衰落等常见的信道衰落类型,能够应用于3GPP、COST-207等标准信道模型的复现。该模拟器可作为无线通信系统研究的测试设备,辅助通信系统研究的算法验证、方案优化以及性能分析。     

基于网络编码的衰落信道频谱感知算法

针对传统认知无线电网络中频谱状态转换频繁和频谱检测时延长的问题,提出基于随机线性网络编码的累积和能量检测频谱感知算法。该算法在主用户信道中引入随机线性网络编码,利用网络编码对频谱的整形作用,使频谱状态转换稀疏,频谱结构更规律化,减小频谱检测时延,提高系统吞吐率。此外,针对传统累积和能量检测算法抗衰落性能差的问题,通过比较该算法在五种衰落信道下的检测时延和吞吐率,研究该算法的抗衰落性能。实验结果表明,在一定的虚警概率下,该算法有效降低了检测时延,提高了吞吐率及抗衰落能力,能够更好地适应复杂的衰落信道环境。     

非频率选择性衰落信道下捕获性能的分析

对基于数字匹配滤波器(DMF)捕获系统在非频率选择性衰落信道下的捕获性能进行了深入讨论，利用状态转移图推导出单次驻留判决方式时平均捕获时间的表达式。对平坦慢衰落信道和快衰落信道下的平均捕获时间进行了数字分析，得出的主要结论是：无论信道是否存在衰落，基于DMF的捕获系统都具有很快的捕获速度；基于DMF的捕获系统在衰落信道下的捕获性能明显要比非衰落信道差；衰落速度越快，平均捕获时间就越长，系统的捕获性能就越差。因此当信道存在非频率选择性衰落时，可以在接收端采用分集接收(比如空间分集)来改善系统的捕获性能。     

同步捕获算法在莱斯衰落信道下的性能分析

跳频同步是跳频通信系统正常工作的重要前提,直接影响其工作性能,快速跳频通信系统实现同步更为困难,针对这个技术困难,提出了FH系统的一种基于双图案的同步捕获方法,运用理论分析并仿真验证了该同步捕获方法在各种衰落信道（其中包括Rayleigh衰落信道、Rician衰落信道、Nakagami-m衰落信道）下的捕获性能。结果表明：不同衰落信道对FFH/BFSK系统的同步捕获性能不同,在相同的同步捕获门限下,处于深度衰落的Nakagami-m衰落信道对捕获性能的影响最为显著,而就同步捕获性能对门限的敏感度而言,Rayleigh衰落信道下的影响最大。     

新的分层系统信道分配算法浅析

本文研究了分层覆盖系统中的信道分配问题.在考虑层闻呼叫溢出、层内信道紧凑复用、提高切换呼叫优先级等因素的基础上,对层间动态信道分配且带层间呼叫溢出的cp-hdca-bo算法做出改进,提出了-种新的动态信道分配算法.仿真结果表明,该算法可有效降低切换呼叫阻塞率.     

基于Kalman滤波的WCDMA上行链路衰落信道跟踪

针对WCDMA上行链路的结构，介绍了一种基于卡尔曼滤波和线性内插的信道跟踪方法。Kalman滤波器通过线性内插所提供的粗略的数据估计值来准确地获得信道参数的LMMSE解，跟踪信道的变化。仿真结果表明该方法能有效跟踪快速衰落信道，改善系统的性能。     

一种低复杂度信道模拟器的设计

针对TD-LTE射频一致性测试系统专项的需求及通用信道模拟器设计周期长、复杂度高的现状,研究了影响无线信道特性的路径损耗、阴影衰落、多径多普勒效应和高斯白噪声等因素,并相应提出了一种新的计算正余弦函数方法和高斯白噪声产生方法。通过信道理论建模、Matlab链路搭建进行模型优化分析以及基于Xilinx公司Virtex-6芯片的模型FPGA实现,得到了一种简单有效的信道模拟器。实验表明,用TD-LTE基带信号作为激励,该信道冲激响应与Matlab理论值误差在2‰之内,且模型不涉及SCM、WINNER等模型天线方向图、多链路等高复杂度模块,说明该信道模拟器具有简便性和可靠性。     

双选信道下的CPM-FMT联合调制

为了提高双选择性衰落信道下滤波多音（FMT）多载波系统的性能,从子载波调制角度出发,提出了一种连续相位调制-滤波多音（CPM-FMT）联合调制方法。该方法首先将比特数据流串并转换后进行CPM映射,接着对映射后的信号进行重组,然后进行FMT调制。在接收端首先将接收的信号进行FMT解调并进行逆重组,然后进行CPM解映射恢复出比特数据流。实验结果表明,CPM-FMT联合调制方法优于传统调制的QPSK-FMT方法,在误码率为10-3时,白噪声信道下性能最大提高了10 dB,时间频率双选择性衰落信道下性能提高了5 dB,同时该方法对多谱勒频偏具有良好的稳健性。这表明CPM-FMT方法能显著提高FMT系统在双选择性衰落信道下的性能,可应用于高速移动环境下的宽带无线传输系统。     

适用于平台摆动模型的HAPS通信系统信道分配算法

针对高空平台(HAPS)遭受平流层横风影响呈现水平摆动现象,引起地面呼叫用户为继续获得可靠服务在蜂窝间来回切换的问题,提出了平台摆动条件下区分用户优先级的信道预留和切换排队相结合的信道分配算法。该算法充分考虑了不同类型用户终端对服务等级的需求,对用户终端进行了优先级区分,且从降低切换失败率的角度,在信道预留基础上对切换呼叫用户进行排队。仿真结果表明,与传统的无优先级切换排队和区分优先级的固定信道预留算法相比,该算法能够显著降低切换掉话率,尤其是高优先级用户的切换掉话率,补偿了因平台运动所导致的系统性能损失。     

相关瑞利衰落信道下空时分组编码性能分析

目前对空时编码的研究大都是基于信道是独立的假设下进行的,然而在实际系统中独立性假设是不成立的。基于此,研究了信道的相关性对空时编码性能的影响。计算机仿真结果表明：由于衰落信道的相关性,系统性能有所下降,且系统性能关于相关系数存在“地板效应”,即相关系数小于某一数值时,对系统性能的影响较小;当大于此值时,系统性能就会急剧下降。     

Online channel strategies under different offline channel power structures

This study explores the manufacturer's marketing and pricing strategies for online channel under different offline channel power structures. Through these strategies, the manufacturer sells products through an offline retailer and an e-tailer. The manufacturer decides the cooperation mode with the e-tailer by the reselling or the agency selling mode and the pricing strategy on the basis of the power structures, i.e., vertical Nash structure (VN), manufacturer Stackelberg structure (MS), and retailer Stackelberg structure (RS). We find the manufacturer selects the online agency selling mode when the commission rate is less than the given threshold. As long as the commission rate is more than another threshold, the manufacturer selects the online reselling mode under the VN structure; however, the manufacturer selects the online agency selling mode under the other two structures. As well, the offline wholesale price is higher under the MS structure than those under the VN and RS structures. When the manufacturer selects the online agency selling mode, the offline retail price is highest under the MS structure, and the online retail price is highest under the VN structure. Meanwhile, consumers can always obtain a higher surplus in the online agency selling mode under all offline power structures.     

营销渠道冲突分析

所用的营销渠道都存在着潜在的渠道冲突,营销渠道冲突的类型、产生原因及解决办法.     

广告专业频道——数字电视时代的新选择

数字电视的出现深刻地影响了中国电视媒体的格局,电视媒体如何顺应这种发展趋势是值得探讨的问题。国家广电总局在2003年公布的《广播电视有线数字付费频道业务管理暂行办法(试行)》明确规定:付费频道节目应符合专业化、对象化的要求,专业性、对象性节目的     

On manufacturers complementing the traditional retail channel with a direct online channel

With the explosion of the Internet and the reach that it affords, many manufacturers have complemented their existing retail channels with an online channel, which allows them to sell directly to their consumers. Interestingly, there is a significant variation within product categories in manufacturer's use of the Internet as a direct distribution channel. The main objective of this study is to examine the strategic forces that may influence the manufacturer's decision to complement the retail channel with a direct online channel. In particular, we are interested in answering the following questions:

1. Why is it that in some markets only a few firms find it optimal to complement their retail channels with a direct Internet channel while other firms do not?
2. What strategic role (if any), does the direct Internet channel serve and how do market characteristics impact this role?

To address these issues we develop a model with a single strategic manufacturer serving a market through a single strategic retailer. In addition to the focal manufacturer's product the retailer carries products of competing manufacturers. Consumers in this market are one of two types. They are either brand loyal or store loyal. The retailer sets the retail price and the level of retail support, which impact the demand for the manufacturer's product. The retailer's decisions in turn depend on the wholesale price as well as the Internet price of the product if the manufacturer decides to complement the retail channel with an online channel. Our analysis reveals that the optimality of complementing the retail channel with an online channel and the role served by the latter depends critically upon the level of support that the retailer allocates to the manufacturer's product in the absence of the online channel. The level of support allocated by the retailer, in the absence of the online channel, depends upon the retail margins on the manufacturer's product relative to that on rival products in the product category. When the size of the brand loyal segment is small relative to the size of the store loyal segment then in the absence of the online channel, the manufacturer can lower wholesale price and enhance retail support, especially when the retail margins on the rival products are low. In contrast, when the size of the loyal segment is large and the retail margins on rival products are high the manufacturer will find it more profitable to charge a high wholesale price even if that induces the retailer to extend low levels of support. If the manufacturer decides to complement the retail channel with an online channel, some consumers who would have purchased from the retailer might prefer to purchase online. Our analysis reveals that when consumers' sensitivity to price differences across the competing channels exceeds a certain threshold it is not optimal for the manufacturer to complement the retail channel with an online channel. However, this price sensitivity threshold itself depends upon product/market characteristics, suggesting that manufacturers seeking to complement their retail channels with an online channel should look beyond the nature of threat the online channel poses to the retail channel in devising their optimal distribution strategies. When the retail margins on rival products are sufficiently small, complementing the retail channel with an online channel when optimal allows the manufacturer to price discriminate and enhance profits. In contrast when retail margins on rival products are sufficiently high, complementing the retail channel with an online channel serves to enhance retail support. We also identify market conditions under which profits of both the manufacturer and the retailer are greater with the online channel than that without it. This is particularly interesting since the online channel competes with the retail channel.     

Information and channel profits

New marketing information technologies, associated with point-of-purchase scanner systems, have increased the potential information available to manufacturers and retailers. In this paper, we explore the pricing and profit implications of this technology within a channel setting. We find that improved information about demand always results in greater absolute profits, as well as a claim on greater division of channel profits for the informed channel member. The greater profitability is due to the informed channel member's ability to “fine tune” prices in response to changes in demand conditions. However, total channel profits are highest when only one channel member acquires information. We also show that fine-tuning of price has the effect of smoothing sales, as informed firms charge higher prices during high demand periods and charge lower prices during low demand periods. Lastly, we show that an equilibrium where both channel members acquire information does not lead to a prisoners' dilemma.     

Retail channel price discrimination

This paper examines price differentials of identical items across retail channels. Many consumer packaged goods are sold through both grocery and drug stores. Liquor is unique in that in much of the country there is a third retail channel of distribution, liquor stores. If consumers in each retail channel differ in their willingness to pay for certain items, then sellers can exploit those differences and charge different prices for the same items in each channel. We examine a unique data set of pooled cross sectional retail scanner data on wine to test whether sellers use retail channel to identify heterogeneous consumer market segments and engage in price discrimination. We begin by presenting a model of price discrimination by retail channel along with behavioural assumptions regarding shoppers in each channel. Next we examine sales by retail channel and find persistent price differentials for the same item across retail channel after controlling for sample selection bias and seasonality. Lastly, we estimate the price elasticity of demand correcting for endogeneity and find differences across channel consistent with the price differentials. The extent of price differential, however, differs significantly with respect to price point.     

英雄感染力 频道影响力——重庆卫视即将启动《剧风尚 英雄志》大型系列电视活动

一年前，重庆卫视在北京成功举行“2006-2007中国剧风尚盛典”，并现场颁发中国剧风尚编剧、风尚音乐、风尚颠覆作品、风尚颠覆人物、风尚视觉等20多个奖项。那个春季，重庆卫视经过一系列排兵布阵，在全国卫视排名徘徊在第三到第五名，这样一台晚会用颠覆性的手段第一次盘点和展望中国电视剧的发展，嵌入强烈的时尚符号，同时也让重庆卫视在影响力排名上一举树立了自己的江湖地位。     

广东流通怎么"通"?

广东流通产业毛病颇多说起广东的零售业,形式颇多,小至几十平方米的便利店,大至15—16万平方米,集购、食、娱、游于一体的购物中心,中间还包括百货商店、超级市场、大型综合超市、专卖店、专业店、仓储式商店以     

一种新的MIMO信道模型

实际无线通信环境中发送天线之间以及接收天线之间存在相关性。针对以上特点,从 多径MIMO信道的特性出发,首先建立发射天线相关系数矩阵和接收天线相关系数矩阵,并将 它们引入无线信道的莱斯MIMO信道模型中。最后通过分析LOS MIMO信道相关模型和瑞利衰落 MIMO信道相关模型,给出了具体的建模步骤。仿真结果表明采用本文方法产生的信道模型的 MIMO系统误码率更低,从而验证了该信道模型能够较好地模拟MIMO系统的空间信道。