Utilizing Space-Time Diversity for Wireless Communications

In this paper we consider the use of multiple antennas for wireless communication over fading channels.The fading we consider is quasi-static flat Rayleigh fading. For such a scenario optimal SNR schemes are derived when the transmitter knows the channel and when the transmitter does not know the channel. But in both cases the receiver has to estimate the channel. When the SNR during channel estimation is reasonably high we derive expressions to show the impact of channel estimation errors on SNR.     

动态频谱接入中的侦测与避让技术

动态频谱接入技术对频谱实行动态管理,允许未授权用户在无干扰的情况下使用已授权用户的闲置频带,是解决现今无线频谱资源紧缺和利用率低等难题的有效途径,已成为无线通信领域的研究热点。本文介绍了动态频谱接入的侦测与避让方法,分析和讨论了各自的优缺点,并指出动态频谱接入需要进一步研究的问题和可能的发展方向。     

MIMO检测技术在LTE系统中的应用研究

随着移动通信的发展,新一代移动通信标准LTE对传输速率和系统容量等提出了更高的要求,这就需要采用更先进的技术来实现更高的传输速率和更好的传输质量。多输入多输出（MIMO,MultipleInputMultipleOutput）技术就是实现高速传输,提高传输质量的重要途径。本文对MIM0检测技术在LTE系统中的应用进行了分析与研究。     

IMT—2000固定无线接入技术及其应用

根据宽带接入的技术要求,在分析ＩＭＴ－２０００／ＦＷＡ技术特点的基础上,探讨它在未来宽带接入网中的两种应用方案及其在信令接口、业务质量、网络管理等方面的相关问题。     

虚拟专用网络技术

对ＶＰＮ的基本概念作简要介绍后,着重分析了ＶＰＮ的三种典型的应用方式,即Ｉｎｔｒａｎｅｔ ＶＰＮ,远程接入ＶＰＮ和Ｅｘｔｒａｎｅｔ ＶＰＮ,并对现有的一些ＶＰＮ技术进行了总结,提出了一个一般的ＶＰＮ体系结构模型。     

V5接口技术综述

本文对Ｖ５接口技术的各个方面作了较为详尽的论述,包括Ｖ５接口的起源、基本概念、协议、工作过程、网管、实现方法、技术指标、标准、现状及发展中的宽带Ｖ５接口等十个方面的内容。     

时隙式随机争用多址系统分析方法研究

本文给出一种新的平均周期分析方法,并对时隙式随机争用多址系统进行了分析,得到了系统的信息分组发送成功的平均长度公式、信息分组发生碰撞的平均长度公式和空闲时隙的平均长度公式,并在讨论了系统的冲突分解特性后,给出了系统的吞吐量。     

Layered Access Control Schemes on Watermarked Scalable Media

Intellectual Property (IP) protection is a critical element in multimedia transmission and delivery systems. Conventional IP protection on multimedia data can be categorized into encryption and watermarking. In this paper, a structure to perform layered access control on scalable media by combining encryption and robust watermarking is proposed, implemented, and verified. By taking advantages of the nature of both encryption and watermarking, copyrights of multimedia contents can be well protected and at the same time, multiple-grade services can be provided. In the summated examples, we assume a scalable transmission scheme over the broadcasting environment and use it to test the effectiveness of proposed method. When the embedded watermark is extracted with high confidence, the key to decrypt the next layer can be perfectly recovered. Then, the media contents are reconstructed and the copyrights are assured. The application examples also demonstrate the practicality of the proposed system.

Throughput and delay analysis of multi-channel wireless infrastructure networks

Wireless infrastructure networks (WINs) provide ubiquitous connectivity to mobile nodes in metro areas. The nodes in such backbone networks are often equipped with multiple transceivers to allow for concurrent transmissions in multiple orthogonal channels. In this study, we develop an analytical model for the estimation of the delay and throughput performance of wireless infrastructure networks employing slotted ALOHA channel access and slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) over multiple channels. The analytical model, which takes into account the correlation due to multi-hop transmissions, approximates the performance observed through simulations accurately.     

侧墙技术在相变存储器中的应用

从相变存储器(phase change random access memory,PCRAM)的基本结构和工作原理出发,首先介绍了PCRAM的技术优势、面临的技术挑战、常用的解决策略以及存在的相应问题;接着阐述了在微电子加工中广泛应用的关键工艺——侧墙技术,并将其在PCRAM中的应用成果进行了分类;然后从加热电极的制备、相变材料限制结构的制备、新相变材料的制备与表征和器件间互联等4个方面展开叙述;最后展望了该技术在相变存储领域应用发展的趋势。侧墙技术因其具备自对准的特点,制备工艺可控性好,制备精度不依赖于光刻精度,在纳米技术飞速发展的今天,侧墙技术将会在更高精度上发挥其作用。