可在单片机上实现的语音混沌保密通信方法

针对目前数字混沌保密方法中计算量大的不足,提出了一种可在单片机上实现的改进混沌保密方法,并将该方法用于数字语音混沌保密通信。分析了该方法中运用整数运算代替浮点运算降低计算量的原理与过程,着重说明了改进的混沌算法在单片机上的实现。最后,在AT89C51单片机上成功进行了数字语音的混沌保密通信实验并取得了令人满意的结果。     

卫星测控站射频接收系统EMC设计与测试

本文以卫星测控站为例,介绍了卫星测控站和卫星通信地面站接收系统EMC的设计与测试方法,并给出了测试结果。     

MT—2B2B一种新型线路码的研究

本文以三角波为传输波变形，以差分双相码为基础提出了一种新型的线路码－MT－2B2B。文章描述了码的构成，计算了码的频谱结构，分析了码的特点。码对于高速近距离基带传输系统具有较大的实用价值。     

随机均衡器的计算机辅助最优化设计

本文提供了一种实用的随机均衡器的计算机辅助设计方法.以二元件均衡器为链接模型,以非线性最小二乘法为最优化方式,解决了多节均衡器链接中初始参数值的选取问题.讨论了0.618法在非单一极值区间的应用.并且通过实例计算说明这一方法的有效性和实用性.     

On the Performance of TETRA Short Data Service-Transport Layer

This paper presents the results of an extensive measurement survey on the performance of Short Data Service Transport Layer (SDS-TL) of Terrestrial Trunked Radio (TETRA) cellular networks. We developed a novel software measurement platform that runs over the TETRA Peripheral Equipment Interface (PEI), generates SDS-TL traffic, performs measurements, and presents statistics of QoS metrics. The measurement platform was utilized in two measurement campaigns: in the first one, two terminals were co-located in the same TETRA cell, and in the second campaign the terminals were positioned in different cells. Measurements were taken for SDS-TL sizes varying from 10 to 190 bytes (excluding the TL header) with an increment of 5 bytes. For each SDS-TL size, 1,500 messages were exchanged through the measurement platform between the TETRA mobile terminals. We repeated all measurements for three intertransmission intervals, namely 2, 1.5, and 1 s, corresponding to measurement durations-for each set of 1,500 SDS-TL- of ≈ 3,000, 2,250 and 1,500 s, respectively. Hence, 166,500 SDS-TL messages were exchanged between two terminals for each measurement campaign. Results obtained include the end-to-end transmission delay (mean and standard deviation) and the percentage of lost SDS-TL versus the message size for the three intertransmission intervals. The effects of inadequate radio capacity as well as gaps in the radiocoverage can be easily identified through the measurement platform, and we analyze such representative cases.     

直接序列扩频系统的多次驻留顺序捕获

本文利用矩阵变换方法对多次驻留顺序捕获的平均捕获时间表示式进行了推导,其过程较信号流图法简单。同时还给出了一次、二次及三次驻留顺序捕获系统的平均捕获时间的计算实例。     

Performance Evaluation of Distributed Database Architectures for UMTS Service Deployed in an Urban Area

The design of distributed databases (DDBs) destined to store user information is a key issue in third-generation mobile communication systems such as UMTS. In particular, the problem of determining the most appropriate DDB architectures for UMTS is critical due to the anticipated requirements of high distribution and adaptability of information. This paper presents a model which allows different DDB architectures to be evaluated, in terms of query loads and average search times. The model proposed puts no constraints on either the DDB structure arrangement or the user position characterization. The paper also discusses a real, significant case study, concerning a query operation arising from an access procedure performed on the DDB of a communication network covering an urban area.     

F—PORT传真存储转发系统

本文介绍了日本ＫＤＤ公司的Ｆ－ＰＯＲＴ传真存储转发系统的构成、工作方式及其功能。     

半导体激光器与新材料

介绍了半导体激光器和半导体光电材料研究的新进展。     

迅速崛起的亚太光纤市场

本文归纳分析出亚太光纤市场的两个显著特点，介绍了亚太地区光通信发展水平，以及亚太各国和地区间的光通信合作，指出亚太光纤市场得以迅速发展的主要原因。