中速数据数字调制解调器终端设备

本文介绍日本电气公司（NEC）的最新中速数据（IDR）数字调制器和解调器设备，中速数据数字调制调解终端的配置及与其相关的1：N备份切换和监迭单元；这些设备都符合现有的INTELSAT规范IESS－308）修订版4。     

FSK数字调制解调器的应用

在数字信息技术高速发展的今天,快捷、安全、高速的信息传输,一直是信息高速公路发展的题中之义.自商业计算机逐渐普及以来,使数据传输速率也因为频移键控技术的飞跃发展越来越快.而运用FSK,这一数字频移键控技术,使调制解调器在数据传输的应用方向大大拓展.     

视音频信号同线传输调制解调器

视频切换开关在电视系统中应用非常广泛。视频切换开关目前有两种形式 ,一种是普通的视频切换开关 ,结构简单 ,但日后升级困难 ,不能进行远程控制 ,价格便宜。另一种是计算机控制的切换开关 ,今后更新换代方便 ,能进行远程控制 ,输入端和输出端可随意组合 ,而且可以编程控制 ,目前 ,多媒体计算机内视频卡开关只是视频开关 ,不能同时进行视音频的同步切换。为了能同时切换视音频信号。我们研制了视音频信号同线传输的调制器和解调器。1调制解调器的原理视音频同线传输调制和解调器的原理及系统部分的框图 ,如图 1所示。音频信号经预加重电路…     

家庭网络的网关技术

叙述了家庭网关在家庭网络中所起的作用及其三个发展阶段，讨论了专用网关应该具备的功能，介绍了近期宣布与演示的相关产品。     

ADSL调制解调器的测试

全球固定网络电话用户线已超过8亿,我国今年1月份的统计数字是1.5亿.全球移动电话用户也超过5亿,我国今年一月份的统计数字是9千万.目前美国仍在电话总用户数方面稳居首位,我国暂居第二位.     

个人网关的研究与实现

本文介绍了一个全新的概念：个人网关（PG：Personal Gateway)。它可以克服以往IP电话的种种缺陷,为个人用户提供单独的一路IP语音服务,而且使用户在上网的同时也可通过话机方便地拨打和接听电视。本文着重讨论了个人网关的设计思想、原理、体系结构、应用环境和前景。     

短波数字调制解调器

本文以短波数字通信为背景，着重分析了在慢、非选择性衰落信道中数据传输的误码率，针对中、低速数据传输提出了一种较好的调制方式：GMSK调制，并给出了GMSK调制方式在功率谱密度、已调波占用带宽和邻道干扰三个方面的特性，最后介绍了具体的实现方案。     

Consumer Devices for eCommerce Access

It is widely predicted that electronic commerce will have a far-reaching impact on businesses in the next few years. For this to occur it will be essential that users are able to access and use eCommerce services when and where they wish, at times and places that are convenient to them. It is likely that increasingly many of the access devices used will not be standard desktop PCs. In this paper the range of potential devices that could in future be used to access eCommerce services is considered, and some of the issues in supporting this diverse range of devices are examined.     

通过USB接口实现对1394设备的访问

文章介绍了USB和1394两种接口之间通过同步方式传输数据包的原理，以及在传输过程中如何实现两种不同格式的数据包进行转换的方法。     

Android设备获取web服务端验证码技术的研究

传统的使用session记录验证码的方法存在缺陷:如果客户端无法使用cookie,则无法正确的进行验证。故文章提出了一种通过Mysql数据库来记录验证码的方法。首先web服务器收到客户端索要验证码的请求后发送验证码,并将验证码和请求中的标识符作为一组数据通过JDBC(Java Data Base Connectivity)记录在Mysql数据库中。然后等web服务器收到客户端提交的验证码后,依照提交请求中的标识符到Mysql数据库中找到对应的验证码,拿此验证码和提交的验证码进行匹配。测试结果表明:此方法有效地解决了使用session记录用户信息的弊端,而且还具有数据保存时间灵活,数据方便于管理,服务器内存占用减少的优点。     

Dynamic Resource Allocation of Random Access for MTC Devices

In a long term evolution‐advanced (LTE‐A) system, the traffic overload of machine type communication devices is a challenge because too many devices attempt to access a base station (BS) simultaneously in a short period of time. We discuss the challenge of the gap between the theoretical maximum throughput and the actual throughput. A gap occurs when the BS cannot change the number of preambles for a random access channel (RACH) until multiple numbers of RACHs are completed. In addition, a preamble partition approach is proposed in this paper that uses two groups of preambles to reduce this gap. A performance evaluation shows that the proposed approach increases the average throughput. For 100,000 devices in a cell, the throughput is increased by 29.7% to 114.4% and 23.0% to 91.3% with uniform and Beta‐distributed arrivals of devices, respectively.     

A Composite Circuit Model for NDR Devices in Random Access Memory Cells

Devices exhibiting negative differential resistance (NDR), such as resonant tunneling diodes and Esaki-type diodes, offer the promise of converting a dynamic random access memory (DRAM) cell to operate like a static random access memory cell with potentially lower dynamic power dissipation and faster read and write operations than a conventional DRAM. However, a circuit model that describes the operation of the resulting novel memory cell and is of use for both hand analysis and design, and circuit simulation as has yet been developed due to the non-analytical current-voltage curve of the two NDR devices in the cell. In this paper, a "composite" circuit model is presented that describes the relationship between current and voltage at the common node of connection of the two NDR devices. The composite model is analytical and can easily be implemented in SPICE or any circuit simulator. It is also useful for hand analysis of the read/write performance metrics. Finally, comparisons of composite models are presented     

肖特基器件用重掺As衬底上外延层过渡区控制

掺As衬底外延片很大部分用于肖特基器件,器件对正向压降要求越来越高,因此对外延层参数之一的过渡区宽度提出了更高要求.讨论了影响过渡区的温度、生长速率、本征CAP层以及赶气等因素.通过一系列实验,找到了合理的生长条件,得到了完美的过渡区,解决了器件反向电压和正向压降之间的矛盾.在反向电压一致的条件下,正向压降平均降低了200 mV,产品整体成品率提高了两个百分点以上.研究结果已成功应用于大规模生产中.     

无铅器件逆向转化有铅器件工艺

通过对有铅焊料与无铅器件混用的工艺性问题与质量问题进行分析,论述了无铅器件逆向转化为有铅器件的必要性;介绍了无铅器件焊端材料以及对逆向转化工艺的影响;提出并重点论述了有引线无铅器件、无引线无铅器件和球形焊端无铅器件逆向转化为有铅器件的工艺方法.     

Key Establishment and Pairing Management Protocol for Downloadable Conditional Access System Host Devices

In this paper, we investigate the possible security threats to downloadable conditional access system (DCAS) host devices. We then propose a DCAS secure micro (SM) and transport processor (TP) security protocol that counters identified security threats using a secure key establishment and pairing management scheme. The proposed protocol not only resists disclosed SM ID and TP ID threats and indirect connection between TA and TP threats, but also meets some desirable security attributes such as known key secrecy, perfect forward secrecy, key compromised impersonation, unknown key‐share, and key control.     

Authentication-based Access Control and Data Exchanging Mechanism of IoT Devices in Fog Computing Environment

The emergence of fog computing has witnessed a big role in initiating secure communication amongst users. Fog computing poses the ability to perform analysis, processing, and storage for a set of Internet of Things (IoT) devices. Several IoT solutions are devised by utilizing the fog nodes to alleviate IoT devices from complex computation and heavy processing. This paper proposes an authentication scheme using fog nodes to manage IoT devices by providing security without considering a trusted third party. The proposed authentication scheme employed the benefits of fog node deployment. The authentication scheme using fog node offers reliable verification between the data owners and the requester without depending on the third party users. The proposed authentication scheme using fog nodes effectively solved the problems of a single point of failure in the storage system and offers many benefits by increasing the throughput and reducing the cost. The proposed scheme considers several entities, like end-users, IoT devices, fog nodes, and smart contracts, which help to administrate the authentication using access policies. The proposed authentication scheme using fog node provided superior results than other methods with minimal memory value of 4009.083 KB, minimal time of 76.915 s, and maximal Packet delivery ratio (PDR) of 76.