Security issues for downloaded code in mobile phones

'Software defined radio' (SDR) is a technology that will appear in future generations of mobile phones, i.e. following the third-generation mobile phone technology that is currently being defined and developed. Early versions of 'pragmatic' SDR will allow the terminal to be reconfigured at any level of its protocol stack. Ultimately, the 'pure' SDR technology will allow a mobile phone or terminal to have its air interface software configured or reconfigured by other software (or software parameters) that have been downloaded to the terminal, e.g. over the air, or from a remote server via the Internet and one's personal computer (PC). A number of security issues arise with downloaded code that implements the air interface functions, and these may not be obvious simply from looking at the way PC software is updated on-line today. This paper starts with an outline of the code that allows a mobile phone to operate over a particular air interface. This sets the baseline for a discussion of the security issues surrounding the change of this code from one that is fixed and downloaded once only, to code that is reconfigurable during the life of a product.     

利用框架理论对信号进行重建

在Hilbert空间中讨论了框架的一些重要的性质,定义了一个框架算子,并讨论了该算子的性质。根据实际问题构造了一框架,使信号在此框架下的投影正好为非均匀采样值。给出了一种框架界的估计方法和重建原信号的迭代算法,最后,用仿真验证了此算法的有效性。     

H.248协议在UMTS核心网中的应用

描述了H.248协议的连接模型和消息结构,分析了H.248协议在UMTS核心网中的实现方案,并给出了一个应用实例,最后探讨了实现中可能面对的问题和解决方案。     

软交换网络中媒体网关控制器的研究与设计

300万像素对于专业摄影来说可能不值一提，但是对于家庭用户而言却已经十分完美了。下面三款数码相机是300万家庭中令人兴奋的新品，它们的价格都在3000元到4000元人民币之间，想想一年前3000万像素的相机要花多少钱？而在测试中它们的表现也的确让人觉得物有所值。     

定向棱镜腔平顶高斯激光束特性的研究

在XeCl准分子激光器中,采用定向棱镜作为端反射镜与平面输出镜构成激光器谐振腔,获得了近场能量分布均匀、远场能量分布高度集中的相干平顶高斯激光束输出,并具有腔镜高抗失调能力,改善了激光束质量。     

Reliability prediction models to support conceptual design

During the early stages of conceptual design, the ability to predict reliability is very limited. Without a prototype to test in a lab environment or without field data, component failure rates and system reliability performance are usually unknown. A popular method for early reliability prediction is to develop a computer model for the system. However, most of these models are extremely specific to an individual system or industry. This paper presents three general procedures (using both simulation and analytic solution techniques) for predicting system reliability and average mission cost. The procedures consider both known and unknown failure rates and component-level and subsystem-level analyzes. The estimates are based on the number of series subsystems and redundant (active or stand-by) components for each subsystem. The result is a set of approaches that engineers can use to predict system reliability early in the system-design process. Software was developed (and is discussed in this paper) that facilitates the application of the simulation-based techniques. For the specific type of system and mission addressed in this paper, the analytic approach is superior to the simulation-based prediction models. However, all three approaches are presented for two reasons: (1) to convey the development process involved with building these prediction tools; and (2) the simulation-based approaches are of greater value as the research is extended to consider more complex systems and scenarios     

铁路电力试验车软件的设计与实现

介绍了铁路电力试验车软件的设计思想、框架结构及其总体控制策略 ,并就其中的测试程序、数据库管理系统、串口通讯程序、复杂式样报表生成和系统安装程序的设计策略作了叙述。     

激光晶体Nd:YVO4的形貌及生长缺陷

本文报道了应用环境扫描电镜（ESEM）和同步辐射X射线白光形貌术对采用提拉法生长出的Nd:YVO4晶体进行的形貌及生长缺陷的分析,获得了该晶体的开裂表面的ESEM形貌像以及取自晶体肩部和中间部位的（001）面的同步辐射白光形貌像,观察到了位错、包裹物等缺陷,可为生长高质量的Nd:YVO4晶体提供重要的启示.     

Oracle9i数据库安全管理机制剖析

数据库安全和数据安全机制是数据库开发设计者目前必须考虑的问题之一。Oracle9i数据库管理系统在数据库安全方面为数据库管理员和应用开发者提供了很好的安全机制。文章从不同侧面和角度讨论Oracle9i数据库系统的安全管理机制，为实施更安全更灵活的数据库安全策略提出了全方位的技术思路。