SM协议在GPRS网络监测中的研究与实现

介绍了SM协议及GPRS网络测试仪中SM协议监测模块的基本概念和功能。监测功能包括消息解析、核心参数提取、利用关键参数进行呼叫合成及对合成结果进行统计分析处理4个环节。其中消息的解析又包含消息数据详细解析与合成信息数据提取解析2个部分,故需要重点说明SM协议监测模块消息结构,并在此基础上研究SM协议的详细解码和基础解码、CDR合成技术、实时统计分析等。现场测试保证了数据的真实性和相关理论方法的有效可行性。     

SMT在大规模生产中的应用

以松下ＨＤ８２录象机单板的大规模生产过程为范例，分析探讨了ＳＭＴ工艺在大规模生产中应该注意的几个问题和工艺要点，并提出了解决方法和应对措施。对ＳＭＴ技术实际生产中的应用有一定的参考价值。     

Outage probability bound of decode and forward two‐way full‐duplex relay employing spatial modulation over cascaded α − μ channels

The system performance of mobile‐to‐mobile (D2D) cooperative communication has been improved by utilizing spatial modulation (SM) in this paper. The proposed system employs decode and forward (DF) relaying technique along with physical layer network coding (PLNC); hence, it has been named as SM‐based decode and forward two‐way relay (DFTWR). It enables full‐duplex communication thereby enhancing the system efficiency. Information bits are exchanged between the two bidirectional nodes. For two bits of information exchange, the antenna index is conveyed by the least significant bit (LSB) of the data symbol while the most significant bit (MSB) carries the message. The system performance has been investigated by analyzing certain performance metrics like lower and upper bounds of outage probability and average data rate for N‐α‐μ cascaded fading channels. The change in the system performance by varying certain parameters like relative geometrical gain, fading coefficients, and number of cascaded components has also been put forth in this paper.     

Design and implementation of UMTS session management in the user equipment

In universal mobile telecommunications system (UMTS), session management (SM) maintains a communication session between a user equipment (UE) and the core network. 3GPP TS 24.008 specifies the SM functions and the communication protocols between the UE and the core network. However, the interaction between the SM and other entities in the UE are not specified in detail. This paper designs and implements the SM software. We use a finite state machine (FSM) to model the SM functions. Based on the FSM and the primitives, we describe how to set up the development steps to implement the SM at the UE. Copyright © 2006 John Wiley & Sons, Ltd.     

不锈钢PC型单模光纤活动连接器

本文介绍不锈钢PC型单模光纤活动连接器的设计及制造。它的插针体采用不锈钢材料,其端面加工成凸球面形。该连接器插入损耗典型值为0.3dB,回波损耗大于35dB,抗反射性能强,特别适用于大容量、超高速数字传输、宽频带图象模拟传输及本地网(LAN)等光纤通信系统。     

基于SM4轮函数设计的认证加密算法

认证加密算法,作为一种对称密码算法,能够同时保护数据的机密性和完整性,在信息安全领域有着重要作用.现有的认证加密算法大多是基于分组密码的工作模式设计的,底层需要调用全轮的分组密码,效率受到很大限制.本文主要考虑从基本部件出发直接设计一个高效的认证加密算法.首先结合国产分组密码标准SM4与广义Feistel结构给出了一种通用的结构设计.然后以抵抗碰撞攻击为安全性目标,利用混合整数规划（MILP）方法搜索得到了一些状态大小和效率各不相同的结构,这些结构可以被用来构造消息认证码和认证加密算法.最后,利用目前搜索得到的状态大小和效率较优的结构设计了一个认证加密算法,并进行了初步的安全性分析和软件实现,其速度约为SM4-GCM速度的10倍.     

Improved preimage and pseudo-collision attacks on SM3 hash function

A preimage attack on 32-step SM3 hash function and a pseudo-collision attack on 33-step SM3 hash function respectively were shown.32-step preimage attack was based on the differential meet-in-the-middle and biclique technique,while the previously known best preimage attack on SM3 was only 30-step.The 33-step pseudo-collision attack was constructed by using the same techniques.The preimage attack on 32-step SM3 can be computed with a complexity of 2^254.5,and a memory of 2⁵.Furthermore,The pseudo-preimage and pseudo-collision attacks on 33-step SM3 by extending the differential characteristic of the 32-step preimage attack were present.The pseudo-collision attack on 33-step SM3 can be computed with a complexity of 2^126.7,and a memory of 2³.     

天线布局对于MIMO可见光通信的影响

针对多输入多输出(MIMO)的室内可见光 通信(VLC)系统,通过改变发光二极管(LED)及 光接收机的空间分布,分析了天线布局对于系统性能的影响。VLC系统采用基于朗伯辐射 的信道模型, 使用常见的重复编码(RC)、空间复用(SMP)和空间调制(SM)3种MIMO技术,分析了两 种系统。第1种为4×6系统,即发射端的4个LED采用正方形布局,光接收机的6个探测器采用正六边形、 矩形和三角 形布局。仿真结果表明,在室内中心处,对于RC,三角形布局的误码率(BE R)性能最好;对于SMP和SM,正六边形和三角形的性能相近,且优于矩形布 局。在室内非中心处,正六边形是3种技术的最优选 择。第2种为8×8系统,LED和光检测器分别采用正八边形、正方形布局。仿真结果表明, 发送端采用正方形布局时系统性能较好。     

Decreased oxygen saturation in asymmetrically prominent cortical veins in patients with cerebral ischemic stroke

Decreased oxygen saturation in asymmetrically prominent cortical veins (APCV) seen in ischemic stroke has been hypothesized to correlate with an increase of de-oxygenated hemoglobin. Our goal is to quantify magnetic susceptibility to define APCV by establishing a cutoff above which the deoxyhemoglobin levels are considered abnormal. A retrospective study was conducted on 26 patients with acute ischemic stroke in one cerebral hemisphere that exhibited APCV with 30 age- and sex-matched healthy controls. Quantitative susceptibility mapping (QSM) was used to calculate the magnetic susceptibility of the cortical veins. A paired t-test was used to compare the susceptibility of the cortical veins in the left and right hemispheres for healthy controls as well as in the contralateral hemisphere for stroke patients with APCV. The change in oxygen saturation in the APCV relative to the contralateral side was calculated after thresholding the susceptibility using the mean plus two standard deviations of the contralateral side for each individual. The thresholded susceptibility value of the APCVs in the stroke hemisphere was 254 ± 48 ppb which was significantly higher (p < 0.05) than that in the contralateral hemisphere (123 ± 12 ppb) and in healthy controls (125 ± 8 ppb). There was a decrease of oxygen saturation in the APCV ranging from 16% to 44% relative to the veins of the contralateral hemisphere. In conclusion, APCV seen in SWI correspond to reduced levels of oxygen saturation and these abnormal veins can be identified using a susceptibility threshold on the QSM data.     

自适应多天线技术

多天线技术有多种实现模式,不同的实现模式有不同的特点和应用场景。文章首先介绍了波束赋形(BF)、循环延迟分集(CDD)、空间分集(SD)、空间复用(SM)等各种多天线技术实现模式的原理。进而分析了各种多天线模式的技术特征以及他们适合的应用场景。基于这些分析,文章提出了一种多天线模式自适应切换算法,他能根据应用场景或者无线信道特征,自适应地选择最优的多天线模式来发送数据,从而进一步发挥多天线技术的优势。