The wireless market has experienced a phenomenal growth since the first second- generation (2G) digital cellular networks, based on global system for mobile communications (GSM) technology, were Introduced in the early 1990s. Since then, GSM has become the dominant global 2G radio access standard. Almost 80% of today’s new subscriptions take place in one of the more than 460 cellular networks that use GSM technology. This growth has taken place simultaneously with the large experienced expansion of access to the Internet and its related multimedia services.
标签： Performance Evolution GPRS EDGE GSM and
上传时间： 2020-05-27
上传用户：shancjb
With the rapid growth of the wireless mobile applications, wireless voice has begun to challenge wireline voice, whereas the desire to access e-mail, surf the Web or download music (e.g., MP3) wirelessly is increasing for wireless data. While second generation (2G) cellular wireless systems, such as cdmaOne1, GSM2 and TDMA3, Introduced digital technology to wireless cellular systems to deal with the increasing demand for wireless applications, there is still the need for more spectrally efficient technologies for two reasons. First, wireless voice capacity is expected to continue to grow. Second, the introduction of high-speed wireless data will require more bandwidth.
标签： Wireless Systems Mobile Beyond and 3G
上传时间： 2020-05-30
上传用户：shancjb
The market for cellular phones and wireless data transmission equipment has changed dramatically since the late 1970s when cellular phones were first Introduced and the late 1980s when wireless data equipment became available. As would be expected, duringthistime RF test requirements and RF test equipment has changed dramatically.
标签： Measurements Cellular Phones for RF
上传时间： 2020-05-31
上传用户：shancjb
When 3GPP started standardizing the IMS a few years ago, most analysts expected the number of IMS deploymentsto grow dramatically as soon the initial IMS specifications were ready (3GPP Release 5 was functionallyfrozenin the first half of 2002and completedshortly after that). While those predictions have proven to be too aggressive owing to a number of upheavals hitting the ICT (Information and Communications Technologies) sector, we are now seeing more and more commercial IMS-based service offerings in the market. At the time of writing (May 2008), there are over 30 commercial IMS networks running live traffic, addingup to over10million IMS users aroundthe world; the IMS is beingdeployedglobally. In addition, there are plenty of ongoing market activities; it is estimated that over 130 IMS contracts have been awarded to all IMS manufacturers. The number of IMS users will grow substantially as these awarded contracts are launched commercially. At the same time, the number of IMS users in presently deployed networks is steadily increasing as new services are Introduced and operators running these networks migrate their non-IMS users to their IMS networks.
标签： Multimedia Subsystem The IMS 3G IP
上传时间： 2020-06-01
上传用户：shancjb
This chapter provides extensive coverage of existing mobile wireless technologies. Much of the emphasis is on the highly anticipated 3G cellular networks and widely deployed wireless local area networks (LANs), as the next-generation smart phones are likely to offer at least these two types of connectivity. Other wireless technologies that either have already been commercialized or are undergoing active research and standardization are Introduced as well. Because standardization plays a crucial role in developing a new technology and a market, throughout the discussion standards organizations and industry forums or consortiums of some technologies are Introduced. In addition, the last section of this chapter presents a list of standards in the wireless arena.
标签： Networking Wireless Complete
上传时间： 2020-06-01
上传用户：shancjb
In the first chapter, the topic of this book is classified into the area of pervasive com- puting. Further, security and privacy in the scope of RFID technology is motivated and the vision that guides the remainder of this book is Introduced.
标签： RFID_Security_and_Privacy_Concept
上传时间： 2020-06-08
上传用户：shancjb
随着科技发展及工业4.0 进程推进,机械臂应用范围越来越广,并演化出各种各样的机械臂,如码垛机械臂、焊接机械臂、装配机械臂以及手术机械臂等。现利用solidworks 进行三维建模,设计制作一款基于stm32f103c8t6 单片机的主从式桌面级机械臂,该机械臂包括一个主动机械臂和一个从动机械臂,采用蓝牙传输信号方式进行同步运动,并且详细介绍了该机械臂材料选择、结构设计、工作原理、组成部分和设计特点。With the development of science and technology and the advancement of Industry 4.0, the application range of the mechanical arm has become wider and wider, and various types of mechanical arms, such as palletizing robot arms, welding robot arms, assembly robot arms, and surgical robot arms, have been developed. Now using solidworks for 3D modeling, design and manufacture a master-slave desktop-level robot arm based on stm32f103c8t6 single-chip microcomputer. The robot arm includes an active robot arm and a slave robot arm, which uses Bluetooth to transmit signals for synchronous motion. The material selection, structural design, working principle, components and design features of the manipulator are Introduced.
标签： stm32f103c8t6 单片机
上传时间： 2022-03-27
上传用户：sheng199241
入室抢劫事件屡见不鲜,针对此现象进行分析不难发现,造成失窃事件的极大原因是人们慵懒和意识差等不良性格造成习惯性不锁门.本文以STC89C52单片机为基础,设计了一种基于人体红外传感器的自动关门锁门装置,来解决此类问题.The incidents of burglary are so common. It is not difficult to find that the main reason for the burglary is the habit of unlocking of doors caused by people's laziness and poor consciousness. Based on the single chip microcomputer of STC89C52, a device used with infrared sensor of human body is Introduced in this paper, which can achieve the effect of automatic closing and locking doors.
上传时间： 2022-03-27
上传用户：canderile
本文设计了一种磁致伸缩位移传感器,介绍了该磁致伸缩位移传感器的测量原理,通过结构优化设计提高了仪器的性能,详述了硬件电路设计及实现方法,完成了软件设计,实现了高压充电、问询脉冲加载、时间测量及滤波等功能,并通过实验对其性能进行了验证。所研制的磁致伸缩位移传感器具有测量精度高、长期稳定性好等特点,满足了大量程、高精度、恶劣环境等测量的要求。A kind of sensor based on magnetostrictive principle is designed.The measuring principle of the magnetostrictive displacement sensor is Introduced,the performance of the instrument is improved by the structural optimization design,and Introduced the hardware circuit design and the realization method,completed the software design,realized the functions of the high voltage charging,inquiries pulse loading,time measurement and filtering,and its performance is verified through the experiment.The magnetostrictive displacement sensor has the characteristics of high measuring precision.The sensor meets the requirements of large range,high precision,poor environment and so on.
标签： 位移传感器
上传时间： 2022-04-06
上传用户：hai7ying
为适应双向DC/DC功率变换的电流采样需求,一种高精度高边电流采样电路被提出。其基本思想是在功率电路的高边串入采样电阻,借助电流镜原理并引入偏置电流电路,将双向电流均转换为正向电压输出。通过理论分析与仿真结合的方法对电流镜采样原理及4种不同的偏置电流电路方案进行对比,最后通过实验数据验证了高精度高边电流采样电路的有效性。实验数据表明,该采样电路可在-25~75℃的温度工作范围内,针对-10~＋10 A范围内的电流采样实现优于5%的采样精度。Current sensing plays an important role in controlling,monitoring or protection functions of power systems.To meet the current sensing requirement of bidirectional DC/DC converters,a high-accuracy bidirectional current sensing circuit is proposed.The proposed current sensing circuit inserts a resistor in the path of the current to be sensed,while the current mirror and biased current circuit are Introduced.Therefore,the bidirectional current can be expressed by positive voltage.By theoretical analysis and simulation,the sampling theory is analyzed and four biased current circuits are compared.At last,experimental results verified the proposed method.It is demonstrated that the proposed current sensing circuit can achi...
上传时间： 2022-04-22
上传用户：sheng199241
