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.
標簽： Performance Evolution GPRS EDGE GSM and
上傳時間： 2020-05-27
上傳用戶：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.
標簽： Wireless Systems Mobile Beyond and 3G
上傳時間： 2020-05-30
上傳用戶：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.
標簽： Measurements Cellular Phones for RF
上傳時間： 2020-06-01
上傳用戶：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.
標簽： Multimedia Subsystem The IMS 3G IP
上傳時間： 2020-06-01
上傳用戶：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.
標簽： Networking Wireless Complete
上傳時間： 2020-06-01
上傳用戶：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.
標簽： RFID_Security_and_Privacy_Concept
上傳時間： 2020-06-08
上傳用戶：shancjb
隨著科技發展及工業4.0 進程推進,機械臂應用范圍越來越廣,并演化出各種各樣的機械臂,如碼垛機械臂、焊接機械臂、裝配機械臂以及手術機械臂等。現利用solidworks 進行三維建模,設計制作一款基于stm32f103c8t6 單片機的主從式桌面級機械臂,該機械臂包括一個主動機械臂和一個從動機械臂,采用藍牙傳輸信號方式進行同步運動,并且詳細介紹了該機械臂材料選擇、結構設計、工作原理、組成部分和設計特點。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.
標簽： stm32f103c8t6 單片機
上傳時間： 2022-03-27
上傳用戶：
入室搶劫事件屢見不鮮,針對此現象進行分析不難發現,造成失竊事件的極大原因是人們慵懶和意識差等不良性格造成習慣性不鎖門.本文以STC89C52單片機為基礎,設計了一種基于人體紅外傳感器的自動關門鎖門裝置,來解決此類問題.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.
上傳時間： 2022-03-27
上傳用戶：canderile
本文設計了一種磁致伸縮位移傳感器,介紹了該磁致伸縮位移傳感器的測量原理,通過結構優化設計提高了儀器的性能,詳述了硬件電路設計及實現方法,完成了軟件設計,實現了高壓充電、問詢脈沖加載、時間測量及濾波等功能,并通過實驗對其性能進行了驗證。所研制的磁致伸縮位移傳感器具有測量精度高、長期穩定性好等特點,滿足了大量程、高精度、惡劣環境等測量的要求。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.
標簽： 位移傳感器
上傳時間： 2022-04-06
上傳用戶：
為適應雙向DC/DC功率變換的電流采樣需求,一種高精度高邊電流采樣電路被提出。其基本思想是在功率電路的高邊串入采樣電阻,借助電流鏡原理并引入偏置電流電路,將雙向電流均轉換為正向電壓輸出。通過理論分析與仿真結合的方法對電流鏡采樣原理及4種不同的偏置電流電路方案進行對比,最后通過實驗數據驗證了高精度高邊電流采樣電路的有效性。實驗數據表明,該采樣電路可在-25~75℃的溫度工作范圍內,針對-10~＋10 A范圍內的電流采樣實現優于5%的采樣精度。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...
上傳時間： 2022-04-22
上傳用戶：
