The design and manufacturing of wireless radio frequency (RF) transceivers has developed rapidly in recent ten yeas due to rapid development of RF integrated circuits and the evolution of high-speed digital signal processors (DSP). Such high speed signal processors, in conjunction with the development of high resolution analog to digital converters and digital to analog converters, has made it possible for RF designers to digitize higher intermediate frequencies, thus reducing the RF section and enhancing the overall performance of the RF section.
標簽： Transceivers Wireless Digital
上傳時間： 2020-05-27
上傳用戶：shancjb
The General Packet Radio Service (GPRS) allows an end user to send and receive data in packet transfer mode within a public land mobile network (PLMN) without using a permanent connection between the mobile station (MS) and the external network during data transfer. This way, GPRS opti- mizes the use of network and radio resources (RRs) since, unlike circuit- switched mode, no connection between the MS and the external network is established when there is no data flow in progress. thus, this RR optimiza- tion makes it possible for the operator to offer more attractive fees.
上傳時間： 2020-05-27
上傳用戶：shancjb
In cellular networks, it is estimated that 2 3 of calls and over 90% of data services occur indoors. However, some surveys show that many households and businesses experience a poor indoor coverage problem. It has been identified that poor coverage is the main reason for churn, which is very costly for operators in saturated markets. How to provide good indoor coverage cost effectively is thus a demanding challenge for operators.
標簽： Technologies Femtocells Deployment and
上傳時間： 2020-05-27
上傳用戶：shancjb
Providing QoS while optimizing the LTE network in a cost efficient manner is very challenging. thus, radio scheduling is one of the most important functions in mobile broadband networks. The design of a mobile network radio scheduler holds several objectives that need to be satisfied, for example: the scheduler needs to maximize the radio performance by efficiently distributing the limited radio re- sources, since the operator’s revenue depends on it.
標簽： Communications Future Mobile LTE
上傳時間： 2020-05-27
上傳用戶：shancjb
Ever since ancient times, people continuously have devised new techniques and technologies for communicating their ideas, needs, and desires to others. thus, many forms of increasingly complex communication systems have appeared over the years. The basic motivations behind each new one were to improve the transmission fidelity so that fewer errors occur in the received message, to increase the transmission capacity of a communication link so that more infor- mation could be sent, or to increase the transmission distance between relay sta- tions so that messages can be sent farther without the need to restore the signal fidelity periodically along its path.
標簽： Communications Essentials Optical
上傳時間： 2020-05-31
上傳用戶：shancjb
Wireless communications has become a field of enormous scientific and economic interest. Recent success stories include 2G and 3G cellular voice and data services (e.g., GSM and UMTS), wireless local area networks (WiFi/IEEE 802.11x), wireless broadband access (WiMAX/IEEE 802.16x), and digital broadcast systems (DVB, DAB, DRM). On the physical layer side, traditional designs typically assume that the radio channel remains constant for the duration of a data block. However, researchers and system designers are increasingly shifting their attention to channels that may vary within a block. In addition to time dispersion caused by multipath propagation, these rapidly time-varying channels feature frequency dispersion resulting from the Doppler effect. They are, thus, often referred to as being “doubly dispersive.”
標簽： Time-Varying Channels
上傳時間： 2020-06-01
上傳用戶：shancjb
In this book we focus on the basic signal processing that underlies current and future ultra wideband systems. By looking at signal processing in this way we hope this text will be useful even as UWB applications mature and change or regulations regarding ultra wideband systems are modified. The current UWB field is extremely dynamic, with new techniques and ideas being presented at every communications and signal-processing conference. The basic signal-processing techniques presented in this text though will not change for some time to come. thus, we have taken a somewhat theoretical approach, which we believe is longer lasting and more useful to the reader in the long term than an up-to-the-minute summary that is out of date as soon as it is published.
標簽： Wideband Signals Systems Ultra 1st
上傳時間： 2020-06-01
上傳用戶：shancjb
A wireless ad-hoc network is a wireless network deployed without any infrastructure. In such a network, there is no access point or wireless router to forward messages among the computing devices. Instead, these devices depend on the ad-hoc mode of their wireless net‐ work interface cards to communicate with each other. If the nodes are within the transmis‐ sion range of the wireless signal, they can send messages to each other directly. Otherwise, the nodes in between will forward the messages for them. thus, each node is both an end system and a router simultaneously.
上傳時間： 2020-06-01
上傳用戶：shancjb
This effort started as an answer to the numerous questions the authors have repeatedly had to answer about electrostatic discharge (ESD) protection and input/output (1/0) designs. In the past no comprehensive book existed suffi- ciently covering these areas, and these topics were rarely taught in engineering schools. thus first-time I/O and ESD protection designers have had consider- able trouble getting started. This book is in part an answer to such needs.
上傳時間： 2020-06-05
上傳用戶：shancjb
GaN is an already well implanted semiconductor technology, widely diffused in the LED optoelectronics industry. For about 10 years, GaN devices have also been developed for RF wireless applications where they can replace Silicon transistors in some selected systems. That incursion in the RF field has open the door to the power switching capability in the lower frequency range and thus to the power electronic applications. Compared to Silicon, GaN exhibits largely better figures for most of the key specifications: Electric field, energy gap, electron mobility and melting point. Intrinsically, GaN could offer better performance than Silicon in terms of: breakdown voltage, switching frequency and Overall systems efficiency.
標簽： GaN-on-Si Displace and SiC Si
上傳時間： 2020-06-07
上傳用戶：shancjb
