Abstract-The effect of the companding process on QAM signals has been under investigation for the past several years. The compander, included in the PCM telephone network to improve voice performance, has an unusual affect on digital QAM data signals which are transmitted over the same channel. The quantization noise, generated by the companding process which is multiplicative (and asymmetric), degrades the detectability performance of the outermost points of the QAM constellation more than that of the inner points. The combined effect of the companding noise and the inherent white gaussian noise of the system, leads us to a re-examination of signal constellation design. In this paper we investigate the detectability performance of a number of candidates for signal constellations including, a typical rectangular QAM constellation, the same constellation with the addition of a smear-desmear operation, and two new improved QAM constellation designs with two-dimensional warpi
标签： investigation Abstract-The companding the
上传时间： 2013-12-20
上传用户：英雄
After an introduction to the history of mobile communications, this guide considers the basics of mobile radio, the design of cellular and private radio systems, and issues of interworking with the fixed network. It then looks at the role of the mobile radio operator, the design and operation of mobile radio networks, the needs of large user groups, and relevant regulatory and government decisions. A final section focuses on career development through resolution of conflicts, understanding managerial issues, and professional vehicles.
标签： communications introduction considers the
上传时间： 2016-06-24
上传用户：nanshan
This m file models a DPSK UWB system using a delay in one leg of the mixer, correlation receiver low pass filter combination requiring no template for synching. Various waveforms are displayed throughout the system to allow the user to observe operation of the system.
标签： correlation receiver models system
上传时间： 2013-12-25
上传用户：yyyyyyyyyy
sql equipment management system for the Institute of Laboratory office automation management system an important part of it can lend to the return of the equipment scrapped and a new standardized management, thereby increasing efficiency and avoiding waste of resources. background database using Access, prospects of development tools using Visual Basic. The system uses ADO data access technology, and each database table and operation of the field to the type of package, which succeeded in object-oriented programming thinking applied to the database application design.
标签： management system Laboratory automation
上传时间： 2016-08-15
上传用户：784533221
ST7787 芯片的SPEC，比亚迪2.4inchLCM的SPEC。The ST7787 is a single-chip controller/driver for 262K-color, graphic type TFT-LCD. It consists of 720 source line and 320 gate line driving circuits. This chip is capable of connecting directly to an external microprocessor, and accepts Serial Peripheral Interface (SPI), 8-bits/9-bits/16-bits/18-bits parallel interface. Display data can be stored in the on-chip display data RAM of 240x320x18 bits. It can perform display data RAM read/write operation with no external operation clock to minimize power consumption. In addition, because of the integrated power supply circuits necessary to drive liquid crystal, it is possible to make a display system with the fewest components.
上传时间： 2016-09-22
上传用户：woshini123456
IEEE 802.11d-2001, Amendment to IEEE 802.11-1999, (ISO/IEC 8802-11) Information technology--Telecommunications and information exchange between systems--Local and metropolitan area networks--Specific requirements--Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Specification for operation in Additional Regulartory Domains
标签： 802.11 IEEE Information technology
上传时间： 2014-01-21
上传用户：坏天使kk
IEEE 802.11F-2003 IEEE Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol Across Distribution Systems Supporting IEEE 802.11 operation
标签： IEEE Interoperability Multi-Vendor Recommended
上传时间： 2013-12-09
上传用户：独孤求源
IEEE 802.11j-2004 IEEE Standard for Information technology—Telecommunications and information exchange between systems--Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—Amendment 7: 4.9 GHz–5 GHz operation in Japan
标签： Telecommunications IEEE Information information
上传时间： 2014-01-17
上传用户：asasasas
IEEE 802.16e-2005 IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems Amendment for Physical and Medium Access Control Layers for Combined Fixed and Mobile operation in Licensed Bands.
标签： IEEE metropolitan Interface for
上传时间： 2016-10-02
上传用户：litianchu
版本更新了一下，到5.84了，需要用VS.net平台进行编译运行，介绍与原来的一样！ 磁盘文件的安全删除，我们通常所执行的删除操作并不是真正的删除只是清除了文件的fat表内容，文件数据还在磁盘上，可以恢复，所以不安全。-disk deletion of the security document, we usually enforced by the delete operation does not really delete the file will simply remove the fat table of contents, document data on the disk is, can be restored, therefore unsafe.
上传时间： 2016-11-05
上传用户：大三三
