  Signals, Modulation Types, and Access Technologies Authors: Mr. Lawrence Harte Number of Pages: 50 Number of diagrams: 22 Copyright: 2004
Printed or Electronic Version (3.4MB) Available - Electronic Version has Color Diagrams Wireless Technology Basics explains the fundamentals of wireless technology and terminology. This includes how the radio frequency spectrum is divided, the basics of radio frequency transmission and modulation, antennas and radio networks. This book explains how the radio spectrum is divided into frequency bands and why specific frequency ranges are assigned to specific types of devices. Discussed are the differences between analog and digital signal types and how they are used by radio devices. You will learn about the key modulation types including amplitude (AM), frequency (FM), and phase (PM) modulation. Discussed are physical and logical channels and how a single physical channel may have more....Sample Diagrams There are 22 self explanatory diagrams in this book Signal Digitization This diagram shows how an analog signal is converted to a digital signal. This diagram shows that an acoustic (sound) signal is converted to an audio electrical signal (continuously varying signal) by a microphone. This signal is sent through an audio band-pass filter that only allows frequency ranges within the desired audio band (removes unwanted noise and other non-audio frequency components). The audio signal is then sampled every 125 microseconds (8,000 times per second) and converted into 8 digital bits. The digital bits represent the amplitude of the input analog signal.
Phase Modulation This figure shows a sample of phase modulation (PM). In this diagram, a digital signal (on top) creates a phase modulated carrier signal (on bottom). As the digital signal voltage is increased, the frequency of the radio signal changes briefly so the phase (relative timing) of the transmitted signal advances compared to the unmodulated radio carrier signal. This results in a phase-shifted signal (solid line) compared to an unmodulated reference radio signal (dashed lines). When the voltage of the digital signal is decreased, the frequency changes again so the phase of the transmitted signal retards compared to the unmodulated radio carrier signal.
Code Division Multiplexing This figure shows how a single direct sequence spread spectrum communication channel can have several channels. In this example, there are 3 different code patterns that are used for communication channels. When a receiver uses the reference code, a direct sequence spread spectrum system can build a mask as shown in this figure for each conversation allowing only that information which falls within the mask to be transmitted or received.
Table of Contents Wireless Technology Basics Dividing the Radio Frequency (RF) Spectrum LicensingFrequency Allocation Charting RF Channels and Bandwidth Radio Propagation Signal Types Analog SignalsDigital Signals Digitization of an Analog Signal Modulation of the Radio Waves Amplitude Modulation (AM)Frequency Modulation (FM) Phase Modulation (PM) Radio Access Technologies Frequency Division Multiple Access (FDMA)Time Division Multiple Access (TDMA) Spread Spectrum (FHMA and CDMA) Duplex Operation Analog (Audio) Signal Processing Digital Signal Processing Radio Signal Processing Antennas Antenna GainRadio Transmitters and Receivers Wireless Network Infrastructure Radio TowersSwitching Facilities Interconnection to Other Networks Customer Databases Public Switched Telephone Network (PSTN) Public Data Network (PDN) Internet About the Author Mr. Lawrence Harte is the managing director of Althos, an expert information provider covering the communications industry. He has over 29 years of technology analysis, development, implementation, and business management experience. Mr. Harte has worked for leading companies including Ericsson/General Electric, Audiovox/Toshiba and Westinghouse and consulted for hundreds of other companies. Mr. Harte continually researches, analyzes, and tests new communication technologies, applications, and services. He has authored over 30 books on telecommunications technologies on topics including Wireless Mobile, Data Communications, VoIP, Broadband, Prepaid Services, and Communications Billing. Mr. Harte’s holds many degrees and certificates include an Executive MBA from Wake Forest University (1995) and a BSET from the University of the State of New York, (1990). Mr. Harte can be contacted at LHarte@Althos.com.Description Wireless Technology Basics explains the fundamentals of wireless technology and terminology. This includes how the radio frequency spectrum is divided, the basics of radio frequency transmission and modulation, antennas and radio networks. This book explains how the radio spectrum is divided into frequency bands and why specific frequency ranges are assigned to specific types of devices. Discussed are the differences between analog and digital signal types and how they are used by radio devices. You will learn about the key modulation types including amplitude (AM), frequency (FM), and phase (PM) modulation. Discussed are physical and logical channels and how a single physical channel may have many logical channels. Access technologies are described including frequency division (FDMA), time division, (TDMA), and code division (CDMA) are showing how access technologies allow radio bandwidth to be shared so many users can share a limited amount of frequency bands and communication channels. Included are the basics of how analog and digital signal processing including filtering, digital signal processing, and speech coding. Covered are antenna and radio transmission fundamentals. Also included is a brief description of wireless network equipment such as base stations and switching systems. Some of the most important topics featured are: · How the radio spectrum is divided and why frequencies are assigned to specific types of devices |
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