Click to enlargeWireless Technology Basics<a name="top">

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

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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

Licensing
Frequency Allocation Charting
RF Channels and Bandwidth
Radio Propagation

Signal Types

Analog Signals
Digital 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 Gain

Radio Transmitters and Receivers

Wireless Network Infrastructure

Radio Towers
Switching 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. Hartes 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
Analog and digital signal types and how they are used by radio devices
Explanation of modulation types including amplitude (AM), frequency (FM), and phase (PM)
Description of physical and logical channels
How radio bandwidth can be shared using access
technologies such as frequency division (FDMA), time division, (TDMA), and code division (CDMA)
Basics of analog and digital signal processing
Antenna and radio transmission fundamentals
Brief description of wireless network equipment

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