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U. Glaeser

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FIGURE 42.22 Typical analog and digital signals.<br />

Each of these possibilities has its pros and cons. When a signal carrying information is transmitted,<br />

it looses its energy and strength and gathers some interference (noise) as it propagates away from the<br />

transmitter. If energy of signal is not boosted at some intermediate point, it may attenuate beyond<br />

recognition before it reaches its intended destination. That will certainly be a wasted effort. In order to<br />

boost energy and strength of a signal, it must be amplified (in case of analog signals) and rebuild (in<br />

case of digital signals). When an analog signals is amplified, the noise also becomes amplified and that<br />

certainly lowers expectations about receiving the signal at its destination in its original (or close to it)<br />

form. On the other hand, digital signals can be processed and reconstructed at any intermediate point<br />

and, therefore, the noise can essentially be filtered out. Moreover, transmission of information in digital<br />

form has many other advantages including processing of information for error detection and correction,<br />

applying encryption and decryption techniques to sensitive information, and many more. Thus, digital<br />

information transmission technology has become the dominant technology in the field communications<br />

[9,18].<br />

As indicated earlier, communication technology has experienced phenomenal growth over the past<br />

several decades. The following two factors have always played a critical role in shaping the future of<br />

communications [20]:<br />

• Severity of user needs to exchange information<br />

• State of the technology related to communications<br />

Historically, inventions have always been triggered by the severity of needs. It has been very true for<br />

the field of communications as well. In addition, there is always an urge and curiosity to make things<br />

happen faster. When electricity was discovered and people (scattered around the globe) wanted to<br />

exchange information over longer distances and in less time, telegraph was invented. Morse code was<br />

developed with shorter sequences (of dots and dashes) for more frequent alphabets. That resulted in<br />

transmission of message in a shorter duration of time. Presence of electricity, and capability of wires to<br />

© 2002 by CRC Press LLC

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