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Analog transmission offers advantages in the transmission of analog information. Additionally, it is more bandwidth-conservative and is widely available.
Analog Data
Analog has an advantage with respect to the transmission of information which is analog in its native form, such as voice, image and video. The process of transmission of such information is relatively straightforward in an analog format, whereas conversion to a digital bit stream requires conversion equipment. Such equipment adds cost, contributes additional points of failure, and can negatively affect the quality of the signal through the conversion process, itself. The impacts on analog and digital conversion are discussed fully in the examination of T-carrier (Chapter 8).
Bandwidth
A raw information stream consumes less bandwidth in analog form than in digital form. This is particularly evident in CATV transmission, where 50 or more analog channels routinely are provided over a single coaxial cable system. Without the application of compression techniques on the same cable system, only a few digital channels could be supported.
Presence
Finally, analog transmission systems are already in place, worldwide. The interconnection of those systems is routine and all aspects of the standards for are well understood and easily implemented. As the majority of network traffic is voice and as the vast majority of voice terminals are analog devices, voice communications largely depends on analog networks; conversion to digital networks would require expensive, wholesale conversion of such terminal equipment.
Digital transmission offers advantage in the transmission of digital information. Additionally, such data can be compressed effectively and relatively easily. Security of the data can be more readily ensured and the error performance of digital networks are much improved over their analog counterparts. Finally, the cost-effectiveness of such networks is improved by virtue of the greater bandwidth they provide, especially since they can be more easily upgraded and more effectively managed.
Digital Data
Just as it is better to transmit analog information in an analog format, it is better to transmit digital information in a digital format. Digital transmission certainly has the advantage where binary computer data is being transmitted. The equipment required to convert digital data to an analog format and send the digital bit streams over an analog network can be expensive, susceptible to failure, and can create errors in the information.
Compression
Digital data can be compressed relatively easily, thereby increasing the efficiency of transmission. As a result, substantial volumes of voice, data, video and image information can be transmitted using relatively little raw bandwidth.
Security
Digital systems offer better security. While analog systems offer some measure of security through the scrambling, or intertwining of several frequencies, scrambling is fairly simple to defeat. Digital information, on the other hand, can be encrypted to create the appearance of a single, pseudo-random bit stream. Thereby, the true meaning of individual bits, sets of bits, or the total bit stream cannot be determined without having the key to unlock the encryption algorithm employed.
Quality
Digital transmission offers improved error performance (quality) as compared to analog. This is due to the devices that boost the signal at periodic intervals in the transmission system in order to overcome the effects of attenuation. Additionally, digital networks deal more effectively with noise, which always is present in transmission networks.
Cost
The cost of the computer components required in digital conversion and transmission has dropped considerably, while the ruggedness and reliability of those components has increased over the years.
Upgradability
Since digital networks are comprised of computer (digital) components, they are relatively easy to upgrade. Such upgrades can increase bandwidth, improve error performance, and enhance functionality. Some upgrades can be effected remotely over a network, eliminating the need to dispatch expensive technicians for that purpose.
Management
Generally speaking digital networks can be managed much more easily and effectively due to the fact that such networks consist of computerized components. Such components can sense their own level of performance, isolate and diagnose failures, initiate alarms, respond to queries, and respond to commands to correct any failure. Further, the cost of so enabling these components continues to drop.
As we have noted, electromagnetic energy attenuates over a distance through either a wire or the air. Therefore, it is necessary to place some sort of device at regular intervals in a network to overcome this phenomenon. These boosting units read a weak incoming signal and create a stronger outgoing signal until the signal reaches another boosting unit, and so on. Analog networks make use of devices known as amplifiers, while repeaters are employed in digital networks.
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