TERM PAPER OF: ECE 302

TOPIC:- ANALOG VS DIGITAL

SUBMITED TO: Lec . GURUSHARNJEET SINGH

SUBMITTED BY:ROCKEY

ROLL NO: RB6803B46

SECTION: B6803

REGSN NO.: 10801381

ACKNOWLEDGEMENTI would like to thanks all those who have encouraged me to make a project. I am grateful to our lecturer LEC. Gurusharnjeet SINGH, who acted as a source of inspiration for me. He encouraged me to make a project. I will never forget his support and word of wisdom. His immense help and suggestion for improving the content of the project are highly appreciable .Without his involvement this project would not have been possible. I am also thankful to my friends for their help and support.

Abstract – This term is containg information about the analog and digital signal, communication and difference between the analog communication and digital communication.

Keywords- analog signal, digital signal,communication system, analog communication system, digital communication system, analog vs digital communication system.

Introduction

Analog signal

Analog signals are a representation of time varying quantities in a continuous signal. Basically, a time variance is presented in a manner in which some sort of information is passed using various types of methods. These methods can include electrical, mechanical, hydraulic or pneumatic systems. Unlike digital signals, which use a numeric method of transmitting information, analog signals use small fluctuations in the signal itself to pass information.

Digital signal

A digital system would be to flick the light switch on and off. There's no 'in between' values, unlike our string. If the switch you are using is not a dimmer switch, then the light is either on, or off. In this case, the transmitter is the light bulb, the media is the air, and the receiver is your eye. This would be a digital system.

Communication System

•Communication is the process of exchanging information between source and destination(sink)

•Routing of information requires a communication link - Channel to transmit information between source and destination.

•In past ages communication is carried over by runners, torches, pigeons etc. Such mediums are now obsolete in modern communication systems.

•Communication engineering deals with transmitting information through electrical signals, i.e. information or message such as spoken words, photographs, live scenes and sounds are first converted to electrical signals before being transmitted on communication link to receiver or destination.

•Electrical communication is reliable, fast and economical at the same time. Modern communication has applications such as e-banking, e-shopping, teleconferencing etc a possible reality.

Analog communication

Analog Communication is a data transmitting technique in a format that utilizes continuous signals to transmit data including voice, image, video, electrons etc. An analog signal is a variable signal continuous in both time and amplitude which is generally carried by use of modulation.

Analog circuits do not involve quantisation of information unlike the digital circuits and consequently have a primary disadvantage of random variation and signal degradation, particularly resulting in adding noise to the audio or video quality over a distance.

Data is represented by physical quantities that are added or removed to alter data. Analog transmission is inexpensive and enables information to be transmitted from point-to-point or from one point to many. Once the data has arrived at the receiving end, it is converted back into digital form so that it can be processed by the receiving computer.

Analog communication system properties

Analog communication systems, amplitude modulation (AM) radio being a typifying example, can inexpensively communicate a bandlimited analog signal from one location to another (point-to-point communication) or from one point to many (broadcast). the coherent receiver provides the largest possible signal-to-noise ratio for the demodulated message. this receiver thus indicates that some residual error will always be present in an analog system's output.

Although analog systems are less expensive in many cases than digital ones for the same application, digital systems offer much more efficiency, better performance, and much greater flexibility.

Efficiency

The Source Coding Theorem allows quantification of just how complex a given message source is and allows us to exploit that complexity by source coding (compression). In analog communication, the only parameters of interest are message bandwidth and amplitude. We cannot exploit signal structure to achieve a more efficient communication system.

Performance

Because of the Noisy Channel Coding Theorem, we have a specific criterion by which to formulate error-correcting codes that can bring us as close to error-free transmission as we might want. Even though we may send information by way of a noisy channel, digital schemes are capable of error-free transmission while analog ones cannot overcome channel disturbances; see this problem for a comparison.

Flexibility

Digital communication systems can transmit real-valued discrete-time signals, which could be analog ones obtained by analog-to-digital conversion, and symbolic-valued ones (computer data, for example). Any signal that can be transmitted by analog means can be sent by digital means, with the only issue being the number of bits used in A/D conversion (how accurately do we need to represent signal amplitude). Images can be sent by analog means (commercial

television), but better communication performance occurs when we use digital systems (HDTV). In addition to digital communication's ability to transmit a wider variety of signals than analog systems, point-to-point digital systems can be organized into global (and beyond as well) systems that provide efficient and flexible information transmission. Computer networks, explored in the next section, are what we call such systems today. Even analog-based networks, such as the telephone system, employ modern computer networking ideas rather than the purely analog systems of the past.

Consequently, with the increased speed of digital computers, the development of increasingly efficient algorithms, and the ability to interconnect computers to form a communications infrastructure, digital communication is now the best choice for many situations.

Advantages of Analog - Uses less bandwidth

More accurate

Disadvantages of Analog-

The effects of random noise can make signal loss and distortion impossible to recover

Digital communication

Data transmission, digital transmission or digital communications is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibres, wireless communication channels, and storage media. The data is represented as an electro-magnetic signal, such as an electrical voltage, radiowave , microwave or infra-red signal.

Digital communication systems properties

As the received signal becomes increasingly noisy, whether due to increased distance from the transmitter (smaller α) or to increased noise in the channel (larger N0), the probability the receiver makes an error approaches 1/2. In such situations, the receiver performs only slightly better than the "receiver" that ignores what was transmitted and merely guesses what bit was transmitted. Consequently, it becomes almost impossible to communicate information when digital channels become noisy.

As the signal-to-noise ratio increases, performance gains--smaller probability of error pe -- can be easily obtained. At a signal-to-noise ratio of 12 dB, the probability the receiver makes

an error equals 10-8. In words, one out of one hundred million bits will, on the average, be in error.

Once the signal-to-noise ratio exceeds about 5 dB, the error probability decreases dramatically. Adding 1 dB improvement in signal-to-noise ratio can result in a factor of 10 smaller pe.

Signal set choice can make a significant difference in performance. All BPSK signal sets, baseband or modulated, yield the same performance for the same bit energy. The BPSK signal set does perform much better than the FSK signal set once the signal-to-noise ratio exceeds about 5 dB.

Advantages of Digital -

Less expensive

More reliable

Easy to manipulate

Flexible

Compatibility with other digital systems

Only digitised information can be transported through a noisy channel without degradation

Integrated networks

Disadvantages of Digital -

Sampling Error

Digital communications require greater bandwidth than analogue to transmit the same information.

The detection of digital signals requires the communications system to be synchronised, whereas generally speaking this is not the case with analogue systems.

Analog vs digital communication

Analog signals are signals with continuous values. Analog signals are used in many systems,

although the use of analog signals has declined with the advent of cheap digital signals.

Digital signals are signals that are represented by binary numbers, "1" or "0". The 1 and 0

values can correspond to different discrete voltage values, and any signal that doesnt quite fit

into the scheme just gets rounded off.

In the case of Digital Communication, the modulation technique used is Digital Modulation, which uses 1’s and 0’s and hence the use of digital communication will be favor in communication for a longer distance. When we consider analog communication, we use analog modulation and it is not used for long distance communication.

In the case of digital communication, the error is very less and loss of data can be avoided. This ensures that less loss of information is present in Digital Communication and hence we can say that Digital Communication is error free.

The influence of noise is very less in the case of Digital communication, when compared to that of analog communication Since we used digital modulation in the case of digital communication, which uses 1’s and 0’s, we usually experience a very high transmission in this case.

Since the loss of data is very less in Digital communication we can say that, Digital Communication is more reliable and accurate than that of analog communication.

The set up required for digital communication is easier and hence we can say that installation process is easier for Digital Communication.

Privacy can be maintained in the case of digital communication.

We can also able to merge voice, video and data and transmit them over a single transmission system, in the case of digital communication.

Analog systems are less tolerant to noise, make good use of bandwidth, and are easy to manipulate mathematically. However, analog signals require hardware receivers and transmitters that are designed to perfectly fit the particular transmission. If you are working on a new system, and you decide to change your analog signal, you need to completely change your transmitters and receivers. Digital signals are more tolerant to noise, but digital signals can be completely corrupted in the presence of excess noise. In digital signals, noise could cause a 1 to be interpreted as a 0 and vice versa, which makes the received data different than the original data. Imagine if the army transmitted a position coordinate to a missile digitally, and a single bit was received in error? This single bit error could cause a missile to miss its target by miles. Luckily, there are systems in place to prevent this sort of

scenario, such as checksums and CRCs, which tell the receiver when a bit has been corrupted and ask the transmitter to resend the data. The primary benefit of digital signals is that they can be handled by simple, standardized receivers and transmitters, and the signal can be then dealt with in software.

security is another priority of messaging services in modern days.Digital communication provides better security to messages than the analog communication.It can be achieved through various coding techniques available in digital communication.

Conclusion

Digital signal communication is expensive than analog signal but now on these digital signal having more scope than analog because it reduces information loss and noise .it increases security and privacy regarding to the analog signal.so digital communication having wide scope in future.

Biblography and refrences

http://www.wisegeek.com/what-is-an-analog-signal.htm

http://www.wisegeek.com/what-is-an-analog-signal.htm

http://cnx.org/content/m0074/latest/

http://www.answerbag.com/q_view/31169