DataCom_Module 1.pdf

INTRODUCTION TO DATA AND DIGITAL COMMUNICATION Aaroon Loeb WHAT IS COMMUNICATION? Communication is transferring data reliably from one point to another. -Data could be voice, video, codes etc.. It is important to receive the same information that was sent from the transmitter....

INTRODUCTION TO DATA AND DIGITAL COMMUNICATION Aaroon Loeb WHAT IS COMMUNICATION? Communication is transferring data reliably from one point to another. -Data could be voice, video, codes etc.. It is important to receive the same information that was sent from the transmitter. DATA AND DIGITAL Data refers to the raw facts that are collected while Digital refers to the utilization of digital tools, systems, and processes for creating, storing, processing, and communicating information. DATA COMMUNICATION Data Communication is a process of exchanging data or information. In case of computer networks this exchange is done between two devices over a transmission medium. This process involves a communication system which is made up of hardware and software. The hardware part involves the sender and receiver devices and the intermediate devices through which the data passes. The software part involves certain rules which specify what is to be communicated, how is to be communicated and when. It is also called as a Protocol. Basic Components of Data Communication Data Communication has five basic components that are as follows: Message: It is the data or the information that is to be exchanged between two points. Often in the real world, we share messages in the form of texts, numbers, pictures, audio, and videos. Sender: It is the node (device) that is intended to send the information being transferred or communicated. It has mechanisms of its own that make information encoded in a format that is feasible and secure to transfer on the transmission medium accurately and timely. Receiver: The device that holds the responsibility of receiving the encoded information and decoding it into a certain format accurately and sending the feedback is the receiver.  Transmission Medium: It is a path such as a cable that serves as traveling media on which the message is transferred from the sender to the receiver end. Protocol: The protocol is the rules that are agreed upon between sender and receiver which govern the entire exchange process. These protocols make communication possible between two devices without them may be connected but won’t be communicating. DIGITAL COMMUNICATION Digital Communication involves the physical transfer of data and information through a suitable communication channel. This exchange of information in the form of discrete messages can take place Point to Point or Point to Multipoint. Conventionally analog signals have been used to establish a connection and start communication over large distances but this made the signals suffer many losses such as distortion, interference, and even security breaches. These problems were overcome by the usage of digital signals over analog ones. Analog signals are digitized using different techniques. Communication using these digital signals makes it more accurate and less vulnerable to losses or breaches. Basic Components of Digital Communication Digital Communication has the following basic components: Source: Any point of data origin that can offer a piece of information that may be analog or digital can consider a source. Input Transducer: The transducer at the input end performs the task of converting a physical input from point of source into an electrical signal. It is also equipped with an analog to a digital converter where the analog signal needs to be digitized for further transfer or exchange. This digital signal is nothing but a sequence of binary numbers, i.e. 0s and 1s. Source Encoder: At the source encoder, the compression of the digitized signal data is done to minimize the number of bits while maintaining the correctness of the data. For the compression removal of redundancy is an important step. In this way, the effective utilization of the bandwidth is ensured.  Channel Encoder: The compressed data from the source code is encoded for error correction using a channel encoder. To prevent the alteration of the data signal during transmission because of noise in the channel, the channel encoder adds a few redundant bits to the data being transmitted called the error-correcting bits. Digital Modulator: The transmitting channel modulates the signal to be transmitted and also the signal can be converted from digital format to analog hence making it ready to travel along with the medium. Channel: Channel is a transmission medium through which the signal transmission takes place.  Output Transducer: Here the output signal is converted from the electrical form to the physical form. Output Signal: Signal that is produced after the complete process as the output is the output signal.  APPLICATIONS DATA DIGITAL COMMUNICATION COMMUNICATION Wireless networks (sending or recieving data Digital watches wirelessly from remote Image processing servers using computer Speech processing connected to internet Data Compression through a WiFi) LAN Modem  DATA FLOW Simplex communication is undirectional only one of the devices sends the data and the other one only receives the data Example: in the above diagram: a CPU send data while a monitor only recieves data. Half-duplex both the stations can transmit as well as receive but not at the same time. When one device is sending other can only receive and vice versa Example: A walkie-talkie Full-duplex data can be transmitted in both directions on a signal carrier at the same time. Example: plain old telephone service; the parties at both ends of a call can speak and be heard by the other party simultaneously. (both parties at both ends can speak and hear each other at the same time.) NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information. NETWORK CRITERIA Performance -Depends on Network Elements -Measured in terms of Delay and Throughput Reliability -Failure rate of network components Measured in terms of availability/robustness Security -Data protection against corruption/loss of data due to: 1.Errors 2.Malicious users PHYSICAL STRUCTURES Type of Connection Point to Point - single transmitter and receiver Multipoint - Multiple recipients of single transmission