CHAPTER 3 Data Communication.pdf
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The document discusses data communication, defining data as processed information and outlining the components of a communication system, including the message, sender, receiver, medium, and protocols. It also explains the characteristics of data transmissions, including signal types (analog and digital), transmission modes (asynchronous and synchronous), and direction of transmission (simplex, half-duplex, full-duplex). Additionally, it highlights the importance of standards for ensuring compatibility and efficient networking among devices.
CHAPTER 3 Data Communication.pdf
- 1. CHAPTER 3 DATA COMMUNICATION DATA The collection of raw facts and figures is called data. The word data is derived from the Latin language and it is plural of Datum. The text, numbers, symbols, images, voice, and video which are processed by computers and digital devices are called data. Data can be considered as unprocessed information. COMMUNICATION Communication is the process of sharing a message. A conversation between two people is an example of communication. DATA COMMUNICATION Data Communication is the process of transferring data electrically from one place to another. It is the process of exchange of data and information between two parties such as humans and electronic or computing devices. COMPONENTS OF COMMUNICATION SYSTEM A Communication system has the following five components. Message It is the information or data to be communicated. Common forms of information include text, numbers, pictures, audio, and video. Sender It is the device that generates and sends a message. It can be a computer, telephone handset, etc. Receiver Any particular digital electronic device can receive data in form of a message. The location of receiving computer is generally different from the sending computer. Like the sender, it can also be a computer, telephone handset, etc. Medium It is the channel or path through which the message is carried from the sender to the receiver. Some examples include twisted-pair cable, coaxial cable, radio waves, etc. Protocol Protocols are the rules and procedures by which computers exchange data on the network. The sender and receiver follow the same protocols to communicate with each other. In other words, a protocol is an agreement between two parties or vendors, using communication devices.
- 2. STANDARDS Standards are the set of rules for data communication that are needed for the exchange of information among devices. It is important to follow Standards that are created by various Standard Organizations like IEEE, ISO, ANSI, etc. OR Standards are rules that define the appearance, functionality, or protocols of some equipment. They are essential for network communication. Network standards define rules of communications among computing devices. This ensures that companies (i.e. Cisco and IBM) that manufacture computing and networking products follow these uniform standards. By following standards, all hardware becomes compatible with the network, allowing efficient networking to take place. CHARACTERISTICS OF DATA TRANSMISSIONS Data communication has several characteristics but some are discussed below: 1. Signal type 2. Transmission mode 3. Direction of transmission 1. SIGNAL A signal is an electromagnetic or electrical current that carries data from one system or network to another. TYPES OF SIGNAL There are two types of signals discussed below: Analog Signals Analog signals are continuously varying signals or waves that change with time and are used to represent data. An analog signal can be used to measure changes in some physical quantities such as light, sound, pressure, or temperature. Example An example of an analog signal is the human voice. When we speak, we use air to transmit an analog signal. An electrical signal from an audio tape can also be in analog form. Characteristics Of Analog Signals Amplitude The amplitude of a signal refers to the height of the signal. It is equal to the vertical distance from a given point on the waveform to the horizontal axis. It is measured in volts. Frequency Frequency refers to the number of periods in one second or the number of cycles per second. Frequency is measured in Hertz (Hz).
- 3. Digital Signals A digital signal is an electrical signal that is converted into a pattern of bits to represent a sequence of discrete values, at any given time. It can only be one of the finite numbers represented as 0 or 1. Examples Examples of digital signals are Computers, Digital Phones, Digital pens, etc. DIFFERENCE BETWEEN ANALOG AND DIGITAL SIGNAL PARAMETERS ANALOG SIGNAL DIGITAL SIGNAL Definition An analog signal is a continuous wave that changes over time. A digital signal is a discrete wave that carries information in binary form. Range The Analog signal has no fixed range. Digital signal has an infinite number i.e. 0 and 1. Flexibility Analog hardware is not flexible. Digital hardware is flexible in implementation. Representation An analog signal is represented by a sine wave. A digital signal is represented by square waves Examples The human voice is an example of an analog signal. Signals used by the computer are the digital signal. 2. TRANSMISSION MODES (Asynchronous And Synchronous) Transmission is the action of transferring or moving something from one position or person to another. It is a mechanism for transferring data between two devices connected using a network. It is also called communication Mode. In computer networking there are two types of transmission: Synchronous transmissions Asynchronous transmissions ASYNCHRONOUS TRANSMISSION In Asynchronous Transmission, data is sent in form of a byte or character. This transmission is the half-duplex type transmission. In this transmission start bits and stop bits are added with data. It does not require synchronization.
- 4. EXAMPLE Email Forums Letters etc. SYNCHRONOUS TRANSMISSION In Synchronous Transmission, data is sent in form of blocks or frames. This transmission is the full-duplex type. Between sender and receiver, synchronization is compulsory. In Synchronous transmission, There is no gap present between data. It is efficient and more reliable than asynchronous transmission to transfer a large amount of data. EXAMPLE Chat Rooms Telephonic Conversations Video Conferencing etc. DIFERENCES BETWEEN SYNCHRONOUS AND ASYNCHRONOUS TRANSMISSION SYNCHRONOUS TRANSMISSION ASYNCHRONOUS TRANSMISSION In Synchronous transmission, data is sent in form of blocks or frames. In Asynchronous transmission, data is sent in form of bytes or characters. Synchronous transmission is fast. Asynchronous transmission is slow. Synchronous transmission is costly Synchronous transmission is costly In Synchronous transmission, the time interval of transmission is constant. In Asynchronous transmission, the time interval of transmission is not constant, it is random. In this transmission, users have to wait till the transmission is complete before getting a response back from the server. Here, users do not have to wait for the completion of transmission to get a response from the server. In Synchronous transmission, there is no gap present between data. In Asynchronous transmission, there is a gap present between data. Efficient use of transmission lines is done in synchronous transmission. While in Asynchronous transmission, the transmission line remains empty during a gap in character transmission. The start and stop bits are not used in transmitting data. The start and stop bits are used in transmitting data that imposes extra overhead. Synchronous transmission needs Asynchronous transmission does not
- 5. precisely synchronized clocks for the information of new bytes. need synchronized clocks as a parity bit is used in this transmission for information of new bytes. 3. DIRECTION OF TRANSMISSION Another characteristic of data transmission is direction Data may flow in more than one direction. There are three types of transmission modes. They are: Simplex Mode Half-duplex Mode Full-duplex Mode Simplex Mode Simplex is the data transmission mode in which the data can flow only in one direction, i.e., the communication is unidirectional. In this mode, a sender can only send data but can not receive it, and vice versa. OR In simplex mode, Sender can send the data but the sender can’t receive the data. It is unidirectional communication. Example Radio and TV transmission, keyboard, mouse, etc. Advantages It utilizes the full capacity of the communication channel during data transmission. It has the least or no data traffic issues as data flows only in one direction. Disadvantages It is unidirectional having no inter-communication between devices. There is no mechanism for information to be transmitted back to the sender(No mechanism for acknowledgment). Half-Duplex Mode
- 6. In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive it, and vice versa. The half-duplex mode is used in cases where there is no need for communication in both directions at the same time. OR In half-duplex mode, Sender can send the data and also can receive the data one at a time. It is two-way directional communication but one at a time. Example Walkie-talkie in which message is sent one at a time and messages are sent in both directions. Advantages Speed is a big advantage of a full-duplex. The device can receive and send data, but not at the same time. Troubleshooting is very easy Data is transmitted on both sides Disadvantages In a half Duplex, more data cannot be transmitted on both sides at the same time. When one device sends data, the device on the other hand only receives data. It is slow in data transmission. Delay in data transmission. Full-Duplex Mode In full-duplex mode, both stations can transmit and receive simultaneously. In full-duplex mode, signals going in one direction share the capacity of the
- 7. link with signals going in another direction, this sharing can occur in two ways: Either the link must contain two physically separate transmission paths, one for sending and the other for receiving. Or the capacity is divided between signals traveling in both directions. OR In full-duplex mode, Sender can send the data and also can receive the data simultaneously. It is two-way directional communication simultaneously. Example: Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time. Advantages Performance of full-duplex mode is much better than half and simplex mode. The speed of full-duplex mode is high than simplex and half-duplex mode. Data can be sent and received on both sides, which increases the performance of the network. No delay in communication, because both devices send and receive data at the same time. Disadvantages No proper bandwidth utilization as the same line is used for sending and receiving data at the same time. It is more complex than a simplex and half-duplex mode. DIFFERENCES BETWEEN THE TYPES OF TRANSMISSION MODES PARAMETERS SIMPLEX MODE HALF DUPLEX MODE FULL-DUPLEX MODE Direction Of Communication Simplex mode is a uni-directional communication. Half Duplex mode is a two-way directional communication but one at a time. Full-Duplex mode is a two-way directional communication simultaneously. Sender And Receiver In simplex mode, Sender can send the data but the sender can’t In Half-duplex mode, Sender can send the data and also can receive In Full-duplex mode, Sender can send the data and also can receive
- 8. receive the data. the data one at a time. the data simultaneously. Channel Usage Usage of one channel for the transmission of data. Usage of one channel for the transmission of data. Usage of two channels for the transmission of data. Performance The simplex mode provides less performance than a half duplex and a full duplex. The Half-duplex mode provides less performance than the full duplex. Full-duplex provides better performance than simplex and half- duplex modes. Bandwidth Utilization Simplex utilizes the maximum of a single bandwidth. The Half-duplex involves lesser utilization of single bandwidth at the time of transmission. The Full-duplex doubles the utilization of transmission bandwidth. Examples Keyboard and monitor Walkie- talkie The walkie-talkie is an example of half-duplex mode. The telephone network is an example of a full- duplex mode.