1.9 Data Communication

This topic introduces the process of exchanging data between devices through a transmission medium, covering the basic components of network communication, modes of communication, and communication devices.

Definition

Data Communication: Data communication refers to the process of exchanging data or information (through a computer network) between two or more devices or systems through a transmission medium such as cables, optical fibers, or wireless mediums. This communication can involve the transfer of various types of data, including text, numbers, images, audio, and video, and it is a fundamental component of modern information technology and telecommunications.

Core Concept

Data communication is like sending a letter. You (the sender) write a message (the message), put it in an envelope, and send it through the postal system (the medium). The postal system follows rules (the protocol) to deliver it to your friend (the receiver). In computer networks, data is broken into packets, sent through cables or wireless signals, and reassembled at the destination. This allows computers, phones, and other devices to share information instantly across the world.

Detailed Explanation

Network Communication Components

Data communication is the process of transferring information from one point to another in a networking environment. Network communication consists of five basic components:

Sender: Sender, also called transmitter, is a computer/device that sends the message (data or information) from source to destination in a communication network. It may be a computer, workstation, cell phone, or camera. The sender device converts the electrical signal into a form that is suitable for transmission over the communication network.

Message: Message is the data or information that is to be transmitted. Message can be in the form of text, audio, video, or any combination of these.

Medium: Medium is the path through which message travels from source to destination. Medium can be wired, for example telephone cable, coaxial cable, and fibre optics. It can also be wireless, for example Bluetooth, Wi-Fi, microwave, radio wave, and satellite.

Receiver: Receiver is the device which receives the transmitted message. It can be a computer, workstation, telephone handset, or television set. The data received from the transmission medium may not be in proper form to be accepted by the receiver, and it must be converted to appropriate form before it is received.

Protocol: A protocol is a set of rules that governs data communications. It represents an agreement between the communicating devices. Without a protocol, two devices are connected but may not communicate with each other.

Modes of Network Communication

Modes of network communication refer to the methods or the ways information is transmitted from one place to another.

The following are different modes of data communication:

• Simplex, Half-duplex, and Full-duplex
• Synchronous and Asynchronous

Simplex Mode: In Simplex mode, the communication takes place in only one direction. In this mode, communication is unidirectional, i.e., the communication can only take place in one direction and it is not possible for the receiver to send data back. For example, data being sent to an electronic notice board found in train stations and airports. Radio and television broadcasting are also examples of simplex transmission. Transmission of information from a computer to a printer is also in one direction.

Half-duplex Mode: In half-duplex mode, the communication takes place in both directions but not at the same time. The signal can only be sent or received at one time. A common example of this type of communication is the use of walkie-talkies, where each of the persons communicating must indicate when they have finished speaking. Half-duplex transmission is also used in transaction-oriented systems, for example, communication between a computer and a credit card machine.

Full-duplex Mode: In full-duplex mode, the communication takes place in both directions at the same time. In this mode, both sender and receiver can send and receive the data simultaneously, for example, two or more computers connected to a network device such as a switch that provides full-duplex activity. It is the fastest bi-directional mode of communication. The full-duplex mode is like a two-way street, with traffic flowing in both directions at the same time.

One common example of full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time. Also, full-duplex mode is the most suitable for data communication between computers.

Asynchronous Transmission: In asynchronous transmission, the time interval between two characters is variable and not fixed. The computer devices can exchange information at their own rate, slow or fast. Start and Stop bits are used in asynchronous transmission. These bits provide timing (synchronization) for the connection between the sender and the receiver. The start bit tells the receiver that a character is coming, and the stop bit indicates that the transmission of character has ended. This type of transmission is ideal for slow-speed communication when gaps may occur during transmission.

Synchronous Transmission: In contrast, synchronous transmission uses a consistent time interval between characters. Here, the sender and receiver devices are synchronized to send data continuously, even when no data is being transmitted (by sending an idle character). No start or stop bits are needed, and the data is transmitted as one continuous bit stream or block. The receiver then counts the bits and reconstructs the data. This method is faster than asynchronous transmission because fewer control bits (like start and stop bits) are needed. A common example of synchronous transmission is the data exchange between devices in network communications.

Communication Devices

Communication devices are used to transmit data between locations in telecommunication systems. Common devices include Hub, Switch, Router, and Gateway.

Hub: A hub is a basic device that connects multiple devices in a Local Area Network (LAN). It broadcasts data to all connected devices, meaning every device sees the same data. Hubs are simple but inefficient since they send data to every device, regardless of the intended recipient.

Switch: A switch is a more intelligent device compared to a hub. It inspects incoming data packets, determines which device the data is for, and sends it only to the correct device. This reduces network traffic and increases efficiency.

Router: A router connects multiple networks, often linking a local network to the internet. It determines the best path for data packets to travel from one network to another and forwards them accordingly. Routers help direct internet traffic and are essential for network communication.

Gateway: A gateway connects different types of networks that use different protocols. It acts as a translator, converting data formats from one network to another to ensure compatibility. For instance, it may connect a network of PCs with an IBM mainframe network.

Comparison of Communication Devices

Intermediate Level

Data communication involves five components: sender, message, medium, receiver, and protocol. Modes include simplex (one-way), half-duplex (two-way, one at a time), and full-duplex (two-way simultaneously). Transmission can be asynchronous (variable timing, start/stop bits) or synchronous (fixed timing, continuous stream). Communication devices include hubs (broadcast to all), switches (send only to intended device), routers (connect networks and find best path), and gateways (translate between different protocols). These devices form the backbone of modern networks, enabling efficient and reliable data exchange.

Important Points

• - Data communication = exchange of data between devices.
• - Five components: Sender, Message, Medium, Receiver, Protocol.
• - Medium can be wired (cable, fiber) or wireless (Wi-Fi, Bluetooth).
• - Modes: Simplex (one-way), Half-duplex (two-way, one at a time), Full-duplex (two-way, simultaneous).
• - Asynchronous: variable timing, start/stop bits.
• - Synchronous: fixed timing, continuous stream.
• - Devices: Hub (broadcast), Switch (intended device), Router (connects networks), Gateway (translates protocols).

Remember

• - Five Components: Sender, Message, Medium, Receiver, Protocol.
• - Simplex: One-way (radio, TV).
• - Half-duplex: Two-way, one at a time (walkie-talkie).
• - Full-duplex: Two-way, simultaneous (telephone).
• - Asynchronous: Start/stop bits, variable timing.
• - Synchronous: No start/stop bits, fixed timing.
• - Hub: Broadcasts to all.
• - Switch: Sends to intended device.
• - Router: Connects networks.
• - Gateway: Translates protocols.

Common Mistakes

• - Confusing half-duplex and full-duplex: Half-duplex is two-way but not simultaneous; full-duplex is simultaneous.
• - Mixing up hub and switch: Hub broadcasts to all; switch sends only to the intended device.
• - Thinking router and gateway are the same: Router connects similar networks; gateway connects different protocols.
• - Forgetting the five components of data communication: Sender, Message, Medium, Receiver, Protocol.
• - Assuming asynchronous is always slower: Asynchronous is suitable for slow-speed communication; synchronous is faster but requires synchronization.

Quick Revision

Data communication is the exchange of data between devices. It has five components: sender, message, medium, receiver, and protocol. Modes include simplex (one-way), half-duplex (two-way, one at a time), and full-duplex (two-way, simultaneous). Transmission can be asynchronous (variable timing, start/stop bits) or synchronous (fixed timing, continuous stream). Communication devices include hubs (broadcast), switches (intended device), routers (connect networks), and gateways (translate protocols).

60-Second Revision

• Simplex: One-way (radio).
• Half-duplex: Two-way, one at a time (walkie-talkie).
• Full-duplex: Two-way, simultaneous (telephone).
• Async: Start/stop bits, variable timing.
• Sync: Fixed timing, continuous stream.
• Hub: Broadcasts.
• Switch: Intended device.
• Router: Connects networks.
• Gateway: Translates protocols.