2nd PUC Computer Science Notes – Chapter 11 Data Communication
Complete Short Notes & Exam Preparation Guide
Based on the NCERT textbook
Student-friendly notes • Exam-oriented revision • Chapter structure preserved
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Table of Contents
- 11.1 Concept of Communication
- 11.2 Components of Data Communication
- 11.3 Measuring Capacity of Communication Media
- 11.4 Types of Data Communication
- 11.5 Switching Techniques
- 11.6 Transmission Media
- 11.7 Mobile Telecommunication Technologies
- 11.8 Protocol
- Questions & Answers
- Important Questions
- Quick Revision
- Final Revision
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Chapter Overview
This chapter explains Data Communication, its components, communication capacity, communication modes, switching techniques, transmission media, wireless technologies, mobile telecommunication generations and communication protocols.
Communication
Exchange of data between connected devices.
Transmission Media
Links through which messages travel between communicating devices.
Protocols
Rules followed by communicating parties for successful communication.
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11.1 Concept of Communication
The term Data Communication consists of the words Data and Communication. Data may be text, image, audio, video or multimedia files. Communication is the act of sending or receiving data.
Devices Used
- Personal computers
- Mobile phones
- Laptops
- Printers
- Servers
- Switches
A network of computing devices connected through communication media.
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11.2 Components of Data Communication
Five important aspects are involved in communication between two computing devices using a network:
1. Sender
A device capable of sending data over a network.
2. Receiver
A device capable of receiving data from the network.
3. Message
The data or information exchanged between sender and receiver.
4. Communication Media
The path through which the message travels.
5. Protocols
The rules followed by communicating parties.
Sender
A sender is a computer or other device capable of sending data over a network.
Examples: computer, mobile phone, smartwatch, walkie-talkie and video recording device.
Receiver
A receiver is a computer or other device capable of receiving data from the network.
Examples: computer, printer, laptop, mobile phone and television.
In computer communication, the sender and receiver are known as nodes in a network.
Message
A message is the data or information that needs to be exchanged between the sender and receiver.
Messages may be in the form of text, number, image, audio, video or multimedia.
Communication Media
Communication media is the path through which a message travels from source to destination. It is also called a medium or link.
It may be wired or wireless. Examples mentioned in the chapter include television cable, telephone cable, Ethernet cable, satellite link and microwaves.
Protocols
Protocols are a set of rules that communicating parties must follow for successful and reliable data communication.
Examples mentioned: Ethernet and HTTP.
The five major aspects are sender, receiver, message, communication media and protocols.
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11.3 Measuring Capacity of Communication Media
In data communication, the transmission medium is also known as a channel. The capacity of a channel is the maximum amount of signals or traffic that the channel can carry.
11.3.1 Bandwidth
- Higher bandwidth gives a higher data transfer rate.
- Normally, bandwidth is the difference between maximum and minimum frequency contained in composite signals.
- Bandwidth is measured in Hertz (Hz).
| Unit | Conversion |
|---|---|
| Kilohertz | 1 KHz = 1000 Hz |
| Megahertz | 1 MHz = 1000 KHz = 1,000,000 Hz |
11.3.2 Data Transfer Rate
It is measured in bits per second (bps).
| Unit | Conversion given in the textbook |
|---|---|
| 1 Kbps | 1 Kbps = 210 bps = 1024 bps |
| 1 Mbps | 1 Mbps = 220 bps = 1024 Kbps |
| 1 Gbps | 1 Gbps = 230 bps = 1024 Mbps |
| 1 Tbps | 1 Tbps = 240 bps = 1024 Gbps |
Example 11.1
A user wants to upload a text document at the rate of 10 pages per 20 seconds. Assume that one page contains 1600 characters and each character is of 8 bits. Find the required data rate of the channel.
Solution
Answer: 6400 bps
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11.4 Types of Data Communication
Data communication happens in the form of signals between two or more computing devices or nodes. Data transfer can happen over a point-to-point or multipoint communication channel.
The chapter broadly categorises communication into three types:
Simplex
One-way communication.
Half-duplex
Two-way communication, but not at the same time.
Full-duplex
Two-way communication at the same time.
11.4.1 Simplex Communication
- The devices use the entire capacity of the link to transmit data.
- It is similar to a one-way street.
- Examples given include data entered through a keyboard and audio sent to a speaker.
- Controlling home appliances through IoT is also given as an example.
Simplex communication occurs in one direction.
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11.4.2 Half-duplex Communication
- While one device sends data, the other receives it.
- The direction of transmission can be switched.
- It is similar to a narrow one-way bridge shared by vehicles moving in both directions.
- Example: Walkie-talkie.
Communication occurs in both directions, but at different moments.
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11.4.3 Full-duplex Communication
- It is similar to a two-way road where vehicles can move in both directions at the same time.
- Examples include mobile phones and landline telephones.
- The transmission-link capacity is shared between signals travelling in both directions.
- It can use two physically separate simplex lines: one for sending and one for receiving.
- Alternatively, the capacity of a single channel can be shared between signals travelling in different directions.
Full-duplex permits simultaneous communication in both directions.
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| Basis | Simplex | Half-duplex | Full-duplex |
|---|---|---|---|
| Direction | One direction | Both directions | Both directions |
| Same time? | No reverse communication | No | Yes |
| Example in chapter | Keyboard to computer; audio to speaker | Walkie-talkie | Mobile phone; landline telephone |
11.5 Switching Techniques
In a network having multiple devices, making a dedicated connection between every pair of devices can be costly for large networks. Switching provides an alternative by routing data through various nodes in a network.
The switching process forms a temporary route for data transmission. Two commonly used switching techniques described in the chapter are:
Circuit Switching
A dedicated path is established before communication begins.
Packet Switching
The message is divided into smaller packets transmitted independently.
11.5.1 Circuit Switching
The chapter gives an earlier telephone-call system as an example, where switching equipment found a physical path or channel from the caller’s telephone to the receiver’s telephone.
11.5.2 Packet Switching
- Different packets belonging to the same message may take different routes.
- Each packet contains a header and the main message part.
- The header contains the destination address and other information.
- When all packets reach the destination, they are reassembled into the complete message.
- A channel is occupied only during transmission of a packet.
- After transmission of a packet, the channel becomes available for packets from other communicating parties.
| Basis | Circuit Switching | Packet Switching |
|---|---|---|
| Path | Dedicated path established before communication. | Packets are transmitted independently through the network. |
| Data | All packets follow the same established path. | Different packets may take different routes. |
| Channel occupation | Dedicated path is used during the communication. | Channel is occupied only during packet transmission. |
| Example / reference | Earlier telephone-call system. | Packet-based transmission described in the chapter. |
Other Terms Mentioned
VoIP: A communication methodology designed to deliver both voice and multimedia communications over Internet Protocol.
VoLTE: Voice over Long-Term Evolution is described as a standard for high-speed wireless communication for mobile phones, including IoT and wearables.
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11.6 Transmission Media
In data communication, transmission media are the links that carry messages between two or more communicating devices.
Transmission media are classified into:
Communication media are broadly classified as wired and wireless media.
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Guided / Wired Transmission
In guided transmission, there is a physical link made of wire or cable through which data in the form of signals travels between nodes. Metallic cables and fiber-optic cables are examples. They are also called wired media.
Unguided / Wireless Transmission
In unguided transmission, data travels through air in the form of electromagnetic waves using an antenna. These are also called wireless media.
Dish-shaped antennas are used for sending and receiving data over longer distances. They are mounted on taller buildings to maintain line-of-sight. Waves gradually become weaker after travelling a certain distance through air, so repeaters are installed to regenerate signals of the same energy.
11.6.1 Wired Transmission Media
Three commonly used guided/wired media described in the chapter are:
- Twisted-pair cable
- Coaxial cable
- Fiber-optic cable
Twisted-pair and coaxial cables carry electric signals, whereas optical fiber carries light signals.
(A) Twisted Pair Cable
- Several pairs may be combined and covered with protective outer wrapping.
- Each twisted pair acts as a single communication link.
- The twisted configuration reduces the effect of electrical interference from nearby similar pairs.
- Twisted pairs are less expensive.
- They are commonly used in telephone lines and LANs.
Types: Unshielded Twisted-Pair (UTP) and Shielded Twisted-Pair (STP).
Logical structure of UTP and STP cables as shown in the textbook.
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(B) Coaxial Cable
- It has a copper wire at the core.
- The core is surrounded by insulating material.
- The insulator is surrounded by an outer conductor, usually a copper mesh.
- The outer conductor is covered with plastic.
- The shielded design helps the copper core transmit data with reduced environmental interference.
- It carries signals of higher frequencies over longer distances.
Main layers of a coaxial cable.
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(C) Optical Fibre
- A thin transparent strand of glass is present at the centre.
- The centre is covered with a layer of less dense glass called cladding.
- The arrangement is covered with an outer jacket made of PVC or Teflon.
- Optical fiber is usually used in backbone networks.
- It is lightweight and has higher bandwidth, giving a higher data transfer rate.
- Signals can travel longer distances.
- Electromagnetic noise cannot affect the cable.
- Optical fibers are expensive and unidirectional.
- Two cables are required for full-duplex communication.
Light travels through the glass core of optical fiber.
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11.6.2 Wireless Transmission Media
In wireless communication, information travels as electromagnetic signals through air. The electromagnetic spectrum from 3 KHz to 900 THz is available for wireless communication.
Wireless technologies allow communication between two or more devices over short to long distances without requiring physical media.
The chapter mentions Bluetooth, Wi-Fi and WiMax as wireless communication technologies.
Frequency ranges and categories shown in the chapter.
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Classification of Transmission Waves and Their Properties
| Transmission Waves | Properties |
|---|---|
| Radio Waves |
|
| Microwaves |
|
| Infrared Waves |
|
11.6.3 Wireless Technologies
(A) Bluetooth
- Bluetooth-enabled printers can print documents without a physical connection.
- Bluetooth devices contain a low-cost transceiver chip.
- The chip uses the unlicensed 2.4 GHz frequency band.
- Devices can send data within a range of 10 metres.
- Speed is 1–2 Mbps.
- Devices within 10 metres can form a personal area network called a piconet.
- Devices in a piconet work in a master-slave configuration.
- A master device can communicate with up to 7 active slave devices at the same time.
- Bluetooth technology allows up to 255 devices to build a network.
- Out of them, 8 devices can communicate at the same time; remaining devices can remain inactive waiting for a response command from the master.
(B) Wireless LAN
Wireless LAN is a local area network and is a popular way to connect to the Internet.
- IEEE assigns numbers to different LAN standards.
- Wireless LAN is numbered 802.11 and is popularly known as Wi-Fi.
- Networks may contain laptops, mobile phones and network devices called access points (APs).
- An access point creates a wireless local area network by connecting to a wired router, switch or hub.
- Access points are connected to a wired network.
- Devices communicate or access the Internet through an access point.
An access point connects wireless devices to a wired network.
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Benefits of WLAN mentioned in the chapter
- Wireless connections can extend or replace an existing wired infrastructure.
- They increase access for mobile devices.
- They provide easy Internet access in public places.
WiMax
WiMax stands for Worldwide Interoperability for Microwave Access. Like Wi-Fi, it is used for communication in wireless networks, but WiMax uses a larger spectrum to deliver connections to various devices.
- It has a higher data transfer rate than Wi-Fi as described in the chapter.
- It can span a larger area.
- It is used in MAN applications.
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11.7 Mobile Telecommunication Technologies
The mobile phone network is described as the most used network in the world. It allows users to communicate through calls and instant messages and access the Internet through wireless connections. IoT also allows control and communication with other smart devices.
Mobile communication technologies are classified into generations: 1G, 2G, 3G, 4G and 5G.
| Generation | Information from the chapter |
|---|---|
| 1G | Came around 1982. Used only for voice calls. Analog signals carried voice between caller and receiver. |
| 2G | Came around 1991. Voice calls were transmitted digitally, giving improved call quality. Increased capacity allowed more simultaneous users. Improved security was possible because signals could be encrypted. SMS and MMS were also enabled. |
| 3G | Developed during the late 1990s and commercially introduced around 2001. Offered digital voice and data services. Provided Internet access through the same radio towers used for voice service and offered greater voice/data capacity and faster data transfer. |
| 4G | Developed because demand for faster data was increasing. It is much faster than 3G and supports interactive multimedia, voice, video, wireless Internet and other broadband services. |
| 5G | Described in the textbook as being under development. Expected to support IoT and Machine-to-Machine communication, data transfer in Gbps, connected vehicles and future Internet-of-Things devices. |
Machine-to-Machine (M2M)
Machine-to-machine communication is direct communication between devices, either wired or wireless.
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11.8 Protocol
11.8.1 Need for Protocols
Protocols are required for reasons such as flow control, access control and addressing.
Flow Control
Flow control is required when the sender and receiver have different speeds of sending and receiving data.
A sending speed of 1024 Mbps and receiving speed of 512 Mbps can result in data loss.
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If Computer A sends at 1024 Mbps and Computer B receives at 512 Mbps, Computer B must inform Computer A about the speed mismatch so that Computer A can adjust its transmission rate. Otherwise, data may be lost.
Access Control
Access control decides which nodes in a communication channel can access a shared link at a particular instant of time. Without proper access control, data packets may collide when computers send simultaneously, causing loss or corruption of data.
Protocols also define:
- How computers identify one another on a network.
- The form into which data should be converted for transit.
- How to decide whether received data is meant for that node or should be forwarded.
- How to ensure that all data reaches the destination without loss.
- How packets are rearranged and processed at the destination.
11.8.2 HyperText Transfer Protocol (HTTP)
- Tim Berners-Lee led the development of HTTP at CERN in 1989 in collaboration with IETF and W3C.
- HTTP is a request-response or client-server protocol.
- It runs over TCP.
- It is commonly used between a web browser (client) and a web server.
- It defines how information is formatted and transmitted.
- It defines how web servers and browsers respond to various commands.
A web page is written using a markup language such as HTML and stored on a web server for access through its URL. When a user enters the URL in a browser, the client sends an HTTP request to the web server and the HTTP response sends the requested web page back to the browser.
11.8.3 File Transfer Protocol (FTP)
- FTP works using a client-server model.
- A connection is established between two nodes for accessing the file.
- The user may authenticate using a user ID and password.
- The user specifies the file name and location.
- Another connection is then set up and the file transfer takes place directly between the machines.
- Some servers provide FTP logins without authentication for accessing files.
- FTP handles different file-naming conventions, data/text representations and directory structures.
11.8.4 Point to Point Protocol (PPP)
- It defines how two devices authenticate each other and establish a direct link.
- Two directly connected routers can communicate using PPP.
- Home computers connected to an Internet Service Provider through a modem also use PPP.
- Communicating devices should have duplex modes for using this protocol.
- PPP maintains data integrity.
- It ensures packets arrive in order.
- It informs the sender about damaged or lost packets and asks for retransmission.
11.8.5 Simple Mail Transfer Protocol (SMTP)
- It uses information written in the message header.
- It is not concerned with the content of the email message.
- The email header contains recipient email addresses.
- Email containing header and body is placed in an outgoing-mail queue.
- The SMTP sender program takes mails from the outgoing queue and transmits them to the destination(s).
- When delivery to a recipient is successful, that recipient’s address is removed from the destination list.
- After delivery to all recipients, the mail is removed from the outgoing queue.
- The SMTP receiver program accepts arriving mail and places it in the appropriate user mailbox.
11.8.6 Transmission Control Protocol (TCP) / Internet Protocol (IP)
Internet Protocol (IP)
IP ensures that each computer or node connected to the Internet is assigned an IP address, which identifies the node independently.
Transmission Control Protocol (TCP)
- TCP breaks the message or data into smaller chunks called IP packets.
- Packets are transmitted through the Internet from one router to another.
- TCP guarantees delivery of packets on the designated IP address.
- TCP is responsible for ordering packets so they are delivered in sequence.
The Internet contains redundant connection paths, with backbones and ISPs connected at multiple locations. Therefore, different packets of the same message may travel through different routes depending on congestion and other factors. At the destination, packets are reassembled into the original message.
| Protocol | Full Form | Main purpose described in the chapter |
|---|---|---|
| HTTP | HyperText Transfer Protocol | Primary protocol used to access the World Wide Web. |
| FTP | File Transfer Protocol | Transfers files from one machine to another. |
| PPP | Point to Point Protocol | Establishes a dedicated and direct connection between two devices. |
| SMTP | Simple Mail Transfer Protocol | Used for email services. |
| TCP/IP | Transmission Control Protocol / Internet Protocol | Standardised communication rules using a client-server model; IP addresses identify nodes and TCP handles packet delivery/order. |
Questions & Answers
1-Mark Questions
Data communication is the exchange of data between two or more networked or connected devices.
Bandwidth is the range of frequencies available for transmission of data through a channel.
Hertz (Hz).
It is the number of bits transmitted between source and destination in one second.
Full-duplex communication.
Optical fiber cable.
3 KHz – 1 GHz.
HyperText Transfer Protocol.
File Transfer Protocol.
Simple Mail Transfer Protocol.
A personal area network formed by Bluetooth-enabled communicating devices within a range of 10 metres.
2-Mark Questions
The five main components are:
- Sender
- Receiver
- Message
- Communication medium
- Protocols
| Simplex | Half-duplex |
|---|---|
| Communication is only in one direction. | Communication can occur in both directions. |
| One device is sender and the other is receiver. | Both devices can send and receive. |
| Example: keyboard to computer. | Example: walkie-talkie. |
Circuit switching establishes a dedicated path between sender and receiver before communication begins. All packets follow the established path.
Packet switching breaks a message into smaller pieces called packets. The packets are transmitted independently and may follow different routes before being reassembled at the destination.
Optical fiber has higher bandwidth and can carry signals over longer distances. Electromagnetic noise cannot affect it. It is also lightweight, but expensive and unidirectional.
Unshielded Twisted-Pair (UTP) and Shielded Twisted-Pair (STP).
3-Mark Questions
Simplex: One-way communication. Example: keyboard input or audio sent to a speaker.
Half-duplex: Two-way communication, but not at the same time. Example: walkie-talkie.
Full-duplex: Two-way communication simultaneously. Examples: mobile phones and landline telephones.
The three commonly used wired media are twisted pair, coaxial cable and fiber-optic cable. Twisted pair contains twisted copper wires and is commonly used in telephone lines and LANs. Coaxial cable has a copper core with insulating material and an outer conductor. Optical fiber carries data as light through a glass fiber and has higher bandwidth.
Radio waves: 3 KHz–1 GHz, omni-directional and used in AM/FM radio, television and cordless phones.
Microwaves: 1 GHz–300 GHz, unidirectional, require line-of-sight and are used for radar and satellite communication.
Infrared: 300 GHz–400 THz, very high frequency, cannot penetrate solid objects and is used for short-distance point-to-point communication.
Protocols are needed for flow control, access control and addressing. Flow control handles differences in sender and receiver speeds. Access control decides which node can use a shared link at a particular time and prevents collisions and resulting loss or corruption of data.
4/5-Mark Questions
Transmission media are links that carry messages between communicating devices. They are classified as guided/wired and unguided/wireless.
Guided media use a physical wire or cable and include twisted pair, coaxial cable and fiber-optic cable. Unguided media transmit electromagnetic waves through air and include radio waves, microwaves and infrared waves.
Circuit switching establishes a dedicated path before communication, and all packets follow that path. Packet switching divides a message into packets. The packets can travel through different routes and are reassembled at the destination. In packet switching, a channel is occupied only while a packet is being transmitted.
1G used analog voice communication. 2G introduced digital voice and additional services such as SMS and MMS. 3G provided digital voice and data services and faster data transfer. 4G provided much faster data and supported multimedia, voice, video, wireless Internet and broadband services. 5G is described as under development and expected to support IoT, M2M communication, Gbps data transfer and connected devices.
HTTP: Primary protocol for accessing the World Wide Web.
FTP: Used for transferring files between machines.
PPP: Establishes a dedicated direct connection between two devices.
SMTP: Used for email services.
TCP/IP: A set of standardised rules in which IP identifies nodes using IP addresses and TCP handles packetisation, delivery and ordering.
📝 Important Questions
1 Mark
- What is data communication?
- What is bandwidth?
- What is data transfer rate?
- Which communication mode allows simultaneous two-way communication?
- Which transmission medium carries light signals?
- What is the frequency range of radio waves?
- What does HTTP stand for?
- What does FTP stand for?
- What does SMTP stand for?
- What is a piconet?
2 Marks
- List the five components of data communication.
- Differentiate simplex and half-duplex communication.
- What is circuit switching?
- What is packet switching?
- Write the types of twisted-pair cable.
- Write important features of optical fiber.
- What is Bluetooth?
- What is Wireless LAN?
3 Marks
- Explain simplex, half-duplex and full-duplex communication.
- Explain the three categories of wired transmission media.
- Explain radio waves, microwaves and infrared waves.
- Explain the need for protocols.
- Explain Bluetooth and piconet.
4/5 Marks
- Explain the different transmission media.
- Explain circuit switching and packet switching.
- Explain the generations of mobile telecommunication technologies.
- Explain HTTP, FTP, PPP, SMTP and TCP/IP.
- Explain optical fiber and list its advantages and disadvantages as given in the chapter.
Textbook Exercise — Answers
Data communication is the exchange of data between two or more networked or connected devices. Its main components are sender, receiver, message, communication medium and protocols.
Full-duplex communication.
The uploaded chapter does not provide enough information to establish a LAN-versus-MAN-versus-WAN speed and coverage comparison. Therefore, no outside information has been added here.
The three categories are twisted-pair cable, coaxial cable and fiber-optic cable.
Twisted pair consists of twisted copper wires and is commonly used in telephone lines and LANs. Coaxial cable contains a copper core, insulating material, an outer conductor and plastic covering. Fiber-optic cable carries data as light through glass and provides higher bandwidth and longer-distance transmission.
| Basis | Wired / Guided | Wireless / Unguided |
|---|---|---|
| Physical link | Uses a physical wire or cable. | No physical transmission medium is required. |
| Signal path | Signals travel through the physical link. | Electromagnetic waves travel through air using an antenna. |
| Examples | Metallic cable and fiber-optic cable. | Radio waves, microwaves and infrared waves. |
Fiber-optic cable.
Advantages:
- Lightweight.
- Higher bandwidth.
- Higher data transfer rate.
- Signals can travel longer distances.
- Electromagnetic noise cannot affect the cable.
Disadvantages:
- Expensive.
- Unidirectional.
- Two cables are required for full-duplex communication.
3 KHz – 1 GHz.
From the conversion given in the chapter: 1 Gbps = 230 bps.
Therefore:
18 Gbps = 18 × 230 bps
= 19,327,352,832 bps
HyperText Transfer Protocol.
HTTP: HyperText Transfer Protocol; the primary protocol used to access the World Wide Web.
Bandwidth: The range of frequencies available for transmission of data through a channel. It is measured in Hertz.
Bluetooth: A short-range wireless technology used to connect devices such as mobile phones, mouse, headphones, keyboards and computers. It uses the 2.4 GHz unlicensed frequency band and can send data within 10 metres at 1–2 Mbps.
DNS: DNS is mentioned in this exercise, but the uploaded chapter does not provide an explanation or definition of DNS. Therefore, no outside information has been added.
Data Transfer Rate: The number of bits transmitted between source and destination in one second. It is also called bit rate and is measured in bps.
A protocol is a set of standard rules that the communicating parties, including sender, receiver and intermediate devices, need to follow.
Example: HTTP is a request-response/client-server protocol used to access the World Wide Web.
Bandwidth = Maximum frequency − Minimum frequency
= 1 GHz − 500 MHz
= 1000 MHz − 500 MHz
= 500 MHz
⚡ Quick Revision
Important Definitions
- Data Communication
- Bandwidth
- Data Transfer Rate
- Simplex
- Half-duplex
- Full-duplex
- Circuit Switching
- Packet Switching
- Protocol
- HTTP
- FTP
- PPP
- SMTP
- TCP/IP
Important Terms
- Sender
- Receiver
- Node
- Message
- Channel
- Bandwidth
- Bit rate
- Packet
- Header
- Piconet
- Access Point
- IP address
- M2M
Important Frequencies
- Wireless spectrum: 3 KHz – 900 THz
- Radio waves: 3 KHz – 1 GHz
- Microwaves: 1 GHz – 300 GHz
- Infrared waves: 300 GHz – 400 THz
- Bluetooth: 2.4 GHz unlicensed frequency band
Important Data Rates
- 1 Kbps = 210 bps = 1024 bps
- 1 Mbps = 220 bps = 1024 Kbps
- 1 Gbps = 230 bps = 1024 Mbps
- 1 Tbps = 240 bps = 1024 Gbps
Communication Modes
- Simplex — one direction
- Half-duplex — both directions, not simultaneously
- Full-duplex — both directions simultaneously
Switching
- Circuit switching — dedicated path
- Packet switching — message divided into packets
- Packets may take different routes
- Packets are reassembled at destination
Wired Media
- Twisted pair
- Coaxial cable
- Fiber-optic cable
- Twisted pair and coaxial carry electric signals.
- Fiber optic carries light signals.
Wireless Media
- Radio waves
- Microwaves
- Infrared waves
- Wireless communication uses electromagnetic waves through air.
Mobile Generations
1G → 2G → 3G → 4G → 5G
- 1G — analog voice
- 2G — digital voice, SMS and MMS
- 3G — voice + data
- 4G — faster data and broadband services
- 5G — expected IoT, M2M and Gbps support
Protocol Full Forms
- HTTP — HyperText Transfer Protocol
- FTP — File Transfer Protocol
- PPP — Point to Point Protocol
- SMTP — Simple Mail Transfer Protocol
- TCP/IP — Transmission Control Protocol / Internet Protocol
Bluetooth Facts
- Short-range wireless technology
- 2.4 GHz unlicensed band
- Range: 10 metres
- Speed: 1–2 Mbps
- Personal area network: piconet
- Master can communicate with up to 7 active slave devices simultaneously
- Up to 255 devices can build a network
- 8 devices can communicate at the same time
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Final Revision — One-Page Memory Sheet
Data Communication
Exchange of data between two or more networked or connected devices.
Five Components
Sender + Receiver + Message + Communication Medium + Protocols
Channel Capacity
Measured using Bandwidth and Data Transfer Rate.
Communication Modes
Simplex → Half-duplex → Full-duplex
Switching Techniques
Circuit Switching + Packet Switching
Transmission Media
Wired: Twisted Pair, Coaxial, Fiber Optic
Wireless: Radio, Microwaves, Infrared
Wireless Technologies
Bluetooth + Wireless LAN/Wi-Fi + WiMax
Mobile Generations
1G → 2G → 3G → 4G → 5G
Protocols
HTTP + FTP + PPP + SMTP + TCP/IP
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- Learn the definition and five components of data communication.
- Remember bandwidth, data transfer rate and their units.
- Practise the 10-page/20-second data-rate calculation.
- Understand simplex, half-duplex and full-duplex clearly.
- Compare circuit switching and packet switching.
- Revise wired-media types and their characteristics.
- Remember radio, microwave and infrared frequency ranges.
- Revise Bluetooth range, speed, frequency and piconet facts.
- Remember Wireless LAN = 802.11 = Wi-Fi.
- Revise 1G, 2G, 3G, 4G and 5G.
- Learn protocol definitions and full forms.
- Practise bandwidth calculation: maximum frequency − minimum frequency.
- Revise the important textbook diagrams and their logical structures.
Chapter Summary
- Data communication is the exchange of data between connected devices.
- The major components are sender, receiver, message, channel and protocols.
- Transmission media are classified into guided/wired and unguided/wireless media.
- Channel capacity is described using bandwidth and data transfer rate.
- Communication modes are simplex, half-duplex and full-duplex.
- Switching techniques include circuit switching and packet switching.
- Wired media include twisted pair, coaxial cable and fiber-optic cable.
- Wireless media include radio waves, microwaves and infrared waves.
- Bluetooth is a short-range wireless technology using the 2.4 GHz unlicensed band.
- Wireless LAN is numbered 802.11 and is popularly called Wi-Fi.
- Mobile communication generations are identified as 1G, 2G, 3G, 4G and 5G.
- Protocols provide rules for flow control, access control, addressing and other communication requirements.
- HTTP, FTP, PPP, SMTP and TCP/IP are the protocols discussed in the chapter.
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