Chapter 11 - Data Communication
11.1 Concept of Communication
What is Communication?
Communication is the process of transferring information from one place to another.
In computer science, data communication refers to the exchange of data between two or more devices using a transmission medium.
📌 Communication can be:
- Human to human
- Human to machine
- Machine to machine
Need for Data Communication
- Sharing information quickly
- Resource sharing
- Remote access
- Global connectivity
11.2 Components of Data Communication
A data communication system consists of five basic components:
🔹 1️⃣ Sender
The device that sends data. Example: Computer, mobile phone
🔹 2️⃣ Receiver
The device that receives data. Example: Server, printer
🔹 3️⃣ Message
The data or information being transmitted. Example: Text, image, audio, video
🔹 4️⃣ Transmission Medium
The physical path through which data travels. Example: Cable, optical fiber, wireless signals
🔹 5️⃣ Protocol
A set of rules that governs data communication. Example: TCP/IP, HTTP
📌 All five components must work together for successful communication.
11.3 Measuring Capacity of Communication Media
What is Bandwidth?
Bandwidth is the maximum data transfer capacity of a communication channel.
📌 It indicates how much data can be transmitted per unit time.
Units of Bandwidth
| Unit | Meaning |
|---|---|
| bps | bits per second |
| Kbps | 1,000 bps |
| Mbps | 1,000,000 bps |
| Gbps | 1,000,000,000 bps |
Data Transfer Rate
- Higher bandwidth → faster data transfer
- Lower bandwidth → slower communication
📌 Bandwidth ≠ Speed (but related)
11.4 Types of Data Communication
Data communication can be classified based on direction of data flow.
🔹 1️⃣ Simplex
- One-way communication
- Sender → Receiver only
📌 Example:
- Keyboard to computer
- Television broadcast
🔹 2️⃣ Half Duplex
- Two-way communication, but not simultaneously
📌 Example:
- Walkie-talkie
🔹 3️⃣ Full Duplex
- Two-way communication simultaneously
📌 Example:
- Telephone call
- Video conferencing
Comparison Table (IMPORTANT)
| Type | Direction | Example |
|---|---|---|
| Simplex | One-way | Keyboard |
| Half Duplex | Both (one at a time) | Walkie-talkie |
| Full Duplex | Both (simultaneous) | Phone |
11.5 Switching Techniques
What is Switching?
Switching is the technique used to route data from source to destination across networks.
Types of Switching Techniques
🔹 1️⃣ Circuit Switching
- Dedicated path established before communication
- Path remains reserved
📌 Example:
- Traditional telephone network
✔ Reliable ❌ Inefficient for data transfer
🔹 2️⃣ Packet Switching
- Data broken into packets
- Packets travel independently
📌 Example:
- Internet
✔ Efficient ✔ Cost-effective
🔹 3️⃣ Message Switching
- Entire message sent and stored at intermediate nodes
- No dedicated path
📌 Example:
- Old telegraph systems
❌ Slow ❌ Not used today
Comparison Table
| Switching | Path | Efficiency |
|---|---|---|
| Circuit | Dedicated | Low |
| Packet | Dynamic | High |
| Message | Store & Forward | Very Low |
11.6 Transmission Media
What is Transmission Media?
Transmission media is the physical path through which data is transmitted.
Types of Transmission Media
🔹 Guided Media (Wired)
1️⃣ Twisted Pair Cable
- Two insulated copper wires twisted together
- Low cost
- More noise
📌 Example:
- Telephone lines
2️⃣ Coaxial Cable
- Central copper conductor
- Better shielding
📌 Example:
- Cable TV
3️⃣ Optical Fiber
- Uses light signals
- Very high speed
- Long distance
📌 Advantages:
- High bandwidth
- Secure
- No electromagnetic interference
🔹 Unguided Media (Wireless)
1️⃣ Radio Waves
- Used for broadcasting
- Long range
2️⃣ Microwaves
- Line-of-sight transmission
- Used in satellite communication
3️⃣ Infrared
- Short range
- Used in TV remotes
Comparison (Exam Favourite)
| Media | Speed | Cost |
|---|---|---|
| Twisted Pair | Low | Cheap |
| Coaxial | Medium | Moderate |
| Optical Fiber | Very High | Expensive |
11.7 Mobile Telecommunication Technologies
Evolution of Mobile Communication
🔹 1️⃣ 1G
- Analog
- Voice only
🔹 2️⃣ 2G
- Digital
- Voice + SMS
📌 Example: GSM
🔹 3️⃣ 3G
- Voice + data
- Internet access
🔹 4️⃣ 4G
- High-speed Internet
- Video streaming
📌 Example: LTE
🔹 5️⃣ 5G
- Ultra-high speed
- Low latency
- Supports IoT, AI
Comparison Table
| Generation | Speed | Features |
|---|---|---|
| 2G | Low | Voice, SMS |
| 3G | Medium | Internet |
| 4G | High | HD streaming |
| 5G | Very High | Smart tech |
11.8 Protocol
What is a Protocol?
A protocol is a set of rules and standards that govern communication between devices.
📌 Without protocols, communication is not possible.
Functions of a Protocol
- Data formatting
- Error control
- Flow control
- Addressing
Common Protocols (IMPORTANT)
| Protocol | Use |
|---|---|
| TCP/IP | Internet communication |
| HTTP | Web pages |
| HTTPS | Secure web |
| FTP | File transfer |
| SMTP | Email sending |
| POP3 | Email receiving |
📝 NCERT EXAM SUMMARY (MUST MEMORISE)
- Communication = data transfer
- 5 components of data communication
- Bandwidth measured in bps
- Simplex, Half Duplex, Full Duplex
- Circuit vs Packet switching
- Guided vs Unguided media
- Mobile generations 1G–5G
- Protocols define rules
Short Answer & Case-Study Questions
PART A: Short Answer Questions
(Each answer: 3–4 sentences)
Q1. What is data communication?
Answer: Data communication is the process of transferring data from one device to another using a communication medium. It allows computers and devices to exchange information. Communication can be wired or wireless.
Q2. List the basic components of a data communication system.
Answer: The basic components are sender, receiver, message, transmission medium, and protocol. All components must work together for successful communication. Absence of any component disrupts communication.
Q3. What is bandwidth?
Answer: Bandwidth is the maximum data transfer capacity of a communication channel. It determines how much data can be transmitted per second. It is measured in bps, Kbps, Mbps, or Gbps.
Q4. Why is bandwidth important in data communication?
Answer: Higher bandwidth allows faster data transmission. Low bandwidth causes delays and slow communication. Applications like video calls and streaming require high bandwidth.
Q5. What is simplex communication? Give an example.
Answer: Simplex communication allows data transfer in only one direction. The receiver cannot send data back to the sender. Example: Television broadcasting.
Q6. What is half-duplex communication?
Answer: Half-duplex communication allows data transfer in both directions but not simultaneously. Only one device can transmit at a time. Example: Walkie-talkie.
Q7. What is full-duplex communication?
Answer: Full-duplex communication allows data transmission in both directions simultaneously. Both sender and receiver can communicate at the same time. Example: Telephone calls.
Q8. What is switching in networking?
Answer: Switching is the process of routing data from source to destination across a network. It helps in efficient data transmission. Different switching techniques are used based on network requirements.
Q9. What is packet switching?
Answer: Packet switching divides data into small packets. Each packet travels independently to the destination. This technique is efficient and used by the Internet.
Q10. What is circuit switching?
Answer: Circuit switching establishes a dedicated path before data transmission begins. The path remains reserved until communication ends. Example: Traditional telephone network.
Q11. What is transmission media?
Answer: Transmission media is the physical path through which data travels from sender to receiver. It can be wired or wireless. Examples include cables, radio waves, and optical fiber.
Q12. Differentiate between guided and unguided media.
Answer: Guided media uses physical cables such as twisted pair and optical fiber. Unguided media uses wireless signals like radio and microwave. Guided media is more secure than unguided media.
Q13. What is optical fiber? Mention one advantage.
Answer: Optical fiber uses light signals to transmit data. It supports very high data transfer rates. It is secure and free from electromagnetic interference.
Q14. What is a protocol?
Answer: A protocol is a set of rules that governs data communication. It defines how data is formatted, transmitted, and received. Without protocols, devices cannot communicate properly.
Q15. Name any two communication protocols and their uses.
Answer: HTTP is used for transferring web pages. FTP is used for transferring files between computers.
PART B: Case-Study / Scenario-Based Questions (5)
(Long description + decision-based answers)
Q16. A school wants fast, secure transmission of exam data between two buildings. Which transmission media should be used and why?
Answer: Optical fiber should be used because it provides very high speed and secure communication. It is suitable for long distances and large data transfer. It is also resistant to interference and data loss.
Q17. A news channel broadcasts programs to millions of viewers. Which type of data communication is used?
Answer: Simplex communication is used because data flows only in one direction—from the broadcaster to viewers. Viewers cannot send data back. This is suitable for mass broadcasting.
Q18. A mobile user is making a voice call where both users speak and listen at the same time. Identify the communication type and justify.
Answer: Full-duplex communication is used. Both users can transmit and receive data simultaneously. This allows smooth real-time conversation.
Q19. An Internet service provider breaks large files into smaller parts before sending them. Which switching technique is used and why?
Answer: Packet switching is used. It divides data into packets that travel independently. This improves efficiency, reliability, and reduces congestion.
Q20. A smart city uses sensors, cameras, and connected devices to monitor traffic and pollution. Which mobile technology generation is most suitable and why?
Answer: 5G technology is most suitable because it offers very high speed and low latency. It supports a large number of connected devices. This makes it ideal for IoT-based smart city applications.