Networking and Telecommunications

2.1 Computer Networks

Types of networks by geographical coverage:

Type	Full Form	Coverage	Example
PAN	Personal Area Network	~10 metres	Bluetooth devices, smartwatch ↔ phone
LAN	Local Area Network	Building/campus	Office computers, Wi-Fi network
MAN	Metropolitan Area Network	City	Cable TV networks, city Wi-Fi
WAN	Wide Area Network	Country/global	Internet (largest WAN)

Network topologies:

• Bus: linear chain of devices
• Ring: circular connection
• Star: hub/switch at centre — most common today
• Mesh: every device connected to every other
• Tree: hierarchical

Modern networks typically use star topology.

Protocols are rules governing communication. Key protocols:

• TCP/IP: Foundation of Internet communication; TCP ensures reliable delivery, IP handles addressing and routing
• HTTP/HTTPS: Web browsing; HTTPS uses SSL/TLS encryption
• FTP: File transfer
• SMTP/POP3/IMAP: Email protocols
• DNS (Domain Name System): Translates domain names (google.com) to IP addresses — "phone book of the Internet"

IP Addressing

IPv4: 32-bit address (e.g., 192.168.1.1); about 4.3 billion unique addresses — exhausted in 2011.

IPv6: 128-bit address (e.g., 2001:0db8:85a3::8a2e:0370:7334); virtually unlimited (3.4 × 10³⁸) — solving the address shortage.

2.2 Mobile Telecommunications Generations

Generation	Year	Key Feature	Speed	Technology
1G	1980s	Voice only	2.4 Kbps	Analogue
2G	1991	Digital voice + SMS	9.6–384 Kbps	GSM, CDMA
3G	2000s	Mobile internet	Up to 7.2 Mbps	UMTS, HSPA
4G/LTE	2010s	Broadband mobile internet	Up to 100 Mbps (theoretical 1 Gbps)	LTE Advanced
5G	2019+	Ultra-fast, low latency, massive IoT	Up to 20 Gbps theoretical; 100–300 Mbps actual	NR (New Radio), mm-waves

5G Key Specifications

• Peak speed: 20 Gbps (download)
• Latency: < 1 millisecond (4G: ~30–50 ms) — enables real-time control
• Device density: 1 million devices per km² (4G: ~100,000)
• Use cases: eMBB (Enhanced Mobile Broadband), URLLC (Ultra-Reliable Low-Latency Communication for autonomous vehicles/remote surgery), mMTC (Massive Machine Type Communication for IoT)

India's 5G

• Spectrum auctioned August 2022 (Rs 1.5 lakh crore — India's largest spectrum auction)
• Commercial launch: 13 October 2022 (Airtel in 8 cities, Jio in 4 cities)
• By end-2024: 100+ cities; India had 100+ million 5G subscribers
• India's 5G uses midband spectrum (3.3–3.67 GHz, 26 GHz mmWave)
• 6G research underway: India's Bharat 6G Vision document released March 2023; target — India contributes 10% of 6G patents

2.3 Internet Architecture

World Wide Web (WWW): An application-layer system of interlinked hypertext documents accessed via the Internet. Invented by Tim Berners-Lee (CERN, 1989).

Web generations:

• Web 1.0 (1990s): Read-only; static HTML pages
• Web 2.0 (2000s–present): Read-write; user-generated content; social media, blogs, wikis
• Web 3.0 (emerging): Decentralised; blockchain-based; user-owned data; semantic web (AI interprets content)

IoT protocols for constrained devices and networks:

• MQTT: lightweight messaging for IoT sensors
• CoAP: constrained devices
• Zigbee: short-range wireless for smart home devices
• LoRaWAN: long-range, low-power — for agricultural and city sensors

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