Communication Technologies

• Bluetooth: short range (about 10 metres), low power, creates PAN, IEEE 802.15.

• Wi-Fi: wireless LAN, IEEE 802.11 standard.

• NFC (Near Field Communication): a few centimetres, used in contactless payment and tap-to-pay.

• Infrared: line-of-sight, used in remotes.

• RFID: radio tags for tracking, used in libraries and toll collection (FASTag).

• GPS: satellite-based location. India's regional system is NavIC.

GSM (Global System for Mobile) uses SIM cards. CDMA (Code Division Multiple Access).

Satellites relay signals using uplink and downlink. INSAT and GSAT are Indian communication satellites. EDUSAT (2004) was India's first dedicated educational satellite. Types: geostationary (about 36,000 km altitude, appears fixed) and low-earth orbit. Used in DTH television, VSAT, weather, navigation and distance education.

Invention: Ray Tomlinson sent the first network e-mail in 1971 and introduced the @ symbol.

Address structure: username@domain.com. The username is the user's mailbox, and the domain identifies the mail server.

Parts of a message: To (main recipient), Cc (carbon copy, visible to all), Bcc (blind carbon copy, hidden from others), Subject, Body, Attachment and Signature.

Folders: Inbox (received mail), Outbox (mail waiting to be sent), Sent, Drafts (unsent saved mail), Spam or Junk (unsolicited mail) and Trash.

Protocols: SMTP sends mail (outgoing). POP3 downloads mail to one device, usually removing it from the server. IMAP keeps mail on the server and syncs across devices.

Advantages: fast, cheap, global, attachments, searchable record, asynchronous. Limitations: spam, phishing, viruses, overload, no tone or emotion, needs internet.

E-mail netiquette: clear subject, polite and concise, do not type in all capitals (it is shouting), proofread, use Reply All carefully, do not forward chain mails, respect privacy, use Bcc for large groups.

Audio-conferencing: voice-only communication among multiple locations. Video-conferencing: audio and video in real time, which allows face-to-face interaction at a distance. Types: point-to-point (two sites) and multipoint (many sites). Requirements: device (computer or phone), camera, microphone, speaker, stable internet bandwidth, and conferencing software.

Platforms: Zoom, Google Meet, Microsoft Teams, Cisco Webex. Educational uses: virtual classes, guest lectures, thesis viva, remote meetings, webinars and workshops. Advantages: saves travel cost and time, flexible, recordable, reaches remote learners. Limitations: needs bandwidth and power, technical glitches, privacy and security concerns, less personal interaction, "Zoom fatigue". Synchronous means at the same time (live class). Asynchronous means at different times (recorded lecture).

VoIP (Voice over IP) sends voice using the internet (WhatsApp calls, Skype). IoT (Internet of Things) connects everyday objects to the internet. Cloud computing gives on-demand computing resources over the internet (SaaS, PaaS, IaaS, for example Google Docs, AWS, Azure). AI and ML let machines simulate intelligence, with generative AI producing text, images and code. Big data is characterised by volume, velocity, variety (the 3 Vs). Blockchain is a decentralised, tamper-resistant ledger. AR and VR give augmented and immersive experiences.