Human Computer Interaction (CY-803 (C)) - Unit 5 Short Notes

UNIT 5: Mobile, Wireless, and Security Technologies

1.0 Wireless Network Paradigms & Classification

1.1 Wireless Personal Area Network (WPAN)

• Definition: A WPAN is a personal area network that connects devices within a very short range (typically < 10 meters) of an individual.

• Distinguishing Characteristics:

  • Range: Very short (1-10 m).

  • Power Consumption: Very low, enabling battery-powered operation.

  • Data Rate: Varies (e.g., Bluetooth ~1-3 Mbps, Zigbee ~250 kbps).

  • Use-Cases: Connecting personal devices (headphones, keyboard, mouse, phone to laptop).

• Comparison with Other Wireless Networks:

  | Feature | WPAN | WLAN | WMAN | WWAN | | :--- | :--- | :--- | :--- | :--- | | Range | < 10 m | ~100 m | ~5-10 km | > 10 km (cellular) | | Typical Tech | Bluetooth, Zigbee | Wi-Fi (802.11) | WiMAX (802.16) | 3G/4G/5G, LTE | | Ownership | Personal | Local (Home/Office) | Metropolitan | Wide (Nationwide) |

1.2 Wireless Local Area Network (WLAN)

• Core Principle: Provides wireless connectivity within a local area (building, campus) using radio waves, typically based on IEEE 802.11 standards.

• Deployment Scenarios: Home networks, corporate offices, public hotspots (airports, cafes). Uses an Access Point (AP) as a central hub.

1.3 Wireless Metropolitan Area Network (WMAN) - WiMAX

• Standard: Primarily based on IEEE 802.16.

• Physical Layer Architecture:

  • Uses a point-to-multipoint architecture with a base station serving multiple subscriber stations.

  • Employs Orthogonal Frequency Division Multiplexing (OFDM) for robust transmission in multipath environments.

• Modulation Techniques:

  • OFDM: Splits the data stream into multiple parallel sub-carriers, making it resistant to frequency-selective fading.

  • Adaptive Modulation: Uses higher-order Quadrature Amplitude Modulation (QAM) (e.g., 64-QAM, 256-QAM) when signal quality is good for higher throughput; switches to more robust QPSK in poor conditions.

• Operating Frequency Bands: Originally 2-11 GHz (licensed), later versions also use 3.5 GHz and 5.8 GHz bands.

1.4 Wireless Wide Area Network (WWAN) & Cellular Technologies

• Evolution & Key Differentiators:

  | Generation | Technology | Key Features & Performance | | :--- | :--- | :--- | | 2G | GSM, CDMA | Digital voice, SMS, very slow circuit-switched data (9.6 kbps). | | 2.5G/2.75G | GPRS, EDGE | Packet-switched data (always-on), higher data rates (GPRS: ~40 kbps, EDGE: ~150 kbps). | | 3G | UMTS, CDMA2000 | Mobile broadband (384 kbps - 2 Mbps), video calling, improved spectral efficiency. | | 4G/LTE | LTE, WiMAX | All-IP core, high data rates (100 Mbps mobile, 1 Gbps stationary), low latency (< 10 ms), OFDMA. | | 5G | NR (New Radio) | Ultra-high speed (multi-Gbps), ultra-low latency (< 1 ms), massive IoT support, network slicing. |

2.0 Specific Wireless Standards & Technologies

2.1 Wi-Fi (IEEE 802.11) Standards Evolution

• Chronological Development & Implications:

  | Standard | Year | Frequency | Max Theoretical Rate | Key Tech & Impact | | :--- | :--- | :--- | :--- | :--- | | 802.11b | 1999 | 2.4 GHz | 11 Mbps | First widely adopted, prone to interference (microwaves). | | 802.11a | 1999 | 5 GHz | 54 Mbps | Less interference, shorter range, not compatible with b/g. | | 802.11g | 2003 | 2.4 GHz | 54 Mbps | Backward compatible with b, popular for homes. | | 802.11n (Wi-Fi 4) | 2009 | 2.4/5 GHz | 600 Mbps | MIMO (multiple antennas), channel bonding, better range/speed. | | 802.11ac (Wi-Fi 5) | 2013 | 5 GHz | ~3.5 Gbps | Wider channels (160 MHz), 256-QAM, MU-MIMO (multi-user). | | 802.11ax (Wi-Fi 6/6E) | 2019 | 2.4/5/6 GHz | ~9.6 Gbps | OFDMA (efficient in dense deployments), BSS Coloring, Target Wake Time (TWT) for IoT. | | 802.11be (Wi-Fi 7) | 2024* | 2.4/5/6 GHz | ~46 Gbps | Multi-Link Operation (MLO), 4096-QAM, 320 MHz channels. |

  Trends: Shift to 5/6 GHz for less congestion, OFDMA for efficiency in IoT/dense environments, MU-MIMO for serving multiple clients simultaneously.

2.2 Cellular Technology Generations

• 2.5G/2.75G: GPRS (General Packet Radio Service)

  • Key Features: Introduced packet-switched domain to GSM's circuit-switched core. "Always-on" connectivity, pay-per-bit billing.

  • Capabilities: Enabled mobile internet (WAP), email. Peak rate ~40-80 kbps.

• 3G: Universal Mobile Telecommunication System (UMTS)

  • Architecture: Introduced a new radio access network (UTRAN) and a packet-switched core network (with SGSN, GGSN nodes).

  • Primary Objective: Provide mobile broadband (video calling, mobile TV) with speeds up to 2 Mbps.

• 4G & LTE (Long-Term Evolution)

  • Key Features:

    1. All-IP Network: Eliminated circuit-switched domain; voice becomes VoIP (VoLTE).

    2. High Data Rates: 100 Mbps (mobile), 1 Gbps (stationary).

    3. Low Latency: ~10 ms, enabling real-time apps.

    4. Architectural Shift: Flattened network (removed RNC in E-UTRAN), OFDMA downlink, SC-FDMA uplink.

  • Benefits: Higher spectral efficiency, seamless mobility, better support for multimedia streaming.

2.3 RFID (Radio Frequency Identification)

• Definition: Technology that uses electromagnetic fields to automatically identify and track tags attached to objects.

• System Components:

  • Tag: Microchip + antenna (stores ID/data). Passive (no battery, powered by reader's signal) or Active (has battery, longer range).

  • Reader: Emits radio waves and receives tag responses.

  • Middleware: Software that filters and processes data from readers to backend systems.

• Principle of Operation:

  • Inductive Coupling (Low-Freq/High-Freq): Reader's magnetic field induces current in tag's coil (for passive tags, < ~1 m range).

  • Backscatter (UHF/Microwave): Reader emits signal; tag modulates reflected signal to send data back (common for supply chain, longer range).

• Data Transmission Mechanisms:

  • Passive Tag: No internal power. Reader's signal provides both power and communication carrier. Data transmitted via load modulation (changing tag's antenna impedance).

  • Active Tag: Has battery. Can transmit its own signal (higher power, longer range, up to 100 m+).

3.0 Mobility Management & Internet Protocols

3.1 Mobile IP (Internet Protocol)

• Core Purpose: Enables a mobile node (MN) to maintain continuous connectivity while changing its point of attachment to the internet, using a permanent Home Address (HoA).

• Key Components:

  • Home Agent (HA): Router in MN's home network; tunnels packets to MN's Care-of Address (CoA).

  • Foreign Agent (FA): Router in visited network; provides CoA and registers MN with HA (in MIPv4).

  • Care-of Address (CoA): Temporary IP address used by MN in the visited network.

  • Correspondent Node (CN): The node MN is communicating with.

• Mobile IPv4 vs. Mobile IPv6:

  | Feature | Mobile IPv4 | Mobile IPv6 | | :--- | :--- | :--- | | Addressing | 32-bit IP, CoA can be FA's or co-located. | 128-bit IP, only co-located CoA (no FA needed). | | Tunneling | IP-in-IP or GRE encapsulation by HA. | IPv6 Header extension headers (Routing Header Type 2). | | Route Optimization | Requires triangle routing (HA to FA to MN) by default; optional but complex. | Built-in via Binding Updates to CNs, avoiding triangle routing. |

  • Encapsulation Headers:

    • IPv4: Original packet is encapsulated inside a new IPv4 packet. Outer header has HA as src, FA as dst; inner has CN as src, HoA as dst.

    • IPv6: Uses IPv6 Routing Header (Type 2). Outer header has CN as src, CoA as dst. Inner packet has CN as src, HoA as dst. No full encapsulation overhead.

3.2 TCP over Wireless Networks

• Challenges:

  • High Bit Error Rate (BER): Causes packet loss, misinterpreted as congestion by TCP.

  • Large/Latency & Variable Delay: Inflates RTT, slows congestion window growth.

  • Link Asymmetry: Downlink often faster than uplink; ACKs may be delayed.

  • Frequent Disconnections: Mobile handoffs cause session timeouts.

• Impact on TCP: TCP's congestion control (e.g., slow start, fast retransmit) and reliability (retransmission timeout) mechanisms are triggered by wireless losses, leading to unnecessary throughput degradation.

• Proposed Enhancements:

  • Explicit Loss Notification (ELN): Link layer informs TCP of non-congestion losses.

  • TCP SACK (Selective Acknowledgment): More efficient recovery from multiple packet losses.

  • Split Connection (e.g., I-TCP): Breaks connection at base station; uses different TCP variants over wireless and wired links.

  • TCP Westwood+: Estimates bandwidth from ACKs to set congestion window, more aggressive after wireless loss.

4.0 Routing in Infrastructure-less Networks

4.1 Ad Hoc Networks & Routing Protocol Classifications

• Proactive (Table-Driven) Protocols: e.g., DSDV (Destination-Sequenced Distance-Vector), OLSR (Optimized Link State Routing).

  • Mechanism: Each node maintains up-to-date routes to all other nodes by periodically exchanging routing tables (hello packets). Low latency for route setup, but high control overhead in dynamic networks.

• Reactive (On-Demand) Protocols: e.g., AODV (Ad-hoc On-demand Distance Vector), DSR (Dynamic Source Routing).

  • Mechanism: Routes are discovered only when needed via Route Request (RREQ) / Route Reply (RREP) flooding. Lower overhead in static networks, but high route discovery latency.

• Hybrid Protocols: e.g., ZRP (Zone Routing Protocol).

  • Mechanism: Combines both. Uses proactive routing within a local "zone" (e.g., 2-hop neighborhood) and reactive routing for destinations outside the zone. Aims to balance overhead and latency.

4.2 Mesh Networks & Multi-Hop Relay

• Concept of Multi-Hop Relay: A source node sends a packet to a destination via one or more intermediate relay nodes (hops), as nodes may be out of direct radio range.

• Significance in Mesh Networks:

  • Extended Coverage: Nodes can act as relays, extending network reach beyond a single hop.

  • Increased Reliability & Robustness: Multiple paths exist; if one node/link fails, traffic can be rerouted (self-healing).

  • Load Balancing: Traffic can be distributed across multiple paths.

  • Scalability: Can cover large areas without a single central point of failure.

• Relationship to Ad Hoc Routing: Mesh networks typically use ad hoc routing protocols (like proactive or reactive ones listed above) to establish and maintain these multi-hop paths dynamically.

5.0 Security in Mobile & Wireless Systems

5.1 Threat Landscape

• Denial of Service (DoS) / Distributed Denial of Service (DDoS):

  • Attack Vectors: Jamming (physical layer), exhausting battery/CPU, flooding routing protocols (e.g., AODV RREQ storms), exhausting authentication servers.

  • Impact: Deprives legitimate users of service, causes network congestion, drains mobile device resources (battery).

5.2 Security Models

• Primary Objectives of Military Security Models (CIA Triad +):

  1. Confidentiality: Preventing unauthorized disclosure of information.

  2. Integrity: Ensuring data is not altered improperly.

  3. Availability: Ensuring timely and reliable access to data/services.

  4. Authentication: Verifying identity of users/systems.

  5. Authorization: Granting access rights after authentication.

  6. Non-Repudiation: Preventing a party from denying an action.

• Role of Hierarchical Command Structures:

  • Enforces a centralized policy and chain of command for security decisions.

  • Defines clear levels of authority (e.g., Commander -> Officer -> Soldier) for access control and incident response.

  • Enables consistent enforcement of security rules across a large, distributed organization (e.g., military, large enterprise).

6.0 Application & Transaction Layer

6.1 E-commerce

• Definition: The buying and selling of goods or services, and the transmission of funds or data, over an electronic network, primarily the internet.

• Transformation of Traditional Business Models:

  • B2B (Business-to-Business): Streamlined supply chains, electronic marketplaces (e.g., Alibaba), just-in-time inventory.

  • B2C (Business-to-Consumer): Online retail (Amazon), 24/7 availability, global reach, personalized marketing.

  • C2C (Consumer-to-Consumer): Enabled by platforms (eBay, Facebook Marketplace), peer-to-peer sales.

  • Key Enablers: Secure payment gateways, shopping carts, web storefronts, logistics tracking, customer review systems.

6.2 Electronic Payment Systems

• Categories:

  • Card-Based: Credit/Debit cards via payment gateways (Visa, Mastercard).

  • Digital Wallets: Store payment info (PayPal, Apple Pay, Google Wallet) for one-click payments.

  • Cryptocurrencies: Decentralized digital currencies (Bitcoin, Ethereum) using blockchain.

• Mechanisms for Secure Transactions:

  • Encryption (SSL/TLS): Secures data in transit.

  • Authentication: Multi-factor authentication (password + OTP), biometrics.

  • Tokenization: Replaces sensitive card data with a unique token.

• Key Security Requirements:

  • Authentication: Verify parties involved.

  • Confidentiality: Encrypt transaction details.

  • Integrity: Ensure data isn't tampered with.

  • Non-Repudiation: Proof of transaction (digital signatures).

  • Availability: System must be accessible during transactions.