Wireless & Mobile Networks: Tech, Protocols & Business Apps

Key Concepts & Technologies

Wireless Communication Basics

Wireless communication transmits data without physical cables using electromagnetic waves (radio, microwave, infrared). Key components:

• Transmitter: Converts data into signals (e.g., router, smartphone).
• Medium: Air (radio waves, microwaves).
• Receiver: Decodes signals (e.g., laptop, IoT device).

graph TD
  A["Wireless Communication"] --> B["Components"]
  A --> C["Types"]
  A --> D["Challenges"]
  B --> B1["Transmitter: Router/Smartphone"]
  B --> B2["Medium: Air (Radio/Microwave Waves)"]
  B --> B3["Receiver: Laptop/IoT Device"]
  C --> C1["Wi-Fi: IEEE 802.11 (Local Area)"]
  C --> C2["Bluetooth: Short-range (IoT, Headsets)"]
  C --> C3["Cellular: GSM/5G (Wide Area)"]
  D --> D1["Interference: Signal Overlap"]
  D --> D2["Latency: Delay in Data Transfer"]
  D --> D3["Security: Encryption Needed"]

A typical home Wi-Fi router showing antennas, Ethernet ports, and LED indicators. (Image: Syced, CC0, via Wikimedia Commons)

Wi-Fi (IEEE 802.11 Standards)

Wi-Fi uses radio waves (2.4 GHz/5 GHz) for local area networking. Key standards:

Worked Example: eSewa Wi-Fi Login When you log in to eSewa via Wi-Fi at a café:

1. Your phone sends a probe request to nearby access points (APs).
2. The café’s AP (e.g., TP-Link Archer C7) responds with its SSID (eSewa_Cafe).
3. You authenticate via WPA3-Enterprise (secure encryption).
4. Data travels via 802.11ac (5 GHz) to the café’s router, then to eSewa’s server.

Bluetooth & Near-Field Communication (NFC)

• Bluetooth: Short-range (10m), low power (used in Khalti QR payments, wireless headsets).
• NFC: Ultra-short range (<10 cm), used in contactless cards (e.g., Nepal Rastra Bank’s digital wallets).

flowchart TD
  A["Bluetooth Device\n(e.g., Headset)"] -->|"Pairing"| B["Smartphone\n(Bluetooth Module)"]
  B -->|"Data Transfer"| C["Audio/Files\n(2.1 Mbps)"]
  D["NFC Tag\n(e.g., Payment Card)"] -->|"Tap"| E["POS Terminal\n(NFC Reader)"]
  E -->|"Transaction"| F["Bank Server\n(Encrypted)"]

Cellular Networks (GSM to 5G)

Cellular networks use frequency bands divided into cells (each served by a base station). Evolution:

Worked Example: Pathao Driver’s 4G Connection

1. A Pathao driver’s phone connects to a 4G LTE base station (e.g., Nepal Telecom’s 1800 MHz tower).
2. The phone sends GPS coordinates via TCP/IP to Pathao’s server.
3. The server matches the driver with a nearby rider using geohashing.
4. Real-time updates (e.g., "30 seconds away") use WebSockets for low latency.

Wireless Security Threats & Solutions

Real-World Case: Ncell’s 4G Security Ncell uses:

• AES-256 encryption for voice/data.
• SIM card authentication (GSM’s A3/A8 algorithm).
• Deep packet inspection to block malicious traffic.

Mobile Network Architectures

Two main architectures:

1. Client-Server (Internet): Devices (clients) connect to centralized servers (e.g., eSewa’s backend).
2. Peer-to-Peer (P2P): Devices communicate directly (e.g., WhatsApp calls via WebRTC).

graph TD
  subgraph Client-Server
    A[Client Device
    (e.g., Smartphone)] -->|"HTTP/HTTPS"| B[Server
    (e.g., eSewa Backend)]
  end
  subgraph Peer-to-Peer
    C[Peer 1
    (e.g., WhatsApp User)] -->|"WebRTC"| D[Peer 2
    (e.g., WhatsApp User)]
  end

A P2P network showing direct device communication. (Image: Anselm Vollprecht (cite source: „Und jetzt zus@mmen. Dein Ei, CC BY-SA 4.0, via Wikimedia Commons)

Wireless Applications in Nepal

Exam Tip

1. Compare Wi-Fi vs. Cellular: Focus on range, speed, and use cases (e.g., Wi-Fi for LAN, 5G for IoT).
2. Security: Always mention encryption (WPA3, AES) and authentication (802.1X, SIM cards).
3. Real-World Scenarios: Link theories to eSewa, Khalti, or NTC (e.g., "How does Pathao use 4G for low-latency updates?").
4. Diagrams: Draw OSI layer traces for wireless (e.g., Wi-Fi at Data Link/Physical layers).
5. Shortcomings: Know limitations (e.g., Bluetooth’s range, 5G’s high cost).

In the Real World

1. eSewa’s Wi-Fi Login: Uses 802.11ac for secure authentication at cyber cafés. If the café’s AP is misconfigured (e.g., WEP instead of WPA3), hackers can intercept login credentials via packet sniffing.
2. Khalti’s NFC Payments: When you tap your phone on a Daraz kiosk, the NFC chip in your phone securely transmits payment details to the merchant’s terminal using EMVCo standards. This avoids manual PIN entry, reducing fraud.
3. NTC’s 5G Pilot in Kathmandu: NTC’s 5G testbed in Thapathali uses beamforming to direct signals to specific devices (e.g., a smart traffic light). This reduces interference and improves latency for real-time data from sensors.

Case Study: Daraz’s Mobile Supply Chain Daraz uses wireless networks for:

• Warehouse IoT: LoRaWAN tracks inventory in real time (low-power, long-range).
• Driver Tracking: 4G LTE-M updates delivery status to customers.
• Customer Support: Wi-Fi Direct enables instant file sharing for returns.

graph TD
  subgraph Daraz Systems
    A[LoRaWAN Sensors
    (Warehouse)] -->|"Inventory Data"| B[Cloud Server
    (AWS)]
    C[4G LTE-M
    (Driver Device)] -->|"GPS/Status"| D[Customer App
    (WebSockets)]
    E[Customer Device
    (Wi-Fi/4G)] -->|"Return Request"| F[Support Agent
    (VoIP)]
  end