1. Introduction & Key Concepts

Wireless communication carries information through the air using electromagnetic waves (radio, infrared, microwave) without requiring physical conductors. It is everywhere — from your Bluetooth earbuds to satellite TV. This document groups technologies by typical range (short, medium, long) and explains real-world uses, pros/cons, security, and practical deployments.

Key terms

• Bandwidth: the maximum data rate possible (e.g., Mbps).
• Range: effective distance of communication.
• Latency: delay between sending and receiving data.
• Line-of-sight (LoS): unobstructed path between transmitter and receiver — needed for microwave & some satellite links.
• Frequency bands: e.g., 2.4 GHz, 5 GHz, UHF, VHF, L-band, Ku-band.
• Interference: unwanted signals that reduce performance.

2. Short-Range Technologies (0 — ~100 m)

Short-range tech targets personal & local-area connections. They’re lower-power, lower-cost, and optimized for convenience.

2.1 Bluetooth

Range: Class 2 ~10 m (common), Class 1 ~100 m. Frequency: 2.4 GHz ISM. Use-cases: earbuds, mice, smartwatches, car audio, sensor networks.

• Versions: Bluetooth Classic (audio), BLE (Bluetooth Low Energy) for sensors and IoT.
• Strengths: Low power, widespread support, simple pairing UX.
• Limitations: Limited throughput vs Wi‑Fi, potential congestion at 2.4 GHz.

Real-life: Your phone connects to an earpiece and a smartwatch using two separate Bluetooth profiles: A2DP for audio and GATT for fitness data.

2.2 Wi‑Fi (IEEE 802.11 family)

Range: Typical indoor 20–50 m; outdoor/line-of-sight up to 100+ m. Frequencies: 2.4 GHz and 5 GHz (also 6 GHz for Wi‑Fi 6E). Use-cases: home/office internet, hotspots, campus access points.

• Standards: 802.11n (Wi‑Fi 4), 802.11ac (Wi‑Fi 5), 802.11ax (Wi‑Fi 6/6E).
• Strengths: High throughput, flexible deployment, wide device support.
• Limitations: Interference in crowded bands, security misconfigurations.

2.3 NFC (Near Field Communication)

Range: < 10 cm. Use-cases: contactless payments, access cards, quick device pairing.

Real-life: Tap your phone at a store to pay using M-Pesa or contactless Visa/Mastercard.

2.4 Infrared (IR)

Range: a few meters; requires direct line-of-sight. Use-cases: TV remotes, some sensor-to-sensor links in industrial equipment.

2.5 UWB (Ultra Wideband)

Range: short (meters). Use-cases: precise indoor localization (centimeter-level), secure device unlocking, car keyless entry systems.

Short-range security tips

• Disable discoverable Bluetooth when not pairing.
• Use WPA3 or strong WPA2 passphrases on Wi‑Fi.
• Be cautious accepting NFC prompts; authenticate transactions on-screen.

3. Medium-Range Technologies (~100 m — ~10 km)

Medium-range tech bridges neighborhoods, campuses, and small towns — it is used by ISPs and mobile operators to extend access beyond a single building.

3.1 WiMAX (802.16)

Range: several kilometers (up to tens of km for LOS). Use-cases: last-mile ISP links, rural broadband.

Historically used where fiber wasn’t available; partly supplanted by LTE and fixed wireless access (FWA).

3.2 Cellular: 4G LTE & 5G (NR)

Range: Cell radius typically 1–10 km depending on frequency and environment. Use-cases: mobile internet, voice (VoLTE), enterprise backup links, IoT via NB‑IoT/Cat‑M.

• 4G (LTE): Good coverage, solid speeds (tens to hundreds of Mbps).
• 5G: Higher peak speeds, lower latency; uses mmWave for very high speed but short range; sub-6GHz for broader coverage.

3.3 Microwave point-to-point links

Range: 1–50 km line-of-sight. Use-cases: backbone links between towers, connecting a branch office to HQ, CCTV backhaul.

Microwave links carry a lot of traffic where fiber is too expensive or slow to deploy. They require careful alignment and clear LoS.

3.4 Fixed Wireless Access (FWA)

ISPs offer home internet using a rooftop antenna connected to a remote base station — effectively a medium-range wireless solution competing with DSL or fiber.

Deployment notes

• Site survey is critical: measure RSSI, check Fresnel zone clearance for microwave links.
• Regulatory: many medium-range bands require licensing or coordination with a national regulator.

4. Long-Range Technologies (~10 km — global)

Long-range tech provides national or global reach: satellite comms, HF radio, some cellular backhaul at scale.

4.1 Satellite communication

Types: GEO (geostationary), MEO (medium-earth), LEO (low-earth orbit). Use-cases: TV broadcast, maritime internet, remote connectivity, GPS.

• GEO: ~36,000 km altitude; constant position relative to Earth; higher latency (~500 ms round-trip).
• LEO: 500–2,000 km altitude (e.g., Starlink); lower latency, requires constellation.

Satellites are the choice for oceans, deserts, and anywhere fiber & towers can’t reach.

4.2 HF/VHF/UHF long-haul radio

HF: uses ionospheric propagation to reach thousands of kilometers (useful for international maritime/air comms and ham radio).

Emergency services and military still rely on HF when other infrastructure fails.

4.3 Wide-area cellular coverage (GSM/3G legacy)

Older 2G/3G systems provide voice and SMS across broad territories and can serve as fallback where LTE/5G isn't present.

Long-range realities

• Costs are generally higher (satellite subscriptions, terminal hardware, licensing).
• Latency varies: GEO high, LEO lower; choose based on application (VoIP vs broadcasting).

5. Comparison & How to Choose

Choice depends on:

• Required range and coverage
• Throughput (Mbps) and latency
• Reliability & availability
• Power & physical constraints
• Budget & regulatory environment

Quick selection guide

1. Short, personal: Wi‑Fi or Bluetooth.
2. Office building / campus: Wi‑Fi + wired backbone; consider microwave for building-to-building backhaul.
3. Rural last-mile: LTE/FWA or WiMAX or satellite.
4. Global / maritime / aviation: Satellite (LEO for interactive apps).

6. Security Considerations (Practical)

6.1 Common attacks & defenses

• Eavesdropping: Use encryption (WPA3, TLS, VPNs).
• Rogue APs / Evil Twin: Use 802.1X / certificates; educate users about authentic network names.
• Bluetooth attacks (bluesnarfing, bluebugging): Keep discoverability off, patch devices, use PINs.
• SIM swap & IMSI catchers: Use carrier protections, be alert to SMS/2FA changes, consider app-based 2FA.
• Physical tampering (microwave dishes, rooftop antennas): Secure mounts and use tamper-evident seals.

6.2 Hardening an access point / small network

• Use strong encryption (WPA2-Enterprise or WPA3) with RADIUS for business Wi‑Fi.
• Segment guest networks and enforce client isolation for public hotspots.
• Apply firmware updates on routers and APs; change default admin passwords.
• Monitor logs for unusual associations, MAC spoofing, or bandwidth spikes.

7. Practical Deployment Examples (Real-life, vivid)

Example A — A small town ISP

Scenario: Town X has no fiber. ISP mounts a microwave link to the nearest fiber POP (point of presence) 20 km away. A local tower holds a sector antenna providing LTE-FWA to households. Households receive a small rooftop CPE (customer-premise equipment) that connects via Ethernet to a Wi‑Fi router inside the home.

Devices involved: microwave radios, tower sectors, small CPEs, household Wi‑Fi routers.

Example B — School campus (ATC style)

Scenario: Arusha Technical College needs campus-wide internet. They install a fiber ring between buildings; each building has an AP controller and multiple APs (2.4/5 GHz). Lecture halls use high-gain directional antennas to serve many students. A separate SSID and captive portal handle guest access.

Example C — Mobile money in rural shops

Shops rely on GSM/2G or 3G for USSD and M-Pesa transactions. Where 3G/4G exists, richer apps and QR payments are available. For resilience, critical points may have a UPS and a backup 2G dongle if power or 4G fails.

Example D — Emergency communications

During an outage, emergency teams may deploy HF/VHF radios, portable Wi‑Fi mesh, and satellite terminals to restore voice and data for coordination.

8. Practical Labs, Tools & Commands

Hands-on labs to practice—suitable for an ICT lab session.

Lab 1 — Wi‑Fi discovery & mapping (Linux)

1. Use iwconfig and iwlist scan to list APs.
2. Use airmon-ng to enable monitor mode and airodump-ng to capture beacons (educational purpose only on your own network).
3. Use nmcli dev wifi list on systems with NetworkManager.

Lab 2 — Bluetooth scanning

1. sudo bluetoothctl then scan on to discover nearby devices.
2. Practice pairing and unpairing devices securely.

Lab 3 — Basic microwave link design checklist

• Determine line-of-sight and Fresnel zone clearance.
• Measure distance and select frequency band and antenna gain.
• Plan redundancy & power backup (solar/UPS).

9. How This Knowledge Helps You (Study & Career)

• Network engineering: design, deploy, and maintain wireless infrastructure.
• Cybersecurity: secure wireless networks, detect attacks, and conduct audits.
• IoT & embedded systems: choose protocols (BLE, LoRaWAN, NB‑IoT) suitable for power and range.
• Entrepreneurship: build local ISPs or managed Wi‑Fi services for businesses.
• Everyday life: better troubleshoot your home internet, secure your devices, and make informed purchases.

Study tips: Combine theory with lab work—set up a small home lab with a second-hand AP and a Raspberry Pi to practice.