Lesson 8: Satellite Communications

Satellite communications is a high-growth niche in telecommunications, especially with the rise of LEO mega-constellations like Starlink, Amazon Kuiper, and OneWeb. It enables global broadband, backhaul for 5G, direct-to-device connectivity, maritime/aviation comms, and integration with NTN (Non-Terrestrial Networks) in 5G/6G standards.

Why Satellite Communications Matters

Provides coverage where terrestrial networks cannot reach (oceans, deserts, remote areas, disaster zones)
Rapid deployment for emergency response and rural connectivity
Low-latency LEO systems now compete with fiber in many use cases (20–50 ms RTT)
Growing role in 5G/6G NTN and mobile backhaul
Increasing demand for satellite engineers in operators, vendors, and space-tech companies

1. Satellite Orbits

Orbit Type	Altitude	Latency (RTT)	Coverage per Satellite	Number of Satellites Needed	Key Use Cases
GEO	~35,786 km	500–700 ms	~1/3 of Earth	3–4	TV broadcast, traditional VSAT, maritime
MEO	8,000–20,000 km	100–150 ms	Regional/global	Dozens	High-throughput backhaul, aviation
LEO	300–2,000 km	20–50 ms	Small footprint	Thousands	Broadband internet, IoT, D2D

GEO vs MEO vs LEO Coverage & Latency Comparison

(Replace with actual image path or URL in your repo: e.g., images/orbits-comparison.png)

Typical LEO Constellation Layout

(images/leo-constellation.png)

LEO Satellite Visibility Geometry

(images/leo-visibility-geometry.png)

2. Link Budget – The Most Important Calculation

The link budget determines whether communication is possible by balancing transmitted power, gains, and all losses.

Basic Link Budget Equation (in dB): Received Power (dBm) = Tx Power + Tx Antenna Gain – Tx Losses – FSPL – Atmospheric Losses + Rx Antenna Gain – Rx Losses + Other Gains

Key terms:

EIRP = Tx Power + Tx Antenna Gain
FSPL (Free Space Path Loss) = 20 log₁₀(d) + 20 log₁₀(f) + 147.55 (d in km, f in GHz)
- GEO at Ku/Ka band: ~190–205 dB
- LEO at 12 GHz: ~140–160 dB
G/T = Rx antenna gain / system noise temperature
Rain fade, gaseous absorption, scintillation (especially >10 GHz)
Margin: typically 3–10 dB

Example Satellite Link Budget Waterfall

(images/link-budget-waterfall.png)

Typical Gains/Losses Breakdown

(images/link-budget-components.png)

3. VSAT (Very Small Aperture Terminal)

Traditional fixed satellite access using small dishes (0.6–2.4 m).

Components:

Outdoor Unit (ODU): Parabolic dish + LNB (receive) + BUC (transmit)
Indoor Unit (IDU): Satellite modem/router
Hub/Gateway: Central station for traffic aggregation

Classic VSAT Terminal

(images/classic-vsat-dish.png)

Modern Maritime/Convertible VSAT

(images/maritime-vsat-antenna.png)

4. Modern Satellite Internet – Starlink & Beyond

Starlink (SpaceX) – Leading LEO broadband constellation in 2026:

7,000 satellites in orbit
Laser inter-satellite links (ISL) for global routing
User terminal: Flat phased-array antenna (“Dishy”) – no moving parts
Performance: 100–300+ Mbps down / 20–50 Mbps up, 20–40 ms latency
Direct-to-cell capability (for unmodified phones in remote areas)

Starlink User Terminal (Gen 2 / Gen 3)

(images/starlink-dish-gen3.png)

Starlink Portable Kit Comparison

(images/starlink-dish-comparison.png)

Key Takeaways

LEO constellations revolutionized satellite broadband with low latency and high capacity
Link budget engineering is the foundation of satellite system design
Phased-array antennas replaced mechanical dishes for user terminals
Satellite now plays a growing role in 5G NTN, rural connectivity, and mobile backhaul

This lesson completes the physical-layer and access-network part of the telecom roadmap — next we move into the essential tools every telecom engineer must master.