When and How to use Satellite Connectivity for Raspberry Pi IoT

Step 1: Choose the satellite network provider

Choosing the satellite connectivity provider is crucial step and it is determined by factors such as price, coverage and usecase. To be able to connect Raspberry Pi to satellite network, it is necessary to obtain subscription to a data plan. Ensure the plan covers the expected data usage and provides the necessary credentials (SIM card, activation, etc.).

Below is the summary of some of the well known providers:

Iridium Satellite Network

Coverage:

• Global Coverage: Iridium offers truly global coverage, including the poles, oceans, and airways. This is because Iridium satellites are in low Earth orbit (LEO) and are arranged in a polar orbit, which ensures that there is always at least one satellite overhead anywhere on Earth.

Key Features:

• LEO Satellites: The network consists of 66 active satellites plus spares, which orbit at an altitude of approximately 780 kilometers (485 miles).
• Low Latency: The low orbit altitude results in lower latency compared to higher orbit satellites.
• Continuous Coverage: With overlapping footprints, Iridium provides continuous coverage even in remote and polar regions.

Globalstar Satellite Network

Coverage:

• Regional Coverage: Globalstar provides coverage primarily in North America, Europe, Northern Asia, parts of South America, and Australia. The coverage is not as comprehensive as Iridium's, with some gaps in polar and oceanic regions.

Key Features:

• LEO Satellites: Globalstar's constellation consists of 24 active LEO satellites orbiting at an altitude of approximately 1,414 kilometers (879 miles).
• Focus on Terrestrial Use: Designed more for terrestrial and coastal use, particularly in areas with significant population centers.
• Lower Cost: Generally lower cost for hardware and services compared to other satellite networks.

Inmarsat Satellite Network

Coverage:

• Global Coverage (Excluding Polar Regions): Inmarsat provides near-global coverage with the exception of the extreme polar regions. Its geostationary satellites cover the majority of the Earth's surface, making it suitable for most remote applications.

Key Features:

• Geostationary Orbit (GEO): Inmarsat operates 14 geostationary satellites that stay fixed over a particular point on the Earth's equator at an altitude of approximately 35,786 kilometers (22,236 miles).
• Higher Bandwidth: Supports higher bandwidth and data rates compared to LEO satellites, making it suitable for applications requiring significant data throughput such as video streaming.
• Specialized Services: Offers specialized services like Broadband Global Area Network (BGAN) for high-speed internet connectivity.

Step 2: Choose the compatible satellite modem

While there are other possibilities, simplest solution is to choose modem compatible with the satellite data plan. Below are some of the well known modems from each of the providers we described earlier:

Iridium Modems:

• Iridium 9602/9603: These modems offer global coverage and support short-burst data (SBD) communications. Ideal for simple messaging and tracking applications.
  • Features: Small size, low power consumption, global coverage.
  • Use Cases: Asset tracking, environmental monitoring.

Globalstar Modems:

• Globalstar STX3: Known for its low power consumption and small form factor, suitable for IoT devices requiring intermittent data transmissions.
  • Features: Low cost, efficient power usage, limited to regions with Globalstar coverage.
  • Use Cases: Remote sensing, telemetry.

Inmarsat Modems:

• Inmarsat BGAN (Broadband Global Area Network): Provides higher bandwidth suitable for more data-intensive applications, including real-time video streaming and large data transfers.
  • Features: Higher data rates, reliable connection, more power-hungry.
  • Use Cases: Disaster response, remote field operations.

Step 3: Connect the satellite modem to Raspberry Pi

Modems typically come in two flavors. USB modem can be directly connected to one of the USB ports on Raspberry Pi whereas Serial Modem needs USB-to-Serial adapter to connect via RS232/TTL.