What are Satellite Phones?

Jul 3, 2023

A satellite phone, also known as a sat phone, is a mobile communication device that allows users to establish communication links through satellites orbiting the Earth. Unlike conventional cellular phones which rely only on ground-based towers, satellite phones utilize satellites to facilitate communication over vast distances, including remote areas, oceans, deserts, and other locations where terrestrial networks are absent. Satellite phones play a vital role in providing communication services in areas where traditional cellular networks are unavailable. Some of the most prominent satellite phone networks are Iridium, Inmarsat, and Global Star, etc.

Satellite phones can also support text messaging and data services, though speeds are considerably slower compared to traditional networks. Texting is generally straightforward and similar to regular cell phones. Data speeds for satellite phones are typically limited to around 10 kilobits per second, making tasks like checking emails feasible but not suitable for bandwidth-intensive activities. Some networks also offer separate devices, such as the IsatHub from Inmarsat, which can act as Wi-Fi hotspots and provide speeds of up to 300 kbps.

Calling a satellite phone from a regular phone is considered an international call, and costs vary depending on the phone provider. Some satellite phone users can opt for a local telephone number connected to their satellite phone, simplifying the calling process for others. However, it is important to check with the phone company as some cellular providers may block calls to satellite phones by default. Satellite phone companies represent significant advancements in satellite communication technology, offering global coverage and voice-carrying capabilities. These systems have attracted substantial investments and consortiums of companies aiming to revolutionize the field of telecommunications.

Types of Satellite Phone Systems

Geostationary Orbit (GEO) Satellite Phones: Geosynchronous satellites are fixed in a single position above the Earth's equator at an altitude of over 36,000 kilometers, providing coverage over a larger area. These satellites remain fixed relative to the Earth's surface, allowing continuous communication coverage within a particular geographic region.

Low Earth Orbit (LEO) Satellite Phones: LEO satellite phones use a network of satellites that orbit the Earth at much lower altitudes, typically between 400 and 700 kilometers. LEO satellites provide better coverage, sound quality, and lower delays compared to geosynchronous satellites. LEO satellites move at high speeds relative to the Earth's surface, enabling them to provide global coverage by handing off communication signals between satellites as they traverse the sky. LEO satellite systems require a larger number of satellites to ensure coverage over most of the Earth's surface. These satellites move at high speeds, completing an orbit in around two hours. The low altitude of LEO satellites allows for reliable service in various regions, including remote areas like Antarctica. While LEO satellite systems offer advantages such as superior call quality and lower power consumption, their data transmission speeds are slower compared to geosynchronous systems. This means that activities like streaming videos may not be feasible with LEO satellite connections.

For optimal service, satellite phones require a clear line of sight to the satellite. This means that if you are indoors or in an obstructed area, you may need to step outside to make a call. In dense forests or mountainous regions, geosynchronous satellite systems may face line-of-sight challenges, whereas LEO satellite systems offer repeated opportunities to connect as satellites pass overhead.

How Does a Satellite Phone Work?

Satellite phones work by connecting to communication satellites positioned in geostationary orbit or low Earth orbit (LEO). The work is as follows:

  • User Initiates a Call or Message: When a user dials a number or sends a message from a satellite phone, the device converts the audio or text into digital signals.
  • Signal Transmission: The digital signals are transmitted through the satellite phone's antenna to the nearest satellite in view. The antenna must have a clear line of sight to the satellite to establish a connection.
  • Satellite Relay: The satellite acts as a relay station, receiving the signals from the user and then relaying them back to Earth.
  • Ground Station: The signals received by the satellite are transmitted to a ground station or telecommunication hub on Earth. These ground stations are equipped with large antennas and advanced equipment to handle high-frequency satellite signals.
  • Satellite Network: From the ground station, the signals are forwarded to the satellite network's gateway, which acts as the interface between the satellite and the public switched telephone network (PSTN) or the internet.
  • Connection Establishment: The satellite network establishes a connection with the recipient's phone number or internet protocol (IP) address, enabling seamless communication between the satellite phone user and the recipient.
  • Communication Flow: Once the connection is established, voice calls or data transfers between the two parties can take place in real-time as if using a conventional phone or internet service.

Benefits of Satellite Phones

  • Global Coverage: Satellite phones can operate virtually anywhere on Earth, ensuring communication in remote or disaster-stricken regions.
  • Independent from Terrestrial Infrastructure: They are not reliant on cellular towers or ground-based networks, making them ideal for areas with limited or no terrestrial coverage.
  • Emergency Communication: Satellite phones serve as essential tools during emergencies or natural disasters when traditional communication infrastructure may be disrupted. Satellite phones offer a crucial communication option in areas with limited or no cellular coverage, providing connectivity in remote regions and during emergencies.
  • They are more resilient and durable compared to regular cell phones, making them suitable for use in extreme conditions or by search and rescue agencies. Satellite phones also provide secure communication, which can be important for government authorities and security agencies.