Starlink in Iran: How the regime jams the service and what helps against it

The situation in Iran has been escalating since early January. What began as demonstrations by business people at the end of December, expressing their anger over the poor economic situation, has developed into mass protests that the Iranian regime is brutally suppressing. Thousands of deaths are now being reported. The aim is to prevent as many images and news as possible from reaching the public, which is why the Iranian government is blocking communication networks.

Reliable information is challenging to come by, as practically the entire country has been offline since the evening of January 8; the content delivery network Cloudflare registers almost no more data traffic from Iran, and the internet observation group Netblocks also speaks of a complete communication blockade.

One of the few digital ways out currently leads via satellite through the global network Starlink by SpaceX. Although usage is forbidden in Iran, terminals are smuggled into the country, and SpaceX tolerates their use; since January 13, it has even been free of charge. However, activists are reporting that Starlink is also functioning increasingly poorly in Iran, and users are being actively tracked. But how can a system of thousands of satellites be jammed from the ground, and how does the regime find users of the devices without access to customer data or the network?

• Starlink is illegal in Iran, but terminals are smuggled into the country.
• The radio connection from space to the terminal can be easily jammed.
• The Starlink constellation now consists of over 9,000 satellites.

The US organization Holistic Resilience, which helps Iranians secure their internet access, speaks of around 50,000 users in the country. In this article, we will explore how Starlink works, why it functions in Iran, and how the Iranian government is likely jamming the network. While neither the regime nor SpaceX likes to reveal their cards, hackers and journalists are not deterred by this, and the laws of physics apply to everyone.

Orbit Network

Starlink is a satellite constellation built by SpaceX in low Earth orbit (LEO) to provide internet access. The primary goal of tech billionaire and SpaceX founder Elon Musk: fast, low-latency, and affordable internet access for remote regions of the world, wherever other access methods fail or are not economically viable. Developed since 2015, launched into orbit since 2019, and available for private customers since 2021, the network now has over 9 million paying customers. It is also the largest satellite network in the world to date, with around 9,500 active satellites, which now constitute the majority of man-made objects in Earth orbit. In Germany, Starlink currently charges 50 euros per month for stationary use without volume limits. The monthly tariff for the portable Starlink terminal, which serves motorhomes for example, is pricier.

Internet access via satellite is not new and has been available via geostationary satellites since the early 2000s. Due to its low orbit of around 550 kilometers, Starlink can deliver significantly better results compared to these: Instead of around 120 milliseconds of signal transit time for 35,800 kilometers (geosynchronous orbit), it is only about 2 milliseconds with Starlink.

Furthermore, customers are distributed across numerous satellites, each of which has up to 48 separate spot beams, resulting in better reception and thus higher data rates. Typical private customers with stationary terminals can expect between 150 and 400 Mbit/s downlink and 10 to 50 Mbit/s uplink data rates with 25 to 100 milliseconds latency. This is a significant improvement over the 50 to 100 Mbit/s downlink rate, 600 millisecond latency, and often limited data volume of geostationary offerings.

For this to work optimally, the user must set up the satellite modem in a location with at least 100 degrees of clear view of the sky. Currently, there is the standard set for stationary home users, the Mini for on-the-go use, the Mini X with an additional Mini router, and Performance and Enterprise models for business customers. There are also several special versions for more demanding scenarios, such as maritime and aviation applications.

Tracking without Movement

Starlink uses frequencies between 10.7 and 14.5 GHz (in the so-called Ku-band) for communication between the satellite and the customer antenna, as well as blocks between 17.8 and 30 GHz for communication between the ground station and the satellite. These short wavelengths exhibit high path loss, so directional antennas are always necessary for long distances. At the same time, SpaceX has no other choice, because anyone who wants to supply many customers with high data rates needs broad frequency blocks. The transmission frequencies of digital satellite television DVB-S2 are also in the Ku-band.

To enable the service in its quality and simplicity, SpaceX has made phased array antennas suitable for mass production, both for its satellites and for the customer satellite modems. Such antennas are, in rough terms, electronically steerable directional antennas without moving parts. They consist of numerous small antenna elements that are dynamically controlled and synchronized in groups.

A simple phased array was developed as early as 1905 and consists of three radiators whose arrangement forms an equilateral triangle with a side length of slightly more than a quarter wavelength. Operated individually, each radiator is omnidirectional, radiating equally in all directions and receiving signals equally well from all directions. However, if fed in parallel at two radiators at the base in a triangular arrangement, and the radiator at the apex via a phase delay line a quarter wavelength later, the array gains the characteristic of a directional antenna. It has a preferred direction towards the apex and base of the triangle. If the delay line is connected to one of the other radiators, the preferred direction of the array also changes accordingly by 60 degrees.

By drastically increasing the number of antenna elements – Starlink terminals are said to have up to 1500 – both antenna performance and beamforming can be increased dynamically during operation. The principle is therefore the key to Starlink's success and is used both from the satellite to the ground and in the reverse direction; both try to direct their transmissions as precisely as possible towards each other.

Unlike satellite dishes, as known from satellite television, with phased arrays in Starlink terminals, it is no longer important to precisely align the antenna with a satellite: the receiving unit simply adjusts the preferred direction of the array until it receives the satellite as well as possible, and vice versa. By continuously readjusting, it can keep the satellite in view until the next Starlink satellite takes over and the array is adjusted to it.

The first two versions of the Starlink "dishes" did have motors for alignment, but these were only for initial positioning, not for active tracking of the antenna to the currently used satellite. Nowadays, alignment is only necessary for optimal results; due to the large number of satellites, Starlink has been working for some time in any orientation towards the sky and also in motion (car, boat, aircraft, etc.).