Researchers have developed a technique that allows low Earth orbit satellite antennas to handle signals for multiple users simultaneously, thereby reducing costs and simplifying the designs of communication satellites.
Low-orbit satellites may soon provide high-speed communication to millions around the globe, yet their capabilities have been limited by a technological constraint—each antenna array can only connect with one user at a time.
This one-to-one communication means companies typically must either deploy numerous satellites in a constellation or build large singular satellites equipped with multiple antenna arrays for broad coverage. Both methods are costly, complex, and risk creating overcrowded orbits.
For instance, SpaceX has opted for the “constellation” approach with its StarLink network, which currently includes over 6,000 satellites in low-Earth orbit, more than half of which launched in the last few years. SpaceX plans to add tens of thousands more satellites in the upcoming years.
Now, a team of researchers from Princeton University and Yang Ming Chiao Tung University in Taiwan has devised a method that allows low-orbit satellite antennas to support multiple user signals at the same time, significantly lessening the amount of hardware required.
In a paper published on June 27 in IEEE Transactions on Signal Processing, the researchers outline how they tackled the single-user limitation. Their method is based on a well-known technique that enhances communication by placing antenna arrays in a way that directs radio wave beams precisely where they are needed. Each beam transmits information, such as texts or phone calls, as signals. While antenna arrays on ground-based structures like cell towers can manage numerous signals within a single beam, low-orbit satellites are restricted to one.
The rapid speed of the satellites, which travel at 20,000 miles per hour and are constantly changing their positions, makes it challenging to handle multiple signals without causing interference.
“For a cell tower to communicate with a car moving at 60 miles per hour, relative to the data exchange speed, the car doesn’t move much,” said co-author H. Vincent Poor, a professor in Electrical and Computer Engineering at Princeton. “But these satellites are moving so quickly that their positional information changes rapidly.”
To address this challenge, the researchers have created a system that allows a single antenna array to effectively split its transmissions into multiple beams without needing additional hardware. This innovation enables satellites to surpass the single-user limitation associated with each antenna array.
Co-author Shang-Ho (Lawrence) Tsai, an electrical engineering professor at Yang Ming Chiao Tung University, likened the technology to shining different beams from a single flashlight without using multiple bulbs. “Now, we only need one bulb,” he explained. “This can lead to significant reductions in both cost and power usage.”
A network that utilizes fewer antennas could result in a need for fewer satellites or the creation of smaller satellites, or both. “A standard low Earth orbit satellite network might require 70 to 80 satellites to cover the United States alone,” Tsai noted. “With this new technique, that number could drop to around 16.”
The researchers believe this new method could easily be integrated into already constructed satellites, according to Poor. “A major advantage is that you can design a more straightforward satellite,” he stated.
Implications for Space
Low-orbit satellites operate in the lower part of Earth’s atmosphere, positioned between 100 and 1,200 miles above the surface. This area offers limited space; more objects in orbit increase the chances of collisions, which can break apart satellite debris that poses further risks to other satellites.
“The primary concern isn’t just the risk of being struck by a falling satellite,” Poor stated, “but rather the long-term health of the atmosphere and the increasing cloud of space debris, which can lead to serious issues.”
With the low-orbit satellite sector expanding quickly, as companies like Amazon and OneWeb deploy their own satellite networks for internet access, this new technique could significantly lower the potential hazards in space.
Poor mentioned that although this study remains theoretical, the potential efficiency improvements are substantial. “This paper is all rooted in mathematics,” he noted. “In this particular field, theoretical studies often yield accurate predictions.”
Since the paper’s publication, Tsai has begun conducting field tests using underground antennas to validate the mathematical model. “The next step is to apply this method to an actual satellite and get it launched into space,” he added.
