Subspace radio is a technique for performing faster than light communication. It is a bit of a misnomer as it often does not use radio signals. It also doesn't use subspace, though the techniques are closely related. Regardless, this form of communication can be one of the most reliable and secure methods of communication over interstellar distances currently known.
How fast that communication is, however, depends entirely on how deep into the subspace bands your equipment can tunnel. A major station with a dedicated subspace array can hold a real-time video call across thousands of light years. A freighter captain on the fringe? She's sending text messages and hoping for a reply sometime this week.
The first problem one encounters once subspace travel becomes a thing is the lag time in communication. Even very short hops in subspace can lead to days or weeks of lag time in communications. Because of this, most species arrive at the same solution to the problem; why not use the same technology they just invented to move themselves vast distances to move data the same way?
Most forms of communication are electromagnetic in nature, meaning they are already moving at the speed of light, in a "massless" form. This has the advantage of making the energy requirements significantly less demanding than moving a ship. But, unlike a ship, it's not really possible to create a pocket that moves with the signal like a subspace pocket moves with the ship that generates it. Instead, space-time between the transmitter and receiver is warped to shorten the distance between them. At this point, any "real time" form of communication can be utilized.
This form of space-time manipulation is known as tunneling. It works best with waves or near-massless particles.
The speed of a subspace radio transmission is determined by how deep into the subspace bands the tunnel reaches. The same band structure that governs FTL travel applies to communications — Alpha band tunneling is barely faster than lightspeed, while Epsilon or Zeta band depth approaches real-time across interstellar distances.
The critical difference from ship travel is that you're not moving mass through the tunnel. The energy requirements are significantly lower, but they still scale with depth. Pushing a tunnel into the deeper bands requires proportionally more powerful subspace arrays, better graviton generators, and more sophisticated software to maintain tunnel stability over the duration of the transmission.
The tunnel itself is the bottleneck. A text message needs milliseconds of tunnel time — burst it through and collapse the tunnel. A sustained voice call requires holding the tunnel open. A high-definition video stream requires holding a deep, stable tunnel for the entire duration of the conversation.
This means lower-bandwidth communication is almost always faster and cheaper. A text message can be routed through deeper bands than a video call on the same equipment, simply because it needs so much less tunnel time. This is why most interstellar communication — even between well-connected systems — defaults to text and short recorded messages rather than real-time calls. It's not that the call is impossible; it's that the infrastructure cost of holding a deep tunnel open for a casual chat is absurd.
Subspace radio capabilities vary enormously depending on the equipment available. In practice, interstellar communication operates in tiers.
Large stations and wealthy planets maintain dedicated subspace communication arrays — massive installations capable of tunneling into the Epsilon band and deeper. These arrays can sustain real-time voice and video across thousands of light years, and handle enormous data throughput for GalNet synchronization.
Station-to-station deep-band links form the backbone of interstellar communication, often called the "fast network." This is the infrastructure that GalNet runs on. Getting your signal routed through the fast network versus a direct shallow-band tunnel is the difference between seconds and days.
Not all deep-band communication hardware sits on stations. Logistics ships, exploration vessels, and some specially modified ships carry GalNet nodes — subspace arrays powerful enough to tunnel into the deep bands and connect directly to the fast network.
Logistics and supply ships need them to coordinate fleet operations across vast distances. Exploration ships need them because they operate on the frontier, far from any station infrastructure, and still need to report back. And then there are the modified vessels — aftermarket or custom installations, expensive and power-hungry, but invaluable. Intelligence ships, wealthy Freelancer captains, and certain less-than-legitimate operations all find reasons to invest in deep-band comms capability.
These ships effectively become mobile relay points. Nearby vessels with weaker radios can route their signals through a GalNet node ship rather than trying to tunnel on their own, which is why fleet logistics ships are so critical to military operations — lose your logistics train and you don't just lose supplies, you lose communications.
Most ships can manage Alpha or Beta band depth for communications. That's good enough for near real-time communication within a system or to nearby systems, but over longer distances the lag adds up fast — hours, days, or even weeks depending on how far the signal has to travel.
Ship captains learn to work within these constraints. Short text messages and recorded voice clips are the norm. Real-time calls are reserved for nearby contacts or emergencies where the power draw is justified. Many experienced spacers develop a habit of front-loading their messages with the important information, because by the time a reply comes back, the situation may have changed entirely.
Small colonies and remote outposts often have limited subspace radio capability — barely scratching Alpha band, if they have subspace equipment at all. Communication with the wider galaxy can lag by days or weeks. Most fringe settlements receive periodic GalNet data dumps from passing ships rather than maintaining a continuous connection.
Some don't even bother with subspace radio, relying instead on ships physically carrying data in and out. It's slow, but it's reliable, and it doesn't require expensive equipment that nobody on the colony knows how to maintain.
Subspace radio is often used as a point to point communication system. If you know your destination, you can tunnel from your current location to the destination, and then establish a secure form of communication such as a point to point laser system. The resulting communication will be almost impossible to intercept. Most military communications work like this.
Unfortunately, 'nearly impossible to intercept' does not also mean 'nearly impossible to detect'. When using point to point subspace radio (P2PSR) it's possible to detect both the origin and destination of the communication. At the very least, that tunneling is happening is often easily detected. This can lead to detection of otherwise hidden forces simply by their communications.
This is why most secure communications use a network of redundant repeater stations. While they can add lag, repeaters also make it much more difficult to track down the destination point of a message.
Repeaters serve a second, equally important function: they bridge the gap between shallow-band and deep-band infrastructure. A ship that can only tunnel to Alpha band can reach a nearby repeater, which then relays the signal through deep-band station-to-station links. The message travels the vast majority of its journey on the fast network, even though the sender's equipment could never reach those depths directly. This is how most civilian communication actually works — not by tunneling directly to the destination, but by reaching the nearest node on the fast network and letting the infrastructure do the heavy lifting.
Another technique is what's called a "subspace broadcast". It's possible to tunnel to a nearby location and let the final leg of communication happen at normal lightspeed, over a wide-band radio frequency. This is often more useful for one way rather than two way communication. It is very useful when either the exact destination is unknown, or there's a desire to obfuscate the exact destination.
The original version of this page treated subspace radio as essentially instant for everyone, which conflicted with the eventual-consistency model of GalNet and the general feel of the setting. The band depth model ties communication speed directly into the existing subspace band structure, creating a natural tiered system where infrastructure and money determine how connected you are — which is way more interesting from a storytelling perspective.
The "fast network" concept gives us a backbone that explains how GalNet works without requiring magic, and GalNet node ships create interesting tactical and narrative possibilities. Losing your logistics ship in a battle isn't just a supply problem — it's a communications blackout.