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Introduction
With the rapid growth of data usage around the world, there is an increasing demand for high-capacity, low-latency communications infrastructure. Two vital technologies that form the backbone of global communications are submarine cables and broadband satellites. This article provides an in-depth comparison between submarine cables and satellite networks in terms of their costs, reliability, capacity, and latency. It analyzes the relative strengths and limitations of each technology and how they complement each other.
The article also examines recent technological advancements like low-Earth orbit satellites, and laser inter-satellite and satellite-ground links that are poised to transform the capabilities of satellite networks. This article offers insights into the technological battleground of global data transmission, helping readers understand the infrastructure that underpins our hyper-connected information society. While both technologies are advancing rapidly, each has unique capabilities that will ensure satellites and submarine cables continue to coexist as critical components of the global communications ecosystem.
Coexistence
Broadband service delivered by satellites in Low Earth Orbit (LEO) can potentially supplement, but not completely eliminate, the need for submarine cables, due to a variety of reasons. Here are a few reasons why we can't solely depend on satellite-based communications:
- Costs: The costs associated with launching, maintaining, and upgrading satellites are much higher than maintaining and laying new submarine cables. While the costs of satellite launches are decreasing due to the advent of reusable rockets, it is still more expensive compared to the cost of laying new submarine cables.
- Reliability: Submarine cables tend to be more reliable than satellite connections. Satellites can be affected by space weather, cosmic radiation, or even orbital debris. In contrast, once laid, submarine cables are relatively unaffected by weather and other environmental conditions.
- Capacity and latency: While laser connections between satellites (or satellite constellations, such as SpaceX's Starlink) can theoretically provide global coverage, the total bandwidth capacity and latency of these systems is currently inferior to that of submarine cables. Submarine cables have a vast capacity to handle large data volumes with relatively low latency. It's not that satellite systems can't handle large volumes of data, but the data transmission rate is simply lower compared to fiber-optic cables.
- Regulatory Challenges: Satellite-based communication systems must deal with more complex international regulations and treaties related to space usage, whereas submarine cables, though they do face international agreements for their deployment, generally encounter a more straightforward regulatory landscape.
- Data Sovereignty and Security: Data transmitted through satellites can be subject to different security and data sovereignty issues compared to data transmitted through submarine cables. Submarine cables allow for a more direct, point-to-point connection, which can be more secure.
Additional comparative details for each item are provided below.
Costs
Satellite communications require substantial upfront investment and ongoing costs, making them more expensive than terrestrial cable networks like submarine cables. Here are some of the key cost elements involved:
- Satellite Manufacture and Launch: Creating a satellite is a high-tech, high-cost venture involving extensive R&D, testing, and production. Once the satellite is built, it must be launched into space, which involves costs for the launch vehicle, fuel, and insurance. It's worth noting that while the cost of launching satellites has been decreasing due to reusable rockets (like SpaceX's Falcon 9), it still represents a substantial investment.
- Satellite Maintenance and Replacement: Satellites have a limited lifespan (typically 10-15 years). After this, they must be replaced, which involves the cost of building and launching a new satellite. Additionally, there can be costs related to maintaining the satellite's function from ground control stations, including tracking, telemetry, command, and control.
- Ground Stations: Satellite communication also requires a network of ground stations around the globe. These stations have to be built, maintained, and staffed, adding to the operational costs.
- Spectrum Rights: Satellite operators have to pay for spectrum rights to transmit signals to and from Earth, adding to the overall cost of satellite communications.
On the other hand, submarine cables, while also having significant costs, are generally less expensive:
- Cable Production and Installation: While laying submarine cables is an expensive venture, it's typically cheaper than the cost of manufacturing and launching satellites. The costs include the manufacture of the cable, the cost of the ship to lay the cable, and labor.
- Maintenance: Once laid, submarine cables require less maintenance than satellites. There's a cost for repairing cables when they are damaged, but this is relatively rare and less costly than satellite replacements.
- Longer Lifespan: Submarine cables have a longer operational lifespan than satellites, often up to 25 years, reducing the frequency of replacement costs.
- No Spectrum Costs: Submarine cables do not require the purchase of spectrum rights, reducing their operating costs compared to satellites.
That being said, the costs of both technologies are decreasing, and both are vital for global communication infrastructure.
Reliability
The reliability of communication systems like satellites and cables is determined by various factors such as environmental conditions, operational lifespan, and failure risks. Here's a comparison of the reliability of submarine cables versus satellite connections:
Submarine Cables:
- Environmentally Stable: Once laid, submarine cables are generally unaffected by most environmental conditions. They are on the seafloor, insulated from atmospheric weather and conditions that could interfere with signal transmission.
- Physical Damages: Submarine cables are vulnerable to physical damages caused by ship anchors, fishing activities, and even natural disasters like earthquakes. However, these instances are relatively rare and well-documented, allowing for fast repair operations.
- Redundancy: The world's internet is carried by many submarine cables. So even if one cable gets damaged, the data can be rerouted through other cables, ensuring uninterrupted service.
- Constant Connection: Submarine cables provide a constant connection. The latency and speed of the connection are generally consistent and don't change depending on time of day or other factors.
Satellite Connections:
- Environmental Sensitivity: Satellites can be affected by space weather (solar flares), cosmic radiation, and even orbital debris, which can interfere with signal transmission.
- Line-of-Sight Issues: Satellite signals can also be blocked or degraded by terrestrial weather conditions, buildings, or trees, affecting the reliability of the connection.
- Limited Lifespan: Satellites have a limited operational lifespan (typically 10-15 years). When a satellite reaches its end of life or if it malfunctions, it could lead to a loss of service until a replacement satellite is launched.
- Signal Latency: Satellite communications have higher latency (the time it takes for a data packet to travel from source to destination) than submarine cables because the data has to travel to space and back. This latency can impact the performance of certain applications, like video conferencing or online gaming.
- Limited Bandwidth: Satellites also have limited bandwidth compared to submarine cables. This means they can handle less data at once, which can slow down speeds during peak usage times.
While both systems have their respective advantages and challenges, in terms of overall reliability—considering factors like environmental resilience, consistency of service, and lifespan—submarine cables are generally considered more reliable than satellite connections.
Capacity
Capacity: This refers to the amount of data that can be sent through the network at a given time, typically measured in gigabits per second (Gbps) or terabits per second (Tbps).
- Submarine Cables: Modern submarine cables are fiber-optic, capable of carrying multiple terabits of data per second. For example, the MAREA cable, a joint project by Microsoft, Facebook, and Telxius, spans the Atlantic Ocean and has a capacity of up to 200 terabits per second. These cables carry the bulk of the world's internet traffic.
- Satellites: Satellites, particularly those in geostationary orbit (GEO), have much lower capacity compared to submarine cables, often measured in gigabits per second. Even the new mega-constellations of satellites in low-Earth orbit (LEO), such as SpaceX's Starlink, while having a combined capacity that is much higher than traditional satellite systems, still cannot match the capacity of submarine cables.
Latency
Latency: Latency refers to the delay in the transmission of data and is usually measured in milliseconds (ms). It's especially critical for real-time applications like video calls, online gaming, and certain types of financial transactions.
- Submarine Cables: Since data in fiber-optic cables travels at approximately two-thirds the speed of light, latency can be quite low. The exact latency depends on the length of the cable, but for transoceanic cables, it's typically less than 100 milliseconds.
- Satellites: For satellites in geostationary orbit, latency is much higher, typically around 600-800 milliseconds, due to the large distance to the satellite (about 36,000 km above Earth). LEO satellites like Starlink operate at much lower altitudes (around 1,200 km), reducing the distance data needs to travel. This results in lower latency, comparable to ground-based systems, but still higher than most direct, terrestrial cable connections.
Latency in a network is often measured in milliseconds (ms) and represents the time it takes for data to travel from one point to another. Here are some specific examples related to the latency of different types of networks:
| Type of Connection | Approximate Latency (in milliseconds) |
|---|---|
| Local Area Network (LAN) | Less than 1 ms |
| Wi-Fi Network | 1-3 ms (local network) |
| 5G Mobile Network | 1-10 ms |
| 4G Mobile Network | 50-100 ms |
| Online Gaming (Optimal) | Less than 50 ms |
| Hibernia Express (Submarine Cable) | 58.95 ms |
| Typical Submarine Cable | Less than 100 ms |
| Starlink (LEO Satellite) | 20-40 ms (actual measurements are much higher, as described below) |
| Geostationary Orbit (GEO) Satellite | 600-800 ms |
Note that these are general values and actual latency can vary depending on a variety of factors including the specific technology used, the distance data has to travel, network congestion, and more.
In terms of capacity, submarine cables have an advantage. In terms of latency, LEO satellites may, eventually, have the advantage. However, deployed system measurements show much higher latencies than SpaceX has advertised.
SpaceX Starlink Latency as of Q1 2023
Based on the Q1 2023 data from Ookla on Starlink's performance, here are some updated latency numbers specifically for Starlink's space-to-ground latency:
SpaceX Advertised Target: 20-40 ms
Measured Performance:
- United States: 62 ms
- Canada: 70 ms
- Mexico: 97 ms
- Chile: 54 ms
- Peru: 48 ms
- Colombia: 55 ms
- Brazil: 75 ms
- Jamaica: 57 ms
The Ookla data shows that Starlink's latency in most countries tested falls in the range of 48-75 ms. This is somewhat higher than the previous rough estimate of 20-40 ms, but still very low compared to traditional geostationary satellite internet services. The lower latency is enabled by Starlink's low-Earth orbit.
The one exception is Mexico, where Starlink's latency is measured at 97 ms by Ookla. Overall, these updated numbers from real-world testing provide a more accurate picture of Starlink's excellent low-latency performance, which matches or beats cable/DSL in many areas. As Starlink continues to improve its network, we may see further reductions in latency over time.
Examples of Broadband Satellite and Submarine Cable Systems
SpaceX Starlink
Starlink is a satellite internet constellation being developed and deployed by SpaceX to provide high-speed, low-latency broadband internet across the globe.
Key Details:
- Orbital Shells: The Starlink constellation consists of multiple orbital shells, with operational satellites across low Earth orbit (LEO) at altitudes of 540-570 km.
- Deployment Status: As of August 2022, SpaceX had launched over 2,900 Starlink satellites, with aims to eventually deploy up to 42,000 satellites. Starlink already has hundreds of thousands of users in over 30 countries.
- Design: Each Starlink satellite weighs about 260 kg and is equipped with high-throughput antennas, steerable laser links, and Hall thrusters using krypton propellant. The satellites are designed for rapid production and low-cost launches aboard SpaceX's Falcon 9 rockets.
- Capacity: In 2022, SpaceX shared that the total network capacity of Starlink is over 200 Gbps. As more satellites are deployed, total capacity is projected to reach up to 10 Tbps in the future.
- Latency: By virtue of its low-Earth orbit, Starlink is eventually expected to provide a space-to-ground latency of 20-40 ms, which is far lower than traditional geostationary satellite internet services. This matches or exceeds ground-based internet latency.
- Coverage: Starlink's phased array antennas allow seamless switching between satellites to maintain constant coverage for users on the ground. The expanding constellation aims to provide constant high-speed internet access anywhere on Earth.
Starlink represents a transformative leap in satellite communication capabilities and has the potential to disrupt the industry with its unique low-latency, high-capacity broadband service. As deployment continues, it may significantly alter the satellite vs submarine cable capacity and latency dynamics.
Hibernia Express
The Hibernia Express cable, also known as Project Express, is a transatlantic submarine communications cable system that was laid by Hibernia Networks. It was specifically designed to provide the fastest data connection between major financial and media hubs in North America and Europe.
Key Details:
- Routes: The Hibernia Express cable system has a unique, low-latency path connecting New York to London, as well as connectivity to other major cities including Halifax, Montreal, Dublin, and Brean (UK).
- Completion: The cable was completed in 2015 after about two years of construction.
- Design: Hibernia Express was the first new transatlantic cable to be laid in over 12 years, and it was designed with the latest technology at the time of its construction. It's a 6-fiber-pair cable with an initial capacity of 53 Tbps (terabits per second). The cable was designed to support future upgrades for increased capacity.
- Latency: The primary design goal of the Hibernia Express was to achieve the lowest possible latency between New York and London, specifically targeting financial trading operations that can benefit from even the smallest improvements in latency. Upon completion, the cable achieved a latency of around 58.95 milliseconds, which was the fastest latency of any transatlantic cable at that time.
- Distance: The Hibernia Express cable follows a more direct route across the Atlantic than previous cables, with a total distance of about 4,600 kilometers.
| Aspect | Detail |
|---|---|
| Routes | The Hibernia Express cable system has a unique, low-latency path connecting New York to London, as well as connectivity to other major cities including Halifax, Montreal, Dublin, and Brean (UK). |
| Completion | The cable was completed in 2015 after about two years of construction. |
| Design | Hibernia Express was the first new transatlantic cable to be laid in over 12 years, and it was designed with the latest technology at the time of its construction. It's a 6-fiber-pair cable with an initial capacity of 53 Tbps (terabits per second). The cable was designed to support future upgrades for increased capacity. |
| Latency | The primary design goal of the Hibernia Express was to achieve the lowest possible latency between New York and London, specifically targeting financial trading operations that can benefit from even the smallest improvements in latency. Upon completion, the cable achieved a latency of around 58.95 milliseconds, which was the fastest latency of any transatlantic cable at that time. |
| Distance | The Hibernia Express cable follows a more direct route across the Atlantic than previous cables, with a total distance of about 4,600 kilometers. |
The Hibernia Express cable represents the evolution of submarine cable systems towards low-latency, high-capacity designs that can meet the increasing demand for data transmission speed and volume, particularly from industries like finance and media where fractions of a second can have significant implications.
How Will the Introduction of Laser Communications Change Landscape?
The introduction of laser communications in satellites is a significant technological advancement that could have a profound impact on the performance of satellite networks. It could potentially change several aspects of the comparison between satellite and submarine cable communications.
- Capacity: Laser communication technology can transmit data at a significantly higher rate than traditional radio frequency (RF) methods. This could increase the data capacity of satellite networks, potentially bridging the gap between satellite and submarine cable capacities. However, it's important to note that this would largely depend on the number and configuration of satellites, and even with this increase, satellite networks would still likely fall short of the capacity offered by modern fiber-optic submarine cables.
- Latency: Laser communication could reduce the time it takes for signals to travel from one satellite to another, which could slightly decrease overall latency. However, latency in satellite communication is primarily due to the distance the signal must travel to and from the satellite, which is determined by the satellite's altitude. Therefore, even with laser communication, the latency of satellites in low Earth orbit (LEO) would still be higher than that of submarine cables, and the latency of geostationary satellites would remain significantly higher.
- Reliability: Laser communications could also improve the reliability of satellite connections. Laser beams can carry more information and are less likely to be interfered with by other signals, which could reduce the likelihood of data loss or corruption. However, they can still be affected by atmospheric conditions such as cloud cover, and unlike submarine cables, they would remain susceptible to space weather and orbital debris.
- Cost: The introduction of laser communication technology could increase the cost of satellite networks, at least initially. This is because it requires new, specialized equipment both for the satellites and the ground stations. However, over time, the cost may decrease as the technology matures and economies of scale come into play.
The introduction of laser communications in satellites represents a significant technological advancement and could improve the performance of satellite networks. However, it's unlikely that this alone would allow satellites to outperform submarine cables in terms of capacity, latency, and cost-effectiveness.
The Bottom Line
While satellite technology is advancing rapidly and holds great promise, it's more likely that satellites and submarine cables will coexist and supplement each other rather than one technology completely replacing the other. Different applications and situations will require different solutions, and both satellites and submarine cables have roles to play in the global communications infrastructure.