From Earth to Space: how optical technologies will play a significant role in future Internet
Exponential increases in Internet speed have facilitated an entirely new set of applications and industry verticals underpinned by evolving fixed optical networks, and projects such as Metro-Haul. As we pioneered optical communication and control for next generation 5G Internet and services, we must now look for emerging challenges ahead. We may look up both figuratively and physically, for our next opportunity. In the future space communication will play a significant role in providing Internet communications and optical technology will be the enabler.
Legacy satellites, probes and space-based objects like the International Space Station (ISS), rely mostly on radio technology for communication. Using radio, it would take approximately 2.5 seconds to send data to the Moon and back to Earth, several minutes from Mars. In 2014 the ISS tested OPALS (Optical PAyload for Lasercomm Science) system developed by NASA, this achieved a data rate of 50 megabits per second. By 2015 gigabit laser-based communication was performed by the European Space Agency (ESA) and called the European Data Relay System (EDRS). The ESA system is still operational and extensively used.
This year we are now seeing a slew of next generation meshed satellite constellations – OneWeb, SpaceX, TeleSat – with Alphabet, Amazon and Facebook also developing space-based communication projects. These new networks will be capable of providing global gigabyte Internet via space-based laser communication. These new satellite constellations are positioned in a Low Earth Orbit (LEO) Earth orbit which is approximately ≤ 2,000 km altitude, they number from thousands to tens of thousands, in a grid-like pattern, and will provide continuous internet coverage. The constellation will orbit the Earth on the order of 100 minutes, travelling at roughly 27,000 kmph.
These new satellite constellations can expand coverage to remote areas, as well as provide lower latency (<50 milliseconds) compared to rural legacy terrestrial networks. The potential for lower latency for long-distance connectivity stems from being able to build nearly shortest paths (after incurring the overhead for the up-links and down-links) instead of circuitous terrestrial fiber routes, and they also transmit at the speed of light in instead of that in fiber. Total throughput using these space satellite networks will range from 3 Tbps to more than 50 Tbps per constellation. These new networks will provide connections of 100s Mbps to residential users and multiple Gbps to enterprise users.
As we identified in our last blog (“OPTICS RESEARCH FOR FUTURE SMART NETWORKS AND SERVICES”) free-space optics technology will be a critical enabler for space-based Internet communication. Also, several problems exist for the control and orchestration of space-based optical networks, these include both data plane and control plane challenges:
Data Plane Challenges
- Small footprint and weight, low power consumption, high resiliency with zero maintenance;
- Operation at broad temperature ranges with minimal performance degradation;
- Exceedingly long (>10 years) Mean Time Between Failures (MTBF);
- Inter satellite or inter orbital links have to cover larger distances; therefore the transmission scheme has to be power efficient with excellent sensitivity at the receiver;
- Need to consider power versus transmission costs, and path viability;
- Programming of dynamic optical technology such as Steered Laser Transceiver (SALT) devices, will be required.
Control Plane Challenges
- Acquisition and tracking of satellites as they move, and calculating relative velocity;
- Selecting paths for direct Free Space Optical (FSO) uplinks and downlinks, consideration of cloud cover, air turbulence and external object occlusion;
- Next generation space networks are not static, the overhead satellite changes frequently, the laser links between space-based satellites change often, and link latencies for links that are up will change regularly;
- Consideration of the time-varying topology of the space network will necessitate frequent routing updates;
- A need to avoid routing oscillation between space and ground networks.
The need for an evolution of IP transport architecture and mechanisms, may also be required. Several emerging techniques and technologies are currently in discussion within the ITU-T FG NET-2030 effort, such as “New IP”. This group of researchers, vendors, network operators and application developers and service providers, are investigating use cases, architecture and technologies for Network 2030, and beyond.
We now find ourselves at a significant stage of optical evolution and Space-based networks represent an an exciting development of optical technology . As we look beyond Metro-Haul we may start to consider where, and what, research opportunities we should pursue next.