Have you noticed that Low Earth Orbit (LEO) is getting more and more crowded? Several companies are developing worldwide satellite networks to provide Internet access to every square inch of the Earth’s surface. SpaceX and Elon Musk’s Starlink are perhaps the most visible companies, but other participants in this derby include Amazon’s Project Kuiper, SpaceLink, Viasat and Telesat. On the one hand, it will be very convenient to have multiple companies competing to spread Internet-based communications everywhere. On the other hand, there is a compatibility issue which rears its ugly head. All of these companies are developing their own communications satellite constellation networks, and it’s very obvious that the satellites in each constellation will communicate with each other to minimize latency through the network. It is also quite obvious that the links between these satellites will be based on optical communications. In other words, space lasers.
One of the concerns currently being raised is the lack of a standard protocol for inter-satellite optical communications. Of course, the satellites in one provider’s constellation will probably be able to communicate with the other satellites, at least until the next optical communications stack upgrade, but there’s no standard protocol in sight that would allow satellites from different providers to communicate with each other. But wouldn’t that be a good idea?
One organization that thinks compatibility would be a good idea is the latest incarnation of the US government agency that started this whole internet thing. That would be DARPA, the Defense Advanced Research Projects Agency. DARPA’s predecessor, ARPA (that’s DARPA minus the “D” for “defense” because at the time the “D” was silent) funded the development of the ARPANET – the predecessor of the Internet – in 1966. ARPANET is where we got packet switching, distributed network control and the TCP/IP protocol which are the fundamental technologies of today’s Internet.
DARPA is trying to avoid the networking situation we had in the 1970s and 1980s, where many computer companies had developed mutually incompatible networking protocols. Digital Equipment Corporation (DEC) had DECnet. IBM had SNA (Systems Networking Architecture) and used a token ring protocol. Telephone companies like AT&T used ISDN. Depending on your perspective, ISDN would have meant “Integrated Services Digital Network”, “I see dollars now”, or “I still don’t know”. Datapoint pushed its ARCNET (Attached Resource Computer Network). General Motors has been playing around with a Token Bus network protocol for some time. And then, of course, Xerox PARC developed Ethernet, which was so successful that Xerox dropped out of the IT business altogether.
DARPA would rather history not repeat itself in space, where no one can hear you scream, so the agency has a new program designed to bring some organization to the situation. The name of the project is the Space-Based Adaptive Communications Node program, abbreviated as Space-BACN, and, of course, pronounced “space bacon”, which should not be confused with the regular BACN, the Battlefield Airborne Communications Node of the United States Air Force. You see, we’re well on our way to minimizing confusion here.
According to DARPA’s website, the Space-BACN initiative “aims to create a low-cost, reconfigurable optical communications terminal that adapts to most inter-satellite optical link standards, translating between various satellite constellations.”
It appears, at this time, that DARPA is not trying to develop an inter-satellite networking standard. This is probably a very good idea since these are the early days and the experimentation is still ongoing. Instead, DARPA appears to want to develop a universal optical modem for satellites that can be easily adapted to a range of protocols.
Space-BACN Phase 0, already completed, has developed an architectural design. Phase 1, which includes three “technical areas”, is now underway. Technical Area 1 (TA1) aims to develop a flexible, low SWaPC (size, weight, power, cost) optical aperture or optical head, which is responsible for pointing acquisition, target tracking and tracking functions. optical transmission and reception. Here are lasers. The three companies selected by DAPRA for TA1 are CACI, MBRYONICS and Mynaric.
TA2’s goal is to develop a reconfigurable optical modem that supports data rates up to 100 Gbps over a single wavelength of light. The TA2 electronics connect to the TA1 space lasers via an optical fiber. TA2 participants selected by DARPA include II-VI Aerospace and Defense, Arizona State University, and Intel Federal, LLC.
TA3 will “identify the critical command and control elements needed to support inter-satellite optical link communications between constellations and develop the schematic needed to interface between Space-BACN and commercial partner constellations.” The companies participating in TA3 are the providers of the satellite constellation: Space Exploration Technologies (SpaceX), Telesat, SpaceLink, Viasat and Kuiper Government Solutions, an Amazon subsidiary.
The TA2 effort needs to develop several capabilities, and I discussed those needs with Jose Alvarez, a senior manager in the Intel Office of the CTO, representing the Intel Programmable Solutions group. This is the group within Intel responsible for FPGAs. Alvarez explains that Intel is working on the electronic part of the optical modem, which will require significant DSP capabilities to implement the modem’s FEC (forward error correction) algorithm and to compensate for Doppler effects on light. After all, orbiting satellites move fast enough that relativistic effects become apparent. These DSP capabilities will likely be based on FPGA implementations for the foreseeable future, at least until there is enough experience to codify the algorithms into standards.
In addition, Intel hires technologists from its Assembly Test Technology Development (ATTD) division and researchers from Intel Labs. For its role in the TA2 effort, Intel plans to develop three new chips that will be integrated into a multi-chip package (MCP) device using EMIB (embedded multi-die interconnect bridge) and AIB (advanced interface bus) packaging technologies. ) from Intel. EMIB and AIB technologies are commercially proven Intel packaging technologies that the company has used for years to manufacture its most advanced processors and FPGAs. The most extensive use of these packaging technologies is in the company’s Ponte Vecchio device, which combines 47 active chips into a single package to create its GPGPU for high-performance computing (or supercomputers).
The three planned chiplets include:
- A DSP/FEC chiplet implemented with Intel Process 3, which is currently Intel’s most advanced digital process node.
- A data converter, optical transimpedance amplifier (TIA), and driver chiplet implemented with the Intel Process Node 16, which includes RF FinFETs that can be used for analog RF signal processing, high data converters speed, TIAs and pilots.
- A photonic IC (PIC) chip based on Tower Semiconductor’s photonic process technologies that can implement low-loss waveguides and etched V-groove mechanical interfaces for optical fiber.
Intel has begun its Phase 1 of the TA2 program, starting with the design of the three chiplets, and they are working with the other players to fully define the interfaces between system components in each of the other technical areas. Phase 1 will last 14 months and will end with a preliminary design review. Upon completion of Phase 1, DARPA will select Phase 1 participants from the first two technical areas to participate in an 18-month Phase 2 project to develop engineering design units based on the Phase 1 work. hopes that all this work will produce interoperable satellite constellations in the years to come.