Advanced Cellular ASIC to Enable Satellite to Mobile Network

Article By : Nitin Dahad

Cellular ASIC from Ensilica to enable any unmodified handset to connect to AST SpaceMobile's space-based cellular broadband network.

Ensilica is developing the cellular ASIC that will enable AST SpaceMobile’s planned space-based cellular broadband network. AST SpaceMobile intends to build what it claims will be the first global cellular broadband network in space to operate directly with standard, unmodified mobile devices. Its aim is to create a network that lacks the coverage gaps inherent in most land-based networks. That should improve the connectivity for the five billion people who now subscribe to mobile services, and then also bring cellular broadband to those who remain unconnected, nearly half of the world’s population.

The company engaged with Ensilica over a year ago, with a brief to deliver a next-generation ASIC with state-of-the-art performance and power efficiency to maximize the capabilities of the company’s network. The ASIC will be a key communications component of the spacecraft electronics payload for AST SpaceMobile.

ensilica-space photoEnsilica’s business development director, Paul Morris, explained the challenge to EE Times in an interview. He said, “AST is putting a mobile base station in space so that you can talk directly to the mobile, and maybe people don’t quite fully understand the implications of that. The key advantage is it works with any existing mobile, and you just need to buy a subscription to connect to their network. And people like Vodafone and others are partnering with them.”

The capability to talk directly to mobile handsets is important for AST SpaceMobile because it will be the most significant differentiator from Starlink, the space-based broadband services supplier founded by Elon Musk. Starlink will connect with towers, which would then distribute subscriber communications. AST SpaceMobile, meanwhile, intends to communicate directly with individual subscribers’ handsets, cutting out the intermediary link through cell towers and land-based network infrastructure.

Starlink has a head start; it has roughly 1,600 satellites already in orbit, with plans to loft as many as 42,000 in some indeterminate future span. Part of Ensilica’s job is to help AST SpaceMobile catch up.

Morris said, “The big challenge of making this work is the limited power supply from the solar cells. If you imagine a satellite, as it goes around the earth, with a low earth orbit satellite you’re in the sun for a certain proportion of the orbit, and then you’re in total darkness. So, in the small time you’re in the sun, you can charge and then the rest of the time you’re running on batteries. That limits the power budget. The challenge they brought to us was to build a modem design that met all their communications specifications, that met the power budget.

“And the only way of doing that was to come up with a novel architecture and to use a very advanced semiconductor process node,” Morris continued. “We can’t say which one it is, but we can say it’s an advanced node and these weren’t available even a small number of years ago. It wasn’t possible to do this before. You could never have got the signal processing down low enough to actually run it off the solar cells. And that’s really the breakthrough, I think.”

He added that the chip is a complete custom design involving a mix of integrated RF design and signal processing, on a FinFET based process.

Inherent to the challenge is meeting the performance requirements within the power budget. This means managing the tradeoffs between bandwidth, transmit power, receive sensitivity, and power consumption, all of which are at odds with each other.

The Midland, Texas, headquartered AST SpaceMobile is developing a satellite, BlueWalker 3, which is a 693-square-foot phased array for planned direct-to-cell phone connectivity at 4G/5G speeds. This is going through final integration and testing, with an expected launch in Summer 2022.

The company’s chief technology officer, Huiwen Yao, said, “AST SpaceMobile’s decision to select EnSilica was based on their advanced digital signal processing and RFIC work, enabling them to deliver the innovative architecture to meet our requirements for our next generation semi-conductor. We look forward to working with EnSilica to help AST SpaceMobile bring cellular broadband connectivity to the world.”

Last year Ensilica announced it was developing a single-chip Ka band transceiver IC for the European Space Agency.  The mmWave IC will form a key component of next-generation, low-cost hybrid automotive communication terminals, enabling vehicles to always be connected. The IC is being developed as part of ESA’s Advanced Research in Telecommunications Systems (ARTES) project and the CASSIS project (Connected Automotive Satellite Service Integrated System), which is led by the UK Satellite Applications Catapult (UKSAC). Operating at up to 31.5 GHz, the custom Ka band CMOS ASIC will form part of an affordable, consumer-scale communications module supporting a flat panel electronically steerable phased array antenna. The hybrid module will communicate with geostationary and low earth orbit (LEO) satellites, 4G/5G infrastructure and Wi-Fi communications to deliver high capacity connectivity to cars, small vessels and aircraft.

This article was originally published on EE Times.

Nitin Dahad is a correspondent for EE Times, EE Times Europe and also Editor-in-Chief of embedded.com. With 35 years in the electronics industry, he’s had many different roles: from engineer to journalist, and from entrepreneur to startup mentor and government advisor. He was part of the startup team that launched 32-bit microprocessor company ARC International in the US in the late 1990s and took it public, and co-founder of The Chilli, which influenced much of the tech startup scene in the early 2000s. He’s also worked with many of the big names—including National Semiconductor, GEC Plessey Semiconductors, Dialog Semiconductor and Marconi Instruments.

 

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