Satellites With Sub-Frame Delay

As broadcasters launch NEXTGEN TV and telecoms launch 5G, a couple of high-profile, rich-guys with rocket companies are racing to build new wireless data communications infrastructures to benefit everyone, everywhere.

There’s a Low Earth Orbit (LEO) satellite infrastructure moving into place overhead promising to provide affordable gigabit internet service anywhere worldwide.  Typically, a large fleet of deployed LEO satellites is called a constellation. The low altitude of LEO satellites reduces their individual footprint compared to many geostationary satellites.

Flat panel design allows a dense launch stack of satellites to be individually launched from the nosecone frame. Courtesy Starlink.

Flat panel design allows a dense launch stack of satellites to be individually launched from the nosecone frame. Courtesy Starlink.

Moving Towers

Think of a single LEO satellite as a moving cell phone tower. As one tower moves away (as you drive your car), your phone connection is handed off to the tower with the strongest signal. LEO satellites use a similar technology to hand-off users to other satellites as they circle the globe.

The strategy is to blanket the skies with 1000s of small satellites that can be easily received by antennas that only need to be pointed up. Elon Musk's newest LEO satellites are painted black to disappear at night.

LEOs aren’t relatively permanent like TV communications geostationary satellites orbiting at 22,300 mile altitudes are, nor do they have the typical 260 millisecond (ms) end-to-end delay, not including compression, modulation, demodulation and decoding. LEO satellites are two-way systems for IP data, like cell phone networks.

A typical LEO satellite’s altitude is about 300-400 miles but can be up to 1200 miles high to qualify as LEO. Orbital periods can be from 84 to 127 minutes. Low-orbiting LEO satellites are about 95% closer to Earth’s surface than geostationary telecommunications satellites, reducing end-to-end latency to approximately 30 ms. The delay is expected to diminish to about 20 ms as satellites spiral closer to Earth over their lifespan. For reference, one frame of common 29.95 fps NTSC video is about 33.4 ms.

Time is Money

Near or more than one second of source latency complicates live TV production. Near-zero latency (0.02 – 0.03 mS) is enough to excite TV news people, bonded cellular users, remote event broadcasters and eSports pioneers. Bigger non-TV markets where the lowest possible latency is mission-critical include stock trading, financial markets, medical, government, automotive, maritime, enterprise, aviation and on-line gamers and gambling.

Four companies are or were active in the LEO market until recently. At this moment, we're down to a couple of rich guys with rocket companies.

LeoSat was a Luxembourg-based company that planned to launch 79 to 108 LEO satellites, using Ka band for downlink, at an estimated cost of US $3.6 billion. LeoSat ran out of money in November 2019 before launching any satellites.

OneWeb filed for Chapter 11 on 3/27/20, because of the financial impact and market turbulence related to COVID-19. OneWeb's vision was “to enable Internet access for everyone, everywhere.” Before bankruptcy, OneWeb secured global spectrum, successfully launched 74 satellites and developed user terminals. With half its planned 44 ground stations completed or in development, OneWeb performed successful demonstrations of its system with broadband speeds in excess of 400 Mbps and latency of 32 mS. 

Intellian recently announced a contract with OneWeb to manufacture User Terminals for use on the OneWeb Network, and the first User Terminals were planned to go into production immediately. The future of OneWeb is unknown at this time.

In April 2019, Jeff Bezos’ Amazon announced plans to offer broadband access from orbit with 3,236-satellite ‘Project Kuiper’ constellation. FCC filings describe Amazon’s plan to put 3,236 satellites in low Earth orbit, including 784 satellites at an altitude of 367 miles (590 km), 1,296 satellites at 379 miles (610 km) and 1,156 satellites in 391-mile (630 km) orbits. An Amazon spokesperson said "This is a long-term project that envisions serving tens of millions of people who lack basic access to broadband internet. We look forward to partnering on this initiative with companies that share this common vision."

Bezos' space travel and rocket company, Blue Origin will launch the satellites. However, a spokesperson said Project Kuiper is an Amazon effort, not Blue Origin's.

Starlink satellites have 4 antennas, allowing an enormous amount of throughput to be placed and redirected in a short time. Courtesy Starlink.

Starlink satellites have 4 antennas, allowing an enormous amount of throughput to be placed and redirected in a short time. Courtesy Starlink.

Starlink

Then there’s Elon Musk. His SpaceX company is using its reusable Falcon 9 rocket to launch payloads of 60 Starlink satellites per launch into an approximate 340 mile-altitude orbit. The first launch was on 23 May 2019. The fourth launch was on 18 March 2020. The approximate bandwidth of each individual Starlink satellite is about 16.6 Gbps. Starlink says every 60-satellite launch adds a terabyte of bandwidth to its constellation.

Musk’s project mission is to ultimately redefine internet service with high-speed service across the globe from a constellation of about 4000 LEO satellites by 2025. When completed as planned in 2027, the Starlink Constellation will consist of nearly 12,000 satellites, with possible later extension to 42,000 for total Earth coverage. To put that number in perspective, a grand total of only 8900 satellites have ever been launched and only 2218 of them remain in orbit today.

Currently, the FCC has authorized and approved SpaceX’s deployment of 4,425 satellites to provide fixed-satellite service (FSS) around the globe. Gwynne Shotwell, the president and chief operating officer of SpaceX said completing the project may cost $10 billion or more. Musk said during a recent call with reporters that Starlink could net the company perhaps US $30 to $50 billion per year.

A pizza-sized box is expected to be available for about US $200 to get on Starlink’s broadband network. Monthly subscription is anticipated to be about US $80 for 1 gigabit service. According to the Starlink website, first service is targeted to begin this year in the northern US and Canada, and rapidly expand to cover the populated world by 2021. If Musk’s project seems altruistic, in fact it is because it is also a source of funds for Musk’s vision of Mars exploration and human settlement.

Before being ejected from the stack and unfolding the solar panel, each satellite is about the size of a desk. Courtesy Starlink.

Before being ejected from the stack and unfolding the solar panel, each satellite is about the size of a desk. Courtesy Starlink.

Starlink satellites navigate using stars and sensors for position and altitude, track other related satellites in real time. They can also be moved by ground control and can move themselves automatically when necessary with an autonomous collision avoidance system using on-board ion thrusters. The Starlink website says the ion thruster-powered satellites are the first Krypton-propelled spacecraft ever flown.

Also, according to the Starlink website, at the end of life satellites will utilize their on-board propulsion system to deorbit over the course of a few months.

In the unlikely event the propulsion system becomes inoperable, the satellites will burn up in Earth’s atmosphere within 1-5 years. Satellites begin catastrophic deterioration at altitudes below 200 miles. 

Frezeframe from a Starlink video shows a satellite being ejected from the Falcon 9 rocket. Courtesy Starlink.

Frezeframe from a Starlink video shows a satellite being ejected from the Falcon 9 rocket. Courtesy Starlink.

Need For Speed

How LEO satellites will affect the success of 5G remains to be seen. While it seems that cellular providers can’t roll out 5G fast enough, 4G average speeds of about 100 Mbps easily handle the needs of most TV content distribution models. Cellular visionaries are predicting 6G with hologram content in approximately 10 years.

In the meantime, the 26 Mbps bandwidth of an ATSC 3.0/NEXTGEN TV stream promises to change TV more than anything else on the foreseeable technology horizon, and it’s virtually Starlink-ready.

Cellular users don’t complain about bandwidth, they complain about coverage. 5G bandwidth is reported to top out at about 10 Gbps, which is one benefit of new spectrum many users will never use. 5G coverage with full bandwidth needs a strong signal that requires major investments in an exponential number of additional cell towers and antennas.

In the 5G world, testing is underway for broadcasting one-to-many TV streams on unique 5G frequencies and tests are reported success so far. A LEO connection has plenty of bandwidth for HD and UHD video. Today’s Netflix requires 25 Mbps for UHD 4K. At the end of the day, consumers will make their content delivery preference decisions based on price.

MEOs

Medium Earth Orbit (MEO) satellites orbit at altitudes from 12 miles (2,000 km) to 22,000 miles (35,700 km). MEO satellites have a longer design life than LEO satellites and don’t require the highly engineered designs required for geostationary orbiting. Instead, precision atomic clock timing sources are required for MEO. The higher altitude MEO satellites have a larger horizon-to-horizon footprint than LEO satellites, allowing reliable service in the most remote areas on Earth, such as the South Pole.

MEO constellations can allow for low latency, high speed links with fewer satellites, and can even be simpler to track than LEO satellites. Some of today's leading satellite companies such as SES are planning future launches of their next generation satellites in MEO.

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