Japan Launches "Super-Speed" Internet Satellite 159
A number of readers wrote in about the launch this morning of a Japanese H-2A rocket carrying a Kizuna ("Winds") satellite into orbit. Kizuna is intended to provide "super high-speed data transmission" for Japan and Southeast Asia. The news stories on the launch, such as the AP's linked here, are short on technical detail. For example they say the satellite successfully achieved orbit 175 miles above the earth — hardly suitable for Internet communications to a specific area on the surface (remember Teledesic?). Reader nebulus4 provided a link to the Japan Aerospace Exploration Agency site with an illustration and a little more detail. Such as the fact that Kizuna is destined for geosync orbit, and that a 45-cm antenna will equip eventual users for 155 Mbps down / 6 Mbps up, whereas a 5-m antenna will allow enterprises and ISPs to tap into 1.2 Gbps down. Given the latency to geosync orbit, you probably wouldn't want to use Kizuna to play an online shooter.
Re:Geosynchronous Latency (Score:3, Interesting)
In any case, a Molniya orbit would only require three satellites for coverage, looks ideal for Japan as a nation, and the perigee can be as low as ~400km. The round-trip latency for 400 km would be (400*4/300,000), or 5ms (if my mental mathematics is not off by a decimal point or so).
Yes, you'd need three satellites, admittedly.
Re:Remember Pearl Harbor!! (Score:3, Interesting)
The fact that you posted this racist crap in the first place or the fact that you posted anon so you could mod down anyone that responded to you.
Re:Now featuring... (Score:5, Interesting)
From the JAXA site about Kizuna:
"Scheduled orbit: Geostationary orbit at 143 degrees East longitude and at an altitude of about 36,000 km"
It is, even though the summarizer slipped up a bit (technically the term is correct, but somewhat misleading), destined for geostationary orbit.
Re:Geosynchronous Latency (Score:3, Interesting)
The connection sucks for anything interactive
Except, possibly chess.
I know you were joking, but as an administrator on a chess server, I can tell you that people get pretty pissed off when lagging half a second. It's acceptable for playing long games, but most over-the-net chess games are 1 to 5 minutes per player per game. Yes, it's a whole different game that just shares moving rules with "chess".
Re:latency = what? (Score:3, Interesting)
First, the speed of light is slowed down by fibre optic cable, just as light is slowed travelling through any medium. Roughly light in optical fibre travels 2/3 the speed of light in a vacuum.
So, to compute minimum latency, take the length of fibre, divide by the speed of light, divide by 2/3, and then double it, as the data must go there and back.
Thus, if we had a 1300 km cable: 1300km / 299,792.458 km/s / (2/3) * 2 = 0.013009 s = 13 ms round-trip-time.
So, for our 1300 km fibre optic cable, the RTT (ping time) propagation delay would be 13 ms. In reality, you'd have to add delays from routers at either end, but in modern high-end equipment operating at 1Gbps or more, the router delays are very small, something like 0.03 ms on a 1500-byte packet.
To go back to the game server and the gamer latency, in real life, it could be as low as 0.1 ms if you were in the same room as the server, or around 5 ms if you were in the same city as the server. Certainly less than the 70ms minimum cited in the article.
P.S. I just realized that if 1300km = 13ms latency, 6892 km = 68.92 ms latency, or very close. I never noticed this before, and i'm a bit shocked. I can now easily roughly guess the length of fibre runs using traceroute. Fascinating.