Assuming the data request goes from the sat terminal to the sat, then
from the sat to the earth link station, out and back from the internet,
then from the earth link station to the sat, and finally from the sat
back to the terminal, it will have traveled about 143,000Km. With the
speed of light being 300,000Km/sec there is about 450ms of latency
caused by the simple physical layout of any sat based system.
This doesn't explain the sat latency I have seen around here.... 1400ms
to google via Directway, 1300ms to google via Wild Blue. Nor does it
account for the 30kbit/sec upload speeds...
Wild Blue's local partner just suspended installs in my area. They
claim that they can't install any more because of upload speed and
latency problems caused by too many users with too much traffic. I am
now picking up users who the local partner got all excited about Wild
Blue. And once Wild Blue users see a wireless connection with
300-500kbit upload speeds, they start breaking their contracts...
Just my $.02.....
--
Tony Weasler wrote:
I wonder what the latency is going to be. The second article mentions
a usage cost of between $4-7/MB. They state that the smallest
terminals are 1kg and "about half the size of a laptop." This won't
be a competitor to existing broadband infrastructure, but if the
latency is low enough it could provide great short-term connectivity
for remote areas.
- Tony
07-12-2005 [12/7/05] - Inmarsat has announced the successful launch of
its Broadband Global Area Network (BGAN). The company unveiled the new
service to the world in a joint press briefing with representatives of
its Distribution Partners and manufacturers at its London HQ on
December 7.
Six years in development, BGAN is the world's first mobile
communications service to provide both voice and broadband data
simultaneously through a truly portable device on a global basis. It
is also the first to offer guaranteed IP data rates on demand.
Delivered via the Inmarsat-4 satellites - the world's most advanced
commercial communications spacecraft - the service is initially
available across Europe, Africa, the Middle East and Asia.
Following the successful launch of Inmarsat's second I-4 satellite on
November 8, network coverage will be extended to North and South
America from Q2, 2006.
The two I-4 satellites will deliver seamless broadband coverage across
85 per cent of the world's landmass and be available to 98 per cent of
the world's population.
"BGAN delivers broadband where other networks can't," said Michael
Butler, Inmarsat's chief operating officer. "It enables anyone to set
up a broadband mobile office in minutes and remain fully productive -
wherever they are on the planet."
BGAN offers IP data speeds of up to 492kbps, with the option of
guaranteed data rates up to 256kbps. The service is designed for
mobile users who want dependable, secure broadband access when working
in locations with an unreliable or non-existent telecoms infrastructure.
[...]
http://about.inmarsat.com/news/00018831.aspx
----------------------------------------
Lift-off for Inmarsat's global broadband
By John Walko - EE Times - (12/08/2005 5:42 AM EST)
[...]
The cost of transferring one megabyte of data from anywhere in the
world is put at between $4 to $7, while a voice call is expected to
cost under $1 a minute.
[...]
http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=174906190
----------------------------------------
AP story:
http://abcnews.go.com/Technology/wireStory?id=1382023
--
Blair Davis
AOL IM Screen Name -- Theory240
West Michigan Wireless ISP
269-686-8648
A division of:
Camp Communication Services, INC
--
WISPA Wireless List: wireless@wispa.org
Subscribe/Unsubscribe:
http://lists.wispa.org/mailman/listinfo/wireless
Archives: http://lists.wispa.org/pipermail/wireless/
