(E-Mail Removed) hath wroth:
>Thanks for all your replies. Things I should mention, first my boss
>told me he would have satellite internet connection available to us but
>that he need it a way to distribute the signal so that we could all
>have internet at each truck, I dont know if it works while moving I
>guess I should clarify that to him, right now we have a couple of cell
>phone connections and they work while moving so I guess he assumes is
>the same for the satellite connection.
Well, this is a two part problem. Part one is how to maintain a
satellite internet connection (I'll assume Direcway) while moving.
Part two is how to maintain a wireless connection to the other trucks
while moving at the same time.
As far as I can tell, you're doing it all wrong. For the internet
connection while moving, you will probably do better with cellular
wireless using EV-DO or HSDPA. You can get about 600Kbits/sec average
download which should be sufficient. Upload is about 300Kbits/sec
which is FAR better than the 100Kbits/sec you'll get with a satellite
connection. (Direcway claims up to 1Mbit/sec but that's only in the
middle of the night with a perfect connection). My guess(tm) is that
you'll be uploading quite a bit of collected data to wherever and
therefore upload speed is critical. Satellite just doesn't do well
with upload.
There are other satellite data services that will also work. However,
the real question is how much data are you going to up/down load and
how often? Many of the marine satellite data service will easily
handle a moving vehicle, but are rather limited on traffic size.
Unless you need to move data between the various trucks, it would
probably make sense to just give each truck an EV-DO cell phone and
forget about the wireless interconnection.
Part two of the puzzle is tricky and expensive. You can put high gain
omnidirectional antennas on the roof of each truck, but any difference
in vertical elevation will cause a problem. Wi-Fi will work while
moving but is seriously affected by reflections, multipath,
interference, and other wi-fi systems. It may be made to work, but I
question on how reliable it will be.
Methinks the right answer is to use 900Mhz data. The speeds are
slower than 2.4GHz 802.11g, but are a fair match to what can be
commonly done with satellite or cell phone internet. I suggest you
look at the offerings of:
http://www.avalanwireless.com
http://www.waverider.com
http://www.freewave.com
Most of these transmit at about 1watt. The higher power, lower
frequency, and slower data rates, translate into longer range. The
antennas are less critical and there is very little interference.
>Also I should mention we are 90% of the time on the highway, I work for
>the Hurricane Research at UF and we chase hurricanes on the east coast
>so we are almost all the time on open exposure terrain.
How much data do you send back and forth? How often? That makes a
big difference in the selection of appropriate technology.
>We use the internet to get real time weather data mostly.
What's your interpretation of "real time"? Does it mean that you have
equipment that has to synchronize with some type of raw date
collector? That will be difficult with the typical 700msec satellite
latency.
>It would be
>great if we could use it moving, but if not possible then at least
>distribute the signal when we are setting up equipment.
Do you have time to point an antenna on each truck to the central
truck carrying the satellite dish? Can you guarantee line of sight at
all times between each truck and the central truck? If so,
directional antennas on each truck might be an option. However, I
suspect you're in a rush and don't have time to tinker with
directional antennas. That means onmis which which might have
radiation angle and gain problems.
--
Jeff Liebermann
(E-Mail Removed)
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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