As suggested by another member I'll repost this as a separate topic. I need to setup an Access Point on one of the trailers that is pulled by one of the trucks of our convoy. Our convoy is made up of 6 trucks. We have a Satellite Internet connection and we need to create an AP so that all the 6 trucks would have internet connection. Is there any way I could setup the AP with a router an amplifier and antenna? I'm assuming the range has to be maybe like half a mile. Another member suggested that the trucks would act as reflectors of the signal. Any suggestion as how to solve this issue is greatly appreciated.
A half mile in a moving vehicle could be a problem. Given this sounds like budget is not excessively an issue, one could experiment. A consumer grade AP will only cost about $70 or less, external antenna about that much again maybe a bit less. If you can get it to work with say a couple of trucks say one on front and back of the truck with the AP, then you could relay down the lenght of the trucks (a couple of bridges). How do you plan to make the satellite feed work while moving? That IMO would be the big problem, the uplink.
How fast do you need it to be? A few VHF modems would make it very easy to set it up, but only give you
2400bps or so (maybe more these days). How much bandwidth does a truck need? :-P A fast sat. connection that keeps going while your moving is serious kit if you're trying to get a high bitrate, so I'm guessing 2400bps isn't going to be the bottleneck.
Are these trucks moving when communications is required? Maintaining a satellite connection is difficult while moving. I've seen it done on a rocking boat with a gyro stabilized platform, but I don't know about vehicles that go under bridges or have the sky blocked by buildings, trees, etc.
What manner of bandwidth do you need? You can trade range for bandwidth to some extent. As others mentioned, there are low speed wireless modem devices that might be more suitable.
I don't like amplifiers unless both ends of a link are amplified. Putting an amplifier at one end gives you fabulous transmit range, but your receiver can't hear the reply. All it does is create a jammer with little improvement in communications range.
Half a mile will probably require directional antennas on the trucks. These cannot be easily aimed while moving. If your convoy is moving, and you're using directional antennas (typical gain about 5dBi), then you'll be limited to about 300ft radius range.
This may not be all that bad because you can possibly build some type of mobile mesh repeater system. Like amplifiers, I have a bad attitude about mesh systems and very little experience. However, this might be a good use for one. If you could keep the distance between trucks to about 300ft, you might be able to maintain end to end communications. I don't think it will be very fast as each hop cuts the maximum bandwidth in half. That will be fine for perhaps email and light surfing, but if you're planning on streaming video, forget it.
I didn't see that posting but I don't think that will work. Passive repeaters, passive reflectors, and periscope antennas are large and inefficient.
Nope. I gotta know what manner and quantity of data you're trying to move, whether the convoy is moving, whether there are any installation issues, approximate budget, and whether there are any environmental or topographical issues.
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.
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.
We use the internet to get real time weather data mostly. 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.
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:
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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.
How much data do you send back and forth? How often? That makes a big difference in the selection of appropriate technology.
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.
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.
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