Source #1 relates to ranges for WiFi direct: (
https://stackoverflow.com/a/24705722)
Source #2 relates to time taken for WiFi direct connection to be established: (
https://stackoverflow.com/a/19297780)
@20Kph, you're looking at about 5.6 meters per second. Going with an optimistic 50 meter range for your WiFi (I'm assuming no external antenna, having to go through the truck walls, glass, etc), you have about 9 seconds worth of time. With a 4-6 second setup time for the WiFi connect, you may have 3-5 seconds worth of time. The issue is that even though a connection is established, it may still take even more time to discover that the connection has been established. Also, any other interference (truck walls, weather situation, other signals in the truck, etc.) would cut the distance and time allotted for the connection and data transfer to happen. Then you also need to take into account the WiFi ability of the device used. Would you be able to install external antennas on the trucks for WiFi and tie your devices to the antenna(s)? That may give you the additional distance needed to give you time enough to pull this off. Doubling the range would give you an additional 9 seconds to play with.
On my desk, connection is instant - because they are 1 foot away from each other... Each unit cresting a hill (on opposite ends) may be a different matter due to no line-of-sight.
Again, I have all the data needed to determine this but the process is long and involved, demanding high server CPU and a scheduled time. I am looking to shorten the process by real time capture using device hardware / functionality - Stretched to the limits.
Sorry, no additional antenna can be installed. The Samsung Active 8 tablet does not support this - no port (now obsolete - as many good products have become). That would have been nice since an external antenna would have increased the range.
I don't need much and not for long. The critical moment is when they pass each other (when strength is 99 percent). So, maybe have loaded trucks (going south) be the server and do the grunt work (collect data). Empty trucks would just need to be in a mode to see server and connect / transmit who they are, where they are and road speed.
The tablets are mounted so they are looking through the windshield. I connect to the AP, at shift end, and transmit daily data at distances of up to 200 meters away easily.
I could, I suppose, constantly buffer data to send as a large burst (10 k) - just as vehicles pass each other.
Or, lessen the transfer payload by having both vehicles store their own data and figure it out on the back end - by using a unique id that each shared during a passing event to sync the data. Like I stated in past posts - "Cat Skinning - there is more than one way..."
Granted, this may or may not work - but one will never know unless you experiment. I can do this in my own environment without having to be on-site to see if it is feasible.
Yes, it sucks not having real time over cell. All of this could have been avoided.
If I can get this to remotely work, it produces another benefit. I can advise drivers (pop up warning screen) of an approaching vehicle - even if they did not get the mandatory two-way radio message when they are suppose to call out.
Note: There has been many incidents when vehicles left the road, wrecked truck and trailers, caused expensive clean-ups (lead anyone?) and personal injuries because drivers did not slow down (or stop as sometimes required) when approaching an on-coming vehicle.
Thanks