Our company developed stations that collect data in an agricultural field. These field could be in the middle of nowhere, so stations use GSM/GPRS with SIM card that automatically switches to strongest provider.
Every 5 minutes, an internet connection is setup to send data to a server. The data has a structure with packet length, command, sensor data and crc check. But these data structures are sent with a http post to an url.
For 480 bytes of data, about 2550 bytes of data traffic is used. There is a lot of overhead in the HTTP protocol. Because we only need to send 480 bytes of data, we have 80% overhead with the post over http. Now we have a few hundreds of stations and that number is growing. So costs for data traffic are increasing rapidly.
We want to do a redesign of the transmission of data. The data is send by microchip microprocessor in the stations.
Our goal is to decrease the overhead as much as possible, with guaranteed data delivery. So I looked into TCP and UDP.
TCP has failure detection and recovery, but has a higher overhead. UDP has lower overhead, but there it is not guaranteed that data is delivered without failure.
My first idea is to build a server that listens to a TCP port. And stations sent the data over TCP. Mainly because of guarantied data delivery.
With UDP we have to develop check and resend of data ourself, but the data structure of our records is already prepared to do checks.
So I am really in doubt what to do. And I am trying to get an answer on these questions:
How many bytes overhead would it take by TCP and UDP to sent (and deliver) 480 bytes of data?
Are TCP and UDP the best ways to consider for sending 480 bytes of data, or is there a smarter solution with even lower overhead?
