Latency on Server request


I got problems using a TCP Connection to a Server via GPRS with the SL6087 firmware R7.52.0.201306260837.
When i send messages from the Server to the SL6087 it takes between 2 and 90 seconds till i see something on the UART channel. So sometimes it works just fine and sometimes the message has a 90 second latency. Shortly after sending the messages from the server I can see the power consumption of the SL6087 going up, but i don’t get any AT command that there is data to collect. The server then resends the unacknowledged message and everytime again, I can see the power consumption going up but no activity on the UART. Eventually all the messages get send on the UART in one go.
Why does the SL6087 not send them on the first attempt? The messages are all stored, as no data is lost.

I create the connection as follows:


(I am sure, that the server sends the messages, because another client gets the messages in time)
Whenever the SL6087 contacts the server I receive an acknowledgment within 0.5-1 second.

Has anyone experienced a similar problem and knows how to solve it?
Looking forward to your answers.


ok, so it means the error is with SL6087 only?
With other FW version it is correct?
I didn’t understand… “why SL doesn’t send it in first attempt”…
seems like the serial port is getting blocked… have you tried on USB?



the SL6087 with that FW is the only one i use.
I’ll check if it works better via USB as soon as possible.



I managed to make some tests on the Sierra Wireless Development Kit and made the tests via USB instead of UART. They had the same outcome -> delays ranging from 2-90 seconds.

After that i used another SIM Card from another provider and it worked much better. The delays were ranging between 0.5 and 3 seconds. So i guess the delays are related to a poor network coverage from that particular provider at my workspace.

Still i want to adress the delays related to poor network coverage. Is there any possibility to establish a connection to a base station faster or even stay connected at all times?

Thanks in advance

Not necessarily; there are many steps & gateways between the mobile and the remote host - it’s certainly not just a matter of local coverage :exclamation:

How about using something like tracert to see where the delays are happening… :question: