This page can be seen as a first approach to a working configuration to the Huawei 1550, which is an USB modem. In the tests we try to connect to the 3G network.
The device in which is used the modem is a TP-Link TL-MR3040 and the hardware device version is v1.0, and we're using the OpenWrt firmware recommendation from the device page for the v1.0 hardware version: TP-Link TL-MR3040#Installation (only for v1.0).
By default, the installed OpenWrt firmware in the TL-MR3040 device doesn't recognize the modem.
Looking for a working solution we found the page http://eko.one.pl/forum/viewtopic.php?id=652 with a complete working solution. Copy-paste the configuration, you don't need to have the PIN code activated.
With that configuration, the device now connects to the Internet using the 3G modem connection.
The problem is that there are some disconnects from the 3G network and you have to unplug and plug again the device to reconnect. The connection has been alive for 2-3 hours without disconnects.
The page configuration is for another OpenWrt version, then you have to change some bits to adapt to the installed firmware version, as for example the quoting for option parameters when configuring the /etc/config/network file.
To avoid disconnects, the page says that you have to change in the /etc/ppp/options/ the next parameters and set them as:
lcp-echo-failure 3 lcp-echo-interval 3
But writing directly to the config file doesn't works, and have to be done using Luci for example, due to a reported bug http://luci.subsignal.org/trac/ticket/532. This configuration is done in Interface → 3G (your 3G interface) → Advanced Options.