MB with UDP streaming and HSUPA

[Deckard]

I'm using VLC to stream out from a capture card, linked to network with an ethernet cable. Next, I've tried WiFi connection and everything still works fine.

Now I'm using a HSUPA USB modem key and the output stream is a little bit jerky, with macroblocks, etc ... I guess the problem deals with buffering but I've never changed anything. Now I guess I need to.
So what do I need to change ? sout-udp-caching, sout-udp-ttl, sout-udp-group, sout-udp-raw ?

I'm using the CLI : "... :sout=#transcode{vcodec=h264,venc=x264,vb=448,scale=1.0,acodec=mp4a,ab=64,channels=1}:duplicate{dst=std{access=file,mux=tx,dst=},dst=rtp{dst=IP_ADDRESS}}"
Where do I add the sout-udp parameters ?

Thank you.