Hi,
I have been using 3G (HSPA) connection at my remote station for 1,5 years. It is connected to a 900 Mhz UMTS base station and the critical parameters have been the following on average:
Ping 60...80 ms
Downlink 1...3 Mbps
Uplink 300kbps...1Mbps
Those sound like sufficient values but the RXTX is very sensitive to even small variations in the speed/packet loss. I do experience a lot of RX audio bursts/idle periods (with audio quality set to zero) during internet busy hours (5PM-10PM) as there are a lot of other users connected to the same base station . Also the CW TX suffers from this. There is quite a lot of errors in keying during that time.
I have a 15 dBi 3G yagi antenna even thought the base station is very near (< 4 km). The 3G router is a BandRich R300
http://www.bandrich.com/R300-Spec.html. The rig is TS-480 and I have been running only on 160 and 80 meters.
Hoping to get a LTE connection some day...
73 de Kari, OH2XX