Real-world use of Linux multipath TCP

LTE's theoretical peak is about 30 bits/Hz (using 8x8 MIMO); currently deployed LTE modems in cellphones do 2x2 MIMO for 7.5 bits/Hz, and can aggregate 2 or 3 spectrum bands to get high peak bitrates. LTE can be deployed in 1.4, 3, 5, 10, 15 and 20 MHz wide spectrum chunks, getting a theoretical speed peak of 600 Mbit/s for a single 20 MHz carrier; a current mobile LTE modem (like the one in the Samsung Galaxy S6) can combine 3 carriers at once, each band getting 150 Mbit/s to give you a peak of 450 Mbit/s raw data rate. You can expect to lose around 50 Mbit/s of the peak rate to overheads (network management, idle users checking in, cell handoff etc), for an LTE rate of 400 Mbit/s. Note that this throughput figure depends crucially on your serving cell sites having no other clients to serve; LTE reallocates airtime (and thus carrier aggregation bands) once a millisecond to keep latency under control, but your data rate is thus constantly varying with cell load.

Your 50 to 100 figure sounds right for a modem capable of 2x2 MIMO on a single band, talking to a base station that's only capable of 2x2 MIMO itself in a 20 MHz wide carrier; you've got a cell capable of 150 Mbit/s if it dedicates itself to you, but where other users (including network overhead) bring the speed down to a more realistic 50 Mbit/s. A base station with more MIMO capability (e.g. 8x4 MIMO) can get you to 100 Mbit/s on your 2x2 MIMO device despite the other users; to go much faster, you need carrier aggregation to let you use more than 20 MHz of spectrum, or more complex MIMO systems to let you get more bits on the same spectrum.