Communications concepts:
1. Meteor burst radio/data - using ionisation tracks caused by meteors as they burn up in the upper atmosphere.
Several thousand kilometre range as previously discussed here:
http://forum.juhlin.com/showthread.php?t=2688
2. EME (Earth-Moon-Earth) communication
Using the Moon as a reflector - eliminates need for satellites, global range when the Moon is in the sky at each location.
wiki entry is a good start:
http://en.wikipedia.org/wiki/Earth-M..._communication
pdf from Princeton is excellent but potentially too detailed:
http://physics.princeton.edu/pulsar/...E_2010_Hbk.pdf
Summary is that 1-2m diameter satellite dishes are usable, or ~12-15 foot yagi antennas.
Data rates wouldn't be too bad with modern digital comms (think dial-up, not broadband or LTE type speeds).
You could use inflatable satellite dishes, as manufactured by GATR:
www.GATR.com
30kg kit runs on compressed air to make a 1.2m diameter satellite 'dish'.
I don't like ELF because of the geological, power and size restrictions on transmitter siting. The receiver antennae would need to be pretty large for the boltholes to get messages.