To provide email and satellite internet access direct to laptop sized portable terminals.

How does RBGAN work: 

The solution is to have high power transmission in the downlink and high sensitivity satellite uplink sensitivity. This is largely achieved simply by using a large 10m diameter antenna on the satellite. The earliest satellites (e.g. Telstar) used low power, say 1 watt, into its antennas with gain of 3 dBi or so plus 30m diameter dishes on the ground.  The RBGAN idea simply reverses this arrangement so there is nothing too improbable about it.  

The feed system will need to generate some 100 spot beams, each approx  1.8 deg beam-width, thus covering all the visible surface of the earth, which looks like a circle approx 18 degrees diameter as seen from the R-BGAN satellite.  With such a design it is possible to have an uplink G/T per beam of 17 dBK  (10m dia, 1.6 GHz, 300K)

On the downlink, beam gain will be about 42 dBi giving a beam edge eirp of some 55 dBW when the power allocated to a beam is 40W.  The power per beam will need to vary according to the traffic required.  If you do the RBGAN link budgets using http://www.satsig.net/linkbugt.htm you will find that uplink bit rates of 100 kbit/s and downlink bit rates of 144 kbit/s look quite feasible. 

* This is not 'broadband' as I understand  the term in respect of cable modems, ADSL phone lines and fixed larger 1.2 to 1.8m satellite dish users, rather medium speed.  Even the 144 kbit/s is shared amongst multiple terminal users.

Located at orbit longitude 65 degrees east the RBGAN service is now successfully operating on Inmarsat-4 satellite where it has has coverage of Africa north of the equator, Europe, and Asia to the west of Calcutta.  Coverage to the south of Africa and further to the east in Asia is expected but is not guaranteed and awaits confirmation.  In some places RBGAN is subject to licence restrictions.

There are three main manufacturers: NERA, Thrane & Thrane and HNS.

RBGAN - Regional Broadband* Global Area Network

Ideal Inmarsat RBGAN terminal test site - Everest camp.
http://www.everest.co.jp/sat/sat_main.htm for full details.