Inmarsat is set to launch the first of its fourth-generation satellites Thursday: It will launch two satellites this year offering speeds of up to 432 Kbps symmetrically. Tenzing said last year that although it was limited to relatively slow speeds with current technology that the I-4 Inmarsat satellites would allow them to bond one, two, or four channels providing planes with 432 Kbps, 864 Kbps, or nearly 1.7 Mbps of symmetrical bandwidth.
Connexion by Boeing uses existing satellites to offer 5 Mbps downstream and 1 Mbps upstream with an option to go to 20 Mbps downstream. However, Boeing's more conventional system requires transponders in each area of coverage in which planes fly that effectively restrict the bandwidth in those zones. Inmarsat uses a beam focusing method that will allow them to deliver spot access to congested areas keeping throughput higher. Each satellite will support 200 spot beams covering 250 square miles each.
Inmarsat equipment is already in thousands of long-haul planes, or about 50 percent of all such planes. Tenzing told me in 2004 that on many planes, the upgrade process will require an hour or two of a technician's time to swap out modules.