Satellite beams data at record 1.2Gbits/s
The great ATM switch in the sky.
By Martyn Williams, IDG News Service | Published: 14:06, 13 May 2008
Engineers testing a recently launched Japanese communications satellite have succeeded in establishing a two-way Internet link running at 1.2Gbits/s each way.
The speed represents a record for satellite communications, according to the Japan Aerospace Exploration Agency and the National Institute of Information and Communications Technology.
The tests were carried out on May 2 as part of verification of the Kizuna satellite. In the tests data was transmitted on two 622Mbits/s channels both up to the satellite and down to a receiving antenna. Together the combined data transmission speed was 1.2Gbits/s.
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Kizuna was launched on February 23 and is intended to provide high-speed Internet links to homes and offices in remote areas, to organisations as a back-up during natural disasters and to improve regional communications links in Asia.
One of the satellite's special features is an on-board Asynchronous Transfer Mode (ATM) switch. In other satellite Internet systems data sent to the satellite has to be sent to an earth station, demodulated, switched to its destination and then remodulated and sent again via the satellite to reach its destination. With a switch onboard the satellite is capable of doing all this in space thus making more efficient use of the available frequency spectrum, according to JAXA.
Tests carried out in March and April verified uplink communications at 1.5Mbits/s and downlink at 155Mbits/s using a compact 45 centimetre antenna and both up and downstream at 155Mbits/s using a larger 1.2 metre dish. At the time JAXA said the 155Mbits/s downlink was the fastest in the world achieved with such a small size antenna.
