Once the terminal is correctly pointed at the satellite, it automatically logs on to the system and, in a matter of a few minutes, is ready to be used. Initially, it gives a low-bit-rate connection to the Internet, allowing access to a booking portal for reserving higher bit rates.
The traditional downside of Ka-band has always been its susceptibility to rain fade. This is because, as a general rule, the higher the frequency of an RF signal, the more it is absorbed by rain. The latest systems compensate for this by running with significant spare capacity in clear sky conditions. In severe rain, the system will automatically drop to a more robust modulation scheme. It means the user will notice a drop in available bit rate, but should still remain on-air.
Let’s look, then, at a typical system designed for HD newsgathering. The minimum requirement should be for data rates of around 9Mb/s upload and 20Mb/s download, which gives comfortable headroom even when live to air.
The antenna will be in the 0.6m to 1.0m range. A 0.75m dish will give the required performance in most conditions. Most of the major manufacturers have Ka-band flyaway and vehicle mount antennas of this size in their product ranges. This links to the transceiver, which will probably be 3W to 4W. It will mount directly on the antenna and connect to the data modem by L-band RF cables, although some systems now use a single standard coax cable.
The IP-over-satellite modem will depend on the choice of satellite system. In addition to converting IP data to satellite RF, it will also supply power to the transceiver. The video data, in turn, comes from an IP video encoder, again widely established and proven technology.
The complete system is likely to weigh less than 44lb and pack into a single case, meaning it would not be a serious problem to take it as baggage on a commercial flight. Power consumption will be in the range of 60W to 70W, so the journalist could carry the system to a news location, rig it in a rental car and run it from the vehicle battery.
Most important, all this technology is available today and proven in use. Major broadcasters are taking advantage of the agility, flexibility and cost savings that IP over satellite delivers.
One broadcaster covered the Greek general elections using a single 70cm Ka-band antenna clamped to a railing on the roof of the journalists’ hotel. Using the bi-directional IP platform, they were able to provide simultaneous live reports for domestic and international television bulletins; off-air feeds of competitor broadcasters and local Greek TV; FTP transfers of edited packages; live radio reports; FTP transfers of edited radio packages; full access to the newsroom IT system; and Web browsing and e-mail.
All this was accomplished using a transceiver and modem combination, which cost $500. It makes an attractive alternative to SNG!
—Stuart Brown is Broadcast Systems Director of Cobham.