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By Prima Setiyanto Widodo
The use of the Ku-band for satellite communications in tropical regions like Indonesia seems to become more frequent. We observe that several satellites “parked” above Indonesia have Ku-band transponders, and even Ka-band transponders. Just look at the satellite owned by NewSkies (NSS 6), launched in December 2002 and positioned at 95° East, containing only Ku-band transponders and with a footprint directed to Indonesia (Sumatra, Java, Borneo, Celebes, Bali, Nusa Tenggara, Moluccas). This is also the case for the
iPSTAR satellite, to be launched this year, 2004. The Malaysia owned Measat 3, to be launched in 2005 and co-located with the Measat 1 satellite will have 24 Ku-band transponders. The Ku-band footprint directed towards Indonesia has been named by Measat the “Ku-band for Indonesia”. Measat 4 is planned to cover the whole of Indonesia from West to East. This satellite will be launched by Malaysia in the year 2007.
Why have those satellite planners the courage to use the Ku-band frequency? Of course they have calculated the technical feasibility, besides applying a regenerative system, also called Automatic Link Control, which is to exercise control over the power of the satellite to compensate for rain attenuation up to 10 db. Furthermore, for the ground segment there now exists a new development, that is the use of AUPC (automatic uplink power control) and Turbo Coding. Actually, AUPC has long been available, but it is only recently being massproduced.
With AUPC we can automatically control the transmit power in line with the rain attenuation, in general up to 9 db. With turbo coding, we can also save the power used, so that with the same transmit power we will obtain a bigger fade margin compared to a satellite modem that does not use turbo coding. At this moment, Adaptive Coding is being developed whereby the system will adapt itself to the weather conditions. The system will change the modulation in case of a weather change (rain), while retaining the bandwidth; only the throughput will decrease. By using adaptive coding, link-availability will increase.
There is an additional problem in satellite communications. TCP/IP applications have difficulties in passing through because of the long delay caused by the time it takes for the signal to travel from earth to space to earth. TCP/IP was designed for short delay times, passing through terrestrial connections. Are there solutions for this? There are, among others, by re-engineering the TCP algorithm, TCP spoofing and IP over DVB. Besides that, there is a TCP that has been designed for satellites (see This problem is not a serious hindrance any more. VPN services over satellites are no
longer just a dream; it has been proven that they can be applied successfully.
It can be imagined what could happen if these various new technologies are combined. It is time that Indonesia abandons its wariness to use Ku-band frequencies. An inexpensive system of broadband satellite services will assist greatly in the process of empowering its citizens, because for such a wide area as Indonesia, the appropriate information technology infrastructure is satellites.
One can imagine ATMs that respond quickly, and also Internet kiosks that can be moved from one site to another. The penetration of banking services can be executed faster, as well as the penetration of Internet. Distance learning and e-learning can be established relatively speedily and at lower cost. There is even the possibility to have General Elections on-line with VSATs connected to every community. This agility can only be carried out if the equipment used robust, fast and compact. We can do this with Ku-band systems.

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