European Space Agency

STELIOS (Ku-band Microterminal for multicasting)


The project will develop a Ku-band micro-terminal for reception of satellite multicast services. It uses a combination of spread-spectrum modulation, coding and use of near-end-of-life satellites allows for the cost-effective transmission of medium data rates to micro-terminals (antenna apertures of less than 20cm diameter). Such terminals could be used in a wide range of mobile and portable environments. The system will support IP multicasting for educational and entertainment purposes.

This system has several significant and desirable features. A user can enter data in a convenient form, such as from a notebook computer. The transmission can take place from a major earth station and can use a low-cost satellite such as Astra 1A. The 'downlink' is a highly integrated micro-terminal, which can be physically integrated with advertising units (billboards, displays etc). This unit achieves a high level of performance in a very small volume.
A new company, KuCast Ltd has been formed to exploit this technology.

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There are several key technical issues, these are:
Development of low-cost demodulator that operates optimally in the presence of thermal noise, phase noise and co-satellite interference.
The development of low-cost terminal that can be manufactured at a cost commensurate with the business plan is a key issue.
Power consumption compatible with an outdoor receiver powered by solar panel is a key issue. An addressing scheme that is efficient, flexible and scaleable is a key issue.
Keeping the channel overhead low is a key issue.
Confirmation that direct sequence spread spectrum meets the satellite access requirements and ITU regulations.

Key commercial issues are:

  • Equipment Supply or Service Provider,
  • Exploitation by technology transfer and licensing,
  • Exploitation by product sales,
  • Exploitation by selling a multicast service,
  • Exploitation by franchising,
  • Strategic Partnerships Key Customers,
  • Competition.


There is a market opportunity for Ku band multicasting based on cost. We have analysed the approximate cost of delivering a kbyte of data by GSM SMS, GPRS, 3G and the proposed satellite method for a unicast service.

For a multicast service, SMS is poor as it depends on a point-to-point circuit switched transport layer and requires n circuits for n recipients.

GPRS and 3G fare better for multicast in the sense that the packet link layer control (LLC) supports multi-point addressing. Multicasting within a given coverage is possible without re-use of resources but for a multi cell multicast (the general case) there is a cost penalty for a multicast service.

Clearly the satellite solution offers a consistent low cost solution on a pan continental basis. The small physical size of our receiver/demodulator is also a great benefit. This will allow it to be integrated into a range of indoor and outdoor display types.


The system has the following elements:

  • User browser,
  • Booking server,
  • Local terminal,
  • Scheduler,
  • Uplink Ethernet interface,
  • Uplink processor,
  • Uplink synch/asynch converter,
  • Upconverter,
  • Transmitter,
  • Flat plate antenna,
  • LNB,
  • Downconverter/demodulator,
  • Synch/asynch converter,
  • Downlink Ethernet interface,
  • Display Ethernet interface,
  • Display processor.

The user will be able to access the system by pointing to a web page on the Booking Server. The Booking Server will allow the user to: identify himself, load material into the system, specify when and for how long the clip will be transmitted, specify the recipient display terminals (individually, by group, by combination of group and time-slot. It will also be possible, through a local terminal, to load clips into the system and specify when and for how long clips will be transmitted. This may be required for large files, which it is not sensible to load over the Internet. The scheduler will be co-located with the uplink to avoid the delays and uncertainties of the Internet.

It will have software to load a multi-wheel data carousel to transmit files and images in a predetermined prioritised schedule. This software will also address separate groups of micro-terminals by private IPv4 unicast address or IPv4 multicast address or proprietary addressing schemes. The Ethernet interface will be physically part of the processor module and will provide a general purpose, high data rate, and standard interface to the uplink. We will use an 8-bit micro-controller running software written in C and compiled to run under a real-time OS.

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The project started by defining the System Elements to be developed. This took into account the target commercial applications and intended services.

The bulk of the work involves developing a Multicast Transmitter and a Multicast Receiver. Our aim is to have very low cost equipment and to achieve this we are using low cost microprocessors, serial interface chips and demodulator chips. The result is a highly integrated low cost receiver/demodulator, with sufficient intelligence to interface directly to standard display devices.

We are building several 'close to market' prototypes of the system units.

Current status

The multi-layerd printed cicuit boards for the modulator and demodulator are currently being built. The software for the on-board micro-controller is well advanced and is being tested. Some critical sections require further attention and are being worked on presently. The modulator communicates with the carousel using TCP/IP and the micro-terminal streams data to its displays using multicast UDP. The satellite link carries data encapsulated in SDLC frames.

Discussions are taking part with strategic partners to exploit the micro terminal and the overall system that it can support. There is a strong interest in the concept and in the way the system can use ageing satellites which are in an inclined orbit.

Status date

Thursday, May 28, 2009 - 10:41