Satmode

SATMODE: ALWAYS-ON SATELLITE RETURN PATH TECHNOLOGY FOR DIGITAL INTERACTIVE TV PLATFORMS.

The lack of an efficient and scalable return path has always limited true interactivity over satellite TV. Remote interactivity is the key element needed for the continuation of growth of digital television through the introduction of new services. This interactivity requires a scalable, secured, always on, permanent, instantaneous connectivity.

SATMODE answers this need, allowing the connection of TV consumers individually, both ways with their iTV content providers, with other consumers, with other infrastructures (GSM and internet) in real time, at any time, all the time. The main characteristics of SATMODE are: always on connectivity, packet transmission, ability to carry IP, bit rate adaptability (1 to 64 kbit/s), random access scheme, flexible air-interface.

Although compatible with existing satellites, SATMODE is designed to be ready for new generations of space segments.

Purpose of the SATMODE technology

SATMODE is a low cost interactive TV solution via satellite, targeting the mass-market through consumer products.

SATMODE supports several new services to the viewer, like the following ones:
* Betting
* Communication: Chat, SMS, e-mail
* Tele-Voting, Polls, Play-along, Quiz
* Games: standalone or multiplayer
* Interactive advertising
* Home Shopping
* Personal Data Consultation / banking
* Walled Garden Internet Services

SATMODE also supports new features allowing the technical management of the iTV platform:
* Enhanced conditional access
* Audience metering
* Statistics gathering
* Hard disk drive content management

SATMODE presents several specific technological advantages. Among them, the messages are sent through SATMODE without any establishment time with a total transmission time lower than a few seconds.

The system is scalable up to the complete DTH market and is designed to minimize the terminal cost.

Due to the nature of iTV traffic, SATMODE is also very competitive in terms of communication costs and thus in terms of total cost of ownership.

Modem Layer

The modem layer is specified by a proposed CENELEC standard (prEN50478).

The SATMODE design having led to this specification was optimized for the iTV case.

The choice of constant envelope modulations was made to minimize the terminal cost. Thanks to this property, very low cost ODUs operating at full saturation and in non-linear mode can be used.

The moderate bit rates of SATMODE allow to use very low power transmitters (typically 100 mW), keeping the cost compatible with the mass-market.

The selected access scheme -slotted ALOHA- is efficient on iTV traffic and very easy to scale up to a very high number of terminals only sending a few packets from time to time.

The SATMODE modem specification aims at fully specifying the behavior SATMODE modem function used in a terminal.

To increase the applicability and the probability of commercial success of SATMODE, it was decided to design SATMODE as a system usable with existing space segments and ready for future satellites improved for point-to-point applications.

Considering this objective, it was considered as mandatory to have built-in flexibility in terminals deployed today and ready for the future.

This flexibility allows SATMODE to be used in extreme scenarios by adjusting the modem parameters:
* Very power limited scenarios (it’s the case for most VSAT Ku-band satellites)
* Aggressive multi-beam space segment, targeting high spectral efficiency.

To reach that goal and nevertheless keep full interoperatibility of terminals, SATMODE uses a fully specified waveform toolbox.

Each building block has a well-defined space of operation and can be used without limitation in this space.

The building blocks of the SATMODE toolbox are:
* Symbol Rate: 2 kHz to 128 kHz
* Binary or quaternary CPM
* Programmable phase filter for CPM modulations (GMSK being a specific case)
* Flexible Turbo or Turbo-like
* Programmable interleavers (3)
* Programmable constituent codes with bypass possibilities (2)
* Programmable Unique Word structure
* Tables extraction from a DVB TS (DVB-S or DVB-S2 broadcast)

All the parameters are sent by the HUB through DVB tables, even allowing changes during operation:
* FCT: Sprectrum organisation in Carrier Groups
* FAT: Spectrum Allocation to services

Signalisation information sent to specific terminals is also embedded in DVB tables (SMT tables).

The terminal is fully defined: it must be able to play the complete waveform space.The HUB usually only implements one scheme and sends the tables to the terminals to instruct them to play that scheme.

SATMODE Project

The SATMODE development project was funded at 50% by [http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=11843 ESA] .

References

* ESA [http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=11843] Retrieved Aug. 28, 2005
* SES-ASTRA [http://www.ses-astra.com/products/broadcast/itv/] Retrieved Aug. 28, 2005
* Newtec [http://www.newtec.be/index.php?id=256]