gcs undertakes Research & Technology Development activities directed towards integrating video, interactive data services, and novel types of interactive multimedia as well as improving the utilization of bandwidth.

Starting from DVB/MPEG-2 technology for digital video and for Internet technology, gcs develops hardware and software components for interactive multimedia applications. The goal of the developments is to deliver systems which are compatible with popular hardware and software platforms, comply with international standards and are fully integrated with Internet technology.

All developments are directed towards turn-key systems for interactive multimedia applications and services – "Internet Broadcast Solutions".

Multicast Web Caching

Based on an idea named SiMPLE, born nearly ten years ago, a new ESA funded project called YouCache aims to successfully integrate SiMPLE technology in already deployed two-way satellite systems.

SiMPLE addresses the observation that more than 90 per cent of the web traffic stems from less than 10 per cent of web servers with a satellite based multicast web caching system. Repetitious content is cached and served to the users without latency and each request served from the client cache consequently saves costly satellite bandwidth.

ASTRA2Connect is an already deployed commercial two-way satellite system operated by the project partner SES ASTRA, serving the end-user market at DSL-like costs Efficient use of the satellite capacity is of utmost commercial importance, because less capacity consumption per user means more users per transponder.

Consequently, the integration of SiMPLE into the ASTRA2Connect system, as the initial target, for exploiting the effectiveness and efficiency of web caching is considered a commercially attractive solution, that may well be adapted to other two-way satellite systems addressing the residential market.

IP over DVB

The success of digital television relying on Digital Video Broadcast (DVB) technology is its capability to carry Internet Protocol (IP) packets as well. Low-cost receiver equipment for home PCs is available as USB devices and PCI boards, hence, making high-speed IP-multicast services direct-to-home feasible and achievable.

gcs develops since years software for novel IP-multicast applications, that require in many cases no return-link at all. Services established on top of it will provide high-speed filtering of those information relevant and interesting to the end-user even depending on its current location.

DVB is standardized for wireless satellite and terrestrial, and cable delivery networks, with which ubiquitous access to information is only a matter of economy of scale.

Many customers have already realised the benefits of automatic high-speed on-demand push services and redefine the roles of networks, switching to IP over DVB technology for mission critical services.

Reliable Multicasting

Reliable IP-multicast software is responsible for delivering multimedia data to subscribed receive stations with high efficiency and reliability. This is achieved by adding a reliable multicast layer on top of the IP/DVB based transmission system.

Reliable IP-multicast shortens transaction times, reduces bandwidth requirements and, hence, leads to faster services if it is combined with an appropriate group management and error handling transport protocol.

gcs and University of Salzburg have developed a light-weight reliable multicast protocol, called Restricted Reliable Multicast Protocol (RRMP), which provides end-to-end reliable data delivery service to higher layer entities. It implements Forward Error Correction (FEC) as an appealing approach to avoid feedback implosion for reliable multicast transport. FEC techniques transmit additional redundant information to enable the receivers to correct a certain amount of lost data, without requiring retransmission.

To provide garantueed full reliable transmission RRMP requires a low bandwidth return link for requests to retransmit the FEC information of lost packets. A proactive mode allows to reduce the number of retransmissions in permanently sending FEC and only those FEC information for packets have to be retransmitted where lost packets could not be corrected.

gcs has integrated RRMP into its light-weight IP-multicast program DataCast sender/receiver to easy integration of IP-multicast file delivery into existing environments. The performance and reliability of DataCast and RRMP was the key issue that DataCast/RRMP was decided to become the IP-multicast software for the ENVISAT data dissemination system.

RRMP also is a key component of our SiMPLE technology.

DVB Interface Hardware

Integrating IP/DVB transmission into Internet environments is primarily a matter to implement a suitable and low-cost encapsulator board that plugs into a standard PCI or CompactPCI slot and provides a DVB compliant external interface, for example Synchronous Parallel Interface (SPI) or Asynchronous Serial Interface (ASI).

The first version of such a board has been developed by gcs already in 1997 and is the base component for our IP/DVB gateways. The board is capable to support speeds up to 45 megabit/sec and is typically delivered with Linux drivers.

The second version has been developed under ESA contract and is now available as high-speed successor. Again Linux drivers are available. This board has increased Rx and Tx performance (supporting full ASI net bitrate of 216 megabit/sec), remultiplexing capabilities and is the base component for IP/DVB multiplexers.

The basic design perfectly fits for off-the-shelf applications while its flexibility in software and hardware makes it also ideal for quick adaptation to special problems.