Community Research and Development Information Service - CORDIS


MEMO draws together both broadcasting and telecommunications technologies, to provide opportunities for a distinctive range of services. It makes use of developments in DAB, which provides the opportunity to broadcast not only sound, but text, graphics or even real-time video. The distinctive additional feature that MEMO provides is a 'return channel' using GSM technology to enable the user to 'interact' with the broadcast services.

In bringing these technologies together, MEMO provides the foundation for services that can be classified into three general categories:

-Data downloading - the DAB downlink is used to broadcast large amounts of information to all receivers. The user is then able to locally interact with that data.

-Interactive broadcasting/push services - Information is 'pushed out' to a selected number of addressed receivers. The user can then reply to the received information via the GSM return channel, for example to send back a simple report. It is also possible to add this information to the information being broadcast to other users.

-Personal services - DAB is used as an extension to GSM data communication for downloading large data files to an individual user via a broadband link. In such a way, it could provide, for example, a wireless (mobile) Internet service.

These different kinds of service are all possible within the same session. What is distinctive about MEMO is that it uses asymmetrical data rates, by coupling the broadband downlink (using DAB) with a low bit-rate interactive link (using GSM). Bringing together these two technologies allows for interactive services with downloading rates of up to 1.7 Mbit/s. Furthermore, the data can be broadcast over large geographical areas, facilitating high mobility.

Most interactive multimedia applications use asymmetric communications. A typical example is browsing the Internet: a very short request from a user terminal stimulates the download of huge data streams from the server to the user’s terminal.

Digital audio broadcast (DAB) was developed within EUREKA 147 and is standardised within ITU, ETSI and EBU. DAB, originally developed for sound broadcasting to mobile and portable receivers, is well suited to carry also any kind of digital data. The key features of the DAB system are its high data rate of up to 1.7 Mbps, the reliable transmission (convolution coding and interleaving in both time and frequency domain) and the flexibility of its general-purpose multiplex (including packet mode data transfer) that reconfigured at any time.

Associating GSM with DAB, such a system can provide interactive multimedia services to fully mobile users. The relatively low bandwidth of GSM does not limit these asymmetric services. The use of existing components based on well established standards for the technical chain (GSM and DAB) can lead to an early implementation of such services.

The MEMO system can handle broadcast and personal services as well as combinations of these, they can be categorised into 3 main types:

-Broadcast Type Services and Virtual Interactive Services. The DAB downlink is used to mainly broadcast information of general interest (push mode). On the receiver side the information is filtered and stored in a local database, consequently the interactivity is only virtual.

-Interactive Broadcast Type Services. In the case the user needs additional, specific material, this information could be downloaded using the interactive method (pull mode). Furthermore, the user can reply to the received information via the GSM link (e.g. e-mail to the author or for public auctioning).

Personal Services. DAB is used as a broadband extension to GSM data communication for downloading data to an individual user.

In overview, the DAB terminal is divided into three functional layers:
-The bottom layer consists of transport services and associated name services and is accessed via the low level API.
-The top layer consists of applications that are using the DAB services via the high level API. These applications may or may not be MEMO aware.
-Between the two API layers there is a service and session management layer. This layer contains functionalities that would otherwise have been contained in the applications themselves, thus allowing applications to be less complex and more easily developed. Applications can access the low level API directly and this is the case for legacy Internet applications.

The MEMO Terminal consists of two units:
-One for pre-processing of the data embedded into a DAB data stream.
-One for the application software.

The overall software structure for this system is based on the MEMO Terminal API. The two terminal parts are connected to each other by a wireless LAN interface, providing limited local mobility to the application part of the terminal system. The pre-processing part of the terminal (MEMO-Cube) consists in a PC/104 based computer system, running LINOX.

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