Résumé des résultats (Abstract)
(Anglais)
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Broadband interactive multimedia information service are rapidly emerging. Use of the Internet continues to grow exponentially. The technological goal behind the MAD project was to help extend advanced multimedia and high-speed Internet services to home users. Specifically, MAD involved multimedia data delivery to the home and high bit-rate wireless interconnection in the home.
ACCESS TO THE HOME IS VIA ATM OVER xdsl (8 Mbps). Within the home, wireless connectivity is provided by a Hiperlan type 2 (Hiperlan/2) wireless local area network (WLAN), which WLAN operates at 25 Mbps. The multimedia data is delivered to a set-top-box connected to the residential gateway through a firewire link (IEEE1394).
In terms of research, the main challenges concern the physical hiperlan/2 link (i.e., baseband for synchronization, channel estimation, equalization and quality-of-service (qos) over the time-varying channel). Hiperlan/2 is based on OFDM, which is sensitive to synchronization problems. Multimedia information services have different qos requirements dependent on the service class. CSEM was mainly involved in the specification, design and development of a Hiperlan/2 wireless access point (WAP) and mobile terminal.
For the DLC layer, Hiperlan/2 specifications (which are undergoing standardization) were completely analyzed. Quality of service negotiation and provision was studied. Adaptive schemes for adaptation to the channel were pproposed to maintain the negotiated parameter of a Hiperlan/2 connection. Hiperlan/2 DLC layer was completely specified in SDL and simulated. The control plane of Hiperlan/2 was generated from the SDL specification. Because the C code generated using SDT is not optimal and because the transport plan of a protocol stack has to be very efficient, thus the transport plane was implemented from scratch in C++. The implementation was done in a genereric to allow an easy reuse.
AT THE PHYSICAL LAYER, HIPERLAN/2 EMPLOYS MULTIPLE ofdm SUBCARRIERS, WHICH REQUIRE TIGHT SYNCHRONIZATION FOR PROPER OPERATION. the requirements for synchronization are complicated by the combination of high data rate indoor wireless transmission and the use of orthogonal frequency division multiplexing (ofdm). synchronization may be viewed as a two step process; 1) coarse synchronization (acquisition) and 2) fine synchronization (tracking). Both coarse and fine hiperlan/2 synchronization techniques and algorithms were studied and novel techniques were proposed and evaluated for improving coarse synchronization. the results of csems woRK ON COARSE SYNCHRONIZATION TECHNIQUES WERE PRESENTED AT ieeevtc'99.
fOLLOWING THE WITHDRAWAL OF THE MAIN PARTNER (DUE TO INTERNAL REORGANISATION), THE PROJECT WAS INTERRUPTED AFTER A LITTLE MORE THAN A YEAR OF WORK. CSEM WAS AUTHORIZED TO ACHIEVE SOME IMPORTANT WORKS IN THE DOMAIN OF FINE SYNCHRONISATION AND TRACKING ALGORITHMS FOR OFDM, IN ORDER to allow a reasonable exploitation of the obtained results.
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