Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

TR-STBC equalisation receiver for WCDMA downlink

Space-time block coding (STBC) is a MIMO technique offering increase in robustness to fading by exploitation of spatial diversity in terrestrial wireless channels. STBC is highly suited to small, low power user terminals as it requires only low-complexity processing at the user terminal. However, STBC traditionally assumes frequency-flat fading, and so is not ideally suited for frequency-selective channels, such as the WCDMA links employed in third generation cellular wireless standards (e.g. UMTS). Time-reversal STBC (TR-STBC) allows both spatial and multipath delay diversity gains to be achieved over frequency-selective channels.

WCDMA standards such as UMTS use orthogonal spreading codes on the down-link to minimise multi-user interference. However multipath dispersion on frequency-selective channels causes this interference to reappear. Chip-level equalisation can be used to reverse the frequency-selective fading and remove the interference.

FLOWS has demonstrated a combination of TR-STBC techniques with chip-level equalisation applied to the WCDMA downlink. This allows spatial and multipath diversity to be exploited, with little deterioration in performance for the case of multiple active users per cell. UMTS-standard common pilot sequences were used for MIMO channel estimation, and the performance of the technique has been realistically evaluated on time-variant channels.

Reported by

University of York
Heslington -
YO1 5DD York
United Kingdom
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