Turbo coded HSDPA systems with transmit diversity over frequency selective fading channels

Transmit diversity is one of the key contributions to the 3G (third generation) WCDMA (wide-band code division multiple access) systems to accommodate high data-rate applications, where spatial diversity is introduced into the signal by transmitting through multiple antennas. While turbo codes are well understood to be able to provide powerful error correction ability in a SISO (single input single output) system, therefore achieve improved system performance, space-time block coded (STBC) MIMO (multiple input multiple output) transmission is receiving more and more interests as an effective method to combat adverse effects of fading, improve the performance and increase the capacity. This paper addresses the issue of introducing space-time coding to turbo coded HSDPA (high-speed downlink packet access) systems in order to obtain both diversity gain and coding gain. This novel scheme extends STBC, originally proposed for perfectly known frequency nonselective fading channels to frequency selective fading channels. Channel equalization is utilized to mitigate the intersymbol interference (ISI) caused by multipath propagation. Numerical results are presented to reveal the performance merits of the proposed system gained by using turbo space-time coding.