Bit interleaved coded modulation with space time block codes for OFDM systems

Abstract

Wireless systems often implement one or more types of diversity in order to achieve reliable communication. Different types of diversity techniques such as temporal, frequency, code, and spatial have been developed. Besides the destructive multipath nature of wireless channels, frequency selective channels pose intersymbol interference (ISI) while offering frequency diversity for well designed systems. Orthogonal frequency division multiplexing (OFDM) combats ISI very well by converting the frequency selective channel into parallel flat fading channels. On the other hand, bit interleaved coded modulation (BICM) has a high performance for flat fading Rayleigh channels. The combination of BICM and OFDM exploits the diversity that is inherited within frequency selective fading channels. Hence, BICM-OFDM is a very effective technique to provide diversity gain., employing frequency diversity. Orthogonal space-time block codes (STBC) make use of spatial diversity by coding in space and time. Thus, diversity in frequency and space can be taken advantage of by combining BICM-OFDM and STBC. We show and quantify both analytically and via simulations that, for frequency selective fading channels, BICM-STBC-OFDM systems can fully and successfully exploit frequency and space diversity to the maximum available extent.