This paper focuses on Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems, where the MIMO channel order is larger than the length of the Cyclic Prefix (CP). By swapping the filtering operations of the MIMO channel and the Fast Fourier Transform (FFT), it is shown that each tone of a MIMO OFDM system can be viewed as a MIMO Single-Carrier (SC) system. This so-called pertone equalization (PTEQ) approach for MIMO OFDM systems is an attractive alternative for the recently developed time-domain equalization (TEQ) approach for MIMO OFDM systems.
This research paper proposes new time-domain and per-tone frequency-domain equalization techniques for OFDM transmission over time and frequency selective channels. One mixed time- and frequency-domain equalizer and one per-tone frequency-domain equalizer are presented. The Mixed Time and Frequency-domain Equalizer (MTFEQ) consists of a one-tap Time-Varying (TV) Time-domain Equalizer (TEQ), which converts the doubly-selective channel into a purely frequency-selective channel, followed by a one-tap Frequency-domain Equalizer (FEQ), which then equalizes the resulting frequency selective channel in the frequency-domain. The per-tone frequency-domain equalizer (FPTEQ) is then obtained by transferring the TEQ operation to the frequency-domain.
In this research paper, Katholieke Universiteit Leuven discusses new time-domain and per-tone frequency-domain equalization techniques for OFDM transmission over time- and frequency selective channels. They have presented one mixed time- and frequency-domain equalizer and one per-tone frequency-domain equalizer. An important feature of the proposed techniques is that no bandwidth expansion or redundancy insertion is required except for the cyclic prefix.
High-data rate techniques in communication systems have gained a considerable attraction in recent years. A technique of special interest is OFDM (Orthogonal Frequency Division Modulation) which is a multi-carrier modulation technique. This is due to its simple implementation and robustness against frequency selective channels by converting the channel into flat fading sub channels. OFDM has been standardized for a variety of applications such as Digital Audio Broadcasting (DAB), digital TV broadcasting, wireless LAN, and Asymmetric Digital Subscriber Lines (ADSL). Combining OFDM with multiple antennas has been shown to provide significant increase in capacity through the use of transmission diversity.