Ran, J: Signal Processing, Channel Estimation and Link Adapt

The emerging wireless communication systems, such as cellular communications systems and wireless net-works, are changing the life style nowadays dramatically. The prospect of modern wireless communication systems is very attractive by declaring the ability of ubiquitous access to information with high-quality and high-speed service.

The Orthogonal Frequency Division Multiplexing (OFDM) technique is one promising candidate for the $4^{th}$ generation wireless systems, due to its merits of high flexibility and low equalization complexity for wideband wireless communication applications. To further enhance the communication system capacity and reliability, multiple antenna techniques can be integrated into OFDM systems.

As a preliminary step, the physical characteristics of wideband radio channels and the channel modeling issue are addressed. The channel capacity with multiple antennas is presented by considering both cases of ideal and practical estimated channel state information (CSI) in the system.

The fundamentals of the OFDM transmission technique are introduced. With the OFDM transmission structu-re the frequency-selective wideband radio channel is decomposed into a set of parallel subcarriers, and each subcarrier can be treated as a flat-fading narrowband channel.

Several Multiple-Input-Multiple-Output (MIMO) technologies are discussed, in the scope of subcarrier-based MIMO encoding and decoding within the MIMO-OFDM transceiver structure, i.\ e.\ integrate the MIMO signal processing algorithms into a wideband OFDM system, where each OFDM subcarrier is regarded individually as a narrowband flat-fading subsystem with the Discrete Fourier Transform (DFT) and Inverse Discrete Fou-rier Transform (IDFT). The simulation results and analysis are presented under various radio channel condi-tions with ideal CSI.

For practical reasons, channel estimation is necessary for coherent-detection MIMO-OFDM systems. The Pilot-based Channel Estimation