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MIMO OFDM is a very promising technique for high-speed wireless transmission. By applying the Direct Conversion Architecture (DCA), low-cost, low-power and fully integrated implementation of such systems is enabled. However, the performance of DCA may be seriously limited by I/Q-imbalance, which shows frequency selectivity in broadband systems. In this paper, we consider an indoor scenario and present...
For communication systems with direct-conversion architecture, I/Q-imbalance can be a crucial performance limiting effect. Furthermore, as the datarates of the wireless communication systems increase, larger transmission bandwidths (BW) and high-order modulated waveforms are applied. As a result, the systems are sensitive to frequency dependent I/Q-imbalance and the corresponding calibration is more...
OFDM signals have sidelobes in the spectrum, causing interference to the neighboring frequency channels in a cellular system. The sidelobes can be suppressed by raised cosine (RC) windowing in time domain, while the inter-cell interference can be suppressed by reserving a guardband between neighboring frequency channels. A higher roll-off factor (ROF) of the RC window leads to better sidelobe suppression...
In this paper, channel estimation schemes as well as low crest-factor preamble construction are presented for practical MIMO OFDM systems with NULL subcarriers. In the presence of NULL subcarriers, the performance of the channel estimator in [1] degrades considerably. Therefore, Maximum-likelihood (ML) channel estimators were proposed for MIMO OFDM systems with NULL subcarriers [2], [3]. However,...
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