Using only the receiver knowledge about the fading channel state, open-loop communication is possible. The main question, however, is whether we can improve
these schemes using channel information at the transmitter with a reasonable amount of complexity and overhead. In closed-loop schemes, transmitter knowledge
of the channel conditions is usually obtained using a feedback link from the receiver to the transmitter. Feedback information must be communicated over a reverse
channel in an adequately reliable and quick fashion. This is because communication over each realization of the channel cannot begin before the feedback link is
established. Moreover, the amount of communication resources, such as bandwidth and power dedicated to feedback information must be kept minimal so as not
to significantly affect the rest of the network and to impose the least possible interferences on other users. Should we keep the feedback information scarce, low
power, and prompt, we cannot help facing the issue of unreliable feedback information. Feedback errors and mismatches are extra sources of errors in a close-loop
system, degrading performance severely (even worse than an open-loop scheme). Our main focus in this study is to prevent this phenomenon and to design reliable
and high-rate communication schemes when the knowledge of the transmitter about the channel condition is limited and erroneous.
Javad Kazemitabar, Hamid Jafarkhani, and Siavash Ekbatani, “Code design for rank-deficient correlated channels,” IEE Electronics Letters, Vol. 41, October 2005.
S. Ekbatani, F. Etemadi, and H. Jafarkhani, “Outage behavior of quasi-static fading channels with partial power control and noisy feedback,” IEEE Global Comm. Conf. (GLOBECOM -07), November 2007.
S. Ekbatani and H. Jafarkhani, “Design of multi-antenna coded modulators using noisy quantized channel state information,” IEEE Global Comm. Conf. (GLOBECOM-06), November 2006.
S. Ekbatani, F. Fazel and H. Jafarkhani, “Space-time multi-block coding with covariance beam forming for mobile transceivers in block-fading channels,” IEEE Wireless Comm. and Net. Conf. (WCNC-06), April 2006.
S. Ekbatani and H. Jafarkhani “Novel space-time-frequency codes with improved distance spectrum for mobile multi-path channels,” IEEE Wireless Comm. and Networking Conf. (WCNC-06), April 2006.
S. Ekbatani, L. Liu and H. Jafarkhani, “A power loading scheme for space-time trellis codes based on channel magnitude feedback,” IEEE Global Comm. Conf. (GLOBECOM-05), November 2005.