Hyoungsuk Lee - Profile on Academia.edu (original) (raw)
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We consider a physical layer security based on the wiretap channel for wireless communication sys... more We consider a physical layer security based on the wiretap channel for wireless communication systems in which there are one transmitter and multiple receivers/users who report their channel state information (CSI) to the transmitter. This scenario is practically useful since it models the forward link of cellular systems where the systems can take advantage of the multiuser diversity. We are curious about the role of the multiuser diversity in the secure communication under the wiretap channel framework. Although it is well known that fixed transmit power is not optimal when CSI is available to the transmitter, to get useful insights, we consider a fixed transmit power case. In return, we can have some of important performance measures such as outage probability, average secrecy rate, failure rate, and average wait time in closed forms. The analysis interestingly shows that the multiuser diversity becomes always disadvantageous for the secure communications. We substantiate our claims with the analytic results and numerical evaluations.
MIMO-OFDM system is one of the promising schemes for achieving high data rate in communication sy... more MIMO-OFDM system is one of the promising schemes for achieving high data rate in communication systems. In this paper, channel estimation techniques based on Loosely Synchronous (LS) codes are proposed for MIMO-OFDM systems. Since LS codes have perfect auto-correlation and crosscorrelation functions within certain vicinity of the zero shifts, multiple antenna and multipath signal interference can be reduced substantially. Through simulations, it is shown that the proposed methods outperform both of least square and linear minimum mean square error (LMMSE) estimators.
In this paper, we propose an efficient transmit strategy utilizing the partial channel informatio... more In this paper, we propose an efficient transmit strategy utilizing the partial channel information feedback for the QRD based V-BLAST systems. In the proposed scheme, after QR decomposition (QRD) of the channel matrix, positive real-valued diagonal elements of R are forwarded to the transmitter through the feedback channel. Based on the feedback information, the transmitter allocates the optimum transmit power to minimize the bit error rate (BER) of the system. With small feedback overhead, the proposed scheme shows significantly improved BER performance compare to the conventional sorted QR decomposition (SQRD) based V-BLAST systems. Moreover, we can reduce the receiver complexity by removing the unnecessary sorting process at the receiver.
We consider a physical layer security based on the wiretap channel for wireless communication sys... more We consider a physical layer security based on the wiretap channel for wireless communication systems in which there are one transmitter and multiple receivers/users who report their channel state information (CSI) to the transmitter. This scenario is practically useful since it models the forward link of cellular systems where the systems can take advantage of the multiuser diversity. We are curious about the role of the multiuser diversity in the secure communication under the wiretap channel framework. Although it is well known that fixed transmit power is not optimal when CSI is available to the transmitter, to get useful insights, we consider a fixed transmit power case. In return, we can have some of important performance measures such as outage probability, average secrecy rate, failure rate, and average wait time in closed forms. The analysis interestingly shows that the multiuser diversity becomes always disadvantageous for the secure communications. We substantiate our claims with the analytic results and numerical evaluations.
MIMO-OFDM system is one of the promising schemes for achieving high data rate in communication sy... more MIMO-OFDM system is one of the promising schemes for achieving high data rate in communication systems. In this paper, channel estimation techniques based on Loosely Synchronous (LS) codes are proposed for MIMO-OFDM systems. Since LS codes have perfect auto-correlation and crosscorrelation functions within certain vicinity of the zero shifts, multiple antenna and multipath signal interference can be reduced substantially. Through simulations, it is shown that the proposed methods outperform both of least square and linear minimum mean square error (LMMSE) estimators.
In this paper, we propose an efficient transmit strategy utilizing the partial channel informatio... more In this paper, we propose an efficient transmit strategy utilizing the partial channel information feedback for the QRD based V-BLAST systems. In the proposed scheme, after QR decomposition (QRD) of the channel matrix, positive real-valued diagonal elements of R are forwarded to the transmitter through the feedback channel. Based on the feedback information, the transmitter allocates the optimum transmit power to minimize the bit error rate (BER) of the system. With small feedback overhead, the proposed scheme shows significantly improved BER performance compare to the conventional sorted QR decomposition (SQRD) based V-BLAST systems. Moreover, we can reduce the receiver complexity by removing the unnecessary sorting process at the receiver.