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A Novel Frame Synchronization for MIMO-OFDM Transmission System
Yuhei Nagao,Kenichi Kubo,Masayuki Kurosaki,Hiroshi Ochi 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
MIMO-OFDM system, such as IEEE802.11n wireless LAN and IEEE802.16e wireless MAN, employs cyclic shift diversity transmission in order to avoid unintended beam-forming. However, such system reduces the accuracy of frame synchronization due to large value of channel root mean square (RMS) delay spread, which is observed at receiver. This paper proposes a novel frame synchronization scheme for high accuracy in large RMS delay spread channel environment. The simulation results show that the proposed scheme can improve the performance of the packet error rate and synchronization error rate in IEEE802.11 TGn channel model B with the RMS delay spread of 15[㎱] and model E with RMS delay spread of 100[㎱].
Low Complexity Iterative Precoder for Downlink MU-MIMO Systems
Naotaka Yoshida,Yuji Yokota,Yuhei Nagao,Hiroshi Ochi 대한전자공학회 2015 ITC-CSCC :International Technical Conference on Ci Vol.2015 No.6
Block diagonalization (BD) precoder is used for Multi-User Multiple Input Multiple Output (MU-MIMO) IEEE 802.11ac Wireless LAN. To improve the latency of the MU-MIMO systems, the BD precoder using iterative calculation has been proposed. We call this method Iterative BD (IBD). IBD can start the MU-Precoder weight matrix calculation even before all user’s channel state information (CSI) are received. However IBD has a higher complexity compared to non-iterative BD because of the overhead of iterative calculation. In this paper, we reduce the complexity due to the iteration process by computing the null space needed in the IBD method together with the channel matrix decompression which is applied by CSI feedback process based on IEEE802.11ac. We show that our method can significantly reduce the complexity of IBD.