Basal plane bending of 4H-SiC single crystals grown using the sublimation method on an open or closed backside seed was measured using high-resolution X-ray diffractometry.
In this work, we investigate the closed loop extended orthogonal-space time block codes in decodeand-forward cooperative networks and propose an updatable automatic repeat request protocol with relay selection. In the system, the relays decoding correctly are incorporated into a relay set, the optimal relays within this relay set can be selected based on the channel information, and the extended orthogonal-space time block codes scheme is employed with the help of the feedback in automatic repeat request message. With the consideration of the relay selection, the system performance can be improved. Simulation and analysis results prove the efficiency of the proposed scheme, which achieves better performance than conventional relay schemes.. After that, he has been an associate professor in the School of Information Science and Engineering, Shandong University, China. He is also a member of IEEE and serves as associate editor, TPC member, and session chair of international journals and conferences. His current research fields include cooperative communication and MIMO systems, ultra-wideband communications, cognitive radio, and advanced channel coding and modulation schemes.
Cooperative spectrum sensing provides more accurate detection of the primary user's activity in cognitive radio (CR) systems. Since the report channels between the cognitive users and base station (BS) are imperfect, a transmit diversity scheme is also employed to improve the decision performance. Different clusters with space time block codes (STBC) are assigned to report the decision by TDMA method to BS. However, if a cluster reports sensing decisions to BS in the reporting slot, the other clusters do nothing but wait for their orders and the time efficiency will decrease. Here, we set the clusters in waiting status do not stop the spectrum sensing to improve the time efficiency. In this case, different clusters will get different sensing durations and energy consumption will not lead to the performance improvement certainly. To solve this problem, we assign the clusters with high sensing sensitivity different sensing durations to decrease energy consumption. Simulation results show that the proposed scheme improves the sensing performance significantly.
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