We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum.In the signal arm,object spatial information is encoded as a phase matrix.For an N−grey-scale object,different phase matrices...We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum.In the signal arm,object spatial information is encoded as a phase matrix.For an N−grey-scale object,different phase matrices,varying from 0 toπwith incrementπ/N,are used for different greyscales,and then they are modulated to a signal beam by a spatial light modulator.According to the conservation of the orbital angular momentum in the ghost imaging system,these changes will give different coincidence rates in measurement,and hence the object information can be extracted in the idler arm.By simulations and experiments,the results show that our scheme can improve the resolution of the image effectively.Compared with another encoding method using orbital angular momentum,our scheme has a better performance for both characters and the image object.展开更多
One of the main requirements of cognitive radio systems is the ability to detect the presence of the primary user with fast speed and precise accuracy. To achieve that, a possible two-stage spectrum sensing scheme is ...One of the main requirements of cognitive radio systems is the ability to detect the presence of the primary user with fast speed and precise accuracy. To achieve that, a possible two-stage spectrum sensing scheme is suggested in this paper. More specifically, a fast spectrum sensing algorithm based on the energy detection is introduced focusing on the coarse detection. A complementary fine spectrum sensing algorithm adopts one-order cyclostationary properties of primary user＇s signals in time domain. Since the one-order feature detection is performed in time domain, the real-time operation and low-computational complexity can be achieved. Also, it drastically reduces hardware burdens and power consumption as opposed to two-order feature detection. The sensing performance of the proposed method is studied and the analytical performance results are given. The results indicate that better performance can be achieved in proposed two-stage sensing detection compared to the conventional energy detector.展开更多
This article considers a wireless multi-hop/mesh network where single multi-antenna source-destination pair communicates through a selected relay subset using simple relay selection under the constraint of fixed relay...This article considers a wireless multi-hop/mesh network where single multi-antenna source-destination pair communicates through a selected relay subset using simple relay selection under the constraint of fixed relay＇s number. Compared with random selection, the simple relay selection can yield certain capacity advantages while linear zero-forcing （ZF） receiver and linear beamformer are considered at the relay. For match-filter （MF） beamformer and amplified-and-forward （AF） beamformer with a fixed number of relays, the capacities are given. Furthermore, we extend the simple selection methods to the relaying scheme with orthogonal-triangular （QR） beamformer and investigate these linear beamformer schemes over spatially correlated multi-input multi-output （MIMO） links for both the backward and forward channel over the two-bop MIMO relay networks.展开更多
基金Supported by the University Natural Science Research Foundation of Jiangsu Province(11KJA510002)the Foundation(No NJ210002)the Open Research Fund of Key Lab of Broadband Wireless Communication and Sensor Network Technology(Ministry of Education).
文摘We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum.In the signal arm,object spatial information is encoded as a phase matrix.For an N−grey-scale object,different phase matrices,varying from 0 toπwith incrementπ/N,are used for different greyscales,and then they are modulated to a signal beam by a spatial light modulator.According to the conservation of the orbital angular momentum in the ghost imaging system,these changes will give different coincidence rates in measurement,and hence the object information can be extracted in the idler arm.By simulations and experiments,the results show that our scheme can improve the resolution of the image effectively.Compared with another encoding method using orbital angular momentum,our scheme has a better performance for both characters and the image object.
基金supported by the National Natural Science Foundation of China (60972039,60972041)the Hi-Tech Research and Development Program of China (2009AA01Z241)+2 种基金the National Postdoctoral Research Program (20090451239)the Natural Science Fund for Higher Education of Jiangsu Province (09KJB510012)the Important National Science and Technology Specific Project of China (2009ZX03003-006)
文摘One of the main requirements of cognitive radio systems is the ability to detect the presence of the primary user with fast speed and precise accuracy. To achieve that, a possible two-stage spectrum sensing scheme is suggested in this paper. More specifically, a fast spectrum sensing algorithm based on the energy detection is introduced focusing on the coarse detection. A complementary fine spectrum sensing algorithm adopts one-order cyclostationary properties of primary user＇s signals in time domain. Since the one-order feature detection is performed in time domain, the real-time operation and low-computational complexity can be achieved. Also, it drastically reduces hardware burdens and power consumption as opposed to two-order feature detection. The sensing performance of the proposed method is studied and the analytical performance results are given. The results indicate that better performance can be achieved in proposed two-stage sensing detection compared to the conventional energy detector.
基金the National Natural Science Foundation of China (60772061)the OpenResearch Fund of National Mobile Communications Research Laboratory of Southeast University, the National Basic Research Program of China (2007CB310607)the Jiangsu Post doctoral Research Programs
文摘This article considers a wireless multi-hop/mesh network where single multi-antenna source-destination pair communicates through a selected relay subset using simple relay selection under the constraint of fixed relay＇s number. Compared with random selection, the simple relay selection can yield certain capacity advantages while linear zero-forcing （ZF） receiver and linear beamformer are considered at the relay. For match-filter （MF） beamformer and amplified-and-forward （AF） beamformer with a fixed number of relays, the capacities are given. Furthermore, we extend the simple selection methods to the relaying scheme with orthogonal-triangular （QR） beamformer and investigate these linear beamformer schemes over spatially correlated multi-input multi-output （MIMO） links for both the backward and forward channel over the two-bop MIMO relay networks.
