Visible light communication (VLC) has been regarded as a promising solution in short-range intelligent communication system. Nowadays, the research is focused on integrating the multi-input multi-output (MIMO) techniq...
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ISBN:
(纸本)9781628413434
Visible light communication (VLC) has been regarded as a promising solution in short-range intelligent communication system. Nowadays, the research is focused on integrating the multi-input multi-output (MIMO) technique in the VLC system, to achieve a larger transmission capacity and stronger transmission reliability. However, one important issue should be addressed due to the use of MIMO technology: the multipath inter-symbol interference. The multipath inter-symbol interference comes from the reflection of the signal in the room and channel crosstalk between different channels. In this paper, we propose a novel optical system used in the MIMO VLC system to reduce multipath interference dramatically. Signals from different LEDs can be separated by using parabolic lens plated with reflecting film. This structure can reduce the reflection effect effectively as well. We present the simulation results to observe the distribution of optical power on the imaging plane for various receiving positions and low correlation between all channels. We can find that the optical power density becomes stronger than non-imaging system and the interference is sharply decreased, thus the SNR and BER are also optimized. Analysis about the optical system is given in this paper.
A novel scheme based on detection is proposed for half-duplex two-way relay system in this paper. multi-input multi-output and network coding technique are applied in the relay. The proposed method employs detection i...
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ISBN:
(纸本)9783037859032
A novel scheme based on detection is proposed for half-duplex two-way relay system in this paper. multi-input multi-output and network coding technique are applied in the relay. The proposed method employs detection in this system when the relay and two stations receive signal. Theoretical and simulative analyses of the protocol performance under the assumption of a binary symmetric relay channel model are carried out. The zero-forcing detection and maximum likelihood detection are respectively used. The simulation results show that the new scheme facilitates more reliable transmission and higher information transmission rate.
Recently, it has been shown that applying MIMO technology, i.e. using multiple antennas at the transmit side and multiple antennas at the receive side, improves the performance of object detection and localization. In...
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Recently, it has been shown that applying MIMO technology, i.e. using multiple antennas at the transmit side and multiple antennas at the receive side, improves the performance of object detection and localization. In such scenarios, the spatial diversity specifically helps overcome the fading of the cross section of the object, leading to reduced probability of missed detection. Such a phenomenon is, in fact, the dual of probability of bit error reduction in communication systems due to diversity gain. Despite the importance of such performance enhancement, this subject has not been sufficiently investigated in the PCL (Passive Coherent Location) schemes, where the transmitters (or illuminators of opportunity) used for localization are already present in the environment. Especially, in cases where the transmitters are working in a SFN (Single Frequency Network), such as the DVB-T (Digital Video Broadcasting-Terrestrial) signal, and all are transmitting the same signal, the situation becomes of higher importance. Obviously, the effect of the SFN environment invalidates the assumption of sending orthogonal waveforms traditionally used in localization schemes. In this paper, we design the Neyman-Pearson detector for a PCL scheme and show that we can achieve the desired diversity gain for such a design as well. (C) 2014 Sharif University of Technology. All rights reserved.
This paper addresses adaptive modulation and power allocation for maximizing the practicable sum capacity (sum of the uncoded throughputs of the users) of a multiuser multiple-input single-output (MU-MISO) system. Sin...
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ISBN:
(纸本)9781479944484
This paper addresses adaptive modulation and power allocation for maximizing the practicable sum capacity (sum of the uncoded throughputs of the users) of a multiuser multiple-input single-output (MU-MISO) system. Since the optimal solution, dirty paper encoding (DPC), is complicated to implement, we use the simpler linear precoding based on signal-to-leakage-plus-noise ratio (SLNR). For different choices of constellation sizes, the maximum practicable sum capacities and their corresponding optimal power allocations are obtained via individual non-convex optimization. The best constellation sizes for each user are then identified through a search for the highest maximized practicable sum capacity. Simulations demonstrate the significant performance improvement from this approach compared to existing power allocation schemes. Finally, a selection procedure between different constellation sets is presented to obtain the highest practicable sum capacity while maintaining the instantaneous BER of each user below a target value. This approach allows management of the trade-off between the capacity and error performances.
Video broadcasting is an efficient way to deliver video content to multiple receivers. However, due to heterogeneous channel conditions in MIMO wireless networks, it is challenging for video broadcasting to map scalab...
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Video broadcasting is an efficient way to deliver video content to multiple receivers. However, due to heterogeneous channel conditions in MIMO wireless networks, it is challenging for video broadcasting to map scalable video layers to proper MIMO transmit antennas to minimize the average overall video transmission distortion. In this paper, we investigate the channel scheduling problem for broadcasting scalable video content over MIMO wireless networks. An adaptive channel scheduling based unequal error protection (UEP) video broadcasting scheme is proposed. In the scheme, video layers are protected unequally by being mapped to appropriate antennas, and the average overall distortion of all receivers is minimized. We formulate this scheme into a non-linear combinatorial optimization problem. It is not practical to solve the problem by an exhaustive search method with heavy computational complexity. Instead, an efficient branch-and-bound based channel scheduling algorithm, named TBCS, is developed. TBCS finds the global optimal solution with much lower complexity. The complexity is further reduced by relaxing the termination condition of TBCS, which produces a (1 - epsilon)-optimal solution. Experimental results demonstrate both the effectiveness and efficiency of our proposed scheme and algorithm. As compared with some existing channel scheduling methods, TBCS improves the quality of video broadcasting across all receivers significantly. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
Coupled-core multi-core fibers (MCFs) offer characteristics that are beneficial for long-haul spatially multiplexed transmission. Using full-vector solution of the wave equation, we study the number of propagating mod...
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Coupled-core multi-core fibers (MCFs) offer characteristics that are beneficial for long-haul spatially multiplexed transmission. Using full-vector solution of the wave equation, we study the number of propagating modes and several modal characteristics, including intermodal beat lengths, group delay spread, mode-dependent chromatic dispersion, and intramodal and intermodal effective areas. We identify a range of design parameters that simultaneously optimizes these characteristics. Our results demonstrate the limited accuracy of perturbation-based analyses in characterizing MCFs with closely spaced cores.
In this article, a dual-band WLAN/ultrawideband (UWB) printed wide slot microstrip-fed antenna is presented for multi-input multi-output (MIMO)/diversity *** proposed antenna consists of a U-shaped patch, a T-shaped m...
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In this article, a dual-band WLAN/ultrawideband (UWB) printed wide slot microstrip-fed antenna is presented for multi-input multi-output (MIMO)/diversity *** proposed antenna consists of a U-shaped patch, a T-shaped monopole path, and a pentagonal wide slot in the ground plane. The antenna is designed to cover both the WLAN (2.42.485 GHz) and UWB (3.110.6 GHz) ranges, with value of S11 below -10 dB. The antenna is constructed on a FR4 substrate with overall dimensions of 28 x 28 x 1 mm3. It is shown that the proposed dual-band antenna is suitable for diversity polarization applications. The simulation results show that the different configurations of the antenna in the MIMO/diversity have good S-parameters over the operating frequency bands. The simulation and measured results of the proposed dual-band antenna as well as that of the MIMO/diversity antenna configuration agree well. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:461465, 2013;View this article online at ***. DOI 10.1002/mop.27391
This brief paper presents multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with dual-polarized division multiplexing (PDM) and diversity for multimedia broadcasting services. In ...
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This brief paper presents multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with dual-polarized division multiplexing (PDM) and diversity for multimedia broadcasting services. In particular, the polarized diversity is realized by transmitting two independent and distributed space-frequency coded signals through two sets of dual-polarized transmit antennas. In the corresponding polarized receptions, MIMO zero-forcing (ZF) detection and ZF detection combined with a group-wise or a symbol-wise successive cancelation (SIC) are used to minimize a depolarization effect caused by a cross-polarization discrimination (XPD). Furthermore, we analyze the output signal-to-interference-plus-noise ratio (SINR) of such MIMO detections in terms of the XPD effect. It is shown that the output SINR of MIMO ZF detection increases as the absolute XPD value increases. It is also shown that the output SINR of ZF-SIC detection converges to that of ZF detection as the absolute XPD value increases. Finally, we compare the performances of uni-polarized and dual-polarized MIMO-OFDM systems over a multipath Rician channel with XPD. From simulation results, we conclude that as the absolute XPD value increases, the polarized MIMO-OFDM systems provide a lower symbol error rate than uni-polarized MIMO-OFDM systems.
The problem of joint beamforming and power allocation for cognitive multi-input multi-output systems is studied via game theory. The objective is to maximize the sum utility of secondary users (SUs) subject to the pri...
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The problem of joint beamforming and power allocation for cognitive multi-input multi-output systems is studied via game theory. The objective is to maximize the sum utility of secondary users (SUs) subject to the primary user (PU) interference constraint, the transmission power constraint of SUs, and the signal-to-interference-plus-noise ratio (SINR) constraint of each SU. In our earlier work, the problem was formulated as a non-cooperative game under the assumption of perfect channel state information (CSI). Nash equilibrium (NE) is considered as the solution of this game. A distributed algorithm is proposed which can converge to the NE. Due to the limited cooperation between the secondary base station (SBS) and the PU, imperfect CSI between the SBS and the PU is further considered in this work. The problem is formulated as a robust game. As it is difficult to solve the optimization problem in this case, existence of the NE cannot be analyzed. Therefore, convergence property of the sum utility of SUs will be illustrated numerically. Simulation results show that under perfect CSI the proposed algorithm can converge to a locally optimal pair of transmission power vector and beamforming vector, while under imperfect CSI the sum utility of SUs converges with the increase of the transmission power constraint of SUs.
A rectangular slot antenna fed by a coplanar waveguide is proposed for dual-band wireless local area network (WLAN) operations. The measured 210-dB bandwidth for return loss is from 2.1 to 2.95 GHz and 5.05 to 6.25 GH...
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A rectangular slot antenna fed by a coplanar waveguide is proposed for dual-band wireless local area network (WLAN) operations. The measured 210-dB bandwidth for return loss is from 2.1 to 2.95 GHz and 5.05 to 6.25 GHz, covering all the 2.4/5-GHz WLAN bands. A multifeed four-element planar array was designed and simulated. It shows that the features of small size, uniplanar structure, good radiation characteristics, and small mutual coupling are promising for multi-input multi-output applications. (c) 2013 Wiley Periodicals, Inc.
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