In Vehicle-to-Vehicle (V2V) communication, the rapid movement of vehicles brings fast attenuation of signal propagation and serious shift effect of Doppler frequency, leading to serious transmission performance deteri...
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In Vehicle-to-Vehicle (V2V) communication, the rapid movement of vehicles brings fast attenuation of signal propagation and serious shift effect of Doppler frequency, leading to serious transmission performance deterioration. multiple-input multiple-output (MIMO) technique can be well applied in V2V communication by exploiting diversity and multiplexing gain to improve the system reliability and increase the data rate. In an MIMO system, the achieved diversity and multiplexing gain is closely related to its detection method. Integer-Forcing (IF) detection is one of the linear detections proposed in recent years. Compared to the traditional linear and Maximum Likelihood (ML) detection, IF has a good tradeoff between the complexity and system performance. In this paper, considering its good detection performance, IF is applied to the detection of a MIMO V2V communication system and the performance is further analyzed theoretically by employing Alamouti code at the transmitters. The diversity gain proves to be full and is confirmed by the simulation results. (C) 2018 Elsevier B.V. All rights reserved.
Unlike the time-division duplexing systems, the down-link (DL) and uplink (UL) channels are not reciprocal in the case of frequency-division duplexing (FDD). However, some long-term parameters, e.g., the time delays a...
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Unlike the time-division duplexing systems, the down-link (DL) and uplink (UL) channels are not reciprocal in the case of frequency-division duplexing (FDD). However, some long-term parameters, e.g., the time delays and angles of arrival of the channel paths, enjoy reciprocity. In this paper, by efficiently exploiting the aforementioned limited reciprocity, we address the DL channel state information (CSI) feedback in a practical wideband massive multiple-input multiple-output system operating in the FDD mode. With orthogonal frequency-division multiplexing waveform and assuming frequency-selective fading channels, we propose a scalable framework for the DL pilots design, DL CSI acquisition, and the corresponding CSI feedback in the UL. In particular, the base station (BS) can transmit the FFT-based pilots with carefully selected phase shifts. Then, the user can rely on the so-called time-domain aggregate channel to derive the feedback of reduced dimensionality according to either its own knowledge about the statistics of the DL channels or the instruction from the serving BS. We demonstrate that each user can just feed back one scalar number per DL channel path for the BS to recover the DL CSIs. Comprehensive numerical results further corroborate our designs.
We develop a general framework for the analysis of a broad class of point-to-point linear multiple-input multiple-output (MIMO) transmission schemes in decentralized wireless ad hoc networks. New general closed-form e...
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We develop a general framework for the analysis of a broad class of point-to-point linear multiple-input multiple-output (MIMO) transmission schemes in decentralized wireless ad hoc networks. New general closed-form expressions are derived for the outage probability, throughput and transmission capacity. For the throughput, we investigate the optimal number of data streams in various asymptotic regimes, which is shown to be dependent on different network parameters. For the transmission capacity, we prove that it scales linearly with the number of antennas, provided that the number of data streams also scales linearly with the number of antennas, in addition to meeting some mild technical conditions. We also characterize the optimal number of data streams for maximizing the transmission capacity. To make our discussion concrete, we apply our general framework to investigate three popular MIMO schemes, each requiring different levels of feedback. In particular, we consider eigenmode selection with MIMO singular value decomposition, multiple transmit antenna selection, and open-loop spatial multiplexing. Our analysis of these schemes reveals that significant performance gains are achieved by utilizing feedback under a range of network conditions.
The rapid development of mobile communications requires even higher spectral efficiency. Non-orthogonal multiple access (NOMA) has emerged as a promising technology to further increase the access efficiency of wireles...
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The rapid development of mobile communications requires even higher spectral efficiency. Non-orthogonal multiple access (NOMA) has emerged as a promising technology to further increase the access efficiency of wireless networks. Among several NOMA schemes, it has been shown that sparse code multiple access (SCMA) is able to achieve better performance. In this paper, we consider a downlink MIMO-SCMA system over frequency selective fading channels. For optimal detection, the complexity increases exponentially with the product of the number of users, the number of antennas and the channel length. To tackle this challenge, we propose near optimal low-complexity iterative receivers based on factor graph. By introducing auxiliary variables, a stretched factor graph is constructed and a hybrid belief propagation (BP) and expectation propagation (EP) receiver, named stretch-BP-EP, is proposed. Considering the convergence problem of BP algorithm on loopy factor graph, we convexify the Bethe free energy and propose a convergence-guaranteed BP-EP receiver, named conv-BP-EP. We further consider cooperative network and propose two distributed cooperative detection schemes to exploit the diversity gain, namely, belief consensus-based algorithm and the Bregman alternative direction method of multipliers (ADMM)-based method. Simulation results verify the superior performance of the proposed conv-BP-EP receiver compared with other methods. The two proposed distributed cooperative detection schemes can improve the bit error rate performance by exploiting the diversity gain. Moreover, Bregman ADMM method outperforms the belief consensus-based algorithm in noisy inter-user links.
A compact 5.5 GHz band-notched ultra-wideband (UWB) 2-element antenna with high isolation for multiple-input multiple-output (MIMO) portable wireless devices in wireless personal area network (WPAN) application is pro...
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A compact 5.5 GHz band-notched ultra-wideband (UWB) 2-element antenna with high isolation for multiple-input multiple-output (MIMO) portable wireless devices in wireless personal area network (WPAN) application is proposed. The MIMO antenna is designed for 3.1-10.6 GHz range on Neltec substrate with compact dimension of 43 x 20 mm(2) and is tested experimentally. For the rejection band at 5.5 GHz, a slot of length 1.0 is etched into the radiator. Simple structure, i.e., receded steps at ground are used to improve isolation by 3 dB between two UWB antennas. The simulated and measured results show |S-11|-10 dB and |S-21|-20 dB in most of the frequency range excluding the reject band at 5.5 GHz in UWB range. The measured, simulated and calculated results show that the proposed UWB MIMO antenna is a good candidate for UWB MIMO systems. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1390-1394, 2016
A broadband multiple-input multiple-output antenna with a size of 60 x 120 x 1.6 mm is presented for the smart phones. Enhanced performance of the antenna is achieved by utilizing dual radiator chopping and ground pla...
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A broadband multiple-input multiple-output antenna with a size of 60 x 120 x 1.6 mm is presented for the smart phones. Enhanced performance of the antenna is achieved by utilizing dual radiator chopping and ground plane slitting. Supplemental L-shaped meandered ground structure over the top of radiator was added to enhance the performance in the lower frequency band. The proposed antenna covers two frequency bands for return loss <-6 dB, that is, 0.8-0.96 and 1.7-2.7 GHz, respectively, specified for mobile phone operation. The antenna is fabricated and measured results are obtained for return loss, isolation, envelope correlation, and radiation pattern. (C) 2014 Wiley Periodicals, Inc.
In this letter, antenna diversity is used to improve the outage performance of downlink multiple-input multiple-output non-orthogonal multiple access systems with partial channel state information, of which the transm...
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In this letter, antenna diversity is used to improve the outage performance of downlink multiple-input multiple-output non-orthogonal multiple access systems with partial channel state information, of which the transmitter only knows the distance and channel direction information associated with each user. We analyze the ergodic rate and the outage probability of the proposed system. Moreover, we derive the closed-form expression of each user's outage probability. Numerical results confirm the accuracy of our analysis.
In this letter, we introduce accurate approximation expressions for composite fading channel model and outage probability of multiple-input multiple-output (MIMO) free space optical (FSO) link between two unmanned aer...
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In this letter, we introduce accurate approximation expressions for composite fading channel model and outage probability of multiple-input multiple-output (MIMO) free space optical (FSO) link between two unmanned aerial vehicles (UAVs) in hovering state. In our derivations, we consider the effects of weather attenuation, random fluctuations in UAVs' positions and orientations, and atmospheric turbulence. Our proposed model is unified with respect to turbulence effect, which means it is valid for different atmospheric turbulence models. We show the accuracy of the proposed model through comparisons with Monte Carlo simulations under different channel conditions.
The design of a novel circularly polarized (CP) modified slot multiple-input multiple-output (MIMO) antenna for WLAN applications with a small size of 20 x 20 mm(2) is suggested. The MIMO antenna configuration consist...
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The design of a novel circularly polarized (CP) modified slot multiple-input multiple-output (MIMO) antenna for WLAN applications with a small size of 20 x 20 mm(2) is suggested. The MIMO antenna configuration consists of two stepped open-circuit feed-lines to enhance the input matching condition, a square ground plane with circularly etching and two arc-shape slotted stubs along the two opposite edges to produce the CP functionality. To accredit the simulation results, the prototypes of the suggested CP modified slot MIMO antenna are constructed on an inexpensive FR-4 substrate and tested. The outcomes exhibit a 6% (330 MHz, 5.10-5.43 GHz) 3dB axial-ratio bandwidth, and the measured 10-dB impedance bandwidth is 62.9% (4720 MHz, 4,92-9.64 GHz). Antenna feed-lines are Microstrip-Microstrip to gain a high isolation and low envelope correlation between the two input ports. Fine efficiency of the propounded antenna over the working bands are also received. The outcomes demonstrate, which the antenna can be evaluated as a suitable choice for CP MIMO systems. (C) 2017 Wiley Periodicals, Inc.
Decision-feedback equalization is considered for point-to-point multiple-input multiple-output visible light communication systems. Based on the geometric mean decomposition (GMD) and uniform channel decomposition (UC...
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Decision-feedback equalization is considered for point-to-point multiple-input multiple-output visible light communication systems. Based on the geometric mean decomposition (GMD) and uniform channel decomposition (UCD), two precoders under the signal non-negativity and total average power constraints are designed for such systems. The GMD scheme can decompose the channel into multiple parallel sub-channels with equal gains. The UCD scheme further improves performance through power allocation. Simulation results of bit-error-rate and capacity are presented. It is shown that the proposed schemes can outperform conventional linear designs and the UCD scheme performs better than the GMD scheme.
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