In this paper, a combination system of multi-antenna multipleinputmultipleoutput (MIMO) and non-orthogonal multiple access (NOMA) technologies is investigated, in which the source communicates with users using a mu...
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In this paper, a combination system of multi-antenna multipleinputmultipleoutput (MIMO) and non-orthogonal multiple access (NOMA) technologies is investigated, in which the source communicates with users using a multiple amplify-and-forward (AF) relaying network. These relay nodes are equipped with a single antenna and employ a power-splitting protocol to harvest energy from received signals, whereas the source and users are multiple-antenna nodes. In addition, two antenna-relay selection methods are considered to enhance the harvested energy at the relay including the maximum ratio transmission (MRT) and transmit antenna selection (TAS) at the source, with maximal-ratio combining at the users, these methods are compared to the performance of the random selection (RS) scheme. To evaluate the performance of the proposed system, we derive analytical expressions of the outage probability and throughput for the MRT and TAS schemes over Rayleigh fading channels, and use a Monte Carlo simulation to verify the accuracy of the analytical results. The results demonstrate the benefit of using MRT and TAS schemes, which provide a better performance than RS schemes, in a MIMO/NOMA system. Moreover, these results characterize the effects of various system parameters, such as power allocation factors, the numbers of antenna and relay nodes, power-splitting ratio, successive interference cancellation and energy-harvesting efficiency, on the system performance of two users of MIMO/NOMA. This is further compared with multiple-antenna conventional orthogonal multiple access (MIMO/OMA) schemes.
A novel approach to analyzing the performance of the V-BLAST multi-input multi-output systems with two transmit antennas is presented in this letter. Based on the properties of Wishart matrices, we derive the exact SN...
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A novel approach to analyzing the performance of the V-BLAST multi-input multi-output systems with two transmit antennas is presented in this letter. Based on the properties of Wishart matrices, we derive the exact SNR distributions in the first and second detection steps when optimal detection ordering is used. Closed-form analytical expressions for the bit error rates are then given. The effect of optimal ordering on the diversity order and SNR is evaluated. The results are found to be consistent with those previously published by other researchers.
In this paper, we provide the capacity limits of multiple-input multiple-output (MIMO) free-space optical communication (FSO) system in the presence of quality of service (QoS) requirements. Closed-form expression for...
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In this paper, we provide the capacity limits of multiple-input multiple-output (MIMO) free-space optical communication (FSO) system in the presence of quality of service (QoS) requirements. Closed-form expression for the effective capacity of MIMO FSO system with equal gain combining (EGC) is derived. In order to provide insights into the impact of various system parameters, asymptotic expressions are further analyzed in the high signal-to-noise ratio (SNR) regime. Special cases are provided according to the derived results at the same time. Numerical results are given to validate all the analytical results, and the influences of QoS requirements and MIMO configurations are also illustrated. (C) 2016 Elsevier B.V. All rights reserved.
Free-space optics (FSO) is a safe, license-free, high speed and high-bandwidth cordless technique for broadcasting signals at the same speed as fiber optics. But the main drawback of FSO is the dissolution of the sign...
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Free-space optics (FSO) is a safe, license-free, high speed and high-bandwidth cordless technique for broadcasting signals at the same speed as fiber optics. But the main drawback of FSO is the dissolution of the signals due to atmospheric turbulence and thus degrading the link performance. So, to enhance the bit error rate (BER) performance, spatial diversity is employed over the FSO links for single-inputmultiple-output FSO (SIMO-FSO) systems. In this paper, we analyze the BER performance of SIMO-FSO links with spatial diversity and multiple-input multiple-output FSO (MIMO-FSO) systems over gamma-gamma atmospheric turbulence fading channel with misalignment (pointing errors). The closed form expressions are derived for the same with various combining schemes in terms of the Meijer G function and also evaluate the results with 2D and 3D graphs. (C) 2014 Elsevier GmbH. All rights reserved.
Spatial diversity techniques are usually used to mitigate the influence of turbulence in the free-space optical communication (FSOC) with photon-counting receivers, especially when the communication links are weak. A ...
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Spatial diversity techniques are usually used to mitigate the influence of turbulence in the free-space optical communication (FSOC) with photon-counting receivers, especially when the communication links are weak. A maximum likelihood (ML) detection can be directly applied to the outputs of photon-counting receivers. However, it is challenging to obtain an analytical error probability for the ML detection. In this letter, we derive the analytical error probability of the ML detection under both turbulent and non-turbulent cases by equivalently considering L detected photons;and the approximating error is in the order of magnitude O(?(L)b/L!), where ?(b) is the back -b ground noise. Besides, we prove that the ML detection equals a threshold detection following an equal-gain combining when the signal strengths are close to each other in non-turbulent cases. Numerical results show that L < 10 is sufficient for typical scenarios with small background noises ?(b) < 1. Besides, we demonstrate that the derived analytical error probability can achieve a higher precision and computational efficiency compared with Monte-Carlo methods.
In conventional concatenations of Convolutional Codes (CC) and Space-Time Block Codes (STBC), the CC and STBC are utilized to provide coding gain and spatial diversity, respectively. We propose a concatenated code tha...
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In conventional concatenations of Convolutional Codes (CC) and Space-Time Block Codes (STBC), the CC and STBC are utilized to provide coding gain and spatial diversity, respectively. We propose a concatenated code that achieves the full system diversity by appropriately selecting the outer CC with an inner reduced-rank STBC. The advantage of the lower rank STBC is that the number of RF chains can be reduced. For any number of RF chains, R, we show that a desirable diversity order Y can be easily achieved i.e., 1 <= R <= Y. Using trellis diagram, we formalize the method to determine the maximum diversity.
This letter considers the near-field beamforming in millimeter wave Internet-of-vehicle, where phased arrays have been widely used for mitigating misfocus effect. In near-field regime, the angle and distance need to b...
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This letter considers the near-field beamforming in millimeter wave Internet-of-vehicle, where phased arrays have been widely used for mitigating misfocus effect. In near-field regime, the angle and distance need to be considered simultaneously due to the fact that the wave propagation is spherical. We design the phase profile of the antenna arrays by using the angle and distance information to meet characteristic of near-field spherical wavefront. Then, we construct the chirp signal based on the hybrid frequency modulation technique to improve Doppler sensitivity to compensate the effect caused by the movement of the vehicles. Our results reveal that the proposed method can achieve high data rates by reducing the beam misfocus and Doppler effect in millimeter wave Internet-of-vehicle.
The full-duplex (FD) single-user multiple-input-multiple-output (SU-MIMO) sum-rate maximization problem leads to a nonconvex optimization problem. In this paper, we introduce a maximum self-interference threshold (SIT...
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The full-duplex (FD) single-user multiple-input-multiple-output (SU-MIMO) sum-rate maximization problem leads to a nonconvex optimization problem. In this paper, we introduce a maximum self-interference threshold (SIT) constraint to the sum-rate maximization problem to transform the problem into a convex optimization problem and develop the SIT-based FD precoding (FDP-SIT) algorithm. In particular, the FDP-SIT algorithm consists of an inner loop that assumes fixed threshold values and an outer loop that optimizes each node's threshold values. Illustrative examples show how the proposed FDP-SIT algorithm can provide a tradeoff between the separate and joint FDP algorithms. As well, the measured data-based results suggest that the FDP-SIT algorithm can offer increased sum rates when low cancelation power is used.
In this letter a multiuser transmitter preprocessing (MUTP) approach is proposed for downlink wireless communications, such as in spatial-division multiple-access (SDMA) or direct-sequence code-division multiple-acces...
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In this letter a multiuser transmitter preprocessing (MUTP) approach is proposed for downlink wireless communications, such as in spatial-division multiple-access (SDMA) or direct-sequence code-division multiple-access (DS-CDMA) system. In the proposed MUTP the preprocessing matrix is obtained by constructing a subspace that is orthogonal to the interference subspace without relying on eigen-analysis. The proposed MUTP fully removes the downlink multiuser interference, resulting in the zero-forcing (ZF) solution. It is capable of achieving the same bit error rate (BER) performance as the conventional ZF-based MUTP (ZF-MUTP).
We study the optimal antenna configuration (i.e. number of transmit anti receive antennas) for multiple-input multiple-output systems in pilot-symbol-assisted modulation schemes with imperfect channel estimation. We a...
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We study the optimal antenna configuration (i.e. number of transmit anti receive antennas) for multiple-input multiple-output systems in pilot-symbol-assisted modulation schemes with imperfect channel estimation. We assume block flat-fading channels and focus on a practical range of high signal-to-noise ratio. An ergodic capacity lower bound is used as the objective function to be maximized. We analytically study the capacity gain from adding extra antennas to the transmitter or to the receiver in two different scenarios. Our numerical results show that the optimal antenna configuration under imperfect channel estimation can be significantly different from that under perfect channel estimation assumption. In addition, we investigate the capacity gain from optimizing antenna configuration and find that the gain can be larger than that achieved by optimizing transmit power over pilot and data symbols, particularly for large block lengths.
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