1,179 research outputs found
Reconfigurable Intelligent Surface Aided TeraHertz Communications Under Misalignment and Hardware Impairments
TeraHertz (THz) communications are envisioned to help satisfy the ever high
data rates demand with massive bandwidth in the future wireless communication
systems. However, severe path attenuation, transceiver antenna misalignment,
and hardware imperfection greatly alleviate the performance of THz
communications. To solve this challenge, we utilize the recently proposed
reconfigurable intelligent surface (RIS) technology and provide a comprehensive
analytical framework of RIS-aided THz communications. More specifically, we
first prove that the small-scale amplitude fading of THz signals can be exactly
modeled by the fluctuating two-ray distribution based on recent measurements.
Exact statistical characterizations of end-to-end signal-to-noise plus
distortion ratio (SNDR) and signal-to-noise ratio (SNR) are derived. Moreover,
we propose a novel method of optimizing the phase-shifts at the RIS elements
under discrete phase constraints. Finally, we derive analytical expressions for
the outage probability and ergodic capacity, respectively. The tight upper
bounds of ergodic capacity for both ideal and non-ideal radio frequency chains
are obtained. We provided Monte-Carlo simulations to validate the accuracy of
our results. It is interesting to find that the impact of path loss is more
pronounced compared to others, and increasing the number of elements at the RIS
can significantly improve the THz communication system performance
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Performance Analysis of mmWave Communications with Selection Combining over Fluctuating-Two Ray Fading Model
Performance of Integrated IoT Network with Hybrid mmWave/FSO/THz Backhaul Link
Establishing end-to-end connectivity of Internet of Things (IoT) network with
the core for collecting sensing data from remote and hard-to-reach terrains is
a challenging task. In this article, we analyze the performance of an IoT
network integrated with wireless backhaul link for data collection. We propose
a solution that involves a self-configuring protocol for aggregate node (AN)
selection in an IoT network, which sends the data packet to an unmanned aerial
vehicle (UAV) over radio frequency (RF) channels. We adopt a novel hybrid
transmission technique for wireless backhaul employing opportunistic selections
combining (OSC) and maximal ratio combining (MRC) that simultaneously transmits
the data packet on mmWave (mW), free space optical (FSO), and terahertz (THz)
technologies to take advantage of their complementary characteristics. We
employ the decode-and-forward (DF) protocol to integrate the IoT and backhaul
links and provide physical layer performance assessment using outage
probability and average bit-error-rate (BER) under diverse channel conditions.
We also develop simplified expressions to gain a better understanding of the
system's performance at high signal-to-noise ratio (SNR). We provide computer
simulations to compare different wireless backhaul technologies under various
channel and SNR scenarios and demonstrate the performance of the data
collection using the integrated link.Comment: This work has been submitted to IEEE for possible publicatio
Ratio of Products of Mixture Gamma Variates with Applications to Wireless Communications Systems
The fading scenario of many realistic wireless communication transmission systems, such as, multi-hop communications and spectrum sharing in cognitive radio networks (CRNs), can be modelled by the product and the ratio of the product of the random variables (RVs) of the channel distribution. However, there is no work has been investigated in the literature to provide unified statistics of the product and the ratio of the products that can be used for a wide range of non-composite and composite fading conditions. Accordingly, in this paper, the statistical properties, namely, probability density function (PDF), cumulative distribution function (CDF), and moment generating function (MGF) of the product and the ratio of the product of independent and non-identically distributed (i.n.d.) mixture Gamma (MG) RVs are derived. A MG distribution has been widely employed to approximate with high accuracy most of the conventional fading models, for example, Rayleigh, Nakagami-m, Nakagami-q (Hoyt), and Nakagami-n (Rician) as well as the generalised composite fading channels, such as, generalised- (),− /gamma, − /gamma, and − /gamma. Hence, the derived PDF, CDF, and MGF are utilized for the Beaulieu–Xie and −−− shadowed fading channels that have not been yet presented by the previous works due to mathematical intractability of their statistics. Thus, the equivalent parameters of a MG distribution for these channels are given. To this end, simple closed-form mathematically tractable expressions of the performance metrics are obtained. The derived statistics are applied to analyse the outage probability (OP), the average error probability for different modulation schemes, the effective rate (ER) of wireless communication systems and the average area under the receiver operating characteristics (AUC) curve of energy detection over cascaded fading channels. Moreover, the OP of the multi-hop communications systems with co-channel interference (CCI), both the lower bound of secure OP (SOPL) and probability of non-zero secrecy capacity (PNSC) of the physical layer security (PLS), and the outage and delay-limited capacities of CRNs are studied via using the statistics of the ratio of the product of MG variates. A comparison between the numerical results and the Monte Carlo simulations is presented to verify the validation of our analysis
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