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Multiple-input multiple-output (MIMO) antennas are commonly evaluated by using the correlation coefficient. However, the correlation has several different definitions and calculation methods, and this misleads the real performance of the MIMO antennas. This paper describes five definitions and their differences of the correlation, i.e., signal corr...
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... that the channel correlation matrix cannot be used for the Kronecker model because this correlation considers only the instantaneous channel characteristics, which do not necessarily represent the statistical properties of the environment. Figure 6 shows the relationship among the measurable and computable quantities through the correlation characteristics. The complex pattern is quite useful information because this can yield various kinds of the physical quantities that are used in MIMO systems. ...
Citations
... Gain = 4π × radiation intensity Total radiated power (5) d. Envelope correlation coefficient (ECC) "ρe" illustrates the impact of the diverse transmission routes of the RF indicators in any MIMO antenna system [17]. The ECC is expressed in terms of S-parameters which is given by Eq. (6) [18], and the proposed MIMO ECC is 0.0001. ...
... Multiple input multiple output (MIMO) configurations are broadly applied to improve antenna performance, especially in terms of reliability, higher data rate, and diversity to reduce the risk of interference with other wireless devices. Instead of using wideband antennas, researchers put efforts into designing resonation at multiple bands of their own choice [1]. Along with that, more attention is put into developing a relatively small-sized antenna to meet the requirements of modern communication devices, such as cellular phones, smartwatches, portable devices, and other wearables. ...
This paper presents a compact two-element MIMO antenna with improved isolation for triple-band applications. The antenna consists of two radiating elements with the shared ground plane and a novel decoupling structure. Each antenna element has three stubs with different lengths, which work as quarter-wavelength monopoles to give a triple-band operation. The decoupling system is made by etching various slots in an inverted H-shape stub attached to two quarter-circles at its lower ends. The simulated and measured results show that the antenna operates (|S11| < −10 dB) at the key frequency bands of 2.4 GHz (2.29-2.47 GHz), 3.5 GHz (3.34-3.73 GHz), and 5.5 (4.57-6.75 GHz) GHz with a stable gain and radiation patterns. Moreover, the MIMO antenna shows good isolation characteristics. The isolation is more than 20 dB, the envelope correlation coefficient is <0.003, and diversity gain is 9.98 dB, within the frequency band of interest. Furthermore, the MIMO antenna has a compact size of 48 mm × 31 mm × 1.6 mm. These features of the proposed antenna make it a suitable candidate for I.S.M., 5G sub-6 GHz, and WLAN applications.
... Indeed, a distance in the order of magnitude of a wavelength is often considered as enough to prevent an adversary from learning the secret, although this assumption has been criticized [131]. For reference, the wavelength at a 2.4 GHz frequency is 12.5 cm; typically, a distance of a few decimeter is enough to achieve total spatial decorrelation between two channels [132]. There are different requirements to build a CBKE protocol. ...
Location services are foreseen as one of the major IoT features in the next years, and have gained a lot of interest over the last decade from the literature of Wireless Sensors Networks, (WSN) and Vehicular Ad Hoc Networks (VANet). Impulse-Radio Ultra-Wideband (UWB), standardized in IEEE 802.15.4-2003, is currently the most performant radio positioning technology with centimeter-level accuracy and is used widely in industrial applications. It has been proven in the literature that UWB positioning is not completely tamper-proof, as various physical and link layers vulnerabilities have been identified in 802.15.4. Most of the major attacks against IR-UWB are physical-level attacks, such as Early-Detection/Late-Commit (ED/LC). Considering their cost, complexity, and sometimes lack of maturity, they are not necessarily the most realistic attacks against cheap IoT systems. On the other hand, protocol-level flaws expose IR-UWB positioning against attacks that can be mounted with limited expertise and cheap hardware. Hence, the aim of this work is to identify the most critical vulnerabilities of 802.15.4 IR-UWB, evaluate real-world attacks against UWB IPS and propose low-cost countermeasures suitable for IoT applications. An open platform for IR-UWB positioning security evaluation, SecureLoc, is part of the contributions. We propose and evaluate various spoofed acknowledgment-based attack schemes against IR-UWB. Several countermeasures, at the physical, medium access control and system level, are proposed, including notably a novel weak PUF-based authentication protocol, a spoofing resilient acknowledgment scheme, a tamper-proof ranging approach, and a cooperative verification protocol for rogue node detection. All the proposed attacks and countermeasures have been implemented and evaluated on SecureLoc.
... At present, most researches on terahertz channels are about energy acquisition and information capacity analysis [23][24][25], while there are few studies on multiple inputs and multiple-output (MIMO) in the terahertz band. Because of this, this paper proposes a MIMO model suitable for the terahertz frequency band and analyzes the channel model with traversal capacity as a metric [26,27]. ...
... Since the influence of electronic and antenna noise in the present environment is very low [32][33][34][35], the main focus is on molecular absorption noise. It can be seen from [27] that the noise power spectral density W can be expressed as ...
With the development of wireless mobile communication technology, the demand for wireless communication rate and frequency increases year by year. Existing wireless mobile communication frequency tends to be saturated, which demands for new solutions. Terahertz (THz) communication has great potential for the future mobile communications (Beyond 5G), and is also an important technique for the high data rate transmission in spatial information network. THz communication has great application prospects in military-civilian integration and coordinated development. In China, important breakthroughs have been achieved for the key techniques of THz high data rate communications, which is practically keeping up with the most advanced technological level in the world. Therefore, further intensifying efforts on the development of THz communication have the strategic importance for China in leading the development of future wireless communication techniques and the standardization process of Beyond 5G. This paper analyzes the performance of the MIMO channel in the Terahertz (THz) band and a discrete mathematical method is used to propose a novel channel model. Then, a channel capacity model is proposed by the combination of path loss and molecular absorption in the THz band based on the CSI at the receiver. Simulation results show that the integration of MIMO in the THz band gives better data rate and channel capacity as compared with a single channel.
The growing demand for high data rate with high quality of service (QoS) is required for a re-design of current systems. The Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system can enhance performance of system toward high data rate requirements. However, the received signal can be corrupted due to selectivity of the channel. Error correction code (ECC) can overcome the drawback of channel affect. In addition, space time code (STC) that transmits replica of transmitted signal through different sub-channels can obtain the spatial diversity. As a result, it improved the system performance.
The combination of the aforementioned systems can be improved with the system outcome significantly. In this work, the actual MIMO system was implemented with two transmission,and a reception antennas. The receiver combined received signals using maximum ratio combiner (MRC) to increase a received signal to noise ratio (SNR). OFDM which divides channel into several sub-channels is employed with different number of sub-carriers. To increase the system throughput, several modulation formats are used with different constellation maps such as (BPSK, QPSK, 16QAM, and 64 QAM). To exploit the advantages of ECC regarding the cancelation of channel effect to the received signals. Several codes such as Conventional Code (CC), Low Density Parity Check (LDPC) code and Reed Solomon (RS) code were studied. LDPC performs better performance compared with other codes, therefore, LDPC is used with different code rate. It is seen from the simulation results, the MIMO-OFDM system combined with LDPC code and STC can perform better performance regarding bit error rate (BER) at the indicated SNR.
The MIMO-OFDM with LDPC and STC system obtain a gain about 5 dB in SNR at 10^-4 BER. Moreover, the gain in the spectral efficiency with sacrificing by SNR is achieved. The 8 bps/Hz was obtained.
A base station scanner that can evaluate MIMO antennas for LTE downlink signaling has been proposed. In this system, all signal processing is done offline, so analysis is significantly delayed. Further, only FDD-LTE is supported. This report details a coherent base station scanner that offers real-time demodulation of not only FDD but also TDD. Experiments on LTE signals using both duplex modes confirm that the developed scanner offers excellent performance and reduced post analysis times.
A novel optically transparent multiple-input multiple-output (MIMO) antenna for automotive applications is presented in this article. The MIMO antenna consists of a two-semicircular slot-loaded monopole with a staircase ground structure. It is developed on a glass substrate with dimension
$29\times50$
mm
<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>
. The fluorine-doped tin oxide and indium-doped tin oxide (ITO) are used as the conductive layers on the bottom and top of the substrate with sheet resistance
$4~\Omega $
/sq and
$10~\Omega $
/sq, respectively. The fabricated antenna has an optical transmittance greater than 72%; hence, it can be placed on the glass surface of the automotive. The measured results show that the proposed antenna exhibits a good impedance matching over a frequency of 2.4–11 GHz with isolation greater than 20 dB and a peak realized gain of 2 dBi, which is suitable for ultrawideband (UWB) automotive applications.
