In this paper, a two-port ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is designed, fabricated, and tested based on characteristic mode theory. The MIMO design consists of two circular patches wh...
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In this paper, a two-port ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is designed, fabricated, and tested based on characteristic mode theory. The MIMO design consists of two circular patches which are connected to the UWB unit with an I-shaped branch. Slots are opened in the circular patch to enhance the impedance matching performance, and in order to improve the isolation of the antenna while operating, metal strips are added to the patch, and a fence decoupling structure. The overall size of the proposed antenna is 77.5 x 39 x 1 mm(3), and the microstrip feed is used. Simulation results show that the antenna can cover the 2.68-11.85 GHz band with a return loss of -43.5 dB, an isolation of less than -20 dB, and an envelope correlation coefficient (ECC) of < 0.007. It possesses good directional radiation characteristics, and it can be used in 5G MIMO communication systems.
Cylindrical vector beam (CVB) provides an attractive prospect in enhancing the capacity density of optical communication via mode multiplexing. However, the mode coupling in few-mode fiber will disturb the mode power ...
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Cylindrical vector beam (CVB) provides an attractive prospect in enhancing the capacity density of optical communication via mode multiplexing. However, the mode coupling in few-mode fiber will disturb the mode power distribution of CVBs randomly, which causes crosstalk and signal fading, severely degrading the system performance and even interrupting communication. Here, we propose a diversity gain strategy to mitigate the crosstalk and signal fading in CVB multiplexing communication. By performing multi-input multi-output equalization on the receiving signals and estimating the channel matrix by solving the optimal mode channel weights, the diversity gain is performed to equalize the crosstalk-induced noise components and random signal errors, and the crosstalk and signal fading are mitigated. As a proof of concept, we experimentally demonstrate a multi-dimensional multiplexing communication (320 channels combined by 4 CVBs and 80 wavelengths), and 7.5 Tbit/s QPSK-OFDM signals are transmitted in 5 km few-mode fiber. We show that after diversity gain, the biterror-rate is improved by about 2-3 orders of magnitude, and the communication outage of 60 % is completely suppressed. These validate that the diversity gain effectively eliminates crosstalk and signal fading caused by mode coupling in CVB multiplexing transmission over few-mode fiber, which significantly enhances communication capacity while greatly improving the stability and reliability of the communication system. It provides an effective solution for future high-capacity and long-distance optical communication.
A new isolation technique is proposed for multiple-input multiple-output (MIMO) microstrip patch antenna (MPA) arrays utilizing mode diversity. Typically, similar modes are excited in each element of the MIMO array. H...
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A new isolation technique is proposed for multiple-input multiple-output (MIMO) microstrip patch antenna (MPA) arrays utilizing mode diversity. Typically, similar modes are excited in each element of the MIMO array. However, the proposed MIMO array uses two elements of different sizes excited in distinct modes at the same frequency. It is found that the TM01 mode excited in one MPA, a hybrid mode (TM 03+ TM21) is induced in the coupled MPA, while exciting the TM03 mode in another patch induces a quasi-TM11 mode in the coupled MPA. Both induced modes exhibit weak fields at the feeding points, reducing the mutual coupling between the two patch antennas without requiring extra decoupling structure. Additionally, the induced modes create a null in the broadside direction, reducing cross-polarization (x-pol) levels. An isolation level over 50 dB is achieved in 1x2 MIMO array at 5.8 GHz. The design is adaptable to larger array. Therefore, to validate the design technique, a 1x4 array is simulated, fabricated and measured, showing 30-45 dB isolation among the ports in the passband. Moreover, the design features an x-pol around -40 dB in broadside direction in both E- and H-planes, ensuring effective polarization diversity. The technique is applied to a MIMO dielectric resonator antenna (DRA) array, demonstrating excellent isolation and radiation pattern performance. Furthermore, the technique is versatile and can be applied to various MIMO configurations. Therefore, simulations have been performed for 2x4 MPA array, validating the effectiveness of isolation in both the E- and H-planes. This approach also optimizes space utilization, allowing for the inclusion of additional patch elements to form hybrid-coupled MIMO MPAs within confined spaces.
The performance of millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems has been significantly enhanced by the incorporation of dynamic reconfigurable intelligent surfaces (RIS). This paper proposes ...
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The performance of millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems has been significantly enhanced by the incorporation of dynamic reconfigurable intelligent surfaces (RIS). This paper proposes a novel dynamic channel estimation technique that combines dynamic atomic norm minimization with dynamic RIS to optimize RIS-aided mmWave MIMO systems. Leveraging the dynamic nature of both atomic norm minimization and RIS, the proposed approach efficiently adapts to changing environmental conditions, providing robust and accurate channel estimation. By dynamically optimizing the RIS configuration, the system achieves improved spectral and energy efficiency, enabling high-speed and reliable communication in challenging mmWave environments. Theoretical analysis and simulation results demonstrate the effectiveness of the proposed dynamic channel estimation technique, highlighting its potential for enhancing the performance of future wireless communication systems. It presents a breakthrough dynamic channel estimation method for millimeter-wave (mmWave) multiple-input multiple-output systems that combines dynamic atomic norm minimization with reconfigurable intelligent surfaces (RIS). By adapting to environmental changes, this method significantly improves the accuracy of channel estimation. Dynamic RIS optimization increases spectral and energy efficiency and ensures fast and reliable communication in challenging mmWave environments. The simulations confirm the effectiveness of this system and show that it has the potential to revolutionize the future performance of wireless communications. image
This paper presents a compact-sized six-port millimeter wave multiple-input multiple-output (MIMO) antenna for next generation wireless network applications. A rectangular patch loaded with a Sierpinski slot is design...
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This paper presents a compact-sized six-port millimeter wave multiple-input multiple-output (MIMO) antenna for next generation wireless network applications. A rectangular patch loaded with a Sierpinski slot is designed as a main radiator to resonate at 31 GHz in the millimeter wave spectrum on a hexagonal-shaped substrate. An Array-antenna Decoupling Surface (ADS) consisting of primary and secondary reflectors is embedded to improve the isolation in the MIMO system. The presented MIMO configuration has a footprint of 13.86 mm x 16 mm, designed on Rogers RT/Duroid 5880 substrate with a thickness of 0.508 mm. Despite its compactness, the proposed MIMO antenna provides an impressive isolation of about -35 dB between the adjacent ports and a satisfactory gain of 9.8 dB in the whole band of operation. A prototype of the design is fabricated and tested. The measured results show a -10 dB impedance bandwidth in the range of 30.2-31.8 GHz. The investigated diversity parameters resulted in an Envelope Correlation Coefficient (ECC) below 0.18, Channel Capacity Loss (CCL) less than 0.1 bits/s/Hz, and Group Delay within 1.2 ns. Based on these attributes, the suggested MIMO antenna may be well suited for compatibility with millimeter-wave high-capacity wireless networks.
Integrated sensing and communication (ISAC) has become a promising technology in current sixth-generation (6G) wireless communications due to its ability to support both communication and sensing. Existing works regar...
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Integrated sensing and communication (ISAC) has become a promising technology in current sixth-generation (6G) wireless communications due to its ability to support both communication and sensing. Existing works regarding ISAC channels mainly focus on far-field propagation conditions based on plane wave assumption. However, with the deployment of ultra-massive multiple-in multiple-out (MIMO), the far-field assumption may no longer hold, as the communication and sensing propagation distances can become comparable to the antenna size. To address this issue, we propose a three-dimensional MIMO channel model that captures the characteristics of communication and sensing channels in ISAC environments, considering near-field propagation conditions. Additionally, we distinguish the communication and sensing propagation environments by employing different effective scatterer distributions. In the model, the sensing channel is divided into target sensing and environmental sensing components, whereas the communication channel is divided into line-of-sight and non-line-of-sight components. The weighted sum of each component in communication and sensing channels results in accurate channel representations. Based on the proposed model, we derive and thoroughly investigate space-time-frequency correlation function, normalized absolute error function, and channel capacity. A key observation is that the correlation between communication and sensing channels is high in dense scatterer environments, which implies that the communication channel can be recovered from the sensing channel. Error function results indicate that the proposed channel model achieves fairly high accuracy in ultra-massive MIMO scenarios. These findings provide essential support for the development of ISAC systems in future 6G wireless communications.
Maximum-likelihood multiuser detection incurs a large computational complexity, and its low-complexity detection scheme suffers from a performance loss, where this tradeoff is inevitable and inherent in a classical co...
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Maximum-likelihood multiuser detection incurs a large computational complexity, and its low-complexity detection scheme suffers from a performance loss, where this tradeoff is inevitable and inherent in a classical computer. In this paper, we use the Grover adaptive search (GAS) to break the tradeoff, which is a quantum exhaustive search algorithm guaranteed to obtain the optimal solution, achieving a quadratic speedup. Specifically, we design two specific parameters of GAS to achieve the optimal performance with a reduced complexity: the initial threshold and the number of Grover rotations. The initial threshold of GAS can be optimized using a solution of semi-definite programming, and it is possible to calculate the distribution of the number of solutions smaller than the initial threshold in advance, which depends on instantaneous channel coefficients. In addition, we analyze the number of quantum gates required for GAS and show that the gate count can be reduced by bypassing the higher-order terms in the objective function, leading to a reduced circuit runtime. Our analysis and simulation results demonstrate that the proposed approach achieves the same performance as the optimal maximum-likelihood detection while reducing the query complexity of GAS, implying that the large constant overhead of quadratic speedup can be further reduced.
A low-profile, compact and efficient antenna is especially desirable for wireless applications, as it can reduce the size and weight of the system and improve its performance. In recent years, flower-shaped antennas h...
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A low-profile, compact and efficient antenna is especially desirable for wireless applications, as it can reduce the size and weight of the system and improve its performance. In recent years, flower-shaped antennas have gained popularity due to their low profile, broad bandwidth and good radiation characteristics. In this work, a high-isolated dual-element UWB-MIMO antenna is experimentally verified having size of 32 x 39 x 0.8 mm3. The main radiating element of MIMO setup comprises a Half-Cut Flower-Shaped (HCFS) resonator. A tree-shaped decoupling structure is use to enhance the isolation. The simulated operating band of the proposed 2-port UWB-MIMO antenna ranges from 2.3 to 2.68 GHz and 3.15 to 12.87 GHz which covers Bluetooth, Wi-Fi/WLAN, Wi-MAX and UWB) with inter-element isolation of more than 15 dB and 20 dB, respectively. The measured results are found in close agreement with simulated ones. Furthermore, the diversity parameters such as Envelope Correlation Coefficient (ECC), Channel Capacity Loss (CCL), Mean Effective Gain (MEG), Effective Diversity Gain (EDG) and Total Active Reflection Coefficient (TARC) have also been analysed to ensure its legitimacy for wireless applications. Moreover, the simulation S-parameters characteristic of the proposed 8-element antenna for wireless access point applications has also been showcased.
Energy harvesting (EH)-assisted non-orthogonal multiple access (NOMA) cognitive radio (CR) networks allow simultaneous transmission of multiple secondary user signals on primary frequency bands with harvested energy, ...
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Energy harvesting (EH)-assisted non-orthogonal multiple access (NOMA) cognitive radio (CR) networks allow simultaneous transmission of multiple secondary user signals on primary frequency bands with harvested energy, enhancing spectral, spectrum utilization, and energy efficiencies. Although multiple antennas are used for efficient energy transfer and signal transceiving, multiple-input multiple-output (MIMO) communication in these networks is facing reliability/security performance degradation due to nonlinear EH, hardware impairment (HWi), and wire-tapping. The paper aims to numerically evaluate the security and reliability of MIMO communication in EH-assisted NOMA CR networks with jamming (MehNOwJ) under such effects. The results indicate that MehNOwJ prevents full outage and achieves optimum performance with proper parameter selection of preset spectral efficiency, power saturation threshold, EH duration, number of antennas of jammer. In addition, the performance improves with an accreting quantity of antennas but experiences saturation. Moreover, MehNOwJ drastically outperforms alternative approaches (MIMO communication in EH-assisted orthogonal multiple access CR network with jamming and MIMO communication in EH-assisted NOMA CR network without jamming), offering insights into the benefits of combining NOMA and jamming techniques.
Future smart reconfigurable antennas (RAs) (Haupt R-L and Lanagan M (2013) Reconfigurable antennas. IEEE Antennas and Propagation Magazine 55, 49-61) will likely be fully multipurpose and controlled by software and eq...
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Future smart reconfigurable antennas (RAs) (Haupt R-L and Lanagan M (2013) Reconfigurable antennas. IEEE Antennas and Propagation Magazine 55, 49-61) will likely be fully multipurpose and controlled by software and equipped with machine learning skills that can discern and respond to alterations in the radio frequency environment. Cognitive radio utilizations will be accomplished using a new generation of antenna technology and communication protocols. The effective use of frequencies and the use of polarization diversity and radiation pattern reconfigurability to send data over existing congested frequencies will be major advantages for such applications. The usage of antennas that can be reconfigured in multiple-input multiple-output (MIMO) channels will enhance channel capacity while simultaneously improving channel efficiency and lowering costs (Christodoulou C-G, Tawk Y, Lane S-A and Erwin S-R (2012) Reconfigurable antennas for wireless and space applications. Proceedings of the IEEE 100, 2250-2261). There are a lot of antennas used both at the transmitter and at the receiver front end in a MIMO system. The benefit of employing such arrangements is that different types of information can be conveyed at a similar time, boosting the spectral efficiency of communication in a multipath situation. The coding rate, modulation level, and transmission signaling method of a MIMO system can all be changed in response to changing channel circumstances and user needs. In a MIMO context, polarization reconfigurable/frequency-reconfigurable/radiation pattern RA increase the degree of freedom and enhancing the system's performance. The usage of such antennas greatly enhances capacity by enabling a choice of various polarization configurations and pattern diversity. Antenna arrays that can be reconfigured are also an appealing MIMO system solution that needs to retain robust communication channels, particularly in portable gadgets where the area is limited.
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