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Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper envisages a technique for enhancing the privacy of multi-antenna wireless networks using Artificial Noise (AN). The artificial noise is a form of interference that is designed to degrade the channel quality of eavesdroppers, thereby making it unfeasible for them to capture and decode the transmitted data. The proposed method uses Non-Orthogonal Multiple Access (NOMA). It allows multiple users to share a resource block like a time slot or frequency. This increases the spectral efficiency. The paper evaluates the effectiveness of Artificial Noise (AN) in improving the privacy of the system by measuring the Bit Error Rate (BER) and the eavesdropper's secrecy rate. Simulations show the method significantly enhances the security of the system. The paper also investigates the impact of various system parameters, such as the number of antennas and power allocation coefficients, on the system performance. Overall, the proposed method provides a promising approach to enhancing the security of multi-antenna wireless networks. [ABSTRACT FROM AUTHOR]

This paper presents a compact three-port antenna design suitable for use in mobile radio systems that require polarization and pattern diversity. The antenna design utilizes a shorted bow-tie patch split in half with an air gap and a top-loaded two-element monopole placed along the gap on a small common ground plane ( $0.37\lambda ^{2}$ ) to achieve a compact form factor. The patch is excited by aperture coupling and probe feeding via two independent ports, producing two orthogonally polarized broadside patterns for polarization diversity. Meanwhile, the co-located monopole generates a vertically polarized omnidirectional pattern to provide pattern diversity. High inter-port isolation (> 25 dB) is achieved by incorporating simple decoupling structures shorted to the ground plane between the patch and the monopole. Measurements on the antenna prototype show that envelope correlation coefficients among the three different radiation patterns are lower than – 37 dB (or 0.0002) within the operating bandwidth, making this antenna a good candidate for diversity applications.

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Interference has been a key roadblock against the effectively deployment of applications for end-users in wireless networks including fifth-generation (5G) and beyond fifth-generation (B5G) networks. Protocols and standards for various communication types have been established and utilised by the community in the last few years. However, interference remains a key challenge, preventing end-users from receiving the quality of service (QoS) expected for many 5G applications. The increased need for better data rates and more exposure to multimedia information lead to a non-orthogonal multiple access (NOMA) scheme that aims to enhance spectral efficiency and link additional applications employing successive interference cancellation and superposition coding mechanisms. Recent work suggests that the NOMA scheme performs better when combined with suitable wireless technologies specifically by incorporating antenna diversity including massive multiple-input multiple-output architecture, data rate fairness, energy efficiency, cooperative relaying, beamforming and equalization, network coding, and space–time coding. In this paper, we discuss several cooperative NOMA systems operating under the decode-and-forward and amplify-and-forward protocols. The paper provides an overview of power-domain NOMA-based cooperative communication, and also provides an outlook of future research directions of this area. [ABSTRACT FROM AUTHOR]

Improving safety is of general interest in aviation. Flight transponders used in collision avoidance systems advise pilots with information of potential collisions and avoidance resolutions. Some transponders are capable of transmitting the instantaneous position of the vehicle which might be turned off. To prevent autonomous flights from collisions, the transponder signals shall be used to estimate the direction-of-arrival (DoA). Recently, multimode antennas have been investigated for communication and localization purposes. Multimode antennas provide several orthogonal ports on a single radiator surface. This leads to a reduction of space and weight, which is of interest in airborne applications. To perform DoA estimation as well as communication, a suitable channel model is required. In this contribution, a channel model fulfilling the requirements for both multiple-input multiple-output (MIMO) communication and DoA estimation is proposed. This channel model relies on the manifold matrix representation of the UAV under consideration. The derived description of a manifold matrix for the UAV use-case is used for an optimization to achieve a close to omnidirectional radiation pattern. Therefore, different optimization functions are derived and their performance is compared. The results of the optimization using the calculated manifold matrix are verified by measurements taken in an antenna measurement chamber. [ABSTRACT FROM AUTHOR]

This article proposes a scalable dual-polarized antenna using the compact cavity and slot-dipole hybrid structure for omnidirectional radiation. For the horizontal polarization, an open-ended cavity is uniformly excited at its TE1/2,0,0 mode to achieve omnidirectional coverage. Based on this thin cavity, a hybrid structure with slots and parasitic dipole stub pairs is designed for vertical polarization, providing an omnidirectional pattern in the azimuthal plane. The measured results show that dual-polarized radiations with port isolation higher than 25 dB and gain variations lower than 2.7 dB are achieved in the band of 2.39–2.49 GHz, covering the frequency band of wireless local area network (WLAN) system. Moreover, to validate the scalability of the proposed antenna, a cascaded array is contrived to realize high-gain omnidirectional radiation. Compared with the existing works, the proposed omnidirectional dual-polarized antenna has the advantages of both compact volume and array scalability, exhibiting promising usage for high-gain router applications. [ABSTRACT FROM AUTHOR]

In this communication, a novel dual-polarized (DP) epsilon-near-zero (ENZ) antenna is proposed with its operating frequencies independent of lengths for both polarizations. To obtain a DP implementation of ENZ antenna, an antiphase ENZ (AP-ENZ) mode is used based on a slot-fed substrate-integrated waveguide (SIW) antenna at its cutoff frequency, in which the electric field presents a sign-function-like distribution, presenting a fixed operating frequency independent on length. The proposed DP length-irrelevant antenna design is composed of a cross-shaped SIW operating on two orthogonal AP-ENZ modes, which are excited by a cavity-backed cross-shaped slot with good port isolation. The SIW lengths for both polarizations can be tuned independently without disturbing the operation frequency with controllable radiation patterns. To be specific, we study two cases of different lengths where sidelobe elimination and high gain radiation are realized, respectively. To verify this design, two antenna prototypes Ant. 1 and Ant. 2 are fabricated and tested, exhibiting agreements between simulation and experiment. The proposed Ant. 1 presents no sidelobes at 2.42 GHz while Ant. 2 shows a high gain of 10.56 dBi from 2.45 to 2.55 GHz. The proposed design method enables antennas with a variety of radiation patterns to be designed at a fixed frequency and both symmetric and asymmetric patterns for DP antennas. It also inspires the design of a flexible antenna with unchanged operating frequency when folded in both dimensions. [ABSTRACT FROM AUTHOR]

A systematic procedure for constructing orthogonal antenna ports on arbitrary symmetric multimode antennas is proposed. The procedure is based on the projection operator method from group theory. With this method, optimal orthogonal port configurations are generated analytically. Electromagnetic simulations, modal analyses, or optimization techniques are not required. The optimal port configurations are solely governed by the symmetry of an antenna and can thus be considered as a priori knowledge. Accordingly, this knowledge is available right from the beginning of the design process and can be purposefully used to compare different suitable antenna geometries with respect to the practical implementation effort. The procedure is illustrated by means of an application example resulting in a complete prototype of a six-port multimode antenna. [ABSTRACT FROM AUTHOR]

Background: Wireless power transfer is important for energizing and recharging the Internet-of-Things (IoT) cordlessly. Harnessing energy effectively from radio waves has become a crucial task. It is known that diversities at the transmitting antenna and waves (i.e. simultaneous continuous waves with center frequencies separated apart) can enhance the radio frequency (RF) to direct current (DC) energy conversion. What remains unknown is the extent of which the wave diversity enhances the conversion gain. This study attempts to examine the RF-to-DC conversion gain of applying wave diversity. This paper investigates the effects of wave diversity on the energy conversion efficiency, and contributes the analytical expression that relate the conversion efficiency to the diversity count, i.e. the number of simultaneously transmitted sinewaves. Methods: We adopted a theoretical approach to the problem. First, we derived and presented a theoretical model that incorporated different forms of transmit diversity, i.e. antenna and wave diversities. This model then connected a RF-to-DC energy conversion model resulting from polynomial fitting on circuit simulation results. With the availability of these two models, we determined the theoretical energy conversion gain of simultaneously transmitting multiple sinewaves. Results: The results showed that transmitting multiple sinewaves simultaneously yields diversity gain and higher energy conversion efficiency. Most importantly, the gain and conversion efficiency can now be theoretically quantified. For example, at certain RF power measured at the receiver circuit, the diversity gain of transmitting four sinewaves is 2.6 (as compared to transmitting single sinewave). In fact, both the diversity gain and conversion efficiency increased with the number of simultaneously transmitted sinewaves. In another example, the conversion efficiency of transmitting four sinewaves is 0.1 as compared to 0.075 of two sinewaves. Conclusions: In summary, this paper presents a novel analytical expression for wave diversity in the context of wireless power transfer.

Interference has been a key roadblock against the effectively deployment of applications for end-users in wireless networks including fifth-generation (5G) and beyond fifth-generation (B5G) networks. Protocols and standards for various communication types have been established and utilised by the community in the last few years. However, interference remains a key challenge, preventing end-users from receiving the quality of service (QoS) expected for many 5G applications. The increased need for better data rates and more exposure to multimedia information lead to a non-orthogonal multiple access (NOMA) scheme that aims to enhance spectral efficiency and link additional applications employing successive interference cancellation and superposition coding mechanisms. Recent work suggests that the NOMA scheme performs better when combined with suitable wireless technologies specifically by incorporating antenna diversity including massive multiple-input multiple-output architecture, data rate fairness, energy efficiency, cooperative relaying, beamforming and equalization, network coding, and space–time coding. In this paper, we discuss several cooperative NOMA systems operating under the decode-and-forward and amplify-and-forward protocols. The paper provides an overview of power-domain NOMA-based cooperative communication, and also provides an outlook of future research directions of this area.

This article presents a dual-band and dual-polarized microstrip antenna array with broadside beam scanning ability for millimeter-wave applications. Within a compact multilayer structure, wide bandwidth and high port isolation are achieved by using double-layer gridded patches with three groups of metallic via-fences. For beam scanning purpose, a prototype of $2 \times 2$ array is designed, fabricated, and tested. The experimental results agree well with the simulations. For both orthogonal polarizations, the −10 dB bandwidth covers 23.3–31.7 and 42.5–46.5 GHz with average gains of 12 and 13.1 dBi, respectively. A 3 dB beam scanning angle from −51° to 43° at 27 GHz and −28° to 30° at 45 GHz is obtained. The proposed array provides dual-band and wideband properties for dual orthogonal polarizations with competitive beam steering range and compact dimensions, as a feasible solution for fifth-generation (5G) millimeter-wave mobile communications. [ABSTRACT FROM AUTHOR]

In this article, an omnidirectional dual-polarized antenna with low windage is presented within a wedge-profiled structure for supersonic onboard systems. Based on aerodynamic analysis, a wedge-profiled cavity is designed with colocated slots for omnidirectional and dual-polarized radiation. For horizontal polarization, two identical half-wavelength slots are etched onto the cavity sidewalls symmetrically. The vertical polarization is achieved by another horizontal slot, with the port isolation higher than 42 dB. A low windage coefficient of 0.11 is obtained within the wedge-profiled cavity with the dimensions of $41.6 \times 16 \times 30$ mm3 ($0.34\lambda _{0} \times 0.13\lambda _{0} \times 0.24\lambda _{0}$). The proposed antenna is constructed and tested, with the measured results in agreement with the simulated ones. The operating bandwidths cover the band of 2.40–2.48 GHz, and the gain variations below 3.5 dB are realized in the azimuthal plane for both polarizations. The proposed wedgy antenna is with both electromagnetic and aerodynamic considerations, exhibiting the potentials in supersonic onboard communication systems. [ABSTRACT FROM AUTHOR]

Frequent packet loss and power inadequacy are the major issues in wireless fading networks owing to the deep fading effects and inefficient resource utilization caused by unoriented information forwarding mechanisms. Diversity techniques are potentially employed in wireless communication systems to combat the impact of fading and reinforce the desired service level guarantees for data transmission. In this work, we employ spatial diversity and antenna beamforming methods to significantly improve the signal quality performance of wireless networks and enhance the reliability by decreasing the bit error probability. A constrained optimization problem is formulated for alleviating the net noise power integrated with the adaptive beamforming vector and ameliorated channel state information. For this, the evolutionary genetic algorithm scheme is iteratively implemented for evaluating the optimal solution of the proposed optimization problem. The influence of various selection functions in the application of genetic algorithm is investigated for effective heuristic modeling design and searching through the feasible solution space. Through extensive simulation results, several crucial network parameters characterizing the proficiency of wireless communications including the noise power, signal-to-noise ratio (SNR), bit error rate (BER) are estimated and analyzed for varying number of antennas deployed at the receiver node. Furthermore, the performance of the proposed genetic algorithm based optimization technique is compared with the existing models using the key channel quality metrics of achievable SNR, BER, and model computational complexity.

In this article, a wideband and highly-integrated quad-element multiple-input multiple-output (MIMO) antenna is proposed for the first time, to adapt to the size-limited environment in fifth-generation (5G) smartphones. First, the wideband decoupling between two extremely closely-spaced open-slot antennas with face-to-face and back-to-back configurations are investigated. Then, based on the complementary antenna pairs, wideband integrated quad-element MIMO antennas are implemented by the ingenious combination of these antenna pairs. For validation, an 8 × 8 MIMO system, constituted by two sets of integrated quad-antenna configurations, is simulated, fabricated, and measured. Both the simulated and measured results show that the 8 × 8 MIMO system can provide isolation of better than 10 dB between any two ports and a total antenna efficiency of 52.8%–70.8%/40.5%–75.0% across 3.3–5.0 GHz. Compared with the existing integrated quad-antenna design schemes, the proposed solution can expand the bandwidth from less than 200 to 1700 MHz, covering the entire 5G N77, N78, and N79 bands. In addition to the integrated quad-antenna design, further extension to integrated multiantenna configurations is also discussed by the flexible combination of complementary antenna pairs, which paves the way for future higher-order MIMO system in smartphones. [ABSTRACT FROM AUTHOR]

Ambient radiofrequency (RF) energy scavenging has been recently addressed with a wide range of studies to provide alternative powering for low-power applications. However, due to the low power level of the ambient electromagnetic field, the efficiency of the latter systems is still below expectations. Multipath in the environment may be considered and antenna diversity is then a solution for quasi-omnidirectional RF reception to reach a higher probability of receiving energy in a realistic situation. A 3D flexible antenna diversity, which can be integrated into the rectangular packaging, is proposed in order to take advantage of system packaging form. The angle and polarization diversity antenna was designed on flexible substrate in order to achieve the flexibility and low-cost. This design overcomes the low performance of the substrate while maintaining a compact, high isolation, and good radiation efficiency of the antenna. An indoor experimental setup was carried out to compare different rectenna configurations. The measurement results validate the principle and demonstrate the performance of the 3D flexible diversity system. The probability measurements were carried out under precise conditions in indoor scenarios and the results in comparison with statistic models confirmed the performance of the system in such low power conditions.

A wide-band multiple-input multiple-output (MIMO) antenna with dual-band (2.4 and 5 GHz) operation is proposed for premium indoor access points (IAPs). Typically, an omni-directional pattern is used for dipole antennas and a directional radiation pattern is used for patch antennas. In this paper, both antenna types were used to compare their performance with that of the proposed 2 × 2 MIMO antenna. We simulated and measured the performance of the MIMO antenna, including the isolation, envelope correlation coefficient (ECC), mean effective gain (MEG) for the IAPs, and the throughput, in order to determine its communication quality. The performance of the antennas was analyzed according to the ECC and MEG. The proposed antenna has sufficient performance and excellent characteristics, making it suitable for IAPs. We analyzed the communication performance of wireless networks using the throughput data of a typical office environment. The network throughput of an 802.11n device was used for the comparison and was conducted according to the antenna type. The results showed that the values of the ECC, MEG, and the throughput have unique characteristics in terms of their directivity, antenna gains, isolation, etc. This paper also discusses the communication performance of various aspects of MIMO in multipath situations.

In this article, an endfire dual-polarized phased antenna array with small ground clearance is proposed for the fifth-generation (5G) millimeter-wave (mmW) applications with a wide bandwidth. In this array, each antenna element consists of a dipole fed by a microstrip line for horizontal polarization and an H-plane horn using substrate-integrated waveguide (SIW) for vertical polarization. To achieve a wide bandwidth for vertical polarization, two metal vias are added at the aperture of the horn antenna. Then, a four-element antenna array is designed by partially overlapping the aperture of each horn element. A prototype has been fabricated using multilayer printed circuit board (PCB) process. The measured results agree well with the simulated ones. The antenna is with an impedance bandwidth of $\vert \text{S}_{11}\vert < -10$ dB from 24.4 to 29.5 GHz for both polarizations. The maximum gains of vertical and horizontal polarizations are 9.16 and 9.27 dBi, with the scanning angle from −34° to 33° for both polarizations with gain deterioration less than 3 dB. The proposed antenna is a promising solution for 5G mmW cellphones or antenna-in-package applications. [ABSTRACT FROM AUTHOR]

Abstract An un-coded multi-transmitter query scheme is introduced for wireless backscatter communication systems in which M transmitters and N receivers are used for single-tag connectivity (M × 1 × N). The main idea is to harden the wireless communication channel with a tag device for high data rate readings. The proposed method is designed for multipath fading channels in which the backscatter channel is a multiplicative Rayleigh. A coherent transmit query scheme is used to increase the tag-reflected signals and simultaneously alter the fading statistics in the forward path by implementing a receiver feedback. Full-diversity performance and array gain is achieved using the receiver diversity without requiring any tag antenna diversity. Therefore, the tag device remains simple. Mathematical expressions for the probability density function (PDF) of the backscatter channel are presented using closed-form equations. Bit error rate (BER) simulations for the binary phase shift keying (BPSK) modulation are computed numerically. Diversity gain of 10 dB is obtained by using a 2 × 1 × 1 scheme. The results show that the transmit diversity for single-tag usage performs the same as the tag antenna diversity, at the expense of a moderate transmitter complexity. The tag device remains intact as a requirement for the simplicity and size constraints. Also, the system realization becomes more feasible due to the available space on the transmitter side to accomplish the uncorrelated forward channel conditions. The feasibility study is demonstrated using software-defined radio (SDR) implementations.

In this letter, a multiple-beam antenna (MBA) scheme with reduced port dimension is proposed for low-complex massive multiple-input–multiple-output (MIMO) systems. From practical scenario consideration, two 2-port and 8-element subarrays with dual 2-to-8 Butler matrix networks are designed for 3 dB beam coverage within 60° sector. Based on channel capacity analysis of an 8-subarray (8 × 8-element) antenna system, it is proved that only 25% number of radio frequency (RF) chains are utilized in the proposed scheme to achieve a competitive data transmission rate, compared with a regular 8 × 8-element and 64-chain massive MIMO system, with the advantages of low cost, low system weight, and low complexity of signal processing. The proposed 8-subarray system is built and measured to verify the antenna performance. The proposed multibeam antenna scheme exhibits potential possibilities in low-complex and low-cost massive MIMO systems for the fifth-generation (5G) applications. [ABSTRACT FROM AUTHOR]

In this letter, we propose techniques for joint transmit and receive beamforming in downlink multi-user MIMO systems under Rayleigh fading channels using knowledge of the second-order statistics. The contribution of our work is twofold. First, we derive a closed-form expression for the outage probability for a general channel model using a recent covariance shaping method and for the conventional Kronecker structured model. Second, we present an outage minimization technique obtained by designing the transmit and receive beamformers. The transmit beamformers maximize the statistics of the signal-to-leakage-plus-noise ratio, while the receive beamformers minimize the cross-covariance of all users. Our techniques are “blind” in the sense that they do not require the transmission of pilot symbols, nor the estimation of the instantaneous state of the channel, making them bandwidth efficient. The derived theoretical results are validated via Monte Carlo simulations and show significant reduction in the outage probability by employing the proposed statistical beamforming techniques. [ABSTRACT FROM AUTHOR]

Industrial WSNs are gradually gaining space in industry due to low cost of installation and maintenance. However, RF communications systems are prone to several propagation phenomena which can compromise reliability in terms of missed message deadlines. This work aims to increase the robustness of industrial WSN. In order to achieve this goal, it is necessary to correct inherent problems in wireless communications, some of which are channel noise, interference, and multipath fading. Multipath can be considered the main factor that makes communications in wireless sensor networks a real challenge when compared to other types of mediums, such as optical fiber, cable, or even directional radio transmissions. In this sense, antenna diversity is proposed as a solution to deal with these effects, with the aim of improving radio reliability to make the use of dense industrial WSN feasible. The potential of antenna diversity in WSN is not fully exploited in industrial applications. This article presents the combination of selection technique for industrial WSN through an algorithm that selects the transceiver port that has the highest link quality indicator and performs antenna switching in the radio modules. The results obtained are analyzed to verify the diversity gain by using antenna spatial diversity at reception and thus reduce packet error rate. The results corroborate with theory by increasing radio reliability in terms of diversity gain, quadrupling the received signal power when the correct antenna is chosen. [ABSTRACT FROM AUTHOR]

A dual-polarized microstrip antenna loaded with capacitive via fence is proposed for compact size, wide beamwidth, and high isolation. By exploring a capacitive blind-via fence near the radiating apertures, the field is concentrated between the fence and ground, achieving obvious dimension miniaturization and wide beamwidth for regular dual-polarized microstrip antennas. The proposed blind-via fence is constituted by four rows of metallic wires with subwavelength diameter, period, and gap to the ground. Thanks to the field concentration brought by the blind-via fence, high isolation is realized by suppressing the radiation from the feeding probes, similar to two disk-loaded monopole antennas, and forcing the fundamental mode of the patch. To validate the proposed concept, a prototype is fabricated and characterized with the size of 0.19 $\lambda _{0} \times 0.19\,\,\lambda _{0} \times 0.07 \lambda _{0}$ ($\lambda _{0}$ is the free-space wavelength at the center frequency). The simulated and measured results agree well, with wide half-power beamwidth of 107° and 105° in the E- and H-planes, respectively. Meanwhile, the port isolation is higher than 32 dB within the operating bandwidth of 2.48–2.56 GHz. The proposed antenna is with the merits of compact size, wide beamwidth, and high isolation, exhibiting potential usage in diversity or multiple-input and multiple-output (MIMO) systems with wide-coverage applications. [ABSTRACT FROM AUTHOR]

In this article, we present a low-power, small form-factor, 60-GHz packaged radio featuring broad beam coverage. We increase angular coverage by beam switching between two orthogonally pointed low directivity beams that are created using two different antennas integrated in package. The resulting wide angular coverage of the radio makes radio links robust to movement and rotation; this improvement overcomes a key challenge for millimeter-wave (mmWave) deployment in portable electronics. We incorporate a 3.2 mm $\times $ 3.2 mm 32-nm CMOS radio integrated circuit (IC) in the package for radio functions. The IC includes TX and RX RF front ends, up- and down-conversion mixers, TX and RX analog baseband circuits, a common PLL, TX and RX LO chains, and ADCs and a micro-controller for built-in self-test (BIST). The IC is flip-chip packaged on a four-layer organic package comprising two TX antennas and two RX antennas. In board-level over-the-air measurements of the half-duplex packaged radio, 17.1-dBm effective isotropic radiated power (EIRP) and 6.1-dB noise figure are achieved in the TX and RX modes respectively, with power consumption below 250 mW in either mode. We characterized the radio over the air using 802.11ad waveforms; the radio is 802.11ad compliant in both TX and RX modes at data rates up to the maximum 802.11ad PHY rate of 4.62 Gb/s (raw data rate >7 Gb/s) with a TX EVM < −22 dB and RX sensitivity < −54 dBm. To measure angular coverage, we characterized 802.11ad compliance in 3-D over 3 $\pi $ steradians in first-of-a-kind measurements. The radio maintains 802.11ad compliance over 2.9 $\pi $ steradians solid angle. [ABSTRACT FROM AUTHOR]

This article presents a wideband orthogonal-mode dual-antenna pair with a shared radiator for fifth-generation (5G) multiple-input multiple-output (MIMO) metal-rimmed smartphones. The wideband decoupling property of the dual-antenna pair is realized by the combination of the orthogonal monopole/dipole modes in the lower band and the orthogonal slot/open-slot modes in the higher band. With the orthogonal-mode design scheme, the dual-antenna pair shows a wide impedance bandwidth of 3.3–5.0 GHz and a high isolation of more than 21.0 dB across the entire band without using any external decoupling structures. By arranging four such dual-antenna pairs at two side edges of the smartphone, an $8 \times 8$ MIMO system is fulfilled. Both the simulation and measurement results show that the proposed $8 \times 8$ MIMO system could offer an isolation of better than 12.0 dB and an envelope correlation coefficient of lower than 0.11 between all ports. The measured average antenna efficiencies are 74.7% and 57.8% for the two antenna elements of the dual-antenna pair. We portend that the proposed design scheme, with merits of shared radiator, wide bandwidth, and metal rim compatibility, has the potential for the application of future 5G smartphones. [ABSTRACT FROM AUTHOR]

In this article, the mutual coupling reduction of a two‐port planar inverted‐F antenna (PIFA) using a planar electromagnetic bandgap (EBG) structure is presented and investigated for multiple input multiple output/diversity applications. The planar EBG structure is designed for etching on the ground plane of the device. The EBG and the antenna design parameters are identified and the frequency scalability of the design is illustrated by showing two separate designs at 2.45 and 3.50 GHz. The optimized 2.45 GHz design demonstrates 25 dB more coupling reduction compared to the state of the art PIFA with a slot on the ground. Analyses of efficiency and effective diversity gain are also performed which show excellent performance. [ABSTRACT FROM AUTHOR]

This paper characterizes the performance metrics of MU-MIMO systems under Rayleigh fading channels in the presence of both cochannel interference and additive noise with unknown channel state information and known correlation matrices. In the first task, we derive analytical expressions for the cumulative distribution function of the instantaneous signal-to-interference-plus-noise ratio (SINR) for any deterministic beamvectors. As a second task, exact closed-form expressions are derived for the instantaneous capacity, the upper bound on ergodic capacity, and the Gram-Schmidt orthogonalization-based ergodic capacity for similar intra-cell correlation coefficients. Finally, we present the utility of several structured-diagonalization techniques, which can achieve the tractability for the approximate solution of ergodic capacity for both similar as well as different intra-cell correlation matrices. The novelty of this paper is to formulate the received SINR in terms of indefinite quadratic forms, which allows us to use complex residue theory to characterize the system behavior. The analytical expressions obtained closely match simulation results.

In this communication, a dual-polarized cross-slot antenna is proposed with a relative small dimension. Orthogonal polarizations with high port isolation are provided by the cross-slot structure. A dual-mode colocated feeding network is properly integrated with the cross slot, without occupying extra area. Therefore, the overall dimension of the proposed antenna is only $0.293\lambda _{0} \times 0.293\lambda _{0} \times 0.008\lambda _{0}$ ($\lambda _{0}$ is the free space wavelength at center frequency). A prototype is fabricated and measured to prove the design strategy. In such a compact antenna volume, the −10 dB impedance bandwidths for both orthogonal polarizations are over 6%, with the port isolation better than 30 dB and radiation efficiency over 68%, exhibiting potential applications in space-limited systems, such as access points and portable base stations. [ABSTRACT FROM AUTHOR]

A new ultra-wideband multimode (MM) antenna design that enables the detection/transmission of two orthogonal field components over a nearly hemispherical coverage area is presented in this paper. It integrates and colocates two perpendicularly oriented bow-tie dipole elements, a short convex monopole and four horizontally oriented tapered slot antenna (TSA) elements (formed by the dipoles) in order to produce four decoupled and complementary gain patterns. The antenna feeding structure includes four single-ended transmission lines supporting the desired set of individual excitation modes. Experimental verification confirms the predicted negligible coupling between the antenna operating modes and orthogonality of the corresponding radiated field patterns. These unique features can be exploited in applications where pattern and polarization diversity are of importance. In this study, we have evaluated the proposed antenna as a MIMO base station antenna and characterized it in two different propagation scenarios. For this example, it has been shown that the utilization of the additional monopole and TSA modes plays an important role in maximizing MIMO efficiency in line-of-sight (LOS) scenarios and at the same time provides additional independent data streams in rich scattering scenarios. In both considered scenarios, the antenna is shown to have a MIMO frequency bandwidth of 85%. [ABSTRACT FROM AUTHOR]

In this paper, antenna diversity is used to improve the outage performance of downlink non-orthogonal multiple access (NOMA) systems combined with single-user multiple-input multiple-output (SU-MIMO) due to the statistical channel state information (CSI), that the transmitter only knows the statistical characteristic associated with each user's channel matrix. We design the precoding and detection vectors, which makes the proposed MIMO-NOMA system reduce to a single-antenna NOMA system with statistical CSI. Next, a dynamic power allocation scheme is proposed to maximize the ergodic sum rate of the considered NOMA group with the minimum ergodic rate constraints of the weaker users. Under this power allocation, we analyze the impact of user clustering and then develop a novel user clustering algorithm. Also, the outage analysis indicates that the proposed system only obtains receive diversity and under the proposed power allocation, the users’ diversity gains are linear with their successive interference cancellation decoding orders. Simulation results confirm our proposed analysis. [ABSTRACT FROM AUTHOR]

This paper presents a planar omnidirectional multiple-input multiple-output (MIMO) antenna with pattern phase diversity. The profiles of conventional dual-polarized omnidirectional MIMO antennas are too high to be planar integrated due to the limited bandwidth of vertical-polarized element. Therefore, a dual-channel horizontal-polarized MIMO antenna is proposed for the planar integration of omnidirectional MIMO antenna. The antenna is formed with four-element folded dipole array, and a compact feed network with two sets of 90° progressive phases is employed to feed the two channels with shared elements, thus the antenna can be integrated into a sheet of substrate with an ultralow profile of 0.8 mm. Although the polarization and radiation pattern (amplitude) of the two colocated channels are the same with each other, a high isolation is still achieved as a result of the orthogonal pattern phase. A prototype was fabricated to validate the performance. The measured highest isolation between two channels is 31.7 dB, and −10 dB isolated bandwidth is 2.29–2.57 GHz (11.7%) with S11 < −14 dB and envelope correlation coefficient less than 0.05, which shows a good diversity performance. Therefore, the proposed dual-channel antenna gives a feasible solution for the planar integration of the omnidirectional MIMO system. [ABSTRACT FROM AUTHOR]

Space-shift-keying (SSK) and spatial modulation (SM) enable multiple antenna transmission systems to convey information on antenna indices. While SSK/SM helps reduce the number of radio frequency (RF) chains, large numbers of antennas and low spatial correlations are required to achieve high data rates. This work investigates the use and design of multifunctional reconfigurable antennas (MRAs) for SSK/SM based transmission where a single-element MRA generates large numbers of modes. To enhance legacy SSK/SM performance while reducing RF hardware complexity, we propose single- and multi-carrier antenna mode-shift keying (MoSK) and mode modulation (MoM) schemes facilitated by MRAs. Based on an error probability analysis, we determine criteria for MRA design and mode set selection suitable for MoSK/MoM. We also develop two MRA designs and investigate their performances over Rayleigh fading channels. We argue that by creating MRA modes with low pattern correlations, channel correlations can be reduced to improve the detection performance. Extensive simulations demonstrate that MoSK/MoM performance exceeds that of SSK/SM along with significant complexity reduction. For instance, a single-carrier MoSK/MoM using a single MRA with 8 modes achieves about 2 dB gain compared to legacy SSK/SM requiring 8 antennas, and by multi-carrier MoSK/MoM using 4 subcarriers, an MRA with 32 modes can attain an error rate performance comparable to this single-carrier system. [ABSTRACT FROM AUTHOR]