Search

In order to improve the spectrum effectiveness, decrease the power consumption of wireless communication system, for a two-way cooperative non-orthogonal multiple access (NOMA) network with simultaneous wireless information and power transfer (SWIPT), an adaptive power splitting scheme of SWIPT was proposed. Based on the decode-and-forward protocol and the users' distance information, the successive interference cancellation was carried out at the relay to decode the users' messages and harvest the energy from the sources. An adaptive power splitting scheme was proposed based on users' channel state information, which the relay could successfully decode the users' information and harvest the most energy from the sources. Based on the harvested energy, the relay forwarded the decoded information of the users in the next time slot. According to the proposed adaptive power splitting scheme, the overall outage probability, end-to-end outage probability, and the diversity gain at high signal-to-noise ratio were derived. Compared with three-way cooperative orthogonal multiple access network with fixed power splitting of SWIPT, the proposed adaptive power splitting of SWIPT for two-way cooperative NOMA networks can achieve much better outage performance. [ABSTRACT FROM AUTHOR]

We proposed the statistical misalignment model and the power-efficient configuration of transceivers for bi-directional multi-input and multi-output (MIMO) based vertical free space optical (FSO) links. Spatial diversity based MIMO FSO systems could be used to mitigate atmospheric fading issues. However, the increased number of channels can cause additional pointing error in pointing, acquisition and tracking (PAT) systems. The statistical misalignment model for detecting misalignment error is derived from the multiple transceivers. For the bi-directional characteristics of non-terrestrial back-haul networks, transmission performance is down-leveled to the worse in the asymmetric MIMO configuration of transceivers. The symmetric structure can mitigate the effect of increased pointing error to improve transmission performance. The proposed technique can be applied to the design of power-efficient FSO systems for non-terrestrial wireless back-haul networks. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications 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.)

In this paper, we analyzed the diversity performance with increased pointing error caused by multiple beam transmissions for spatial diversity based vertical free space optical (FSO) back-haul links. For power-limited FSO systems, the spatial diversity technique can be employed to mitigate the atmospheric fading issues in vertical FSO links. However, the arrangement of multiple transmitters to achieve independent channels can cause additional alignment errors in the misalignment detection process of pointing, acquisition, and tracking (PAT) systems, as demonstrated by the experiment results. The increase of misalignment makes the pointing loss severe to reduce the achievable diversity gain, which results in insufficient received power to satisfy the system requirements. The system optimization with the statistical misalignment model can mitigate the effect of increased pointing error and improve the diversity gain as the number of channels increases. The proposed scheme provides an enhanced link margin for designing seamless FSO wireless back-haul networks for next-generation wireless communication systems.

In this study, a multiple-input multiple-output (MIMO) antenna for wide scanning is designed. By adding slits to the patches, each element is intended to strengthen the isolation between the radiating elements. The proposed high isolation and wide scanning antenna combine to achieve the desired phased-array antenna. The array has a main beam pointing to the desired scanning region and a minimum side lobe level (SLL) in the undesired direction. A compact and linear eight-element array with an interelement spacing of λ / 2 is designed and analyzed for beam scanning in the E-plane. Considering the worst case, the proposed array has a very low mutual coupling of (S21 = −24 dB), and it realizes a gain of 9.3 dBi and an SLL of 11 dB at a scanning angle of 70 ∘ . The antenna performance was studied in terms of the S-parameter, radiation patterns, beam-scanning performance, envelope correlation coefficient (ECC), diversity gain (DG), peak gain, and efficiency. A close agreement was observed between the simulated and measured results. [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) multiple-input-multiple-output (MIMO) antennas promise a wide range of interesting applications in various radio frequency (RF) systems. However, the prime challenges in realizing such systems include achieving a wider bandwidth, significant isolation between the antennas and compactness. This research demonstrates a compact MIMO antenna having a prominent isolation level for portable UWB applications. The proposed antenna comprises two modified rectangular radiating elements with narrow slots in the ground plane, achieving an enhanced bandwidth from 2.1 to 16.9 GHz covering the S, C, X and Ku bands. Meanwhile, two inverted L-shaped stubs are introduced into the ground structure to obtain a higher isolation greater than 16 dB in the entire spectrum. The proposed antenna is of compact size (36 × 38 mm2) and exhibits excellent performance in terms of return loss, mutual coupling, envelope correlation coefficient (ECC), diversity gain (DG) and total active reflection coefficient (TARC). [ABSTRACT FROM AUTHOR]

A quad-port MIMO antenna is constructed and studied in this communication with single resonating bands (wideband) for WLAN & WiMAX applications. It is designed by etching out a circular slot from a patch placed on the front side of the substrate & a feeder line on the backside of the substrate. The proposed structure has ≤−10 dB impedance bandwidth of 2540 MHz (4.36–6.90 GHz). To legitimize the work attributes of the proposed MIMO antenna, diversity parameters such as total active reflection coefficient; envelope correlation coefficient (ECC) & diversity gain are calculated. The isolation is more than 25 dB, justifying the suggested design's acceptability as a quad-port MIMO antenna. The suggested design's examination revealed the steady performance and a high degree of agreement between the simulated and measured findings. [ABSTRACT FROM AUTHOR]

In this paper, we present a new design for a multiple-input multiple-output (MIMO) antenna with four ports operating in wide and multi-millimeterwave (Mm-Wave) bands for various 5G applications (including the internet of things (IoT), communication devices, and smartphones). The antenna is designed in a rectangular zigzag shape with slots to make the antenna operate at different frequencies. For this, the antenna operates at multiple frequencies from 38 to 62 GHz, so it supports all advanced wireless communication applications. The most important characteristic of the design is its small size and compact structure compared to designs presented by researchers in previous literature so the antenna dimensions for four elements are 29×49 mm2. The antenna performance based on the results obtained from CST Studio Suite is good since the reflection coefficients of the antenna resonate at six main frequencies are 39.128 GHz, 42.992 GHz, 47.384 GHz, 51.536 GHz, 55.472 GHz, and 59.288 GHz. In addition, the isolation value between all antenna elements is =30 dB and the diversity gain value for all frequencies is 10 dB. Moreover, a very small value was obtained for the envelope correlation coefficient (ECC) is <4.0576 × 10-11. Finally, the results indicate a favorable design and potential competitor for all 5G MIMO Mm-Wave applications. [ABSTRACT FROM AUTHOR]

In this work, the asymptotic performance analysis over double shadowed κ - μ fading channel is presented. More specifically, the unified asymptotic tight performance bounds for maximum ratio combining , selection combining and equal gain combining diversity receptions is presented. The system performance in terms of the outage probability (OP), symbol error probability (SEP) (coherent/non-coherent), the average probability of detection, and the average area under the receiver operating characteristic curve (AUC) is studied. To gain more insights and to validate the asymptotic slope of the results, the coding gain and diversity gain for OP, SEP, probability of missed detection, and complementary AUC for all the diversity techniques are also presented. It is found that the asymptotic slope of all the performance parameters and diversity techniques depend only on the number of multipath clusters and the diversity order of the system. Further, simulation results are presented to demonstrate the effectiveness of the proposed methodology under various channel conditions in diverse field of applications, such as vehicle-to-vehicle communication, wearable communication, and wireless power transfer related technologies. [ABSTRACT FROM AUTHOR]

This paper presents a method for designing a new two-element ultra-wideband (UWB) multiple-input-multiple-output (MIMO) antenna. We propose the design of an ultra-wideband antenna has been proposed with a study of its properties. An isolation technique using well-designed metamaterials is presented to achieve the miniaturization and performance of the two antennas and ensure proper operation of the MIMO system with a very small spacing between radiating elements (λ/12) where λ is the length waves in a vacuum. The metamaterials used considerably reduce the coupling of multi-antennas. The application of these materials called split-ring resonator (SRR) on the antenna patch plane has contributed to the increase in the performance of the antenna studied in terms of S parameters, multiplexing efficiency, diversity gain (DG), radiation properties and envelope correlation coefficient (ECC). This increases the transmission rate. This antenna system offers advantages such as reduction in weight and bulk, which facilitates its integration into a receiver, dedicated to 5G and connected objects.

In this paper, a coplanar waveguide-fed ultra-wideband-multiple-input and multiple-output (UWB-MIMO) antenna with a novel stub for isolation has been presented. The dimensions of the proposed antenna are 18 × 22 × 1.6 mm3. The proposed antenna is design on an FR4 substrate and simulated in CST studio. The |S11| of the presented MIMO antenna is less than −10 dB between 2.8 and 13 GHz with an impedance bandwidth of 10.2 GHz. The envelope correlation coefficient (ECC) is less than 0.007 and diversity gain (DG) is greater than 9.97 dB. The proposed UWB-MIMO antenna is analyzed in terms of isolation, reflection coefficient, current distribution, ECC, DG, peak gain, multiplexing efficiency, and radiation pattern. [ABSTRACT FROM AUTHOR]

In this paper, the outage performance of wireless networks with unstructured topologies is investigated. The network reliability perspective of graph theory is used to obtain the network outage polynomial of generalized wireless networks for both uncorrelated and correlated wireless channels. A relationship is established between the max-flow min-cut theorem and key communication performance indicators. The diversity order is equal to the size of the minimum cut-set between source and destination, and the coding gain is the number of cut-sets with size equal to the minimum cut. An ergodic capacity analysis of arbitrary network topologies based on the network outage polynomial is also presented. Numerical results are used to illustrate the technical definitions and verify the derivations. [ABSTRACT FROM AUTHOR]

In this research study, a compact dual-polarized co-radiator ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with improved impedance bandwidth and isolation is proposed for wireless applications. The designed co-radiator has an overall area of 0.3λo × 0.3λo mm2 (where, λo is free space wavelength corresponding to the lower cut-off frequency, i.e., 3.1 GHz). The proposed resonator comprises of a hybrid geometry which is created with the combinations of a circular-shaped patch, a square, and two rectangular stubs. It is centrally aligned between two 50 Ω micro-strip feed lines that are positioned orthogonal to each other. Further, the modified ground plane is attached with the end-loaded line which provides broadband isolation over entire UWB frequency band. The simulated results of the proposed antenna exhibit wideband characteristics with impedance bandwidth of 3.1–16.9 GHz with minimum isolation of −15 dB. Moreover, all the radiation performance parameters are analyzed and discussed. Some important diversity parameters such as envelope correlation coefficient, mean effective gain, effective diversity gain, and channel capacity loss have also been evaluated. Furthermore, all the measured results of proposed antenna agree well with the simulated results which make the proposed antenna a suitable candidate for UWB-MIMO wireless applications. [ABSTRACT FROM AUTHOR]

Although the widely linear least mean square error (WLMMSE) receiver has been an appealing option for multiple-input-multiple-output (MIMO) wireless systems, a statistical understanding on its pose-detection signal-to-interference-plus-noise ratio (SINR) in detail is still missing. To this end, we consider a WLMMSE MIMO transmission system with rectilinear or quasi-rectilinear (QR) signals over the uncorrelated Rayleigh fading channel and investigate the statistical properties of its SINR for an arbitrary antenna configuration with $N_t$ transmit antennas and $N_r$ receive ones. We first derive an analytic probability density function (PDF) of the SINR in terms of the confluent hypergeometric function of the second kind, for WLMMSE MIMO systems with an arbitrary $N_r$ and $N_t=2, 3$. For a more general case in practice, i.e., $N_t>3$ , we resort to the moment generating function to obtain an approximate but closed form PDF under some mild conditions, which, as expected, is more Gaussian-like as $2N_r-N_t$ increases. The so-derived PDFs are able to provide key insights into the WLMMSE MIMO receiver in terms of the outage probability, the symbol error rate, and the diversity gain, all presented in closed form. In particular, its diversity gain and the gain improvement over the conventional LMMSE one are explicitly quantified as $N_r-(N_t-1)/2$ and $(N_t-1)/2$ , respectively. Finally, Monte Carlo simulations support the analysis. [ABSTRACT FROM AUTHOR]

A multiple-input multiple-output (MIMO) antenna with a defective ground surface (DGS) is proposed for next-generation millimeter-wave communication. The designed antenna consists of a pair of mushroom shape radiating units with two square ring-loaded defected common ground plane. The antenna is printed on duroid-5880 high-frequency laminates (loss tangent 0.0009, relative permittivity 2.2). Significant bandwidth ranges from 31.6 GHz to 48.8 GHz (impedance bandwidth of 43.17%) is obtained during the investigation of the antenna. The introduced MIMO antenna exhibits a low mutual coupling (|S21|, |S12| < −20) dB with the incorporation of DGS. The antenna performance parameters defined as return loss, radiation pattern, gain, the radiation efficiency is examined. Many diversity parameters are also discussed in terms of mutual coupling, envelop correlation coefficient (ECC < 0.002), diversity gain (DG > 9.995), and channel capacity loss (CCL < 0.3 bits/sec/Hz) across the ultra-wide band (UWB) frequencies. Simulated results are verified by the measured results, and good agreement is observed between them. These distinguishable attributes with the simple configuration model the propound MIMO antenna suitable for millimeter-wave applications. [ABSTRACT FROM AUTHOR]

A low-profile multiple-input/multiple-output (MIMO) antenna of dimension 0.5 λ 0 × 0.7 λ 0 is proposed in this communication. This antenna consists of four square radiating patches and a partial ground to which a fractal H-shaped metamaterial electromagnetic band gap (MM-EBG) isolator is etched below the substrate in between the gaps of adjacent pairs of radiating patches or on each arm of intersection of the antenna. The isolator structure is simple to design and is capable of reducing mutual coupling by 15 dB, 16 dB, and 9 dB between antenna elements 1 & 2, 1 & 3, and 1 & 4, respectively. Favorable performance in terms of envelope correlation coefficient (less than 0.1, 0.05, and 0.1) and diversity gain (greater than 9.96, 9.98, and 9.93 dB) with consistent frequency band ranging from 2.53 GHz to 7.3 GHz is exhibited by the proposed MIMO antenna. The results are compared with previous reported literature, and comparative results shows good performance in terms of bandwidth, ECC, diversity gain, and radiation characteristics with improved isolation. Also, an equivalent circuit model of proposed design is presented. The simulated design is validated by fabricating and testing. The measurement of performance parameters closely agree with the simulated ones and have the potential for S and C band applications such as WLAN, WiMAX, IoT, and 5G. [ABSTRACT FROM AUTHOR]

A tree-shaped graphene-based microstrip multiple-input and multiple-output (MIMO) antenna for terahertz applications is proposed. The proposed MIMO antenna is designed on a 600 × 300 μm2 polyimide substrate. The designed MIMO antenna provides a wide impedance bandwidth of 88.14% (0.276–0.711 THz) due to the suggested modifications in the antenna configuration. The MIMO design parameters like total active reflection coefficient (TARC), mean effective gain (MEG), envelope correlation coefficient (ECC) and diversity gain (DG), channel capacity loss (CCL) are evaluated, and their values are found within acceptable limits. The proposed MIMO structure offers MEG ≤ − 3.0 dB, TARC ≤ − 10.0 dB, DG ≈ 10 dB, CCL < 0.5 bps/Hz/s and ECC < 0.01 at the resonant frequency. At the resonant frequency, the isolation between the radiating elements of the proposed MIMO antenna is recorded as − 52 dB. The variations in operating frequency and S-parameters are also analyzed as a function of the chemical potential (μc) of the graphene material. The parametric analysis, structural design evolution steps, surface current distribution, antenna characteristics parameters and diversity parameters are discussed in detail in this paper. The designed MIMO antenna is suitable for high-speed short-distance communication, video-rate imaging, biomedical imaging, sensing and security scanning in the THz frequency band. [ABSTRACT FROM AUTHOR]

A novel multiband 2 × 2 dual-polarization antenna with couple of meander line structure is proposed for IoT connected devices. The MIMO antenna operates from 1.39 to 6.02 GHz with the gain of 7.35 dB and the return loss of less than −10 dB, within its effective bandwidth at both input ports. The proposed dual polarized antenna has a very high isolation of −27 dB between the input ports. The performance of 2 × 2 MIMO antenna is analyzed with respect to the correlation coefficient, channel capacity loss, diversity gain, mean effective gain and total active reflection co-efficient. For simulation, High Frequency Structure Simulation (HFSS) solver is used and it also calculates the MIMO antenna parameters. The projected antenna shows multiband operation with polarization diversity and high isolation among elements. It also offers a good mixture of coverage and capacity benefits, which is expected to support the future IoT connected devices. [ABSTRACT FROM AUTHOR]

Summary: The proposed research work is on fractal MIMO antenna with microstrip feeding for lower sub‐6 GHz. The design construct's goal is to improve the isolation among the patches and is constructed with a combination of circular strip and rectangular strip slots, and rectangular slots are introduced on the ground plane. The fractal‐shaped MIMO structure composes of FR‐4 material and compact size of 25 × 35 mm2. The current 2 × 1 fractal MIMO radiator resonates at a frequency 3.5 GHz for lower sub‐6‐GHz applications with directional radiation patterns. In this structure, the performance characteristics of design antenna parameters like S‐parameters, surface current distributions, and radiation pattern of the fractal MIMO radiator are investigated. In addition to antenna parameters, MIMO parameters like diversity gain (DG), mean effective gain (MEG), channel capacity loss (CCL), total active reflection coefficient (TARC), and time‐domain analysis parameters are also evaluated. It has been observed that the MIMO parameters of the antenna are in the acceptable range. Fractal‐based prototype MIMO structures are fabricated as well as tested for effective radiation and impedance. The improvised MIMO design that's been installed on a printed circuit board with connector, device housing, compact size, and various types of housing shows better performance compared to the conventionally designed antennas. [ABSTRACT FROM AUTHOR]

An efficient Multi-Input Multi-Output (MIMO) antenna system with a spatial diversity configuration for the Fifth Generation (5G) mobile handsets is constructed from a compact-size quad-band (28=45=51=56 GHz) microstrip patch antennas. The antenna is constructed as primary and secondary patches which are capacitively coupled and designed to realize impedance matching and to produce appropriate radiation patterns in the four frequency bands. The novel quad-band patch antenna includes complicated radiation mechanisms required for multiple-band operation. Twoport and four-port MIMO antenna systems that employ the quad-band patch antenna are proposed in the present work for the 5G mobile handsets. Numerical and experimental investigations are achieved to assess the performance of both the single-element antenna and the proposed MIMO antenna systems including the return loss at each antenna port and the coupling coefficients between the different ports. It is shown that the simulation results agree with the experimental measurements and both show good performance. The bandwidths achieved around 28, 45, 51, and 56 GHz are about 0:6, 2:0, 1:8, and 1:3 GHz, respectively. The radiation patterns produced when each port is excited alone are shown to be suitable for spatial diversity scheme with high radiation efficiency. It is shown that the envelope correlation coefficient (ECC) and the diversity gain (DG) are perfect over the four frequency bands. [ABSTRACT FROM AUTHOR]

In this article, we investigate the potential enhancements in signal reliability which can be achieved using a millimeter-wave distributed antenna system (DAS) within an indoor environment. To achieve this, we measured the signal power simultaneously received at nine ceiling-mounted access point (AP) locations likely to be used in future indoor DAS deployments while a mobile user imitated making a voice call on a hypothetical user equipment. Key metrics, associated with the performance of multiple antenna systems, such as the cross correlation coefficient (CCC) and channel power imbalance (CPI) are determined. It was found that line-of-sight (LOS) and quasi-LOS (QLOS) links with the APs typically led to higher CCC values than the non-LOS (NLOS) cases. Similarly, LOS and QLOS links typically produced higher CPI values between APs than the NLOS case. To enable the reproduction of our results, we have successfully applied autoregressive moving average and autoregressive integrated moving average modeling to the CCC and CPI time series. The performance improvement that can be achieved using a DAS instead of a single AP was evaluated using three commonly deployed diversity combining schemes, namely, selection combining, equal gain combining, and maximal ratio combining along with three AP selection mechanisms, namely, per-sample random AP selection, one-shot AP selection, and per-sample optimal AP selection. Finally, we have provided some useful insight into the influence of differing AP numbers on the diversity gain when considering the aforementioned AP selection methods. [ABSTRACT FROM AUTHOR]

The safety of vulnerable road users is paramount, particularly as we move towards the widespread adoption of autonomous and self-driving vehicles. In this study, we investigate the use of a six-element distributed antenna system (DAS), operating at 5.8 GHz and mounted on the exterior (i.e., roof and wing mirrors) of an automobile, to enhance signal reliability for pedestrian-to-vehicle (P2V) communications. Due to its low complexity and ease of implementation, we consider the use of a switch-and-examine combining with post-examining selection (SECps) scheme to combine the signal received by the DAS. During our experiments, a pedestrian wearing a wireless device on their chest either stood stationary or walked by the side of a road. It was found that the overall signal reliability depends on not only the number, but also different groupings of the antennas which are selected. The goodness-of-fit results have shown that the temporal behavior of the diversity gain was adequately described by the Gaussian distribution. Building upon this, we also provide some useful insights into the antenna selection through the comparison of three different antenna selection mechanisms, namely per-sample random antenna selection, one-shot antenna selection and per-sample optimal antenna selection. [ABSTRACT FROM AUTHOR]

This article presents a compact Co-Planar Waveguide (CPW) fed antenna for next-generation Vehicular Communications. The antenna is designed by employing two rectangular stacked patch structures and slots, making the antenna resonate at dual frequency bands. The analytical study of antenna design is carried out using the governing microstrip patch equations. On optimizing the patch's dimensions for CPW structures, the desired frequency range of operation is obtained for the single element antenna structure. The designed antenna resonates at 3.5 GHz (LTE-42 Band) and 5.9 GHz (DSRC Band), yielding this antenna to be a prime component for Vehicular to Everything (V2X) Communication. The optimized single-element antenna structure is 35 mm × 20 mm designed on an FR-4 substrate of thickness 1.6 mm. The substrate has a dielectric constant of 4.4 and a loss tangent value of 0.001. Further, the antenna structure is developed as a 4-element MIMO configuration with the distance between adjacent antenna elements to be 10 mm. The adjacent antennas in the MIMO configuration are positioned orthogonal to each other, thereby exhibiting better isolation between the antenna elements. The antenna has a reflection coefficient value of < −10 dB within the bandwidth of interest and VSWR less than 2. The Gain value of the designed antenna ranges between 2.8 and 2.9 dBi at 3.5 GHz and between 3.6 and 3.7 dBi at 5.89 GHz. The overall efficiency of the antenna element is between 60 and 80% at both frequency bands. MIMO parameters are analyzed by calculating the Channel Capacity Loss (CL), Diversity Gain (DG), Envelope Correlation Coefficient (ECC) and Total Active Reflection Co-Efficient (TARC). The designed antenna is fabricated and tested, which shows the measured results coincide with the simulated antenna results. The overall dimension of the MIMO configured antenna design is 60 mm × 60 mm × 1.6 mm, which is highly compact and is a suitable candidate for deployment of Vehicle to Vehicle (V2V), Vehicle to Infrastructure (V2I), and Vehicle to Network (V2N) scenarios. [ABSTRACT FROM AUTHOR]

Abstract This paper is concerned with diversity gain analysis for millimeter-wave (mmWave) massive MIMO systems employing distributed antenna subarray architecture. First, for a single-user mmWave system in which the transmitter and receiver consist of K t and K r subarrays, respectively, a diversity gain theorem is established when the numbers of subarray antennas go to infinity. Specifically, assuming that all subchannels have the same number of propagation paths L, the theorem states that by employing such a distributed antenna subarray architecture, a diversity gain of K r K t L−N s +1 can be achieved, where N s represents the number of data streams. This result means that compared to the co-located antenna architecture, using the distributed antenna subarray architecture can scale up the diversity gain proportionally to K r K t . The analysis of diversity gain is then extended to the multiuser scenario as well as the scenario with conventional partially connected radio-frequency structure in the literature. Simulation results obtained with the hybrid analog/digital processing corroborate the analysis results and show that the distributed subarray architecture indeed yields a significantly better diversity performance than the co-located antenna architectures.

This paper proposes a method for designing a new ultra wide band (UWB) multiple-input multiple-output (MIMO) antenna with two and four elements. First we presented an ultra-wide band antenna we studied these performances. Then, we studied the application of metamaterials to the design of MIMO antennas for miniaturization and the performance of antennas, in order to guarantee the proper functioning of the MIMO system with a much reduced separation distance between the radiating elements (λ/12), where the coupling can be very weak. The application of these circular double ring SRRs materials on the front plan of the antenna has contributed to the increasing of the antenna performance is studied in terms of S-Parameters, efficiency, diversity gain (DG), radiation properties and envelop correlation coefficient (ECC). It offers advantages such as the reduction of weight and congestion that is beneficial for their integration into satellite communications systems. [ABSTRACT FROM AUTHOR]

In this letter, the impact of residual hardware impairment (RHI) on the performance of non-orthogonal multiple access (NOMA) is investigated by taking into account the effect of imperfect successive interference cancellation (ipSIC). The new exact and asymptotic pairwise error probability (PEP) expressions with RHI under ipSIC are derived over Rayleigh fading channels. The asymptotic PEP expression is subsequently utilized to quantify the diversity orders achieved by NOMA users in the presence of RHI. In particular, we show that the effective diversity order of each NOMA user equals to user’s order for both ideal and non-ideal (RHI) scenarios. Leveraging the derived PEP, the union bound on the bit error rate of NOMA users are further evaluated. We demonstrate that the impact of RHI with ipSIC on each user’s error rate performance is negligible. In contrast, when perfect SIC is considered, such effects are significant. Numerical and Monte Carlo simulation results are presented to corroborate the analysis. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new design for a four-ports Multiple-Inputs Multiple-Outputs (MIMO) antenna. The main aim behind this work in this paper is to present an antenna with a smaller size compared to the designs presented by researchers in previous works, and it operates in the wide and multi-bands required by most advanced communication systems. The structural scenario of this antenna is square-shaped designed using the CST Studio Suite with real dimensions of 36 mm × 36 mm and a thickness of 1.6 mm. This antenna carries both wide and multi bands and operates in the Millimeter-Wave (mm-Wave) spectrum. This antenna has been designed to be suitable for all the fifth-generation (5G) communication applications. Based on the results obtained from the CST, it is observed that the impedance bandwidth of the MIMO antenna system is from 39 to 75 GHz. In addition, the antenna gave excellent results as each antenna in the MIMO configuration works independently because the isolation ratio among all ports is greater than 24.539 dB, and it reaches 43 dB at a frequency of 71 GHz. Moreover, a set of key performance measures of the MIMO antenna were analyzed, the most important which is the Envelope Correlation Coefficient (ECC) and found that the ECC value is less than 0.00075. So, this value is very small compared to the ECC values that were presented in previous researches. [ABSTRACT FROM AUTHOR]

This study presents a compact dual element wearable ultrawideband (UWB) multi-in multi-out (MIMO) antenna with increased port isolation. The suggested design consists of a jeans substrate in which a tree-fashioned stub comprising of eight branches is introduced in the middle position of the partially etched antenna ground for improving the characteristics of port isolation. The proposed design occupies the frequency spectrum operating from 1.71 to 12.63 GHz (impedance bandwidth of around 152.3%) and satisfies the bandwidth demands for WiMAX (3.2-3.8 GHz), WLAN (5.15-5.35/5.72-4.85 GHz), the C Downlink-uplink bands (3.7-4.2/5.9-6.425GHz), ITU bands (8-8.5GHz) and the downlink defense band (7.2-7.5GHz). The antenna is able to maintain isolation between the ports >22dB across the entire UWB frequency spectrum. The coefficient of the envelope correlation for the whole operating band was observed to be <0.012 along with a very high diversity gain >9.9. The channel power loss of the proposed wearable UWB MIMO antenna is found to be <0.27 bit/s/Hz. The suggested UWB MIMO antenna, fascinated with optimization, covers an area of 35 × 35 mm2. The suggested design is also able to perform satisfactorily when attached on-body. Simulation and testing fairly identified the performance of the antenna and rendered it to be an upstanding choice for wearable UWB applications. [ABSTRACT FROM AUTHOR]

We investigate the beamforming for the multi antenna cooperative non-orthogonal multiple access (NOMA) system, where an access point (AP) delivers messages for multiple user terminals (UT) with successive interference cancellation (SIC) reception method. Some UTs with multiple antennas cooperate with the AP transmission to improve the diversity and the average power performance. We formally present two optimal beamforming schemes at the AP and at the cooperative UTs. One scheme has no power limitation for the cooperative UTs, while the other one does have such limitation. We guarantee that the rank one beamformer is sufficient to achieve the optimal points so that the proposed schemes have rank one semi-definite programming (SDP) structure. Simulation results show the performance gain of the multi-antenna cooperative NOMA schemes in the sense of diversity and the average power. [ABSTRACT FROM AUTHOR]

In recent years, OFDM with index modulation (OFDM-IM) has become a potential technique due to its improvement of diversity gain. In typical OFDM-IM schemes, incoming information bits are divided into two parts, symbols bits, and index bits. However, the symbol bits conveyed by each OFDM symbol suffer from low diversity order, which has a negative impact on diversity gain. In this paper, we propose the scheme called OFDM with all index modulation (OFDM-AIM), which replaces the PSK/QAM constellation modulator with subblock modulator and simplifies the structure. With such an arrangement, the subblocks of OFDM-AIM become flexible, which contributes to achieving the higher diversity order of the system. Moreover, we study the effects of Euclidean distance and diversity order based on the unconditional pair error probability, which gives the guideline to design a legitimate subblocks set. Then the algorithm to build the subblocks set with higher diversity order is proposed, which can achieve better diversity gain. Theoretical and simulated results show that the OFDM-AIM scheme is capable of achieving better BER performance than other index modulated OFDM schemes.

This paper considers the application of non-orthogonal multiple access (NOMA) into cooperative cognitive radio (CR) networks with simultaneous wireless information and power transfer (SWIPT). For NOMA in cooperative CR networks with SWIPT, the cognitive relay harvests the transmission power from the secondary transmitter with power splitting scheme, while the fixed power allocation scheme is used for the NOMA protocol. The closed-form analytical expression of the overall outage probability for the proposed networks is derived, as well as its diversity order at high signal-to-noise ratio (SNR) region is investigated. Furthermore, compared to OMA in cooperative CR networks with SWIPT, the proposed scheme can always achieve the same diversity order, but lower overall outage performance. Compared with NOMA in cooperative CR networks using its own battery for transmission, the SWIPT NOMA in cooperative CR networks will lead to losing a little of the overall outage performance, but without losing the diversity order.

In this paper, through a mathematical analysis of the overall links capacity equation, we present an efficient partner selection criterion in a cooperative communication scheme with a time-varying fading channel and severe interference on the cooperative links to mitigate the interference effect without the need for additional power consumption to transmit the information signal. For the partner(s) selection, we examine different selection criteria based on minimizing the error rate and maximizing the end-to-end system capacity to collaborate in the delivery process. We prove that in the proposed relay scheme, a simple selection criterion independent of the interference state is a sufficient and efficient criterion for selecting the partners out of terminals suffering from interference. It is found that the use of a simple and efficient selection criterion for assigning multiple cooperating terminals is able to achieve a significant diversity gain, conserve the energy of individual terminals, and improve the error performance with low computational complexity, even in the absence of the interference state information. All of the theoretical findings are verified through simulation studies.

In this paper, we analyze the impact of buffer-aided full-duplex successive relay selection schemes with energy harvesting capability of relay nodes in amplifying and forward (AF) and decode and forward (DF) relaying environments for the Internet of Things networks. We propose to select a relay pair based on the energy harvested and signal strength at relay and destination to receive and transmit in the same time slot, respectively. Contrary to the previous relay pair selection schemes which are based on the signal strength only and cause the relay overuse problem, the proposed scheme ensures the balanced use of energy of relay nodes. The proposed relay selection scheme is implemented with the time switching (TS) and power splitting (PS)-based energy harvesting models in AF and DF relaying environments separately. Furthermore, we derive the closed-form expression of the outage probability and average throughput for both the TS and PS approaches in the DF and AF relaying modes. We compare the proposed relay selection scheme with the S-MMRS scheme and prove that the proposed scheme significantly reduces the outage probability and improves the average throughput. Furthermore, the analytical findings are reinforced with the extensive Monte Carlo simulations.

In recent years, multiple-input-multiple-output (MIMO) antennas with the ability to radiate waves in more than one pattern and polarization play a great role in modern telecommunication systems. This paper provides a theoretical review of different mutual coupling reduction techniques in MIMO antenna systems. The increase in the mutual coupling can affect the antenna characteristics drastically and therefore degrades the performance of the MIMO systems. It is possible to improve the performance partially by calibrating the mutual coupling in the digital domain. However, the simple and effective approach is to use the techniques, such as defected ground structure, parasitic or slot element, complementary split ring resonator, and decoupling networks which can overcome the mutual coupling effects by means of physical implementation. An extensive discussion on the basis of different mutual coupling reduction techniques, their examples, and comparative study is still rare in the literature. Therefore, in this paper, different MIMO antenna design techniques and all of their mutual coupling reduction techniques through various structures and mechanisms are presented with multiple examples and characteristics comparison.

Mutual coupling between the multiple antenna designs is a critical problem which deteriorates the performance of multiple input multiple output (MIMO) system. It affects the antenna efficiency and influences the correlation. In this paper, a study on the isolation between the multiple antenna elements is presented. The antennas are placed on a cost-effective compact dielectric substrate with different orientations to minimize the correlation. A CPW fed antenna is designed using FR4 substrate, using which two and four element antenna structures are developed. The performance parameters are analysed, wherein the envelope correlation coefficient (ECC) has to be less than 0.5, diversity gain nearer to 10 dB in the operating bandwidth, mean effective gain (MEG) less than 3 dB, channel capacity loss (CCL) less than 0.4 bits/s/Hz and the isolation between the antenna elements well above 20 dB. Acceptable gain, high radiation efficiency, and stable radiation pattern of the proposed design are analysed and the fabricated prototype of two and four element is measured for its performance parameters. All the necessary simulations are carried out in the EM simulator Ansys HFSS v.14.0 and a detailed comparison study is done based on the existing antennas. [ABSTRACT FROM AUTHOR]

In this paper, we propose a generalized space-time block coded spatial modulation (GSTBC-SM) scheme for open-loop massive multiple-input and multiple-output (MIMO) downlink communication systems. Specifically, we firstly partition the information bits into multiple groups with each group modulated by the spatial modulation (SM), where the SM symbols are invoked for orthogonal STBC (OSTBC) and quasi-orthogonal STBC (Q-OSTBC) structures. Then, message passing (MP) and block minimum mean square equalization (B-MMSE) detectors are designed for our GSTBC-SM systems, to achieve near-optimal performance with significantly reduced complexity in massive MIMO configurations. Finally, we derive the theoretical average bit error probability (ABEP) of the proposed scheme. The main contribution is that the propose scheme achieves high transmission rate and diversity gain even with small number of radio frequency (RF) chains at the transmitter. Simulation results verify the theoretical derivations and show that the proposed GSTBC-SM scheme provides near 20 dB gain over the conventional GSTBC scheme under massive MIMO configurations. [ABSTRACT FROM AUTHOR]

This paper investigates the diversity gain of a distributed cyclic delay diversity (dCDD) scheme for cyclic-prefixed single carrier systems in non-identical fading channels. Non-identical small-scale fading is assumed in the environment, in which non-identical line-of-sight and non-line-of-sight fading coexist. A condition for dCDD resulting in intersymbol interference free reception at the receiver, is extended to this new channel environment. For an overpopulated system setup, a generalized performance analysis, is not available from existing works, is conducted after developing closed-form expressions for the distribution of the signal-to-noise ratio (SNR) realized at the receiver. Since the order statistics are involved in the statistical properties of the SNR, the corresponding spacing statistics are utilized to derive feasible closed-form expressions. The finalized closed-form expressions are shown to provide very reliable outage probability and spectral efficiency of dCDD for underpopulated and overpopulated systems. An asymptotic performance analysis verifies the maximum achievable diversity of the dCDD even in the overpopulated case within the considered channel environment. Link-level simulations are conducted and these verify the maximum achievable diversity gain. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) appears as a promising multi-carrier waveform candidate for beyond 5G due to its attractive advantages such as operational flexibility and ease of implementation. However, OFDM-IM may not be a proper choice for 5G services such as enhanced mobile broadband (eMBB) since achieving high data rates is challenging because of its null subcarriers. One solution to enhance the spectral efficiency of OFDM-IM is the employment of multiple distinguishable constellations (modes) by also exploiting its null subcarriers for data transmission. This article proposes a novel IM technique called super-mode OFDM-IM (SuM-OFDM-IM), where mode activation patterns (MAPs) and subcarrier activation patterns (SAPs) are jointly selected and conventional data symbols are repetition coded over multiple subcarriers to achieve a diversity gain. For the proposed scheme, a low-complexity detector is designed, theoretical analyses are performed and a bit error rate (BER) upper bound is derived. The performance of the proposed system is also investigated through real-time experiments using a software-defined radio (SDR) based prototype. We show that SuM-OFDM-IM exhibits promising results in terms of spectral efficiency and error performance; thus, appears as a potential candidate for 5G and beyond communication systems. [ABSTRACT FROM AUTHOR]

In this paper, the error performance and spectrum efficiency (SE) of uplink massive multiuser spatial modulation (SM) MIMO systems with zero-forcing detection for perfect and imperfect channel state information (CSI) are investigated over composite Rayleigh fading channels. We firstly derive the error probabilities of transmit antenna index detection and transmitted symbol detection of each user. Using these results, the bit error rate (BER) performance of the system under perfect CSI is analyzed. Furthermore, a closed-form average BER of the system is derived. We generalize the analytical results of perfect CSI to those of imperfect CSI for practicality, and derive a closed-form BER for the system with imperfect CSI. Based on this, two asymptotic BER expressions are developed to characterize the error performance of the system for large-scale receive antennas and high SNR. By means of the asymptotic expressions, the diversity order of the system is attained. Besides, we derive a lower bound on the achievable SE of the system with imperfect CSI. With this lower bound, an approximate expression of the achievable SE is obtained in closed form. Simulation results indicate that our theoretical analysis is valid, and agrees with simulation results well. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a four‐element wideband monopole MIMO antenna. Initially, a single‐element wideband CPW‐fed antenna is designed operating in the range of 4.30 to 6.45 GHz. Using this design, an approach towards MIMO structure is studied. A two‐element structure is designed keeping them adjacent to each other, and the isolation between the antennas is observed. After which, a four‐element structure is designed having the best orientation in order to achieve good isolation between the antenna elements. The proposed antenna configuration has four identical CPW‐fed elements. The proposed configuration has a fractional bandwidth of 40.27% and has a simulated peak gain of 5.5 dBi. This antenna is intended to be used for WLAN, WiMAX, and satellite bands of range corresponding to 4.70–6.19, 5.5–5.7, and 5–6 GHz. All the necessary antenna simulations are simulated using Ansys HFSS and verified on NI AWR Design Environment. The fabricated model of the proposed design is measured for its performance parameters and validated. [ABSTRACT FROM AUTHOR]