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Summary: The increasing prevalence of MIMO technology in wireless communication networks is attributed to its ability to augment system capacity and dependability. Consequently, there is a notable enthusiasm for the advancement and implementation of S‐band applications. Nevertheless, the mutual coupling between numerous antennas presents a crucial obstacle to MIMO system performance. This paper presents a novel technique that utilizes a defective ground structure with parasitic components to increase antenna isolation and gain. Additionally, an L‐shaped slot is incorporated into the patch element to enhance the antennas impedance bandwidth. Antennas are intentionally placed in a perpendicular arrangement to minimize the impact of the coupling effects. The antenna exhibits an impedance bandwidth in the frequency range of 2.62–2.79 GHz. Furthermore, the utilization of a four‐element MIMO antenna setup with a defective ground structure yields outstanding isolation properties, with values notably lower than −25 dB. To achieve an optimal MIMO performance, we assessed various diversity parameters, including diversity gain, channel capacity loss, total active reflection coefficient, and envelope correlation coefficient. The parameter values were within acceptable limits (ECC < 0.04, DG = 10 dB, TARC < 0 dB, and CCL < 0.1 bits/s/Hz). This research paper therefore offers essential insights into the design and optimization of MIMO antennas specifically for 2.7 GHz applications. [ABSTRACT FROM AUTHOR]

Summary: A dual‐band (1.6–1.9 GHz and 3.3–3.9 GHz) eight‐antenna multiple‐input and multiple‐output (MIMO) system is proposed in this paper. The basic structure of the proposed antenna element consists of microstrip lines, cylindrically shaped shorting, and a rectangular‐shaped defected ground structure (DGS). This structure is responsible for the production of a self‐ isolated MIMO system. The performance of the MIMO antenna system is investigated by the detailed analysis of S‐parameters, Envelope Correlation Coefficient (ECC), Mean Effective Gain (MEG), Total Active Reflection Coefficient (TARC), and Channel Capacity (CC). The proposed MIMO antenna system offers a good S‐parameter, radiation pattern, and satisfactory isolation characteristics. The MIMO antenna system is fabricated on lossy high dielectric (εr = 4.3) FR4 substrate (loss tangent 0.02). The measured results are in good agreement with simulated one. The proposed antenna focuses on the 3.3–3.9 GHz frequency band, which covers bands 3.3–3.6 GHz (center frequency, 3.45 GHz) or 3.4–3.8 GHz (center frequency, 3.6 GHz) under the band below 6 GHz for 5G operation. [ABSTRACT FROM AUTHOR]

Summary: In communication systems, in order to increase spectrum efficiency, pulses with limited bandwidth that meet the Nyquist zero intersymbol interference criterion are usually used for transmission. However, the truncated pulse is conducive to the realization of the partial response signal transmission system. The actual method is to cut the finite bandwidth pulse into a finite and sufficient length in the time domain. This will make the overall impulse response no longer meet the Nyquist criterion and at the receiving end will produce intentional intersymbol interference, so demodulation requires complex sequence detection. In this paper, we consider the truncated root raised cosine modulation system with timing offset and compare the channel capacity of partial response signals with different parameters. At the receiving end, demodulation uses the turbo equalization with different equalization methods to eliminate the intersymbol interference of partial response signals. Among them, we use fewer symbol paths in the BCJR algorithm to calculate the maximum posterior probability to construct low‐complexity equalization and compare according to the computational complexity and performance results of different equalizations. [ABSTRACT FROM AUTHOR]

Summary: A novel multiple‐input multiple‐output double asymmetrical cylindrical dielectric resonator antenna (MIMO‐DCDRA) with modified stub line feed is discussed and proposed in this work. Two unequal CDRA are placed diagonally to each other and are electromagnetically coupled with feeding arrangement via two asymmetrical circular apertures. By performing the optimization of the dimensional parameters, a significant impedance bandwidth of 70.84% ranging from 2.87 to 5.76 GHz and axial ratio bandwidth (ARBW) of 34.89% is obtained. Antenna gain is about 5.0 dBi within the operating frequency. The proposed MIMO‐DCDRA exhibits a low mutual coupling of (|S21| & |S12| < −20 dB) with the incorporation of a neutralization line. There are various diversity parameters that 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/s/Hz) over the entire impedance bandwidth. [ABSTRACT FROM AUTHOR]

Summary: In this article, a novel and compact multiband quad port asymmetric coplanar strip‐fed triangular lamp post shaped printed multiple‐input and multiple‐output (MIMO) antenna has been presented. The proposed MIMO antenna is designed and developed on a FR‐4 (εr = 4.4) dielectric (40 × 40 × 1.6) mm3. The proposed MIMO antenna utilizes the pattern diversity technique to obtain the desired isolation among closely spaced radiators. Simulated and measured results indicate that |S11| of proposed lamp post shaped MIMO antenna array < −10 dB, that assures the operation in three frequency bands, namely, (2.27–2.42), (3.38–3.62), and (4.5–6.23) GHz, which are the operating bands of WiBro, Bluetooth, WiMAX, and WLAN/WiMAX, respectively. A peak radiation gain of 5.1 dBi is observed alongside with a maximal radiation efficiency close to 92% in operating band for the proposed MIMO antenna. A minimal isolation of −18 dB between the antenna elements has been observed in all three operating bands, which is necessary for improved performance to achieve high data transfer rates. Performance critical diversity characteristics such as diversity gain (DG), envelope correlation coefficient (ECC), total active reflection coefficient (TARC), mean effective gain (MEG), and channel capacity (CC) of the compact proposed lamp post shaped MIMO antenna have been calculated and found that the correlation coefficient was <0.001 with higher diversity gain > 9.95 dB and achieved better CCL < 0.4 bits/s/Hz in the respective operating bands. With these results, the proposed triangular lamp post shaped MIMO array is suitable for high data rate applications, which is one of the main concerns of 5G and beyond networks. [ABSTRACT FROM AUTHOR]

Summary: In this communication, a novel compact spanner shaped ultra‐wideband (UWB) antenna is designed for multiple input multiple output (MIMO) system applications. The proposed structure of size 24 × 32 mm2 (0.24λ0 × 0.32λ0, λ0 is calculated at lower band frequency) is designed and fabricated on widely available FR4 dielectric material with a dielectric constant of 4.4 and loss tangent of 0.02. The proposed structure comprises two spanner shaped antennas, a defected T‐shaped stub and a pair of small vertical strips. The defected T‐shaped stub and vertical strips are used for getting a complete UWB bandwidth and good isolation between two elements. It is performing from 3.0 to 11.0 GHz with isolation more than 20 dB in most of the operating region. The parametric studies have been done for the required parameters and figured out the surface current distribution at different resonant frequencies within the working region. The MIMO antenna diversity performance is confirmed with low values of envelope correlation coefficient (ECC < 0.005), channel capacity losses (CCL < 0.04 bits/s/Hz), acceptable mean effective gain (MEG ≤ −3 dB, MEG ratio = 0 dB), and total active reflection coefficient (TARC ≤ −10 dB) values. The peak gain values are varying from 1.5 to 6.0 dBi, and the radiation efficiency values are above 83% for the entire operating region. The simulated and measured values are well matched. [ABSTRACT FROM AUTHOR]

As the increasing demand of the radio spectrum, the researchers pay more attention to the technology of cognitive radio networks to improve the use of the scarce spectrum resources. Recently, cooperative communications combining with cognitive radio have been proposed in many literatures to improve the channel capacity. The primary users with poor transmission environment transmit their packets with the assistance of the secondary users (SUs) by offering them spectrum resources. This paper first raises issues in existing works, such as non-optimal selection, selection collision, and transmission interruption. Aiming at these issues, we design a centralized system model and a cooperative relaying protocol for multiple primary user pairs to dynamically lease spectrum in exchange for the transmission assistance of SUs. Then we define 2 problems of the cooperative SU assignment to maximize total rate and maximize number of assigned SUs. We prove they are NP-hard and propose a local search algorithm for the objective of maximize total rate and a 1/2 approximation algorithm for another objective. Our simulation results show that our system and algorithms can effectively improve the performance of the wireless networks. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the analytical performance of the multiple-input multiple-output system(MIMO) with orthogonal space-time block codes (STBCs) subject to Weibull fading channels (WFC). Space-time block code technique provides an efficient pattern for wireless transmission over various fading channels using multiple transmit antennas. Two approximating methods of the sum of independent Weibull randomvariables are studied. For each approach, we derive accurate approximate expressions for several performance metrics of MIMOSTBC system operating under independent and nonidenticalWFC. The proposed approximations are expressed in terms of 2 generalized hypergeometric functions, namely, Fox's H and Meijer's G functions. All the derived approximate expressions prove high accuracy, while compared with the simulation results established via Monte Carlo method and Kolmogorov-Smirnov test as well. Although the 2 approaches have approximately the same accuracy, the second method approximate expressions are much less complex than those of the first method. [ABSTRACT FROM AUTHOR]

Unequal error protection systems are a popular technique for video streaming. Forward error correction (FEC) is one of error control techniques to improve the quality of video streaming over lossy channels. Moreover, frame-level FEC techniques have been proposed for video streaming because of different priority video frames within the transmission rate constraint on a Bernoulli channel. However, various communication and storage systems are likely corrupted by bursts of noise in the current wireless behavior. If the burst losses go beyond the protection capacity of FEC, the efficacy of FEC can be degraded. Therefore, our proposed model allows an assessment of the perceived quality of H.264/AVC video streaming over bursty channels, and is validated by simulation experiments on the NS-2 network simulator at a given estimate of the packet loss ratio and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide a more accurate evaluation tool for video streaming over bursty channels and help to evaluate the impact of FEC performance on different burst-loss parameters. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In space shift keying (SSK), all information bits are transmitted by antenna indices rather than transmitting symbols. To obtain high spectral efficiency, exponentially increasing number of antennas is used, which is generally not practical. Less number of antennas can only be possible by using more than one active antenna, such as generalized SSK, but this type of solutions result in excessive degradation in bit error ratio in correlated channels. In this study, variable number of active antennas for each codeword is proposed and called variable antenna-SSK. First of all, pairwise error probability is obtained for variable number of antennas in the case of correlated channels. Then, to reduce the correlation effect, a novel antenna codeword construction method that minimizes the pairwise error probability is introduced for exponentially correlated channels. Codeword sets are obtained for k = 3 and 8 bits/s/Hz for 7 and 13 transmit antennas. Simulation results show that variable antenna-SSK gets better performance according to its counterparts with increasing effect of correlation. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, the performance analysis based on PDF approach of an L-branch equal gain combiner (EGC) over independent and not necessarily identical Weibull fading channels is presented. Several closed-form approximate expressions are derived in terms of only one Fox H-function as PDF, cumulative distribution function, and moments of the EGC output Signal-to-noise ratio (SNR), outage probability, amount of fading, channel capacity, and the average symbol error rate for various digital modulation schemes. All results are illustrated and verified by simulations using computer algebra systems. [ABSTRACT FROM AUTHOR]

Since the concept of the multiuser multiple input multiple output (MU-MIMO) system has been introduced for enhancement of capacity and flexibility, it has been accepted in various wireless standards. To enjoy the benefits of the MU-MIMO system, full or partial channel information is necessary at the transmitter, but how to use the full or partial feedback information in the practical system perspective has not been investigated well. In this paper, we analyze the interference of full usage concurrent transmission codebook based on the MU-MIMO systems and also investigate the usage of channel information for a codebook based scheme and a zero-forcing beamforming (ZFBF) scheme. Based on the analytic results, we propose two adaptive schemes for the practical usage perspective in MU-MIMO-OFDM systems. Firstly, we propose an adjustable uplink channel sounding scheme, which depends on the number of users in a given cell/sector in frequency division duplexing system, with ZFBF MU-MIMO-OFDM systems. Secondly, we propose an adaptive switching scheme, which depends on signal-to-noise ratio, between the codebook based scheme and the ZFBF scheme. The performance of the proposed scheme is evaluated with computer simulations, and the simulation results show that the proposed scheme provides the enhanced throughput over entire signal-to-noise-ratio regions. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Diffusion-based communication is one of the most dominating forms in the micrometer and nanoscale communications. Generally, information is coded in molecules that are released by a transmitter nanomachine, propagated via a diffusion-based channel, and then received by a receiving nanomachine (called receiver). The receiver considered in this paper is equipped with multiple ligand receptors. The molecular communication system in this paper is single hop and SISO. Namely, there is only a channel connecting a pair of transmitter and receiver. While most literature considers either the channel or the receptors, this paper proposes a channel model that takes into account both the diffusion-based channel and the ligand-based receiver. The channel capacity under such model is analyzed, which studies the impact of different parameters at both channel and the receiver on the performance of the molecular communication system. We establish a digital channel model based on the on-off keying and time slot scheme. A capacity expression is derived with consideration of the effects of the channel memory and ligand-receptor binding mechanisms. The numerical results show that the overall channel capacity is restricted by the physical parameters of diffusion channel and ligand receptors. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, we consider a cooperative relay scheme for a mobile network with MIMO technology. The channel capacity for two well-known relaying schemes are investigated: analogue relaying (amplify and forward) and digital relaying (decode and forward) from a mobile device to the base station through a relay node. In order to further increase the channel capacity, we propose an efficient hierarchical procedure based on support vector machine, namely hierarchical support vector machines (HSVM), to estimate the wireless networks condition approximately and design two ways (matched filter and minimum mean square error filter) of increasing the channel capacity according to the estimated wireless network condition. The proposed HSVM can estimate the wireless networks condition in much shorter time compared with the traditional minimum mean square error scheme without incurring much estimation error, which is spatial, useful for delay sensitive communication. For digital relaying, the effect of imperfect channel decode is also addressed. Our numerical results demonstrate the reduction of estimation complexity by adopting HSVM and the significant improvement of network capacity by applying the matched filter weight at relay nodes according to the network estimation. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Cooperative diversity systems have recently been proposed as a way to form virtual antenna schemes without utilizing collocated multiple antennas. In this paper, we consider the Nth best opportunistic amplify-and-forward (AF) cooperative diversity systems. The AF type can be regarded as one on the basis of modified channel state information. Wireless channels between any pair of nodes (i.e., direct and dual hop links) are assumed quasi-static independent and nonidentically distributed (INID) Rayleigh fading. The best opportunistic AF (OAF) scheme requires two phases of transmission. During the first phase, the source node transmits a signal to all relays and the destination. In the second phase, the best relay is only selected on the basis of highest signal-to-noise ratio (SNR) scheme to forward the source signal to the destination. Therefore, the indirect link (i.e., source-selected relay destination) can give the highest received SNR. However, the best relay selection cannot be available so that we might choose the second, third, or generally the Nth best relay. In this paper, we derive the approximated outage probability and channel capacity for the Nth best OAF relay systems over INID Rayleigh fading channels. At first, the indirect link's received SNR is approximated as harmonic mean upper bound. With this information, we obtain the given relay's Nth best selection probability as the closed form. Finally, both outage probability and channel capacity are derived as the closed forms. Simulation results are finally presented to validate the analysis. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The theoretically achievable average channel capacity (in the Shannon sense) per user of a hybrid cellular direct sequence/fast frequency hopping code-division multiple-access (DS/FFH-CDMA) system, operating in a Rayleigh fading environment, was examined. The analysis covers the downlink transmission and leads to the derivation of a novel expression between the average channel capacity available to each system's user under simultaneous optimal power and rate adaptation and the system's parameters, providing an optimistic upper bound, useful for practical modulation and coding schemes. The final derived closed-form expression can be useful for the design of the DS/FFH-CDMA system because it provides a theoretical tool for the initial quantitative analysis. Finally, avoiding the application of complex theoretical algorithm or lengthy simulation, we theoretically derived numerical results to illustrate the presented analysis. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The CDMA system can provide more capacity than the conventional AMPS system and the hierarchical layer of cells is required for system design in the future. However, the problem is whether the same RF channels used in a CDMA underlaying macrocell/microcell structure also obtain high capacity as in the homogeneous structure. This paper investigates the interference of uplink and downlink from both the microcell and macrocell in a hierarchical structure. Downlink power control is also considered. The results show that the capacity of microcell in a hierarchical structure is 23 per cent less than in homogeneous cells. The capacity of macrocell in a hierarchical structure decreases dramatically in proportion to the number of microcells. The capacities of the microcell and macrocell are limited in downlink, and uplink, respectively. In addition, more efforts for microcell should be made, such as more power is transmitted by microcell basestation if the same RF channel is used in a hierarchical structure. The results suggest that different RF channels are used in a two-tier cellular environment. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]