Modern Wireless Communication Systems Research Articles

A Triple-band Suspended Microstrip Antenna with Symmetrical USlots for WLAN/WiMax Applications

In this study, a triple-band suspended microstrip antenna with symmetrical U-slots is proposed for modern wireless communication systems. The antenna is specifically designed to acquire application in WLAN and WiMAX communication. Symmetrical U-slots in the radiator patch increase the number of resonances and improve the gain response. An appropriate air height was maintained between the ground plane and the radiator patch layer for improving bandwidth operation. The impedance characteristics of the antenna are enhanced using probe feeding techniques. The proposed compact antenna is designed on a single dielectric substrate of (30×25×1.56) mm3 . Parametric analysis of the proposed structure has been realized using IE3D software. This prototype exhibits maximum impedance bandwidth of 750 MHz and gain response of 7.28 dBi. The performance of the structure at three resonating bands i.e., at 3.3 GHz, 3.78 GHz and 5.3 GHz facilitate it to be applicable for WLAN/WiMAX systems.

Miniaturized quad-channel microstrip diplexer with low insertion loss and wide stopband for multi-service wireless communication systems

In this paper, a compact four-channel diplexer is designed using a microstrip structure to separate input signals at 2.07/3.94 GHz and 2.37/4.49 GHz and load them on two output ports. The presented diplexer is designed utilizing a novel structure, which can be applied in modern multi-band wireless communication systems and IEEE 802.16 WiMAX that covers 3.17–4.2 GHz. This diplexer is consisting of coupled lines, a spiral cell and U-shape structures that are integrated to obtain a high performance. To create four passbands at two output ports, the proposed structure is miniaturized so that it occupies only a 0.025 λ g 2 circuit size where λg is the guided wavelength calculated at 2.07 GHz. Moreover, the low insertion losses are obtained at all channels. Another achievement of this work is obtaining a wide stopband. After the last passband, harmonics are attenuated up to 8 GHz, which is suitable for ultra wideband applications. The introduced diplexer is fabricated to confirm the design process where the measured results are in a good agreement with the simulations.

Comparative Analysis of E–Shape and H-Shape Microstrip Slotted Antenna on the Basis of Return Loss and Bandwidth

<p>icro-strip patch antenna is more popular as compared to other antennas and widely used today in modern wireless communication system because of its elegant weight, low fabrication price, easy to feed, ease to fabricate, easy to analyze, and attractive radiation characteristics. Though patch antenna<br />has several advantages but has some disadvantages as well, like limited bandwidth and low gain. In last few years, Different techniques such as Electromagnetic Band Gap (EBG) structure, artificial magnetic conductor (AMC)/ and modifying the structure of microstrip patch antenna are used to overcome the above mentioned limitations. In this paper, we propose two different geometry shape antennas i.e. E and H-shaped which is developed from the rectangular patch and compare the performance of the proposed antennas on the basis of gain and Bandwidth with the same physical dimensions. The CST Micro studio simulator is used to study the antennas. Bandwidth and Return loss of E-shaped Antenna is much better than that of H-shaped antenna. The results obtained clearly demonstrations that, the implementation of the E-Shape is much better in term of bandwidth and return loss compared to the H-shaped patch antenna. So it’s better to use E-shaped antenna for modern wireless communication system.</p>

Performance and Improvement of Antenna Designs in Modern Wireless Communication System

In this paper, the cell innovation and the remote correspondence innovation is creating and enhancing quickly. The reception apparatus goes about as the scaffold between the client terminal and the base station controller. Being a key segment of the remote correspondence framework, the reception apparatus’ fundamental capacity is to communicate and to get electromagnetic waves. It will, to an expansive degree, influence the quality and the speed of the correspondence. With the advancing of the reception apparatus innovation, the versatile terminal gadgets have developed from the unique specialized devices to exceptionally intellectualized types of gear. The imparted content was likewise expanded, as there are presently FM programs, TV shows and web. All these, be that as it may, conveys requesting benchmarks to the reception apparatus. For instance, it requires a considerably higher data transmission and best exhibitions from the reception apparatus to help the complex applications and correspondence capacity of the versatile terminals. Furthermore, the correspondence system’s convenient terminal has almost bolted the position of the recieving wire, which requests that the span of the radio wire must be downscaled. The control of the wave speed, shape and its directivity can be typically streamlined by enhancing the radiation qualities of the recieving wires, which will help the general execution of a framework. In along these lines, additionally enhanced are the channel limit and the recurrence use proportion. This paper, starting with the presentation of the improvement status of the remote correspondence framework and the radio wires, contemplates a portion of the plans of new reception apparatuses. With that review, this paper likewise breaks down the advancement heading fitting to current correspondence framework and the important gadgets, and in addition the structure adjustment and pattern of reception apparatuses.

A Novel Two-Stage Broadband Doherty Power Amplifier for Wireless Applications

Broadband and highly efficient amplifiers are of great interest in modern wireless communication systems. In this paper, we present a novel two-stage broadband Doherty power amplifier (DPA), which is able to maintain high efficiency at saturated output power and at backoff output power levels over a wide bandwidth. The amplifier uses a novel and simple approach to achieve bandwidth enhancement and at the same time uses a driver amplifier. We employ Klopfenstein taper to deliver wide bandwidth. The measurement results show that the proposed broadband two-stage DPA is able to deliver 31%-35% drain efficiency at 6-dB output power backoff while at the saturation it achieves 40%-55% drain efficiency over the designed bandwidth of 1.5 to 2.6 GHz. The amplifier can deliver above 35-dBm output power with substantial gain of around 20 dB. The proposed DPA is a promising candidate for wideband and high gain requirements in modern wireless systems.

Noise Power Estimators in ISM Radio Environments: Performance Comparison and Enhancement Using a Novel Samples Separation Technique

Noise power estimation is central to efficient radio resource allocation in modern wireless communication systems. In the literature, there exist many noise power estimation methods that can be classified based on underlying theoretical principle; the most common are spectral averaging, eigenvalues of sample covariance matrix, information theory, and statistical signal analysis. However, how these estimation methods compare against each other in terms of accuracy, stability, and complexity is not well studied, and the focus instead remains on the enhancement of individual methods. In this paper, we adopt a common simulation methodology to perform a detailed performance evaluation of the prominent estimation techniques. The basis of our comparison is the signal-to-noise ratio estimation in the simulated industrial, scientific and medical band transmission, while the reference noise signal is acquired from an industrial production plant using a software-defined radio platform, USRP-2932. In addition, we analyze the impact of different techniques for noise-samples’ separation on the estimation process. As a response to defects in the existing techniques, we propose a novel noise-samples’ separation algorithm based on the adaptation of rank-order filtering. Our analysis shows that the proposed solution, apart from its low complexity, has a very good root-mean-squared error of 0.5 dB and smaller than 0.1-dB resolution, thus achieving a performance comparable with the methods exploiting information theory concepts.

Secure minimum loss route selection of MIMO-based MANET in combined (indoor, outdoor, and forest) terrain

Multiple-input multiple-output (MIMO) system is a very promising technique in modern wireless communication systems, which can meet the demand of high data rate with limited bandwidth. Integration of MIMO technology with mobile ad hoc network can improve the performance of transmission process in hazardous environment. In order to design a real MIMO wireless system and predict its performance under certain circumstances, it is necessary to have accurate MIMO wireless channel models for different scenarios. Mobile ad hoc network with multiple antennas suffers scattering effects. A combination of two ring model and random scattering model is described in this paper to evaluate channel impulse response of the network. Channel impulse response or channel matrix is used to estimate the propagation loss of the MIMO-based mobile ad hoc network in different terrain. Finally, a minimum loss secure path selection is described here using path loss-based administrator selection secure routing protocol (PASR) protocol to select loss less secure route for transmission.

A 1.8-3.8-GHz Power Amplifier With 40% Efficiency at 8-dB Power Back-Off

This paper presents a novel power combining architecture, referred to as distributed efficient power amplifier (DEPA) that mitigates the inherent bandwidth limiting factors in a Doherty power amplifier (DPA), namely, impedance inversion and load modulation, by distributing the conventional auxiliary amplifier of the DPA to multiple auxiliary subamplifiers along a broadband multisection impedance transformer. The proposed technique is demonstrated through the design, implementation, and measurement of a wideband DEPA having 8-dB output power back-off and 72% fractional bandwidth. The experimental results show a Doherty-like efficiency enhancement from 1.8 to 3.8 GHz. For the output power levels of 37.4±1.1 and 45.4±1.1 dBm, corresponding to 8-dB OBO and peak output power, the efficiency levels are between 41%-51% and 42%-62%, respectively. Furthermore, linearized modulated measurements show that the DEPA is linearizable and meets the spectral requirements for modern wireless communication systems.

Single‐layer dual‐broadband circularly polarised annular‐slot antenna for WLAN applications

This study proposes a single-layer dual-broadband circularly polarised (CP) antenna that operates at 2.4, 5.2 and 5.8 GHz for wireless local area networks (WLAN) applications. An annular-slot antenna loaded with a lightning-shaped slot for achieving good CP radiation in the WLAN 2.4 GHz band is initially studied. To cover the WLAN 5.2 GHz band as well, the inner circular patch of the aforementioned design is modified as an inner ring patch loaded with a notch and a narrow U-shaped strip. By further embedding a crescent parasitic element into the circular slot of the inner ring patch, the upper CP band is significantly broadened to cover the WLAN 5.8 GHz. Accordingly, the final design can exhibit two wide 3 dB axial ratio bands of 13.3% (2.24-2.56 GHz) and 16.9% (5.01-5.94 GHz), and their corresponding 10 dB impedance bandwidths are 25.9% (2.21-2.86 GHz) and 25.9% (5.05-6.54 GHz). With the advantages of compact size, low-cost, easy integration and dual-broad CP bands, the proposed designs are very attractive for modern wireless communication systems, especially for WLAN applications.

A Wideband Tunable Reflection-Type Phase Shifter With Wide Relative Phase Shift

Wide bandwidth, wide tunable phase range, and a compact circuit size are always desired for the tunable phase shifter utilized in the modern wireless communication system. However, the existing reflection-type phase shifter configurations cannot satisfy all these requirements simultaneously. To resolve these problems, the reflection load consisting of two tunable capacitors and a quarter wavelength transmission line is utilized on a vertically installed planar structure to implement a new reflection-type phase shifter. For demonstration, a reflection-type phase shifter is designed, fabricated, and measured. A wide bandwidth of 66.7% defined by 10-dB return loss had been achieved. Over the same band, a wide phase shift range up to 407° can be observed. Meanwhile, the fabricated circuit occupies a compact circuit size of ${0.26\lambda _{g} *0.37\lambda _{g}}$ .

Hardware-Efficient QR-Decomposition Using Bivariate Numeric Function Approximation

Bivariate function approximation has proven its feasibility in terms of hardware-efficient arithmetic signal processing. However, its impact on high performance QR decomposition (QRD) has only been roughly studied so far. In this paper, a novel hardware architecture for Givens-Rotation-based QRD is proposed targeting hardware efficient signal processing. To this end, an ingenious triangular systolic array structure is considered. Complex-valued matrices are efficiently processed by means of a sophisticated bivariate numeric function approximation methodology. In order to get a comprehensive insight in the performance, exhaustive evaluation is carried out with a modern multi-antenna wireless communication system. In detail, the proposed QRD hardware architecture is used in a suitable channel pre-coding setup. For a meaningful proof-of-concept, our work is evaluated on several levels of the computing stack. In addition, our design is implemented and physically synthesized in a state-of-the-art 65-nm Taiwan Semiconductor Manufacturing Company technology and compared with other publications. The results indicate our approach to be a powerful solution for hardware-based QRD, especially in terms of energy and area requirements.

Mathematical Derivation of MIMO Based MANET to Improve the Network Performance

The proliferations of research activities in wireless communication stimulated researchers to develop a new technology and a technique to enable efficient and purposeful application in mobile ad hoc network. This new technique was developed by invention of MIMO technology and its tremendous potential in wireless network. The advantage of MIMO technology is it’s high data rate and improved transmission efficiency in ad hoc network, wireless communication, IEEE 802.11n (Wi-Fi) and IEEE 802.16e (WiMAX) standards. Mobile ad hoc network (MANET) has several significant applications in infrastructure-less wireless network. MIMO technology has played a key role to improve the transmission efficiency in MANET. Mobile ad hoc network (MANET) and Multiple Input Multiple Output (MIMO) communication both are very emerging in modern wireless communication system. Main focus of this research work is to improve the spectral efficiency of the MANET. MANET and MIMO communication are studied separately to analyze the performance of these networks. Analysis of this work can further help to implement an integrated network or MIMO based mobile ad hoc network. And finally analysis the performance of the integrated network (MIMO-MANET) to improve the spectral efficiency.

Optimised periodic precoder-based blind channel estimation for MIMO-OFDM systems

ABSTRACTIn modern wireless communication systems, multiple antennas at transmitter and receiver are employed along with orthogonal frequency-division multiplexing to achieve very high data rate with significant system reliability. To further enhance system performance, blind channel estimation techniques are employed whenever data symbols are transmitted in blocks. These estimation techniques are computationally expensive at almost all signal-to-noise ratio values. In this paper, periodic precoder-based blind channel estimation is used to tackle problems like complexity, channel order overestimation and bandwidth expansion. The system reliability can be improved, if precoder coefficients are chosen in such a way that they have no dependency or minimum correlation with noise coefficients. The overall bit error rate (BER) is derived and simulated with dependency on periodic sequence and channel estimation error. The simulation results shows that the presented precoding scheme performs better in terms of BER with minimum channel estimation error as compared to other state-of-the-art schemes.

Compact and broadband antenna based on a step-shaped metasurface.

A metasurface (MS) is highly useful for improving the performance of patch antennae and reducing their size due to their inherent and unique electromagnetic properties. In this paper, a compact and broadband antenna based on a step-shaped metasurface (SMS) at an operating frequency of 4.3 GHz is presented, which is fed by a planar monopole and enabled by selecting an SMS with high selectivity. The SMS consists of an array of metallic step-shaped unit cells underneath the monopole, which provide footprint miniaturization and bandwidth expansion. Numerical results show that the SMS-based antenna with a maximum size of 0.42λ02 (where λ0 is the operating wavelength in free space) exhibits a 22.3% impedance bandwidth (S11 < -10 dB) and a high gain of more than 7.15 dBi within the passband. Experimental results at microwave frequencies verify the performance of the proposed antenna, demonstrating substantial consistency with the simulation results. The compact and broadband antenna therefore predicts numerous potential applications within modern wireless communication systems.

Enhancing BER Performance Limit of BCH and RS Codes Using Multipath Diversity

Modern wireless communication systems suffer from phase shifting and, more importantly, from interference caused by multipath propagation. Multipath propagation results in an antenna receiving two or more copies of the signal sequence sent from the same source but that has been delivered via different paths. Multipath components are treated as redundant copies of the original data sequence and are used to improve the performance of forward error correction (FEC) codes without extra redundancy, in order to improve data transmission reliability and increase the bit rate over the wireless communication channel. For a proof of concept Bose, Ray-Chaudhuri, and Hocquenghem (BCH) and Reed-Solomon (RS) codes have been used for FEC to compare their bit error rate (BER) performances. The results showed that the wireless multipath components significantly improve the performance of FEC. Furthermore, FEC codes with low error correction capability and employing the multipath phenomenon are enhanced to perform better than FEC codes which have a bit higher error correction capability and did not utilise the multipath. Consequently, the bit rate is increased, and communication reliability is improved without extra redundancy.

Rate Adaptive Hybrid ARQ With Optimal Spectral Efficiency and Delay Tradeoff

Hybrid automatic repeat request (HARQ) is widely used in modern wireless communication systems to improve the spectral efficiency. However, the spectral efficiency improvement is at the cost of increased transmission delay. In this paper, we first show that the gap between spectral efficiency of conventional HARQ and ergodic channel capacity diminishes as $\frac {1}{D}$ , where $D$ is the average delay of HARQ. It is then shown that rate optimized HARQ, which allows static resource allocation of each HARQ transmission, is capable of achieving marginally better spectral efficiency and delay tradeoff performance. We then consider rate adaptive HARQ, which allows dynamic resource allocation based on outdated CSI feedback information from the receiver. Under the assumption of the cumulative distribution function of the fading channel capacity being a power function, spectral efficiency of simple linear stationary policy converges to the ergodic channel capacity at order of $\frac {1}{D^{2}}$ . For a wide class of policies, the spectral efficiency can converge to ergodic channel capacity at order of $e^{-D}$ . The optimal policy can be found in a simple explicit form sequentially by a greedy algorithm. Simulation results show that it achieves significantly higher spectral efficiency than other existing schemes with the same average delay.

Secret Key Agreement: Fundamental Limits and Practical Challenges

Despite the tremendous progress made toward establishing PLS as a new paradigm to guarantee security of communication systems at the physical layer, there is a common belief among researchers and industrials that there are many practical challenges that prevent PLS from flourishing at the industrial scale. Most secure message transmission constructions available to date are tied to strong assumptions on CSI, consider simple channel models and undermine eavesdropping capabilities; thus compromising their practical interest to a big extent. Perhaps arguably, the most likely reasonable way to leverage PLS potential in securing modern wireless communication systems is via secret-key agreement. In the latter setting, the legitimate parties try to agree on a key exploiting availability of a public channel with high capacity which is also accessible to the eavesdropper. Once a key is shared by the legitimate parties, they may use it in a one-time pad encryption, for instance. In this article, we investigate two performance limits of secret-key agreement communications; namely, the secret-key diversity-multiplexing trade-off and the effect of transmit correlation on the secretkey capacity. We show via examples how secretkey agreement offers more flexibility than secure message transmissions. Finally, we explore a few challenges of secret-key agreement concept and propose a few guidelines to overturn them.

Design of a Novel Wideband High Efficiency CCF PA

In this article, a novel approach for the design of broadband high-efficiency power amplifiers (BHPAs) is presented. The method is to simplify the process of synthesizing a wideband output matching network by realizing harmonic tuning and fundamental matching separately. First, the second and third harmonic load impedances are calculated based on the theory of Continuous Class-F Mode. Then, a novel wideband harmonic-suppressing network is obtained by using microstrip radial stubs which is not affected by the adjacent fundamental matching circuit. The proposed PA using a 10-W Cree GaN HEMT device achieves a measured result of a fractional bandwidth of 30.4% from 1.95 to 2.65 GHz, with 60.9–81.6% drain efficiency, 60–79.9% PAE and 39.7–41.7 dBm output power throughout the operating band. As shown in the design process, simulated analyses and measured results, the proposed idea makes the design of the harmonic load network much easier and more accurate. It is generally more feasible, compared with some of the existing methods which are difficult to realize the fundamental and harmonic wave controlling at the same time, especially at higher frequencies. And this method can be widely applied in the BHPA design and modern wireless communication systems.

Generation of Long Perfect Gaussian Integer Sequences

Recently, the perfect Gaussian integer sequences have been widely used in modern wireless communication systems, such as code division multiple access and orthogonal frequency-division multiplexing systems. This letter presents two different methods to generate the long perfect Gaussian integer sequences with ideal periodic auto-correlation functions. The key idea of the proposed methods is to use a short perfect Gaussian integer sequence together with the polynomial or trace computation over an extension field to construct a family of the long perfect Gaussian integer sequences. The period of the resulting long sequences is not a multiple of that of the short sequence, which has not been investigated so far. Compared with the already existing methods, the proposed methods have three significant advantages that a single short perfect Gaussian integer sequence is employed, the long sequences consist of two distinct Gaussian integers, and their energy efficiency is monotone increasing.

Design of Wideband PBG Antenna for New Generation Communication Systems through Simulation

In modern wireless communication system, demand of high bandwidth antennas with low cost are increased. In proposed paper, these requirements have been fully justified by using PBG based wideband antenna. Although, metamaterial is one more option to build this idea, sometimes, negative permittivity or negative permeability or both does not permit to allow easy fabrication and maintaining low cost. An antenna with several periodic rods and organic magnetic materials substrate made it possible to enhance the bandwidth and think off using it for 5G communication systems. Proposed antenna is designed and fabricated for frequency range of 40 GHz - 50 GHz, and 12 × 9 periodic rods with substrate having organic magnetic materials property. Antenna is designed and analyzed using commercial simulation software CST microwave studio (CST STUDIO SUITE 2014) and measured for return loss and VSWR for fabricated design. Obtained results meet the requirement of wider bandwidth of 1.5 - 2 GHz and return loss, ?35 dB, and directivity is 61 dBi with efficiency of 61%.