This paper presents a new design to obtain wide dual-band operation from a coplanar probe feed antenna loaded with two shorted walls. The lower band of proposed antenna has a 10 dB bandwidth of 611 MHz (24.18%) around the center frequency 2527MHz, and the upper band has a bandwidth of 1255 MHz (27.88%) around the center frequency 4501MHz. The obtained bandwidths cover WLANs operations on all bands. The bandwidth of the first operating frequency covers ISM band (2400- 2483.5) MHz, which is required by IEEE 802.11b, g and Bluetooth standards, and the bandwidth of the second operating frequency covers U-NII1 (5150-5350) MHz band, which is required by IEEE 802.11a and HiperLAN2 standards, and also covers U-NII2 (5470-5725) MHz and U-NII3/ISM (5725-5825) MHz bands, which are required by IEEE 802.11a standard. A three dimensional finite-difference time-domain (3-D FDTD) method is employed to analyze the proposed structure and find its performance. The simulated results are compared with the experimental results.
In this paper, the effect of the grating parameters (i.e. gratings length (Lg) and the induced index profile (Δn)); the temperature variation (T) and the applied strain change on the fiber Bragg Grating (FBG) 3dB-bandwidth (i.e. full width-half maximum (FWHM)) have successfully investigated numerically using MATHCAD software. Results show that for Lg < 7 mm, the FBG 3dB-bandwidth (i.e. full width-half maximum (FWHM)) value shows a good reliable and visible impact. Otherwise, there are no significant effects except for increasing the FBG reflectivity. Also, results show that the FWHM value has affected by the change of the Δn value. In contrast, results show that there is no significant effect of the temperature on the FWHM value. Also, results shown that the dependence of the Bragg wavelength (λB) upon both strain and temperature variations is lies within the range of 0.462 – 0.470 fm με-1 °C-1
This paper presents a new design of the filtering antenna with a quasi-elliptic function response. The basic structure of the proposed filtering antenna is consists of a four-folded arms open-loop resonator (OLR). The proposed filtering antenna is simulated, improved and, analyzed by using 3D Computer Simulation Technology (CST) electromagnetic simulator software. The design has good spurious harmonic suppression in the upper and lower stopbands. The Insertion Loss of the proposed filtering antenna IL=0.2 dB and the Return Loss RL= -25.788 dB at the center frequency fo=5.75 GHz. The passband bandwidth which is relatively wide, and equal to 0.793 GHz. The microstrip filtering antenna circuit shows good design results compared to the conventional microstrip patch antenna. The filtering antenna design circuit with etched ground plane structure also has good design results compared to the filtering antenna design which has a complete ground plane structure.
Beam squint phenomenon is considered one of the most drawbacks that limit the use of (mm-waves) array antennas; which causes significant degradation in the BER of the system. In this paper, a uniform linear array (ULA) system is exemplified at millimeter (mm-waves) frequency bands to realize the effects of beam squint phenomena from different directions on an equivalent gain response to represent the channel performance in terms of bit error rate (BER). A simple QPSK passband signal model is developed and tested according to the proposed antenna array with beam squint. The computed results show that increasing the passband bandwidth and the number of antenna elements, have a significant degradation in BER at the receiver when the magnitude and phase errors caused by the beam squint at 26 GHz with various spectrum bandwidths.
The thermal dependence of the spectral response (i.e. transmission, reflection and time delay ( τ r ) responses) of uniform polymer optical fiber (POF) Bragg gratings has been investigated. In addition to the temperature dependence, the effects of grating strength (kL g ) and fiber index modulation ( ∆ n) have been investigated. Besides high capability of tunable wavelength due to the unique large and negative thermo-optic coefficient of POF, the spectral response for POF Bragg gratings show high stability and larger spectrum bandwidth with temperature variation compare with the silica optical fiber (SOF) Bragg gratings, especially with the increase of the kL g value. It was found that by increasing kL g , the peak reflectance value increases and the bandwidth of the Bragg reflector become narrower. Also it’s shown by increasing the kL g value, τ r deceasing significantly and reach its minimum value at the designed wavelength ( λ B ). Furthermore, the τ r for POF Bragg gratings is less than that for SOF Bragg gratings at the same value of kL g . Also it’s found that the peak reflectivity value increases to around 60% when the ∆ n value increases from 1 ˣ 10 -4 to 5 ˣ 10 -4 .
Wireless sensor networks have many limitations such as power, bandwidth, and memory, which make the routing process very complicated. In this research, a wireless sensor network containing three moving sink nodes is studied according to four network scenarios. These scenarios differ in the number of sensor nodes in the network. The RPL (Routing Protocol for low power and lossy network) protocol was chosen as the actual routing protocol for the network based on some routing standards by using the Wsnet emulator. This research aims to increase the life of the network by varying the number of nodes forming it. By using different primitive energy of these nodes, this gives the network to continue working for the longest possible period with low and fair energy consumption between the nodes. In this work, the protocol was modified to make the sink node move to a specific node according to the node’s weight, which depends on the number of neighbors of this node, the number of hops from this node to the sink node, the remaining energy in this node, and the number of packets generated in this node. The simulation process of the RPL protocol showed good results and lower energy consumption compared to previous researches.
In this paper, a semi-elliptical annular slot loaded trapezoidal dipole antenna with band-notched characteristics for UWB applications is designed. A microstrip feedline consisting of multiple feedline sections is used for improving the impedance matching. The band-notched characteristics for WLAN band are achieved by loading the trapezoidal dipole arms with semi- elliptical annular slots. The designed antenna structure has an operating range from 3.5-12.4 GHz(109%) with band-rejection in the frequency range of 5-6 GHz. Nearly omnidirectional patterns are achieved for the designed antenna structure. The designed antenna structure provided an average peak gain of 2.12 dB over the entire frequency range except in the notched band where it reduced to -2.4 dB. The experimental and simulation results are observed to be in good agreement. An improved bandwidth performance with miniaturized dimensions as compared to earlier reported antenna structures is achieved.
This paper proposes a new design of compact coplanar waveguide (CPW) fed -super ultra-wideband (S-UWB) MIMO antenna with a bandwidth of 3.6 to 40 GHz. The proposed antenna is composed of two orthogonal sector-shape monopoles (SSM) antenna elements to perform polarization diversity. In addition, a matched L-shaped common ground element is attached for more efficient coupling. The FR-4 substrate of the structure with a size of 23 × 45 × 1.6 mm3 and a dielectric constant of 4.3 is considered. The proposed design is simulated by using CST Microwave Studio commercial software. The simulation shows that the antenna has low mutual coupling (|S21| < -20 dB) with |S11|<−10 dB, ranging from 3.6 to 40 GHz. Envelope correlation coefficient (ECC) is less than 0.008, diversity gain (DG) is more than 9.99, mean effective gain (MEG) is below - 3 dB and total active reflection coefficient (TARC) is less than -6 dB over the whole response band is reported. The proposed MIMO antenna is expected efficiently cover the broadest range of frequencies for contemporary communications applications.
In this paper, a compact two-element cylindrical dielectric resonator antenna (CDRA) array with corporate feeding is proposed for X-band applications. The dielectric resonator antenna (DRA) array is excited by a microstrip feeder using an efficient aperture-coupled method. The designed array antenna is analyzed using a CST microwave studio. The fabricated sample of the proposed CDRA antenna array showed bandwidth extending from 10.42GHz to 12.84GHz (20.8%). The achieved array gain has a maximum of 9.29dB i at frequency of 10.7GHz. This is about 2.06dB i enhancement of the gain in comparison with a single pellet CDRA. The size of the whole antenna structure is about 50 50mm 2 .
In this paper, a new compact coplanar antenna used for Radio frequency identification (FID) applications is presented. This antenna is operated at the resonant frequency of 2.45 GHz. The proposed antenna is designed on an epoxy substrate material type (FR-4) with small size of (40 × 28) mm2 in which the dielectric thickness (h) of 1.6 mm, relative permittivity (er) of 4.3 and tangent loss of 0.025. In this design the return loss is less than −10 dB in the frequency interval (2.12 − 2.84) GHz and the minimum value of return loss is -32 dB at resonant frequency. The maximum gain of the proposed antenna is 1.22 dB and the maximum directivity obtained is 2.27 dB. The patch and the ground plane of the proposed antenna are in the same surface. The proposed antenna has a wide bandwidth and omnidirectional radiation pattern with small size. The overall size of the compact antenna is (40 × 28 × 1.635) mm3. The Computer Simulation Technology (CST) microwave studio software is used for simulation and gets layout design.
Wavelet-based algorithms are increasingly used in the source coding of remote sensing, satellite and other geospatial imagery. At the same time, wavelet-based coding applications are also increased in robust communication and network transmission of images. Although wireless multimedia sensors are widely used to deliver multimedia content due to the availability of inexpensive CMOS cameras, their computational and memory resources are still typically very limited. It is known that allowing a low-cost camera sensor node with limited RAM size to perform a multi-level wavelet transform, will in return limit the size of the acquired image. Recently, fractional wavelet filter technique became an interesting solution to reduce communication energy and wireless bandwidth, for resource-constrained devices (e.g. digital cameras). The reduction in the required memory in these fractional wavelet transforms is achieved at the expense of the image quality. In this paper, an adaptive fractional artifacts reduction approach is proposed for efficient filtering operations according to the desired compromise between the effectiveness of artifact reduction and algorithm simplicity using some local image features to reduce boundaries artifacts caused by fractional wavelet. Applying such technique on different types of images with different sizes using CDF 9/7 wavelet filters results in a good performance.
Cryptography is one of the technological means to provide security to data being transmitted on information and communication systems. When it is necessary to securely transmit data in limited bandwidth, both compression and encryption must be performed. Researchers have combined compression and encryption together to reduce the overall processing time. In this paper, new partial encryption schemes are proposed to encrypt only part of the compressed image. Soft and hard threshold compression methods are used in the compression step and the Advanced Encryption Standard (AES) cipher is used for the encryption step. The effect of different threshold values on the performance of the proposed schemes are studied. The proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of the underlying selected compression methods.
In different modern and future wireless communication networks, a large number of low-power user equipment (UE) devices like Internet of Things, sensor terminals, and smart modules have to be supported over constrained power and bandwidth resources. Therefore, wireless-powered communication (WPC) is considered a promising technology for varied applications in which the energy harvesting (EH) from radio frequency radiations is exploited for data transmission. This requires efficient resource allocation schemes to optimize the performance of WPC and prolong the network lifetime. In this paper, harvest-then-transmit-based WP non-orthogonal multiple access (WP-NOMA) system is designed with time-split (TS) and power control (PC) allocation strategies. To evaluate the network performance, the sum rate and UEs’ rates expressions are derived considering power-domain NOMA with successive interference cancellation detection. For comparison purposes, the rate performance of the conventional WP orthogonal multiple access (WP-OMA) is derived also considering orthogonal frequency-division multiple access and time-division multiple access schemes. Intensive investigations are conducted to obtain the best TS and PC resource parameters that enable maximum EH for higher data transmission rates compared with the reference WP-OMA techniques. The achieved outcomes demonstrate the effectiveness of designed resource allocation approaches in terms of the realized sum rate, UE’s rate, rate region, and fairness without distressing the restricted power of far UEs.
With the substantial growth of mobile applications and the emergence of cloud computing concepts, therefore mobile Cloud Computing (MCC) has been introduced as a potential mobile service technology. Mobile has limited resources, battery life, network bandwidth, storage, and processor, avoid mobile limitations by sending heavy computation to the cloud to get better performance in a short time, the operation of sending data, and get the result of computation call offloading. In this paper, a survey about offloading types is discussed that takes care of many issues such as offloading algorithms, platforms, metrics (that are used with this algorithm and its equations), mobile cloud architecture, and the advantages of using the mobile cloud. The trade-off between local execution of tasks on end-devices and remote execution on the cloud server for minimizing delay time and energy saving. In the form of a multi-objective optimization problem with a focus on reducing overall system power consumption and task execution latency, meta-heuristic algorithms are required to solve this problem which is considered as NP-hardness when the number of tasks is high. To get minimum cost (time and energy) apply partial offloading on specific jobs containing a number of tasks represented in sequences of zeros and ones for example (100111010), when each bit represents a task. The zeros mean the task will be executed in the cloud and the ones mean the task will be executed locally. The decision of processing tasks locally or remotely is important to balance resource utilization. The calculation of task completion time and energy consumption for each task determines which task from the whole job will be executed remotely (been offloaded) and which task will be executed locally. Calculate the total cost (time and energy) for the whole job and determine the minimum total cost. An optimization method based on metaheuristic methods is required to find the best solution. The genetic algorithm is suggested as a metaheuristic Algorithm for future work.
In this study, we propose a compact, tri-band microstrip patch antenna for 5G applications, operating at 28 GHz, 38 GHz, and 60 GHz frequency bands. Starting with a basic rectangular microstrip patch, modifications were made to achieve resonance in the target frequency bands and improve S11 performance, gain, and impedance bandwidth. An inset feed was employed to enhance antenna matching, and a π–shaped slot was incorporated into the radiating patch for better antenna characteristics. The design utilized a Rogers RT/Duroid-5880 substrate with a 0.508 mm thickness, a 2.2 dielectric constant, and a 0.0009 loss tangent. The final dimensions of the antenna are 8 x 8.5 x 0.508 mm3. The maximum S11 values obtained at the resonant frequencies of 27.9 GHz, 38.4 GHz, and 56 GHz are -15.4 dB, -18 dB, and -26.4 dB, respectively. The impedance bandwidths around these frequencies were 1.26 GHz (27.245 - 28.505), 1.08 GHz (37.775 - 38.855), and 12.015 GHz (51.725 - 63.74), respectively. The antenna gains at the resonant frequencies are 7.96 dBi, 6.82 dBi, and 7.93 dBi, respectively. Radiation efficiencies of 88%, 84%, and 90% were achieved at the resonant frequencies. However, it is observed that the radiation is maximum in the broadside direction at 28 GHz, although it peaks at −41o/41o and −30o/30o at 38 GHz and 56 GHz, respectively. Furthermore, the antenna design, simulations, and optimizations were carried out using HFSS, and the results were verified with CST. Both simulators showed a reasonable degree of consistency, confirming the effectiveness and reliability of the proposed antenna design.