Статьи журнала - International Journal of Wireless and Microwave Technologies
Все статьи: 454
Mutual Coupling Reduction between H Shaped Compact MIMO Antenna for WLAN Application
Статья научная
A simple compact H shaped MIMO antenna for WLAN application at resonating frequency 5.8 GHz is propose in this paper. The center to center spacing between closely placed H shaped MIMO antenna is 0.311λo. The mutual coupling between the proposed antenna is reduced by using dumbbell shaped DGS at the center of the groundplane. These dumbbell shape defect act as bandstop filter because of its inductance and capacitance effect, helps to suppress the surface wave propagation of waves. The filter characteristic of the dumbbell shaped DGS is studied to achieve isolation over the 5.725-5.875 GHz frequency band. Further the parametric study such as length, width and the spacing of dumbbell shaped DGS is optimized and studied in order to achieve good isolation among the MIMO antenna elements. The proposed MIMO structure is fabricated on low cost FR4 substrate having thickness of 1.6mm and the overall dimension of MIMO antenna is 40mm x 24 mm leading to compact size of antenna. The mutual coupling reduces from 24 dB to 34 dB by placing dumbbell shaped DGS. The envelope correlation coefficient for the proposed antenna is below less than 0.04 dB for the operating frequency band. The proposed H shaped MIMO antenna is tested and the measured result follows the simulation results. Therefore the proposed antenna is a good candidate for WLAN application.
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Статья научная
Near Field Communication (NFC), an emerging short-range wireless point to point interconnection technology, with the combination of handheld electronic device has become a potential tool for the two devices to exchange various information when in close range. NFC unites various standards and proprietary technologies. This paper presents a brief introduction about the NFC and various applications and security issues.
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New Downlink Scheduling Framework for Hybrid Unicast and Multicast Traffic in WiMAX Networks
Статья научная
WiMAX networks based on IEEE 802.16 standard has expedited broadband wireless access surge in recent years. The traffic in these networks is identified in four types of class of service with different QoS requirements. Therefore, scheduling mechanism to manage these services in order to meet QoS requirements is a crucial fact and an important challenge. In this paper, for PMP mode of WiMAX networks, a two-level scheduling mechanism in MAC layer of Base Station (BS) has been proposed. The proposed scheduling algorithm takes into account hybrid unicast and multicast downlink traffic including three classes of service: rtps, nrtps and BE. In the first level of this scheduling mechanism, we have used the scheduling algorithms WRR and FCFS to schedule the connections and in its second level, the PQ algorithm based on Aging method is used to manage and schedule the packets. The functionality of the proposed scheduling algorithm is compared with priority queuing (PQ) algorithm. The resulting outcome of simulation shows that the proposed design has quite a better performance for Best Effort (BE) service class. Furthermore the delay of the rtps class and total throughput of the network is increased noticeably.
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New Intrusion Detection Framework Using Cost Sensitive Classifier and Features
Статья научная
The huge increase amount of Cyber Attacks in computer networks emerge essential requirements of intrusion detection system, IDS to monitors the cybercriminals. The inefficient or unreliable IDS can decrease the performance of security services and today world applications and make the ongoing challenges on the Cyber Security and Data mining fields. This paper proposed a new detection system for the cyber-attacks with the ensemble classification of efficient cost sensitive decision trees, CSForest classifier and the least numbers of most relevant features are selected as the additional mechanism to reduce the cost. The standard dataset, NSL-KDD, IDS is used to appraise the results and compare the previous existing systems and state-of-the-art methods. The proposed system outperforms the other existing systems and can be public a new benchmark record for the NSL-KDD datasets of intrusion detection system. The proposed combination of choosing the appropriate classifier and the selection of perfect features mechanism can produce the cost-efficient IDS system for the security world.
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Next Generation Campus Network Deployment Project Based on Softswitch
Статья научная
After analyzing the current networks of Guizhou University，we brought forward a scheme of next generation campus networks based on softswitch technology by choosing SoftX3000 switching system of HuaWei and provided the specific solution of accessing campus networks in this paper. It is proved that this scheme is feasible by using OPNET, which not only accomplished the integration of the PSTN and IP networks but also achieved the combining of voice services and data services.
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Novel Hybrid Spectrum Handoff for Cognitive Radio Networks
Статья научная
Cognitive radio (CR) is projected as a technology (or solution) that will raise the spectrum utilization considerably by allowing low-priority or secondary user (SU) to utilize the spectrum of high-priority or primary user (PU) opportunistically. Spectrum handoff is a different type of handoff necessitated by the reappearance of the primary user on the frequency channels occupied by the secondary user at that time and location. In this paper, a hybrid type of spectrum handoff algorithm is proposed where proactive decision and reactive decision approaches are combined. Depending on the arrival rate of primary user (i.e. PU activity), the algorithm switches from reactive decision mode to proactive decision mode and vice versa. The switching from one mode to another mode depends on threshold value of PU activity and we evaluated the threshold value through analysis for switching of the algorithm to be 0.37. Simulated results show that the proposed hybrid spectrum handoff algorithm reduces the total service time of secondary user considerably compared to conventional proactive decision or reactive decision handoff approaches.
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Numerical Analysis of Slot Position of Rectangular U Slot Microstrip Patch Antenna
Статья научная
The main focus of this paper is to study and analyze how the performance of rectangular U slot antenna is affected by the variation of U slot position. The work presented herein is a simulation based study. Experimentally, it has been revealed that variations in parameters such as the width and length of the U-slot, height and size of the patch, probe size and location as well as substrate permittivity can dramatically change the antenna's behavior. Till date, no analytical methods have been developed that accurately relate the complex relationships between the antenna dimensions and individuality. This paper describes the behavior of antenna with change of U slot position. A numerical solution is obtained by varying the various positions of U slot along all the axis and the effect of U slot position on various antenna output parameters is analyzed.
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Numerical Investigation of a Polarization-insensitive Energy Harvesting Metasurface
Статья научная
This paper presents the numerical study of a polarization-insensitive energy harvesting metasurface. The proposed metasurface is designed to harvest ambient electromagnetic (EM) energy at 2.45 GHz. The basic constituent element of the metasurface is an electric-field-coupled (ELC) resonator, which is used to synthesize a 2 x 2 super-cell with polarization-insensitive features. Finally, the metasurface is realized as a 3 x 3 array of ELC super-cells, and presents an energy harvesting efficiency of 95.4% at 2.45 GHz. The achieved energy harvesting efficiency is maintained irrespective of the polarization of the incident excitation. The proposed metasurface configuration holds promise for the implementation of ambient EM harvesters, able to scavenge energy from wireless technologies operating in the 2.45 GHz band.
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OFDM synchronization techniques for 802.11ac WLAN
Статья научная
It would be dire need of accurate and fast wireless communication in the present as well as future era. Few years ago, error free wireless link design was only challenge and it had opened a way of digital communication. Now speed of communication becomes vital and essential part of research in the field of wireless communication. In wired communication category, optical communication is a solution to achieve targeted data speed but wireless channel for serial communication is highly disturbed with the phenomena of multipath and frequency selective fading for a data rate over a specific limit. A new technology named Orthogonal Frequency Division Multiplexing (OFDM) is a perfect key to open this locking situation of limited data rate with optimum use of bandwidth in the multipath fading channel. Supporting high data rates and robust response against narrowband interferences, OFDM had penetrated itself in many broadband wireless services. There are many issues with OFDM too and one of them is synchronization between orthogonal frequency channels at receiver. It is mandatory condition in the use of OFDM technology to maintain orthogonality among subcarriers for error free communication. Timing and frequency synchronization errors are quite detrimental to this condition because these errors ultimately disturb the orthogonality which is perfectly set at transmitter. Synchronization errors need to be handled properly otherwise they create Inter-Symbol Interference (ISI) and Inter-Channel Interference (ICI) which after all resulted into the deterioration of Bit Error Rate (BER). This paper covers types of synchronization and its effects, algorithms to decrease it and analysis of the same.
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On Design of Modified Hexagonal Slot UWB Antenna with Band Notched Characteristics
Статья научная
A micro strip-fed printed, modified hexagonal slot ultra wideband antenna with a band notch function is presented as well as investigated in this paper. The basic antenna comprises a U-shape radiating patch on one side of the substrate and ground plane with modified hexagonal slot on the other side of the substrate. Proper alignment and use of a modified hexagonal slot gives additional resonances and much wider impedance bandwidth is obtained. To create a notched band for WiMAX, symmetrical L- shape parasitic stubs are embedded in the upper edge of the modified hexagonal slot of the ground plane. The proposed antenna operates over the frequency band from 2.71 GHz to 11.73 GHz with a band rejection from 3.27-4 GHz (for WiMAX).The proposed antenna is fabricated on a FR-4 substrate having a dielectric constant of 4.4 with an overall size of 28 x 28 x 1.6mm3. Parametric studies have been conducted by changing length, width and thickness of symmetrical L- shape parasitic stubs. Simulated results are in good agreement with measured results. Designed antenna exhibits good radiation, efficiency greater than 80% within the entire ultra wideband except for WiMAX frequency.
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Optimal Spectrum Access for Users in Multi-Channel Cognitive Radio Networks
Статья научная
Cognitive Radio, a software defined radio, is an emerging technology which uses opportunistic spectrum access (OSA) for the efficient utilization of the spectrum. Its main aim is to utilize the unused portions of the spectrum by allowing unlicensed users (secondary users) to transmit data in absence of primary users. In this paper the assignment of multiple primary and secondary users in a multiple channel system is addressed with the sole aim of optimizing the total throughput. We have considered an optimal spectrum access (OSA) algorithm for the allotment of both the primary and secondary users in a multiple channel system and compared the results with the well-known meta-heuristic techniques such as Simulated Annealing (SA) and Tabu Search (TS). The results reveal that OSA algorithm is more efficient as compared to SA and TS as far as throughput optimization is considered.
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Статья научная
OFDM is a technique that is chosen for high data rate communication and is important for 4th generation communication systems. To provide best possible quality of service, intelligent allocation of resources such as power, bandwidths are necessary. Various algorithms have been proposed for allocation of resources. Fuzzy Rule Based System (FRBS) and Particle Swarm Optimization (PSO) algorithm are used for optimization of code rate, modulation and power. FRBS is used to choose the best possible modulation and code rate and PSO is used for better power allocation.
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Статья научная
Researches in the reduction of peak-to-average power ratio (PAPR) from orthogonal frequency division multiplexing (OFDM) output signals are being done using many techniques. Selected mapping (SLM) technique is a distortion-less technique and is a well known method to reduce high PAPR of OFDM signal. One drawback of SLM is its requirement of side information bits to recover original data block at the receiver side which lead rate of data loss. In this paper, we have proposed a sequential phase sequence SLM (SPS-SLM) based OFDM transceiver without side information and studied its performance. For the proposed method, a specific set of phase sequences is designed. MATLAB simulation shows that the proposed scheme performs well in terms of PAPR. Proposed method provides almost the same PAPR reduction performance compared to the conventional SLM method requiring side information.
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PPLS: personnel presence locator system – an amalgam of RF ranging & Zigbee in WSN
Статья научная
In this day and age of occupied time plans, individuals are confronting numerous issues in following the employees and specialists in colleges, schools, universities, doctor's facilities and so forth, hence it ends up vital that each assignment is expert intelligently, productively and in an auspicious way. To achieve this, easy accessibility of people of interest is a must. To alleviate this problem, we propose a solution called “Personnel Presence Locator System (PPLS)” that is an internetworked amalgam of small systems working independently. Moreover, in this article, we give an overview of the naturally multidisciplinary writing of human-detection, concentrating essentially on the extraction of five regularly required properties: in particular Location, Count, Presence, Track, and Identity. The objective of this work is to uncover the abilities and constraints of existing solutions from different disciplines, to manage the production of new frameworks like PPLS and point toward future research bearings.
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PRDSA: Effective Parallel Digital Signature Algorithm for GPUs
Статья научная
RSA based Digital Signature algorithm is an electronic scheme to ensure the security, authenticity and integrity of an electronic document intended to be used on Internet. Due to the involvement of RSA in signing and signature verification which is based on the series of modular multiplications and modular reductions on very large integers, the RSA based digital signature algorithm become compute-intensive and takes lot of time and energy to execute. A potential solution to this problem is to use the massive parallel powers of the multiprocessors of GPU that can simplify its complex computational part via CUDA programming. This paper presents a faster GPU based pRDSA algorithm which serves the same purpose as the RSA Digital Signature Algorithm but with less computational complexity. Proposed algorithm is an energy efficient parallel version of Digital Signature Algorithm to achieve high performance in the area of network security. It is based on SIMD model of parallel programming and implements repeated square-and-multiply method to compute the digital signature. The conceptual model of pRDSA and its performance have been discussed in this paper.
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PRoPHET Using Optimal Path Hops
Статья научная
The opportunistic network paradigm has no stable path and synchronous end-to-end communication. In such an environment, the bundle originator or the infected node stores a redundant copy in its buffer. This copy is replicated to other encountered susceptible nodes based on routing decision. The performance of the employed routing is based on delivering the bundle through optimal paths. This paper improves the decision criteria of the PRoPHET routing. This enhancement is achieved by employing the bundle probability and the optimal path hops. We have called our proposed improved PRoPHET utilizing Optimal Path Hops (PRoPHET-OPH). The evaluating of its performance is conducted by delivery probability, mean delay and percentage of overhead. Numerical findings exhibit that the PRoPHET-OPH performance is superior compared with the traditional PRoPHET.
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Pattern-based and Time-Synchronised Passwords
Статья научная
World has been changed; every person is using a number of software, websites, and other systems that are using text-based passwords as a method of authentication. These passwords need to be strong, hard to guess, and need to be stored in a secure environment. Major problems with passwords are caused by human limitations to remember passwords for different accounts. A trade-off between password security and human-memorability made it difficult to create passwords that are strong enough and easy to remember. No satisfactory solutions have been offered to problems associated with a password such as shoulder surfing, eavesdropping, keylogging programs, Trojan horse, brute force attacks, etc. This study suggests a new easy to use approach for creating a password that is easy to remember even for a large number of accounts. Here in this paper, we proposed two methods one is pattern-based passwords, a simple method that is solving the problem of memorability, another is the idea of Time-Synchronized Passwords (TSP), a novel method for creating passwords that are dynamic in nature and change with the passage of time. The novality of TSP is that instead of storing the passwords in database the patterns are stored, and these patterns are related linked with time. The significance of storing pattern instead of actual password is that at a specific time, the password will have only one instance known to the creator of the password, and this particular instance will be different from instances at other times and thus avoids shoulder surfing, eavesdropping, keylogging, and other problems associated with passwords. These methods are easy to implement and can be used in any system.
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Performance Analysis between Analog OFDM & Digital OFDM System
Статья научная
Orthogonal Frequency Division Multiplexing (OFDM) signaling has been widely used for high data rate transmission applications due to its high spectral efficiency and robustness to the frequency selective fading channels. One of the major drawbacks of the analog OFDM system is frequency shifting in every sub-carrier. That's why bit error rate increased in analog OFDM system. In this research, we want to solve the problem of the analog OFDM system by using IFFT circuit instead of the local oscillator. The IFFT circuit takes an input as frequency domain and provides output as a time domain signal for 4-QAM modulation. Basically IFFT circuit acts as a local oscillator in the analog OFDM system. The IFFT circuit only executes operation on a discrete frequency domain signal which is converted into a time domain signal by its. So no frequency shifting occurs in every sub-carrier in the digital OFDM system. As a result BER also decrease in digital OFDM system over the analog OFDM system.
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Performance Analysis of Differential Evolution Algorithm based Beamforming for Smart Antenna Systems
Статья научная
This paper presents smart antenna array beamforming using differential evolution algorithm. The excitation values of the elements in the array are smartly adjusted to control side lobe levels and placing nulls in the interference signal direction while maintaining the beam in the desired signal direction. Different cases are considered to illustrate the performance of this technique. Simulation results show that this evolution algorithm is better than the traditional beamforming algorithms for Smart antenna systems.
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Performance Analysis of FBMC over OFDM for High Data Rate MIMO Configurations
Статья научная
The burgeoning demand of high data rate in next generation wireless communication, the antecedent of the evolution of new multicarrier modulation technique FBMC (Filter Bank Multicarrier) system is OFDM (Orthogonal Frequency Division Multiplexing). Although OFDM has numerous merits but it consumes higher bandwidth due to its cyclic prefix to eliminate ISI (Inter Symbol Interference) in fading channel and shows large PAPR (Peak to Average Power Ratio) in transmission system. To mitigate these problems, FBMC is more suitable candidate in high speed MIMO (multiple input multiple output) system. At first, in this paper, the responses of OFDM and FBMC system have been analyzed with AWGN and Rayleigh fading channel under theoretical and simulation environment. Besides this, Peak to Average Power Ratio (PAPR) with reduction technique, clipping is applied to know the behavior of these systems. Finally, in the area of MIMO scheme, each system is concatenated with MRC, Alamouti STBC and Generalized STBC to find FBMC as superior contender for 5G. Results show that using 16 QAM modulation, BER performance of FBMC significantly achieves 2dB compared to error rate of OFDM in theoretical and empirical analyses under AWGN and Rayleigh channel. Moreover, the clipping technique enhances the response of FBMC in terms of PAPR compared to OFDM approximately 0.5 dB. In MIMO configurations, MRC-FBMC exhibits the improved performance with 2 dB approximately over MRC-OFDM system. Results also show that in the case of Alamouti STBC, at 30dB and 35dB, FBMC (2×1) and (2×2) configurations achieve BER improvement 5×10-4, 3×10-4 respectively than OFDM (2×1) and (2×2) configurations. Generalized STBC investigation reveals that to reach FBMC BER performance, OFDM needs at least 2dB increment at specific error rate. In a nutshell, this paper brings up three distinct types of appealing features of FBMC such as good BER response, reduced PAPR, and suitability in MIMO configuration compared to OFDM. These distinct features make FBMC an ultimate choice in the emerging areas of MIMO networks.
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