International Journal of Wireless and Microwave Technologies @ijwmt
Статьи журнала - International Journal of Wireless and Microwave Technologies
Все статьи: 562
Multiband microstrip antenna using modified pi-shape slot on ground plane
Статья научная
This paper proposes a multiband microstrip antenna with modified pi-shape slot cut on the ground plane for wireless applications. Complete modal analysis and design process of the proposed antenna is demonstrated explaining the modes contributing to achieve the bands. By placing the modified pi-slot in the appropriate position on the ground plane, it tunes TM10, TM12, TM02 and TM20 and TM22 mode frequencies with respect to the fundamental mode frequency and thus realizes four band response which includes one broadband response having 164 MHz (6.5%) bandwidth. The bandwidth in the other bands are in the range of 6 MHz - 30 MHz. The surface currents at these modes are also altered to yield broadside radiation pattern. Suspended version of this antenna is also proposed that offers triple bands and improved broadside gain of around 4 dBi at the broadband besides 2.5 dBi and 1 dBi gain at other two modes. The proposed antenna saves 56% area with respect to the equivalent un-slotted microstrip antenna.
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Multipath Cluster-based Hybrid MAC Protocol for Wireless Sensor Networks
Статья научная
The WSN (Wireless Sensor Network) is the most appearing expertise that has potential applications broad ranges that include environment examining, smart spaces, medical systems, and robotic study. The efficient energy is a consideration of vital design for WSN. In WSNs, the collision is occurred due to data transmission from the sensor nodes and the traffic at SINK node is high due to the transmission of excess data by the sensor nodes. An important division of the consumption of resources in a WSN is managed by the mechanism of MAC (Medium Access Control). An existing MAC protocols initiated for the utilization of WSNs single channel for the transmission of data. This is basically because of the reality that efficient energy is measured to be the issue of essentiality in WSNs. A new multi-channel MAC procedure MPCB-HM is proposed which utilizes CSMA/CA (Carrier Sense Multiple Access/ Collision Avoidance), to exchange the data, the activity of TDMA (Time Division Multiple Access) sequencing nodes and also FDMA (Frequency Division Multiple Access) to allow collision-free exchange simultaneously. The nodes have multiple communication channels, so that the high data traffic can be shared in multiple channels. This reduces the overhead in the nodes and the Energy consumption is minimized by this method and collision free transmission is achieved. With the help of intra-cluster communication and inter-cluster communication, the MAC mode control is responsible for shifting of mode from TDMA to CSMA and vice versa. The Cluster-based topology is implemented which helps in improving the scalability and energy efficiency. By utilizing the simulator of NS2, the process is estimated and the outcomes have shown that the procedure of MAC is improved by overall network presentation compared to the other protocols.
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Статья научная
Cellular networks are characterized by mobility in which subscribers move freely within the coverage area. Since the radio spectrum is a scarce resource, the available bandwidth is divided by using a combination of Time- and Frequency-Division Multiple Access (TDMA) Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA). For communication process to succeed, the subscriber must be allocated some frequency band (FDMA), a time slot (TDMA) or pseudorandom binary sequence that modulates the carrier (CDMA). With the increasing number of users, these resources may become unavailable, leading to new call blocking or handover call blocking. Erlang B and Erlang C have been used in the past to model teletraffic blocking in Public Switched Telephone Network (PSTN). Unfortunately, Erlang B is only ideal when subscribers do not perform call re-attempts after their initial calls are blocked. On the other hand, Erlang C model is applicable only in networks where queuing is applied and can easily lead to higher blocking rates when the number of users is high. This is because it takes into consideration the number of instances in the queue as well as the resources under use. In this paper, teletraffic blocking probabilities that take into account additional cellular network concepts such as the number of mobile stations, call retries, channels reservation, overlays and underlays, user velocity, relative mobility, call priority, call arrival rates and signal to interference plus noise ratio (SINR) were synthesized. The simulation results showed that the developed teletraffic blocking probabilities were superior to the conventional Erlang B and Erlang C as they consider new concepts that exist in cellular networks that were not envisioned in traditional PSTN.
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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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Novel Machine Learning Approaches for Identifying Attacks in IoT-based Smart Home Environment
Статья научная
Attackers keep launching different attacks on computer networks. Signature-based and Machine Learning (ML)-based techniques have been used to build models for promptly identifying these attacks in networks. However, ML-based approaches are more popular than their counterparts because of their ability to detect zero-day attacks. In the Internet of Things (IoT), devices are interconnected and this called for the need to guide such networks against intrusions. This study aims at building effective ML models from a recently released IoT-based Smart Home dataset. The study revealed patterns and characteristics of the IoT dataset, pre-processed it and then selected discriminant features using Binary Bat Algorithm (BBA). The pre-processing of the Smart Home IoT dataset for the study was carried out based on the issues identified during the exploratory analyses. The experimental evaluation carried out revealed that all the learning algorithms achieved promising classification results. For instance, Decision Trees recorded 98.60% accuracy, KNN produced 99.60% accuracy while Random Forest (RF) and AdaBoost-based models recorded 100.00% and 99.91% respectively. In all other metrics, RF-based attack classification model slightly recorded the best results. The study concluded that the EDA, innovative data pre-processing, BBA-based feature selection improved the classification performances of the ML approaches used in this study.
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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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Статья научная
5G Heterogeneous network is characterized with small cells in close proximity with one another which in most cases are active even at low traffic load periods. Such scenarios lead to unnecessary large energy consumption and co-frequency interference. This large energy consumption and interference in 5G heterogeneous networks have been an issue widely discussed in several technical literature. Different and attractive techniques on energy management have been investigated and proposed. All these have been in seeking ways of minimizing or reducing energy consumption in mobile networks. In this study the on/off and sleep-mode schemes as energy management techniques have been reviewed with the major aim of identifying weak areas of both techniques and suggesting ways which will be useful for further research works in the future. In doing so recent literature on the subject matter were consulted. The on/off and sleep-mode schemes involve switching processes which result to loss of data and information during change of state. Quality of service issues arising from incomplete or proper switching process and unnecessary delay perceived by the users were observed as major concern for both schemes. For further work, amongst other suggestions, it is suggested that the time needed between system switching command and switching operations be considered as an important factor in eliminating switching problems which will positively affect the overall quality of service.
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Optimal Cluster Size for Wireless Sensor Networks
Статья научная
Since energy consumption is one of the main challenges in wireless sensors networks performance and efficiency, this paper discusses and proposes a mathematical model that compromises these two crucial parameters. In addition, number of clusters, cluster size, and number of cluster heads all contribute in network robustness; they have been studied and manipulated in details. This paper suggests a mathematical model that calculates and finds the optimal cluster size and number of sensors for Low Energy Adaptive Cluster Hierarchy (LEACH) protocol. Wireless Sensor Network (WSN) is a network includes devices (sensors) for collecting data by sensing the field. Clustering is one of the simplest strategies used to minimize the power lost in WSNs. Its performance is affected by network area and number of sensors. The cluster head is elected based on traditional Low Energy Adaptive Cluster Hierarchy protocol. The optimal cluster number is detected based on the condition of the LEACH delivery ratio. NS2.35 and MannaSim framework are applied for validating the proposed model. The results show that the proposed model is approved at different areas and nodes density. The optimal cluster size obtained by the proposed model is equivalent to optimal clusters number for 100 % delivery ratio of LEACH.
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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
This paper explores the potential of Ultra-Massive Multiple Input Multiple Output (UM MIMO) systems as a key technology for 6G wireless communications within the Terahertz (THz) frequency band (0.1 – 10 THz). The THz spectrum offers immense capacity and speed advantages but presents significant challenges, such as higher propagation losses and limited coverage range due to atmospheric absorption and signals spreading. The study provides a comprehensive analysis of UM MIMO’s technical performance in overcoming these challenges, focusing on key metrics such as signal propagation, system capacity, and coverage range. Additionally, the research examines the optimization of beam dynamics and spectral efficiency in UM MIMO systems under various wireless channel conditions and precoding techniques. The findings highlight the importance of advanced antenna techniques and adaptive beam management in maximizing the efficiency and viability of 6G THz networks, positioning UM MIMO as a fundamental solution for next-generation wireless communication.
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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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