Volume 27, Issue 2, October 2014

High Gain Circular Patch Antenna Using Metamaterial Supperstrate for DSRS System Applications [Full Text]

Ali A.Saleh and Abdulkareem S. Abdullah

Abstract— In this paper, a metamaterial unit cell with a very low refractive index over a wide frequency band, from 4.5 GHz to 6 GHz, is proposed and designed. The effective material parameters of the unit cell are retrieved. The unit cell forms a planar three-layer metamaterial structure used as a superstrate for gain and radiation enhancement of a circular patch antenna working at 5.885 GHz. The gain of the proposed antenna is increased from 6.19 dBi to 10.72 dBi and the efficiency from 84.06 % to 88.85% compared with the original antenna at 5.885 GHz. The 3 dB beamwidth becomes narrower from 81.20 to 440 and from 86.60 to 51.70 in E-plane and H-plane respectively. This antenna is suitable for Dedicated Short Range System (DSRS) applications. 

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Design of Radiation Pattern-Reconfigurable 60-GHz Antenna for 5G Applications [Full Text]

Yasir I. Abdulraheem, Abdulkareem S. Abdullah, Husham J. Mohammed, Buhari Mohammedand Raed A. Abd-Alhameed

Abstract—Reconfigurable beam steering using circular disc microstrip patch antenna with a ring slotis proposed. The overall dimension of the antenna is 5.4×5.4 mm2 printed on a 0.504 mm thick, Rogers RT5870 substrate with relative permittivity 2.3 and loss tangent 0.0012. The designed antenna operates at the expected 5G frequency band 60 GHz with a central coaxial probe feed. TwoNMOS switches are configured to generate three different beam patterns. Activating each switch individually results in a near 70o shift in the main beam direction, whereas the frequency characteristics are unchanged. The power gains are between 3.9 dB and 4.8dB for the three states of switches configurations. Simulated results in terms of return loss, peak gains and radiation pattern are presented and show areasonable agreement at the expected 60 GHz bandfor 5G applications. 

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Practical Troubleshooting of G729 Codec in a VoIP Network [Full Text]

Yuri Ritvin

Abstract— In the modern telecom arena VoIP networks became ubiquitous and their share is ever-growing bringing more advanced services to the end users. While the VoIP systems' advantages are undoubted, there are multiple challenges during their deployments and this requires a high level of a technical expertise from the personnel involved in such projects. This paper particularly discusses aspects related to a proper G729 codec deployment, describing the pertinent problems and troubleshooting approach successfully used by the author to solve them. 

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Performance Comparison of Particle Swam Optimization, And Genetic Algorithm in The Design Of UWB Antenna [Full Text]

Husham J.Mohammed, Abdulkareem S. Abdullah, Ramzy S. Ali, Yasir I.Abdulraheem and Raed A. Abd-Alhamee

Abstract—An efficient multi-object evolutionary algorithmsare proposed for optimizing frequency characteristics of antennas based on an interfacing created by Matlab environment. This interface makes a link with CST Microwave studio where the electromagnetic investigation of antenna is realized. Very small, compact printed monopole antenna is optimized for ultra- wideband (UWB) applications. Two objective functions are introduced; the first function intends to increase the impedance bandwidth, and second function to tune the antenna to resonate at a particular frequency. The two functions operate in the range of 3.2 to 10.6GHz and depend on the level of return loss. The computed results provide a set of proper design for UWB system in which the bandwidth achieved is 7.5GHz at the resonance frequency 4.48GHz, including relatively stable gain and radiation patterns across the operating band. 


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New High-Input Impedance MISO-Type Universal Biquad Filter Employing CFOAs [Full Text]

KasimK. Abdalla

Abstract—Anew universal multiple inputs single output (MISO) type biquad employing three current feed-back operational amplifiers (CFOAs) is presented. The circuit having three inputs and one output can realize all the five basic filtering functions namely, low pass (LP), high pass (HP), band pass (BP), Notch-filter (NF) and all pass (AP) in voltage mode. The proposed circuit enjoys the following features: orthogonal control of resonance angular frequency (ωo) and quality factor (Q), low active and passive sensitivities and low-output impedances. The workability of the proposed circuit has been confirmed by PSPICE simulations basedupon AD844 type CFOAs. 

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Detection of electromagnetic jamming signals interfering with a railway track-to-train radio communication [Full Text]

S.Mili, D.Sodoyer, V.Deniau and M.Heddebaut

Abstract—Global System for Mobile communications-Railways (GSM-R) is now widely used for train-to-track radio communication. As for any radio communication system, non-intentional and intentional ElectroMagnetic Interference (EMI) can affect this track-to-train radio link. This paper studies the impact of low-power electromagnetic jammers on this communication. Firstly, experiments performed on a dedicated test bench are presented to evaluate the impact of selected jamming signals on a GSM-R radio communication. In certain jamming conditions, loss of connection can result. Then, a method to detect these jamming signals is presented. We considered and modelled a simplified GSM-R communication chain using a GMSK modulation. This was used to evaluate the impact of the jammer on the IQ constellation representation. As for the experimental part, the same interfering signals are applied. We then use the Error Vector Magnitude parameter to detect the presence of these jamming signals. Depending on the parameters of the modulation chain, we adapt our processing to detect the disturbance. A good detection of the jammed signal is obtained by analysing the EVM parameter while trying to detect these signals in an AWGN channel. 

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Multi-Service Group Key Establishment for Secure Wireless Mobile Multicast Networks [Full Text]

Trust T. Mapoka, Yousef. A.S. Dama, Haider M. AlSabbagh, Simon J. Shepherd and Raed A. Abd- Alhameed

Abstract—Recently there is high demand in distributing multimedia services over the internet to ubiquitous and computational intelligent mobile subscribers by the service providers (SPs). In this instance, provision of those services must be restricted to authorized subscribers via integration of authentication and group key management (GKM). GKM with diverse group services subscribed dynamically by moving subscribers in wireless networks has been omitted in conventional approaches. However it is expected that significant key management overhead will arise in them due to multi-services co-existing in the same network. In this paper, we propose a scalable decentralized multi-service GKM scheme considering host mobility in wireless environment. In the scheme, authentication of mobile subscribers and key management phases are delegated from the trusted domain key distributor (DKD) to the subgroup controllers known as area key distributors (AKD). The trusted intermediate AKDs can then establish and distribute the service group keys to valid subscribers in a distributed manner using identity-based encryption without involving the domain key distributor (DKD). This alleviates unnecessary delays and possible bottlenecks at the DKD. We show by simulation that the proposed scheme has some unique scalability properties over known schemes in terms of optimized rekeying communication and storage overheads. The security performance studies have shown resilience to various attacks.