Volume 8. Issue 2, May 2011

On the energy efficiency of Virtual MIMO architectures implemented in Wireless Sensor Networks [Full Text]

George N. Bravos and George I. Dimitrakopoulos

Abstract—Wireless sensor networks (WSNs) represent complex distributed systems that comprise wireless mobile nodes that can (re)organise themselves into arbitrary and temporary network topologies. In this respect they have become suitable for a wide range of applications during the recent years. Due to their special functional characteristics, WSNs demand the implementation of energy-aware techniques in all layers. Recently, a MIMO – based structure has been proposed to offer enhanced energy savings in WSNs under certain circumstances. Based on that idea several alternatives have been examined, and some typical threshold values have been estimated regarding the network’s density, the channel conditions and the distance to the destination node. The goal of this paper is to summarize the main energy and topology models used for both MIMO – based and typical multihop structures, as well as to compare their performance in terms of energy efficiency. Furthermore, the paper expands the already typical threshold values to cases that express advanced applications

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Performance Analysis of a Nationwide Telemedicine Call Center
[Full Text]

Ishtiaq Al Mamoon and Shahriar Khan

Abstract—The object of study was a GSM medical call centre or service point where patients are connected over mobile phone to doctors, who provide emergency services, medication, and drug information. The GSM call centre is equipped with a class IV public switch as Inter exchange carrier, and a PBX. Subscribers can dial 789 from anywhere in Bangladesh, with a phone under the operator. The call hit rate is indicative of patient response, and generally showed an upward trend during its existence. The survey conducted among responding agents showed the strengths, and areas requiring improvement of
this system. A significant number of callers were assisted during medical emergencies. At this time, the call patterns indicate that this project is likely to be sustainable, and that medical tele-conferencing over cellular phone has a potentially large market.

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Effects of Spatial Dispersion on Natural Modes Characteristics of Mushroom-type High Impedance Surfaces
[Full Text]

Mohsen Fallah, Farrokh H. Kashani, Amir A. Heydari, Alireza mallahzade and Hosein M. Armaki

Abstract— In this paper, the effects of spatial dispersion (SD) on natural modes characteristics of mushroom-type high impedance surfaces based on local and nonlocal homogenization methods are studied. Modal characteristics of mushroom-type high impedance surfaces are showing the importance of spatial dispersion (SD) in wire-medium (WM) slabs. Results obtained by different homogenization models are compared leading to important conclusions. Specifically, an interesting observation concerns the mushroom-type HISs, wherein the SD of the WM slab is significantly redused, and the results of local and nonlocal homogenization models are in excellent agreement except in plasma resonance of wire medium. Moreover, the results that are obtained by analytical models are verified by numerical full wave HFSS simulations.

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Multi-Band 4G Wireless sub-sampling receiver Based on: ISPD synthesizer and New Multi band IIR Filter
[Full Text]

Bilel GASSARA and Nouri MASMOUDI

Abstract—In 4G wireless receivers, the sub-sampling technique used in frequency translation offers to the receiver: a simple architecture, the multiband ability and gives a discrete time signal which can be treated easily. In previous work, we focused the research on the frequency synthesizer which presents the key assumption of multiband receiver and we profited the advantages of the Inverse Sine Phase Detector (ISPD) PLL with our new model of the inverse sine function, in addition, we designed a new multiband VCO applied in the synthesizer architecture. In this paper, we present our total and extended work by including all the designed parts in the receiver architecture and presenting a new design of an auto-reconfigurable base band anti-aliasing digital filter applied in GSM/DCS/WLAN-WiMax receiver, without using any added blocks like decimators and switches. The ADS simulation results show its ability to be used in multiband application without SNR degradation.

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Failures in the Field for Base Transceiver Stations
[Full Text]

Sheikh Wadud Ahmed and Shahriar Khan

Abstract—The growing popularity of cell phones has greatly increased the importance of mobile-phone base stations. Outage, call drop, and diminished operation of even a single voice channel can lead to significant loss of revenue. This paper reports some failures in the field of BTS. Selected failures have been shown in detail. Faults due to cableconnectors were found to contribute to the largest number of outage hours. Microwave misalignment owing to bad
weather was another cause of incipient failures. The analysis in this paper will help determine better design, operation, installation and maintenance for BTS.

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Comparative Analysis between Various Types of Corrugated Profiled Horns
[Full Text]

S. H. Mohseni Armaki, R. Kazemi, F. H. Kashani and M. Fallah

Abstract—A parametric study is performed to the various types of conical corrugated profiled horn antennas. The obtained simulated results are presented graphically to show the features of the horns in terms of gain, cross polarization return loss, phase center and radiation patterns. The objective of this paper is to simulate some profiles and compare results with corrugated linear profiled horn as reference antenna.

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Improving the Performance of Data Delivery in Wireless Sensor Networks
[Full Text]

Rezaul Karim, Md. Hasan Furhad, Md. Khaliluzzaman and Md. Ariful Islam Khandaker

Abstract—A wireless sensor network is a group of sensors that are geographically distributed and interconnected by wireless networks. Sen-sors gather information about the state of physical world. Reliable data transfer is an important facet of dependability and quality of service (QoS) in WSNs. Supporting QoS will be of critical importance for pervasive WSNs that serve as the network infrastructure of diverse applica-tions. This paper gives us idea about QoS concepts as well as how can we achieve better reliability in WSNs. Thus, we first review about WSNs as well as sensor nodes, analyze new QoS requirements in WSNs from a wide variety of applications classified by data delivery models and propose QoS in WSNs considering the packet to be small in size so that it can travel faster through the network by avoiding collision. In this way we can improve the Quality of Service in the network. Finally we presented our simulation by NS-2 (Network Simulator).

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On the Implementation of FPGA-Based Adaptive Synchronizer of DSSS Receiver
[Full Text]

Hamidreza Merajpour and Mohammad Hossein Madani


Abstract— Real time performance of adaptive digital signal processing algorithms is required in many applications but it often means a high computational load for many conventional processors. In this paper, we present a configurable hardware for adaptive synchronization of DSSS receiver. The architecture has been designed to deal with parallel/pipeline processing and composed of adaptive acquisition and tracking. This architecture has been simulated on a FPGA device and implementation results are presented.

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Weights Optimization of 1D and 2D Adaptive Arrays Using Neural Network Approach
[Full Text]

Mohammed A. Ghali and Abdulkareem S. Abdullah

Abstract—In this paper, a neural network approach to the problem of finding the weights of one and two dimensional adaptive arrays is presented. In this approach, the computation of the optimum weights is accomplished using three-layer radial basis function neural networks (RBFNN), which treats the problem of computing the weights of an adaptive array antenna as a mapping problem. The algorithm is performed for two applications, linear and planar arrays at different distributions.

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Implementation of a GSM Based Nationwide Medical Call Center
[Full Text]

Ishtiak Al Mamoon and Shahriar Khan


Abstract—An inbound time switching based nationwide call center for medical consultation is a relatively new concept in real-time telemedicine. In this work, a telemedicine project based on the GSM network, is implemented, and analyzed. The GSM Medical call center is accessible through dialing 789 on the GP mobile phone, allowing patients to consult directly with doctors. A brief discussion of the technology and the setup of a GSM/PSTN call center is given. The commissioning of different equipments, system integration, results, technical follow up, and error handing are described. It is intended that these tools and guidelines will aid those involved in the development of telemedicine projects in creating successful and sustainable systems. The implementation of these telemedicine systems is a first for Bangladesh. Challenges are identified, with real-life data from a running commercial system. The findings will provide academic and research issues for those building and running a telemedicine system in a developed or a developing country.

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Noise Cancellation for wireless communication systems using Artificial Neural Network
[Full Text]

Poppy Siddiqua and Tasnuva Ali

Abstract—In this work a neural network approach has been used for noise cancellation. In the wireless networks, noise is a drawback for the signal transmission process and also noise degrades the receiver performance. One promising approach to cancel or minimize the noise signal is based on the Artificial Neural Network (ANN). In this work, the ANN is trained with Backpropagation learning algorithm to find optimum weight matrix and then optimized weighted value is used to reduce the error level. Analysis reveals that using the optimized parameter the performance of the noise canceller improves significantly.

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Incipient Failures in the Field for Base Transceiver Stations
[Full Text]

S. Wadud Ahmed and Shahriar Khan

Abstract—The mobile phone Base Transceiver Station (BTS) accounts for about 80 % of total equipment budget. Of great importance is appropriate deployment and maintenance of the BTS. Outage, call drop, and diminished operation of even a single voice channel can lead to significant loss of revenue. Data and records of BTS commissioning and failure were analyzed. This paper provides such data, with the goal of better understanding of commissioning and incipient failure of BTS. Both the VSWR and BER test results were given for selected cases. Faults due to cable-connectors were found to contribute to the largest number of outage hours. Improper commissioning and operation of the BTS has been identified as the cause of various failures.

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Designing of a coin sized Koch Fractal Antenna [Full Text]

Deepali Gupta, Manoj Kumar Pal and  R.P. Agarwal

Abstract—Antenna designing requires many specifications to be considered as operating frequency, size, gain etc. These requirements led to the fractal antenna. Fractals are the highly convoluted shapes of certain fractals, reducing the overall area occupied by a resonant element. Fractals scale down the size of antenna and allow them to be employed for multi-frequencies. This letter is about the reduction of size and increase in iterations of a Koch loop antenna. This scaling results in a very small 11*11mm antenna having tremendous variations in performance parameters.

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Simulation of Sierpinski Carpet Fractal Antenna
[Full Text]

Alok Nath Yadav, Rajneesh Chawhan, Dr. P. K. Singhal and Kumar Anubhav Tiwari

Abstract—This paper deals with the design of Sierpinski carpet fractal antenna. The method of moments (MoM)-based IE3D software was used to simulate the results for return loss and radiation patterns. The analysis took place between ranges of 0.5GHz to 3GHz. The Sierpinski carpet fractal antenna proves that it is capable to create multiband frequencies. There are four resonant frequencies appeared at 0.85 GHz, 1.83 GHz, 2.13 GHz and 2.68 GHz.