Volume 10, Issue 2, September 2011


Customized RSSI Method for Passive UHF RFID Localization System [Full Text]

I. Kharrat, Y. Duroc, G. Andia Vera, M. Awad, S. Tedjini and T. Aguili

Abstract—
This paper presents a new method for positioning a tag using passive Ultra High Frequency (UHF) Radio Frequency Identification (RFID). Some approaches ignore the key issue that the RFID equipment itself can introduce significant amount of experimental errors. The proposed technique is based on the well-known RSSI (Received Signal Strength Indicator) approach but several innovations are introduced for improving the localization in order to take into account practical aspects and real tag properties. Simulation results are found to be in good agreement with theoretical results, and they emphasize the relevance of the proposed concept.

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A Compact Wideband Antenna with CPW-fed Monopole for WLAN/WiMAX Operation
[Full Text]

M. Koohestani, M. Khaghani and H. Asadi

Abstract—
This  paper  presents  a  new  compact  planar  wideband  antenna  with  CPW–fed  monopole,  suitable  for  WLAN  and WiMAX operations, providing a tunable bandwidth. By simply tuning the lengths of the CPW ground plane which results in an asymmetric ground plane structure, the range of bandwidth can be obtained from 2.3 to 7.6 GHz which can operate in WLAN (2.4–2.484  GHz,  4.9–5.1  GHz,  5.15–5.35  GHz,  5.7–5.9  GHz)  and  WiMAX  (2.5–2.7  GHz,  3.4–3.6  GHz,  5.7–5.9  GHz).  The antenna is as small as 23 mm × 20 mm × 1 mm. The performance of the antenna have been simulated and measured, showing good impedance bandwidth and omnidirectional radiation patterns across its entire tunable frequency range.

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A Novel Modified Monopole Antenna with  a 5.5 GHz Notch Filter [Full Text]

A. Siahcheshm and Y. Zehforoosh

Abstract—
This  paper  presents  the  results  of  a  modified  monopole  antenna  that  exhibits  3-27  GHz  performance.  The  proposed  antenna consists of a triangular shaped radiating patch  with notches. Also, the antenna’s  truncated ground-plane incorporates a central notch. This modification significantly improves the antenna’s impedance bandwidth by 160% over an ultra-wideband frequency range from 3 to 27 GHz. The return-loss (S11) performance over this frequency range is simulated to be better than -10 dB. These characteristics make the proposed antenna an excellent candidate for numerous UWB applications and next generation communication systems. The key physical parameters
affecting the antenna’s frequency characteristics have also been investigated in order to determine optimum antenna performance. The antenna’s simulated return-loss, and E-plane and H-plane radiation patterns show very good correlation with the requirements of UWB applications. 
 
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A Novel Technique for Time Synchronization in OFDM Systems
[Full Text]

Akram Ramezani
 
Abstract
This paper  presents a new method for time  synchronization in OFDM systems. The method is based on exploiting the correlation caused by appending the cyclic prefix to OFDM symbols. According to the simulation results, the improvement in estimation accuracy is quite considerable comparing to similar methods.

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Analytical View of Cryptographic Techniques through Cryptool [Full Text]
 
Sonal Kulshreshtha, Vikram Verma and Richa Kalra

Abstract— Cryptography is an emerging technology, which is important for network security. Research on cryptography is still in its  developing stages and  a considerable research  effort is still required  for secured communication.  This  paper  is  devoted  to  the security and  attack aspects of cryptographic techniques. The simulation  based  information  content  test  such as  Entropy, Floating Frequency, Histogram, N-gram, Autocorrelation and Periodicity on ciphers is done. The simulation based Randomness test such as Frequency test, Pokers test, Serial test, Long run test on ciphers are done using CrypTool.  

 
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A Performance Enhancement of IEEE 802.11a OFDM Standard Model [Full Text]
 
Abdul-Salam Mohammed Abood
 
Abstract—
In  this  paper,  the  Doppler  frequency  estimated  for  orthogonal  frequency  division  multiplexing  (OFDM)  systems  in  time-varying multipath  channels.  The  proposed  scheme  is  a  time-domain  approach  that  utilizes  pilot  subcarriers,  which  are  commonly  implemented  in most  practical  systems  and  the  estimation  be  done  in  time  domain  due  to  using  the  blocks  of  fast  Fourier  transform  (FFT)  and  its  inverse (IFFT)  at  the  transmitter  and  the  receiver  sides  respectively,  in  addition  to  those  standard  blocks.  Time-varying  fading  causes  intercarrier
interference (ICI) in OFDM systems. Thus, in the proposed algorithm, the effect of ICI is taken into consideration with a proper model for ac-curate results. The proposed algorithm can be implemented by simple addition and subtraction blocks based on shifting the data horizontally and adding them vertically (sub-blocks).We evaluate the system performance in flat fading and the AWGN channel to prove the effectiveness of the proposed model. The simulation results show that the proposed algorithm enhanced the system performance in terms of bit error rate (BER), thus it can be considered as alternative technique to the standard model. 

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Performance Improvement of DS-CDMA Wireless Communication Network with Convolutionally Encoded MSK Modulation Scheme [Full Text]

Manish Rai and Saurabh Katiyar

Abstract—
This paper considers the bit error probability analysis of Direct-Sequence Code-Division Multiple Access (DS-CDMA) system. A statistical characterization of the decision variable at transmitter and receiver is obtained. System is simulated with MSK modulation scheme which when compared with conventional Binary Phase Shift Keying (BPSK) gives improved performance in terms of Probability of Error (Pe). Convolution coding is further incorporated with both of the modulations schemes and results show that this coding further improves the system when compared without coding. However, mathematical analysis includes exact bit error calculation as well as various approximation methods based on Gaussian modeling of the Multiple-Access Interference (MAI) terms.