EVM as generic QoS trigger for heterogeneous wieless overlay network

Fourth Generation (4G) Wireless System will integrate heterogeneous wireless overlay systems i.e. interworking of WLAN/ GSM/ CDMA/ WiMAX/ LTE/ etc with guaranteed Quality of Service (QoS) and Experience (QoE).QoS(E) vary from network to network and is application sensitive. User needs an optimal mobility solution while roaming in Overlaid wireless environment i.e. user could seamlessly transfer his session/ call to a best available network bearing guaranteed Quality of Experience. And If this Seamless transfer of session is executed between two networks having different access standards then it is called Vertical Handover (VHO). Contemporary VHO decision algorithms are based on generic QoS metrics viz. SNR, bandwidth, jitter, BER and delay. In this paper, Error Vector Magnitude (EVM) is proposed to be a generic QoS trigger for VHO execution. EVM is defined as the deviation of inphase/ quadrature (I/Q) values from ideal signal states and thus provides a measure of signal quality. In 4G Interoperable environment, OFDM is the leading Modulation scheme (more prone to multi-path fading). EVM (modulation error) properly characterises the wireless link/ channel for accurate VHO decision. EVM depends on the inherent transmission impairments viz. frequency offset, phase noise, non-linear-impairment, skewness etc. for a given wireless link. Paper provides an insight to the analytical aspect of EVM & measures EVM (%) for key management subframes like association/re-association/disassociation/ probe request/response frames. EVM relation is explored for different possible NAV-Network Allocation Vectors (frame duration). Finally EVM is compared with SNR, BER and investigation concludes EVM as a promising QoS trigger for OFDM based emerging wireless standards.Comment: 12 pages, 7 figures, IJWMN 2010 august issue vol. 2, no.

RC4 Encryption-A Literature Survey

AbstractA chronological survey demonstrating the cryptanalysis of RC4 stream cipher is presented in this paper. We have summarized the various weaknesses of RC4 algorithm followed by the recently proposed enhancements available in the literature. It is established that innovative research efforts are required to develop secure RC4 algorithm, which can remove the weaknesses of RC4, such as biased bytes, key collisions, and key recovery attacks on WPA. These flaws in RC4 are still offering an open challenge for developers. Hence our chronological survey corroborates the fact that even though researchers are working on RC4 stream cipher since last two decades, it still offers a plethora of research issues. The attraction of community towards RC4 is still alive

Bandwidth Enhancement Technique of a Dual-Band Circularly Polarized Dielectric Resonator Antenna

This paper presents the rectangular aperture coupled dielectric resonator antenna with dual-band circularly polarized response. The antenna geometry have stair case shaped rectangular dielectric resonator in the form of main radiating element. The specific geometry provides increment of aspect ratio of the dielectric resonator. This allows merging of various resonant frequencies having higher order modes that result in the bandwidth enhancement. This antenna provides 18.63% and 7.68% of -10 dB S11-parameter bandwidth response in operating passbands, respectively. The specific geometry and the introduction of circular slots in ground plane results in the orthogonal modes excitation at the nearby resonant frequencies. Due to this, the circular polarization response at 7.76 and 8.33 GHz frequencies is achieved. The peak gain of 5.8 and 4.6 dBic is obtained in the respective lower and upper operating passbands. Through parametric analysis, tuning of antenna responseis also achieved. The proposed antenna with the optimized parameters may have potential applications in the microwave C- and X-band setups

Bandwidth Enhancement Technique of a Dual-Band Circularly Polarized Dielectric Resonator Antenna

229-232This paper presents the rectangular aperture coupled dielectric resonator antenna with dual-band circularly polarized response. The antenna geometry have stair case shaped rectangular dielectric resonator in the form of main radiating element. The specific geometry provides increment of aspect ratio of the dielectric resonator. This allows merging of various resonant frequencies having higher order modes that result in the bandwidth enhancement. This antenna provides 18.63% and 7.68% of -10 dB S11-parameter bandwidth response in operating passbands, respectively. The specific geometry and the introduction of circular slots in ground plane results in the orthogonal modes excitation at the nearby resonant frequencies. Due to this, the circular polarization response at 7.76 and 8.33 GHz frequencies is achieved. The peak gain of 5.8 and 4.6 dBic is obtained in the respective lower and upper operating passbands. Through parametric analysis, tuning of antenna responseis also achieved. The proposed antenna with the optimized parameters may have potential applications in the microwave C- and X-band setups

Threshold Optimization in Energy Detection Scheme for Maximizing the Spectrum Utilization

AbstractCognitive radio is a new paradigm in wireless communication for improving the spectrum utilization. Spectrum sensing is a fundamental component of cognitive radio networks. Among all the available spectrum sensing algorithms, energy detection scheme has gained more interest owing to its simple implementation. In this paper, we propose a threshold setting algorithm for energy detection scheme which aims at maximizing the spectrum utilization. A closed-form expression for adaptive threshold for maximal spectrum utilization is derived and analyzed. Numerical results demonstrate that the proposed scheme outperforms the conventional methods of determining the threshold

Quantitative analysis of the security performance in wireless LANs

A comprehensive experimental study to analyze the security performance of a WLAN based on IEEE 802.11 b/g/n standards in various network scenarios is presented in this paper. By setting-up an experimental testbed we have measured results for a layered security model in terms of throughput, response time, encryption overheads, frame loss and jitter. Through numerical results obtained from the testbed, we have presented quantitative as well as realistic findings for both security mechanisms and network performance. It establishes the fact that there is always a tradeoff between the security strength and the associated network performance. It is observed that the non-roaming network always performs better than the roaming network under all network scenarios. To analyze the benefits offered by a particular security protocol a relative security strength index model is demonstrated. Further we have presented the statistical analysis of our experimental data. We found that different security protocols have different robustness against mobility. By choosing the robust security protocol, network performance can be improved. The presented analysis is significant and useful with reference to the assessment of the suitability of security protocols for given real time application