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Search Results: 1 - 10 of 1591 matches for " Xuejun Sha "
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Secure Communication System Based on Alterable-Parameter 4-Weighted Fractional Fourier Transform
Bo Ding,Lin Mei,Xuejun Sha
Information Technology Journal , 2010,
Abstract: By discussing the development of 4-WFRFT, a discrete sequence algorithm for 4-WFRFT based on DFT is introduced and this makes it possible to use 4-WFRFT in a discrete time system. On the basis of analyzing the rotating, squeezing effect to the digital signal constellation by 4-WFRFT process also the similarity of 4-WFRFT signal to Gaussian distribution and the anti-scanning competence of 4-WFRFT signal, an alterable-parameter secure communication system is introduced based on 4-WFRFT secure communication system. Moreover, in the light of frequency-hopping patterns, a dynamic alterable-parameter strategy for single parameter 4-WFRFT and three strategies for multi-parameters 4-WFRFT are designed to avoid a non-receiver’s intercepting and decoding. "Tracking coefficient" is defined to judge the anti-scanning capacity. The results of simulation show that the alterable-parameter 4-WFRFT secure communication system has strong practical significance.
A New Acquisition Structure with Frequency Offset Estimation For Impulse Radio Ultra Wide Band Signal
Xinyu Zhang,Xuejun Sha,Ali Nawaz Khan
Information Technology Journal , 2008,
Abstract: The influence of clock frequency offset between transmitter and receiver of IR UWB (Impulse Radio Ultra Wide Band) system is talked about in this study. Firstly, this study highlight the fact that clock frequency offset in UWB system will decrease the performance of the coherent receiver and then the necessity of frequency offset estimation before acquisition step is stated. To improve the acquisition failure situation caused by frequency offset, a new acquisition structure with frequency offset estimation, as well as a new method to estimate frequency offset, is proposed. The scheme employs the characteristics of the symmetry and linearity of correlation to approximate the frequency offset in a range of searching area and has good accuracy. As the simulation results reveal, the proposed acquisition structure with frequency offset estimation outperforms the traditional acquisition system and the acquisition failure caused by frequency offset is improved greatly.
A Variable Step Synchronization Acquisition Method for UWB Systems
Xinyu Zhang,Xuejun Sha,Ali Nawaz Khan
Information Technology Journal , 2008,
Abstract: The extremely narrow pulses with the order of nanoseconds and multipath in Time Hopping Ultra Wide Band system result in long mean acquisition time as well as low acquisition precision. A novel Variable Step Acquisition scheme, which aims to improve both mean acquisition time and acquisition precision, is proposed. The proposed acquisition scheme employs nonconsecutive search and adjusts searching steps according to several thresholds, which makes the acquisition process a fast acquisition with variable steps, i.e., from large steps to small ones. The mean acquisition time performances of the proposed scheme and conventional acquisition schemes are evaluated and compared. It is evident that proposed acquisition scheme significantly outperforms the conventional ones.
Determining Rate of Handoff for Irregularly Bounded Cellular Environments in Future Mobile Networks
Ali Nawaz Khan,Xuejun Sha,Xinyu Zhang
Information Technology Journal , 2008,
Abstract: In this study, we have presented and tested a method to calculate rate of handoff accurately by accounting for irregularities in cellular coverage area in next generation wireless and cellular communication networks. Traditionally, rate of handoff calculations are based on the assumption that cell boundaries can be represented by uniform geometrical shapes such as circle, square and hexagon. However, in real situations cell boundaries are irregular due to various signal-degradation factors and hence cannot be precisely represented by definite geometrical structures. The difference in calculated and measured values of rate of handoff introduces compounding error in probabilistic analysis of Next Generation Networks and hence, requires the multiplication of an appropriate correction factor with calculated rate of handoff to minimize the error. Extensive experimentation reveal that actual rate of handoff for a cellular environment is greater than the calculated rate by as much as 20% and is proportional to the degree of irregularity in the cell boundary.
A Truthful Auction based Incentive Framework for Femtocell Access
Sha Hua,Xuejun Zhuo,Shivendra S. Panwar
Computer Science , 2012,
Abstract: As cellular operators are suffering from a data explosion problem, and users are consequently experiencing poor data services, the introduction of femtocells offers a cost-effective way to mitigate this problem. Femtocells enable larger network capacity by increasing spatial reuse of the spectrum and shortening the distance to the users. Existing work has shown that open access femtocells, which allow unregistered macro users to connect, are efficient in reducing inter-cell interference and offloading traffic. However, a major obstacle constraining the potential capability of femtocells and open access is the lack of incentives for privately-owned femtocells to serve unregistered users. Hence in this paper, we propose a Vickrey-Clarke-Groves (VCG) auction based incentive framework for accessing such selfish femtocells. We consider two scenarios: One scenario involves a single macro user and another scenario has multiple macro users. We design auction schemes for both scenarios and show analytically that our schemes are truthful and have low computational complexity. Extensive simulations validate these properties and show huge performance improvement to the macro users.
Performance Study of Cooperative Diversity System over Nakagami-m Fading Channels
Jingning Wang,Xuejun Sha,Linan Sun,Zhongzhao Zhang
Information Technology Journal , 2009,
Abstract: In this study, a cooperative diversity scheme with decoded-and-forward plus amplify-and-forward is proposed by employing truncated stop-and-wait automatic repeat request for error control. All the transmission channels are assumed to exhibit Nakagami-m fading and the cross-layer performance is analyzed for the proposed scheme, such as the channel efficiency in physical layer, throughput and packet loss rate in link layer. The simulation results show that, the proposed scheme has the better cross-layer performance than other cooperative systems. By choosing a suitable partner, the proposed cooperative scheme can provide better performance than non-cooperative systems and spatial diversity gain can be obtained.
Auto Rate MAC Protocol Based on Congestion Detection for Wireless Ad Hoc Networks
Wei Wu,Zhongzhao Zhang,Xuejun Sha,Chenguang He
Information Technology Journal , 2009,
Abstract: Some auto rate protocols at the MAC layer have been proposed to improve the throughput of Ad Hoc networks with multiple rates support at physical layer. However, all of them neglect the influence of network congestion. The network performance will deteriorate as a result of transmitting data to a congested node. In this study, an auto rate protocol based on congestion detection called auto rate based on congestion detection (ARCD) is proposed. In the ARCD protocol, congestion level is detected at the receiving nodes and fed back to the sending nodes along with the rate selection information and then the sending nodes transmit a limited number of back-to-back packets at appropriate rates. The simulation results show that the ARCD protocol can not only improve the throughput and packet delivery ratio of Ad Hoc networks by taking full advantage of channel condition, but also achieve hop-by-hop congestion control.
A Multi-radio Packet Scheduling Algorithm for Real-time Traffic in a Heterogeneous Wireless Network Environment
Yang Cui,Yubin Xu,Rongqing Xu,Xuejun Sha
Information Technology Journal , 2011,
Abstract: The integration of heterogeneous wireless network has become an overwhelming tendency. So, it is a huge challenge for the network designers that how to manage resource in these access networks with different Radio Access Technologies (RATs) in a cooperative mode. As a feasible scheme, Generic Link Layer (GLL) is introduced. In this study, a novel multi-radio packet scheduling algorithm, is proposed for real-time traffic. There are four outstanding contributions in QU. First, in order to guarantee Quality of Service (QoS) of real-time traffic and avoid wasting resource, a scheduling utility function is developed to represent the degree of satisfaction of performing a packet scheduling in term of avoiding wasting resource provided that guaranteeing QoS. Second, using this utility function, a packet scheduling model, which in fact is a NP problem, is designed and analyzed based on joint consideration of fairness. Third, for improving execution rate, Hopfield Neural Network (HNN) is used to fast find an optimal solution for the scheduling model. Final, simulation is set up and is compared with M-LWDF and PLR algorithms to evaluate performance of QU algorithm. Simulation results show that under high load QU algorithm has lower packet loss ratio and higher spectrum efficiency while offers allowable average packet delay.
The Influence of Entrepreneurial Social Responsibility on the Strategic Decision-Making Process  [PDF]
Yanfei Sha
iBusiness (IB) , 2013, DOI: 10.4236/ib.2013.51B010
Abstract: Entrepreneurs manage enterprise strategic decision. Owing to low quality decision,entrepreneurs bring serious problems to the society. The corporate social responsibility has been rising, and it also has influenced the entrepreneurs' decision environment. This paper refines the deep influence factors of  strategic quality and analyzes the influence mechanism of entrepreneurial social responsibility on the strategic decision-making. The results show that high cognition and sense of entrepreneurial social responsibilitycan enhance the quality of enterprise strategic decision. So enterprise can get understanding and supporting from stakeholders.
Application of Moral Investment of Enterprise in Constructing Harmonious Society  [PDF]
Sha Yanfei
iBusiness (IB) , 2013, DOI: 10.4236/ib.2013.51B011
Abstract: The enterprise is the mainbody of the construction of harmonious society. The pivot to construct the harmonious society is to increase the moral investment.The moral investment should be operational and it can be done in three steps. The first step is to form the moral view. The second step is to make the decision on morality. The last step is to grip the moral carrier.
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