To estimate the mobile location is an important topic in wireless communication. It is well known that non-line-of-sight (NLOS) problem is the most pivotal part that causes the estimated error. When we transmit the signal from mobile station (MS) to base stations (BSs), the direct path between MS and BS is sealed off by some obstacles, and the signal measurements will measure the error due to the signal reflection or diffraction. The hybrid Taguchi-genetic algorithm (HTGA) combines the Taguchi method with the genetic algorithm (GA). In this paper, we bring up a novel HTGA algorithm that utilizes time of arrival (TOA) measurements from three BSs to locate MS. The proposed algorithm utilizes the intersections of three TOA circles based on HTGA to estimate the MS location. Finally, we compare HTGA with GA and find that the Taguchi algorithm can enhance genetic algorithm. We also can find that the average convergence of generation number will not be affected no matter which propagation models we use. Obviously HTGA is more robust, statistically sound, and quickly convergent than the other algorithms. The simulation results show that the HTGA can converge more quickly than GA and furthermore the HTGA can enhance the accuracy of the mobile location.

No abstract

File pollution is a recent security threat to peer-to-peer (P2P) file sharing systems. By disseminating numerous polluted files with mismatched or partially tampered contents in the P2P system, the attacker causes users to download unexpected files. This attack is aimed at frustrating users and making them abandon the system. Present researches on combating file pollution have mostly focused on pollution modeling or evaluating the extent of pollution. Only a few researches have proposed effective methods to eliminate pollution attacks, and they are primarily based on reputation systems and blacklisting mechanisms. However, these methods require exchange of significant feedback among the peers in order to identify the malicious peers or polluted files in the system. In this paper, we describe the application of fault-tolerant mechanism used in the redundant arrays of independent disks system to suppress file pollution attacks based on the concept that P2P file sharing systems currently have global file storage systems. We have extended the previously developed Fluid Model to analyze and evaluate the proposed antipollution mechanism. The model accuracy has been demonstrated by performing several simulation experiments; the proposed mechanism could effectively suppress the pollution and successfully decrease the polluted-time exposure of a P2P file sharing system by approximately 40∼60%.

Wireless location is to determine the position of the mobile station (MS) in wireless communication networks. Taylor series algorithm (TSA) is the most useful in linearizing the nonlinear equations. This paper develops hybrid positioning methods that utilize the time of arrival (TOA) and the angle of arrival (AOA) to locate the MS. TSA can give a location estimate of the MS in nonline-of-sight (NLOS) environments. The quality of the TSA estimate clearly depends critically on the initial MS location. The TSA has divergence problems when the initial estimate of the MS location is poor. To obtain the high performance of TSA, we proposed the initial MS location selection criterion. Simulation results indicate that the positioning accuracy of the proposed criterion is significantly improved.

Many mobile agent system-related services and applications require interacting with a mobile agent by passing messages. However, an agent’s mobility raises several challenges in delivering messages to a mobile agent accurately. Consisting of tracking and message delivery phases, most mobile agent location management schemes create or receive many update messages and interaction messages to ensure the effectiveness of the schemes. In addition to downgrading the overall performance of a mobile agent location management scheme, excessive transmission of messages increases the network load. The migration locality of a mobile agent and the interaction rate between mobile agents significantly affect the performance of a mobile agent location management scheme with respect to location management cost. This work presents a novel Dual Home based Scheme (DHS) that can lower the location management costs in terms of migration locality and interaction rate. While the DHS scheme uniquely adopts dual home location management architecture, a selective update strategy based on that architecture is also designed for cost-effective location management of mobile agents. Moreover, DHS is compared with available schemes based on formulations and simulation experiments from the perspective of location management costs. Simulation results demonstrate that the proposed DHS scheme performs satisfactorily in terms of migration locality and interaction rate.