Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 4 Articles
An efficient channel sounding method using cellular communication systems is proposed for high-speed railway\r\n(HSR) propagation environments. This channel measurement technique can be used conveniently to characterize\r\ndifferent HSR scenarios, which can significantly improve the measurement efficiency. Based on downlink signals of\r\nwideband code division multiple access (WCDMA) and the long term evolution (LTE), principles and methodologies of\r\nHSR channel sounding are presented. Using the WCDMA signal, a measurement campaign is conducted in real-world\r\nHSR scenarios and statistical characterizations are provided using a radio network analyzer. Due to the limits of the\r\nradio network analyzer, afterwards, a software defined radio (SDR)-based channel data recorder is developed allowing\r\nusers to collect the signals from different wireless cellular systems. Especially, the estimation accuracies are validated\r\nin lab by the faded signals emitted from a vector signal generator. The results show that the channel data recorder\r\nprovides a particularly good match to the configured fading channels. Therefore, this measurement method can be\r\nemployed to investigate the HSR channel, and to establish the channel models under the various HSR scenarios....
Transmission Control Protocol (TCP) is the most\r\nreliable protocol. That was previously introduced for wired\r\nnetworks only. Lately the TCP started to act poorly for\r\nseveral factors due to the advent of wireless network. The\r\nrepresented factors which need to be addressed are recovery\r\nmechanism, backup mechanism, mobility, congestion\r\nwindow and maximum packet size. Based on existing\r\nvariants, new were introduced. The most two debated\r\nvariants are Vegas and Westwood which motivated many\r\nresearches. However, the number of studies proved that\r\nVegas could perform more efficiency than other variants\r\nduring the congested network whereas Westwood could\r\nconsume less bandwidth. Hence, in our previous\r\npublications, we already proved by integrating some features\r\nof Vegas and Westwood to get better and more stable\r\nvariant even in high congested network. It is called TCP\r\nUniversity of Bridgeport (TCP-UB). Based on a previous simulation, TCP-UB proved a high\r\nefficiency, less bandwidth consumption and stability from\r\nstatic and mobility point of view. Therefore, in this paper\r\nwe are using NS2 simulator to perform TCP-UB over\r\nwireless mesh network supported with manhattan mobility\r\nmodel. It provides robust and faster transmission service\r\namong several police stations in Connecticut, USA.\r\nFurthermore, we are comparing TCP-UB with Vegas and\r\nWestwood from a static and mobility point of view based on\r\nbandwidth consumption and congestion window scenario.\r\nOn the basis of findings, we validate that TCP-UB is also\r\nbetter performer even over wireless mesh network.....
The affine Fourier transform (AFT), a general formulation of chirp transforms, has been recently proposed for use in multicarrier\r\ncommunications. The AFT-basedmulticarrier (AFT-MC) system can be considered as a generalization of the orthogonal frequency\r\ndivision multiplexing (OFDM), frequently used in modern wireless communications. AFT-MC keeps all important properties\r\nof OFDM and, in addition, gives a new degree of freedom in suppressing interference caused by Doppler spreading in timevaryingmultipath\r\nchannels.We present a general interference analysis of the AFT-MC system that models both time and frequency\r\ndispersion effects. Upper and lower bounds on interference power are given, followed by interference power approximation that\r\nsignificantly simplifies interference analysis. The optimal parameters are obtained in the closed form followed by the analysis of\r\nthe effects of synchronization errors and the optimal symbol period. A detailed interference analysis and optimal parameters are\r\ngiven for different aeronautical and land-mobile satellite (LMS) channel scenarios. It is shown that the AFT-MC system is able to\r\nmatch changes in these channels and efficiently reduce interference with high-spectral efficiency....
Despite the effects of the diffusion of Information\r\nand Communication Technologies (ICT) on\r\nsocio-economic changes that are not yet fully identified,\r\nit is now recognized that ICT alter substantially\r\nour ways of communicating, learning and producing.\r\nIn addition to this, the controversy, that gave rise to\r\nthe concept of ââ?¬Âinformation-societyââ?¬Â, embodies these\r\ndevelopments which foreshadow new forms of social organization\r\nstructured around computer networks and\r\ntelecommunications. ICT increasingly aware of the developments\r\nidentified, and are introduced in all sectors.\r\nThis use has made these technological tools a requirement\r\nfor all countries which is likely to help them face\r\nup to the challenges ahead. In recent years our country\r\nââ?¬ÂMoroccoââ?¬Â has embarked on an ambitious program for\r\nthe widespread use of ICT integration in the System\r\nof Education and Training. In this paper, we propose\r\na strategy to follow in teaching students specific subjects\r\nand a training program for teachers both at the\r\nFaculties of Humanities as well as at that of the socioeconomic\r\nstudies; the ultimate purpose being to achieve\r\nthe integration of ICT in the Moroccan Educational\r\nSystem and Scientific research in general. To conclude we will post the outlook for evaluation of educational\r\nICT....
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