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Mobile Satellite Channel (mobile + satellite_channel)
Selected AbstractsAdaptive predistortion of COFDM signals for a mobile satellite channelINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2003Nibaldo Rodriguez Abstract In this paper, we consider the optimization of the performance of QPSK and 16-QAM coded orthogonal frequency division multiplexing (COFDM) signals over the non-linear and mobile satellite channel. A high power amplifier and Rician flat fading channel produces non-linear and linear distortions; an adaptive predistortion technique combined with turbo codes will reduce both types of distortion. The predistorter is based on a feedforward neural network, with the coefficients being derived using an extended Kalman filter (EKF). The conventional turbo code is used to mitigate Rician flat fading distortion and Gaussian noise. The performance over a non-linear satellite channel indicates that QPSK COFDM followed by a predistorter provides a gain of about 1.7 dB at a BER of 3×10,3 when compared to QPSK COFDM without the predistortion scheme and 16-QAM COFDM provides a gain of 0.5 dB output back-off and 1.2 dB signal to noise ratio at a BER of 3×10,5 when compared with an adaptive predistorter based on the Harmmerstein model. We also investigate the influence of the guard time interval and Doppler frequency effect on the BER performance. When the guard interval increases from 0 to 0.125T samples and the normalized Doppler frequency is 0.001, there is a gain of 0.7 and 1 dB signal to noise ratio at a BER of 6×10,4 for QPSK and 16-QAM COFDM, respectively. Copyright © 2003 John Wiley & Sons, Ltd. [source] Performance of a turbo-coded CDMA system in a mobile satellite channelINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2005Jin Young Kim Abstract The bit error rate (BER) performance of a turbo-coded code-division multiple-access (CDMA) system operating in a satellite channel is analysed and simulated. The system performance is compared for various constituent decoders, including maximum a posteriori probability (MAP) and Max-Log-MAP algorithms, and the soft-output Viterbi algorithm. The simulation results indicate that the Max-Log-MAP algorithm is the most promising among these three algorithms in overall terms of performance and complexity. It is also shown that, for fixed code rate, the BER performance is improved substantially by increasing the number of iterations in the turbo decoder, or by increasing the interleaver length in the turbo encoder. The results in this paper are of interest in CDMA-based satellite communications applications. Copyright © 2005 John Wiley & Sons, Ltd. [source] A new multi-state fading model for mobile satellite channels based upon AFD and LCR data,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2004David W. Matolak Abstract Using measured data on average fade duration (AFD) and level crossing rate (LCR), we obtain new analytical expressions for the probability density function (pdf) of received signal envelope in a mobile satellite channel, via a new method. The measured data for an urban environment comes from Kanatas et al. Proceedings of the 1997 International Mobile Satellite Conference, Pasadena, CA, 16,18 June, 1997; 169,175, but the new method is general in nature and can be applied to other environments. The method is less direct than curve-fitting to a histogram of the ,raw' measured fading amplitude data, but is comparable in complexity and yields good results. Our new model is a composite one, similar to other composite models given in the literature, e.g. the Loo and Lutz models, but in contrast to these, the new model affords a completely closed-form expression for the pdf. As with these other composite models, the new model is amenable to the development of computer simulations of mobile satellite channel amplitude time series realizations, and can be combined with state transition models to provide a complete multi-state fading model. Copyright © 2004 John Wiley & Sons, Ltd. [source] Efficient repair mechanism of real-time broadcast services in hybrid DVB-SH and cellular systemsBELL LABS TECHNICAL JOURNAL, Issue 1 2009Bessem Sayadi In order to ensure good video quality and location-independent access to multimedia content, digital video broadcasting-satellite service to handhelds (DVB-SH) takes advantage of several innovative techniques. The major one is the forward error correction (FEC) scheme implemented at the link layer called multiprotocol encapsulation-inter-burst FEC (MPE-IFEC). MPE-IFEC supports reception in situations of long duration erasure spanning several consecutive time slice bursts (lasting several seconds) due to characteristics of the land mobile satellite channel which are easily hampered by obstacles such as trees, buildings, or overpasses. However, when deep signal fades last for larger durations, the MPE-IFEC correction capacity is insufficient and MPEIFEC fails, causing a service interruption. In this paper , we propose a repair mechanism and a suitable architecture for real-time streaming service error handling with reduced degrading effects such as picture freeze, video frame degradation, and video lag. Based on an analytical model of the performance of the MPE-IFEC, an iterative algorithm is proposed where the probability of recovery of lost bursts is computed and updated. The proposed algorithm controls the retransmission request on the cellular network. Simulation results show that by recovering only some specific lost bursts via the cellular path, the quality of experience here expressed in terms of burst error rate is improved. © 2009 Alcatel-Lucent. [source] Performance of block-coded land mobile satellite systemsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2008Chang-Ming Lee Abstract Although various measurements have indicated that mobile satellite channels are not memoryless, most related coded system performance analysis assumes perfect interleaving is in place so that the effect of channel memory can be completely ignored. This paper presents a systematic method to accurately and efficiently predict the performance of errors-and-erasures or errors-only decoders for block-coded systems in general mobile satellite channels. Numerical results are provided to validate our analytic results. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new multi-state fading model for mobile satellite channels based upon AFD and LCR data,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2004David W. Matolak Abstract Using measured data on average fade duration (AFD) and level crossing rate (LCR), we obtain new analytical expressions for the probability density function (pdf) of received signal envelope in a mobile satellite channel, via a new method. The measured data for an urban environment comes from Kanatas et al. Proceedings of the 1997 International Mobile Satellite Conference, Pasadena, CA, 16,18 June, 1997; 169,175, but the new method is general in nature and can be applied to other environments. The method is less direct than curve-fitting to a histogram of the ,raw' measured fading amplitude data, but is comparable in complexity and yields good results. Our new model is a composite one, similar to other composite models given in the literature, e.g. the Loo and Lutz models, but in contrast to these, the new model affords a completely closed-form expression for the pdf. As with these other composite models, the new model is amenable to the development of computer simulations of mobile satellite channel amplitude time series realizations, and can be combined with state transition models to provide a complete multi-state fading model. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||