Mobile satellite propagation measurements and modeling: A review of results for systems engineers

An overview of Mobile Satellite Service (MSS) propagation measurements and modeling is intended as a summary of current results. While such research is on-going, the simple models presented here should be useful to systems engineers. A complete summary of propagation experiments with literature references is also included

Mobile satellite propagation measurements and modeling: A review of results for systems engineers

An overview of Mobile Satellite System (MSS) propagation measurements and modeling is given, including a summary of results. The simple models presented should be of some use to systems engineers. A complete summary of propagation experiments with literature references is included

Outage analysis in wireless channels with multiple interferers subject to shadowing and fading using a compound pdf model

International Journal of Electronics and Communications, 61(4): pp. 255-261.Wireless communication systems are subject to short term and long term fading of the channel. Instead of the commonly used Nakagami-lognormal model to account for the conditions existing in these shadowed fading channels, a compound probability density function (pdf) model is used to evaluate the performance of wireless systems. While the Nakagami-lognormal lacks a closed form solution to the pdf of the received power in shadowed fading channels, the compound pdf has an analytical expression for the pdf of the received signal power. The synergy between these two models for the analysis of wireless systems is explored by calculating the bit error rate in a DPSK modem as well as the outage probability in a wireless system in a shadowed fading channel. This is followed by the computation of the outage probability in the general case where both the desired and cochannels are subject to shadowing and fading. The analyses were carried out for both fixed number of cochannels and random number of cochannels. Results demonstrate the usefulness of the compound pdf model for the performance analyses of wireless systems in shadowed fading channels

OPTIMIZING RADIO RESOURCE MANAGEMENT IN VERY BAD CHANNEL CONDITIONS

Radio resource management is one of the most important parts of modern multi-user wireless communication systems. The main reason for this importance comes from the fact that the radio resources, such as bandwidth and power, are scarce. For instance, UMTS systems use 5MHz bandwidth for voice as well as data services. The optimum usage of the radio resource guarantees the highest efficient utilization of wireless networks. To optimize the radio resources, the transmitters need to estimate the channel conditions. This channel estimation is done by using pilot signal from the receiver. There are usually small delays between the measurements and the radio resource allocation. When the channel is highly correlated, this delay will not affect the performance, because the channel will not be significantly changed between the time of measurement and the time of transmission. However, if the mobile speed is high or the channel is very high dynamic, the correlation becomes very low. This is due to the timevarying nature of the channel. We call channels with very low correlation in time as bad condition channels. In this thesis we discuss this extremely important topic. The tools for analyzing bad condition channels are also proposed and discussed. Two power control algorithms to mitigate the low correlation of channels have been proposed. Our algorithms are validated through several simulations.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Power control in multimedia CDMA cellular networks.

Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.Wireless mobile communication is witnessing a rapid growth in, and demand for, improved technology and range of information types and services. Further, third generation cellular networks are expected to provide mobile users with ubiquitous wireless access to a global backbone architecture that carries a wide variety of electronic services. We examine the topic of power control and models that arc suitable for modem third generation wireless networks. CDMA technology is proving to be a promising and attractive approach for spectrally efficient, economical and high quality digital communications wireless networks. This thesis addresses the challenge of integrating heterogeneous transmitting sources with a broad range of Quality of Service characteristics in the cellular COMA networks. Provided the right power control can be devised, COMA offers the potential of extracting gain from the statistical multiplexing of such sources. A distributed power control algorithm is proposed which is required to update the transmitted power of the mobiles in each of the service classes locally. and enhance the performance of the system significantly. Algorithms for pragmatic issues like power level quantization and truncation of power are derived and incorporated into the proposed distributed power control algorithm

Adaptive radio resource management for mobile satellite systems

Word processed copy.Includes bibliographical references (leaves 89-99).In this thesis, a set of unique strategies and enhanced schemes for adaptive CDMA modulation are devised. A graded resource system is proposed for better radio resource management. Subsequently, a successful adaptive CDMA algorithm is designed and a prioritised processing gain for adaptive CDMA algorithm in satellite system is introduced. The idea of the critical section in the downlink system when a user controller scheme has to be activated to improve the performance is initiated. The diversity technique and rate compatible punctured turbo-code (RCPT), which has been found to give improved throughput performance in a direct sequence (DS) CDMA, are exploited

Ionospheric scintillation studies

The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work