Fernando Perez-Fontan

Bio: Fernando Perez-Fontan is an academic researcher from University of Vigo. The author has contributed to research in topics: Communication channel & Multipath propagation. The author has an hindex of 15, co-authored 102 publications receiving 916 citations.

Versatile two‐state land mobile satellite channel model with first application to DVB‐SH analysis

Abstract: Standardization activities on Digital Video Broadcasting–Satellite services to Handheld Devices (DVB-SH) have driven the need for a consolidated Land Mobile Satellite (LMS) narrowband channel model. In the DVB-SH system, the satellite broadcasts a signal carrying multimedia services aimed directly to a variety of mobile (handheld or vehicular) and fixed terminals. A three-state LMS channel model that describes the narrowband propagation channel in three possible shadowing states—line-of-sight conditions, moderate shadowing and deep shadowing—had been selected as a baseline for physical layer simulation of the DVB-SH waveform. This type of model, capable of generating complex time series, was originally selected, because it is the simplest model that allows the simulation of first- and second-order effects of the LMS channel in a realistic manner. The main limitations of such model are, first of all, that a classification in three states does not necessarily correspond with reality and, secondly, that the statistical parameters for each state were fixed for a given scenario and elevation angle. Those limitations may impact the selection of Physical Layer parameters of the DVB-SH standard. A new channel model is proposed based on the original three-state model including two major modifications: a reduction in the number of states and the introduction of a versatile selection of statistical parameters describing each state. Furthermore, the state machine is governed either by Markov or by semi-Markov chains. The new-state classification does not necessarily correspond to intuitive physical definitions of the states as before (line-of-sight, shadowing) but instead to channel variations that share similar statistical characteristics. The two-states are termed for convenience, Good and Bad states, representing a range of LOS-to-moderate shadowing and moderate-to-deep shadowing, respectively. For the model parameters selection, datasets at L- and S-band have been analysed using an iterative algorithm that includes automatic data classification and parameter extraction. The proposed model is considered more suitable for the analysis of DVB-SH test cases. This study starts with an overview of the main DVB-SH system parameters and assumptions. The original three-state model is briefly introduced; the new model is presented in detail, including simulator implementation. Finally, both models and experimental data sets are compared on a statistical basis. The performance of both models are discussed to show how effective the model is for the representation of shadowed conditions and therefore, its suitability for the analysis and optimal configuration of the physical and link layer parameters (namely physical layer interleaver size, link layer protection time, overall redundancy, etc.). Copyright © 2010 John Wiley & Sons, Ltd.

S-band LMS propagation channel behaviour for different environments, degrees of shadowing and elevation angles

Abstract: Experimental land mobile satellite (LMS) propagation data have been processed in order to characterise the behaviour of this channel under narrow-band transmission conditions for different environments, degrees of shadowing and elevation angles. Measurements were carried out at S-band. The transmitter was located on a small plane flying parallel to the road with elevations ranging from 40/spl deg/ to 80/spl deg/. For the analysis of the received amplitude series, they were classified for each environment and elevation angle, into three different states according to the degree of shadowing experienced. This was done in order to develop a Markov chain based propagation simulator. The global (slow+fast) signal variations within each state are modelled using the Loo distribution (Rice+log-normal). Average distribution parameter values for each state, elevation angle and environment type are reported. The average state probabilities, slow variations' correlation lengths and other parameters are also presented. Finally, a software implementation is described based on a Markov chain+Loo distribution model that is capable of reproducing the complex envelope variations in the received signal due to shadowing and multipath.

Detection and Tracking of Mobile Propagation Channel Paths

Abstract: In dynamic channel sounder measurements with a moving receiver and/or moving transmitter, propagation paths' parameters show a time-variant behavior. This paper describes a novel algorithm which is able to both detect individual propagation paths and track how these paths evolve with time. The proposed algorithm is capable of estimating the paths' parameters and outperforms the standard snapshot-based algorithm in cases where low accuracy due to resolution limitations in the delay or angular domain is observed. An example based on channel sounder measurements with a moving receiver is given, showing that the algorithm is able to capture the dynamic behavior of the propagation channel.

Shadowing correlation assessment and modeling for satellite diversity in urban environments

Abstract: Non-geostationary orbit satellite networks have dynamic, yet deterministic topologies. This paper deals with the consequences of relying on the use of multiple visible satellites to improve availability with time/locations through satellite diversity techniques. The assumption of independent blockage events in two different satellite-to-mobile links is generally not accurate and information on shadowing correlation should be taken into account in the assessment of availability.In this paper a shadowing correlation study for urban environments is presented and a model for the real environments, as well as for a generic urban environment is inferred. The model proposed here is simple and can be run on a computer. It also relates urban and constellation geometries thus allowing the identification of those cases for which satellite diversity gain should be expected. As a result of this analysis and modelling, we present empirical analytical expressions describing positive correlation coefficient as a function of satellite angular separation (azimuth and elevation). We also show that an angle exists above which correlation can be negative and satellite diversity can sensibly improve link availability. Copyright © 2002 John Wiley & Sons, Ltd.

Characterization of the aeronautical satellite navigation channel through high-resolution measurement and physical optics simulation

Abstract: In this paper we discuss the results of a measurement campaign investigating the environment of satellite navigation receivers for aeronautical applications, where reflections on the plane as well as from the ground decrease the accuracy of the positioning. The focus is on the most critical flight phase—the final approach. For this scenario a wideband model is derived, which allows to investigate the performance of present and future global navigation satellite systems. The work was carried out under an European Space Agency contract (ESTEC Contract number 16059/02/NL/DS) entitled ‘Navigation signal measurement campaign for critical environments’, by Joanneum Research (Austria) with subcontracts to DLR (Germany) and the University of Vigo (Spain). Copyright © 2007 John Wiley & Sons, Ltd.

A new simple model for land mobile satellite channels: first- and second-order statistics

Abstract: We propose a new shadowed Rice (1948) model for land mobile satellite channels. In this model, the amplitude of the line-of-sight is characterized by the Nakagami distribution. The major advantage of the model is that it leads to closed-form and mathematically-tractable expressions for the fundamental channel statistics such as the envelope probability density function, moment generating function of the instantaneous power, and the level crossing rate. The model is very convenient for analytical and numerical performance prediction of complicated narrowband and wideband land mobile satellite systems, with different types of uncoded/coded modulations, with or without diversity. Comparison of the first- and the second-order statistics of the proposed model with different sets of published channel data demonstrates the flexibility of the new model in characterizing a variety of channel conditions and propagation mechanisms over satellite links. Interestingly, the proposed model provides a similar fit to the experimental data as the well-accepted Loo's (1985) model but with significantly less computational burden.

Space-Air-Ground Integrated Network: A Survey

Abstract: Space-air-ground integrated network (SAGIN), as an integration of satellite systems, aerial networks, and terrestrial communications, has been becoming an emerging architecture and attracted intensive research interest during the past years. Besides bringing significant benefits for various practical services and applications, SAGIN is also facing many unprecedented challenges due to its specific characteristics, such as heterogeneity, self-organization, and time-variability. Compared to traditional ground or satellite networks, SAGIN is affected by the limited and unbalanced network resources in all three network segments, so that it is difficult to obtain the best performances for traffic delivery. Therefore, the system integration, protocol optimization, resource management, and allocation in SAGIN is of great significance. To the best of our knowledge, we are the first to present the state-of-the-art of the SAGIN since existing survey papers focused on either only one single network segment in space or air, or the integration of space-ground, neglecting the integration of all the three network segments. In light of this, we present in this paper a comprehensive review of recent research works concerning SAGIN from network design and resource allocation to performance analysis and optimization. After discussing several existing network architectures, we also point out some technology challenges and future directions.

A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles

Abstract: In recent years, there has been a dramatic increase in the use of unmanned aerial vehicles (UAVs), particularly for small UAVs, due to their affordable prices, wide availability, and relative ease of operability. Existing and future applications of UAVs include remote surveillance and monitoring, relief operations, package delivery, and communication backhaul infrastructure. Additionally, UAVs are envisioned as an important component of 5G wireless technology and beyond. The unique application scenarios for UAVs necessitate accurate air-to-ground (AG) propagation channel models for designing and evaluating UAV communication links for control/non-payload as well as payload data transmissions. These AG propagation models have not been investigated in detail, relative to terrestrial propagation models. In this paper, a comprehensive survey is provided on available AG channel measurement campaigns, large and small scale fading channel models, their limitations, and future research directions for UAV communication scenarios.

Satellite Communications in the New Space Era: A Survey and Future Challenges

Abstract: Satellite communications (SatComs) have recently entered a period of renewed interest motivated by technological advances and nurtured through private investment and ventures. The present survey aims at capturing the state of the art in SatComs, while highlighting the most promising open research topics. Firstly, the main innovation drivers are motivated, such as new constellation types, on-board processing capabilities, non-terrestrial networks and space-based data collection/processing. Secondly, the most promising applications are described, i.e., 5G integration, space communications, Earth observation, aeronautical and maritime tracking and communication. Subsequently, an in-depth literature review is provided across five axes: i) system aspects, ii) air interface, iii) medium access, iv) networking, v) testbeds & prototyping. Finally, a number of future challenges and the respective open research topics are described.

Statistical modeling of the LMS channel

Abstract: In this paper, a statistical model for the land mobile satellite (LMS) channel is presented. The model is capable of describing both narrow- and wide-band conditions. The other relevant characteristic is that it can be used to study links with geostationary as well as nongeostationary satellites. The model is of the generative type, i.e., it is capable of producing time series of a large number of signal features: amplitudes, phases, instantaneous power-delay profiles, Doppler spectra, etc. Model parameters extracted from a comprehensive experimental data bank are also provided for a number of environments and elevation angles at L-, S-, and Ka-bands.