Athanasios D. Panagopoulos

Satellite communications at KU, KA, and V bands: Propagation impairments and mitigation techniques

This article surveys the alternative fade mitigation techniques for satellite communication systems operating at Ku, Ka and V frequency bands. The specific phenomena influencing the propagation of radiowaves on Earth-space links are also overviewed. Emphasis is placed on modeling, experimental work carried out in the past, and practical implementations related to each mitigation technique.

MIMO over Satellite: A Review

The present article carries out a review of MIMO-based techniques that have been recently proposed for satellite communications. Due to the plethora of MIMO interpretations in terrestrial systems and the particularities of satellite communications, this review is built on two pillars, namely fixed satellite and mobile satellite. Special attention is given to the characteristics of the satellite channel, which will ultimately determine the viability of MIMO over satellite. Finally, some future research directions are identified.

A survey on game theory applications in wireless networks

While the Quality of Service (QoS) offered to users may be enhanced through innovative protocols and new technologies, future trends should take into account the efficiency of resource allocation and network/terminal cooperation as well. Game theory techniques have widely been applied to various engineering design problems in which the action of one component has impact on (and perhaps conflicts with) that of any other component. Therefore, game formulations are used, and a stable solution for the players is obtained through the concept of equilibrium. This survey collects applications of game theory in wireless networking and presents them in a layered perspective, emphasizing on which fields game theory could be effectively applied. To this end, several games are modeled and their key features are exposed.

A survey of architectures and scenarios in satellite‐based wireless sensor networks: system design aspects

This paper is not a survey related to generic wireless sensor networks (WSNs), which have been largely treated in a number of survey papers addressing more focused issues; rather, it specifically addresses architectural aspects related to WSNs in some way connected with a satellite link, a topic that presents challenging interworking aspects. The main objective is to provide an overview of the potential role of a satellite segment in future WSNs. In this perspective, requirements of the most meaningful WSN applications have been drawn and matched to characteristics of various satellite/space systems in order to identify suitable integrated configurations. Copyright

On the rain attenuation dynamics: spatial-temporal analysis of rainfall rate and fade duration statistics

Knowledge about the dynamic characteristics of rain attenuation is of utmost importance for many applications in terrestrial and satellite communication systems operating at frequencies above 10 GHz. Long-term rain rate statistics and rain rate duration statistics are usually available from meteorological data. In this paper, a spatial–temporal analysis is employed in order to evaluate the rain attenuation power spectrum of a terrestrial/satellite path. The predicted power spectrum is compared with experimental data. Based on the spectral analysis of rainfall rate a method for converting rain rate duration statistics to link fade duration statistics is also proposed. Fade duration statistics are presented for terrestrial and satellite links and compared with available experimental data. The agreement between the predicted results and the experimental data has been found to be quite encouraging. Finally, numerical results are presented for various climatic zones, elevation angles and frequencies. Some very useful conclusions concerning the dynamic properties of rain attenuation for a microwave path are deduced. Copyright

Long-term rain attenuation probability and site diversity gain prediction formulas

Simple models for long-term induced rain attenuation on a slant path and site diversity gain are presented in this work. As verified by numerous tests against the ITU-R databank and other data from the literature, the proposed models exhibit a very good performance. The novel slant path rain attenuation prediction model compared to the ITU-R one exhibits a similar behavior at low time percentages and a better root-mean-square error performance for probability levels above 0.02%. Moreover, comparing the proposed site diversity gain model with other widely accepted models from the literature, an improved performance is observed for distances less than 15 km, while the model performs equally well for greater distances. Furthermore, a sensitivity test between the proposed and Hodges formula with respect to the separation distance D is also carried out. While the lower limit of the proposed model is found to be D=1.7 km, its extension covering large-scale site diversity is successfully compared with experimental data coming from Japan. The set of presented models exhibits the advantage of easy implementation with little complexity and is considered useful for educational and back of the envelope computations.

Multi-satellite MIMO communications at Ku-band and above: investigations on spatial multiplexing for capacity improvement and selection diversity for interference mitigation

This paper investigates the applicability of multiple-input multiple-output (MIMO) technology to satellite communications at the Ku-band and above. After introducing the possible diversity sources to form a MIMO matrix channel in a satellite environment, particular emphasis is put on satellite diversity. Two specific different topics from the field of MIMO technology applications to satellite communications at these frequencies are further analyzed: (i) capacity improvement achieved by MIMO spatial multiplexing systems and (ii) interference mitigation achieved by MIMO diversity systems employing receive antenna selection. In the first case, a single-user capacity analysis of a satellite MIMO spatial multiplexing system is presented and a useful analytical closed form expression is derived for the outage capacity achieved. In the second case, a satellite MIMO diversity system with receive antenna selection is considered, adjacent satellite cochannel interference on its forward link is studied and an analytical model predicting the interference mitigation achieved is presented. In both cases, an appropriate physical MIMO channel model is assumed which takes into account the propagation phenomena related to the frequencies of interest, such as clear line-of-sight operation, high antenna directivity, the effect of rain fading, and the slant path lengths difference. Useful numerical results obtained through the analytical expressions derived are presented to compare the performance of multi-satellite MIMO systems to relevant single-input single-output (SISO) ones.

Power Allocation in Cognitive Satellite Terrestrial Networks with QoS Constraints

The increasing demand for high-speed multimedia services and the underutilization of scarce satellite spectral resources have recently led the researchers to propose the concept of cognitive satellite terrestrial networks. Considering this novel architecture, we propose an efficient resource management mechanism for the terrestrial network that acts as the secondary system. We introduce a new power allocation algorithm that optimizes the effective capacity of the terrestrial link for given Quality of Service (QoS) requirements while guaranteeing a specified outage probability for the satellite link. Both perfect and imperfect channel estimation cases are considered in the power allocation scheme and analytical results are presented. Numerical calculations evaluate the performance of the proposed scheme.

Intercell Radio Interference Studies in Broadband Wireless Access Networks

Capacity has become of primary importance in broadband wireless access (BWA) networks due to the ever-increasing demand for multimedia services and the possibility of providing wireless Internet, leading to their standardization by IEEE (802.16 WirelessMAN) and ETSI (BRAN HIPERACCESS). The major factor limiting capacity in such systems is interference originating from adjacent cells, namely intercell interference. This paper presents a general analysis of intercell interference for a spectrally efficient BWA cellular configuration. It examines the statistical properties of the carrier-to-interference ratio in both downstream and upstream channels. The focus is on the spatial inhomogeneity of rain attenuation over multiple paths, which is the dominant fading mechanism in the frequency range above 20 GHz, especially when two-layered [i.e., line-of-sight (LOS) and non-LOS] architectures are involved. Besides attenuation from precipitation, various architectural and propagation aspects of local multipoint distribution service systems are investigated through simulations, and worst-case interference scenarios are identified

Statistics of differential rain attenuation on converging terrestrial propagation paths

Rain attenuation is considered to be one of the main causes of interference impairments for terrestrial communication systems operating at frequencies above 10 GHz. A method to predict the cumulative distribution of differential rain attenuation on two converging microwave links is proposed. It is based on a convective raincells model for the structure of the rainfall medium, as well as the lognormal assumption for the point rainfall distribution. The degradation of the carrier-to-interference ratio under rainy conditions is also examined. Numerical results are compared with a set of available experimental data for the differential rain attenuation over pairs of terrestrial links in Brazil.