José Mauro P. Fortes

Robust radar-embedded Sidelobe Level modulation using constrained optimization design

In this paper, we propose a robust radar-embedded Sidelobe Level (SLL) modulation for a communication system as a secondary task for a radar system. We propose an optimization formulation based on quadratic, point and first derivative constraints, which can efficiently generate K transmit beampatterns that match a desired transmit mainlobe output power profile and embed K different SLLs towards the communication receiver direction, while sustaining its amplitude over a small angular region. We present the optimal closed form solution to the above described problem. The implementation of the proposed solution is much simpler than the methods so far proposed for radar-embedded SLL communication literature. Simulation results show the good properties of the proposed technique: good mainbeam fit, good sidelobe behavior and a flat BER over the communication region.

On the power flux-density limits to protect the fixed service from HEO FSS satellites emissions in the 18 GHz band

This paper focuses on the protection of Fixed Service (FS) receivers from the aggregate interference produced by the satellites of multiple highly elliptical orbit satellite systems (HEOs). It analyzes the protection given to FS receivers operating in the 18 GHz frequency band by different power flux-density (pfd) masks. These masks establish the maximum allowable pfd produced by each HEO satellite at the Earths surface. The protections offered by four different pfd masks are analysed in two interfering environments, each containing three HEO systems. Two types of HEO system, with different orbital characteristics, are considered: one having satellites that operate only in the northern hemisphere and another having satellites that operate in both hemispheres. To reflect the multiplicity of possibilities concerning the geographical location and technical characteristics of the victim FS receiver (e.g. latitude, longitude, azimuth and elevation of its receiving antenna, antenna gain, receiver noise temperature, etc.) a large amount of results and curves is usually generated by the studies, making it difficult to draw general conclusions on the protection offered by the pfd masks under analysis. In looking for alternative ways of presenting the obtained results, a new variable was defined: the interference in excess. This new variable was defined in a way so that its probability distribution function reflects the protection given to an FS receiver located at a given latitude with a given receiving antenna elevation angle. It indicates the protection of an FS receiver for which the location longitude and the azimuth of the pointing direction of its receiving antenna are randomly chosen. This allows the large amount of results to be compacted into a small number of more representative curves from which general conclusions on the protection offered by the different pfd masks are easily drawn. Copyright

Satellite link performance under rain and external interferences: Constraints to be imposed on the statistical behavior of the external interferences

This paper concerns an environment in which several communication systems share a common frequency band and, therefore, each system operates subject to the interference generated by the others. More specifically, the paper addresses the problem of establishing the limits that should be imposed on the transmitted interfering signals so that all systems sharing the band are able to operate adequately and none of them experiences harmful interferences. This is a well-known problem for those working in the telecommunication regulation and standardization areas. Its solution requires studies and analysis that are usually complex and strongly depend on the technical characteristics of the systems involved. This paper presents a new technique that is able to determine, in a systematic way, the constraints to be imposed on the statistical behavior of the external interferences affecting a satellite link to guarantee that the link performance requirements are satisfied. The proposed technique considers the joint effect of the degradations due to rain and due to external interferences. In the method, a series expansion on the basis of orthonormal functions is used to represent the probability density function of the degradation due to external interferences and the limiting mask is obtained by solving a conveniently defined constrained optimization problem. The method is flexible enough to allow for the use of the rain attenuation models that are usually employed in link calculations. Two example applications are presented: one involving a satellite downlink in 19 GHz and the other an uplink in 29 GHz using power control. Copyright

Protection of FS receivers from the interference produced by HEO FSS satellites in the 18 GHz band: Effect of the roll-off characteristics of the HEO system satellite antenna beams

This paper focuses on the protection of fixed service (FS) receivers from the aggregate interference produced by the satellites of multiple highly elliptical orbit satellite systems (HEOs). It analyzes the protection given to FS receivers operating in the 18 GHz frequency band by the power flux-density (pfd) mask contained in Article 21 of the 2003 edition of the Radio Regulations [International Telecommunication Union, 2003.]. This mask establishes the maximum allowable value for the pfd produced by any of the satellites of a non-geostationary system at the Earths surface. The protection offered to FS receivers by this mask is analyzed in four interfering environments, each containing three identical HEO systems. Four types of HEO systems, with different orbital characteristics, are considered: three having satellites that operate only in the northern hemisphere and one having satellites that operate in both hemispheres. All satellite antennas are assumed to radiate 0.3° spot beams. Each HEO satellite is modelled so that the maximum pfd it produces at the Earths surface just meets the RR Article 21 mask and the analysis takes into account the roll-off characteristics of the satellite antenna beams. To reflect the multiplicity of possibilities concerning the geographical location and technical characteristics of the victim FS receiver (e.g. latitude, longitude, azimuth and elevation of its receiving antenna, antenna gain, receiver noise temperature, etc.) a number of cases were evaluated. The concept of interference in excess [Int. J. Satellite Commun. Networking 2006; 24: 73–95] was used to combine the results corresponding to FS receivers located at the same latitude and having the same receiving antenna elevation angle but for which the location longitude and the azimuth of the pointing direction of its receiving antenna are randomly chosen. Results are expressed in terms of the cumulative distribution function of the interference in excess. Copyright

Low-complexity robust radar-embedded Sidelobe Level modulation using linear constrained optimization design

In this paper, we propose a low-complexity robust radar-embedded Sidelobe Level (SLL) modulation for a communication system as a secondary task for the radar. The robust radar-embedded SLL modulation aims the generation of transmit beampatterns, that satisfactorily match a given transmit profile (with high fidelity adjustment at the mainlobe), where each beampattern embeds a different SLL towards the communication receiver direction and sustains its amplitude over a small angular region. We achieve these goals by modifying the robust SLL optimization problem enunciated in [1], in order to handle differently the mainlobe adjustment requirement. The proposed formulation is based on eigenvector, point and first derivative constraints. We derive its closed form solution and we simplify it through mathematical manipulation and eigenspectrum analysis. These procedures make the proposed solution suitable for online real-time processing. We also derive simple equations for updating the beampatterns for following a moving communication receiver platform.

Satellite interference evaluation: joint effect of modeling earth station locations and earth station antenna sidelobe gains as random variables

When several satellite communication systems share the same frequency band, each system operates under the aggregate interference generated by the others. In this interfering environment, interference calculation procedures in which worst-case situations and simplifying assumptions are considered are commonly used. Given that the geostationary satellite orbit and the frequency spectrum are limited resources, it is important to consider alternatives that lead to a more precise interference evaluation. One of these alternatives is the use of a probabilistic methodology, in which some of the parameters involved are modeled as random variables. This work considers the specific case in which the earth station geographic locations and the sidelobe gains of their antennas are modeled as random. Analytical expressions for the probability distribution function of the carrier to aggregate interference ratio are determined. The proposed methodology is applied to scenarios involving multiple multibeam satellite networks and the results are compared with those obtained with the usual deterministic procedure. Copyright

Impact of avoidance angle mitigation techniques on the interference produced by non-GSO systems in a multiple non-GSO interference environment

This paper adresses the impact of avoidance angle mitigation techniques on the interference produced by non-GSO systems in a multiple non-GSO interference environment. It considers a situation involving a victim LEO system and two other non-GSO interfering systems (one MEO and another LEO) that mitigate around (and only around) the victim LEO system. Interference statistics are obtained using the so called Analytical Method for non-GSO interference computations. The methodology described, including the interference model adopted, and the type of result obtained in Section 3, that shows the variation of the percentage of the total time allowance used by the interference as a function of the Earth station-based and the satellite-based avoidance angles, are very helpful in the process of selecting adequate values for these angles. The burden imposed on the mitigating systems by the use of avoidance angle strategies was evaluated through its impact on the coverage capability of the mitigating systems. Copyright

On the protection of fixed service receivers from the interference generated by non-GSO satellite systems operating in the 3.7-4.2 GHz band

Cunha Maia Nobre, Isabela; Pedro Fortes, José Mauro (Advisor). On the Protection of Fixed Service Receivers from the Interference Generated by Non-GSO Satellite Systems Operating in the 3.7-4.2 GHz Band. Rio de Janeiro, 2017. 70p. Dissertação de Mestrado – Centro de Estudos em Telecomunicações, Pontifícia Universidade Católica do Rio de Janeiro. In this work, the current power-flux density limits in Article 21 of the ITU-R Radio Regulations for non-GSO systems operating in the 3.7-4.2 GHz band are analyzed. These limits aim the protection of Fixed Service receivers, operating in the same frequency band, from the interference produced by non-GSO satellite systems. The analysis was motivated by Resolution 157 [1] of the World Radiocommunication Conference 2015, that recognized the need for a revision of Article 21 with a view to enabling non-GSO systems to operate in these FSS frequency bands while ensuring that existing primary services are protected. In the analysis, five different Walker Delta type satellite constellation structures, adequately chosen, were considered. Results have shown that the current pfd limits may impose undue constraints to non-GSO systems operating in this band. Therefore, a methodology to investigate a more adequate pfd limiting mask is presented. The application of this methodology leads to an alternative mask that approaches the current pfd limits for the geostationary satellites when the number of satellites in the non-GSO interfering system is equal to one. An evaluation of the proposed pfd mask shows that it does not impose unnecessary constraints to the non-GSO satellite systems. This, along with other facts, indicates that the proposed pfd limits are, indeed, much more adequate than the current ones.

Interpolation-and-decimation-based dimensionality reduction applied to space-time processing

In this paper, we specialize a novel stage of dimensionality reduction, based on a joint interpolation and decimation scheme (JIDS), proposed in [1] and [2], for airborne phased-array radars. The JIDS design approach consists of a very elegant and effective way to obtain the joint interpolation filter and decimation pattern, taking advantage of the correlation generated by the interpolation filter in order to eliminate samples and still achieve low signal to interference and noise ratio (SINR) loss. We compare its results in terms of probability of detection and Doppler performance with the full rank Minimum Variance Distortionless Response sample matrix inversion (MVDR-SMI) space-time filter and other rank reduction techniques such as Principal Components (PC), Cross-Spectral Metric (CSM) and Multistage Wiener Filter (MWF). Simulation results show that the proposed approach has an impressive ability to significantly reduce the length of the space-time snapshots and achieves very good performance in Doppler SINR loss and probability of detection, especially in sample starving scenarios.

On the interference from space research service uplink transmissions into the inter-satellite links of a non-GSO system operating in the 22-GHz band

SUMMARY This paper presents a compatibility analysis involving space research service lunar mission uplink transmissions and the inter-satellite links of non-geostationary orbit systems operating in the 22-GHz band. Three points differentiate this analysis from the currently available studies: (1) the mathematical model used here allows for the consideration of the time varying nature of the inclination of the Moon orbital plane; (2) besides the usual unconditional interference cumulative distribution functions, this analysis also considers the conditional cumulative distribution functions given that the victim satellite is receiving interference, important to characterize the interference affecting users that, because of their location, are most of the time using satellites, which are under interference; and (3) instead of dynamic time simulation, the analytical method in Recommendation ITU-R S.1529 is used to determine the various cumulative distribution functions involved. Four scenarios are examined in the paper. Their main differences concern the number and location of the space research service transmitting Earth stations and the strategy under which they are active (transmitting). In all scenarios, cumulative distribution functions of the ratio I/N were determined for both the in-band and the out-of-band interference cases. Copyright