Enzo Alberto Candreva

LTE adaptation for mobile broadband satellite networks

One of the key factors for the successful deployment of mobile satellite systems in 4G networks is the maximization of the technology commonalities with the terrestrial systems. An effective way of achieving this objective consists in considering the terrestrial radio interface as the baseline for the satellite radio interface. Since the 3GPP Long Term Evolution (LTE) standard will be one of the main players in the 4G scenario, along with other emerging technologies, such as mobile WiMAX; this paper analyzes the possible applicability of the 3GPP LTE interface to satellite transmission, presenting several enabling techniques for this adaptation. In particular, we propose the introduction of an inter-TTI interleaving technique that exploits the existing H-ARQ facilities provided by the LTE physical layer, the use of PAPR reduction techniques to increase the resilience of the OFDM waveform to non linear distortion, and the design of the sequences for Random Access, taking into account the requirements deriving from the large round trip times. The outcomes of this analysis show that, with the required proposed enablers, it is possible to reuse the existing terrestrial air interface to transmit over the satellite link.

Hybrid Space-Ground Processing for High-Capacity Multi-Beam Satellite Systems

Signal processing in satellite applications is usually performed either on-ground or on-board, i.e. at the gateway station or in the payload. Within the framework of the European Space Agency (ESA) SatNEx III study, a hybrid approach has been considered by splitting the processing between the satellite and the gateway, aiming to strike a better balance between performance and payload complexity. The design of a high-capacity multi-beam system has been carried out, to assess the potential applicability of a hybrid space-ground processing architecture (Digisat) for satellite broadband systems; this is achieved via hybrid space-ground beamforming, MIMO and MIMO-MUD, Precoding, as well as Digital Feeder link techniques.

1945–2010: 65 Years of Satellite History From Early Visions to Latest Missions

This paper takes a broad view on the history and the present status of satellite communications and broadcasting. The necessary starting point of this overview is the visionary papers produced by Sir Arthur C. Clarke and John Pierce. This was the real dawn of the satellite communication era. This paper attempts to explain the “fil rouge” of the evolution of satellite technologies across six decades, analyzing successes and failures of past satellite missions, and concluding with a picture of future satellite communications.

Coarse beamforming techniques for multi-beam satellite networks

Coarse beamforming is a space processing scheme which allows for efficient use of the available spectral resources on the feeder link of a multi-beam broadband satellite system. In this framework, spectral occupancy of the multiplexed antenna signals that must be exchanged between the satellite and the gateway is a critical issue, up to the point that a costly multiple gateway infrastructure could be required to restrain bandwidth usage. Alternatively, a hybrid on board/on ground processing architecture is desirable, where the effect of space processing allows to project feed signals on a subspace, thus reducing the required feeder link bandwidth. This foresees a fixed processing scheme on board the satellite, which we refer to as Coarse Beamforming, yielding an overall system which relies on reasonable payload complexity, together with on ground processing flexibility. We explore two Coarse Beamforming techniques for the return link of a multi beam satellite system, and we evaluate the effect of compression in terms of reconstructed signal degradation. We show how, without significant distortion, bandwidth occupancy can be considerably reduced.

Performance analysis of a mesh satellite system based on linear and continuous phase modulations

This paper addresses detailed waveform trade-offs for mesh satellite networks. The waveform analysis is carried out considering spectral efficiency, resilience against non linear distortion, channel impairments and interference for both linear and continuous phase modulation schemes defined in the DVB-RCS2 standard.

A Mesh Network over a Semi-Transparent Satellite

In the satellite communications component of the future Internet, peer-to-peer mesh connectivity of satellite terminals is an impellent necessity. In particular, delay sensitive applications such as real-time multimedia, collaborative conferencing and cellular backhauling are appealing use-cases for adopting mesh network topologies. Moreover, the use of a single satellite hop for directly connecting remote terminals (as opposed to a double-hop connection required in star topologies) reduces the satellite traffic load and leads to savings in operational costs of the satellite network. In this paper, we propose a multi-beam satellite mesh network based on a semi-transparent or fully regenerative satellite with different on board switching capabilities. In particular, four network solutions have been assessed in terms of flexibility, complexity and capacity, trading-off between network performance and implementation cost.

On the Optimization of Signal Constellations for Satellite Channels

A gradient method is used to obtain the signal constellation that yields to the minimum error probability over a channel affected by non-linear amplification and additive noise. The results show the dominance of phase shift keying when the amplifier is driven near saturation, and the better performance given by amplitude-phase shift keying if the amplifier is operated in its linear region.

Energy efficient CPM waveforms for satellite mesh networks

This papers addresses the design of new energy-efficient Continuous Phase Modulation (CPM) waveforms suitable for being adopted in satellite mesh networks that are characterized by the absence of the Hub, and by small antennas and power amplifiers with moderate to low output saturated power at the user terminal. In particular, a CPM modulation format concatenated with a proper convolutional code for low spectral efficiency values has been selected to implement an efficient waveform for power-limited scenarios. Performance results show the gain obtained with respect to the DVB-RCS2 CPM waveforms at higher spectral efficiency also when transmission techniques, such as Burst Repetition, are considered, and confirm the suitability of the new designed CPM waveforms for satellite hub-less scenarios.

Multi-user interference mitigation techniques for broadband multi-beam satellite systems

This paper presents a comprehensive evaluation of multi-user interference mitigation techniques for a broadband multi-beam satellite system.

Increasing the feeder link efficiency in broadband satellite systems

In this paper we investigate on signal processing techniques to reduce the bandwidth of the feeder link of a high throughput satellite communication system. On the one hand, conventional transparent satellites are severely constrained by the available bandwidth for the feeder link, while, on the other hand, regenerative satellites require a very large on-board computational effort. An interesting alternative approach is to perform aboard the satellite a digital transparent processing to reduce the redundancy of the signals before transmitting them on the feeder link, hence improving the spectral efficiency of the feeder link with respect to a transparent satellite, while reducing at the same time the associated computational effort with respect to a regenerative satellite. Our results show that the signal occupancy on the feeder link can be effectively reduced, and this positively impacts the number of beams served by a given ground station, hence on the number of required ground stations for a multi-beam system with a large number of beams.