A highly efficient receiver for satellite‐based automatic identification system signal detection

An innovative receiver architecture for the satellite‐based automatic identification system has been recently proposed. In this paper, we describe a few modifications that can be introduced on the algorithms for synchronization and detection, which provide an impressive performance improvement. The receiver architecture has been designed for an on‐board implementation, and a prototype has been implemented by the University of Parma and CGS S.p.A. Compagnia Generale per lo Spazio under the European Space Agency project FENICE (Flexible innovative AIS receiver prototype). A few modifications are also here described that could allow a further performance improvement in case of processing moved to ground‐based stations, based on a priori information there available. Copyright © 2014 John Wiley & Sons, Ltd.     

Evolution of Space Traveling-Wave Tube Amplifier Requirements and Specifications for Modern Communication Satellites

Complex nonconstant envelope high-order digital modulation schemes used in modern communication satellites bring new requirements for the linearity and power efficiency of the on-board traveling-wave tubes (TWTs). As a result, a reassessment of typical TWT specifications is required. A digital system-level figure-of-merit, the total degradation, is proposed. It accounts for the characteristics of any coded signaling scheme, as well as for the performance of the overall communications link, including cochannel and adjacent channel interference. This figure-of-merit allows for reoptimizing the operating point of currently used TWTs, comparing the end-to-end performance of different tubes, and revising the standard TWT linearity-versus-efficiency requirements based on carrier-to-third-order-intermodulation (IM) ratio (C/IM3), noise power ratio, and carrier-to-noise-plus-IM ratio [C/(N + I)].     

MHOMS: high-speed ACM modem for satellite applications

This article presents the novel FPGA-based 1 Gb/s near-Shannon-limit ACM modem developed within the MHOMS program with particular focus on the advanced modem algorithm solutions devised. A number of powerful FEC schemes have been analyzed as possible candidates for the MHOMS modem, and the final selection is justified in terms of the best tradeoff between complexity and performance. State-of-the-art modulation and demodulation algorithms are also presented, including nonlinearity dynamic precompensation techniques and innovative synchronization strategies required by the selected powerful modulation and coding schemes. Overall modem performances are also shown for a variety of spectral efficiencies.     

Symbol and superbaud timing recovery in multi-h continuous-phasemodulation

This paper is concerned with the estimation of two synchronization parameters that play a key role in multi-h continuous-phase modulation receivers-the ordinary symbol timing phase and the so-called superbaud timing phase. The recovery of symbol and superbaud timing is implemented by means of feedforward nondata-aided algorithms. The novelty of the proposed method is that it can be applied to any modulation format, either full or partial response, with binary or multilevel symbols and with arbitrary modulation indices     

Advanced receiver design for satellite‐based automatic identification system signal detection

This paper describes an innovative receiver architecture for the satellite‐based automatic identification system. The receiver performance has been fully validated in the presence of the typical satellite channel characteristics. In particular, it is shown that the devised receiver provides an excellent performance against the noise, as well as a large resilience against message collisions, Doppler shift, and delay spread. Copyright © 2012 John Wiley & Sons, Ltd.     

Coarse recovery of carrier frequency and symbol timing in multibeam satellite channels

A multibeam concept under full frequency reuse is a major prerequisite for high throughput satellite systems. The resulting interference problems might be tackled by appropriately designed precoding or multiuser detection schemes. However, before such powerful techniques are applicable, the most important transmission parameters have to be recovered successfully. In the context of this paper, a feedback structure for joint control of carrier frequency and symbol timing is investigated for a multibeam scenario, which has been developed in some previous work by the authors for a single user link. It is to be noticed that we describe a recovery method for a multibeam satellite network with suitably selected interference mitigation techniques; as a consequence, all cochannels are assumed to be aligned in frequency and time to the reference beam; other signal models are out of scope and not addressed in this contribution.     

Adaptive Coding and Modulation for the DVB-S2 Standard Interactive Applications: Capacity Assessment and Key System Issues

Point-to-point multibeam satellite systems based on the DVB-S standard are currently designed for link closure in the worst-case propagation and location conditions. The DVB-S standard, conceived for broadcasting applications, considers a fixed coding rate and modulation format that are selected according to the assumed coverage and availability requirements. This approach implies the occurrence of high margins in the majority of the cases, when interference and propagation conditions allow for higher signal-to-noise-plus-interference ratio. The adaptive coding and modulation (ACM) introduction in the new DVB-S2 standard for the interactive service profile opens up a number of appealing opportunities for the design and development of satellite broadband networks. In this article we show how the ACM introduction in the satellite downlink enables greatly enhanced system performance but also has a profound impact on the way the system and some of the key system components are designed.     

Cramer‐Rao lower bound and parameter estimation for multibeam satellite links

Data throughput and availability of multibeam satellite links are limited by interference problems, in particular when the design is determined by an aggressive reuse of frequency bands. Usually, this is mitigated by appropriately selected techniques like precoding or multi‐user detection. Before such methods are applicable, however, the most important transmission parameters have to be recovered successfully even under very challenging conditions caused by (full) frequency reuse. The detailed analysis of the log‐likelihood function characterizing the multibeam scenario shows that a beamwise decoupling of the estimation task is possible, if the following three conditions are met: (i) alignment of all frequency offsets; (ii) symbol synchronicity; (iii) orthogonal synchronization sequences. Based on these assumptions, it turns out that the modified Cramer‐Rao lower bound (MCRLB) for carrier frequency and phase, symbol timing and signal amplitude is the same, no matter whether we are dealing with a single or a multiple beam situation. Furthermore, because a maximum likelihood framework for parameter estimation is not available in closed form, we introduce a sub‐optimal concept of low‐complex algorithms. Finally, it is verified by simulation results that the jitter variance of each recovery scheme is close to the related MCRLB, when the decoupling conditions are satisfied. Copyright © 2016 John Wiley & Sons, Ltd.     

Block channel equalization in the presence of a cochannelinterferent signal

Novel algorithms for block equalization of M-ary phase shift keying (PSK) signals transmitted over multipath fading channels in the presence of an interferent cochannel signal are introduced and analyzed. The algorithms exploit the intrinsic statistical properties of cochannel interference (CCI) in order to mitigate its effects. Both linear and decision feedback equalizers (DFEs) are derived under the assumption that the overall channel impulse responses of both the useful and the inteferent signal are known. Simulation results show that: (a) whereas zero-forcing block equalizers yield a large noise enhancement effect, a minimum mean-square block DFE (MMSE-BDFE) can efficiently compensate for the distortion in the useful channel and reduce the effect of CCI at the same time, and (b) the MMSE-BDFEs outperform conventional DFEs, at least in the idealized conditions of our analysis     

Satellite‐based vessel Automatic Identification System: A feasibility and performance analysis

The Automatic Identification System (AIS) is a VHF communication system that provides identification/location information to vessels and shore stations by exchanging data such as position, identification, course, speed, etc. Recently, the interest in detecting and tracking ships at distances from coastlines larger than what can be accomplished by normal terrestrial VHF communications has grown, driven by requirements of long‐range applications such as better handling of hazardous cargo, improved security and countering illegal operations. This paper presents an extension of AIS to a long‐range positioning reporting through a constellation of LEO satellites. It outlines technical challenges like the high rate of message collisions from ships in the field of view of a satellite. Technical solutions are proposed at system and sub‐system level to address these challenges. A computer‐based system simulator is used to assess the system performance and carry out a high‐level system sizing. Results show that a relatively small constellation of LEO satellites can guarantee good ship position detection probability as well as a reporting time interval of a few hours. System performance aspects to be addressed in future work are the possible impact of terrestrial mobile communications interference as well as variations of the estimated traffic data. Copyright © 2009 John Wiley & Sons, Ltd.