This special issue is devoted to Satellite Communication advances so as to gather the most important contributions in this field from academia and industry. In particular, the importance of this issue is also due to the fact that the last issue appearing on IEEE JSAC about SatCom is dated back to 2004 and therefore many important technology advances have been testified in the meantime, actually revolutionizing the satellite industry. In particular, important innovations have been brought to the design of both ground and space segments, spanning physical layers up to upper layers of the protocol stack.

This special issue is devoted to the satellite communications (SatCom) advances so as to gather the most important contributions in this field from academia and industry. In particular, the importance of this issue is also due to the fact that the last issue appearing on IEEE JSAC about SatCom is dated back to 2004 and therefore many important technology advances have been testified in the meantime, actually revolutionizing the satellite industry. In particular, important innovations have been brought to the design of both ground and space segments, spanning physical layers up to upper layers of the protocol stack.

To face the challenges of the new era of heterogeneous networks, mobile satellite systems need to provide an increased level of flexibility. As a consequence, a more effective use of the available resources and the exploitation of interference mitigation techniques are considered necessary to tackle the issue. The limits of a traditional configuration are even more noticeable in specific areas of high traffic requests i.e., in hot spots. In this paper, focusing on the forward link of a typical mobile interactive satellite system operating in L-band, where a large imbalance in traffic demand between the multiple beams is common, new configurations that aim at improving the performance of the system are studied. The proposed approach, based on a higher frequency reuse factor and the application of precoding techniques, boosts the system in terms of total capacity and provides higher flexibility, without making any change whatsoever to the space segment. A general analytic formulation of the problem and a pragmatic solution are provided for hot spot scenarios. Simulations are carried out to validate the proposed solution.

In this paper we propose the usage of Single Carrier Frequency Division Multiple Access (SC-FDMA) in the Broadband Satellite Return Channel. Notably, SC-FDMA is able to improve the physical layer spectral efficiency with respect to single carrier systems, which has been used so far in the Return Channel Satellite (RCS) standards. However, it requires a strict synchronization and it is also sensitive to phase noise of local radio frequency oscillators. For this reason, we propose an effective pilot tone arrangement within the SC-FDMA frame, and a novel Joint Multi-User (JMU) estimation method for the SC-FDMA. As shown by numerical results, the proposed scheme manages to satisfy strict synchronization requirements and to guarantee a proper demodulation of the received signal.

For ADSL applications, very large constellation sizes are used, which can be as large as 32768QAM. It is a big challenge to design turbo TCM for such a large constellation size while still maintaining low decoding complexity. We propose a new turbo coded QAM scheme with a unique "concatenated Gray mapping" for an ADSL system. This new mapping can not only provide good performance for turbo coded bits but can also efficiently maximize the minimum Euclidean distance of uncoded bits. This new turbo coded QAM scheme not only has as good error correcting performance as the conventional bit-interleaved turbo coded QAM and symbol-interleaved turbo TCM schemes, but also has very low decoding complexity which is only about 17% of the conventional bit-interleaved turbo coded QAM.

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.

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.

Frequency tracking loops are used in digital links to control the carrier frequency of the received signals. A basic component in such loops is the frequency difference detector (FDD). This paper concentrates on a class of FDDs for use with binary continuous-phase modulation (CPM). Their derivation is based on two ideas: the maximum-likelihood principle for parameter estimation and Laurent's (1986) decomposition of a CPM signal into the sum of linearly modulated components. The proposed FDDs are suitable for digital implementation and their operation is independent of clock recovery. Analysis and simulation are employed to investigate tracking operation and acquisition capability of frequency control loops endowed with such FDDs. Numerical examples are provided for modulation schemes of practical interest such as MSK and Gaussian MSK. The loop acquisition range is found to be fairly large, about 0.5-1.0 times the bit rate.>