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.
SUMMARYThe recently approved mobile version of the Digital Video Broadcasting Return Channel via Satellite (DVB-RCS1M) foresees the use of direct sequence spectrum spreading (DS-SS) in the forward link. The addition of a spreading mode, on top of the conventional time division signaling structure of the fixed DVB-S2, allows in fact for the efficient extension of DVB-S2 to mobile terminals with small aperture antennas operating in Ku (11-14 GHz) and Ka (20-30 GHz) bands. Spectrum spreading has been introduced to augment the received energy without increasing the transmitted power density, which is limited by regulatory constraints, and to enhance the waveform resilience to co-channel interference. In this paper, we report on the design and assessment of the DS-SS technique that we carried out for its inclusion in the DVB-RCS1M standard. In particular, by comparing the physical layer performance of the spread and nonspread modes in the specific DVB-RCS1M mobile scenarios, we show that the proposed DS-SS technique has no impact on the DVB-RCS1M data detection performance, while satisfying the requirements on interference resilience and received energy augmentation. In order to deal with the acquisition issues raised by the introduction of the DS-SS technique, we then propose and evaluate several synchronization sub-systems able to deal with the specific impairments of the mobile satellite scenarios, that is, large frequency offsets, phase noise, link obstructions, etc. Finally, a possible implementation of the DS-SS technique that fully accommodates the reuse of the specific hardware compatible with conventional DVB-S2 is also reported.
This paper tackles the issue of increasing GNSS receivers reliability by presenting a novel ultra-tight integration scheme identified as Gaussian AUtocorrelation Scaled Sum (GAUSS). This hybridization approach is based on the concept that a completely artificial autocorrelation peak, generated starting from the information provided by the inertial sensors can be fused non-coherently into the received signal autocorrelation function to enhance the receiver robustness in harsh conditions as in the presence of interferers and multipath.
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