Harald Schlemmer

Code-aware joint estimation of carrier phase and SNR for linear modulation schemes

Depending on the length of the training sequence, data-aided parameter estimation requires some extra bandwidth. On the other hand, with non-data-aided solutions the payload symbols can be exploited as well, although the performance deviates significantly from the Cramer-Rao lower bound (CRLB) in the low signal-to-noise ratio (SNR) regime. In order to bridge this gap, recent activities concentrated more and more on code-aware (CA) algorithms so as to use the potential of error correction schemes, which usually form part of modern communication systems. In this context, methods for both carrier phase and SNR estimation have been published in the open literature. In the current paper, we extend this work by developing a CA algorithm for joint estimation of carrier phase and SNR; for comparison purposes, the CRLB of this joint approach is derived as the theoretical performance limit.

Satellite-friendly protocols and standards

Abstract Due to the exponential growth of the Internet, the protocol suite of the Internet has become dominant. In the past, satellite communications systems used proprietary protocols. More recently, satellite multimedia architectures have been based on ATM as well as MPEG transport and multiplexing mechanisms. When the traffic is however mostly IP, then the transmission overhead will be significant in both cases. Therefore native IP satellite systems are preferable. In this paper a meshed satellite communications system is presented which is optimised for IP. An important feature is the support of quality of service. Typical applications are fast Internet access and multimedia services. Due to its flexible architecture it can be easily adapted for different standards.

The Alphasat Aldo Paraboni experiment: Fade mitigation techniques in Q/V-band satellite channels, first results

The Alphasat Aldo Paraboni Payload incorporates two Q/V-band satellite transponders, which covers three spot beams over Europe placed towards Italy and towards Graz/Austria. JOANNEUM RESEARCH developed and installed the ground station in Graz and operates communication experiments since beginning of 2014. The goal is to optimize the usage of the Q/V-band channel especially with respect to its high rain fades. In the first period of operation, particularly adaptive coding and modulation has been used as fade mitigation technique. In this paper, we present the architecture of the ground station, the setup and configuration of the experiments, as well as the results from the first nine months of operation. This includes a first estimate of the trade-off between the achievable spectral efficiency vs. the residual frame error rate with respect to the properties of the corresponding Q/V-band satellite link.

The code-aided FEPE algorithm for joint frequency and phase estimation at Low SNR

Estimation of carrier parameters is of paramount importance in digital communications so as to satisfy the requirements in terms of availability and throughput. This is particularly challenging for systems operated in burst mode, where carrier frequency and phase estimates must be computed for each packet or frame. In this context, the reliability of frequency estimates might be a major problem, in case they are provided under low SNR conditions. Enlarging the observation length is basically possible, but this has to be paid by an increase of complexity and redundancy. In order to avoid this dilemma, an algorithm for frequency estimation through phase estimation (FEPE) has been suggested in the technical literature, which is both simple and powerful. Motivated by this approach, we propose that the operation of the FEPE module is closely linked to that of a duo-binary turbo decoder, establishing this way the code-aided joint recovery of carrier and data. Appropriately selected simulation results confirm the utility of the introduced concept.

Joint synchronization of symbol timing and carrier frequency using the extended zero-crossing property

In a recently published paper, a novel approach for blind feedback synchronization of the symbol timing has been proposed. In order to avoid any jitter floor irrespective of the selected modulation scheme, a filter with very particular properties has been developed and placed in parallel to the receiver matched filter. Nevertheless, the jitter performance of this method degrades in case the carrier frequency offset does not vanish. Therefore, joint synchronization of symbol timing and carrier frequency will be studied in the current paper, based on the dual-filter framework developed in some previous works. To this end, we introduce a very simple frequency error detector, which is analyzed in terms of open-loop characteristic (S-curve) and jitter variance, forming this way the ground for joint recovery.

An efficient receiver architecture for burst reception at very low SNR

In interactive satellite communication systems, adaptive coding and modulation is a suitable countermeasure to mitigate the high fade dynamics of frequency ranges like the Ka-band. Consequently, receivers that support operation at low and very low SNR are required. In this paper, we present such a receiver structure dedicated for burst reception in a MF-TDMA system, as it is typically adopted in the return link of satellite systems.