On the Capacity Degradation in Broadband MIMO Satellite Downlinks with Atmospheric Impairments

Abstract—We investigate the impact of atmospheric impairments on the theoretical bandwidth efficiency of Multiple-Input Multiple-Output (MIMO) geostationary satellite links which are shaped to optimize the channel bandwidth efficiency. We analyze the impairments caused by precipitation, since this is the most severe atmospheric effect causing capacity degradations. By theory, the MIMO channel capacity is strongly affected by signal attenuation as well as signal phase shifts that might reduce the number and strength of spatial subchannels (eigenmodes). We will show, however, that the characteristics of the phase disturbances prevent a loss of capacity. Regarding the additional attenuation, which the signals may encounter passing through the troposphere, we will quantify outage values for several levels of link capacity degradation. Although a loss of capacity cannot be avoided in total, it still turns out that MIMO systems outperform conventional Single-Input Single-Output (SISO) designs in terms of reliability. Even in the presence of atmospheric perturbations, MIMO systems still provide enormous capacity gains and vast reliability improvements. Thus, the MIMO satellite systems presented are perfectly suited to establish the backbone network of future broadband wireless standards (e.g. DVB-SH), supporting high data rates for a variety of worldwide services. I

Uniform Circular Arrays: the Key to Optimum Channel Capacity in Mobile MIMO Satellite Links

Abstract—In this paper, we investigate the benefits of uniform circular arrays (UCAs) as an alternative antenna deployment to uniform linear arrays (ULA), which are commonly applied for multiple-input multiple-output (MIMO) systems. We consider a MIMO satellite link with focus on the Line-of-Sight (LOS) signal component of the MIMO channel between two geostationary satellites and a mobile earth terminal equipped with several antennae. The MIMO LOS channel is optimized with respect to the maximum achievable spectral efficiency. The aim of our approach is to keep this optimum spectral efficiency nearly constantly even if the terminal on earth is moving. We provide an analytical derivation for the optimum UCA arrangement and prove our results by numerical simulations. Especially for mobile applications, the UCA antenna arrangement seems to be a reasonable candidate in order to guarantee high capacity performance durably. To this end, we present a very simple triangle shaped antenna arrangement which is compact enough to allow vehicle roof top installations for S-band applications. I

Data-aided single-carrier coherent receivers

Data-aided algorithms for coherent optic receivers are discussed as an extension of existing non-data aided methods. The concept presents a scalable approach with low implementation complexity and limited overhead for higher-order modulation formats

Optical performance monitoring from FIR filter coefficients in coherent receivers

Abstract: We present a robust and precise optical performance monitoring technique from FIR filter coefficients in coherent receivers with digital equalization. Residual chromatic dispersion, DGD and OSNR are simultaneously estimated from measured 111 Gbit/s data

MIMO System Implementation with Displaced Ground Antennas for Broadband Military SATCOM

is applied to military satellite communication (SATCOM) systems. Superior system performance with respect to channel capacity and data rate is proven utilizing an exemplary communication setup with two antennas at both the ground stations and the geostationary satellite. Contrary to widespread discussed polarization multiplexing SATCOM systems, the approach is suited to fully exploit the multiplexing gain in the spatial domain. This goes along with a linear increase of the channel capacity and the throughput in net data rate depending upon the number of antennas used. Hence, the data rate is almost doubled for the exemplary setup in this paper without the need of higher transmit power or channel bandwidth. Moreover, the system offers improved link availability through antenna diversity. Our approach is based on two ideas: Depending upon the satellite orbit position, distinctly displaced ground antennas grant access to a MIMO channel with maximum spatial multiplexing gain. Nearly optimal data rates are then achieved through maximum likelihood equalization with a low-effort single carrier frequency domain equalizer and a zero-forcing filter. A summary on the robustness of the architecture in respect of capacity degrading influences completes the paper

Capacity Optimization and Modelling of frequency selective WLAN indoor MIMO Channels based on measured data

Motivated by channel measurements in different indoor locations we will show that the WLAN indoor MIMO channel is characterized by few dominant transmission paths mainly corresponding to the LOS path and some strong reflections. In the contrary to the common statistical flat Rayleigh fading channel model we will explain that the WLAN channel is widely deterministic and frequency selective. Furthermore we calculate the channel capacity from the measured data and we show its dependence on the geometrical arrangement of the transmit and receive antennas and the characteristics of the location. Here strong variations are observed and therefore we present some promising approaches that could be valid to reduce these capacity variations and enhance the overall capacity