Information theoretic analysis of hybrid-ARQ protocols in coherent free-space optical systems

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Automatic retransmission request (ARQ) is a feedback-based data link layer technique which enhances the reliability of communication in fading channels. In this paper, we investigate the performance of hybrid-ARQ (H-ARQ) techniques in coherent free-space optical (FSO) communication systems over atmospheric turbulence-induced fading channels. Under the assumption of a Gamma-Gamma statistical fading channel model, we derive outage probability and throughput expressions for three H-ARQ protocols. We further characterize the outage performance at high values of signal-to-noise-ratio (SNR) through diversity and coding gains. Our results provide insight into the performance mechanisms of different H-ARQ protocols in coherent FSO systems and demonstrate that significant performance gains can be achieved through the deployment of H-ARQ particularly in the strong turbulence regime.European Commission ; TUB

Immunohistochemical Labeling of the Inhibin/Activin βC Subunit in Normal Human Placental Tissue and Chorionic Carcinoma Cell Lines

Inhibins and activins are important regulators of the female reproductive system. A novel inhibin subunit, named βC, has been identified and demonstrated to be expressed in several human tissues. We demonstrate here that inhibin βC is expressed in human placenta. Expression of the inhibin βC subunit was demonstrated at the protein level by means of immunohistochemical evaluation and at the transcriptional level by an inhibin βC-specific RT-PCR analysis. Expression of inhibin βC was detected in the human chorionic carcinoma cell lines JEG and BeWo. Although the precise role of this novel inhibin subunit in human placenta development and homeostasis is unclear, analogies with other inhibin subunits and the strong expression of βC in normal human trophoblast cells and chorionic carcinoma cells suggest that βC may be involved in autocrine/paracrine signaling pathways, angiogenesis, decidualization, and tissue remodeling under normal and malignant conditions. Additionally, JEG and BeWo express βC and, therefore, can be used as a cell culture model for further functional analysis of this subunit in the human placenta. (J Histochem Cytochem 58:751–757, 2010