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Outage probability of multi-hop amplify-and-forward relay systems
Conne, C.,Il-Min Kim IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.3
<P>The outage probability of multi-hop amplify-and-forward relay systems with multiple relays is analyzed. Previously, the outage probability of the two-hop system with multiple relays had been analyzed. In this paper, that work is generalized by finding results for the outage probability of the multi-hop system, of which the previously found results for the two-hop system are special cases. In the two-hop system, signals from the source are forwarded by the relays to the destination only, whereas in the multi-hop system, signals are forwarded to other relays as well as to the destination. We derive a lower bound, which is extremely tight to the actual outage probability for almost all values of outage probability, and asymptotically tight in the high-SNR region, for all important practical cases. We also derive a high-SNR straight-line approximation that is extremely tight to the actual outage probability at very high SNRs, and often at moderately high SNRs as well, for all important practical cases.</P>
SER Analysis and PDF Derivation for Multi-Hop Amplify-and-Forward Relay Systems
Conne, Chris,Ju, MinChul,Yi, Zhihang,Song, Hyoung-Kyu,Kim, Il-Min IEEE 2010 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.58 No.8
<P>An amplify-and-forward, multi-branch, multi-hop relay system with K relays, in which the relays broadcast to other relays as well as the destination, is analyzed. An approximate symbol-error-rate (SER) expression, which is valid for any number of relays and for several modulation schemes, is found for the multi-hop system. Also, the cumulative density function (CDF) and probability density function (PDF) are found for the random variable, Z = XY/(X + Y + c), where X and Y are sums of independent, Erlang random variables, and c is a constant. The moment generating function (MGF) of Z is found for the special case in which c=0. It is shown that these results are generalizations of previously published results for special cases of Z. The MGF of Z is used to develop the approximate SER expression. Results for the analytic SER expression are included and compared with simulation results for various values of K, for various modulation schemes, and for two choices of system parameters (channel variances). Results for the multi-hop system are also compared to results for the two-hop system (in which relays transmit only to the destination).</P>
Bacterial Logic Devices Reveal Unexpected Behavior of Frameshift Suppressor tRNAs
Sawyer, Eric M.,Barta, Cody,Clemente, Romina,Conn, Michel,Davis, Clif,Doyle, Catherine,Gearing, Mary,Ho-Shing, Olivia,Mooney, Alyndria,Morton, Jerrad,Punjabi, Shamita,Schnoor, Ashley,Sun, Siya,Suresh, Korean Society for Bioinformatics 2012 Interdisciplinary Bio Central (IBC) Vol.4 No.3
Introduction: We investigated frameshift suppressor tRNAs previously reported to use five-base anticodon-codon interactions in order to provide a collection of frameshift suppressor tRNAs to the synthetic biology community and to develop modular frameshift suppressor logic devices for use in synthetic biology applications. Results and Discussion: We adapted eleven previously described frameshift suppressor tRNAs to the BioBrick cloning format, and built three genetic logic circuits to detect frameshift suppression. The three circuits employed three different mechanisms: direct frameshift suppression of reporter gene mutations, frameshift suppression leading to positive feedback via quorum sensing, and enzymatic amplification of frameshift suppression signals. In the course of testing frameshift suppressor logic, we uncovered unexpected behavior in the frameshift suppressor tRNAs. The results led us to posit a four-base binding hypothesis for the frameshift suppressor tRNA interactions with mRNA as an alternative to the published five-base binding model. Conclusion and Prospects: The published five-base anticodon/codon rule explained only 17 of the 58 frameshift suppression experiments we conducted. Our deduced four-base binding rule successfully explained 56 out of our 58 frameshift suppression results. In the process of applying biological knowledge about frameshift suppressor tRNAs to the engineering application of frameshift suppressor logic, we discovered new biological knowledge. This knowledge leads to a redesign of the original engineering application and encourages new ones. Our study reinforces the concept that synthetic biology is often a winding path from science to engineering and back again; scientific investigations spark engineering applications, the implementation of which suggests new scientific investigations.