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Open AccessFeature PaperArticle

Multi-Hop Relay Selection Based on Fade Durations

University of Missouri-Kansas City, Department of Computer Science and Electrical Engineering, 5110 Rockhill Road, Kansas City, MO 64110, USA
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Electronics 2020, 9(1), 92; https://doi.org/10.3390/electronics9010092
Received: 31 October 2019 / Revised: 8 December 2019 / Accepted: 11 December 2019 / Published: 2 January 2020
(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)
In cooperative relaying, the selection of relays could be based on different parameters. The most well-known and frequently used metric is the signal-to-noise ratio (SNR). In this method of relay selection, the rapid fluctuation of the signal (i.e., fading) is not taken into account in the selection criteria. Such rapid signal change may cause significant loss of information, degrade signal quality for voice or video connections, or could make the channel coding fail. An alternative method of relay selection in a cooperative relay network is by considering fading. Such methods include average fade duration (AFD) and fade duration outage probability (FDOP), which are based on time correlation statistics. Both the AFD and the FDOP are computed in reference to a threshold value for signal quality. This work derives new formulas for two hop and three hop relay paths, with three hop paths given a penalty cost. Then optimization algorithms for each type of relay selection method are derived, including total path and link-by-link optimization. Simulation results provide optimal AFD and FDOP paths for various random network topologies. These paths are then compared to paths that would be found if SNR metrics were used instead. It is shown that SNR optimization results in much different performance. For cases of four sources and four relays, SNR based optimization frequently chose different relay paths, as low as only 63% of the same relay paths as FDOP or AFD optimizations. Because fade duration methods more accurately control the fading nature and true quality of the signals, the results here provide significant improvements in relay performance and allow two and three hop relay paths to be implemented effectively. View Full-Text
Keywords: cooperative relay wireless network; decode and forward (DF); average fade duration (AFD); level crossing rate (LCR); fade duration outage probability (FDOP) cooperative relay wireless network; decode and forward (DF); average fade duration (AFD); level crossing rate (LCR); fade duration outage probability (FDOP)
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Assefa Gebremichail, A.; Beard, C.; Paropkari, R.A. Multi-Hop Relay Selection Based on Fade Durations. Electronics 2020, 9, 92.

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