Browsing by Author "Wu, J."

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    High-rate distributed space-time-frequency coding for wireless cooperative networks
    (IEEE, 2011-02) Wu, J.; Hu, H.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
    In this paper, we propose high-rate distributed space-time-frequency codes (DSTFCs) to exploit maximum achievable diversity gains over frequency-selective fading channels. The proposed designs achieve full-rate for any number of cooperative nodes, and allow channel variations over multiple OFDM blocks within one DSTFC codeword. We analyze diversity gains of DSTFCs through both conditional and average pairwise error probability (PEP), and we proposes better design criteria based on one-side channel conditional PEP. We show that the difference between the frequency-selective channel orders of source-to-relay and relay-to-destination links may provide extra diversity advantages, thus additional performance gains. Through Monte-Carlo simulations, we demonstrate that proposed high-rate DSTFCs provide notable diversity advantages over existing designs.
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    ArticlePublicationOpen Access
    Multiple-relay selection in amplify-and-forward cooperative wireless networks with multiple source nodes
    (Springer Science+Business Media, 2012-08) Wu, J.; Zhang, Y. D.; Amin, M. G.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
    In this article, we propose multiple-relay selection schemes for multiple source nodes in amplify-and-forward wireless relay networks based on the sum capacity maximization criterion. Both optimal and sub-optimal relay selection criteria are discussed, considering that sub-optimal approaches demonstrate advantages in reduced computational complexity. Using semi-definite programming convex optimization, we present computationally efficient algorithms for multiple-source multiple-relay selection (MSMRS) with both fixed number and varied number of relays. Finally, numerical results are provided to illustrate the comparisons between different relay selection criteria. It isdemonstrated that optimal varied number MSMRS outperforms optimal fixed number MSMRS under the same power constraints.
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    ReviewPublicationOpen Access
    Sustainability challenges for the social-environmental systems across the Asian Drylands Belt
    (IOP Publishing, 2022-02) Chen, J.; John, R.; Yuan, J.; Mack, E. A.; Groisman, P.; Allington, G.; Wu, J.; Fan, P.; De Beurs, K. M.; Karnieli, A.; Gutman, G.; Kappas, M.; Dong, G.; Zhao, F.; Ouyang, Z.; Pearson, A. L.; Güngör, Beyza Şat; Graham, N. A.; Shao, C.; Graham, A. K.; Henebry, G. M.; Xue, Z.; Amartuvshin, A.; Qu, L.; Park, H.; Xin, X.; Chen, J.; Tian, L.; Knight, C.; Kussainova, M.; Li, F.; Fürst, C.; Qi, J.; Interior Architecture and Environmental Design; ŞAT, Beyza
    This paper synthesizes the contemporary challenges for the sustainability of the social-environmental system (SES) across a geographically, environmentally, and geopolitically diverse region - the Asian Drylands Belt (ADB). This region includes 18 political entities, covering 10.3% of global land area and 30% of total global drylands. At the present time, the ADB is confronted with a unique set of environmental and socioeconomic changes including water shortage-related environmental challenges and dramatic institutional changes since the collapse of the Union of Soviet Socialist Republics. The SES of the ADB is assessed using a conceptual framework rooted in the three pillars of sustainability science: social, economic, and ecological systems. The complex dynamics are explored with biophysical, socioeconomic, institutional, and local context-dependent mechanisms with a focus on institutions and land use and land cover change (LULCC) as important drivers of SES dynamics. This paper also discusses the following five pressing, practical challenges for the sustainability of the ADB SES: (a) reduced water quantity and quality under warming, drying, and escalating extreme events, (b) continued, if not intensifying, geopolitical conflicts, (c) volatile, uncertain, and shifting socioeconomic structures, (d) globalization and cross-country influences, and (e) intensification and shifts in LULCC. To meet the varied challenges across the region, place-based, context-dependent transdisciplinary approaches are needed to focus on the human-environment interactions within and between regional landscapes with explicit consideration of specific forcings and regulatory mechanisms. Future work focused on this region should also assess the role of the following mechanisms that may moderate SES dynamics: socioeconomic regulating mechanisms, biophysical regulating mechanisms, regional and national institutional regulating mechanisms, and localized institutional regulating mechanisms.