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My research has been focusing on formulating and solving the routing and resource allocation problems in optical core networks considering various technological and architectural options to achieve greater operational efficiency. Among interesting things in my research works is the "power" to mix components and/or (sub-) systems of diverse technologies to create new modes of operation and/or network architectures that can generate network-wide impacts.
The highlight of my work is a proposal for considering photonic network coding as a new dimension for multiplexing optical signals, in addition to traditional physical dimensions such as time, wavelength, polarization and space. This original approach has laid the foundation for the birth of two new research problems, that is, routing wavelength and network coding assignment (RWNCA) for optical core networks based on WDM technologies and routing, spectrum and network coding assignment (RSNCA) for optical core networks based on elastic transmission technologies. RWNCA and RSNCA are already "a few year old" and ... "growing" elegantly !
For many years, the traditional route of upgrading optical core network capacity has been largely based on exploiting multiple physical multiplexing dimensions such as wavelength-division, time-division, polarization-division multiplexing and recently space-division and orbital angular momentum . It turns out that on one hand, almost all physical dimensions have been used and on the other hand, the economic of scale for doing so has been hard to justify. Inspired by the new paradigm enabled by network coding and simultaneously, the tremendous progresses in photonic signal processing technologies, we envision photonic network coding as a new dimension for boosting the entire capacity of optical core networks. In optimizing the capacity gain offered by network coding usage, we have proposed optimal network design frameworks for optical core networks based on both fixed WDM technologies and the elastic ones.
Routing, Wavelength and Network Coding Assignment [1]
Routing, Spectrum and Network Coding Assignment [2]
We leverage the insight from the characteristic of traffic traveling in fiber links to re-design the protection services in elastic optical networks for greater spectrum efficiency. Inspired by the observation that the today premium network traffic traveling in fiber links accounts for roughly 25% of total traffic and the best-effort traffic constitutes the remaining, we propose a new design framework for elastic optical networks with dedicated path protection tailoring to the actual traffic profile rather than enforcing the same protection service for both traffic types as with conventional approaches. Our approach marks a departure from the conventional protection design - shifting from one-size-fits-all full protection to one-size-for-each partial protection depending on the quality-of-service agreement.
[1] Dao Thanh Hai, "On the spectrum-efficiency of QoS-aware protection in elastic optical networks," Optik, Volume 202, 2020 [2] D. T. Hai et al., "QoS-aware protection in elastic optical networks with distance-adaptive and reconfigurable modulation formats", Optical Fiber Technology, 2020
Algorithmic Aspects of Optical Networks Design and Planning
Algorithmic Aspects of Optical Networks Design and Planning
Nature-inspired Algorithms (e.g., GA, PSO, SA) for Routing and Wavelength/Spectrum Assignment
Decomposition Techniques (e.g., column generation) for Solving Large-scale Routing Routing and Wavelength/Spectrum Assignment
Multi-objective Optimization (Pareto front) for Network Design and Planning
Data-driven and/or AI techniques for Routing and Resource Allocation Problems
[1] D. M. Nguyen, L. A. Ngoc, P. T. V. Huong, N. H. Son and D. T. Hai, "An Efficient Column Generation Approach for Solving the Routing and Spectrum Assignment Problem in Elastic Optical Networks," 2019 6th NAFOSTED Conference on Information and Computer Science (NICS), Hanoi, Vietnam, 2019, pp. 130-135, doi: 10.1109/NICS48868.2019.9023831 [2] Hai, Dao Thanh; Morvan, Michel; Gravey, Philippe: 'Combining heuristic and exact approaches for solving the routing and spectrum assignment problem', IET Optoelectronics, 2018, 12, (2), p. 65-72, DOI: 10.1049/iet-opt.2017.0013[3] D. Hai, M. Morvan, and P. Gravey, "On the Routing and Spectrum Assignment with Multiple Objectives," in Advanced Photonics for Communications, OSA Technical Digest (online) (Optical Society of America, 2014), paper JT3A.12.[4] D. T. Hai, "Multi-objective genetic algorithm for solving routing and spectrum assignment problem," 2017 Seventh International Conference on Information Science and Technology (ICIST), Da Nang, 2017, pp. 177-180, doi: 10.1109/ICIST.2017.7926753
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