Graph Theory & Network Optimization Research Laboratory

Graph Theory and Network Optimization (GRANET) laboratory is led by Assoc. Prof. Didem Gözüpek in the Computer Engineering Department of Gebze Technical University, Turkey. We perform research on several aspects of theoretical computer science and discrete mathematics such as structural and algorithmic graph theory and approximation algorithms. We also focus on optimization problems arising from practical applications such as computer networks.

Funding for GRANET mainly comes from both national and international TUBITAK projects. We frequently have openings for postdoctoral researchers and graduate students. In addition to computer engineering, researchers from different background such as mathematics and industrial engineering are also welcome to apply. The available financial package includes salary and conference travel support as well as opportunities for research visits to our collaborators in Europe through our bilateral research projects. Interested candidates should contact Assoc. Prof. Didem Gözüpek via email by sending their CV and a list of academic references.

Sep 30, 2017
Workshop on Graph Theory and Its Applications-VII, co-organized by GRANET director Assoc.Prof.Didem Gözüpek, will take place in Gebze Technical University on November 10-11, 2017. For more information please click here.
Aug 2, 2017
Our paper "Characterizations of minimal dominating sets and the well-dominated property in lexicographic product graphs" has been accepted to Discrete Mathematics and Theoretical Computer Science.
July 25, 2017
Our paper "Parameterized complexity of finding a spanning tree with minimum reload cost diameter" has been accepted to International Symposium on Parameterized and Exact Computation (IPEC), 2017.
 
Gebze Technical University
Department of Computer Engineering
41400, Gebze
Kocaeli, Turkey

+90 262 605 22 17
didem.gozupek (at) gtu.edu.tr
dgozupek (at) gmail.com


      Director
Assoc. Prof. Didem Gözüpek
Research Interests: Algorithmic and structural graph theory, approximation algorithms, optimization problems in communication networks
+90 262 605 22 17
didem.gozupek (at) gtu.edu.tr
Personal website

      Postdoc
Dr. Uğur Odabaşı
Research Interests: Graph theory, combinatorial design theory, optimization problems in communication networks
+90 212 473 70 70
ugur.odabasi (at) istanbul.edu.tr
Personal website

    PhD Student
Hadi Alizadeh
Research Interests: Algorithmic and structural graph theory, approximation algorithms, optimization problems in communication networks
+90 262 605 24 41
halizadeh (at) gtu.edu.tr
Personal website

    PhD Student
Yasemin Büyükçolak
Research Interests: Graph theory and combinatorics
+90 262 605 13 77
y.buyukcolak (at) gtu.edu.tr
Personal website

    MSc Student
Emre Belen
Research Interests: Optimization problems in communication networks
+90 262 605 24 41
ebelen (at) gtu.edu.tr
Personal website

    MSc Student
Mustafa Çamurli
Research Interests: Cognitive radio networks, green networks, optimization problems in communication networks
+90 262 605 24 41
mustafacamurli (at) gmail.com
Personal website

    PhD Student
Sercan Demirci
Research Interests: P2P networks, wireless sensor networks, cognitive radio networks, optimization problems in communication networks
+90 232 311 32 28
sercan.demirci (at) ege.edu.tr
Personal website
Selim Bahadır
Currently: Assistant Professor at Yıldırım Beyazıt University
Mohamed Dahir
(MSc, 2017)
Thesis title: "Energy Efficient Virtual Network Embedding in Federated Software Defined Networks"
Şeyma Batı
(MSc, 2016)
Thesis title: "Joint optimization of cash management and routing for new generation automated teller machine networks" (Currently: Senior software engineer at Yapı ve Kredi Bankası)
Hadi Alizadeh
(MSc, 2015)
Thesis title: "Minimizing signaling cost in green routing for software defined networks"
(Currently: PhD student at Gebze Technical University)
Fatma Ekici
(MSc, 2014)
Thesis title: "Joint overlay routing and relay assignment for green networks"
(Currently: Senior researcher at TUBITAK)
Ongoing projects
2014 - Ongoing
Energy efficiency and fairness for resource management in federated software defined networks, TUBITAK-1001 Project, funded by Scientific and Technological Research Council of Turkey (TUBITAK), Project No: 114E245
Completed projects
2015 - 2017
Reload cost concept in graph theory: A combinatorial analysis, Turkey-France Bilateral Research Project, funded by Scientific and Technological Research Council of Turkey (TUBITAK)-CNRS, Project No: 114E731
2014 - 2017
Resource allocation and routing for green networks, CAREER Project, funded by Scientific and Technological Research Council of Turkey (TUBITAK), Project No: 113E567
2014 - 2016
Energy-fair routing in green multi-domain networks, BAP Project, funded by Scientific Research Projects Office of Gebze Technical University, Project No: 2014 A27
2014 - 2015
A software defined networking approach to resource management in virtual networks, University-Industry Collaboration Project, funded by Argela Technologies
2013 - 2015
Minimum changeover cost graph problems, BAP Project, funded by Scientific Research Projects Office of Gebze Technical University, Project No: 2013 A24
Journals (SCI/SCI-E)

D. Gözüpek, A. Hujdurovic, M. Milanic, "Characterizations of minimal dominating sets and the well-dominated property in lexicographic product graphs", accepted to Discrete Mathematics and Theoretical Computer Science, 2017.

Ş. Batı, D. Gözüpek, "Joint optimization of cash management and routing for new-generation automated teller machine networks", accepted to IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2017.

D. Gözüpek, S. Özkan, C. Paul, I. Sau, M. Shalom, "Parameterized complexity of the MINCCA problem on graphs of bounded decomposability", accepted to Theoretical Computer Science, 2017.

C. Beşiktaş, D. Gözüpek, A. Ulaş, E. Lokman, "Secure virtual network embedding with flexible bandwidth-based revenue maximization", accepted to Computer Networks, 2017.

Y. Büyükçolak, D. Gözüpek, S. Özkan, M. Shalom, "On one extension of Dirac's theorem on Hamiltonicity", accepted to Discrete Applied Mathematics, 2017.

M. F. Tüysüz, Z. K. Ankaralı, D. Gözüpek, "A survey on energy efficiency in software defined networks", accepted to Computer Networks, 2016.

N. Chiarelli, C. Dibek, T. Ekim, D. Gözüpek, S. Miklavic, "On matching extendability of lexicographic products", accepted to RAIRO-Operations Research, 2016.

C. Dibek, T. Ekim, D. Gözüpek, M. Shalom, "Equimatchable graphs are C2k+1-free for k ≥ 4", Discrete Mathematics, vol. 339, no. 12, pp. 2964-2969, 2016.

D. Gözüpek, H. Shachnai, M. Shalom, S. Zaks, "Constructing minimum changeover cost arborescences in bounded treewidth graphs", Theoretical Computer Science, vol. 621, no. 12, pp. 22-36, 2016.

F. Ekici, D. Gözüpek, "Joint overlay routing and relay assignment for green networks", Computer Networks, vol. 79, no. 12, pp. 323-344, 2015.

D. Gözüpek, M. Shalom, F. Alagöz, "A graph-theoretic approach to scheduling in cognitive radio networks", IEEE/ACM Transactions on Networking, vol. 23, no. 1, pp. 317-328, 2015.

D. Gözüpek, M. Shalom, A. Voloshin, S. Zaks, "On the complexity of constructing minimum changeover cost arborescences", Theoretical Computer Science, vol. 540-541, pp. 40-52, 2014.

D. Gözüpek, S. Buhari, F. Alagöz, "A spectrum switching delay-aware scheduling algorithm for centralized cognitive radio networks", IEEE Transactions on Mobile Computing, vol. 12, no. 7, pp. 1270-1280, 2013.

D. Gözüpek, B. Eraslan, F. Alagöz, "Throughput satisfaction-based scheduling for centralized cognitive radio networks", IEEE Transactions on Vehicular Technology, vol. 61, no. 9, pp. 4079-4094, 2012.

B. Eraslan, D. Gözüpek, F. Alagöz, "An auction theory based algorithm for throughput maximizing scheduling in centralized cognitive radio networks", IEEE Communications Letters, vol. 15, no. 7, pp. 734-736, 2011.

D. Gözüpek, F. Alagöz, "Genetic algorithm-based scheduling in cognitive radio networks under interference temperature constraints", Wiley's International Journal of Communication Systems (IJCS), vol. 24, no. 2, pp. 239-257, 2011.

D. Gözüpek, F. Alagöz, "Throughput and delay optimal scheduling in cognitive radio networks under interference temperature constraints", Journal of Communications and Networks (JCN), vol. 11, no. 2, pp. 147-155, 2009.

D. Gözüpek, S. Papavassiliou, N. Ansari, "Enhancing quality of service provisioning in wireless ad hoc networks using service vector paradigm", Wiley Journal on Wireless Communications and Mobile Computing (WCMC), vol. 6, no. 7, pp. 1003-1015, 2006.

International Conferences

J. Baste, D. Gözüpek, C. Paul, I. Sau, M. Shalom, D. M. Thilikos, "Parameterized complexity of finding a spanning tree with minimum reload cost diameter", International Symposium on Parameterized and Exact Computation (IPEC), Vienna, Austria, 2017.

D. Gözüpek, S. Özkan, C. Paul, I. Sau, M. Shalom, "Parameterized complexity of the MINCCA problem on graphs of bounded decomposability", International Workshop on Graph-Theoretic Concepts in Computer Science (WG), Istanbul, Turkey, 2016.

C. Beşiktaş, D. Gözüpek, A. Ulaş, E. Lokman, Ö. Özyurt, K. Ulusoy, "Flexible bandwidth-based virtual network embedding", IEEE Network Operations and Management Symposium (NOMS), Istanbul, Turkey, 2016.

N. T. Altan Akin, D. Gözüpek, "Energy-fair routing in multi-domain green networks", International Conference on Software, Telecommunications and Computer Networks (SoftCOM), Split-Bol (Island of Brac), Croatia, 2015.

H. Alizadeh, D. Gözüpek, S. Buhari, A. Yayimli, "Minimizing signaling cost in green routing for software defined networks", IEEE International Symposium on Computers and Communications (ISCC), Cyprus, 2015.

D. Gözüpek, M. Shalom, "Edge coloring with minimum reload/changeover costs", Algorithmic Graph Theory on the Adriatic Coast (AGTAC), Koper, Slovenia, 2015.

C. Dibek, T. Ekim, D. Gözüpek, M. Shalom, "Equimatchable graphs are C2k+1-free for k ≥ 4", Cologne-Twente Workshop on Graphs and Combinatorial Optimization, Istanbul, Turkey, 2015.

D. Gözüpek, H. Shachnai, M. Shalom, S. Zaks, "Constructing minimum changeover cost arborescences in bounded treewidth graphs", Cologne-Twente Workshop on Graphs and Combinatorial Optimization, Istanbul, Turkey, 2015.

D. Gözüpek, M. Shalom, "Edge coloring with minimum reload/changeover costs", Cologne-Twente Workshop on Graphs and Combinatorial Optimization, Istanbul, Turkey, 2015.

Y. Büyükçolak, D. Gözüpek, S. Özkan, "Extension of Dirac theorem on Hamiltonicity", Cologne-Twente Workshop on Graphs and Combinatorial Optimization, Istanbul, Turkey, 2015.

M. Çamurli, D. Gözüpek, "Channel switching cost-aware resource allocation for multi-hop cognitive radio networks with a single transceiver", International Conference on Ad hoc Networks (ADHOCNETS), Rhodes, Greece, 2014.

M. R. Çelenlioğlu, D. Gözüpek, H. A. Mantar, "A survey on the energy efficiency of vertical handover mechanisms", International Conference on Wireless and Mobile Networks (WiMoN), Istanbul, Turkey, 2013.

D. Gözüpek, M. Shalom, A. Voloshin, S. Zaks, "On the complexity of constructing minimum reload cost path-trees", short paper in International Symposium on Combinatorial Optimization (ISCO), Athens, Greece, 2012.

D. Gözüpek, F. Alagöz, "An interference aware throughput maximizing scheduler for centralized cognitive radio networks", IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), Istanbul, Turkey, 2010.

D. Gözüpek, G. Genç, C. Ersoy, "Channel assignment problem in cellular networks: A reactive tabu search approach", IEEE International Symposium on Computer and Information Sciences (ISCIS), Northern Cyprus, 2009.

D. Gözüpek, F. Alagöz, "Scheduling in cognitive radio networks", Google Anita Borg Meeting, Zürich, Switzerland, 2009.

D. Gözüpek, S. Bayhan, F. Alagöz, "A novel handover protocol to prevent hidden node problem in satellite assisted cognitive radio networks", IEEE International Symposium on Wireless Pervasive Computing (ISWPC), Santorini, Greece, 2008.

D. Gözüpek, A. Sever, "Service concentration node in IMS", Lecture Notes in Computer Science (LNCS), International Conference on Next Generation Teletraffic and Wired/Wireless Advanced Networking (NEW2AN), vol. 5174, pp. 169-176, St.Petersburg, Russia, 2008.

D. Gözüpek, S. Papavassiliou, N. Ansari, J. Yang, "A power efficient qos provisioning architecture for wireless ad hoc networks", IEEE International Conference on Communications (ICC), Istanbul, Turkey, 2006.

D.Gözüpek, S.Papavassiliou, N.Ansari, "A cross-layer architecture for end-to-end qos provisioning in wireless ad hoc networks", International Symposium on Communication Systems, Networks, and Digital Signal Processing (CSNDSP), Patras, Greece, 2006.

Technical Reports

D. Gözüpek, S. Özkan, C. Paul, I. Sau, M. Shalom, "Parameterized complexity of the MINCCA problem on graphs of bounded decomposability", arXiv preprint:1605.00532, 2016.

D. Gözüpek, F. Alagöz, "A fair scheduling model for centralized cognitive radio networks", arXiv preprint:1309.2233, 2013.

D. Gözüpek, M. Shalom, A. Voloshin, S. Zaks, "On the complexity of constructing minimum reload cost path-trees", Technical Report CS-2012-01, Technion, Department of Computer Science, 2012.

Book Chapter

D. Gözüpek, F. Alagöz, "An opportunistic pervasive networking paradigm: Multi-hop cognitive radio networks", Chapter 7 in Pervasive Computing and Networking, John Wiley & Sons, Ltd., UK, 2011.

Local Conferences

D. Gözüpek, G. Genç, "Hücresel ağlarda kanal planlama problemine tabu araması yaklaşımı (A tabu search approach to the channel assignment problem in cellular networks)", Conference on Academic Informatics (Akademik Bilişim), Şanlıurfa, Turkey, 2009.

Sep 30, 2017
Workshop on Graph Theory and Its Applications-VII, co-organized by GRANET director Assoc.Prof.Didem Gözüpek, will take place in Gebze Technical University on November 10-11, 2017. For more information please click here.
Aug 2, 2017
Our paper "Characterizations of minimal dominating sets and the well-dominated property in lexicographic product graphs" has been accepted to Discrete Mathematics and Theoretical Computer Science.
July 25, 2017
Our paper "Parameterized complexity of finding a spanning tree with minimum reload cost diameter" has been accepted to International Symposium on Parameterized and Exact Computation (IPEC), 2017.
July 14, 2017
Our paper "Joint optimization of cash management and routing for new-generation automated teller machine networks" has been accepted to IEEE Transactions on Systems, Man, and Cybernetics: Systems.
June 19, 2017
Our paper "Parameterized complexity of the MINCCA problem on graphs of bounded decomposability" has been accepted to Theoretical Computer Science.
June 16, 2017
GRANET member Mohamed Haji Dahir successfully defended his MS thesis with title "Energy efficient virtual network embedding for federated software defined networks".
May 30, 2017
GRANET member Mohamed Haji Dahir attended the 25th Signal Processing and Communication Application Conference (SIU 2017) in Antalya, Turkey and presented the paper entitled "Energy efficient virtual network embedding in federated software defined networks".
Apr 7, 2017
Our paper "Secure virtual network embedding with flexible bandwidth-based revenue maximization" has been accepted to Computer Networks.
Mar 22, 2017
GRANET member Mohamed Haji Dahir's paper entitled "Energy efficient virtual network embedding in federated software defined networks" has been accepted to IEEE SIU 2017 Conference.
Feb 9, 2017
Emre Belen joined our research group.
Jan 18, 2017
Our paper "On one extension of Dirac's theorem on Hamiltonicity" has been accepted to Discrete Applied Mathematics.
Dec 19, 2016
Our paper "A survey on energy efficiency in software defined networks" has been accepted to Computer Networks.
Dec 12, 2016
Dr. Gülnaz Boruzanlı Ekinci visited GRANET.
Dec 10, 2016
Dr. Selim Bahadır joined our research group.
Nov 18, 2016
GRANET director Dr. Gözüpek and GRANET members Hadi Alizadeh and Dr. Odabaşı gave talks at the Workshop on Graph Theory and Its Applications VI. Click here to see the gallery.
Nov 4, 2016
Workshop on Graph Theory and Its Applications VI co-organized by GRANET director Dr. Gözüpek is going to take place in Istanbul Center for Mathematical Sciences (IMBM) on November 18-19, 2016.
Nov 3, 2016
Our paper entitled "On matching extendability of lexicographic products" has been accepted for publication in RAIRO-Operations Research.
Nov 2, 2016
Our research group website has been established!


Department of Industrial Engineering, Boğaziçi University, Istanbul, Turkey


Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia


CNRS, LIRMM, Universit´e de Montpellier, Montpellier, France


Sharif University of Technology, Tehran, Iran


Technion Israel Institute of Technology, Haifa, Israel
GRANET © 2016