# A Cluster-Based Channel Assignment Technique in IEEE 802.11 Networks
## 5 Conclusions  
Channel assignment in Wi-Fi networks is a complex problem with increasing interest for our society, as there is unceasing growth in the number of customers that make use of Wi-Fi networks, and the available radio resources are very limited. In this paper we propose a heuristic channel assignment technique that is suitable for Wi-Fi networks with a central coordinator. As software-defined networks (SDN) represent a powerful and flexible method for network management, Wi-Fi networks can benefit from this current technology to implement channel assignment techniques. Using SDN, the deployment of centralized channel assignment techniques is easy to implement, as once the specific channel assignment is known, the SDN controller can apply it through its Openflow southbound API [33].  
Figure 8: (a,b) Results for two different settings with high classroom occupancy (36 classrooms under use).  
Figure 9: (a,b) Results for two different settings with total classroom occupancy (48 classrooms under use).  
We modeled the problem as a geometric multilayer graph with two layers: a connectivity layer and an interference layer. The main hypothesis of the paper is that the effect of STAs must be considered in the process of channel assignment. To test that hypothesis, we have proposed a technique called CB-AIIM that is an evolution of AIIM [27], which considers the effect of STAs. In fact, CB-AIIM can be a generalization of AIIM that uses the concept of a cluster (that is composed by an AP and its associated STAs) instead of basing the channel assignment on just the APs. Results show that CB-AIIM clearly improves the performance of AIIM, not only in terms of utility, but also in terms of the variability of the solutions. For that reason, we claim that considering the effect of STAs (the interferences they produce) plays a paramount role in the design of channel assignment techniques. Moreover, we have compared CB-AIIM with other recent proposals appearing in the literature, and we have shown that CB-AIIM outperforms all of them.  
Although the proposal has yielded very satisfactory results, there are still plenty of research opportunities in this area. Our most immediate efforts involve shifting from just considering STAs in a centralized channel assignment to actually involving them in reaching the solutions in a semi-decentralized or decentralized manner. In other words, we plan to develop channel assignment techniques that actively involve STAs in the channel assignment process.  
All authors have made relevant contributions to this work. The proposal of the problem was done by [PERSON] and [PERSON], and it was developed in numerous meetings involving [PERSON] and [PERSON]. The proposal, development and programming of the model were done by [PERSON] and [PERSON]; the programming of the channel assignment techniques was done by [PERSON]. The writing and editing of the paper were done by [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
[PERSON] and [PERSON] are partially funded by project PID2019-104855 RB-100/AEI/10.13039/50110001103 of the Spanish Ministry of Science and Innovation, by project SBPLY/19/180501/000171 of the Junta de Comunidades de Castilla-La Mancha and FEDER and by Project UCeNet (CM/JIN/2019-031) of the Comunidad de Madrid and University of Alcala.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.