# Performance Modeling and Analysis of LTE/Wi-Fi Coexistence
###### Abstract  
In wireless communications, the fundamental challenge facing mobile operators nowadays is the scarcity of the spectrum and the license fees. Because of the increased traffic, critical performance analysis becomes important to overcome such issues. To tackle these issues and improve the network performance and capacity, a coexistence model of LTE and Wi-Fi with two virtual zones is suggested. The inner zone is the secondary zone, which represents Wi-Fi with an unlicensed spectrum to serve the best effort user data and the outer zone is the primary zone, which represents LTE with licensed spectrum to serve all data connections. The numerical solution of the model is presented using MOSEL-2 simulation and the mathematical solution is derived to validate the model. A threshold minimum bit rate established the user admission. Based on a priority level of the service, most of the traffic is served by the primary LTE zone, however, low priority traffic is moved from the primary LTE zone to the secondary Wi-Fi zone so that the traffic of the entire network is balanced. Although this coexistence sometimes harms LTE performance, the simulation results demonstrate the efficiency of the proposed model in balancing the load over the network, and, consequently, the network performance is improved.  
LTE; Wi-Fi; performance analysis; mathematical solution; coexistence; MOSEL-2 Article Performance Modeling and Analysis of LTE/Wi-Fi Coexistence  
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[PERSON], [PERSON], A.  
utilize the licensed and unlicensed spectrum. This means LTE technology works on the unlicensed band without affecting Wi-Fi performance.  
As per the research conducted in [4; 5], Qualcomm was the first who proposed the direct access of unlicensed bands in the downlink by LTE. Likewise, the analysis and research is focused only on the downlink where LTE directly accesses the unlicensed bands. LTE-Advanced was the leading nominee for 4G and it has been accepted to be the main standard for 4G by the International Telecommunication Union-Telecommunication (ITU-T). In the 3 GPP meeting in March 2011 [3], this decision was confirmed and standardized. LTE is based on the orthogonal frequency division multiple access (OFDMA) modulation technique where data can be transmitted on narrow-band and orthogonal sub-carriers in the frequency domain and, therefore, resources can be shared among different users. Similarly, using Wi-Fi technology, the Access Point can connect different wireless devices, such as tablets, laptops, and smartphones.  
The presented research in this paper extends the work already published at the IEEE conference [6]. In this extended version, the following points are considered:  
* We revise the whole conference paper. Compared to the original paper, only 4%, similarity is obtained.
* We revised the literature review with new references.
* We added information about the MOSEL-2 simulation.
* The mathematical formulation of the model is derived and introduced to validate the simulation results.
* All figures and tables are redrawn, and we revise the explanations to reflect the extension. Moreover, new tables and figures are added.  
The rest of the paper is organized as follows: Section 2 presents the related work; Section 3 presents the modeling, which includes five subsections (LTE/Wi-Fi model integration in Section 3.1, modeling assumptions in Section 3.2, the mathematical formulation of the model in Section 3.3, LTE QoS services and applications in Section 3.4, and the MOSEL-2 solution in Section 3.5); the simulation results and discussions are presented in Section 4; and the conclusions and future work are presented in Section 5.