# Performance Modeling and Analysis of LTE/Wi-Fi Coexistence
## 2 Related Work
In [11], cross-technology communication between LTE and Wi-Fi is activated by a new technique called LtFi based on two steps. The first step is to use a side channel among both technologies to generate a bi-directional connection and the second step is to use the identification information to adjacent Wi-Fi nodes, which is used in a subsequent step to create a bi-directional control channel over the wired backhaul. The complete description of the LtFi system is presented in [11]. The provided simulation results show that even if the network is congested, the transmission rate of the data is enhanced. Other research [12] focuses on the LTE and WiMAX performance, by considering various antenna diversity for frequency division and time division multiplexing concerning the maximum throughput of the physical layer. In this regard, the authors considered similar configurations for both technologies to compare their performance. It was found that LTE produces a better performance than WiMAX in all circumstances. In [13], the authors considered that studying the coexistence principle in the unlicensed spectrum between LTE and other technologies, such as Wi-Fi, could be a very interesting topic for researchers. A multi-objective optimization framework to study LTE and Wi-Fi performance in a separate matter and to balance the performance of both technologies concerning the unlicensed spectrum is proposed in [14]. The genetic algorithm is used to guarantee the optimization of the throughput for both technologies, as well as the Wi-Fi average packet delay. Multiple deployment scenarios of the coexistence on 5 GHz between Wi-Fi and long-term evolution-licensed assisted access are demonstrated in detail through an extensive survey presented by the authors in [15]. Various topics are discussed in the survey, such as the performance comparison between both technologies, the carrier aggregation of LTE while using an unlicensed spectrum, the medium-access control protocol for both technologies, and the co-channel interference principle. Additionally, the authors also considered the most important challenges that occurred while both technologies coexisted. In both [16; 17], it is shown that the coexistence between LTE and Wi-Fi has a constructive effect on network performance. Both papers emphasized the fact that the hotspot range, which limits the active users in the cell, is affected by the end-user power rather than the access point. Consequently, any request forwarded to the access point has a constructive effect on the overall performance of the network. Licensed-assisted access (LAA) is a tremendous endeavor conducted by the 3 GPP project to approve the standardization of the LTE operation in Wi-Fi unlicensed bands. The orthogonal coexistence of LAA with Wi-Fiunlicensed spectrum is examined in [18]; the coexistence is based on a listening-before-talk setup. The main objective was to maximize the QoS of end-users in LAA and, at the same time, guard Wi-Fi users. Given the simulation results and QoS metrics, the effectiveness of the suggested scheme is shown. To optimize the resource allocation of the unlicensed spectrum in LTE systems, the authors in [19] suggested an algorithm called Multi-Armed Bandit (MAB) to estimate the unused white space of the unlicensed spectrum due to the inefficient use of the resources. To show the effectiveness of the work, the authors compared the results with other algorithms in the literature. A sub-carrier nulling scheme is suggested in [20]. This scheme is based on the idea that Wi-Fi nodes apply sub-carrier sensing on LTE nodes that are working at the same frequency with no overlap between them. The provided simulation results show that the proposed scheme increases the coexistence performance and provides fairness of more than 90%. A time-sharing power resource virtualization technique is suggested in [21]. The authors assumed that utilizing the unlicensed channels used by Wi-Fi networks in LTE networks becomes a new challenge in the research field.