Modeling and Analysis of Tightly Coupled LTE–Wi-Fi Networks

Patro, Sumanta and Tamma, Bheemarjuna Reddy (2018) Modeling and Analysis of Tightly Coupled LTE–Wi-Fi Networks. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Next generation wireless networks will bestow pervasive communication services to end-users. Huge proliferation of digital gadgets may lead to immense growth of data traffic. Limited by available spectrum, some operators have chosen the unlicensed band to serve this exponential demand. As a promising alternative, offloading data from cellular network to Wi-Fi network caters to the data demand and facilitates a persistent access to the network by leveraging the heterogeneous connectivity. Stochastic geometry has been used in the literature to develop amenable models to delineate and apprehend the performance of wireless networks. A tractable and flexible model has been proposed for heterogeneous wireless networks consisting of tightly coupled long-term evolution (LTE) Small cell eNodeBs (SeNBs) and wireless fidelity (Wi-Fi) access points (APs). Stochastic geometry has been leveraged to characterize the key performance metrics of LTE–Wi-Fi Aggregation (LWA) system. The positions for SeNBs and APs are modeled as two independent homogeneous Poisson Point Processes (PPPs) in a non co-located LWA scenario. Enabling LWA operation with arbitrary number of Wi-Fi APs in a given region may not ensure maximum rate and coverage. A novel scheme, coined as, InterfereNCe Aware mat´eRN hArd-core poinT procEss (INCARNATE) has been proposed to increase the performance of LWA system by allowing LWA operation with a chosen set of Wi-Fi APs. We derive Signal-to-Interference-plus-Noise Ratio (SINR) distribution of UEs which are associated to SeNB, AP or LWA. INCARNATE is modeled as a modified Mat´ern Hard-Core Point Process (MHCPP). This further helps to find joint coverage probability and average data rate over the network. We then verify the accuracy of the analytical results with empirical outcomes. INCARNATE scheme outperforms the traditional MHCPP scheme by 73% and 17% in terms of data rate and coverage probability, respectively. Similarly, LWA with INCARNATE scheme excels by 51% and 6.23% as compared to regular LWA in terms of data rate and coverage probability, respectively. INCARNATE scheme is further extended to mINCARNATE scheme wherein mobility is introduced in the LWA system. Expected number of handovers, rate of handover, and average data rate have been analytically modeled. Outage probability, handover count, and instantaneous throughput of UEs have been measured using simulation environment. Proposed adaptive function assists to obtain the optimal density of LWA nodes using mINCARNATE scheme. The feasibility of LTE–Wi-Fi radio level integration at IP layer (LWIP) has been revealed using OAI LTE, Cisco AP, USRP B210 Software Defined Radio (SDR), and commercial UE. The developed real-time prototype does not require any modifications to the protocol stack of the UE. We have implemented different link aggregation strategies to study the performance of the LWIP prototype. vi

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