| Summary: | 碩士 === 國立交通大學 === 電機資訊國際學程 === 105 === The rapid traffic growth of Long Term evolution (LTE) cellular network is expected to result in the shortage of licensed band. To satisfy the tremendous traffic demand, more spectrum and widely spreading LTE are required. A proposed concept of LTE in unlicensed band (LTE-U) is that enabling LTE to operate in unlicensed band in order to offload data traffic from licensed band to unlicensed band. A fair coexistence mechanism with other networks, like Wi-Fi, or other LTE-Unlicensed (LTE-U) is essential.
In this thesis, we propose two coexistence mechanisms that could be employed to ensure a fair channel access Carrier Sense Adaptive Transmission(CSAT) and Listen-Before-Talk (LBT). First, we consider coexistence mechanism fundamentals, and then downlink system performance of two coexistence mechanisms is analyzed with different simulation scenarios. Through comparing downlink performance of different scenarios driven by existing coexistence mechanisms, we introduce the most trustworthy coexistence mechanism. We conclude that LTE-U interference significantly affects Wi-Fi operation. On the other hand, Licensed Assisted Access (LAA) can coexist with Wi-Fi without affecting Wi-Fi network. In other words, Licensed Assisted Access (LAA) is better neighbor to Wi-Fi than Wi-Fi itself. These results were achieved through using NS-3 simulator which was essential to demonstrate the excellent performance of the coexistence mechanism and scenario.
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